[sqlite] Remove obsolete reference version 3.8.7.4.

third_party/sqlite/sqlite-src-3080704/src/os_unix.c

-/*
-** 2004 May 22
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-******************************************************************************
-**
-** This file contains the VFS implementation for unix-like operating systems
-** include Linux, MacOSX, *BSD, QNX, VxWorks, AIX, HPUX, and others.
-**
-** There are actually several different VFS implementations in this file.
-** The differences are in the way that file locking is done.  The default
-** implementation uses Posix Advisory Locks.  Alternative implementations
-** use flock(), dot-files, various proprietary locking schemas, or simply
-** skip locking all together.
-**
-** This source file is organized into divisions where the logic for various
-** subfunctions is contained within the appropriate division.  PLEASE
-** KEEP THE STRUCTURE OF THIS FILE INTACT.  New code should be placed
-** in the correct division and should be clearly labeled.
-**
-** The layout of divisions is as follows:
-**
-**   *  General-purpose declarations and utility functions.
-**   *  Unique file ID logic used by VxWorks.
-**   *  Various locking primitive implementations (all except proxy locking):
-**      + for Posix Advisory Locks
-**      + for no-op locks
-**      + for dot-file locks
-**      + for flock() locking
-**      + for named semaphore locks (VxWorks only)
-**      + for AFP filesystem locks (MacOSX only)
-**   *  sqlite3_file methods not associated with locking.
-**   *  Definitions of sqlite3_io_methods objects for all locking
-**      methods plus "finder" functions for each locking method.
-**   *  sqlite3_vfs method implementations.
-**   *  Locking primitives for the proxy uber-locking-method. (MacOSX only)
-**   *  Definitions of sqlite3_vfs objects for all locking methods
-**      plus implementations of sqlite3_os_init() and sqlite3_os_end().
-*/
-#include "sqliteInt.h"
-#if SQLITE_OS_UNIX              /* This file is used on unix only */
-
-/*
-** There are various methods for file locking used for concurrency
-** control:
-**
-**   1. POSIX locking (the default),
-**   2. No locking,
-**   3. Dot-file locking,
-**   4. flock() locking,
-**   5. AFP locking (OSX only),
-**   6. Named POSIX semaphores (VXWorks only),
-**   7. proxy locking. (OSX only)
-**
-** Styles 4, 5, and 7 are only available of SQLITE_ENABLE_LOCKING_STYLE
-** is defined to 1.  The SQLITE_ENABLE_LOCKING_STYLE also enables automatic
-** selection of the appropriate locking style based on the filesystem
-** where the database is located.  
-*/
-#if !defined(SQLITE_ENABLE_LOCKING_STYLE)
-#  if defined(__APPLE__)
-#    define SQLITE_ENABLE_LOCKING_STYLE 1
-#  else
-#    define SQLITE_ENABLE_LOCKING_STYLE 0
-#  endif
-#endif
-
-/*
-** Define the OS_VXWORKS pre-processor macro to 1 if building on 
-** vxworks, or 0 otherwise.
-*/
-#ifndef OS_VXWORKS
-#  if defined(__RTP__) || defined(_WRS_KERNEL)
-#    define OS_VXWORKS 1
-#  else
-#    define OS_VXWORKS 0
-#  endif
-#endif
-
-/*
-** standard include files.
-*/
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-#include <unistd.h>
-#include <time.h>
-#include <sys/time.h>
-#include <errno.h>
-#if !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0
-# include <sys/mman.h>
-#endif
-
-#if SQLITE_ENABLE_LOCKING_STYLE || OS_VXWORKS
-# include <sys/ioctl.h>
-# if OS_VXWORKS
-#  include <semaphore.h>
-#  include <limits.h>
-# else
-#  include <sys/file.h>
-#  include <sys/param.h>
-# endif
-#endif /* SQLITE_ENABLE_LOCKING_STYLE */
-
-#if defined(__APPLE__) || (SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS)
-# include <sys/mount.h>
-#endif
-
-#ifdef HAVE_UTIME
-# include <utime.h>
-#endif
-
-/*
-** Allowed values of unixFile.fsFlags
-*/
-#define SQLITE_FSFLAGS_IS_MSDOS     0x1
-
-/*
-** If we are to be thread-safe, include the pthreads header and define
-** the SQLITE_UNIX_THREADS macro.
-*/
-#if SQLITE_THREADSAFE
-# include <pthread.h>
-# define SQLITE_UNIX_THREADS 1
-#endif
-
-/*
-** Default permissions when creating a new file
-*/
-#ifndef SQLITE_DEFAULT_FILE_PERMISSIONS
-# define SQLITE_DEFAULT_FILE_PERMISSIONS 0644
-#endif
-
-/*
-** Default permissions when creating auto proxy dir
-*/
-#ifndef SQLITE_DEFAULT_PROXYDIR_PERMISSIONS
-# define SQLITE_DEFAULT_PROXYDIR_PERMISSIONS 0755
-#endif
-
-/*
-** Maximum supported path-length.
-*/
-#define MAX_PATHNAME 512
-
-/*
-** Only set the lastErrno if the error code is a real error and not 
-** a normal expected return code of SQLITE_BUSY or SQLITE_OK
-*/
-#define IS_LOCK_ERROR(x)  ((x != SQLITE_OK) && (x != SQLITE_BUSY))
-
-/* Forward references */
-typedef struct unixShm unixShm;               /* Connection shared memory */
-typedef struct unixShmNode unixShmNode;       /* Shared memory instance */
-typedef struct unixInodeInfo unixInodeInfo;   /* An i-node */
-typedef struct UnixUnusedFd UnixUnusedFd;     /* An unused file descriptor */
-
-/*
-** Sometimes, after a file handle is closed by SQLite, the file descriptor
-** cannot be closed immediately. In these cases, instances of the following
-** structure are used to store the file descriptor while waiting for an
-** opportunity to either close or reuse it.
-*/
-struct UnixUnusedFd {
-  int fd;                   /* File descriptor to close */
-  int flags;                /* Flags this file descriptor was opened with */
-  UnixUnusedFd *pNext;      /* Next unused file descriptor on same file */
-};
-
-/*
-** The unixFile structure is subclass of sqlite3_file specific to the unix
-** VFS implementations.
-*/
-typedef struct unixFile unixFile;
-struct unixFile {
-  sqlite3_io_methods const *pMethod;  /* Always the first entry */
-  sqlite3_vfs *pVfs;                  /* The VFS that created this unixFile */
-  unixInodeInfo *pInode;              /* Info about locks on this inode */
-  int h;                              /* The file descriptor */
-  unsigned char eFileLock;            /* The type of lock held on this fd */
-  unsigned short int ctrlFlags;       /* Behavioral bits.  UNIXFILE_* flags */
-  int lastErrno;                      /* The unix errno from last I/O error */
-  void *lockingContext;               /* Locking style specific state */
-  UnixUnusedFd *pUnused;              /* Pre-allocated UnixUnusedFd */
-  const char *zPath;                  /* Name of the file */
-  unixShm *pShm;                      /* Shared memory segment information */
-  int szChunk;                        /* Configured by FCNTL_CHUNK_SIZE */
-#if SQLITE_MAX_MMAP_SIZE>0
-  int nFetchOut;                      /* Number of outstanding xFetch refs */
-  sqlite3_int64 mmapSize;             /* Usable size of mapping at pMapRegion */
-  sqlite3_int64 mmapSizeActual;       /* Actual size of mapping at pMapRegion */
-  sqlite3_int64 mmapSizeMax;          /* Configured FCNTL_MMAP_SIZE value */
-  void *pMapRegion;                   /* Memory mapped region */
-#endif
-#ifdef __QNXNTO__
-  int sectorSize;                     /* Device sector size */
-  int deviceCharacteristics;          /* Precomputed device characteristics */
-#endif
-#if SQLITE_ENABLE_LOCKING_STYLE
-  int openFlags;                      /* The flags specified at open() */
-#endif
-#if SQLITE_ENABLE_LOCKING_STYLE || defined(__APPLE__)
-  unsigned fsFlags;                   /* cached details from statfs() */
-#endif
-#if OS_VXWORKS
-  struct vxworksFileId *pId;          /* Unique file ID */
-#endif
-#ifdef SQLITE_DEBUG
-  /* The next group of variables are used to track whether or not the
-  ** transaction counter in bytes 24-27 of database files are updated
-  ** whenever any part of the database changes.  An assertion fault will
-  ** occur if a file is updated without also updating the transaction
-  ** counter.  This test is made to avoid new problems similar to the
-  ** one described by ticket #3584. 
-  */
-  unsigned char transCntrChng;   /* True if the transaction counter changed */
-  unsigned char dbUpdate;        /* True if any part of database file changed */
-  unsigned char inNormalWrite;   /* True if in a normal write operation */
-
-#endif
-
-#ifdef SQLITE_TEST
-  /* In test mode, increase the size of this structure a bit so that 
-  ** it is larger than the struct CrashFile defined in test6.c.
-  */
-  char aPadding[32];
-#endif
-};
-
-/* This variable holds the process id (pid) from when the xRandomness()
-** method was called.  If xOpen() is called from a different process id,
-** indicating that a fork() has occurred, the PRNG will be reset.
-*/
-static int randomnessPid = 0;
-
-/*
-** Allowed values for the unixFile.ctrlFlags bitmask:
-*/
-#define UNIXFILE_EXCL        0x01     /* Connections from one process only */
-#define UNIXFILE_RDONLY      0x02     /* Connection is read only */
-#define UNIXFILE_PERSIST_WAL 0x04     /* Persistent WAL mode */
-#ifndef SQLITE_DISABLE_DIRSYNC
-# define UNIXFILE_DIRSYNC    0x08     /* Directory sync needed */
-#else
-# define UNIXFILE_DIRSYNC    0x00
-#endif
-#define UNIXFILE_PSOW        0x10     /* SQLITE_IOCAP_POWERSAFE_OVERWRITE */
-#define UNIXFILE_DELETE      0x20     /* Delete on close */
-#define UNIXFILE_URI         0x40     /* Filename might have query parameters */
-#define UNIXFILE_NOLOCK      0x80     /* Do no file locking */
-#define UNIXFILE_WARNED    0x0100     /* verifyDbFile() warnings have been issued */
-
-/*
-** Include code that is common to all os_*.c files
-*/
-#include "os_common.h"
-
-/*
-** Define various macros that are missing from some systems.
-*/
-#ifndef O_LARGEFILE
-# define O_LARGEFILE 0
-#endif
-#ifdef SQLITE_DISABLE_LFS
-# undef O_LARGEFILE
-# define O_LARGEFILE 0
-#endif
-#ifndef O_NOFOLLOW
-# define O_NOFOLLOW 0
-#endif
-#ifndef O_BINARY
-# define O_BINARY 0
-#endif
-
-/*
-** The threadid macro resolves to the thread-id or to 0.  Used for
-** testing and debugging only.
-*/
-#if SQLITE_THREADSAFE
-#define threadid pthread_self()
-#else
-#define threadid 0
-#endif
-
-/*
-** HAVE_MREMAP defaults to true on Linux and false everywhere else.
-*/
-#if !defined(HAVE_MREMAP)
-# if defined(__linux__) && defined(_GNU_SOURCE)
-#  define HAVE_MREMAP 1
-# else
-#  define HAVE_MREMAP 0
-# endif
-#endif
-
-/*
-** Explicitly call the 64-bit version of lseek() on Android. Otherwise, lseek()
-** is the 32-bit version, even if _FILE_OFFSET_BITS=64 is defined.
-*/
-#ifdef __ANDROID__
-# define lseek lseek64
-#endif
-
-/*
-** Different Unix systems declare open() in different ways.  Same use
-** open(const char*,int,mode_t).  Others use open(const char*,int,...).
-** The difference is important when using a pointer to the function.
-**
-** The safest way to deal with the problem is to always use this wrapper
-** which always has the same well-defined interface.
-*/
-static int posixOpen(const char *zFile, int flags, int mode){
-  return open(zFile, flags, mode);
-}
-
-/*
-** On some systems, calls to fchown() will trigger a message in a security
-** log if they come from non-root processes.  So avoid calling fchown() if
-** we are not running as root.
-*/
-static int posixFchown(int fd, uid_t uid, gid_t gid){
-#if OS_VXWORKS
-  return 0;
-#else
-  return geteuid() ? 0 : fchown(fd,uid,gid);
-#endif
-}
-
-/* Forward reference */
-static int openDirectory(const char*, int*);
-static int unixGetpagesize(void);
-
-/*
-** Many system calls are accessed through pointer-to-functions so that
-** they may be overridden at runtime to facilitate fault injection during
-** testing and sandboxing.  The following array holds the names and pointers
-** to all overrideable system calls.
-*/
-static struct unix_syscall {
-  const char *zName;            /* Name of the system call */
-  sqlite3_syscall_ptr pCurrent; /* Current value of the system call */
-  sqlite3_syscall_ptr pDefault; /* Default value */
-} aSyscall[] = {
-  { "open",         (sqlite3_syscall_ptr)posixOpen,  0  },
-#define osOpen      ((int(*)(const char*,int,int))aSyscall[0].pCurrent)
-
-  { "close",        (sqlite3_syscall_ptr)close,      0  },
-#define osClose     ((int(*)(int))aSyscall[1].pCurrent)
-
-  { "access",       (sqlite3_syscall_ptr)access,     0  },
-#define osAccess    ((int(*)(const char*,int))aSyscall[2].pCurrent)
-
-  { "getcwd",       (sqlite3_syscall_ptr)getcwd,     0  },
-#define osGetcwd    ((char*(*)(char*,size_t))aSyscall[3].pCurrent)
-
-  { "stat",         (sqlite3_syscall_ptr)stat,       0  },
-#define osStat      ((int(*)(const char*,struct stat*))aSyscall[4].pCurrent)
-
-/*
-** The DJGPP compiler environment looks mostly like Unix, but it
-** lacks the fcntl() system call.  So redefine fcntl() to be something
-** that always succeeds.  This means that locking does not occur under
-** DJGPP.  But it is DOS - what did you expect?
-*/
-#ifdef __DJGPP__
-  { "fstat",        0,                 0  },
-#define osFstat(a,b,c)    0
-#else     
-  { "fstat",        (sqlite3_syscall_ptr)fstat,      0  },
-#define osFstat     ((int(*)(int,struct stat*))aSyscall[5].pCurrent)
-#endif
-
-  { "ftruncate",    (sqlite3_syscall_ptr)ftruncate,  0  },
-#define osFtruncate ((int(*)(int,off_t))aSyscall[6].pCurrent)
-
-  { "fcntl",        (sqlite3_syscall_ptr)fcntl,      0  },
-#define osFcntl     ((int(*)(int,int,...))aSyscall[7].pCurrent)
-
-  { "read",         (sqlite3_syscall_ptr)read,       0  },
-#define osRead      ((ssize_t(*)(int,void*,size_t))aSyscall[8].pCurrent)
-
-#if defined(USE_PREAD) || (SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS)
-  { "pread",        (sqlite3_syscall_ptr)pread,      0  },
-#else
-  { "pread",        (sqlite3_syscall_ptr)0,          0  },
-#endif
-#define osPread     ((ssize_t(*)(int,void*,size_t,off_t))aSyscall[9].pCurrent)
-
-#if defined(USE_PREAD64)
-  { "pread64",      (sqlite3_syscall_ptr)pread64,    0  },
-#else
-  { "pread64",      (sqlite3_syscall_ptr)0,          0  },
-#endif
-#define osPread64   ((ssize_t(*)(int,void*,size_t,off_t))aSyscall[10].pCurrent)
-
-  { "write",        (sqlite3_syscall_ptr)write,      0  },
-#define osWrite     ((ssize_t(*)(int,const void*,size_t))aSyscall[11].pCurrent)
-
-#if defined(USE_PREAD) || (SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS)
-  { "pwrite",       (sqlite3_syscall_ptr)pwrite,     0  },
-#else
-  { "pwrite",       (sqlite3_syscall_ptr)0,          0  },
-#endif
-#define osPwrite    ((ssize_t(*)(int,const void*,size_t,off_t))\
-                    aSyscall[12].pCurrent)
-
-#if defined(USE_PREAD64)
-  { "pwrite64",     (sqlite3_syscall_ptr)pwrite64,   0  },
-#else
-  { "pwrite64",     (sqlite3_syscall_ptr)0,          0  },
-#endif
-#define osPwrite64  ((ssize_t(*)(int,const void*,size_t,off_t))\
-                    aSyscall[13].pCurrent)
-
-  { "fchmod",       (sqlite3_syscall_ptr)fchmod,     0  },
-#define osFchmod    ((int(*)(int,mode_t))aSyscall[14].pCurrent)
-
-#if defined(HAVE_POSIX_FALLOCATE) && HAVE_POSIX_FALLOCATE
-  { "fallocate",    (sqlite3_syscall_ptr)posix_fallocate,  0 },
-#else
-  { "fallocate",    (sqlite3_syscall_ptr)0,                0 },
-#endif
-#define osFallocate ((int(*)(int,off_t,off_t))aSyscall[15].pCurrent)
-
-  { "unlink",       (sqlite3_syscall_ptr)unlink,           0 },
-#define osUnlink    ((int(*)(const char*))aSyscall[16].pCurrent)
-
-  { "openDirectory",    (sqlite3_syscall_ptr)openDirectory,      0 },
-#define osOpenDirectory ((int(*)(const char*,int*))aSyscall[17].pCurrent)
-
-  { "mkdir",        (sqlite3_syscall_ptr)mkdir,           0 },
-#define osMkdir     ((int(*)(const char*,mode_t))aSyscall[18].pCurrent)
-
-  { "rmdir",        (sqlite3_syscall_ptr)rmdir,           0 },
-#define osRmdir     ((int(*)(const char*))aSyscall[19].pCurrent)
-
-  { "fchown",       (sqlite3_syscall_ptr)posixFchown,     0 },
-#define osFchown    ((int(*)(int,uid_t,gid_t))aSyscall[20].pCurrent)
-
-#if !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0
-  { "mmap",       (sqlite3_syscall_ptr)mmap,     0 },
-#define osMmap ((void*(*)(void*,size_t,int,int,int,off_t))aSyscall[21].pCurrent)
-
-  { "munmap",       (sqlite3_syscall_ptr)munmap,          0 },
-#define osMunmap ((void*(*)(void*,size_t))aSyscall[22].pCurrent)
-
-#if HAVE_MREMAP
-  { "mremap",       (sqlite3_syscall_ptr)mremap,          0 },
-#else
-  { "mremap",       (sqlite3_syscall_ptr)0,               0 },
-#endif
-#define osMremap ((void*(*)(void*,size_t,size_t,int,...))aSyscall[23].pCurrent)
-  { "getpagesize",  (sqlite3_syscall_ptr)unixGetpagesize, 0 },
-#define osGetpagesize ((int(*)(void))aSyscall[24].pCurrent)
-
-#endif
-
-}; /* End of the overrideable system calls */
-
-/*
-** This is the xSetSystemCall() method of sqlite3_vfs for all of the
-** "unix" VFSes.  Return SQLITE_OK opon successfully updating the
-** system call pointer, or SQLITE_NOTFOUND if there is no configurable
-** system call named zName.
-*/
-static int unixSetSystemCall(
-  sqlite3_vfs *pNotUsed,        /* The VFS pointer.  Not used */
-  const char *zName,            /* Name of system call to override */
-  sqlite3_syscall_ptr pNewFunc  /* Pointer to new system call value */
-){
-  unsigned int i;
-  int rc = SQLITE_NOTFOUND;
-
-  UNUSED_PARAMETER(pNotUsed);
-  if( zName==0 ){
-    /* If no zName is given, restore all system calls to their default
-    ** settings and return NULL
-    */
-    rc = SQLITE_OK;
-    for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
-      if( aSyscall[i].pDefault ){
-        aSyscall[i].pCurrent = aSyscall[i].pDefault;
-      }
-    }
-  }else{
-    /* If zName is specified, operate on only the one system call
-    ** specified.
-    */
-    for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
-      if( strcmp(zName, aSyscall[i].zName)==0 ){
-        if( aSyscall[i].pDefault==0 ){
-          aSyscall[i].pDefault = aSyscall[i].pCurrent;
-        }
-        rc = SQLITE_OK;
-        if( pNewFunc==0 ) pNewFunc = aSyscall[i].pDefault;
-        aSyscall[i].pCurrent = pNewFunc;
-        break;
-      }
-    }
-  }
-  return rc;
-}
-
-/*
-** Return the value of a system call.  Return NULL if zName is not a
-** recognized system call name.  NULL is also returned if the system call
-** is currently undefined.
-*/
-static sqlite3_syscall_ptr unixGetSystemCall(
-  sqlite3_vfs *pNotUsed,
-  const char *zName
-){
-  unsigned int i;
-
-  UNUSED_PARAMETER(pNotUsed);
-  for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
-    if( strcmp(zName, aSyscall[i].zName)==0 ) return aSyscall[i].pCurrent;
-  }
-  return 0;
-}
-
-/*
-** Return the name of the first system call after zName.  If zName==NULL
-** then return the name of the first system call.  Return NULL if zName
-** is the last system call or if zName is not the name of a valid
-** system call.
-*/
-static const char *unixNextSystemCall(sqlite3_vfs *p, const char *zName){
-  int i = -1;
-
-  UNUSED_PARAMETER(p);
-  if( zName ){
-    for(i=0; i<ArraySize(aSyscall)-1; i++){
-      if( strcmp(zName, aSyscall[i].zName)==0 ) break;
-    }
-  }
-  for(i++; i<ArraySize(aSyscall); i++){
-    if( aSyscall[i].pCurrent!=0 ) return aSyscall[i].zName;
-  }
-  return 0;
-}
-
-/*
-** Do not accept any file descriptor less than this value, in order to avoid
-** opening database file using file descriptors that are commonly used for 
-** standard input, output, and error.
-*/
-#ifndef SQLITE_MINIMUM_FILE_DESCRIPTOR
-# define SQLITE_MINIMUM_FILE_DESCRIPTOR 3
-#endif
-
-/*
-** Invoke open().  Do so multiple times, until it either succeeds or
-** fails for some reason other than EINTR.
-**
-** If the file creation mode "m" is 0 then set it to the default for
-** SQLite.  The default is SQLITE_DEFAULT_FILE_PERMISSIONS (normally
-** 0644) as modified by the system umask.  If m is not 0, then
-** make the file creation mode be exactly m ignoring the umask.
-**
-** The m parameter will be non-zero only when creating -wal, -journal,
-** and -shm files.  We want those files to have *exactly* the same
-** permissions as their original database, unadulterated by the umask.
-** In that way, if a database file is -rw-rw-rw or -rw-rw-r-, and a
-** transaction crashes and leaves behind hot journals, then any
-** process that is able to write to the database will also be able to
-** recover the hot journals.
-*/
-static int robust_open(const char *z, int f, mode_t m){
-  int fd;
-  mode_t m2 = m ? m : SQLITE_DEFAULT_FILE_PERMISSIONS;
-  while(1){
-#if defined(O_CLOEXEC)
-    fd = osOpen(z,f|O_CLOEXEC,m2);
-#else
-    fd = osOpen(z,f,m2);
-#endif
-    if( fd<0 ){
-      if( errno==EINTR ) continue;
-      break;
-    }
-    if( fd>=SQLITE_MINIMUM_FILE_DESCRIPTOR ) break;
-    osClose(fd);
-    sqlite3_log(SQLITE_WARNING, 
-                "attempt to open \"%s\" as file descriptor %d", z, fd);
-    fd = -1;
-    if( osOpen("/dev/null", f, m)<0 ) break;
-  }
-  if( fd>=0 ){
-    if( m!=0 ){
-      struct stat statbuf;
-      if( osFstat(fd, &statbuf)==0 
-       && statbuf.st_size==0
-       && (statbuf.st_mode&0777)!=m 
-      ){
-        osFchmod(fd, m);
-      }
-    }
-#if defined(FD_CLOEXEC) && (!defined(O_CLOEXEC) || O_CLOEXEC==0)
-    osFcntl(fd, F_SETFD, osFcntl(fd, F_GETFD, 0) | FD_CLOEXEC);
-#endif
-  }
-  return fd;
-}
-
-/*
-** Helper functions to obtain and relinquish the global mutex. The
-** global mutex is used to protect the unixInodeInfo and
-** vxworksFileId objects used by this file, all of which may be 
-** shared by multiple threads.
-**
-** Function unixMutexHeld() is used to assert() that the global mutex 
-** is held when required. This function is only used as part of assert() 
-** statements. e.g.
-**
-**   unixEnterMutex()
-**     assert( unixMutexHeld() );
-**   unixEnterLeave()
-*/
-static void unixEnterMutex(void){
-  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
-}
-static void unixLeaveMutex(void){
-  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
-}
-#ifdef SQLITE_DEBUG
-static int unixMutexHeld(void) {
-  return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
-}
-#endif
-
-
-#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
-/*
-** Helper function for printing out trace information from debugging
-** binaries. This returns the string representation of the supplied
-** integer lock-type.
-*/
-static const char *azFileLock(int eFileLock){
-  switch( eFileLock ){
-    case NO_LOCK: return "NONE";
-    case SHARED_LOCK: return "SHARED";
-    case RESERVED_LOCK: return "RESERVED";
-    case PENDING_LOCK: return "PENDING";
-    case EXCLUSIVE_LOCK: return "EXCLUSIVE";
-  }
-  return "ERROR";
-}
-#endif
-
-#ifdef SQLITE_LOCK_TRACE
-/*
-** Print out information about all locking operations.
-**
-** This routine is used for troubleshooting locks on multithreaded
-** platforms.  Enable by compiling with the -DSQLITE_LOCK_TRACE
-** command-line option on the compiler.  This code is normally
-** turned off.
-*/
-static int lockTrace(int fd, int op, struct flock *p){
-  char *zOpName, *zType;
-  int s;
-  int savedErrno;
-  if( op==F_GETLK ){
-    zOpName = "GETLK";
-  }else if( op==F_SETLK ){
-    zOpName = "SETLK";
-  }else{
-    s = osFcntl(fd, op, p);
-    sqlite3DebugPrintf("fcntl unknown %d %d %d\n", fd, op, s);
-    return s;
-  }
-  if( p->l_type==F_RDLCK ){
-    zType = "RDLCK";
-  }else if( p->l_type==F_WRLCK ){
-    zType = "WRLCK";
-  }else if( p->l_type==F_UNLCK ){
-    zType = "UNLCK";
-  }else{
-    assert( 0 );
-  }
-  assert( p->l_whence==SEEK_SET );
-  s = osFcntl(fd, op, p);
-  savedErrno = errno;
-  sqlite3DebugPrintf("fcntl %d %d %s %s %d %d %d %d\n",
-     threadid, fd, zOpName, zType, (int)p->l_start, (int)p->l_len,
-     (int)p->l_pid, s);
-  if( s==(-1) && op==F_SETLK && (p->l_type==F_RDLCK || p->l_type==F_WRLCK) ){
-    struct flock l2;
-    l2 = *p;
-    osFcntl(fd, F_GETLK, &l2);
-    if( l2.l_type==F_RDLCK ){
-      zType = "RDLCK";
-    }else if( l2.l_type==F_WRLCK ){
-      zType = "WRLCK";
-    }else if( l2.l_type==F_UNLCK ){
-      zType = "UNLCK";
-    }else{
-      assert( 0 );
-    }
-    sqlite3DebugPrintf("fcntl-failure-reason: %s %d %d %d\n",
-       zType, (int)l2.l_start, (int)l2.l_len, (int)l2.l_pid);
-  }
-  errno = savedErrno;
-  return s;
-}
-#undef osFcntl
-#define osFcntl lockTrace
-#endif /* SQLITE_LOCK_TRACE */
-
-/*
-** Retry ftruncate() calls that fail due to EINTR
-**
-** All calls to ftruncate() within this file should be made through this wrapper.
-** On the Android platform, bypassing the logic below could lead to a corrupt
-** database.
-*/
-static int robust_ftruncate(int h, sqlite3_int64 sz){
-  int rc;
-#ifdef __ANDROID__
-  /* On Android, ftruncate() always uses 32-bit offsets, even if 
-  ** _FILE_OFFSET_BITS=64 is defined. This means it is unsafe to attempt to
-  ** truncate a file to any size larger than 2GiB. Silently ignore any
-  ** such attempts.  */
-  if( sz>(sqlite3_int64)0x7FFFFFFF ){
-    rc = SQLITE_OK;
-  }else
-#endif
-  do{ rc = osFtruncate(h,sz); }while( rc<0 && errno==EINTR );
-  return rc;
-}
-
-/*
-** This routine translates a standard POSIX errno code into something
-** useful to the clients of the sqlite3 functions.  Specifically, it is
-** intended to translate a variety of "try again" errors into SQLITE_BUSY
-** and a variety of "please close the file descriptor NOW" errors into 
-** SQLITE_IOERR
-** 
-** Errors during initialization of locks, or file system support for locks,
-** should handle ENOLCK, ENOTSUP, EOPNOTSUPP separately.
-*/
-static int sqliteErrorFromPosixError(int posixError, int sqliteIOErr) {
-  switch (posixError) {
-#if 0
-  /* At one point this code was not commented out. In theory, this branch
-  ** should never be hit, as this function should only be called after
-  ** a locking-related function (i.e. fcntl()) has returned non-zero with
-  ** the value of errno as the first argument. Since a system call has failed,
-  ** errno should be non-zero.
-  **
-  ** Despite this, if errno really is zero, we still don't want to return
-  ** SQLITE_OK. The system call failed, and *some* SQLite error should be
-  ** propagated back to the caller. Commenting this branch out means errno==0
-  ** will be handled by the "default:" case below.
-  */
-  case 0: 
-    return SQLITE_OK;
-#endif
-
-  case EAGAIN:
-  case ETIMEDOUT:
-  case EBUSY:
-  case EINTR:
-  case ENOLCK:  
-    /* random NFS retry error, unless during file system support 
-     * introspection, in which it actually means what it says */
-    return SQLITE_BUSY;
-    
-  case EACCES: 
-    /* EACCES is like EAGAIN during locking operations, but not any other time*/
-    if( (sqliteIOErr == SQLITE_IOERR_LOCK) || 
-        (sqliteIOErr == SQLITE_IOERR_UNLOCK) || 
-        (sqliteIOErr == SQLITE_IOERR_RDLOCK) ||
-        (sqliteIOErr == SQLITE_IOERR_CHECKRESERVEDLOCK) ){
-      return SQLITE_BUSY;
-    }
-    /* else fall through */
-  case EPERM: 
-    return SQLITE_PERM;
-    
-#if EOPNOTSUPP!=ENOTSUP
-  case EOPNOTSUPP: 
-    /* something went terribly awry, unless during file system support 
-     * introspection, in which it actually means what it says */
-#endif
-#ifdef ENOTSUP
-  case ENOTSUP: 
-    /* invalid fd, unless during file system support introspection, in which 
-     * it actually means what it says */
-#endif
-  case EIO:
-  case EBADF:
-  case EINVAL:
-  case ENOTCONN:
-  case ENODEV:
-  case ENXIO:
-  case ENOENT:
-#ifdef ESTALE                     /* ESTALE is not defined on Interix systems */
-  case ESTALE:
-#endif
-  case ENOSYS:
-    /* these should force the client to close the file and reconnect */
-    
-  default: 
-    return sqliteIOErr;
-  }
-}
-
-
-/******************************************************************************
-****************** Begin Unique File ID Utility Used By VxWorks ***************
-**
-** On most versions of unix, we can get a unique ID for a file by concatenating
-** the device number and the inode number.  But this does not work on VxWorks.
-** On VxWorks, a unique file id must be based on the canonical filename.
-**
-** A pointer to an instance of the following structure can be used as a
-** unique file ID in VxWorks.  Each instance of this structure contains
-** a copy of the canonical filename.  There is also a reference count.  
-** The structure is reclaimed when the number of pointers to it drops to
-** zero.
-**
-** There are never very many files open at one time and lookups are not
-** a performance-critical path, so it is sufficient to put these
-** structures on a linked list.
-*/
-struct vxworksFileId {
-  struct vxworksFileId *pNext;  /* Next in a list of them all */
-  int nRef;                     /* Number of references to this one */
-  int nName;                    /* Length of the zCanonicalName[] string */
-  char *zCanonicalName;         /* Canonical filename */
-};
-
-#if OS_VXWORKS
-/* 
-** All unique filenames are held on a linked list headed by this
-** variable:
-*/
-static struct vxworksFileId *vxworksFileList = 0;
-
-/*
-** Simplify a filename into its canonical form
-** by making the following changes:
-**
-**  * removing any trailing and duplicate /
-**  * convert /./ into just /
-**  * convert /A/../ where A is any simple name into just /
-**
-** Changes are made in-place.  Return the new name length.
-**
-** The original filename is in z[0..n-1].  Return the number of
-** characters in the simplified name.
-*/
-static int vxworksSimplifyName(char *z, int n){
-  int i, j;
-  while( n>1 && z[n-1]=='/' ){ n--; }
-  for(i=j=0; i<n; i++){
-    if( z[i]=='/' ){
-      if( z[i+1]=='/' ) continue;
-      if( z[i+1]=='.' && i+2<n && z[i+2]=='/' ){
-        i += 1;
-        continue;
-      }
-      if( z[i+1]=='.' && i+3<n && z[i+2]=='.' && z[i+3]=='/' ){
-        while( j>0 && z[j-1]!='/' ){ j--; }
-        if( j>0 ){ j--; }
-        i += 2;
-        continue;
-      }
-    }
-    z[j++] = z[i];
-  }
-  z[j] = 0;
-  return j;
-}
-
-/*
-** Find a unique file ID for the given absolute pathname.  Return
-** a pointer to the vxworksFileId object.  This pointer is the unique
-** file ID.
-**
-** The nRef field of the vxworksFileId object is incremented before
-** the object is returned.  A new vxworksFileId object is created
-** and added to the global list if necessary.
-**
-** If a memory allocation error occurs, return NULL.
-*/
-static struct vxworksFileId *vxworksFindFileId(const char *zAbsoluteName){
-  struct vxworksFileId *pNew;         /* search key and new file ID */
-  struct vxworksFileId *pCandidate;   /* For looping over existing file IDs */
-  int n;                              /* Length of zAbsoluteName string */
-
-  assert( zAbsoluteName[0]=='/' );
-  n = (int)strlen(zAbsoluteName);
-  pNew = sqlite3_malloc( sizeof(*pNew) + (n+1) );
-  if( pNew==0 ) return 0;
-  pNew->zCanonicalName = (char*)&pNew[1];
-  memcpy(pNew->zCanonicalName, zAbsoluteName, n+1);
-  n = vxworksSimplifyName(pNew->zCanonicalName, n);
-
-  /* Search for an existing entry that matching the canonical name.
-  ** If found, increment the reference count and return a pointer to
-  ** the existing file ID.
-  */
-  unixEnterMutex();
-  for(pCandidate=vxworksFileList; pCandidate; pCandidate=pCandidate->pNext){
-    if( pCandidate->nName==n 
-     && memcmp(pCandidate->zCanonicalName, pNew->zCanonicalName, n)==0
-    ){
-       sqlite3_free(pNew);
-       pCandidate->nRef++;
-       unixLeaveMutex();
-       return pCandidate;
-    }
-  }
-
-  /* No match was found.  We will make a new file ID */
-  pNew->nRef = 1;
-  pNew->nName = n;
-  pNew->pNext = vxworksFileList;
-  vxworksFileList = pNew;
-  unixLeaveMutex();
-  return pNew;
-}
-
-/*
-** Decrement the reference count on a vxworksFileId object.  Free
-** the object when the reference count reaches zero.
-*/
-static void vxworksReleaseFileId(struct vxworksFileId *pId){
-  unixEnterMutex();
-  assert( pId->nRef>0 );
-  pId->nRef--;
-  if( pId->nRef==0 ){
-    struct vxworksFileId **pp;
-    for(pp=&vxworksFileList; *pp && *pp!=pId; pp = &((*pp)->pNext)){}
-    assert( *pp==pId );
-    *pp = pId->pNext;
-    sqlite3_free(pId);
-  }
-  unixLeaveMutex();
-}
-#endif /* OS_VXWORKS */
-/*************** End of Unique File ID Utility Used By VxWorks ****************
-******************************************************************************/
-
-
-/******************************************************************************
-*************************** Posix Advisory Locking ****************************
-**
-** POSIX advisory locks are broken by design.  ANSI STD 1003.1 (1996)
-** section 6.5.2.2 lines 483 through 490 specify that when a process
-** sets or clears a lock, that operation overrides any prior locks set
-** by the same process.  It does not explicitly say so, but this implies
-** that it overrides locks set by the same process using a different
-** file descriptor.  Consider this test case:
-**
-**       int fd1 = open("./file1", O_RDWR|O_CREAT, 0644);
-**       int fd2 = open("./file2", O_RDWR|O_CREAT, 0644);
-**
-** Suppose ./file1 and ./file2 are really the same file (because
-** one is a hard or symbolic link to the other) then if you set
-** an exclusive lock on fd1, then try to get an exclusive lock
-** on fd2, it works.  I would have expected the second lock to
-** fail since there was already a lock on the file due to fd1.
-** But not so.  Since both locks came from the same process, the
-** second overrides the first, even though they were on different
-** file descriptors opened on different file names.
-**
-** This means that we cannot use POSIX locks to synchronize file access
-** among competing threads of the same process.  POSIX locks will work fine
-** to synchronize access for threads in separate processes, but not
-** threads within the same process.
-**
-** To work around the problem, SQLite has to manage file locks internally
-** on its own.  Whenever a new database is opened, we have to find the
-** specific inode of the database file (the inode is determined by the
-** st_dev and st_ino fields of the stat structure that fstat() fills in)
-** and check for locks already existing on that inode.  When locks are
-** created or removed, we have to look at our own internal record of the
-** locks to see if another thread has previously set a lock on that same
-** inode.
-**
-** (Aside: The use of inode numbers as unique IDs does not work on VxWorks.
-** For VxWorks, we have to use the alternative unique ID system based on
-** canonical filename and implemented in the previous division.)
-**
-** The sqlite3_file structure for POSIX is no longer just an integer file
-** descriptor.  It is now a structure that holds the integer file
-** descriptor and a pointer to a structure that describes the internal
-** locks on the corresponding inode.  There is one locking structure
-** per inode, so if the same inode is opened twice, both unixFile structures
-** point to the same locking structure.  The locking structure keeps
-** a reference count (so we will know when to delete it) and a "cnt"
-** field that tells us its internal lock status.  cnt==0 means the
-** file is unlocked.  cnt==-1 means the file has an exclusive lock.
-** cnt>0 means there are cnt shared locks on the file.
-**
-** Any attempt to lock or unlock a file first checks the locking
-** structure.  The fcntl() system call is only invoked to set a 
-** POSIX lock if the internal lock structure transitions between
-** a locked and an unlocked state.
-**
-** But wait:  there are yet more problems with POSIX advisory locks.
-**
-** If you close a file descriptor that points to a file that has locks,
-** all locks on that file that are owned by the current process are
-** released.  To work around this problem, each unixInodeInfo object
-** maintains a count of the number of pending locks on tha inode.
-** When an attempt is made to close an unixFile, if there are
-** other unixFile open on the same inode that are holding locks, the call
-** to close() the file descriptor is deferred until all of the locks clear.
-** The unixInodeInfo structure keeps a list of file descriptors that need to
-** be closed and that list is walked (and cleared) when the last lock
-** clears.
-**
-** Yet another problem:  LinuxThreads do not play well with posix locks.
-**
-** Many older versions of linux use the LinuxThreads library which is
-** not posix compliant.  Under LinuxThreads, a lock created by thread
-** A cannot be modified or overridden by a different thread B.
-** Only thread A can modify the lock.  Locking behavior is correct
-** if the appliation uses the newer Native Posix Thread Library (NPTL)
-** on linux - with NPTL a lock created by thread A can override locks
-** in thread B.  But there is no way to know at compile-time which
-** threading library is being used.  So there is no way to know at
-** compile-time whether or not thread A can override locks on thread B.
-** One has to do a run-time check to discover the behavior of the
-** current process.
-**
-** SQLite used to support LinuxThreads.  But support for LinuxThreads
-** was dropped beginning with version 3.7.0.  SQLite will still work with
-** LinuxThreads provided that (1) there is no more than one connection 
-** per database file in the same process and (2) database connections
-** do not move across threads.
-*/
-
-/*
-** An instance of the following structure serves as the key used
-** to locate a particular unixInodeInfo object.
-*/
-struct unixFileId {
-  dev_t dev;                  /* Device number */
-#if OS_VXWORKS
-  struct vxworksFileId *pId;  /* Unique file ID for vxworks. */
-#else
-  ino_t ino;                  /* Inode number */
-#endif
-};
-
-/*
-** An instance of the following structure is allocated for each open
-** inode.  Or, on LinuxThreads, there is one of these structures for
-** each inode opened by each thread.
-**
-** A single inode can have multiple file descriptors, so each unixFile
-** structure contains a pointer to an instance of this object and this
-** object keeps a count of the number of unixFile pointing to it.
-*/
-struct unixInodeInfo {
-  struct unixFileId fileId;       /* The lookup key */
-  int nShared;                    /* Number of SHARED locks held */
-  unsigned char eFileLock;        /* One of SHARED_LOCK, RESERVED_LOCK etc. */
-  unsigned char bProcessLock;     /* An exclusive process lock is held */
-  int nRef;                       /* Number of pointers to this structure */
-  unixShmNode *pShmNode;          /* Shared memory associated with this inode */
-  int nLock;                      /* Number of outstanding file locks */
-  UnixUnusedFd *pUnused;          /* Unused file descriptors to close */
-  unixInodeInfo *pNext;           /* List of all unixInodeInfo objects */
-  unixInodeInfo *pPrev;           /*    .... doubly linked */
-#if SQLITE_ENABLE_LOCKING_STYLE
-  unsigned long long sharedByte;  /* for AFP simulated shared lock */
-#endif
-#if OS_VXWORKS
-  sem_t *pSem;                    /* Named POSIX semaphore */
-  char aSemName[MAX_PATHNAME+2];  /* Name of that semaphore */
-#endif
-};
-
-/*
-** A lists of all unixInodeInfo objects.
-*/
-static unixInodeInfo *inodeList = 0;
-
-/*
-**
-** This function - unixLogError_x(), is only ever called via the macro
-** unixLogError().
-**
-** It is invoked after an error occurs in an OS function and errno has been
-** set. It logs a message using sqlite3_log() containing the current value of
-** errno and, if possible, the human-readable equivalent from strerror() or
-** strerror_r().
-**
-** The first argument passed to the macro should be the error code that
-** will be returned to SQLite (e.g. SQLITE_IOERR_DELETE, SQLITE_CANTOPEN). 
-** The two subsequent arguments should be the name of the OS function that
-** failed (e.g. "unlink", "open") and the associated file-system path,
-** if any.
-*/
-#define unixLogError(a,b,c)     unixLogErrorAtLine(a,b,c,__LINE__)
-static int unixLogErrorAtLine(
-  int errcode,                    /* SQLite error code */
-  const char *zFunc,              /* Name of OS function that failed */
-  const char *zPath,              /* File path associated with error */
-  int iLine                       /* Source line number where error occurred */
-){
-  char *zErr;                     /* Message from strerror() or equivalent */
-  int iErrno = errno;             /* Saved syscall error number */
-
-  /* If this is not a threadsafe build (SQLITE_THREADSAFE==0), then use
-  ** the strerror() function to obtain the human-readable error message
-  ** equivalent to errno. Otherwise, use strerror_r().
-  */ 
-#if SQLITE_THREADSAFE && defined(HAVE_STRERROR_R)
-  char aErr[80];
-  memset(aErr, 0, sizeof(aErr));
-  zErr = aErr;
-
-  /* If STRERROR_R_CHAR_P (set by autoconf scripts) or __USE_GNU is defined,
-  ** assume that the system provides the GNU version of strerror_r() that
-  ** returns a pointer to a buffer containing the error message. That pointer 
-  ** may point to aErr[], or it may point to some static storage somewhere. 
-  ** Otherwise, assume that the system provides the POSIX version of 
-  ** strerror_r(), which always writes an error message into aErr[].
-  **
-  ** If the code incorrectly assumes that it is the POSIX version that is
-  ** available, the error message will often be an empty string. Not a
-  ** huge problem. Incorrectly concluding that the GNU version is available 
-  ** could lead to a segfault though.
-  */
-#if defined(STRERROR_R_CHAR_P) || defined(__USE_GNU)
-  zErr = 
-# endif
-  strerror_r(iErrno, aErr, sizeof(aErr)-1);
-
-#elif SQLITE_THREADSAFE
-  /* This is a threadsafe build, but strerror_r() is not available. */
-  zErr = "";
-#else
-  /* Non-threadsafe build, use strerror(). */
-  zErr = strerror(iErrno);
-#endif
-
-  if( zPath==0 ) zPath = "";
-  sqlite3_log(errcode,
-      "os_unix.c:%d: (%d) %s(%s) - %s",
-      iLine, iErrno, zFunc, zPath, zErr
-  );
-
-  return errcode;
-}
-
-/*
-** Close a file descriptor.
-**
-** We assume that close() almost always works, since it is only in a
-** very sick application or on a very sick platform that it might fail.
-** If it does fail, simply leak the file descriptor, but do log the
-** error.
-**
-** Note that it is not safe to retry close() after EINTR since the
-** file descriptor might have already been reused by another thread.
-** So we don't even try to recover from an EINTR.  Just log the error
-** and move on.
-*/
-static void robust_close(unixFile *pFile, int h, int lineno){
-  if( osClose(h) ){
-    unixLogErrorAtLine(SQLITE_IOERR_CLOSE, "close",
-                       pFile ? pFile->zPath : 0, lineno);
-  }
-}
-
-/*
-** Close all file descriptors accumuated in the unixInodeInfo->pUnused list.
-*/ 
-static void closePendingFds(unixFile *pFile){
-  unixInodeInfo *pInode = pFile->pInode;
-  UnixUnusedFd *p;
-  UnixUnusedFd *pNext;
-  for(p=pInode->pUnused; p; p=pNext){
-    pNext = p->pNext;
-    robust_close(pFile, p->fd, __LINE__);
-    sqlite3_free(p);
-  }
-  pInode->pUnused = 0;
-}
-
-/*
-** Release a unixInodeInfo structure previously allocated by findInodeInfo().
-**
-** The mutex entered using the unixEnterMutex() function must be held
-** when this function is called.
-*/
-static void releaseInodeInfo(unixFile *pFile){
-  unixInodeInfo *pInode = pFile->pInode;
-  assert( unixMutexHeld() );
-  if( ALWAYS(pInode) ){
-    pInode->nRef--;
-    if( pInode->nRef==0 ){
-      assert( pInode->pShmNode==0 );
-      closePendingFds(pFile);
-      if( pInode->pPrev ){
-        assert( pInode->pPrev->pNext==pInode );
-        pInode->pPrev->pNext = pInode->pNext;
-      }else{
-        assert( inodeList==pInode );
-        inodeList = pInode->pNext;
-      }
-      if( pInode->pNext ){
-        assert( pInode->pNext->pPrev==pInode );
-        pInode->pNext->pPrev = pInode->pPrev;
-      }
-      sqlite3_free(pInode);
-    }
-  }
-}
-
-/*
-** Given a file descriptor, locate the unixInodeInfo object that
-** describes that file descriptor.  Create a new one if necessary.  The
-** return value might be uninitialized if an error occurs.
-**
-** The mutex entered using the unixEnterMutex() function must be held
-** when this function is called.
-**
-** Return an appropriate error code.
-*/
-static int findInodeInfo(
-  unixFile *pFile,               /* Unix file with file desc used in the key */
-  unixInodeInfo **ppInode        /* Return the unixInodeInfo object here */
-){
-  int rc;                        /* System call return code */
-  int fd;                        /* The file descriptor for pFile */
-  struct unixFileId fileId;      /* Lookup key for the unixInodeInfo */
-  struct stat statbuf;           /* Low-level file information */
-  unixInodeInfo *pInode = 0;     /* Candidate unixInodeInfo object */
-
-  assert( unixMutexHeld() );
-
-  /* Get low-level information about the file that we can used to
-  ** create a unique name for the file.
-  */
-  fd = pFile->h;
-  rc = osFstat(fd, &statbuf);
-  if( rc!=0 ){
-    pFile->lastErrno = errno;
-#ifdef EOVERFLOW
-    if( pFile->lastErrno==EOVERFLOW ) return SQLITE_NOLFS;
-#endif
-    return SQLITE_IOERR;
-  }
-
-#ifdef __APPLE__
-  /* On OS X on an msdos filesystem, the inode number is reported
-  ** incorrectly for zero-size files.  See ticket #3260.  To work
-  ** around this problem (we consider it a bug in OS X, not SQLite)
-  ** we always increase the file size to 1 by writing a single byte
-  ** prior to accessing the inode number.  The one byte written is
-  ** an ASCII 'S' character which also happens to be the first byte
-  ** in the header of every SQLite database.  In this way, if there
-  ** is a race condition such that another thread has already populated
-  ** the first page of the database, no damage is done.
-  */
-  if( statbuf.st_size==0 && (pFile->fsFlags & SQLITE_FSFLAGS_IS_MSDOS)!=0 ){
-    do{ rc = osWrite(fd, "S", 1); }while( rc<0 && errno==EINTR );
-    if( rc!=1 ){
-      pFile->lastErrno = errno;
-      return SQLITE_IOERR;
-    }
-    rc = osFstat(fd, &statbuf);
-    if( rc!=0 ){
-      pFile->lastErrno = errno;
-      return SQLITE_IOERR;
-    }
-  }
-#endif
-
-  memset(&fileId, 0, sizeof(fileId));
-  fileId.dev = statbuf.st_dev;
-#if OS_VXWORKS
-  fileId.pId = pFile->pId;
-#else
-  fileId.ino = statbuf.st_ino;
-#endif
-  pInode = inodeList;
-  while( pInode && memcmp(&fileId, &pInode->fileId, sizeof(fileId)) ){
-    pInode = pInode->pNext;
-  }
-  if( pInode==0 ){
-    pInode = sqlite3_malloc( sizeof(*pInode) );
-    if( pInode==0 ){
-      return SQLITE_NOMEM;
-    }
-    memset(pInode, 0, sizeof(*pInode));
-    memcpy(&pInode->fileId, &fileId, sizeof(fileId));
-    pInode->nRef = 1;
-    pInode->pNext = inodeList;
-    pInode->pPrev = 0;
-    if( inodeList ) inodeList->pPrev = pInode;
-    inodeList = pInode;
-  }else{
-    pInode->nRef++;
-  }
-  *ppInode = pInode;
-  return SQLITE_OK;
-}
-
-/*
-** Return TRUE if pFile has been renamed or unlinked since it was first opened.
-*/
-static int fileHasMoved(unixFile *pFile){
-#if OS_VXWORKS
-  return pFile->pInode!=0 && pFile->pId!=pFile->pInode->fileId.pId;
-#else
-  struct stat buf;
-  return pFile->pInode!=0 &&
-      (osStat(pFile->zPath, &buf)!=0 || buf.st_ino!=pFile->pInode->fileId.ino);
-#endif
-}
-
-
-/*
-** Check a unixFile that is a database.  Verify the following:
-**
-** (1) There is exactly one hard link on the file
-** (2) The file is not a symbolic link
-** (3) The file has not been renamed or unlinked
-**
-** Issue sqlite3_log(SQLITE_WARNING,...) messages if anything is not right.
-*/
-static void verifyDbFile(unixFile *pFile){
-  struct stat buf;
-  int rc;
-  if( pFile->ctrlFlags & UNIXFILE_WARNED ){
-    /* One or more of the following warnings have already been issued.  Do not
-    ** repeat them so as not to clutter the error log */
-    return;
-  }
-  rc = osFstat(pFile->h, &buf);
-  if( rc!=0 ){
-    sqlite3_log(SQLITE_WARNING, "cannot fstat db file %s", pFile->zPath);
-    pFile->ctrlFlags |= UNIXFILE_WARNED;
-    return;
-  }
-  if( buf.st_nlink==0 && (pFile->ctrlFlags & UNIXFILE_DELETE)==0 ){
-    sqlite3_log(SQLITE_WARNING, "file unlinked while open: %s", pFile->zPath);
-    pFile->ctrlFlags |= UNIXFILE_WARNED;
-    return;
-  }
-  if( buf.st_nlink>1 ){
-    sqlite3_log(SQLITE_WARNING, "multiple links to file: %s", pFile->zPath);
-    pFile->ctrlFlags |= UNIXFILE_WARNED;
-    return;
-  }
-  if( fileHasMoved(pFile) ){
-    sqlite3_log(SQLITE_WARNING, "file renamed while open: %s", pFile->zPath);
-    pFile->ctrlFlags |= UNIXFILE_WARNED;
-    return;
-  }
-}
-
-
-/*
-** This routine checks if there is a RESERVED lock held on the specified
-** file by this or any other process. If such a lock is held, set *pResOut
-** to a non-zero value otherwise *pResOut is set to zero.  The return value
-** is set to SQLITE_OK unless an I/O error occurs during lock checking.
-*/
-static int unixCheckReservedLock(sqlite3_file *id, int *pResOut){
-  int rc = SQLITE_OK;
-  int reserved = 0;
-  unixFile *pFile = (unixFile*)id;
-
-  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
-
-  assert( pFile );
-  unixEnterMutex(); /* Because pFile->pInode is shared across threads */
-
-  /* Check if a thread in this process holds such a lock */
-  if( pFile->pInode->eFileLock>SHARED_LOCK ){
-    reserved = 1;
-  }
-
-  /* Otherwise see if some other process holds it.
-  */
-#ifndef __DJGPP__
-  if( !reserved && !pFile->pInode->bProcessLock ){
-    struct flock lock;
-    lock.l_whence = SEEK_SET;
-    lock.l_start = RESERVED_BYTE;
-    lock.l_len = 1;
-    lock.l_type = F_WRLCK;
-    if( osFcntl(pFile->h, F_GETLK, &lock) ){
-      rc = SQLITE_IOERR_CHECKRESERVEDLOCK;
-      pFile->lastErrno = errno;
-    } else if( lock.l_type!=F_UNLCK ){
-      reserved = 1;
-    }
-  }
-#endif
-  
-  unixLeaveMutex();
-  OSTRACE(("TEST WR-LOCK %d %d %d (unix)\n", pFile->h, rc, reserved));
-
-  *pResOut = reserved;
-  return rc;
-}
-
-/*
-** Attempt to set a system-lock on the file pFile.  The lock is 
-** described by pLock.
-**
-** If the pFile was opened read/write from unix-excl, then the only lock
-** ever obtained is an exclusive lock, and it is obtained exactly once
-** the first time any lock is attempted.  All subsequent system locking
-** operations become no-ops.  Locking operations still happen internally,
-** in order to coordinate access between separate database connections
-** within this process, but all of that is handled in memory and the
-** operating system does not participate.
-**
-** This function is a pass-through to fcntl(F_SETLK) if pFile is using
-** any VFS other than "unix-excl" or if pFile is opened on "unix-excl"
-** and is read-only.
-**
-** Zero is returned if the call completes successfully, or -1 if a call
-** to fcntl() fails. In this case, errno is set appropriately (by fcntl()).
-*/
-static int unixFileLock(unixFile *pFile, struct flock *pLock){
-  int rc;
-  unixInodeInfo *pInode = pFile->pInode;
-  assert( unixMutexHeld() );
-  assert( pInode!=0 );
-  if( ((pFile->ctrlFlags & UNIXFILE_EXCL)!=0 || pInode->bProcessLock)
-   && ((pFile->ctrlFlags & UNIXFILE_RDONLY)==0)
-  ){
-    if( pInode->bProcessLock==0 ){
-      struct flock lock;
-      assert( pInode->nLock==0 );
-      lock.l_whence = SEEK_SET;
-      lock.l_start = SHARED_FIRST;
-      lock.l_len = SHARED_SIZE;
-      lock.l_type = F_WRLCK;
-      rc = osFcntl(pFile->h, F_SETLK, &lock);
-      if( rc<0 ) return rc;
-      pInode->bProcessLock = 1;
-      pInode->nLock++;
-    }else{
-      rc = 0;
-    }
-  }else{
-    rc = osFcntl(pFile->h, F_SETLK, pLock);
-  }
-  return rc;
-}
-
-/*
-** Lock the file with the lock specified by parameter eFileLock - one
-** of the following:
-**
-**     (1) SHARED_LOCK
-**     (2) RESERVED_LOCK
-**     (3) PENDING_LOCK
-**     (4) EXCLUSIVE_LOCK
-**
-** Sometimes when requesting one lock state, additional lock states
-** are inserted in between.  The locking might fail on one of the later
-** transitions leaving the lock state different from what it started but
-** still short of its goal.  The following chart shows the allowed
-** transitions and the inserted intermediate states:
-**
-**    UNLOCKED -> SHARED
-**    SHARED -> RESERVED
-**    SHARED -> (PENDING) -> EXCLUSIVE
-**    RESERVED -> (PENDING) -> EXCLUSIVE
-**    PENDING -> EXCLUSIVE
-**
-** This routine will only increase a lock.  Use the sqlite3OsUnlock()
-** routine to lower a locking level.
-*/
-static int unixLock(sqlite3_file *id, int eFileLock){
-  /* The following describes the implementation of the various locks and
-  ** lock transitions in terms of the POSIX advisory shared and exclusive
-  ** lock primitives (called read-locks and write-locks below, to avoid
-  ** confusion with SQLite lock names). The algorithms are complicated
-  ** slightly in order to be compatible with windows systems simultaneously
-  ** accessing the same database file, in case that is ever required.
-  **
-  ** Symbols defined in os.h indentify the 'pending byte' and the 'reserved
-  ** byte', each single bytes at well known offsets, and the 'shared byte
-  ** range', a range of 510 bytes at a well known offset.
-  **
-  ** To obtain a SHARED lock, a read-lock is obtained on the 'pending
-  ** byte'.  If this is successful, a random byte from the 'shared byte
-  ** range' is read-locked and the lock on the 'pending byte' released.
-  **
-  ** A process may only obtain a RESERVED lock after it has a SHARED lock.
-  ** A RESERVED lock is implemented by grabbing a write-lock on the
-  ** 'reserved byte'. 
-  **
-  ** A process may only obtain a PENDING lock after it has obtained a
-  ** SHARED lock. A PENDING lock is implemented by obtaining a write-lock
-  ** on the 'pending byte'. This ensures that no new SHARED locks can be
-  ** obtained, but existing SHARED locks are allowed to persist. A process
-  ** does not have to obtain a RESERVED lock on the way to a PENDING lock.
-  ** This property is used by the algorithm for rolling back a journal file
-  ** after a crash.
-  **
-  ** An EXCLUSIVE lock, obtained after a PENDING lock is held, is
-  ** implemented by obtaining a write-lock on the entire 'shared byte
-  ** range'. Since all other locks require a read-lock on one of the bytes
-  ** within this range, this ensures that no other locks are held on the
-  ** database. 
-  **
-  ** The reason a single byte cannot be used instead of the 'shared byte
-  ** range' is that some versions of windows do not support read-locks. By
-  ** locking a random byte from a range, concurrent SHARED locks may exist
-  ** even if the locking primitive used is always a write-lock.
-  */
-  int rc = SQLITE_OK;
-  unixFile *pFile = (unixFile*)id;
-  unixInodeInfo *pInode;
-  struct flock lock;
-  int tErrno = 0;
-
-  assert( pFile );
-  OSTRACE(("LOCK    %d %s was %s(%s,%d) pid=%d (unix)\n", pFile->h,
-      azFileLock(eFileLock), azFileLock(pFile->eFileLock),
-      azFileLock(pFile->pInode->eFileLock), pFile->pInode->nShared , getpid()));
-
-  /* If there is already a lock of this type or more restrictive on the
-  ** unixFile, do nothing. Don't use the end_lock: exit path, as
-  ** unixEnterMutex() hasn't been called yet.
-  */
-  if( pFile->eFileLock>=eFileLock ){
-    OSTRACE(("LOCK    %d %s ok (already held) (unix)\n", pFile->h,
-            azFileLock(eFileLock)));
-    return SQLITE_OK;
-  }
-
-  /* Make sure the locking sequence is correct.
-  **  (1) We never move from unlocked to anything higher than shared lock.
-  **  (2) SQLite never explicitly requests a pendig lock.
-  **  (3) A shared lock is always held when a reserve lock is requested.
-  */
-  assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
-  assert( eFileLock!=PENDING_LOCK );
-  assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
-
-  /* This mutex is needed because pFile->pInode is shared across threads
-  */
-  unixEnterMutex();
-  pInode = pFile->pInode;
-
-  /* If some thread using this PID has a lock via a different unixFile*
-  ** handle that precludes the requested lock, return BUSY.
-  */
-  if( (pFile->eFileLock!=pInode->eFileLock && 
-          (pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK))
-  ){
-    rc = SQLITE_BUSY;
-    goto end_lock;
-  }
-
-  /* If a SHARED lock is requested, and some thread using this PID already
-  ** has a SHARED or RESERVED lock, then increment reference counts and
-  ** return SQLITE_OK.
-  */
-  if( eFileLock==SHARED_LOCK && 
-      (pInode->eFileLock==SHARED_LOCK || pInode->eFileLock==RESERVED_LOCK) ){
-    assert( eFileLock==SHARED_LOCK );
-    assert( pFile->eFileLock==0 );
-    assert( pInode->nShared>0 );
-    pFile->eFileLock = SHARED_LOCK;
-    pInode->nShared++;
-    pInode->nLock++;
-    goto end_lock;
-  }
-
-
-  /* A PENDING lock is needed before acquiring a SHARED lock and before
-  ** acquiring an EXCLUSIVE lock.  For the SHARED lock, the PENDING will
-  ** be released.
-  */
-  lock.l_len = 1L;
-  lock.l_whence = SEEK_SET;
-  if( eFileLock==SHARED_LOCK 
-      || (eFileLock==EXCLUSIVE_LOCK && pFile->eFileLock<PENDING_LOCK)
-  ){
-    lock.l_type = (eFileLock==SHARED_LOCK?F_RDLCK:F_WRLCK);
-    lock.l_start = PENDING_BYTE;
-    if( unixFileLock(pFile, &lock) ){
-      tErrno = errno;
-      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
-      if( rc!=SQLITE_BUSY ){
-        pFile->lastErrno = tErrno;
-      }
-      goto end_lock;
-    }
-  }
-
-
-  /* If control gets to this point, then actually go ahead and make
-  ** operating system calls for the specified lock.
-  */
-  if( eFileLock==SHARED_LOCK ){
-    assert( pInode->nShared==0 );
-    assert( pInode->eFileLock==0 );
-    assert( rc==SQLITE_OK );
-
-    /* Now get the read-lock */
-    lock.l_start = SHARED_FIRST;
-    lock.l_len = SHARED_SIZE;
-    if( unixFileLock(pFile, &lock) ){
-      tErrno = errno;
-      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
-    }
-
-    /* Drop the temporary PENDING lock */
-    lock.l_start = PENDING_BYTE;
-    lock.l_len = 1L;
-    lock.l_type = F_UNLCK;
-    if( unixFileLock(pFile, &lock) && rc==SQLITE_OK ){
-      /* This could happen with a network mount */
-      tErrno = errno;
-      rc = SQLITE_IOERR_UNLOCK; 
-    }
-
-    if( rc ){
-      if( rc!=SQLITE_BUSY ){
-        pFile->lastErrno = tErrno;
-      }
-      goto end_lock;
-    }else{
-      pFile->eFileLock = SHARED_LOCK;
-      pInode->nLock++;
-      pInode->nShared = 1;
-    }
-  }else if( eFileLock==EXCLUSIVE_LOCK && pInode->nShared>1 ){
-    /* We are trying for an exclusive lock but another thread in this
-    ** same process is still holding a shared lock. */
-    rc = SQLITE_BUSY;
-  }else{
-    /* The request was for a RESERVED or EXCLUSIVE lock.  It is
-    ** assumed that there is a SHARED or greater lock on the file
-    ** already.
-    */
-    assert( 0!=pFile->eFileLock );
-    lock.l_type = F_WRLCK;
-
-    assert( eFileLock==RESERVED_LOCK || eFileLock==EXCLUSIVE_LOCK );
-    if( eFileLock==RESERVED_LOCK ){
-      lock.l_start = RESERVED_BYTE;
-      lock.l_len = 1L;
-    }else{
-      lock.l_start = SHARED_FIRST;
-      lock.l_len = SHARED_SIZE;
-    }
-
-    if( unixFileLock(pFile, &lock) ){
-      tErrno = errno;
-      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
-      if( rc!=SQLITE_BUSY ){
-        pFile->lastErrno = tErrno;
-      }
-    }
-  }
-  
-
-#ifdef SQLITE_DEBUG
-  /* Set up the transaction-counter change checking flags when
-  ** transitioning from a SHARED to a RESERVED lock.  The change
-  ** from SHARED to RESERVED marks the beginning of a normal
-  ** write operation (not a hot journal rollback).
-  */
-  if( rc==SQLITE_OK
-   && pFile->eFileLock<=SHARED_LOCK
-   && eFileLock==RESERVED_LOCK
-  ){
-    pFile->transCntrChng = 0;
-    pFile->dbUpdate = 0;
-    pFile->inNormalWrite = 1;
-  }
-#endif
-
-
-  if( rc==SQLITE_OK ){
-    pFile->eFileLock = eFileLock;
-    pInode->eFileLock = eFileLock;
-  }else if( eFileLock==EXCLUSIVE_LOCK ){
-    pFile->eFileLock = PENDING_LOCK;
-    pInode->eFileLock = PENDING_LOCK;
-  }
-
-end_lock:
-  unixLeaveMutex();
-  OSTRACE(("LOCK    %d %s %s (unix)\n", pFile->h, azFileLock(eFileLock), 
-      rc==SQLITE_OK ? "ok" : "failed"));
-  return rc;
-}
-
-/*
-** Add the file descriptor used by file handle pFile to the corresponding
-** pUnused list.
-*/
-static void setPendingFd(unixFile *pFile){
-  unixInodeInfo *pInode = pFile->pInode;
-  UnixUnusedFd *p = pFile->pUnused;
-  p->pNext = pInode->pUnused;
-  pInode->pUnused = p;
-  pFile->h = -1;
-  pFile->pUnused = 0;
-}
-
-/*
-** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
-** must be either NO_LOCK or SHARED_LOCK.
-**
-** If the locking level of the file descriptor is already at or below
-** the requested locking level, this routine is a no-op.
-** 
-** If handleNFSUnlock is true, then on downgrading an EXCLUSIVE_LOCK to SHARED
-** the byte range is divided into 2 parts and the first part is unlocked then
-** set to a read lock, then the other part is simply unlocked.  This works 
-** around a bug in BSD NFS lockd (also seen on MacOSX 10.3+) that fails to 
-** remove the write lock on a region when a read lock is set.
-*/
-static int posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
-  unixFile *pFile = (unixFile*)id;
-  unixInodeInfo *pInode;
-  struct flock lock;
-  int rc = SQLITE_OK;
-
-  assert( pFile );
-  OSTRACE(("UNLOCK  %d %d was %d(%d,%d) pid=%d (unix)\n", pFile->h, eFileLock,
-      pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared,
-      getpid()));
-
-  assert( eFileLock<=SHARED_LOCK );
-  if( pFile->eFileLock<=eFileLock ){
-    return SQLITE_OK;
-  }
-  unixEnterMutex();
-  pInode = pFile->pInode;
-  assert( pInode->nShared!=0 );
-  if( pFile->eFileLock>SHARED_LOCK ){
-    assert( pInode->eFileLock==pFile->eFileLock );
-
-#ifdef SQLITE_DEBUG
-    /* When reducing a lock such that other processes can start
-    ** reading the database file again, make sure that the
-    ** transaction counter was updated if any part of the database
-    ** file changed.  If the transaction counter is not updated,
-    ** other connections to the same file might not realize that
-    ** the file has changed and hence might not know to flush their
-    ** cache.  The use of a stale cache can lead to database corruption.
-    */
-    pFile->inNormalWrite = 0;
-#endif
-
-    /* downgrading to a shared lock on NFS involves clearing the write lock
-    ** before establishing the readlock - to avoid a race condition we downgrade
-    ** the lock in 2 blocks, so that part of the range will be covered by a 
-    ** write lock until the rest is covered by a read lock:
-    **  1:   [WWWWW]
-    **  2:   [....W]
-    **  3:   [RRRRW]
-    **  4:   [RRRR.]
-    */
-    if( eFileLock==SHARED_LOCK ){
-
-#if !defined(__APPLE__) || !SQLITE_ENABLE_LOCKING_STYLE
-      (void)handleNFSUnlock;
-      assert( handleNFSUnlock==0 );
-#endif
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-      if( handleNFSUnlock ){
-        int tErrno;               /* Error code from system call errors */
-        off_t divSize = SHARED_SIZE - 1;
-        
-        lock.l_type = F_UNLCK;
-        lock.l_whence = SEEK_SET;
-        lock.l_start = SHARED_FIRST;
-        lock.l_len = divSize;
-        if( unixFileLock(pFile, &lock)==(-1) ){
-          tErrno = errno;
-          rc = SQLITE_IOERR_UNLOCK;
-          if( IS_LOCK_ERROR(rc) ){
-            pFile->lastErrno = tErrno;
-          }
-          goto end_unlock;
-        }
-        lock.l_type = F_RDLCK;
-        lock.l_whence = SEEK_SET;
-        lock.l_start = SHARED_FIRST;
-        lock.l_len = divSize;
-        if( unixFileLock(pFile, &lock)==(-1) ){
-          tErrno = errno;
-          rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_RDLOCK);
-          if( IS_LOCK_ERROR(rc) ){
-            pFile->lastErrno = tErrno;
-          }
-          goto end_unlock;
-        }
-        lock.l_type = F_UNLCK;
-        lock.l_whence = SEEK_SET;
-        lock.l_start = SHARED_FIRST+divSize;
-        lock.l_len = SHARED_SIZE-divSize;
-        if( unixFileLock(pFile, &lock)==(-1) ){
-          tErrno = errno;
-          rc = SQLITE_IOERR_UNLOCK;
-          if( IS_LOCK_ERROR(rc) ){
-            pFile->lastErrno = tErrno;
-          }
-          goto end_unlock;
-        }
-      }else
-#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
-      {
-        lock.l_type = F_RDLCK;
-        lock.l_whence = SEEK_SET;
-        lock.l_start = SHARED_FIRST;
-        lock.l_len = SHARED_SIZE;
-        if( unixFileLock(pFile, &lock) ){
-          /* In theory, the call to unixFileLock() cannot fail because another
-          ** process is holding an incompatible lock. If it does, this 
-          ** indicates that the other process is not following the locking
-          ** protocol. If this happens, return SQLITE_IOERR_RDLOCK. Returning
-          ** SQLITE_BUSY would confuse the upper layer (in practice it causes 
-          ** an assert to fail). */ 
-          rc = SQLITE_IOERR_RDLOCK;
-          pFile->lastErrno = errno;
-          goto end_unlock;
-        }
-      }
-    }
-    lock.l_type = F_UNLCK;
-    lock.l_whence = SEEK_SET;
-    lock.l_start = PENDING_BYTE;
-    lock.l_len = 2L;  assert( PENDING_BYTE+1==RESERVED_BYTE );
-    if( unixFileLock(pFile, &lock)==0 ){
-      pInode->eFileLock = SHARED_LOCK;
-    }else{
-      rc = SQLITE_IOERR_UNLOCK;
-      pFile->lastErrno = errno;
-      goto end_unlock;
-    }
-  }
-  if( eFileLock==NO_LOCK ){
-    /* Decrement the shared lock counter.  Release the lock using an
-    ** OS call only when all threads in this same process have released
-    ** the lock.
-    */
-    pInode->nShared--;
-    if( pInode->nShared==0 ){
-      lock.l_type = F_UNLCK;
-      lock.l_whence = SEEK_SET;
-      lock.l_start = lock.l_len = 0L;
-      if( unixFileLock(pFile, &lock)==0 ){
-        pInode->eFileLock = NO_LOCK;
-      }else{
-        rc = SQLITE_IOERR_UNLOCK;
-        pFile->lastErrno = errno;
-        pInode->eFileLock = NO_LOCK;
-        pFile->eFileLock = NO_LOCK;
-      }
-    }
-
-    /* Decrement the count of locks against this same file.  When the
-    ** count reaches zero, close any other file descriptors whose close
-    ** was deferred because of outstanding locks.
-    */
-    pInode->nLock--;
-    assert( pInode->nLock>=0 );
-    if( pInode->nLock==0 ){
-      closePendingFds(pFile);
-    }
-  }
-
-end_unlock:
-  unixLeaveMutex();
-  if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock;
-  return rc;
-}
-
-/*
-** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
-** must be either NO_LOCK or SHARED_LOCK.
-**
-** If the locking level of the file descriptor is already at or below
-** the requested locking level, this routine is a no-op.
-*/
-static int unixUnlock(sqlite3_file *id, int eFileLock){
-#if SQLITE_MAX_MMAP_SIZE>0
-  assert( eFileLock==SHARED_LOCK || ((unixFile *)id)->nFetchOut==0 );
-#endif
-  return posixUnlock(id, eFileLock, 0);
-}
-
-#if SQLITE_MAX_MMAP_SIZE>0
-static int unixMapfile(unixFile *pFd, i64 nByte);
-static void unixUnmapfile(unixFile *pFd);
-#endif
-
-/*
-** This function performs the parts of the "close file" operation 
-** common to all locking schemes. It closes the directory and file
-** handles, if they are valid, and sets all fields of the unixFile
-** structure to 0.
-**
-** It is *not* necessary to hold the mutex when this routine is called,
-** even on VxWorks.  A mutex will be acquired on VxWorks by the
-** vxworksReleaseFileId() routine.
-*/
-static int closeUnixFile(sqlite3_file *id){
-  unixFile *pFile = (unixFile*)id;
-#if SQLITE_MAX_MMAP_SIZE>0
-  unixUnmapfile(pFile);
-#endif
-  if( pFile->h>=0 ){
-    robust_close(pFile, pFile->h, __LINE__);
-    pFile->h = -1;
-  }
-#if OS_VXWORKS
-  if( pFile->pId ){
-    if( pFile->ctrlFlags & UNIXFILE_DELETE ){
-      osUnlink(pFile->pId->zCanonicalName);
-    }
-    vxworksReleaseFileId(pFile->pId);
-    pFile->pId = 0;
-  }
-#endif
-#ifdef SQLITE_UNLINK_AFTER_CLOSE
-  if( pFile->ctrlFlags & UNIXFILE_DELETE ){
-    osUnlink(pFile->zPath);
-    sqlite3_free(*(char**)&pFile->zPath);
-    pFile->zPath = 0;
-  }
-#endif
-  OSTRACE(("CLOSE   %-3d\n", pFile->h));
-  OpenCounter(-1);
-  sqlite3_free(pFile->pUnused);
-  memset(pFile, 0, sizeof(unixFile));
-  return SQLITE_OK;
-}
-
-/*
-** Close a file.
-*/
-static int unixClose(sqlite3_file *id){
-  int rc = SQLITE_OK;
-  unixFile *pFile = (unixFile *)id;
-  verifyDbFile(pFile);
-  unixUnlock(id, NO_LOCK);
-  unixEnterMutex();
-
-  /* unixFile.pInode is always valid here. Otherwise, a different close
-  ** routine (e.g. nolockClose()) would be called instead.
-  */
-  assert( pFile->pInode->nLock>0 || pFile->pInode->bProcessLock==0 );
-  if( ALWAYS(pFile->pInode) && pFile->pInode->nLock ){
-    /* If there are outstanding locks, do not actually close the file just
-    ** yet because that would clear those locks.  Instead, add the file
-    ** descriptor to pInode->pUnused list.  It will be automatically closed 
-    ** when the last lock is cleared.
-    */
-    setPendingFd(pFile);
-  }
-  releaseInodeInfo(pFile);
-  rc = closeUnixFile(id);
-  unixLeaveMutex();
-  return rc;
-}
-
-/************** End of the posix advisory lock implementation *****************
-******************************************************************************/
-
-/******************************************************************************
-****************************** No-op Locking **********************************
-**
-** Of the various locking implementations available, this is by far the
-** simplest:  locking is ignored.  No attempt is made to lock the database
-** file for reading or writing.
-**
-** This locking mode is appropriate for use on read-only databases
-** (ex: databases that are burned into CD-ROM, for example.)  It can
-** also be used if the application employs some external mechanism to
-** prevent simultaneous access of the same database by two or more
-** database connections.  But there is a serious risk of database
-** corruption if this locking mode is used in situations where multiple
-** database connections are accessing the same database file at the same
-** time and one or more of those connections are writing.
-*/
-
-static int nolockCheckReservedLock(sqlite3_file *NotUsed, int *pResOut){
-  UNUSED_PARAMETER(NotUsed);
-  *pResOut = 0;
-  return SQLITE_OK;
-}
-static int nolockLock(sqlite3_file *NotUsed, int NotUsed2){
-  UNUSED_PARAMETER2(NotUsed, NotUsed2);
-  return SQLITE_OK;
-}
-static int nolockUnlock(sqlite3_file *NotUsed, int NotUsed2){
-  UNUSED_PARAMETER2(NotUsed, NotUsed2);
-  return SQLITE_OK;
-}
-
-/*
-** Close the file.
-*/
-static int nolockClose(sqlite3_file *id) {
-  return closeUnixFile(id);
-}
-
-/******************* End of the no-op lock implementation *********************
-******************************************************************************/
-
-/******************************************************************************
-************************* Begin dot-file Locking ******************************
-**
-** The dotfile locking implementation uses the existence of separate lock
-** files (really a directory) to control access to the database.  This works
-** on just about every filesystem imaginable.  But there are serious downsides:
-**
-**    (1)  There is zero concurrency.  A single reader blocks all other
-**         connections from reading or writing the database.
-**
-**    (2)  An application crash or power loss can leave stale lock files
-**         sitting around that need to be cleared manually.
-**
-** Nevertheless, a dotlock is an appropriate locking mode for use if no
-** other locking strategy is available.
-**
-** Dotfile locking works by creating a subdirectory in the same directory as
-** the database and with the same name but with a ".lock" extension added.
-** The existence of a lock directory implies an EXCLUSIVE lock.  All other
-** lock types (SHARED, RESERVED, PENDING) are mapped into EXCLUSIVE.
-*/
-
-/*
-** The file suffix added to the data base filename in order to create the
-** lock directory.
-*/
-#define DOTLOCK_SUFFIX ".lock"
-
-/*
-** This routine checks if there is a RESERVED lock held on the specified
-** file by this or any other process. If such a lock is held, set *pResOut
-** to a non-zero value otherwise *pResOut is set to zero.  The return value
-** is set to SQLITE_OK unless an I/O error occurs during lock checking.
-**
-** In dotfile locking, either a lock exists or it does not.  So in this
-** variation of CheckReservedLock(), *pResOut is set to true if any lock
-** is held on the file and false if the file is unlocked.
-*/
-static int dotlockCheckReservedLock(sqlite3_file *id, int *pResOut) {
-  int rc = SQLITE_OK;
-  int reserved = 0;
-  unixFile *pFile = (unixFile*)id;
-
-  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
-  
-  assert( pFile );
-
-  /* Check if a thread in this process holds such a lock */
-  if( pFile->eFileLock>SHARED_LOCK ){
-    /* Either this connection or some other connection in the same process
-    ** holds a lock on the file.  No need to check further. */
-    reserved = 1;
-  }else{
-    /* The lock is held if and only if the lockfile exists */
-    const char *zLockFile = (const char*)pFile->lockingContext;
-    reserved = osAccess(zLockFile, 0)==0;
-  }
-  OSTRACE(("TEST WR-LOCK %d %d %d (dotlock)\n", pFile->h, rc, reserved));
-  *pResOut = reserved;
-  return rc;
-}
-
-/*
-** Lock the file with the lock specified by parameter eFileLock - one
-** of the following:
-**
-**     (1) SHARED_LOCK
-**     (2) RESERVED_LOCK
-**     (3) PENDING_LOCK
-**     (4) EXCLUSIVE_LOCK
-**
-** Sometimes when requesting one lock state, additional lock states
-** are inserted in between.  The locking might fail on one of the later
-** transitions leaving the lock state different from what it started but
-** still short of its goal.  The following chart shows the allowed
-** transitions and the inserted intermediate states:
-**
-**    UNLOCKED -> SHARED
-**    SHARED -> RESERVED
-**    SHARED -> (PENDING) -> EXCLUSIVE
-**    RESERVED -> (PENDING) -> EXCLUSIVE
-**    PENDING -> EXCLUSIVE
-**
-** This routine will only increase a lock.  Use the sqlite3OsUnlock()
-** routine to lower a locking level.
-**
-** With dotfile locking, we really only support state (4): EXCLUSIVE.
-** But we track the other locking levels internally.
-*/
-static int dotlockLock(sqlite3_file *id, int eFileLock) {
-  unixFile *pFile = (unixFile*)id;
-  char *zLockFile = (char *)pFile->lockingContext;
-  int rc = SQLITE_OK;
-
-
-  /* If we have any lock, then the lock file already exists.  All we have
-  ** to do is adjust our internal record of the lock level.
-  */
-  if( pFile->eFileLock > NO_LOCK ){
-    pFile->eFileLock = eFileLock;
-    /* Always update the timestamp on the old file */
-#ifdef HAVE_UTIME
-    utime(zLockFile, NULL);
-#else
-    utimes(zLockFile, NULL);
-#endif
-    return SQLITE_OK;
-  }
-  
-  /* grab an exclusive lock */
-  rc = osMkdir(zLockFile, 0777);
-  if( rc<0 ){
-    /* failed to open/create the lock directory */
-    int tErrno = errno;
-    if( EEXIST == tErrno ){
-      rc = SQLITE_BUSY;
-    } else {
-      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
-      if( IS_LOCK_ERROR(rc) ){
-        pFile->lastErrno = tErrno;
-      }
-    }
-    return rc;
-  } 
-  
-  /* got it, set the type and return ok */
-  pFile->eFileLock = eFileLock;
-  return rc;
-}
-
-/*
-** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
-** must be either NO_LOCK or SHARED_LOCK.
-**
-** If the locking level of the file descriptor is already at or below
-** the requested locking level, this routine is a no-op.
-**
-** When the locking level reaches NO_LOCK, delete the lock file.
-*/
-static int dotlockUnlock(sqlite3_file *id, int eFileLock) {
-  unixFile *pFile = (unixFile*)id;
-  char *zLockFile = (char *)pFile->lockingContext;
-  int rc;
-
-  assert( pFile );
-  OSTRACE(("UNLOCK  %d %d was %d pid=%d (dotlock)\n", pFile->h, eFileLock,
-           pFile->eFileLock, getpid()));
-  assert( eFileLock<=SHARED_LOCK );
-  
-  /* no-op if possible */
-  if( pFile->eFileLock==eFileLock ){
-    return SQLITE_OK;
-  }
-
-  /* To downgrade to shared, simply update our internal notion of the
-  ** lock state.  No need to mess with the file on disk.
-  */
-  if( eFileLock==SHARED_LOCK ){
-    pFile->eFileLock = SHARED_LOCK;
-    return SQLITE_OK;
-  }
-  
-  /* To fully unlock the database, delete the lock file */
-  assert( eFileLock==NO_LOCK );
-  rc = osRmdir(zLockFile);
-  if( rc<0 && errno==ENOTDIR ) rc = osUnlink(zLockFile);
-  if( rc<0 ){
-    int tErrno = errno;
-    rc = 0;
-    if( ENOENT != tErrno ){
-      rc = SQLITE_IOERR_UNLOCK;
-    }
-    if( IS_LOCK_ERROR(rc) ){
-      pFile->lastErrno = tErrno;
-    }
-    return rc; 
-  }
-  pFile->eFileLock = NO_LOCK;
-  return SQLITE_OK;
-}
-
-/*
-** Close a file.  Make sure the lock has been released before closing.
-*/
-static int dotlockClose(sqlite3_file *id) {
-  int rc = SQLITE_OK;
-  if( id ){
-    unixFile *pFile = (unixFile*)id;
-    dotlockUnlock(id, NO_LOCK);
-    sqlite3_free(pFile->lockingContext);
-    rc = closeUnixFile(id);
-  }
-  return rc;
-}
-/****************** End of the dot-file lock implementation *******************
-******************************************************************************/
-
-/******************************************************************************
-************************** Begin flock Locking ********************************
-**
-** Use the flock() system call to do file locking.
-**
-** flock() locking is like dot-file locking in that the various
-** fine-grain locking levels supported by SQLite are collapsed into
-** a single exclusive lock.  In other words, SHARED, RESERVED, and
-** PENDING locks are the same thing as an EXCLUSIVE lock.  SQLite
-** still works when you do this, but concurrency is reduced since
-** only a single process can be reading the database at a time.
-**
-** Omit this section if SQLITE_ENABLE_LOCKING_STYLE is turned off or if
-** compiling for VXWORKS.
-*/
-#if SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS
-
-/*
-** Retry flock() calls that fail with EINTR
-*/
-#ifdef EINTR
-static int robust_flock(int fd, int op){
-  int rc;
-  do{ rc = flock(fd,op); }while( rc<0 && errno==EINTR );
-  return rc;
-}
-#else
-# define robust_flock(a,b) flock(a,b)
-#endif
-     
-
-/*
-** This routine checks if there is a RESERVED lock held on the specified
-** file by this or any other process. If such a lock is held, set *pResOut
-** to a non-zero value otherwise *pResOut is set to zero.  The return value
-** is set to SQLITE_OK unless an I/O error occurs during lock checking.
-*/
-static int flockCheckReservedLock(sqlite3_file *id, int *pResOut){
-  int rc = SQLITE_OK;
-  int reserved = 0;
-  unixFile *pFile = (unixFile*)id;
-  
-  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
-  
-  assert( pFile );
-  
-  /* Check if a thread in this process holds such a lock */
-  if( pFile->eFileLock>SHARED_LOCK ){
-    reserved = 1;
-  }
-  
-  /* Otherwise see if some other process holds it. */
-  if( !reserved ){
-    /* attempt to get the lock */
-    int lrc = robust_flock(pFile->h, LOCK_EX | LOCK_NB);
-    if( !lrc ){
-      /* got the lock, unlock it */
-      lrc = robust_flock(pFile->h, LOCK_UN);
-      if ( lrc ) {
-        int tErrno = errno;
-        /* unlock failed with an error */
-        lrc = SQLITE_IOERR_UNLOCK; 
-        if( IS_LOCK_ERROR(lrc) ){
-          pFile->lastErrno = tErrno;
-          rc = lrc;
-        }
-      }
-    } else {
-      int tErrno = errno;
-      reserved = 1;
-      /* someone else might have it reserved */
-      lrc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK); 
-      if( IS_LOCK_ERROR(lrc) ){
-        pFile->lastErrno = tErrno;
-        rc = lrc;
-      }
-    }
-  }
-  OSTRACE(("TEST WR-LOCK %d %d %d (flock)\n", pFile->h, rc, reserved));
-
-#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
-  if( (rc & SQLITE_IOERR) == SQLITE_IOERR ){
-    rc = SQLITE_OK;
-    reserved=1;
-  }
-#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
-  *pResOut = reserved;
-  return rc;
-}
-
-/*
-** Lock the file with the lock specified by parameter eFileLock - one
-** of the following:
-**
-**     (1) SHARED_LOCK
-**     (2) RESERVED_LOCK
-**     (3) PENDING_LOCK
-**     (4) EXCLUSIVE_LOCK
-**
-** Sometimes when requesting one lock state, additional lock states
-** are inserted in between.  The locking might fail on one of the later
-** transitions leaving the lock state different from what it started but
-** still short of its goal.  The following chart shows the allowed
-** transitions and the inserted intermediate states:
-**
-**    UNLOCKED -> SHARED
-**    SHARED -> RESERVED
-**    SHARED -> (PENDING) -> EXCLUSIVE
-**    RESERVED -> (PENDING) -> EXCLUSIVE
-**    PENDING -> EXCLUSIVE
-**
-** flock() only really support EXCLUSIVE locks.  We track intermediate
-** lock states in the sqlite3_file structure, but all locks SHARED or
-** above are really EXCLUSIVE locks and exclude all other processes from
-** access the file.
-**
-** This routine will only increase a lock.  Use the sqlite3OsUnlock()
-** routine to lower a locking level.
-*/
-static int flockLock(sqlite3_file *id, int eFileLock) {
-  int rc = SQLITE_OK;
-  unixFile *pFile = (unixFile*)id;
-
-  assert( pFile );
-
-  /* if we already have a lock, it is exclusive.  
-  ** Just adjust level and punt on outta here. */
-  if (pFile->eFileLock > NO_LOCK) {
-    pFile->eFileLock = eFileLock;
-    return SQLITE_OK;
-  }
-  
-  /* grab an exclusive lock */
-  
-  if (robust_flock(pFile->h, LOCK_EX | LOCK_NB)) {
-    int tErrno = errno;
-    /* didn't get, must be busy */
-    rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
-    if( IS_LOCK_ERROR(rc) ){
-      pFile->lastErrno = tErrno;
-    }
-  } else {
-    /* got it, set the type and return ok */
-    pFile->eFileLock = eFileLock;
-  }
-  OSTRACE(("LOCK    %d %s %s (flock)\n", pFile->h, azFileLock(eFileLock), 
-           rc==SQLITE_OK ? "ok" : "failed"));
-#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
-  if( (rc & SQLITE_IOERR) == SQLITE_IOERR ){
-    rc = SQLITE_BUSY;
-  }
-#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
-  return rc;
-}
-
-
-/*
-** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
-** must be either NO_LOCK or SHARED_LOCK.
-**
-** If the locking level of the file descriptor is already at or below
-** the requested locking level, this routine is a no-op.
-*/
-static int flockUnlock(sqlite3_file *id, int eFileLock) {
-  unixFile *pFile = (unixFile*)id;
-  
-  assert( pFile );
-  OSTRACE(("UNLOCK  %d %d was %d pid=%d (flock)\n", pFile->h, eFileLock,
-           pFile->eFileLock, getpid()));
-  assert( eFileLock<=SHARED_LOCK );
-  
-  /* no-op if possible */
-  if( pFile->eFileLock==eFileLock ){
-    return SQLITE_OK;
-  }
-  
-  /* shared can just be set because we always have an exclusive */
-  if (eFileLock==SHARED_LOCK) {
-    pFile->eFileLock = eFileLock;
-    return SQLITE_OK;
-  }
-  
-  /* no, really, unlock. */
-  if( robust_flock(pFile->h, LOCK_UN) ){
-#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
-    return SQLITE_OK;
-#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
-    return SQLITE_IOERR_UNLOCK;
-  }else{
-    pFile->eFileLock = NO_LOCK;
-    return SQLITE_OK;
-  }
-}
-
-/*
-** Close a file.
-*/
-static int flockClose(sqlite3_file *id) {
-  int rc = SQLITE_OK;
-  if( id ){
-    flockUnlock(id, NO_LOCK);
-    rc = closeUnixFile(id);
-  }
-  return rc;
-}
-
-#endif /* SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORK */
-
-/******************* End of the flock lock implementation *********************
-******************************************************************************/
-
-/******************************************************************************
-************************ Begin Named Semaphore Locking ************************
-**
-** Named semaphore locking is only supported on VxWorks.
-**
-** Semaphore locking is like dot-lock and flock in that it really only
-** supports EXCLUSIVE locking.  Only a single process can read or write
-** the database file at a time.  This reduces potential concurrency, but
-** makes the lock implementation much easier.
-*/
-#if OS_VXWORKS
-
-/*
-** This routine checks if there is a RESERVED lock held on the specified
-** file by this or any other process. If such a lock is held, set *pResOut
-** to a non-zero value otherwise *pResOut is set to zero.  The return value
-** is set to SQLITE_OK unless an I/O error occurs during lock checking.
-*/
-static int semCheckReservedLock(sqlite3_file *id, int *pResOut) {
-  int rc = SQLITE_OK;
-  int reserved = 0;
-  unixFile *pFile = (unixFile*)id;
-
-  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
-  
-  assert( pFile );
-
-  /* Check if a thread in this process holds such a lock */
-  if( pFile->eFileLock>SHARED_LOCK ){
-    reserved = 1;
-  }
-  
-  /* Otherwise see if some other process holds it. */
-  if( !reserved ){
-    sem_t *pSem = pFile->pInode->pSem;
-
-    if( sem_trywait(pSem)==-1 ){
-      int tErrno = errno;
-      if( EAGAIN != tErrno ){
-        rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_CHECKRESERVEDLOCK);
-        pFile->lastErrno = tErrno;
-      } else {
-        /* someone else has the lock when we are in NO_LOCK */
-        reserved = (pFile->eFileLock < SHARED_LOCK);
-      }
-    }else{
-      /* we could have it if we want it */
-      sem_post(pSem);
-    }
-  }
-  OSTRACE(("TEST WR-LOCK %d %d %d (sem)\n", pFile->h, rc, reserved));
-
-  *pResOut = reserved;
-  return rc;
-}
-
-/*
-** Lock the file with the lock specified by parameter eFileLock - one
-** of the following:
-**
-**     (1) SHARED_LOCK
-**     (2) RESERVED_LOCK
-**     (3) PENDING_LOCK
-**     (4) EXCLUSIVE_LOCK
-**
-** Sometimes when requesting one lock state, additional lock states
-** are inserted in between.  The locking might fail on one of the later
-** transitions leaving the lock state different from what it started but
-** still short of its goal.  The following chart shows the allowed
-** transitions and the inserted intermediate states:
-**
-**    UNLOCKED -> SHARED
-**    SHARED -> RESERVED
-**    SHARED -> (PENDING) -> EXCLUSIVE
-**    RESERVED -> (PENDING) -> EXCLUSIVE
-**    PENDING -> EXCLUSIVE
-**
-** Semaphore locks only really support EXCLUSIVE locks.  We track intermediate
-** lock states in the sqlite3_file structure, but all locks SHARED or
-** above are really EXCLUSIVE locks and exclude all other processes from
-** access the file.
-**
-** This routine will only increase a lock.  Use the sqlite3OsUnlock()
-** routine to lower a locking level.
-*/
-static int semLock(sqlite3_file *id, int eFileLock) {
-  unixFile *pFile = (unixFile*)id;
-  sem_t *pSem = pFile->pInode->pSem;
-  int rc = SQLITE_OK;
-
-  /* if we already have a lock, it is exclusive.  
-  ** Just adjust level and punt on outta here. */
-  if (pFile->eFileLock > NO_LOCK) {
-    pFile->eFileLock = eFileLock;
-    rc = SQLITE_OK;
-    goto sem_end_lock;
-  }
-  
-  /* lock semaphore now but bail out when already locked. */
-  if( sem_trywait(pSem)==-1 ){
-    rc = SQLITE_BUSY;
-    goto sem_end_lock;
-  }
-
-  /* got it, set the type and return ok */
-  pFile->eFileLock = eFileLock;
-
- sem_end_lock:
-  return rc;
-}
-
-/*
-** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
-** must be either NO_LOCK or SHARED_LOCK.
-**
-** If the locking level of the file descriptor is already at or below
-** the requested locking level, this routine is a no-op.
-*/
-static int semUnlock(sqlite3_file *id, int eFileLock) {
-  unixFile *pFile = (unixFile*)id;
-  sem_t *pSem = pFile->pInode->pSem;
-
-  assert( pFile );
-  assert( pSem );
-  OSTRACE(("UNLOCK  %d %d was %d pid=%d (sem)\n", pFile->h, eFileLock,
-           pFile->eFileLock, getpid()));
-  assert( eFileLock<=SHARED_LOCK );
-  
-  /* no-op if possible */
-  if( pFile->eFileLock==eFileLock ){
-    return SQLITE_OK;
-  }
-  
-  /* shared can just be set because we always have an exclusive */
-  if (eFileLock==SHARED_LOCK) {
-    pFile->eFileLock = eFileLock;
-    return SQLITE_OK;
-  }
-  
-  /* no, really unlock. */
-  if ( sem_post(pSem)==-1 ) {
-    int rc, tErrno = errno;
-    rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
-    if( IS_LOCK_ERROR(rc) ){
-      pFile->lastErrno = tErrno;
-    }
-    return rc; 
-  }
-  pFile->eFileLock = NO_LOCK;
-  return SQLITE_OK;
-}
-
-/*
- ** Close a file.
- */
-static int semClose(sqlite3_file *id) {
-  if( id ){
-    unixFile *pFile = (unixFile*)id;
-    semUnlock(id, NO_LOCK);
-    assert( pFile );
-    unixEnterMutex();
-    releaseInodeInfo(pFile);
-    unixLeaveMutex();
-    closeUnixFile(id);
-  }
-  return SQLITE_OK;
-}
-
-#endif /* OS_VXWORKS */
-/*
-** Named semaphore locking is only available on VxWorks.
-**
-*************** End of the named semaphore lock implementation ****************
-******************************************************************************/
-
-
-/******************************************************************************
-*************************** Begin AFP Locking *********************************
-**
-** AFP is the Apple Filing Protocol.  AFP is a network filesystem found
-** on Apple Macintosh computers - both OS9 and OSX.
-**
-** Third-party implementations of AFP are available.  But this code here
-** only works on OSX.
-*/
-
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-/*
-** The afpLockingContext structure contains all afp lock specific state
-*/
-typedef struct afpLockingContext afpLockingContext;
-struct afpLockingContext {
-  int reserved;
-  const char *dbPath;             /* Name of the open file */
-};
-
-struct ByteRangeLockPB2
-{
-  unsigned long long offset;        /* offset to first byte to lock */
-  unsigned long long length;        /* nbr of bytes to lock */
-  unsigned long long retRangeStart; /* nbr of 1st byte locked if successful */
-  unsigned char unLockFlag;         /* 1 = unlock, 0 = lock */
-  unsigned char startEndFlag;       /* 1=rel to end of fork, 0=rel to start */
-  int fd;                           /* file desc to assoc this lock with */
-};
-
-#define afpfsByteRangeLock2FSCTL        _IOWR('z', 23, struct ByteRangeLockPB2)
-
-/*
-** This is a utility for setting or clearing a bit-range lock on an
-** AFP filesystem.
-** 
-** Return SQLITE_OK on success, SQLITE_BUSY on failure.
-*/
-static int afpSetLock(
-  const char *path,              /* Name of the file to be locked or unlocked */
-  unixFile *pFile,               /* Open file descriptor on path */
-  unsigned long long offset,     /* First byte to be locked */
-  unsigned long long length,     /* Number of bytes to lock */
-  int setLockFlag                /* True to set lock.  False to clear lock */
-){
-  struct ByteRangeLockPB2 pb;
-  int err;
-  
-  pb.unLockFlag = setLockFlag ? 0 : 1;
-  pb.startEndFlag = 0;
-  pb.offset = offset;
-  pb.length = length; 
-  pb.fd = pFile->h;
-  
-  OSTRACE(("AFPSETLOCK [%s] for %d%s in range %llx:%llx\n", 
-    (setLockFlag?"ON":"OFF"), pFile->h, (pb.fd==-1?"[testval-1]":""),
-    offset, length));
-  err = fsctl(path, afpfsByteRangeLock2FSCTL, &pb, 0);
-  if ( err==-1 ) {
-    int rc;
-    int tErrno = errno;
-    OSTRACE(("AFPSETLOCK failed to fsctl() '%s' %d %s\n",
-             path, tErrno, strerror(tErrno)));
-#ifdef SQLITE_IGNORE_AFP_LOCK_ERRORS
-    rc = SQLITE_BUSY;
-#else
-    rc = sqliteErrorFromPosixError(tErrno,
-                    setLockFlag ? SQLITE_IOERR_LOCK : SQLITE_IOERR_UNLOCK);
-#endif /* SQLITE_IGNORE_AFP_LOCK_ERRORS */
-    if( IS_LOCK_ERROR(rc) ){
-      pFile->lastErrno = tErrno;
-    }
-    return rc;
-  } else {
-    return SQLITE_OK;
-  }
-}
-
-/*
-** This routine checks if there is a RESERVED lock held on the specified
-** file by this or any other process. If such a lock is held, set *pResOut
-** to a non-zero value otherwise *pResOut is set to zero.  The return value
-** is set to SQLITE_OK unless an I/O error occurs during lock checking.
-*/
-static int afpCheckReservedLock(sqlite3_file *id, int *pResOut){
-  int rc = SQLITE_OK;
-  int reserved = 0;
-  unixFile *pFile = (unixFile*)id;
-  afpLockingContext *context;
-  
-  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
-  
-  assert( pFile );
-  context = (afpLockingContext *) pFile->lockingContext;
-  if( context->reserved ){
-    *pResOut = 1;
-    return SQLITE_OK;
-  }
-  unixEnterMutex(); /* Because pFile->pInode is shared across threads */
-  
-  /* Check if a thread in this process holds such a lock */
-  if( pFile->pInode->eFileLock>SHARED_LOCK ){
-    reserved = 1;
-  }
-  
-  /* Otherwise see if some other process holds it.
-   */
-  if( !reserved ){
-    /* lock the RESERVED byte */
-    int lrc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1,1);  
-    if( SQLITE_OK==lrc ){
-      /* if we succeeded in taking the reserved lock, unlock it to restore
-      ** the original state */
-      lrc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1, 0);
-    } else {
-      /* if we failed to get the lock then someone else must have it */
-      reserved = 1;
-    }
-    if( IS_LOCK_ERROR(lrc) ){
-      rc=lrc;
-    }
-  }
-  
-  unixLeaveMutex();
-  OSTRACE(("TEST WR-LOCK %d %d %d (afp)\n", pFile->h, rc, reserved));
-  
-  *pResOut = reserved;
-  return rc;
-}
-
-/*
-** Lock the file with the lock specified by parameter eFileLock - one
-** of the following:
-**
-**     (1) SHARED_LOCK
-**     (2) RESERVED_LOCK
-**     (3) PENDING_LOCK
-**     (4) EXCLUSIVE_LOCK
-**
-** Sometimes when requesting one lock state, additional lock states
-** are inserted in between.  The locking might fail on one of the later
-** transitions leaving the lock state different from what it started but
-** still short of its goal.  The following chart shows the allowed
-** transitions and the inserted intermediate states:
-**
-**    UNLOCKED -> SHARED
-**    SHARED -> RESERVED
-**    SHARED -> (PENDING) -> EXCLUSIVE
-**    RESERVED -> (PENDING) -> EXCLUSIVE
-**    PENDING -> EXCLUSIVE
-**
-** This routine will only increase a lock.  Use the sqlite3OsUnlock()
-** routine to lower a locking level.
-*/
-static int afpLock(sqlite3_file *id, int eFileLock){
-  int rc = SQLITE_OK;
-  unixFile *pFile = (unixFile*)id;
-  unixInodeInfo *pInode = pFile->pInode;
-  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
-  
-  assert( pFile );
-  OSTRACE(("LOCK    %d %s was %s(%s,%d) pid=%d (afp)\n", pFile->h,
-           azFileLock(eFileLock), azFileLock(pFile->eFileLock),
-           azFileLock(pInode->eFileLock), pInode->nShared , getpid()));
-
-  /* If there is already a lock of this type or more restrictive on the
-  ** unixFile, do nothing. Don't use the afp_end_lock: exit path, as
-  ** unixEnterMutex() hasn't been called yet.
-  */
-  if( pFile->eFileLock>=eFileLock ){
-    OSTRACE(("LOCK    %d %s ok (already held) (afp)\n", pFile->h,
-           azFileLock(eFileLock)));
-    return SQLITE_OK;
-  }
-
-  /* Make sure the locking sequence is correct
-  **  (1) We never move from unlocked to anything higher than shared lock.
-  **  (2) SQLite never explicitly requests a pendig lock.
-  **  (3) A shared lock is always held when a reserve lock is requested.
-  */
-  assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
-  assert( eFileLock!=PENDING_LOCK );
-  assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
-  
-  /* This mutex is needed because pFile->pInode is shared across threads
-  */
-  unixEnterMutex();
-  pInode = pFile->pInode;
-
-  /* If some thread using this PID has a lock via a different unixFile*
-  ** handle that precludes the requested lock, return BUSY.
-  */
-  if( (pFile->eFileLock!=pInode->eFileLock && 
-       (pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK))
-     ){
-    rc = SQLITE_BUSY;
-    goto afp_end_lock;
-  }
-  
-  /* If a SHARED lock is requested, and some thread using this PID already
-  ** has a SHARED or RESERVED lock, then increment reference counts and
-  ** return SQLITE_OK.
-  */
-  if( eFileLock==SHARED_LOCK && 
-     (pInode->eFileLock==SHARED_LOCK || pInode->eFileLock==RESERVED_LOCK) ){
-    assert( eFileLock==SHARED_LOCK );
-    assert( pFile->eFileLock==0 );
-    assert( pInode->nShared>0 );
-    pFile->eFileLock = SHARED_LOCK;
-    pInode->nShared++;
-    pInode->nLock++;
-    goto afp_end_lock;
-  }
-    
-  /* A PENDING lock is needed before acquiring a SHARED lock and before
-  ** acquiring an EXCLUSIVE lock.  For the SHARED lock, the PENDING will
-  ** be released.
-  */
-  if( eFileLock==SHARED_LOCK 
-      || (eFileLock==EXCLUSIVE_LOCK && pFile->eFileLock<PENDING_LOCK)
-  ){
-    int failed;
-    failed = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 1);
-    if (failed) {
-      rc = failed;
-      goto afp_end_lock;
-    }
-  }
-  
-  /* If control gets to this point, then actually go ahead and make
-  ** operating system calls for the specified lock.
-  */
-  if( eFileLock==SHARED_LOCK ){
-    int lrc1, lrc2, lrc1Errno = 0;
-    long lk, mask;
-    
-    assert( pInode->nShared==0 );
-    assert( pInode->eFileLock==0 );
-        
-    mask = (sizeof(long)==8) ? LARGEST_INT64 : 0x7fffffff;
-    /* Now get the read-lock SHARED_LOCK */
-    /* note that the quality of the randomness doesn't matter that much */
-    lk = random(); 
-    pInode->sharedByte = (lk & mask)%(SHARED_SIZE - 1);
-    lrc1 = afpSetLock(context->dbPath, pFile, 
-          SHARED_FIRST+pInode->sharedByte, 1, 1);
-    if( IS_LOCK_ERROR(lrc1) ){
-      lrc1Errno = pFile->lastErrno;
-    }
-    /* Drop the temporary PENDING lock */
-    lrc2 = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 0);
-    
-    if( IS_LOCK_ERROR(lrc1) ) {
-      pFile->lastErrno = lrc1Errno;
-      rc = lrc1;
-      goto afp_end_lock;
-    } else if( IS_LOCK_ERROR(lrc2) ){
-      rc = lrc2;
-      goto afp_end_lock;
-    } else if( lrc1 != SQLITE_OK ) {
-      rc = lrc1;
-    } else {
-      pFile->eFileLock = SHARED_LOCK;
-      pInode->nLock++;
-      pInode->nShared = 1;
-    }
-  }else if( eFileLock==EXCLUSIVE_LOCK && pInode->nShared>1 ){
-    /* We are trying for an exclusive lock but another thread in this
-     ** same process is still holding a shared lock. */
-    rc = SQLITE_BUSY;
-  }else{
-    /* The request was for a RESERVED or EXCLUSIVE lock.  It is
-    ** assumed that there is a SHARED or greater lock on the file
-    ** already.
-    */
-    int failed = 0;
-    assert( 0!=pFile->eFileLock );
-    if (eFileLock >= RESERVED_LOCK && pFile->eFileLock < RESERVED_LOCK) {
-        /* Acquire a RESERVED lock */
-        failed = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1,1);
-      if( !failed ){
-        context->reserved = 1;
-      }
-    }
-    if (!failed && eFileLock == EXCLUSIVE_LOCK) {
-      /* Acquire an EXCLUSIVE lock */
-        
-      /* Remove the shared lock before trying the range.  we'll need to 
-      ** reestablish the shared lock if we can't get the  afpUnlock
-      */
-      if( !(failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST +
-                         pInode->sharedByte, 1, 0)) ){
-        int failed2 = SQLITE_OK;
-        /* now attemmpt to get the exclusive lock range */
-        failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST, 
-                               SHARED_SIZE, 1);
-        if( failed && (failed2 = afpSetLock(context->dbPath, pFile, 
-                       SHARED_FIRST + pInode->sharedByte, 1, 1)) ){
-          /* Can't reestablish the shared lock.  Sqlite can't deal, this is
-          ** a critical I/O error
-          */
-          rc = ((failed & SQLITE_IOERR) == SQLITE_IOERR) ? failed2 : 
-               SQLITE_IOERR_LOCK;
-          goto afp_end_lock;
-        } 
-      }else{
-        rc = failed; 
-      }
-    }
-    if( failed ){
-      rc = failed;
-    }
-  }
-  
-  if( rc==SQLITE_OK ){
-    pFile->eFileLock = eFileLock;
-    pInode->eFileLock = eFileLock;
-  }else if( eFileLock==EXCLUSIVE_LOCK ){
-    pFile->eFileLock = PENDING_LOCK;
-    pInode->eFileLock = PENDING_LOCK;
-  }
-  
-afp_end_lock:
-  unixLeaveMutex();
-  OSTRACE(("LOCK    %d %s %s (afp)\n", pFile->h, azFileLock(eFileLock), 
-         rc==SQLITE_OK ? "ok" : "failed"));
-  return rc;
-}
-
-/*
-** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
-** must be either NO_LOCK or SHARED_LOCK.
-**
-** If the locking level of the file descriptor is already at or below
-** the requested locking level, this routine is a no-op.
-*/
-static int afpUnlock(sqlite3_file *id, int eFileLock) {
-  int rc = SQLITE_OK;
-  unixFile *pFile = (unixFile*)id;
-  unixInodeInfo *pInode;
-  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
-  int skipShared = 0;
-#ifdef SQLITE_TEST
-  int h = pFile->h;
-#endif
-
-  assert( pFile );
-  OSTRACE(("UNLOCK  %d %d was %d(%d,%d) pid=%d (afp)\n", pFile->h, eFileLock,
-           pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared,
-           getpid()));
-
-  assert( eFileLock<=SHARED_LOCK );
-  if( pFile->eFileLock<=eFileLock ){
-    return SQLITE_OK;
-  }
-  unixEnterMutex();
-  pInode = pFile->pInode;
-  assert( pInode->nShared!=0 );
-  if( pFile->eFileLock>SHARED_LOCK ){
-    assert( pInode->eFileLock==pFile->eFileLock );
-    SimulateIOErrorBenign(1);
-    SimulateIOError( h=(-1) )
-    SimulateIOErrorBenign(0);
-    
-#ifdef SQLITE_DEBUG
-    /* When reducing a lock such that other processes can start
-    ** reading the database file again, make sure that the
-    ** transaction counter was updated if any part of the database
-    ** file changed.  If the transaction counter is not updated,
-    ** other connections to the same file might not realize that
-    ** the file has changed and hence might not know to flush their
-    ** cache.  The use of a stale cache can lead to database corruption.
-    */
-    assert( pFile->inNormalWrite==0
-           || pFile->dbUpdate==0
-           || pFile->transCntrChng==1 );
-    pFile->inNormalWrite = 0;
-#endif
-    
-    if( pFile->eFileLock==EXCLUSIVE_LOCK ){
-      rc = afpSetLock(context->dbPath, pFile, SHARED_FIRST, SHARED_SIZE, 0);
-      if( rc==SQLITE_OK && (eFileLock==SHARED_LOCK || pInode->nShared>1) ){
-        /* only re-establish the shared lock if necessary */
-        int sharedLockByte = SHARED_FIRST+pInode->sharedByte;
-        rc = afpSetLock(context->dbPath, pFile, sharedLockByte, 1, 1);
-      } else {
-        skipShared = 1;
-      }
-    }
-    if( rc==SQLITE_OK && pFile->eFileLock>=PENDING_LOCK ){
-      rc = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 0);
-    } 
-    if( rc==SQLITE_OK && pFile->eFileLock>=RESERVED_LOCK && context->reserved ){
-      rc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1, 0);
-      if( !rc ){ 
-        context->reserved = 0; 
-      }
-    }
-    if( rc==SQLITE_OK && (eFileLock==SHARED_LOCK || pInode->nShared>1)){
-      pInode->eFileLock = SHARED_LOCK;
-    }
-  }
-  if( rc==SQLITE_OK && eFileLock==NO_LOCK ){
-
-    /* Decrement the shared lock counter.  Release the lock using an
-    ** OS call only when all threads in this same process have released
-    ** the lock.
-    */
-    unsigned long long sharedLockByte = SHARED_FIRST+pInode->sharedByte;
-    pInode->nShared--;
-    if( pInode->nShared==0 ){
-      SimulateIOErrorBenign(1);
-      SimulateIOError( h=(-1) )
-      SimulateIOErrorBenign(0);
-      if( !skipShared ){
-        rc = afpSetLock(context->dbPath, pFile, sharedLockByte, 1, 0);
-      }
-      if( !rc ){
-        pInode->eFileLock = NO_LOCK;
-        pFile->eFileLock = NO_LOCK;
-      }
-    }
-    if( rc==SQLITE_OK ){
-      pInode->nLock--;
-      assert( pInode->nLock>=0 );
-      if( pInode->nLock==0 ){
-        closePendingFds(pFile);
-      }
-    }
-  }
-  
-  unixLeaveMutex();
-  if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock;
-  return rc;
-}
-
-/*
-** Close a file & cleanup AFP specific locking context 
-*/
-static int afpClose(sqlite3_file *id) {
-  int rc = SQLITE_OK;
-  if( id ){
-    unixFile *pFile = (unixFile*)id;
-    afpUnlock(id, NO_LOCK);
-    unixEnterMutex();
-    if( pFile->pInode && pFile->pInode->nLock ){
-      /* If there are outstanding locks, do not actually close the file just
-      ** yet because that would clear those locks.  Instead, add the file
-      ** descriptor to pInode->aPending.  It will be automatically closed when
-      ** the last lock is cleared.
-      */
-      setPendingFd(pFile);
-    }
-    releaseInodeInfo(pFile);
-    sqlite3_free(pFile->lockingContext);
-    rc = closeUnixFile(id);
-    unixLeaveMutex();
-  }
-  return rc;
-}
-
-#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
-/*
-** The code above is the AFP lock implementation.  The code is specific
-** to MacOSX and does not work on other unix platforms.  No alternative
-** is available.  If you don't compile for a mac, then the "unix-afp"
-** VFS is not available.
-**
-********************* End of the AFP lock implementation **********************
-******************************************************************************/
-
-/******************************************************************************
-*************************** Begin NFS Locking ********************************/
-
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-/*
- ** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
- ** must be either NO_LOCK or SHARED_LOCK.
- **
- ** If the locking level of the file descriptor is already at or below
- ** the requested locking level, this routine is a no-op.
- */
-static int nfsUnlock(sqlite3_file *id, int eFileLock){
-  return posixUnlock(id, eFileLock, 1);
-}
-
-#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
-/*
-** The code above is the NFS lock implementation.  The code is specific
-** to MacOSX and does not work on other unix platforms.  No alternative
-** is available.  
-**
-********************* End of the NFS lock implementation **********************
-******************************************************************************/
-
-/******************************************************************************
-**************** Non-locking sqlite3_file methods *****************************
-**
-** The next division contains implementations for all methods of the 
-** sqlite3_file object other than the locking methods.  The locking
-** methods were defined in divisions above (one locking method per
-** division).  Those methods that are common to all locking modes
-** are gather together into this division.
-*/
-
-/*
-** Seek to the offset passed as the second argument, then read cnt 
-** bytes into pBuf. Return the number of bytes actually read.
-**
-** NB:  If you define USE_PREAD or USE_PREAD64, then it might also
-** be necessary to define _XOPEN_SOURCE to be 500.  This varies from
-** one system to another.  Since SQLite does not define USE_PREAD
-** in any form by default, we will not attempt to define _XOPEN_SOURCE.
-** See tickets #2741 and #2681.
-**
-** To avoid stomping the errno value on a failed read the lastErrno value
-** is set before returning.
-*/
-static int seekAndRead(unixFile *id, sqlite3_int64 offset, void *pBuf, int cnt){
-  int got;
-  int prior = 0;
-#if (!defined(USE_PREAD) && !defined(USE_PREAD64))
-  i64 newOffset;
-#endif
-  TIMER_START;
-  assert( cnt==(cnt&0x1ffff) );
-  assert( id->h>2 );
-  cnt &= 0x1ffff;
-  do{
-#if defined(USE_PREAD)
-    got = osPread(id->h, pBuf, cnt, offset);
-    SimulateIOError( got = -1 );
-#elif defined(USE_PREAD64)
-    got = osPread64(id->h, pBuf, cnt, offset);
-    SimulateIOError( got = -1 );
-#else
-    newOffset = lseek(id->h, offset, SEEK_SET);
-    SimulateIOError( newOffset-- );
-    if( newOffset!=offset ){
-      if( newOffset == -1 ){
-        ((unixFile*)id)->lastErrno = errno;
-      }else{
-        ((unixFile*)id)->lastErrno = 0;
-      }
-      return -1;
-    }
-    got = osRead(id->h, pBuf, cnt);
-#endif
-    if( got==cnt ) break;
-    if( got<0 ){
-      if( errno==EINTR ){ got = 1; continue; }
-      prior = 0;
-      ((unixFile*)id)->lastErrno = errno;
-      break;
-    }else if( got>0 ){
-      cnt -= got;
-      offset += got;
-      prior += got;
-      pBuf = (void*)(got + (char*)pBuf);
-    }
-  }while( got>0 );
-  TIMER_END;
-  OSTRACE(("READ    %-3d %5d %7lld %llu\n",
-            id->h, got+prior, offset-prior, TIMER_ELAPSED));
-  return got+prior;
-}
-
-/*
-** Read data from a file into a buffer.  Return SQLITE_OK if all
-** bytes were read successfully and SQLITE_IOERR if anything goes
-** wrong.
-*/
-static int unixRead(
-  sqlite3_file *id, 
-  void *pBuf, 
-  int amt,
-  sqlite3_int64 offset
-){
-  unixFile *pFile = (unixFile *)id;
-  int got;
-  assert( id );
-  assert( offset>=0 );
-  assert( amt>0 );
-
-  /* If this is a database file (not a journal, master-journal or temp
-  ** file), the bytes in the locking range should never be read or written. */
-#if 0
-  assert( pFile->pUnused==0
-       || offset>=PENDING_BYTE+512
-       || offset+amt<=PENDING_BYTE 
-  );
-#endif
-
-#if SQLITE_MAX_MMAP_SIZE>0
-  /* Deal with as much of this read request as possible by transfering
-  ** data from the memory mapping using memcpy().  */
-  if( offset<pFile->mmapSize ){
-    if( offset+amt <= pFile->mmapSize ){
-      memcpy(pBuf, &((u8 *)(pFile->pMapRegion))[offset], amt);
-      return SQLITE_OK;
-    }else{
-      int nCopy = pFile->mmapSize - offset;
-      memcpy(pBuf, &((u8 *)(pFile->pMapRegion))[offset], nCopy);
-      pBuf = &((u8 *)pBuf)[nCopy];
-      amt -= nCopy;
-      offset += nCopy;
-    }
-  }
-#endif
-
-  got = seekAndRead(pFile, offset, pBuf, amt);
-  if( got==amt ){
-    return SQLITE_OK;
-  }else if( got<0 ){
-    /* lastErrno set by seekAndRead */
-    return SQLITE_IOERR_READ;
-  }else{
-    pFile->lastErrno = 0; /* not a system error */
-    /* Unread parts of the buffer must be zero-filled */
-    memset(&((char*)pBuf)[got], 0, amt-got);
-    return SQLITE_IOERR_SHORT_READ;
-  }
-}
-
-/*
-** Attempt to seek the file-descriptor passed as the first argument to
-** absolute offset iOff, then attempt to write nBuf bytes of data from
-** pBuf to it. If an error occurs, return -1 and set *piErrno. Otherwise, 
-** return the actual number of bytes written (which may be less than
-** nBuf).
-*/
-static int seekAndWriteFd(
-  int fd,                         /* File descriptor to write to */
-  i64 iOff,                       /* File offset to begin writing at */
-  const void *pBuf,               /* Copy data from this buffer to the file */
-  int nBuf,                       /* Size of buffer pBuf in bytes */
-  int *piErrno                    /* OUT: Error number if error occurs */
-){
-  int rc = 0;                     /* Value returned by system call */
-
-  assert( nBuf==(nBuf&0x1ffff) );
-  assert( fd>2 );
-  nBuf &= 0x1ffff;
-  TIMER_START;
-
-#if defined(USE_PREAD)
-  do{ rc = osPwrite(fd, pBuf, nBuf, iOff); }while( rc<0 && errno==EINTR );
-#elif defined(USE_PREAD64)
-  do{ rc = osPwrite64(fd, pBuf, nBuf, iOff);}while( rc<0 && errno==EINTR);
-#else
-  do{
-    i64 iSeek = lseek(fd, iOff, SEEK_SET);
-    SimulateIOError( iSeek-- );
-
-    if( iSeek!=iOff ){
-      if( piErrno ) *piErrno = (iSeek==-1 ? errno : 0);
-      return -1;
-    }
-    rc = osWrite(fd, pBuf, nBuf);
-  }while( rc<0 && errno==EINTR );
-#endif
-
-  TIMER_END;
-  OSTRACE(("WRITE   %-3d %5d %7lld %llu\n", fd, rc, iOff, TIMER_ELAPSED));
-
-  if( rc<0 && piErrno ) *piErrno = errno;
-  return rc;
-}
-
-
-/*
-** Seek to the offset in id->offset then read cnt bytes into pBuf.
-** Return the number of bytes actually read.  Update the offset.
-**
-** To avoid stomping the errno value on a failed write the lastErrno value
-** is set before returning.
-*/
-static int seekAndWrite(unixFile *id, i64 offset, const void *pBuf, int cnt){
-  return seekAndWriteFd(id->h, offset, pBuf, cnt, &id->lastErrno);
-}
-
-
-/*
-** Write data from a buffer into a file.  Return SQLITE_OK on success
-** or some other error code on failure.
-*/
-static int unixWrite(
-  sqlite3_file *id, 
-  const void *pBuf, 
-  int amt,
-  sqlite3_int64 offset 
-){
-  unixFile *pFile = (unixFile*)id;
-  int wrote = 0;
-  assert( id );
-  assert( amt>0 );
-
-  /* If this is a database file (not a journal, master-journal or temp
-  ** file), the bytes in the locking range should never be read or written. */
-#if 0
-  assert( pFile->pUnused==0
-       || offset>=PENDING_BYTE+512
-       || offset+amt<=PENDING_BYTE 
-  );
-#endif
-
-#ifdef SQLITE_DEBUG
-  /* If we are doing a normal write to a database file (as opposed to
-  ** doing a hot-journal rollback or a write to some file other than a
-  ** normal database file) then record the fact that the database
-  ** has changed.  If the transaction counter is modified, record that
-  ** fact too.
-  */
-  if( pFile->inNormalWrite ){
-    pFile->dbUpdate = 1;  /* The database has been modified */
-    if( offset<=24 && offset+amt>=27 ){
-      int rc;
-      char oldCntr[4];
-      SimulateIOErrorBenign(1);
-      rc = seekAndRead(pFile, 24, oldCntr, 4);
-      SimulateIOErrorBenign(0);
-      if( rc!=4 || memcmp(oldCntr, &((char*)pBuf)[24-offset], 4)!=0 ){
-        pFile->transCntrChng = 1;  /* The transaction counter has changed */
-      }
-    }
-  }
-#endif
-
-#if SQLITE_MAX_MMAP_SIZE>0
-  /* Deal with as much of this write request as possible by transfering
-  ** data from the memory mapping using memcpy().  */
-  if( offset<pFile->mmapSize ){
-    if( offset+amt <= pFile->mmapSize ){
-      memcpy(&((u8 *)(pFile->pMapRegion))[offset], pBuf, amt);
-      return SQLITE_OK;
-    }else{
-      int nCopy = pFile->mmapSize - offset;
-      memcpy(&((u8 *)(pFile->pMapRegion))[offset], pBuf, nCopy);
-      pBuf = &((u8 *)pBuf)[nCopy];
-      amt -= nCopy;
-      offset += nCopy;
-    }
-  }
-#endif
-
-  while( amt>0 && (wrote = seekAndWrite(pFile, offset, pBuf, amt))>0 ){
-    amt -= wrote;
-    offset += wrote;
-    pBuf = &((char*)pBuf)[wrote];
-  }
-  SimulateIOError(( wrote=(-1), amt=1 ));
-  SimulateDiskfullError(( wrote=0, amt=1 ));
-
-  if( amt>0 ){
-    if( wrote<0 && pFile->lastErrno!=ENOSPC ){
-      /* lastErrno set by seekAndWrite */
-      return SQLITE_IOERR_WRITE;
-    }else{
-      pFile->lastErrno = 0; /* not a system error */
-      return SQLITE_FULL;
-    }
-  }
-
-  return SQLITE_OK;
-}
-
-#ifdef SQLITE_TEST
-/*
-** Count the number of fullsyncs and normal syncs.  This is used to test
-** that syncs and fullsyncs are occurring at the right times.
-*/
-int sqlite3_sync_count = 0;
-int sqlite3_fullsync_count = 0;
-#endif
-
-/*
-** We do not trust systems to provide a working fdatasync().  Some do.
-** Others do no.  To be safe, we will stick with the (slightly slower)
-** fsync(). If you know that your system does support fdatasync() correctly,
-** then simply compile with -Dfdatasync=fdatasync
-*/
-#if !defined(fdatasync)
-# define fdatasync fsync
-#endif
-
-/*
-** Define HAVE_FULLFSYNC to 0 or 1 depending on whether or not
-** the F_FULLFSYNC macro is defined.  F_FULLFSYNC is currently
-** only available on Mac OS X.  But that could change.
-*/
-#ifdef F_FULLFSYNC
-# define HAVE_FULLFSYNC 1
-#else
-# define HAVE_FULLFSYNC 0
-#endif
-
-
-/*
-** The fsync() system call does not work as advertised on many
-** unix systems.  The following procedure is an attempt to make
-** it work better.
-**
-** The SQLITE_NO_SYNC macro disables all fsync()s.  This is useful
-** for testing when we want to run through the test suite quickly.
-** You are strongly advised *not* to deploy with SQLITE_NO_SYNC
-** enabled, however, since with SQLITE_NO_SYNC enabled, an OS crash
-** or power failure will likely corrupt the database file.
-**
-** SQLite sets the dataOnly flag if the size of the file is unchanged.
-** The idea behind dataOnly is that it should only write the file content
-** to disk, not the inode.  We only set dataOnly if the file size is 
-** unchanged since the file size is part of the inode.  However, 
-** Ted Ts'o tells us that fdatasync() will also write the inode if the
-** file size has changed.  The only real difference between fdatasync()
-** and fsync(), Ted tells us, is that fdatasync() will not flush the
-** inode if the mtime or owner or other inode attributes have changed.
-** We only care about the file size, not the other file attributes, so
-** as far as SQLite is concerned, an fdatasync() is always adequate.
-** So, we always use fdatasync() if it is available, regardless of
-** the value of the dataOnly flag.
-*/
-static int full_fsync(int fd, int fullSync, int dataOnly){
-  int rc;
-
-  /* The following "ifdef/elif/else/" block has the same structure as
-  ** the one below. It is replicated here solely to avoid cluttering 
-  ** up the real code with the UNUSED_PARAMETER() macros.
-  */
-#ifdef SQLITE_NO_SYNC
-  UNUSED_PARAMETER(fd);
-  UNUSED_PARAMETER(fullSync);
-  UNUSED_PARAMETER(dataOnly);
-#elif HAVE_FULLFSYNC
-  UNUSED_PARAMETER(dataOnly);
-#else
-  UNUSED_PARAMETER(fullSync);
-  UNUSED_PARAMETER(dataOnly);
-#endif
-
-  /* Record the number of times that we do a normal fsync() and 
-  ** FULLSYNC.  This is used during testing to verify that this procedure
-  ** gets called with the correct arguments.
-  */
-#ifdef SQLITE_TEST
-  if( fullSync ) sqlite3_fullsync_count++;
-  sqlite3_sync_count++;
-#endif
-
-  /* If we compiled with the SQLITE_NO_SYNC flag, then syncing is a
-  ** no-op
-  */
-#ifdef SQLITE_NO_SYNC
-  rc = SQLITE_OK;
-#elif HAVE_FULLFSYNC
-  if( fullSync ){
-    rc = osFcntl(fd, F_FULLFSYNC, 0);
-  }else{
-    rc = 1;
-  }
-  /* If the FULLFSYNC failed, fall back to attempting an fsync().
-  ** It shouldn't be possible for fullfsync to fail on the local 
-  ** file system (on OSX), so failure indicates that FULLFSYNC
-  ** isn't supported for this file system. So, attempt an fsync 
-  ** and (for now) ignore the overhead of a superfluous fcntl call.  
-  ** It'd be better to detect fullfsync support once and avoid 
-  ** the fcntl call every time sync is called.
-  */
-  if( rc ) rc = fsync(fd);
-
-#elif defined(__APPLE__)
-  /* fdatasync() on HFS+ doesn't yet flush the file size if it changed correctly
-  ** so currently we default to the macro that redefines fdatasync to fsync
-  */
-  rc = fsync(fd);
-#else 
-  rc = fdatasync(fd);
-#if OS_VXWORKS
-  if( rc==-1 && errno==ENOTSUP ){
-    rc = fsync(fd);
-  }
-#endif /* OS_VXWORKS */
-#endif /* ifdef SQLITE_NO_SYNC elif HAVE_FULLFSYNC */
-
-  if( OS_VXWORKS && rc!= -1 ){
-    rc = 0;
-  }
-  return rc;
-}
-
-/*
-** Open a file descriptor to the directory containing file zFilename.
-** If successful, *pFd is set to the opened file descriptor and
-** SQLITE_OK is returned. If an error occurs, either SQLITE_NOMEM
-** or SQLITE_CANTOPEN is returned and *pFd is set to an undefined
-** value.
-**
-** The directory file descriptor is used for only one thing - to
-** fsync() a directory to make sure file creation and deletion events
-** are flushed to disk.  Such fsyncs are not needed on newer
-** journaling filesystems, but are required on older filesystems.
-**
-** This routine can be overridden using the xSetSysCall interface.
-** The ability to override this routine was added in support of the
-** chromium sandbox.  Opening a directory is a security risk (we are
-** told) so making it overrideable allows the chromium sandbox to
-** replace this routine with a harmless no-op.  To make this routine
-** a no-op, replace it with a stub that returns SQLITE_OK but leaves
-** *pFd set to a negative number.
-**
-** If SQLITE_OK is returned, the caller is responsible for closing
-** the file descriptor *pFd using close().
-*/
-static int openDirectory(const char *zFilename, int *pFd){
-  int ii;
-  int fd = -1;
-  char zDirname[MAX_PATHNAME+1];
-
-  sqlite3_snprintf(MAX_PATHNAME, zDirname, "%s", zFilename);
-  for(ii=(int)strlen(zDirname); ii>1 && zDirname[ii]!='/'; ii--);
-  if( ii>0 ){
-    zDirname[ii] = '\0';
-    fd = robust_open(zDirname, O_RDONLY|O_BINARY, 0);
-    if( fd>=0 ){
-      OSTRACE(("OPENDIR %-3d %s\n", fd, zDirname));
-    }
-  }
-  *pFd = fd;
-  return (fd>=0?SQLITE_OK:unixLogError(SQLITE_CANTOPEN_BKPT, "open", zDirname));
-}
-
-/*
-** Make sure all writes to a particular file are committed to disk.
-**
-** If dataOnly==0 then both the file itself and its metadata (file
-** size, access time, etc) are synced.  If dataOnly!=0 then only the
-** file data is synced.
-**
-** Under Unix, also make sure that the directory entry for the file
-** has been created by fsync-ing the directory that contains the file.
-** If we do not do this and we encounter a power failure, the directory
-** entry for the journal might not exist after we reboot.  The next
-** SQLite to access the file will not know that the journal exists (because
-** the directory entry for the journal was never created) and the transaction
-** will not roll back - possibly leading to database corruption.
-*/
-static int unixSync(sqlite3_file *id, int flags){
-  int rc;
-  unixFile *pFile = (unixFile*)id;
-
-  int isDataOnly = (flags&SQLITE_SYNC_DATAONLY);
-  int isFullsync = (flags&0x0F)==SQLITE_SYNC_FULL;
-
-  /* Check that one of SQLITE_SYNC_NORMAL or FULL was passed */
-  assert((flags&0x0F)==SQLITE_SYNC_NORMAL
-      || (flags&0x0F)==SQLITE_SYNC_FULL
-  );
-
-  /* Unix cannot, but some systems may return SQLITE_FULL from here. This
-  ** line is to test that doing so does not cause any problems.
-  */
-  SimulateDiskfullError( return SQLITE_FULL );
-
-  assert( pFile );
-  OSTRACE(("SYNC    %-3d\n", pFile->h));
-  rc = full_fsync(pFile->h, isFullsync, isDataOnly);
-  SimulateIOError( rc=1 );
-  if( rc ){
-    pFile->lastErrno = errno;
-    return unixLogError(SQLITE_IOERR_FSYNC, "full_fsync", pFile->zPath);
-  }
-
-  /* Also fsync the directory containing the file if the DIRSYNC flag
-  ** is set.  This is a one-time occurrence.  Many systems (examples: AIX)
-  ** are unable to fsync a directory, so ignore errors on the fsync.
-  */
-  if( pFile->ctrlFlags & UNIXFILE_DIRSYNC ){
-    int dirfd;
-    OSTRACE(("DIRSYNC %s (have_fullfsync=%d fullsync=%d)\n", pFile->zPath,
-            HAVE_FULLFSYNC, isFullsync));
-    rc = osOpenDirectory(pFile->zPath, &dirfd);
-    if( rc==SQLITE_OK && dirfd>=0 ){
-      full_fsync(dirfd, 0, 0);
-      robust_close(pFile, dirfd, __LINE__);
-    }else if( rc==SQLITE_CANTOPEN ){
-      rc = SQLITE_OK;
-    }
-    pFile->ctrlFlags &= ~UNIXFILE_DIRSYNC;
-  }
-  return rc;
-}
-
-/*
-** Truncate an open file to a specified size
-*/
-static int unixTruncate(sqlite3_file *id, i64 nByte){
-  unixFile *pFile = (unixFile *)id;
-  int rc;
-  assert( pFile );
-  SimulateIOError( return SQLITE_IOERR_TRUNCATE );
-
-  /* If the user has configured a chunk-size for this file, truncate the
-  ** file so that it consists of an integer number of chunks (i.e. the
-  ** actual file size after the operation may be larger than the requested
-  ** size).
-  */
-  if( pFile->szChunk>0 ){
-    nByte = ((nByte + pFile->szChunk - 1)/pFile->szChunk) * pFile->szChunk;
-  }
-
-  rc = robust_ftruncate(pFile->h, nByte);
-  if( rc ){
-    pFile->lastErrno = errno;
-    return unixLogError(SQLITE_IOERR_TRUNCATE, "ftruncate", pFile->zPath);
-  }else{
-#ifdef SQLITE_DEBUG
-    /* If we are doing a normal write to a database file (as opposed to
-    ** doing a hot-journal rollback or a write to some file other than a
-    ** normal database file) and we truncate the file to zero length,
-    ** that effectively updates the change counter.  This might happen
-    ** when restoring a database using the backup API from a zero-length
-    ** source.
-    */
-    if( pFile->inNormalWrite && nByte==0 ){
-      pFile->transCntrChng = 1;
-    }
-#endif
-
-#if SQLITE_MAX_MMAP_SIZE>0
-    /* If the file was just truncated to a size smaller than the currently
-    ** mapped region, reduce the effective mapping size as well. SQLite will
-    ** use read() and write() to access data beyond this point from now on.  
-    */
-    if( nByte<pFile->mmapSize ){
-      pFile->mmapSize = nByte;
-    }
-#endif
-
-    return SQLITE_OK;
-  }
-}
-
-/*
-** Determine the current size of a file in bytes
-*/
-static int unixFileSize(sqlite3_file *id, i64 *pSize){
-  int rc;
-  struct stat buf;
-  assert( id );
-  rc = osFstat(((unixFile*)id)->h, &buf);
-  SimulateIOError( rc=1 );
-  if( rc!=0 ){
-    ((unixFile*)id)->lastErrno = errno;
-    return SQLITE_IOERR_FSTAT;
-  }
-  *pSize = buf.st_size;
-
-  /* When opening a zero-size database, the findInodeInfo() procedure
-  ** writes a single byte into that file in order to work around a bug
-  ** in the OS-X msdos filesystem.  In order to avoid problems with upper
-  ** layers, we need to report this file size as zero even though it is
-  ** really 1.   Ticket #3260.
-  */
-  if( *pSize==1 ) *pSize = 0;
-
-
-  return SQLITE_OK;
-}
-
-#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
-/*
-** Handler for proxy-locking file-control verbs.  Defined below in the
-** proxying locking division.
-*/
-static int proxyFileControl(sqlite3_file*,int,void*);
-#endif
-
-/* 
-** This function is called to handle the SQLITE_FCNTL_SIZE_HINT 
-** file-control operation.  Enlarge the database to nBytes in size
-** (rounded up to the next chunk-size).  If the database is already
-** nBytes or larger, this routine is a no-op.
-*/
-static int fcntlSizeHint(unixFile *pFile, i64 nByte){
-  if( pFile->szChunk>0 ){
-    i64 nSize;                    /* Required file size */
-    struct stat buf;              /* Used to hold return values of fstat() */
-   
-    if( osFstat(pFile->h, &buf) ) return SQLITE_IOERR_FSTAT;
-
-    nSize = ((nByte+pFile->szChunk-1) / pFile->szChunk) * pFile->szChunk;
-    if( nSize>(i64)buf.st_size ){
-
-#if defined(HAVE_POSIX_FALLOCATE) && HAVE_POSIX_FALLOCATE
-      /* The code below is handling the return value of osFallocate() 
-      ** correctly. posix_fallocate() is defined to "returns zero on success, 
-      ** or an error number on  failure". See the manpage for details. */
-      int err;
-      do{
-        err = osFallocate(pFile->h, buf.st_size, nSize-buf.st_size);
-      }while( err==EINTR );
-      if( err ) return SQLITE_IOERR_WRITE;
-#else
-      /* If the OS does not have posix_fallocate(), fake it. First use
-      ** ftruncate() to set the file size, then write a single byte to
-      ** the last byte in each block within the extended region. This
-      ** is the same technique used by glibc to implement posix_fallocate()
-      ** on systems that do not have a real fallocate() system call.
-      */
-      int nBlk = buf.st_blksize;  /* File-system block size */
-      i64 iWrite;                 /* Next offset to write to */
-
-      if( robust_ftruncate(pFile->h, nSize) ){
-        pFile->lastErrno = errno;
-        return unixLogError(SQLITE_IOERR_TRUNCATE, "ftruncate", pFile->zPath);
-      }
-      iWrite = ((buf.st_size + 2*nBlk - 1)/nBlk)*nBlk-1;
-      while( iWrite<nSize ){
-        int nWrite = seekAndWrite(pFile, iWrite, "", 1);
-        if( nWrite!=1 ) return SQLITE_IOERR_WRITE;
-        iWrite += nBlk;
-      }
-#endif
-    }
-  }
-
-#if SQLITE_MAX_MMAP_SIZE>0
-  if( pFile->mmapSizeMax>0 && nByte>pFile->mmapSize ){
-    int rc;
-    if( pFile->szChunk<=0 ){
-      if( robust_ftruncate(pFile->h, nByte) ){
-        pFile->lastErrno = errno;
-        return unixLogError(SQLITE_IOERR_TRUNCATE, "ftruncate", pFile->zPath);
-      }
-    }
-
-    rc = unixMapfile(pFile, nByte);
-    return rc;
-  }
-#endif
-
-  return SQLITE_OK;
-}
-
-/*
-** If *pArg is initially negative then this is a query.  Set *pArg to
-** 1 or 0 depending on whether or not bit mask of pFile->ctrlFlags is set.
-**
-** If *pArg is 0 or 1, then clear or set the mask bit of pFile->ctrlFlags.
-*/
-static void unixModeBit(unixFile *pFile, unsigned char mask, int *pArg){
-  if( *pArg<0 ){
-    *pArg = (pFile->ctrlFlags & mask)!=0;
-  }else if( (*pArg)==0 ){
-    pFile->ctrlFlags &= ~mask;
-  }else{
-    pFile->ctrlFlags |= mask;
-  }
-}
-
-/* Forward declaration */
-static int unixGetTempname(int nBuf, char *zBuf);
-
-/*
-** Information and control of an open file handle.
-*/
-static int unixFileControl(sqlite3_file *id, int op, void *pArg){
-  unixFile *pFile = (unixFile*)id;
-  switch( op ){
-    case SQLITE_FCNTL_LOCKSTATE: {
-      *(int*)pArg = pFile->eFileLock;
-      return SQLITE_OK;
-    }
-    case SQLITE_LAST_ERRNO: {
-      *(int*)pArg = pFile->lastErrno;
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_CHUNK_SIZE: {
-      pFile->szChunk = *(int *)pArg;
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_SIZE_HINT: {
-      int rc;
-      SimulateIOErrorBenign(1);
-      rc = fcntlSizeHint(pFile, *(i64 *)pArg);
-      SimulateIOErrorBenign(0);
-      return rc;
-    }
-    case SQLITE_FCNTL_PERSIST_WAL: {
-      unixModeBit(pFile, UNIXFILE_PERSIST_WAL, (int*)pArg);
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_POWERSAFE_OVERWRITE: {
-      unixModeBit(pFile, UNIXFILE_PSOW, (int*)pArg);
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_VFSNAME: {
-      *(char**)pArg = sqlite3_mprintf("%s", pFile->pVfs->zName);
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_TEMPFILENAME: {
-      char *zTFile = sqlite3_malloc( pFile->pVfs->mxPathname );
-      if( zTFile ){
-        unixGetTempname(pFile->pVfs->mxPathname, zTFile);
-        *(char**)pArg = zTFile;
-      }
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_HAS_MOVED: {
-      *(int*)pArg = fileHasMoved(pFile);
-      return SQLITE_OK;
-    }
-#if SQLITE_MAX_MMAP_SIZE>0
-    case SQLITE_FCNTL_MMAP_SIZE: {
-      i64 newLimit = *(i64*)pArg;
-      int rc = SQLITE_OK;
-      if( newLimit>sqlite3GlobalConfig.mxMmap ){
-        newLimit = sqlite3GlobalConfig.mxMmap;
-      }
-      *(i64*)pArg = pFile->mmapSizeMax;
-      if( newLimit>=0 && newLimit!=pFile->mmapSizeMax && pFile->nFetchOut==0 ){
-        pFile->mmapSizeMax = newLimit;
-        if( pFile->mmapSize>0 ){
-          unixUnmapfile(pFile);
-          rc = unixMapfile(pFile, -1);
-        }
-      }
-      return rc;
-    }
-#endif
-#ifdef SQLITE_DEBUG
-    /* The pager calls this method to signal that it has done
-    ** a rollback and that the database is therefore unchanged and
-    ** it hence it is OK for the transaction change counter to be
-    ** unchanged.
-    */
-    case SQLITE_FCNTL_DB_UNCHANGED: {
-      ((unixFile*)id)->dbUpdate = 0;
-      return SQLITE_OK;
-    }
-#endif
-#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
-    case SQLITE_SET_LOCKPROXYFILE:
-    case SQLITE_GET_LOCKPROXYFILE: {
-      return proxyFileControl(id,op,pArg);
-    }
-#endif /* SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__) */
-  }
-  return SQLITE_NOTFOUND;
-}
-
-/*
-** Return the sector size in bytes of the underlying block device for
-** the specified file. This is almost always 512 bytes, but may be
-** larger for some devices.
-**
-** SQLite code assumes this function cannot fail. It also assumes that
-** if two files are created in the same file-system directory (i.e.
-** a database and its journal file) that the sector size will be the
-** same for both.
-*/
-#ifndef __QNXNTO__ 
-static int unixSectorSize(sqlite3_file *NotUsed){
-  UNUSED_PARAMETER(NotUsed);
-  return SQLITE_DEFAULT_SECTOR_SIZE;
-}
-#endif
-
-/*
-** The following version of unixSectorSize() is optimized for QNX.
-*/
-#ifdef __QNXNTO__
-#include <sys/dcmd_blk.h>
-#include <sys/statvfs.h>
-static int unixSectorSize(sqlite3_file *id){
-  unixFile *pFile = (unixFile*)id;
-  if( pFile->sectorSize == 0 ){
-    struct statvfs fsInfo;
-       
-    /* Set defaults for non-supported filesystems */
-    pFile->sectorSize = SQLITE_DEFAULT_SECTOR_SIZE;
-    pFile->deviceCharacteristics = 0;
-    if( fstatvfs(pFile->h, &fsInfo) == -1 ) {
-      return pFile->sectorSize;
-    }
-
-    if( !strcmp(fsInfo.f_basetype, "tmp") ) {
-      pFile->sectorSize = fsInfo.f_bsize;
-      pFile->deviceCharacteristics =
-        SQLITE_IOCAP_ATOMIC4K |       /* All ram filesystem writes are atomic */
-        SQLITE_IOCAP_SAFE_APPEND |    /* growing the file does not occur until
-                                      ** the write succeeds */
-        SQLITE_IOCAP_SEQUENTIAL |     /* The ram filesystem has no write behind
-                                      ** so it is ordered */
-        0;
-    }else if( strstr(fsInfo.f_basetype, "etfs") ){
-      pFile->sectorSize = fsInfo.f_bsize;
-      pFile->deviceCharacteristics =
-        /* etfs cluster size writes are atomic */
-        (pFile->sectorSize / 512 * SQLITE_IOCAP_ATOMIC512) |
-        SQLITE_IOCAP_SAFE_APPEND |    /* growing the file does not occur until
-                                      ** the write succeeds */
-        SQLITE_IOCAP_SEQUENTIAL |     /* The ram filesystem has no write behind
-                                      ** so it is ordered */
-        0;
-    }else if( !strcmp(fsInfo.f_basetype, "qnx6") ){
-      pFile->sectorSize = fsInfo.f_bsize;
-      pFile->deviceCharacteristics =
-        SQLITE_IOCAP_ATOMIC |         /* All filesystem writes are atomic */
-        SQLITE_IOCAP_SAFE_APPEND |    /* growing the file does not occur until
-                                      ** the write succeeds */
-        SQLITE_IOCAP_SEQUENTIAL |     /* The ram filesystem has no write behind
-                                      ** so it is ordered */
-        0;
-    }else if( !strcmp(fsInfo.f_basetype, "qnx4") ){
-      pFile->sectorSize = fsInfo.f_bsize;
-      pFile->deviceCharacteristics =
-        /* full bitset of atomics from max sector size and smaller */
-        ((pFile->sectorSize / 512 * SQLITE_IOCAP_ATOMIC512) << 1) - 2 |
-        SQLITE_IOCAP_SEQUENTIAL |     /* The ram filesystem has no write behind
-                                      ** so it is ordered */
-        0;
-    }else if( strstr(fsInfo.f_basetype, "dos") ){
-      pFile->sectorSize = fsInfo.f_bsize;
-      pFile->deviceCharacteristics =
-        /* full bitset of atomics from max sector size and smaller */
-        ((pFile->sectorSize / 512 * SQLITE_IOCAP_ATOMIC512) << 1) - 2 |
-        SQLITE_IOCAP_SEQUENTIAL |     /* The ram filesystem has no write behind
-                                      ** so it is ordered */
-        0;
-    }else{
-      pFile->deviceCharacteristics =
-        SQLITE_IOCAP_ATOMIC512 |      /* blocks are atomic */
-        SQLITE_IOCAP_SAFE_APPEND |    /* growing the file does not occur until
-                                      ** the write succeeds */
-        0;
-    }
-  }
-  /* Last chance verification.  If the sector size isn't a multiple of 512
-  ** then it isn't valid.*/
-  if( pFile->sectorSize % 512 != 0 ){
-    pFile->deviceCharacteristics = 0;
-    pFile->sectorSize = SQLITE_DEFAULT_SECTOR_SIZE;
-  }
-  return pFile->sectorSize;
-}
-#endif /* __QNXNTO__ */
-
-/*
-** Return the device characteristics for the file.
-**
-** This VFS is set up to return SQLITE_IOCAP_POWERSAFE_OVERWRITE by default.
-** However, that choice is controversial since technically the underlying
-** file system does not always provide powersafe overwrites.  (In other
-** words, after a power-loss event, parts of the file that were never
-** written might end up being altered.)  However, non-PSOW behavior is very,
-** very rare.  And asserting PSOW makes a large reduction in the amount
-** of required I/O for journaling, since a lot of padding is eliminated.
-**  Hence, while POWERSAFE_OVERWRITE is on by default, there is a file-control
-** available to turn it off and URI query parameter available to turn it off.
-*/
-static int unixDeviceCharacteristics(sqlite3_file *id){
-  unixFile *p = (unixFile*)id;
-  int rc = 0;
-#ifdef __QNXNTO__
-  if( p->sectorSize==0 ) unixSectorSize(id);
-  rc = p->deviceCharacteristics;
-#endif
-  if( p->ctrlFlags & UNIXFILE_PSOW ){
-    rc |= SQLITE_IOCAP_POWERSAFE_OVERWRITE;
-  }
-  return rc;
-}
-
-#if !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0
-
-/*
-** Return the system page size.
-**
-** This function should not be called directly by other code in this file. 
-** Instead, it should be called via macro osGetpagesize().
-*/
-static int unixGetpagesize(void){
-#if defined(_BSD_SOURCE)
-  return getpagesize();
-#else
-  return (int)sysconf(_SC_PAGESIZE);
-#endif
-}
-
-#endif /* !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0 */
-
-#ifndef SQLITE_OMIT_WAL
-
-/*
-** Object used to represent an shared memory buffer.  
-**
-** When multiple threads all reference the same wal-index, each thread
-** has its own unixShm object, but they all point to a single instance
-** of this unixShmNode object.  In other words, each wal-index is opened
-** only once per process.
-**
-** Each unixShmNode object is connected to a single unixInodeInfo object.
-** We could coalesce this object into unixInodeInfo, but that would mean
-** every open file that does not use shared memory (in other words, most
-** open files) would have to carry around this extra information.  So
-** the unixInodeInfo object contains a pointer to this unixShmNode object
-** and the unixShmNode object is created only when needed.
-**
-** unixMutexHeld() must be true when creating or destroying
-** this object or while reading or writing the following fields:
-**
-**      nRef
-**
-** The following fields are read-only after the object is created:
-** 
-**      fid
-**      zFilename
-**
-** Either unixShmNode.mutex must be held or unixShmNode.nRef==0 and
-** unixMutexHeld() is true when reading or writing any other field
-** in this structure.
-*/
-struct unixShmNode {
-  unixInodeInfo *pInode;     /* unixInodeInfo that owns this SHM node */
-  sqlite3_mutex *mutex;      /* Mutex to access this object */
-  char *zFilename;           /* Name of the mmapped file */
-  int h;                     /* Open file descriptor */
-  int szRegion;              /* Size of shared-memory regions */
-  u16 nRegion;               /* Size of array apRegion */
-  u8 isReadonly;             /* True if read-only */
-  char **apRegion;           /* Array of mapped shared-memory regions */
-  int nRef;                  /* Number of unixShm objects pointing to this */
-  unixShm *pFirst;           /* All unixShm objects pointing to this */
-#ifdef SQLITE_DEBUG
-  u8 exclMask;               /* Mask of exclusive locks held */
-  u8 sharedMask;             /* Mask of shared locks held */
-  u8 nextShmId;              /* Next available unixShm.id value */
-#endif
-};
-
-/*
-** Structure used internally by this VFS to record the state of an
-** open shared memory connection.
-**
-** The following fields are initialized when this object is created and
-** are read-only thereafter:
-**
-**    unixShm.pFile
-**    unixShm.id
-**
-** All other fields are read/write.  The unixShm.pFile->mutex must be held
-** while accessing any read/write fields.
-*/
-struct unixShm {
-  unixShmNode *pShmNode;     /* The underlying unixShmNode object */
-  unixShm *pNext;            /* Next unixShm with the same unixShmNode */
-  u8 hasMutex;               /* True if holding the unixShmNode mutex */
-  u8 id;                     /* Id of this connection within its unixShmNode */
-  u16 sharedMask;            /* Mask of shared locks held */
-  u16 exclMask;              /* Mask of exclusive locks held */
-};
-
-/*
-** Constants used for locking
-*/
-#define UNIX_SHM_BASE   ((22+SQLITE_SHM_NLOCK)*4)         /* first lock byte */
-#define UNIX_SHM_DMS    (UNIX_SHM_BASE+SQLITE_SHM_NLOCK)  /* deadman switch */
-
-/*
-** Apply posix advisory locks for all bytes from ofst through ofst+n-1.
-**
-** Locks block if the mask is exactly UNIX_SHM_C and are non-blocking
-** otherwise.
-*/
-static int unixShmSystemLock(
-  unixShmNode *pShmNode, /* Apply locks to this open shared-memory segment */
-  int lockType,          /* F_UNLCK, F_RDLCK, or F_WRLCK */
-  int ofst,              /* First byte of the locking range */
-  int n                  /* Number of bytes to lock */
-){
-  struct flock f;       /* The posix advisory locking structure */
-  int rc = SQLITE_OK;   /* Result code form fcntl() */
-
-  /* Access to the unixShmNode object is serialized by the caller */
-  assert( sqlite3_mutex_held(pShmNode->mutex) || pShmNode->nRef==0 );
-
-  /* Shared locks never span more than one byte */
-  assert( n==1 || lockType!=F_RDLCK );
-
-  /* Locks are within range */
-  assert( n>=1 && n<SQLITE_SHM_NLOCK );
-
-  if( pShmNode->h>=0 ){
-    /* Initialize the locking parameters */
-    memset(&f, 0, sizeof(f));
-    f.l_type = lockType;
-    f.l_whence = SEEK_SET;
-    f.l_start = ofst;
-    f.l_len = n;
-
-    rc = osFcntl(pShmNode->h, F_SETLK, &f);
-    rc = (rc!=(-1)) ? SQLITE_OK : SQLITE_BUSY;
-  }
-
-  /* Update the global lock state and do debug tracing */
-#ifdef SQLITE_DEBUG
-  { u16 mask;
-  OSTRACE(("SHM-LOCK "));
-  mask = ofst>31 ? 0xffff : (1<<(ofst+n)) - (1<<ofst);
-  if( rc==SQLITE_OK ){
-    if( lockType==F_UNLCK ){
-      OSTRACE(("unlock %d ok", ofst));
-      pShmNode->exclMask &= ~mask;
-      pShmNode->sharedMask &= ~mask;
-    }else if( lockType==F_RDLCK ){
-      OSTRACE(("read-lock %d ok", ofst));
-      pShmNode->exclMask &= ~mask;
-      pShmNode->sharedMask |= mask;
-    }else{
-      assert( lockType==F_WRLCK );
-      OSTRACE(("write-lock %d ok", ofst));
-      pShmNode->exclMask |= mask;
-      pShmNode->sharedMask &= ~mask;
-    }
-  }else{
-    if( lockType==F_UNLCK ){
-      OSTRACE(("unlock %d failed", ofst));
-    }else if( lockType==F_RDLCK ){
-      OSTRACE(("read-lock failed"));
-    }else{
-      assert( lockType==F_WRLCK );
-      OSTRACE(("write-lock %d failed", ofst));
-    }
-  }
-  OSTRACE((" - afterwards %03x,%03x\n",
-           pShmNode->sharedMask, pShmNode->exclMask));
-  }
-#endif
-
-  return rc;        
-}
-
-/*
-** Return the minimum number of 32KB shm regions that should be mapped at
-** a time, assuming that each mapping must be an integer multiple of the
-** current system page-size.
-**
-** Usually, this is 1. The exception seems to be systems that are configured
-** to use 64KB pages - in this case each mapping must cover at least two
-** shm regions.
-*/
-static int unixShmRegionPerMap(void){
-  int shmsz = 32*1024;            /* SHM region size */
-  int pgsz = osGetpagesize();   /* System page size */
-  assert( ((pgsz-1)&pgsz)==0 );   /* Page size must be a power of 2 */
-  if( pgsz<shmsz ) return 1;
-  return pgsz/shmsz;
-}
-
-/*
-** Purge the unixShmNodeList list of all entries with unixShmNode.nRef==0.
-**
-** This is not a VFS shared-memory method; it is a utility function called
-** by VFS shared-memory methods.
-*/
-static void unixShmPurge(unixFile *pFd){
-  unixShmNode *p = pFd->pInode->pShmNode;
-  assert( unixMutexHeld() );
-  if( p && p->nRef==0 ){
-    int nShmPerMap = unixShmRegionPerMap();
-    int i;
-    assert( p->pInode==pFd->pInode );
-    sqlite3_mutex_free(p->mutex);
-    for(i=0; i<p->nRegion; i+=nShmPerMap){
-      if( p->h>=0 ){
-        osMunmap(p->apRegion[i], p->szRegion);
-      }else{
-        sqlite3_free(p->apRegion[i]);
-      }
-    }
-    sqlite3_free(p->apRegion);
-    if( p->h>=0 ){
-      robust_close(pFd, p->h, __LINE__);
-      p->h = -1;
-    }
-    p->pInode->pShmNode = 0;
-    sqlite3_free(p);
-  }
-}
-
-/*
-** Open a shared-memory area associated with open database file pDbFd.  
-** This particular implementation uses mmapped files.
-**
-** The file used to implement shared-memory is in the same directory
-** as the open database file and has the same name as the open database
-** file with the "-shm" suffix added.  For example, if the database file
-** is "/home/user1/config.db" then the file that is created and mmapped
-** for shared memory will be called "/home/user1/config.db-shm".  
-**
-** Another approach to is to use files in /dev/shm or /dev/tmp or an
-** some other tmpfs mount. But if a file in a different directory
-** from the database file is used, then differing access permissions
-** or a chroot() might cause two different processes on the same
-** database to end up using different files for shared memory - 
-** meaning that their memory would not really be shared - resulting
-** in database corruption.  Nevertheless, this tmpfs file usage
-** can be enabled at compile-time using -DSQLITE_SHM_DIRECTORY="/dev/shm"
-** or the equivalent.  The use of the SQLITE_SHM_DIRECTORY compile-time
-** option results in an incompatible build of SQLite;  builds of SQLite
-** that with differing SQLITE_SHM_DIRECTORY settings attempt to use the
-** same database file at the same time, database corruption will likely
-** result. The SQLITE_SHM_DIRECTORY compile-time option is considered
-** "unsupported" and may go away in a future SQLite release.
-**
-** When opening a new shared-memory file, if no other instances of that
-** file are currently open, in this process or in other processes, then
-** the file must be truncated to zero length or have its header cleared.
-**
-** If the original database file (pDbFd) is using the "unix-excl" VFS
-** that means that an exclusive lock is held on the database file and
-** that no other processes are able to read or write the database.  In
-** that case, we do not really need shared memory.  No shared memory
-** file is created.  The shared memory will be simulated with heap memory.
-*/
-static int unixOpenSharedMemory(unixFile *pDbFd){
-  struct unixShm *p = 0;          /* The connection to be opened */
-  struct unixShmNode *pShmNode;   /* The underlying mmapped file */
-  int rc;                         /* Result code */
-  unixInodeInfo *pInode;          /* The inode of fd */
-  char *zShmFilename;             /* Name of the file used for SHM */
-  int nShmFilename;               /* Size of the SHM filename in bytes */
-
-  /* Allocate space for the new unixShm object. */
-  p = sqlite3_malloc( sizeof(*p) );
-  if( p==0 ) return SQLITE_NOMEM;
-  memset(p, 0, sizeof(*p));
-  assert( pDbFd->pShm==0 );
-
-  /* Check to see if a unixShmNode object already exists. Reuse an existing
-  ** one if present. Create a new one if necessary.
-  */
-  unixEnterMutex();
-  pInode = pDbFd->pInode;
-  pShmNode = pInode->pShmNode;
-  if( pShmNode==0 ){
-    struct stat sStat;                 /* fstat() info for database file */
-
-    /* Call fstat() to figure out the permissions on the database file. If
-    ** a new *-shm file is created, an attempt will be made to create it
-    ** with the same permissions.
-    */
-    if( osFstat(pDbFd->h, &sStat) && pInode->bProcessLock==0 ){
-      rc = SQLITE_IOERR_FSTAT;
-      goto shm_open_err;
-    }
-
-#ifdef SQLITE_SHM_DIRECTORY
-    nShmFilename = sizeof(SQLITE_SHM_DIRECTORY) + 31;
-#else
-    nShmFilename = 6 + (int)strlen(pDbFd->zPath);
-#endif
-    pShmNode = sqlite3_malloc( sizeof(*pShmNode) + nShmFilename );
-    if( pShmNode==0 ){
-      rc = SQLITE_NOMEM;
-      goto shm_open_err;
-    }
-    memset(pShmNode, 0, sizeof(*pShmNode)+nShmFilename);
-    zShmFilename = pShmNode->zFilename = (char*)&pShmNode[1];
-#ifdef SQLITE_SHM_DIRECTORY
-    sqlite3_snprintf(nShmFilename, zShmFilename, 
-                     SQLITE_SHM_DIRECTORY "/sqlite-shm-%x-%x",
-                     (u32)sStat.st_ino, (u32)sStat.st_dev);
-#else
-    sqlite3_snprintf(nShmFilename, zShmFilename, "%s-shm", pDbFd->zPath);
-    sqlite3FileSuffix3(pDbFd->zPath, zShmFilename);
-#endif
-    pShmNode->h = -1;
-    pDbFd->pInode->pShmNode = pShmNode;
-    pShmNode->pInode = pDbFd->pInode;
-    pShmNode->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
-    if( pShmNode->mutex==0 ){
-      rc = SQLITE_NOMEM;
-      goto shm_open_err;
-    }
-
-    if( pInode->bProcessLock==0 ){
-      int openFlags = O_RDWR | O_CREAT;
-      if( sqlite3_uri_boolean(pDbFd->zPath, "readonly_shm", 0) ){
-        openFlags = O_RDONLY;
-        pShmNode->isReadonly = 1;
-      }
-      pShmNode->h = robust_open(zShmFilename, openFlags, (sStat.st_mode&0777));
-      if( pShmNode->h<0 ){
-        rc = unixLogError(SQLITE_CANTOPEN_BKPT, "open", zShmFilename);
-        goto shm_open_err;
-      }
-
-      /* If this process is running as root, make sure that the SHM file
-      ** is owned by the same user that owns the original database.  Otherwise,
-      ** the original owner will not be able to connect.
-      */
-      osFchown(pShmNode->h, sStat.st_uid, sStat.st_gid);
-  
-      /* Check to see if another process is holding the dead-man switch.
-      ** If not, truncate the file to zero length. 
-      */
-      rc = SQLITE_OK;
-      if( unixShmSystemLock(pShmNode, F_WRLCK, UNIX_SHM_DMS, 1)==SQLITE_OK ){
-        if( robust_ftruncate(pShmNode->h, 0) ){
-          rc = unixLogError(SQLITE_IOERR_SHMOPEN, "ftruncate", zShmFilename);
-        }
-      }
-      if( rc==SQLITE_OK ){
-        rc = unixShmSystemLock(pShmNode, F_RDLCK, UNIX_SHM_DMS, 1);
-      }
-      if( rc ) goto shm_open_err;
-    }
-  }
-
-  /* Make the new connection a child of the unixShmNode */
-  p->pShmNode = pShmNode;
-#ifdef SQLITE_DEBUG
-  p->id = pShmNode->nextShmId++;
-#endif
-  pShmNode->nRef++;
-  pDbFd->pShm = p;
-  unixLeaveMutex();
-
-  /* The reference count on pShmNode has already been incremented under
-  ** the cover of the unixEnterMutex() mutex and the pointer from the
-  ** new (struct unixShm) object to the pShmNode has been set. All that is
-  ** left to do is to link the new object into the linked list starting
-  ** at pShmNode->pFirst. This must be done while holding the pShmNode->mutex 
-  ** mutex.
-  */
-  sqlite3_mutex_enter(pShmNode->mutex);
-  p->pNext = pShmNode->pFirst;
-  pShmNode->pFirst = p;
-  sqlite3_mutex_leave(pShmNode->mutex);
-  return SQLITE_OK;
-
-  /* Jump here on any error */
-shm_open_err:
-  unixShmPurge(pDbFd);       /* This call frees pShmNode if required */
-  sqlite3_free(p);
-  unixLeaveMutex();
-  return rc;
-}
-
-/*
-** This function is called to obtain a pointer to region iRegion of the 
-** shared-memory associated with the database file fd. Shared-memory regions 
-** are numbered starting from zero. Each shared-memory region is szRegion 
-** bytes in size.
-**
-** If an error occurs, an error code is returned and *pp is set to NULL.
-**
-** Otherwise, if the bExtend parameter is 0 and the requested shared-memory
-** region has not been allocated (by any client, including one running in a
-** separate process), then *pp is set to NULL and SQLITE_OK returned. If 
-** bExtend is non-zero and the requested shared-memory region has not yet 
-** been allocated, it is allocated by this function.
-**
-** If the shared-memory region has already been allocated or is allocated by
-** this call as described above, then it is mapped into this processes 
-** address space (if it is not already), *pp is set to point to the mapped 
-** memory and SQLITE_OK returned.
-*/
-static int unixShmMap(
-  sqlite3_file *fd,               /* Handle open on database file */
-  int iRegion,                    /* Region to retrieve */
-  int szRegion,                   /* Size of regions */
-  int bExtend,                    /* True to extend file if necessary */
-  void volatile **pp              /* OUT: Mapped memory */
-){
-  unixFile *pDbFd = (unixFile*)fd;
-  unixShm *p;
-  unixShmNode *pShmNode;
-  int rc = SQLITE_OK;
-  int nShmPerMap = unixShmRegionPerMap();
-  int nReqRegion;
-
-  /* If the shared-memory file has not yet been opened, open it now. */
-  if( pDbFd->pShm==0 ){
-    rc = unixOpenSharedMemory(pDbFd);
-    if( rc!=SQLITE_OK ) return rc;
-  }
-
-  p = pDbFd->pShm;
-  pShmNode = p->pShmNode;
-  sqlite3_mutex_enter(pShmNode->mutex);
-  assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
-  assert( pShmNode->pInode==pDbFd->pInode );
-  assert( pShmNode->h>=0 || pDbFd->pInode->bProcessLock==1 );
-  assert( pShmNode->h<0 || pDbFd->pInode->bProcessLock==0 );
-
-  /* Minimum number of regions required to be mapped. */
-  nReqRegion = ((iRegion+nShmPerMap) / nShmPerMap) * nShmPerMap;
-
-  if( pShmNode->nRegion<nReqRegion ){
-    char **apNew;                      /* New apRegion[] array */
-    int nByte = nReqRegion*szRegion;   /* Minimum required file size */
-    struct stat sStat;                 /* Used by fstat() */
-
-    pShmNode->szRegion = szRegion;
-
-    if( pShmNode->h>=0 ){
-      /* The requested region is not mapped into this processes address space.
-      ** Check to see if it has been allocated (i.e. if the wal-index file is
-      ** large enough to contain the requested region).
-      */
-      if( osFstat(pShmNode->h, &sStat) ){
-        rc = SQLITE_IOERR_SHMSIZE;
-        goto shmpage_out;
-      }
-  
-      if( sStat.st_size<nByte ){
-        /* The requested memory region does not exist. If bExtend is set to
-        ** false, exit early. *pp will be set to NULL and SQLITE_OK returned.
-        */
-        if( !bExtend ){
-          goto shmpage_out;
-        }
-
-        /* Alternatively, if bExtend is true, extend the file. Do this by
-        ** writing a single byte to the end of each (OS) page being
-        ** allocated or extended. Technically, we need only write to the
-        ** last page in order to extend the file. But writing to all new
-        ** pages forces the OS to allocate them immediately, which reduces
-        ** the chances of SIGBUS while accessing the mapped region later on.
-        */
-        else{
-          static const int pgsz = 4096;
-          int iPg;
-
-          /* Write to the last byte of each newly allocated or extended page */
-          assert( (nByte % pgsz)==0 );
-          for(iPg=(sStat.st_size/pgsz); iPg<(nByte/pgsz); iPg++){
-            if( seekAndWriteFd(pShmNode->h, iPg*pgsz + pgsz-1, "", 1, 0)!=1 ){
-              const char *zFile = pShmNode->zFilename;
-              rc = unixLogError(SQLITE_IOERR_SHMSIZE, "write", zFile);
-              goto shmpage_out;
-            }
-          }
-        }
-      }
-    }
-
-    /* Map the requested memory region into this processes address space. */
-    apNew = (char **)sqlite3_realloc(
-        pShmNode->apRegion, nReqRegion*sizeof(char *)
-    );
-    if( !apNew ){
-      rc = SQLITE_IOERR_NOMEM;
-      goto shmpage_out;
-    }
-    pShmNode->apRegion = apNew;
-    while( pShmNode->nRegion<nReqRegion ){
-      int nMap = szRegion*nShmPerMap;
-      int i;
-      void *pMem;
-      if( pShmNode->h>=0 ){
-        pMem = osMmap(0, nMap,
-            pShmNode->isReadonly ? PROT_READ : PROT_READ|PROT_WRITE, 
-            MAP_SHARED, pShmNode->h, szRegion*(i64)pShmNode->nRegion
-        );
-        if( pMem==MAP_FAILED ){
-          rc = unixLogError(SQLITE_IOERR_SHMMAP, "mmap", pShmNode->zFilename);
-          goto shmpage_out;
-        }
-      }else{
-        pMem = sqlite3_malloc(szRegion);
-        if( pMem==0 ){
-          rc = SQLITE_NOMEM;
-          goto shmpage_out;
-        }
-        memset(pMem, 0, szRegion);
-      }
-
-      for(i=0; i<nShmPerMap; i++){
-        pShmNode->apRegion[pShmNode->nRegion+i] = &((char*)pMem)[szRegion*i];
-      }
-      pShmNode->nRegion += nShmPerMap;
-    }
-  }
-
-shmpage_out:
-  if( pShmNode->nRegion>iRegion ){
-    *pp = pShmNode->apRegion[iRegion];
-  }else{
-    *pp = 0;
-  }
-  if( pShmNode->isReadonly && rc==SQLITE_OK ) rc = SQLITE_READONLY;
-  sqlite3_mutex_leave(pShmNode->mutex);
-  return rc;
-}
-
-/*
-** Change the lock state for a shared-memory segment.
-**
-** Note that the relationship between SHAREd and EXCLUSIVE locks is a little
-** different here than in posix.  In xShmLock(), one can go from unlocked
-** to shared and back or from unlocked to exclusive and back.  But one may
-** not go from shared to exclusive or from exclusive to shared.
-*/
-static int unixShmLock(
-  sqlite3_file *fd,          /* Database file holding the shared memory */
-  int ofst,                  /* First lock to acquire or release */
-  int n,                     /* Number of locks to acquire or release */
-  int flags                  /* What to do with the lock */
-){
-  unixFile *pDbFd = (unixFile*)fd;      /* Connection holding shared memory */
-  unixShm *p = pDbFd->pShm;             /* The shared memory being locked */
-  unixShm *pX;                          /* For looping over all siblings */
-  unixShmNode *pShmNode = p->pShmNode;  /* The underlying file iNode */
-  int rc = SQLITE_OK;                   /* Result code */
-  u16 mask;                             /* Mask of locks to take or release */
-
-  assert( pShmNode==pDbFd->pInode->pShmNode );
-  assert( pShmNode->pInode==pDbFd->pInode );
-  assert( ofst>=0 && ofst+n<=SQLITE_SHM_NLOCK );
-  assert( n>=1 );
-  assert( flags==(SQLITE_SHM_LOCK | SQLITE_SHM_SHARED)
-       || flags==(SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE)
-       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED)
-       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE) );
-  assert( n==1 || (flags & SQLITE_SHM_EXCLUSIVE)!=0 );
-  assert( pShmNode->h>=0 || pDbFd->pInode->bProcessLock==1 );
-  assert( pShmNode->h<0 || pDbFd->pInode->bProcessLock==0 );
-
-  mask = (1<<(ofst+n)) - (1<<ofst);
-  assert( n>1 || mask==(1<<ofst) );
-  sqlite3_mutex_enter(pShmNode->mutex);
-  if( flags & SQLITE_SHM_UNLOCK ){
-    u16 allMask = 0; /* Mask of locks held by siblings */
-
-    /* See if any siblings hold this same lock */
-    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
-      if( pX==p ) continue;
-      assert( (pX->exclMask & (p->exclMask|p->sharedMask))==0 );
-      allMask |= pX->sharedMask;
-    }
-
-    /* Unlock the system-level locks */
-    if( (mask & allMask)==0 ){
-      rc = unixShmSystemLock(pShmNode, F_UNLCK, ofst+UNIX_SHM_BASE, n);
-    }else{
-      rc = SQLITE_OK;
-    }
-
-    /* Undo the local locks */
-    if( rc==SQLITE_OK ){
-      p->exclMask &= ~mask;
-      p->sharedMask &= ~mask;
-    } 
-  }else if( flags & SQLITE_SHM_SHARED ){
-    u16 allShared = 0;  /* Union of locks held by connections other than "p" */
-
-    /* Find out which shared locks are already held by sibling connections.
-    ** If any sibling already holds an exclusive lock, go ahead and return
-    ** SQLITE_BUSY.
-    */
-    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
-      if( (pX->exclMask & mask)!=0 ){
-        rc = SQLITE_BUSY;
-        break;
-      }
-      allShared |= pX->sharedMask;
-    }
-
-    /* Get shared locks at the system level, if necessary */
-    if( rc==SQLITE_OK ){
-      if( (allShared & mask)==0 ){
-        rc = unixShmSystemLock(pShmNode, F_RDLCK, ofst+UNIX_SHM_BASE, n);
-      }else{
-        rc = SQLITE_OK;
-      }
-    }
-
-    /* Get the local shared locks */
-    if( rc==SQLITE_OK ){
-      p->sharedMask |= mask;
-    }
-  }else{
-    /* Make sure no sibling connections hold locks that will block this
-    ** lock.  If any do, return SQLITE_BUSY right away.
-    */
-    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
-      if( (pX->exclMask & mask)!=0 || (pX->sharedMask & mask)!=0 ){
-        rc = SQLITE_BUSY;
-        break;
-      }
-    }
-  
-    /* Get the exclusive locks at the system level.  Then if successful
-    ** also mark the local connection as being locked.
-    */
-    if( rc==SQLITE_OK ){
-      rc = unixShmSystemLock(pShmNode, F_WRLCK, ofst+UNIX_SHM_BASE, n);
-      if( rc==SQLITE_OK ){
-        assert( (p->sharedMask & mask)==0 );
-        p->exclMask |= mask;
-      }
-    }
-  }
-  sqlite3_mutex_leave(pShmNode->mutex);
-  OSTRACE(("SHM-LOCK shmid-%d, pid-%d got %03x,%03x\n",
-           p->id, getpid(), p->sharedMask, p->exclMask));
-  return rc;
-}
-
-/*
-** Implement a memory barrier or memory fence on shared memory.  
-**
-** All loads and stores begun before the barrier must complete before
-** any load or store begun after the barrier.
-*/
-static void unixShmBarrier(
-  sqlite3_file *fd                /* Database file holding the shared memory */
-){
-  UNUSED_PARAMETER(fd);
-  unixEnterMutex();
-  unixLeaveMutex();
-}
-
-/*
-** Close a connection to shared-memory.  Delete the underlying 
-** storage if deleteFlag is true.
-**
-** If there is no shared memory associated with the connection then this
-** routine is a harmless no-op.
-*/
-static int unixShmUnmap(
-  sqlite3_file *fd,               /* The underlying database file */
-  int deleteFlag                  /* Delete shared-memory if true */
-){
-  unixShm *p;                     /* The connection to be closed */
-  unixShmNode *pShmNode;          /* The underlying shared-memory file */
-  unixShm **pp;                   /* For looping over sibling connections */
-  unixFile *pDbFd;                /* The underlying database file */
-
-  pDbFd = (unixFile*)fd;
-  p = pDbFd->pShm;
-  if( p==0 ) return SQLITE_OK;
-  pShmNode = p->pShmNode;
-
-  assert( pShmNode==pDbFd->pInode->pShmNode );
-  assert( pShmNode->pInode==pDbFd->pInode );
-
-  /* Remove connection p from the set of connections associated
-  ** with pShmNode */
-  sqlite3_mutex_enter(pShmNode->mutex);
-  for(pp=&pShmNode->pFirst; (*pp)!=p; pp = &(*pp)->pNext){}
-  *pp = p->pNext;
-
-  /* Free the connection p */
-  sqlite3_free(p);
-  pDbFd->pShm = 0;
-  sqlite3_mutex_leave(pShmNode->mutex);
-
-  /* If pShmNode->nRef has reached 0, then close the underlying
-  ** shared-memory file, too */
-  unixEnterMutex();
-  assert( pShmNode->nRef>0 );
-  pShmNode->nRef--;
-  if( pShmNode->nRef==0 ){
-    if( deleteFlag && pShmNode->h>=0 ) osUnlink(pShmNode->zFilename);
-    unixShmPurge(pDbFd);
-  }
-  unixLeaveMutex();
-
-  return SQLITE_OK;
-}
-
-
-#else
-# define unixShmMap     0
-# define unixShmLock    0
-# define unixShmBarrier 0
-# define unixShmUnmap   0
-#endif /* #ifndef SQLITE_OMIT_WAL */
-
-#if SQLITE_MAX_MMAP_SIZE>0
-/*
-** If it is currently memory mapped, unmap file pFd.
-*/
-static void unixUnmapfile(unixFile *pFd){
-  assert( pFd->nFetchOut==0 );
-  if( pFd->pMapRegion ){
-    osMunmap(pFd->pMapRegion, pFd->mmapSizeActual);
-    pFd->pMapRegion = 0;
-    pFd->mmapSize = 0;
-    pFd->mmapSizeActual = 0;
-  }
-}
-
-/*
-** Attempt to set the size of the memory mapping maintained by file 
-** descriptor pFd to nNew bytes. Any existing mapping is discarded.
-**
-** If successful, this function sets the following variables:
-**
-**       unixFile.pMapRegion
-**       unixFile.mmapSize
-**       unixFile.mmapSizeActual
-**
-** If unsuccessful, an error message is logged via sqlite3_log() and
-** the three variables above are zeroed. In this case SQLite should
-** continue accessing the database using the xRead() and xWrite()
-** methods.
-*/
-static void unixRemapfile(
-  unixFile *pFd,                  /* File descriptor object */
-  i64 nNew                        /* Required mapping size */
-){
-  const char *zErr = "mmap";
-  int h = pFd->h;                      /* File descriptor open on db file */
-  u8 *pOrig = (u8 *)pFd->pMapRegion;   /* Pointer to current file mapping */
-  i64 nOrig = pFd->mmapSizeActual;     /* Size of pOrig region in bytes */
-  u8 *pNew = 0;                        /* Location of new mapping */
-  int flags = PROT_READ;               /* Flags to pass to mmap() */
-
-  assert( pFd->nFetchOut==0 );
-  assert( nNew>pFd->mmapSize );
-  assert( nNew<=pFd->mmapSizeMax );
-  assert( nNew>0 );
-  assert( pFd->mmapSizeActual>=pFd->mmapSize );
-  assert( MAP_FAILED!=0 );
-
-  if( (pFd->ctrlFlags & UNIXFILE_RDONLY)==0 ) flags |= PROT_WRITE;
-
-  if( pOrig ){
-#if HAVE_MREMAP
-    i64 nReuse = pFd->mmapSize;
-#else
-    const int szSyspage = osGetpagesize();
-    i64 nReuse = (pFd->mmapSize & ~(szSyspage-1));
-#endif
-    u8 *pReq = &pOrig[nReuse];
-
-    /* Unmap any pages of the existing mapping that cannot be reused. */
-    if( nReuse!=nOrig ){
-      osMunmap(pReq, nOrig-nReuse);
-    }
-
-#if HAVE_MREMAP
-    pNew = osMremap(pOrig, nReuse, nNew, MREMAP_MAYMOVE);
-    zErr = "mremap";
-#else
-    pNew = osMmap(pReq, nNew-nReuse, flags, MAP_SHARED, h, nReuse);
-    if( pNew!=MAP_FAILED ){
-      if( pNew!=pReq ){
-        osMunmap(pNew, nNew - nReuse);
-        pNew = 0;
-      }else{
-        pNew = pOrig;
-      }
-    }
-#endif
-
-    /* The attempt to extend the existing mapping failed. Free it. */
-    if( pNew==MAP_FAILED || pNew==0 ){
-      osMunmap(pOrig, nReuse);
-    }
-  }
-
-  /* If pNew is still NULL, try to create an entirely new mapping. */
-  if( pNew==0 ){
-    pNew = osMmap(0, nNew, flags, MAP_SHARED, h, 0);
-  }
-
-  if( pNew==MAP_FAILED ){
-    pNew = 0;
-    nNew = 0;
-    unixLogError(SQLITE_OK, zErr, pFd->zPath);
-
-    /* If the mmap() above failed, assume that all subsequent mmap() calls
-    ** will probably fail too. Fall back to using xRead/xWrite exclusively
-    ** in this case.  */
-    pFd->mmapSizeMax = 0;
-  }
-  pFd->pMapRegion = (void *)pNew;
-  pFd->mmapSize = pFd->mmapSizeActual = nNew;
-}
-
-/*
-** Memory map or remap the file opened by file-descriptor pFd (if the file
-** is already mapped, the existing mapping is replaced by the new). Or, if 
-** there already exists a mapping for this file, and there are still 
-** outstanding xFetch() references to it, this function is a no-op.
-**
-** If parameter nByte is non-negative, then it is the requested size of 
-** the mapping to create. Otherwise, if nByte is less than zero, then the 
-** requested size is the size of the file on disk. The actual size of the
-** created mapping is either the requested size or the value configured 
-** using SQLITE_FCNTL_MMAP_LIMIT, whichever is smaller.
-**
-** SQLITE_OK is returned if no error occurs (even if the mapping is not
-** recreated as a result of outstanding references) or an SQLite error
-** code otherwise.
-*/
-static int unixMapfile(unixFile *pFd, i64 nByte){
-  i64 nMap = nByte;
-  int rc;
-
-  assert( nMap>=0 || pFd->nFetchOut==0 );
-  if( pFd->nFetchOut>0 ) return SQLITE_OK;
-
-  if( nMap<0 ){
-    struct stat statbuf;          /* Low-level file information */
-    rc = osFstat(pFd->h, &statbuf);
-    if( rc!=SQLITE_OK ){
-      return SQLITE_IOERR_FSTAT;
-    }
-    nMap = statbuf.st_size;
-  }
-  if( nMap>pFd->mmapSizeMax ){
-    nMap = pFd->mmapSizeMax;
-  }
-
-  if( nMap!=pFd->mmapSize ){
-    if( nMap>0 ){
-      unixRemapfile(pFd, nMap);
-    }else{
-      unixUnmapfile(pFd);
-    }
-  }
-
-  return SQLITE_OK;
-}
-#endif /* SQLITE_MAX_MMAP_SIZE>0 */
-
-/*
-** If possible, return a pointer to a mapping of file fd starting at offset
-** iOff. The mapping must be valid for at least nAmt bytes.
-**
-** If such a pointer can be obtained, store it in *pp and return SQLITE_OK.
-** Or, if one cannot but no error occurs, set *pp to 0 and return SQLITE_OK.
-** Finally, if an error does occur, return an SQLite error code. The final
-** value of *pp is undefined in this case.
-**
-** If this function does return a pointer, the caller must eventually 
-** release the reference by calling unixUnfetch().
-*/
-static int unixFetch(sqlite3_file *fd, i64 iOff, int nAmt, void **pp){
-#if SQLITE_MAX_MMAP_SIZE>0
-  unixFile *pFd = (unixFile *)fd;   /* The underlying database file */
-#endif
-  *pp = 0;
-
-#if SQLITE_MAX_MMAP_SIZE>0
-  if( pFd->mmapSizeMax>0 ){
-    if( pFd->pMapRegion==0 ){
-      int rc = unixMapfile(pFd, -1);
-      if( rc!=SQLITE_OK ) return rc;
-    }
-    if( pFd->mmapSize >= iOff+nAmt ){
-      *pp = &((u8 *)pFd->pMapRegion)[iOff];
-      pFd->nFetchOut++;
-    }
-  }
-#endif
-  return SQLITE_OK;
-}
-
-/*
-** If the third argument is non-NULL, then this function releases a 
-** reference obtained by an earlier call to unixFetch(). The second
-** argument passed to this function must be the same as the corresponding
-** argument that was passed to the unixFetch() invocation. 
-**
-** Or, if the third argument is NULL, then this function is being called 
-** to inform the VFS layer that, according to POSIX, any existing mapping 
-** may now be invalid and should be unmapped.
-*/
-static int unixUnfetch(sqlite3_file *fd, i64 iOff, void *p){
-#if SQLITE_MAX_MMAP_SIZE>0
-  unixFile *pFd = (unixFile *)fd;   /* The underlying database file */
-  UNUSED_PARAMETER(iOff);
-
-  /* If p==0 (unmap the entire file) then there must be no outstanding 
-  ** xFetch references. Or, if p!=0 (meaning it is an xFetch reference),
-  ** then there must be at least one outstanding.  */
-  assert( (p==0)==(pFd->nFetchOut==0) );
-
-  /* If p!=0, it must match the iOff value. */
-  assert( p==0 || p==&((u8 *)pFd->pMapRegion)[iOff] );
-
-  if( p ){
-    pFd->nFetchOut--;
-  }else{
-    unixUnmapfile(pFd);
-  }
-
-  assert( pFd->nFetchOut>=0 );
-#else
-  UNUSED_PARAMETER(fd);
-  UNUSED_PARAMETER(p);
-  UNUSED_PARAMETER(iOff);
-#endif
-  return SQLITE_OK;
-}
-
-/*
-** Here ends the implementation of all sqlite3_file methods.
-**
-********************** End sqlite3_file Methods *******************************
-******************************************************************************/
-
-/*
-** This division contains definitions of sqlite3_io_methods objects that
-** implement various file locking strategies.  It also contains definitions
-** of "finder" functions.  A finder-function is used to locate the appropriate
-** sqlite3_io_methods object for a particular database file.  The pAppData
-** field of the sqlite3_vfs VFS objects are initialized to be pointers to
-** the correct finder-function for that VFS.
-**
-** Most finder functions return a pointer to a fixed sqlite3_io_methods
-** object.  The only interesting finder-function is autolockIoFinder, which
-** looks at the filesystem type and tries to guess the best locking
-** strategy from that.
-**
-** For finder-function F, two objects are created:
-**
-**    (1) The real finder-function named "FImpt()".
-**
-**    (2) A constant pointer to this function named just "F".
-**
-**
-** A pointer to the F pointer is used as the pAppData value for VFS
-** objects.  We have to do this instead of letting pAppData point
-** directly at the finder-function since C90 rules prevent a void*
-** from be cast into a function pointer.
-**
-**
-** Each instance of this macro generates two objects:
-**
-**   *  A constant sqlite3_io_methods object call METHOD that has locking
-**      methods CLOSE, LOCK, UNLOCK, CKRESLOCK.
-**
-**   *  An I/O method finder function called FINDER that returns a pointer
-**      to the METHOD object in the previous bullet.
-*/
-#define IOMETHODS(FINDER, METHOD, VERSION, CLOSE, LOCK, UNLOCK, CKLOCK, SHMMAP) \
-static const sqlite3_io_methods METHOD = {                                   \
-   VERSION,                    /* iVersion */                                \
-   CLOSE,                      /* xClose */                                  \
-   unixRead,                   /* xRead */                                   \
-   unixWrite,                  /* xWrite */                                  \
-   unixTruncate,               /* xTruncate */                               \
-   unixSync,                   /* xSync */                                   \
-   unixFileSize,               /* xFileSize */                               \
-   LOCK,                       /* xLock */                                   \
-   UNLOCK,                     /* xUnlock */                                 \
-   CKLOCK,                     /* xCheckReservedLock */                      \
-   unixFileControl,            /* xFileControl */                            \
-   unixSectorSize,             /* xSectorSize */                             \
-   unixDeviceCharacteristics,  /* xDeviceCapabilities */                     \
-   SHMMAP,                     /* xShmMap */                                 \
-   unixShmLock,                /* xShmLock */                                \
-   unixShmBarrier,             /* xShmBarrier */                             \
-   unixShmUnmap,               /* xShmUnmap */                               \
-   unixFetch,                  /* xFetch */                                  \
-   unixUnfetch,                /* xUnfetch */                                \
-};                                                                           \
-static const sqlite3_io_methods *FINDER##Impl(const char *z, unixFile *p){   \
-  UNUSED_PARAMETER(z); UNUSED_PARAMETER(p);                                  \
-  return &METHOD;                                                            \
-}                                                                            \
-static const sqlite3_io_methods *(*const FINDER)(const char*,unixFile *p)    \
-    = FINDER##Impl;
-
-/*
-** Here are all of the sqlite3_io_methods objects for each of the
-** locking strategies.  Functions that return pointers to these methods
-** are also created.
-*/
-IOMETHODS(
-  posixIoFinder,            /* Finder function name */
-  posixIoMethods,           /* sqlite3_io_methods object name */
-  3,                        /* shared memory and mmap are enabled */
-  unixClose,                /* xClose method */
-  unixLock,                 /* xLock method */
-  unixUnlock,               /* xUnlock method */
-  unixCheckReservedLock,    /* xCheckReservedLock method */
-  unixShmMap                /* xShmMap method */
-)
-IOMETHODS(
-  nolockIoFinder,           /* Finder function name */
-  nolockIoMethods,          /* sqlite3_io_methods object name */
-  3,                        /* shared memory is disabled */
-  nolockClose,              /* xClose method */
-  nolockLock,               /* xLock method */
-  nolockUnlock,             /* xUnlock method */
-  nolockCheckReservedLock,  /* xCheckReservedLock method */
-  0                         /* xShmMap method */
-)
-IOMETHODS(
-  dotlockIoFinder,          /* Finder function name */
-  dotlockIoMethods,         /* sqlite3_io_methods object name */
-  1,                        /* shared memory is disabled */
-  dotlockClose,             /* xClose method */
-  dotlockLock,              /* xLock method */
-  dotlockUnlock,            /* xUnlock method */
-  dotlockCheckReservedLock, /* xCheckReservedLock method */
-  0                         /* xShmMap method */
-)
-
-#if SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORKS
-IOMETHODS(
-  flockIoFinder,            /* Finder function name */
-  flockIoMethods,           /* sqlite3_io_methods object name */
-  1,                        /* shared memory is disabled */
-  flockClose,               /* xClose method */
-  flockLock,                /* xLock method */
-  flockUnlock,              /* xUnlock method */
-  flockCheckReservedLock,   /* xCheckReservedLock method */
-  0                         /* xShmMap method */
-)
-#endif
-
-#if OS_VXWORKS
-IOMETHODS(
-  semIoFinder,              /* Finder function name */
-  semIoMethods,             /* sqlite3_io_methods object name */
-  1,                        /* shared memory is disabled */
-  semClose,                 /* xClose method */
-  semLock,                  /* xLock method */
-  semUnlock,                /* xUnlock method */
-  semCheckReservedLock,     /* xCheckReservedLock method */
-  0                         /* xShmMap method */
-)
-#endif
-
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-IOMETHODS(
-  afpIoFinder,              /* Finder function name */
-  afpIoMethods,             /* sqlite3_io_methods object name */
-  1,                        /* shared memory is disabled */
-  afpClose,                 /* xClose method */
-  afpLock,                  /* xLock method */
-  afpUnlock,                /* xUnlock method */
-  afpCheckReservedLock,     /* xCheckReservedLock method */
-  0                         /* xShmMap method */
-)
-#endif
-
-/*
-** The proxy locking method is a "super-method" in the sense that it
-** opens secondary file descriptors for the conch and lock files and
-** it uses proxy, dot-file, AFP, and flock() locking methods on those
-** secondary files.  For this reason, the division that implements
-** proxy locking is located much further down in the file.  But we need
-** to go ahead and define the sqlite3_io_methods and finder function
-** for proxy locking here.  So we forward declare the I/O methods.
-*/
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-static int proxyClose(sqlite3_file*);
-static int proxyLock(sqlite3_file*, int);
-static int proxyUnlock(sqlite3_file*, int);
-static int proxyCheckReservedLock(sqlite3_file*, int*);
-IOMETHODS(
-  proxyIoFinder,            /* Finder function name */
-  proxyIoMethods,           /* sqlite3_io_methods object name */
-  1,                        /* shared memory is disabled */
-  proxyClose,               /* xClose method */
-  proxyLock,                /* xLock method */
-  proxyUnlock,              /* xUnlock method */
-  proxyCheckReservedLock,   /* xCheckReservedLock method */
-  0                         /* xShmMap method */
-)
-#endif
-
-/* nfs lockd on OSX 10.3+ doesn't clear write locks when a read lock is set */
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-IOMETHODS(
-  nfsIoFinder,               /* Finder function name */
-  nfsIoMethods,              /* sqlite3_io_methods object name */
-  1,                         /* shared memory is disabled */
-  unixClose,                 /* xClose method */
-  unixLock,                  /* xLock method */
-  nfsUnlock,                 /* xUnlock method */
-  unixCheckReservedLock,     /* xCheckReservedLock method */
-  0                          /* xShmMap method */
-)
-#endif
-
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-/* 
-** This "finder" function attempts to determine the best locking strategy 
-** for the database file "filePath".  It then returns the sqlite3_io_methods
-** object that implements that strategy.
-**
-** This is for MacOSX only.
-*/
-static const sqlite3_io_methods *autolockIoFinderImpl(
-  const char *filePath,    /* name of the database file */
-  unixFile *pNew           /* open file object for the database file */
-){
-  static const struct Mapping {
-    const char *zFilesystem;              /* Filesystem type name */
-    const sqlite3_io_methods *pMethods;   /* Appropriate locking method */
-  } aMap[] = {
-    { "hfs",    &posixIoMethods },
-    { "ufs",    &posixIoMethods },
-    { "afpfs",  &afpIoMethods },
-    { "smbfs",  &afpIoMethods },
-    { "webdav", &nolockIoMethods },
-    { 0, 0 }
-  };
-  int i;
-  struct statfs fsInfo;
-  struct flock lockInfo;
-
-  if( !filePath ){
-    /* If filePath==NULL that means we are dealing with a transient file
-    ** that does not need to be locked. */
-    return &nolockIoMethods;
-  }
-  if( statfs(filePath, &fsInfo) != -1 ){
-    if( fsInfo.f_flags & MNT_RDONLY ){
-      return &nolockIoMethods;
-    }
-    for(i=0; aMap[i].zFilesystem; i++){
-      if( strcmp(fsInfo.f_fstypename, aMap[i].zFilesystem)==0 ){
-        return aMap[i].pMethods;
-      }
-    }
-  }
-
-  /* Default case. Handles, amongst others, "nfs".
-  ** Test byte-range lock using fcntl(). If the call succeeds, 
-  ** assume that the file-system supports POSIX style locks. 
-  */
-  lockInfo.l_len = 1;
-  lockInfo.l_start = 0;
-  lockInfo.l_whence = SEEK_SET;
-  lockInfo.l_type = F_RDLCK;
-  if( osFcntl(pNew->h, F_GETLK, &lockInfo)!=-1 ) {
-    if( strcmp(fsInfo.f_fstypename, "nfs")==0 ){
-      return &nfsIoMethods;
-    } else {
-      return &posixIoMethods;
-    }
-  }else{
-    return &dotlockIoMethods;
-  }
-}
-static const sqlite3_io_methods 
-  *(*const autolockIoFinder)(const char*,unixFile*) = autolockIoFinderImpl;
-
-#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
-
-#if OS_VXWORKS && SQLITE_ENABLE_LOCKING_STYLE
-/* 
-** This "finder" function attempts to determine the best locking strategy 
-** for the database file "filePath".  It then returns the sqlite3_io_methods
-** object that implements that strategy.
-**
-** This is for VXWorks only.
-*/
-static const sqlite3_io_methods *autolockIoFinderImpl(
-  const char *filePath,    /* name of the database file */
-  unixFile *pNew           /* the open file object */
-){
-  struct flock lockInfo;
-
-  if( !filePath ){
-    /* If filePath==NULL that means we are dealing with a transient file
-    ** that does not need to be locked. */
-    return &nolockIoMethods;
-  }
-
-  /* Test if fcntl() is supported and use POSIX style locks.
-  ** Otherwise fall back to the named semaphore method.
-  */
-  lockInfo.l_len = 1;
-  lockInfo.l_start = 0;
-  lockInfo.l_whence = SEEK_SET;
-  lockInfo.l_type = F_RDLCK;
-  if( osFcntl(pNew->h, F_GETLK, &lockInfo)!=-1 ) {
-    return &posixIoMethods;
-  }else{
-    return &semIoMethods;
-  }
-}
-static const sqlite3_io_methods 
-  *(*const autolockIoFinder)(const char*,unixFile*) = autolockIoFinderImpl;
-
-#endif /* OS_VXWORKS && SQLITE_ENABLE_LOCKING_STYLE */
-
-/*
-** An abstract type for a pointer to an IO method finder function:
-*/
-typedef const sqlite3_io_methods *(*finder_type)(const char*,unixFile*);
-
-
-/****************************************************************************
-**************************** sqlite3_vfs methods ****************************
-**
-** This division contains the implementation of methods on the
-** sqlite3_vfs object.
-*/
-
-/*
-** Initialize the contents of the unixFile structure pointed to by pId.
-*/
-static int fillInUnixFile(
-  sqlite3_vfs *pVfs,      /* Pointer to vfs object */
-  int h,                  /* Open file descriptor of file being opened */
-  sqlite3_file *pId,      /* Write to the unixFile structure here */
-  const char *zFilename,  /* Name of the file being opened */
-  int ctrlFlags           /* Zero or more UNIXFILE_* values */
-){
-  const sqlite3_io_methods *pLockingStyle;
-  unixFile *pNew = (unixFile *)pId;
-  int rc = SQLITE_OK;
-
-  assert( pNew->pInode==NULL );
-
-  /* Usually the path zFilename should not be a relative pathname. The
-  ** exception is when opening the proxy "conch" file in builds that
-  ** include the special Apple locking styles.
-  */
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-  assert( zFilename==0 || zFilename[0]=='/' 
-    || pVfs->pAppData==(void*)&autolockIoFinder );
-#else
-  assert( zFilename==0 || zFilename[0]=='/' );
-#endif
-
-  /* No locking occurs in temporary files */
-  assert( zFilename!=0 || (ctrlFlags & UNIXFILE_NOLOCK)!=0 );
-
-  OSTRACE(("OPEN    %-3d %s\n", h, zFilename));
-  pNew->h = h;
-  pNew->pVfs = pVfs;
-  pNew->zPath = zFilename;
-  pNew->ctrlFlags = (u8)ctrlFlags;
-#if SQLITE_MAX_MMAP_SIZE>0
-  pNew->mmapSizeMax = sqlite3GlobalConfig.szMmap;
-#endif
-  if( sqlite3_uri_boolean(((ctrlFlags & UNIXFILE_URI) ? zFilename : 0),
-                           "psow", SQLITE_POWERSAFE_OVERWRITE) ){
-    pNew->ctrlFlags |= UNIXFILE_PSOW;
-  }
-  if( strcmp(pVfs->zName,"unix-excl")==0 ){
-    pNew->ctrlFlags |= UNIXFILE_EXCL;
-  }
-
-#if OS_VXWORKS
-  pNew->pId = vxworksFindFileId(zFilename);
-  if( pNew->pId==0 ){
-    ctrlFlags |= UNIXFILE_NOLOCK;
-    rc = SQLITE_NOMEM;
-  }
-#endif
-
-  if( ctrlFlags & UNIXFILE_NOLOCK ){
-    pLockingStyle = &nolockIoMethods;
-  }else{
-    pLockingStyle = (**(finder_type*)pVfs->pAppData)(zFilename, pNew);
-#if SQLITE_ENABLE_LOCKING_STYLE
-    /* Cache zFilename in the locking context (AFP and dotlock override) for
-    ** proxyLock activation is possible (remote proxy is based on db name)
-    ** zFilename remains valid until file is closed, to support */
-    pNew->lockingContext = (void*)zFilename;
-#endif
-  }
-
-  if( pLockingStyle == &posixIoMethods
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-    || pLockingStyle == &nfsIoMethods
-#endif
-  ){
-    unixEnterMutex();
-    rc = findInodeInfo(pNew, &pNew->pInode);
-    if( rc!=SQLITE_OK ){
-      /* If an error occurred in findInodeInfo(), close the file descriptor
-      ** immediately, before releasing the mutex. findInodeInfo() may fail
-      ** in two scenarios:
-      **
-      **   (a) A call to fstat() failed.
-      **   (b) A malloc failed.
-      **
-      ** Scenario (b) may only occur if the process is holding no other
-      ** file descriptors open on the same file. If there were other file
-      ** descriptors on this file, then no malloc would be required by
-      ** findInodeInfo(). If this is the case, it is quite safe to close
-      ** handle h - as it is guaranteed that no posix locks will be released
-      ** by doing so.
-      **
-      ** If scenario (a) caused the error then things are not so safe. The
-      ** implicit assumption here is that if fstat() fails, things are in
-      ** such bad shape that dropping a lock or two doesn't matter much.
-      */
-      robust_close(pNew, h, __LINE__);
-      h = -1;
-    }
-    unixLeaveMutex();
-  }
-
-#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
-  else if( pLockingStyle == &afpIoMethods ){
-    /* AFP locking uses the file path so it needs to be included in
-    ** the afpLockingContext.
-    */
-    afpLockingContext *pCtx;
-    pNew->lockingContext = pCtx = sqlite3_malloc( sizeof(*pCtx) );
-    if( pCtx==0 ){
-      rc = SQLITE_NOMEM;
-    }else{
-      /* NB: zFilename exists and remains valid until the file is closed
-      ** according to requirement F11141.  So we do not need to make a
-      ** copy of the filename. */
-      pCtx->dbPath = zFilename;
-      pCtx->reserved = 0;
-      srandomdev();
-      unixEnterMutex();
-      rc = findInodeInfo(pNew, &pNew->pInode);
-      if( rc!=SQLITE_OK ){
-        sqlite3_free(pNew->lockingContext);
-        robust_close(pNew, h, __LINE__);
-        h = -1;
-      }
-      unixLeaveMutex();        
-    }
-  }
-#endif
-
-  else if( pLockingStyle == &dotlockIoMethods ){
-    /* Dotfile locking uses the file path so it needs to be included in
-    ** the dotlockLockingContext 
-    */
-    char *zLockFile;
-    int nFilename;
-    assert( zFilename!=0 );
-    nFilename = (int)strlen(zFilename) + 6;
-    zLockFile = (char *)sqlite3_malloc(nFilename);
-    if( zLockFile==0 ){
-      rc = SQLITE_NOMEM;
-    }else{
-      sqlite3_snprintf(nFilename, zLockFile, "%s" DOTLOCK_SUFFIX, zFilename);
-    }
-    pNew->lockingContext = zLockFile;
-  }
-
-#if OS_VXWORKS
-  else if( pLockingStyle == &semIoMethods ){
-    /* Named semaphore locking uses the file path so it needs to be
-    ** included in the semLockingContext
-    */
-    unixEnterMutex();
-    rc = findInodeInfo(pNew, &pNew->pInode);
-    if( (rc==SQLITE_OK) && (pNew->pInode->pSem==NULL) ){
-      char *zSemName = pNew->pInode->aSemName;
-      int n;
-      sqlite3_snprintf(MAX_PATHNAME, zSemName, "/%s.sem",
-                       pNew->pId->zCanonicalName);
-      for( n=1; zSemName[n]; n++ )
-        if( zSemName[n]=='/' ) zSemName[n] = '_';
-      pNew->pInode->pSem = sem_open(zSemName, O_CREAT, 0666, 1);
-      if( pNew->pInode->pSem == SEM_FAILED ){
-        rc = SQLITE_NOMEM;
-        pNew->pInode->aSemName[0] = '\0';
-      }
-    }
-    unixLeaveMutex();
-  }
-#endif
-  
-  pNew->lastErrno = 0;
-#if OS_VXWORKS
-  if( rc!=SQLITE_OK ){
-    if( h>=0 ) robust_close(pNew, h, __LINE__);
-    h = -1;
-    osUnlink(zFilename);
-    pNew->ctrlFlags |= UNIXFILE_DELETE;
-  }
-#endif
-  if( rc!=SQLITE_OK ){
-    if( h>=0 ) robust_close(pNew, h, __LINE__);
-  }else{
-    pNew->pMethod = pLockingStyle;
-    OpenCounter(+1);
-    verifyDbFile(pNew);
-  }
-  return rc;
-}
-
-/*
-** Return the name of a directory in which to put temporary files.
-** If no suitable temporary file directory can be found, return NULL.
-*/
-static const char *unixTempFileDir(void){
-  static const char *azDirs[] = {
-     0,
-     0,
-     0,
-     "/var/tmp",
-     "/usr/tmp",
-     "/tmp",
-     0        /* List terminator */
-  };
-  unsigned int i;
-  struct stat buf;
-  const char *zDir = 0;
-
-  azDirs[0] = sqlite3_temp_directory;
-  if( !azDirs[1] ) azDirs[1] = getenv("SQLITE_TMPDIR");
-  if( !azDirs[2] ) azDirs[2] = getenv("TMPDIR");
-  for(i=0; i<sizeof(azDirs)/sizeof(azDirs[0]); zDir=azDirs[i++]){
-    if( zDir==0 ) continue;
-    if( osStat(zDir, &buf) ) continue;
-    if( !S_ISDIR(buf.st_mode) ) continue;
-    if( osAccess(zDir, 07) ) continue;
-    break;
-  }
-  return zDir;
-}
-
-/*
-** Create a temporary file name in zBuf.  zBuf must be allocated
-** by the calling process and must be big enough to hold at least
-** pVfs->mxPathname bytes.
-*/
-static int unixGetTempname(int nBuf, char *zBuf){
-  static const unsigned char zChars[] =
-    "abcdefghijklmnopqrstuvwxyz"
-    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-    "0123456789";
-  unsigned int i, j;
-  const char *zDir;
-
-  /* It's odd to simulate an io-error here, but really this is just
-  ** using the io-error infrastructure to test that SQLite handles this
-  ** function failing. 
-  */
-  SimulateIOError( return SQLITE_IOERR );
-
-  zDir = unixTempFileDir();
-  if( zDir==0 ) zDir = ".";
-
-  /* Check that the output buffer is large enough for the temporary file 
-  ** name. If it is not, return SQLITE_ERROR.
-  */
-  if( (strlen(zDir) + strlen(SQLITE_TEMP_FILE_PREFIX) + 18) >= (size_t)nBuf ){
-    return SQLITE_ERROR;
-  }
-
-  do{
-    sqlite3_snprintf(nBuf-18, zBuf, "%s/"SQLITE_TEMP_FILE_PREFIX, zDir);
-    j = (int)strlen(zBuf);
-    sqlite3_randomness(15, &zBuf[j]);
-    for(i=0; i<15; i++, j++){
-      zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ];
-    }
-    zBuf[j] = 0;
-    zBuf[j+1] = 0;
-  }while( osAccess(zBuf,0)==0 );
-  return SQLITE_OK;
-}
-
-#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
-/*
-** Routine to transform a unixFile into a proxy-locking unixFile.
-** Implementation in the proxy-lock division, but used by unixOpen()
-** if SQLITE_PREFER_PROXY_LOCKING is defined.
-*/
-static int proxyTransformUnixFile(unixFile*, const char*);
-#endif
-
-/*
-** Search for an unused file descriptor that was opened on the database 
-** file (not a journal or master-journal file) identified by pathname
-** zPath with SQLITE_OPEN_XXX flags matching those passed as the second
-** argument to this function.
-**
-** Such a file descriptor may exist if a database connection was closed
-** but the associated file descriptor could not be closed because some
-** other file descriptor open on the same file is holding a file-lock.
-** Refer to comments in the unixClose() function and the lengthy comment
-** describing "Posix Advisory Locking" at the start of this file for 
-** further details. Also, ticket #4018.
-**
-** If a suitable file descriptor is found, then it is returned. If no
-** such file descriptor is located, -1 is returned.
-*/
-static UnixUnusedFd *findReusableFd(const char *zPath, int flags){
-  UnixUnusedFd *pUnused = 0;
-
-  /* Do not search for an unused file descriptor on vxworks. Not because
-  ** vxworks would not benefit from the change (it might, we're not sure),
-  ** but because no way to test it is currently available. It is better 
-  ** not to risk breaking vxworks support for the sake of such an obscure 
-  ** feature.  */
-#if !OS_VXWORKS
-  struct stat sStat;                   /* Results of stat() call */
-
-  /* A stat() call may fail for various reasons. If this happens, it is
-  ** almost certain that an open() call on the same path will also fail.
-  ** For this reason, if an error occurs in the stat() call here, it is
-  ** ignored and -1 is returned. The caller will try to open a new file
-  ** descriptor on the same path, fail, and return an error to SQLite.
-  **
-  ** Even if a subsequent open() call does succeed, the consequences of
-  ** not searching for a reusable file descriptor are not dire.  */
-  if( 0==osStat(zPath, &sStat) ){
-    unixInodeInfo *pInode;
-
-    unixEnterMutex();
-    pInode = inodeList;
-    while( pInode && (pInode->fileId.dev!=sStat.st_dev
-                     || pInode->fileId.ino!=sStat.st_ino) ){
-       pInode = pInode->pNext;
-    }
-    if( pInode ){
-      UnixUnusedFd **pp;
-      for(pp=&pInode->pUnused; *pp && (*pp)->flags!=flags; pp=&((*pp)->pNext));
-      pUnused = *pp;
-      if( pUnused ){
-        *pp = pUnused->pNext;
-      }
-    }
-    unixLeaveMutex();
-  }
-#endif    /* if !OS_VXWORKS */
-  return pUnused;
-}
-
-/*
-** This function is called by unixOpen() to determine the unix permissions
-** to create new files with. If no error occurs, then SQLITE_OK is returned
-** and a value suitable for passing as the third argument to open(2) is
-** written to *pMode. If an IO error occurs, an SQLite error code is 
-** returned and the value of *pMode is not modified.
-**
-** In most cases, this routine sets *pMode to 0, which will become
-** an indication to robust_open() to create the file using
-** SQLITE_DEFAULT_FILE_PERMISSIONS adjusted by the umask.
-** But if the file being opened is a WAL or regular journal file, then 
-** this function queries the file-system for the permissions on the 
-** corresponding database file and sets *pMode to this value. Whenever 
-** possible, WAL and journal files are created using the same permissions 
-** as the associated database file.
-**
-** If the SQLITE_ENABLE_8_3_NAMES option is enabled, then the
-** original filename is unavailable.  But 8_3_NAMES is only used for
-** FAT filesystems and permissions do not matter there, so just use
-** the default permissions.
-*/
-static int findCreateFileMode(
-  const char *zPath,              /* Path of file (possibly) being created */
-  int flags,                      /* Flags passed as 4th argument to xOpen() */
-  mode_t *pMode,                  /* OUT: Permissions to open file with */
-  uid_t *pUid,                    /* OUT: uid to set on the file */
-  gid_t *pGid                     /* OUT: gid to set on the file */
-){
-  int rc = SQLITE_OK;             /* Return Code */
-  *pMode = 0;
-  *pUid = 0;
-  *pGid = 0;
-  if( flags & (SQLITE_OPEN_WAL|SQLITE_OPEN_MAIN_JOURNAL) ){
-    char zDb[MAX_PATHNAME+1];     /* Database file path */
-    int nDb;                      /* Number of valid bytes in zDb */
-    struct stat sStat;            /* Output of stat() on database file */
-
-    /* zPath is a path to a WAL or journal file. The following block derives
-    ** the path to the associated database file from zPath. This block handles
-    ** the following naming conventions:
-    **
-    **   "<path to db>-journal"
-    **   "<path to db>-wal"
-    **   "<path to db>-journalNN"
-    **   "<path to db>-walNN"
-    **
-    ** where NN is a decimal number. The NN naming schemes are 
-    ** used by the test_multiplex.c module.
-    */
-    nDb = sqlite3Strlen30(zPath) - 1; 
-#ifdef SQLITE_ENABLE_8_3_NAMES
-    while( nDb>0 && sqlite3Isalnum(zPath[nDb]) ) nDb--;
-    if( nDb==0 || zPath[nDb]!='-' ) return SQLITE_OK;
-#else
-    while( zPath[nDb]!='-' ){
-      assert( nDb>0 );
-      assert( zPath[nDb]!='\n' );
-      nDb--;
-    }
-#endif
-    memcpy(zDb, zPath, nDb);
-    zDb[nDb] = '\0';
-
-    if( 0==osStat(zDb, &sStat) ){
-      *pMode = sStat.st_mode & 0777;
-      *pUid = sStat.st_uid;
-      *pGid = sStat.st_gid;
-    }else{
-      rc = SQLITE_IOERR_FSTAT;
-    }
-  }else if( flags & SQLITE_OPEN_DELETEONCLOSE ){
-    *pMode = 0600;
-  }
-  return rc;
-}
-
-/*
-** Open the file zPath.
-** 
-** Previously, the SQLite OS layer used three functions in place of this
-** one:
-**
-**     sqlite3OsOpenReadWrite();
-**     sqlite3OsOpenReadOnly();
-**     sqlite3OsOpenExclusive();
-**
-** These calls correspond to the following combinations of flags:
-**
-**     ReadWrite() ->     (READWRITE | CREATE)
-**     ReadOnly()  ->     (READONLY) 
-**     OpenExclusive() -> (READWRITE | CREATE | EXCLUSIVE)
-**
-** The old OpenExclusive() accepted a boolean argument - "delFlag". If
-** true, the file was configured to be automatically deleted when the
-** file handle closed. To achieve the same effect using this new 
-** interface, add the DELETEONCLOSE flag to those specified above for 
-** OpenExclusive().
-*/
-static int unixOpen(
-  sqlite3_vfs *pVfs,           /* The VFS for which this is the xOpen method */
-  const char *zPath,           /* Pathname of file to be opened */
-  sqlite3_file *pFile,         /* The file descriptor to be filled in */
-  int flags,                   /* Input flags to control the opening */
-  int *pOutFlags               /* Output flags returned to SQLite core */
-){
-  unixFile *p = (unixFile *)pFile;
-  int fd = -1;                   /* File descriptor returned by open() */
-  int openFlags = 0;             /* Flags to pass to open() */
-  int eType = flags&0xFFFFFF00;  /* Type of file to open */
-  int noLock;                    /* True to omit locking primitives */
-  int rc = SQLITE_OK;            /* Function Return Code */
-  int ctrlFlags = 0;             /* UNIXFILE_* flags */
-
-  int isExclusive  = (flags & SQLITE_OPEN_EXCLUSIVE);
-  int isDelete     = (flags & SQLITE_OPEN_DELETEONCLOSE);
-  int isCreate     = (flags & SQLITE_OPEN_CREATE);
-  int isReadonly   = (flags & SQLITE_OPEN_READONLY);
-  int isReadWrite  = (flags & SQLITE_OPEN_READWRITE);
-#if SQLITE_ENABLE_LOCKING_STYLE
-  int isAutoProxy  = (flags & SQLITE_OPEN_AUTOPROXY);
-#endif
-#if defined(__APPLE__) || SQLITE_ENABLE_LOCKING_STYLE
-  struct statfs fsInfo;
-#endif
-
-  /* If creating a master or main-file journal, this function will open
-  ** a file-descriptor on the directory too. The first time unixSync()
-  ** is called the directory file descriptor will be fsync()ed and close()d.
-  */
-  int syncDir = (isCreate && (
-        eType==SQLITE_OPEN_MASTER_JOURNAL 
-     || eType==SQLITE_OPEN_MAIN_JOURNAL 
-     || eType==SQLITE_OPEN_WAL
-  ));
-
-  /* If argument zPath is a NULL pointer, this function is required to open
-  ** a temporary file. Use this buffer to store the file name in.
-  */
-  char zTmpname[MAX_PATHNAME+2];
-  const char *zName = zPath;
-
-  /* Check the following statements are true: 
-  **
-  **   (a) Exactly one of the READWRITE and READONLY flags must be set, and 
-  **   (b) if CREATE is set, then READWRITE must also be set, and
-  **   (c) if EXCLUSIVE is set, then CREATE must also be set.
-  **   (d) if DELETEONCLOSE is set, then CREATE must also be set.
-  */
-  assert((isReadonly==0 || isReadWrite==0) && (isReadWrite || isReadonly));
-  assert(isCreate==0 || isReadWrite);
-  assert(isExclusive==0 || isCreate);
-  assert(isDelete==0 || isCreate);
-
-  /* The main DB, main journal, WAL file and master journal are never 
-  ** automatically deleted. Nor are they ever temporary files.  */
-  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_DB );
-  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_JOURNAL );
-  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MASTER_JOURNAL );
-  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_WAL );
-
-  /* Assert that the upper layer has set one of the "file-type" flags. */
-  assert( eType==SQLITE_OPEN_MAIN_DB      || eType==SQLITE_OPEN_TEMP_DB 
-       || eType==SQLITE_OPEN_MAIN_JOURNAL || eType==SQLITE_OPEN_TEMP_JOURNAL 
-       || eType==SQLITE_OPEN_SUBJOURNAL   || eType==SQLITE_OPEN_MASTER_JOURNAL 
-       || eType==SQLITE_OPEN_TRANSIENT_DB || eType==SQLITE_OPEN_WAL
-  );
-
-  /* Detect a pid change and reset the PRNG.  There is a race condition
-  ** here such that two or more threads all trying to open databases at
-  ** the same instant might all reset the PRNG.  But multiple resets
-  ** are harmless.
-  */
-  if( randomnessPid!=getpid() ){
-    randomnessPid = getpid();
-    sqlite3_randomness(0,0);
-  }
-
-  memset(p, 0, sizeof(unixFile));
-
-  if( eType==SQLITE_OPEN_MAIN_DB ){
-    UnixUnusedFd *pUnused;
-    pUnused = findReusableFd(zName, flags);
-    if( pUnused ){
-      fd = pUnused->fd;
-    }else{
-      pUnused = sqlite3_malloc(sizeof(*pUnused));
-      if( !pUnused ){
-        return SQLITE_NOMEM;
-      }
-    }
-    p->pUnused = pUnused;
-
-    /* Database filenames are double-zero terminated if they are not
-    ** URIs with parameters.  Hence, they can always be passed into
-    ** sqlite3_uri_parameter(). */
-    assert( (flags & SQLITE_OPEN_URI) || zName[strlen(zName)+1]==0 );
-
-  }else if( !zName ){
-    /* If zName is NULL, the upper layer is requesting a temp file. */
-    assert(isDelete && !syncDir);
-    rc = unixGetTempname(MAX_PATHNAME+2, zTmpname);
-    if( rc!=SQLITE_OK ){
-      return rc;
-    }
-    zName = zTmpname;
-
-    /* Generated temporary filenames are always double-zero terminated
-    ** for use by sqlite3_uri_parameter(). */
-    assert( zName[strlen(zName)+1]==0 );
-  }
-
-  /* Determine the value of the flags parameter passed to POSIX function
-  ** open(). These must be calculated even if open() is not called, as
-  ** they may be stored as part of the file handle and used by the 
-  ** 'conch file' locking functions later on.  */
-  if( isReadonly )  openFlags |= O_RDONLY;
-  if( isReadWrite ) openFlags |= O_RDWR;
-  if( isCreate )    openFlags |= O_CREAT;
-  if( isExclusive ) openFlags |= (O_EXCL|O_NOFOLLOW);
-  openFlags |= (O_LARGEFILE|O_BINARY);
-
-  if( fd<0 ){
-    mode_t openMode;              /* Permissions to create file with */
-    uid_t uid;                    /* Userid for the file */
-    gid_t gid;                    /* Groupid for the file */
-    rc = findCreateFileMode(zName, flags, &openMode, &uid, &gid);
-    if( rc!=SQLITE_OK ){
-      assert( !p->pUnused );
-      assert( eType==SQLITE_OPEN_WAL || eType==SQLITE_OPEN_MAIN_JOURNAL );
-      return rc;
-    }
-    fd = robust_open(zName, openFlags, openMode);
-    OSTRACE(("OPENX   %-3d %s 0%o\n", fd, zName, openFlags));
-    if( fd<0 && errno!=EISDIR && isReadWrite && !isExclusive ){
-      /* Failed to open the file for read/write access. Try read-only. */
-      flags &= ~(SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE);
-      openFlags &= ~(O_RDWR|O_CREAT);
-      flags |= SQLITE_OPEN_READONLY;
-      openFlags |= O_RDONLY;
-      isReadonly = 1;
-      fd = robust_open(zName, openFlags, openMode);
-    }
-    if( fd<0 ){
-      rc = unixLogError(SQLITE_CANTOPEN_BKPT, "open", zName);
-      goto open_finished;
-    }
-
-    /* If this process is running as root and if creating a new rollback
-    ** journal or WAL file, set the ownership of the journal or WAL to be
-    ** the same as the original database.
-    */
-    if( flags & (SQLITE_OPEN_WAL|SQLITE_OPEN_MAIN_JOURNAL) ){
-      osFchown(fd, uid, gid);
-    }
-  }
-  assert( fd>=0 );
-  if( pOutFlags ){
-    *pOutFlags = flags;
-  }
-
-  if( p->pUnused ){
-    p->pUnused->fd = fd;
-    p->pUnused->flags = flags;
-  }
-
-  if( isDelete ){
-#if OS_VXWORKS
-    zPath = zName;
-#elif defined(SQLITE_UNLINK_AFTER_CLOSE)
-    zPath = sqlite3_mprintf("%s", zName);
-    if( zPath==0 ){
-      robust_close(p, fd, __LINE__);
-      return SQLITE_NOMEM;
-    }
-#else
-    osUnlink(zName);
-#endif
-  }
-#if SQLITE_ENABLE_LOCKING_STYLE
-  else{
-    p->openFlags = openFlags;
-  }
-#endif
-
-  noLock = eType!=SQLITE_OPEN_MAIN_DB;
-
-  
-#if defined(__APPLE__) || SQLITE_ENABLE_LOCKING_STYLE
-  if( fstatfs(fd, &fsInfo) == -1 ){
-    ((unixFile*)pFile)->lastErrno = errno;
-    robust_close(p, fd, __LINE__);
-    return SQLITE_IOERR_ACCESS;
-  }
-  if (0 == strncmp("msdos", fsInfo.f_fstypename, 5)) {
-    ((unixFile*)pFile)->fsFlags |= SQLITE_FSFLAGS_IS_MSDOS;
-  }
-#endif
-
-  /* Set up appropriate ctrlFlags */
-  if( isDelete )                ctrlFlags |= UNIXFILE_DELETE;
-  if( isReadonly )              ctrlFlags |= UNIXFILE_RDONLY;
-  if( noLock )                  ctrlFlags |= UNIXFILE_NOLOCK;
-  if( syncDir )                 ctrlFlags |= UNIXFILE_DIRSYNC;
-  if( flags & SQLITE_OPEN_URI ) ctrlFlags |= UNIXFILE_URI;
-
-#if SQLITE_ENABLE_LOCKING_STYLE
-#if SQLITE_PREFER_PROXY_LOCKING
-  isAutoProxy = 1;
-#endif
-  if( isAutoProxy && (zPath!=NULL) && (!noLock) && pVfs->xOpen ){
-    char *envforce = getenv("SQLITE_FORCE_PROXY_LOCKING");
-    int useProxy = 0;
-
-    /* SQLITE_FORCE_PROXY_LOCKING==1 means force always use proxy, 0 means 
-    ** never use proxy, NULL means use proxy for non-local files only.  */
-    if( envforce!=NULL ){
-      useProxy = atoi(envforce)>0;
-    }else{
-      if( statfs(zPath, &fsInfo) == -1 ){
-        /* In theory, the close(fd) call is sub-optimal. If the file opened
-        ** with fd is a database file, and there are other connections open
-        ** on that file that are currently holding advisory locks on it,
-        ** then the call to close() will cancel those locks. In practice,
-        ** we're assuming that statfs() doesn't fail very often. At least
-        ** not while other file descriptors opened by the same process on
-        ** the same file are working.  */
-        p->lastErrno = errno;
-        robust_close(p, fd, __LINE__);
-        rc = SQLITE_IOERR_ACCESS;
-        goto open_finished;
-      }
-      useProxy = !(fsInfo.f_flags&MNT_LOCAL);
-    }
-    if( useProxy ){
-      rc = fillInUnixFile(pVfs, fd, pFile, zPath, ctrlFlags);
-      if( rc==SQLITE_OK ){
-        rc = proxyTransformUnixFile((unixFile*)pFile, ":auto:");
-        if( rc!=SQLITE_OK ){
-          /* Use unixClose to clean up the resources added in fillInUnixFile 
-          ** and clear all the structure's references.  Specifically, 
-          ** pFile->pMethods will be NULL so sqlite3OsClose will be a no-op 
-          */
-          unixClose(pFile);
-          return rc;
-        }
-      }
-      goto open_finished;
-    }
-  }
-#endif
-  
-  rc = fillInUnixFile(pVfs, fd, pFile, zPath, ctrlFlags);
-
-open_finished:
-  if( rc!=SQLITE_OK ){
-    sqlite3_free(p->pUnused);
-  }
-  return rc;
-}
-
-
-/*
-** Delete the file at zPath. If the dirSync argument is true, fsync()
-** the directory after deleting the file.
-*/
-static int unixDelete(
-  sqlite3_vfs *NotUsed,     /* VFS containing this as the xDelete method */
-  const char *zPath,        /* Name of file to be deleted */
-  int dirSync               /* If true, fsync() directory after deleting file */
-){
-  int rc = SQLITE_OK;
-  UNUSED_PARAMETER(NotUsed);
-  SimulateIOError(return SQLITE_IOERR_DELETE);
-  if( osUnlink(zPath)==(-1) ){
-    if( errno==ENOENT
-#if OS_VXWORKS
-        || osAccess(zPath,0)!=0
-#endif
-    ){
-      rc = SQLITE_IOERR_DELETE_NOENT;
-    }else{
-      rc = unixLogError(SQLITE_IOERR_DELETE, "unlink", zPath);
-    }
-    return rc;
-  }
-#ifndef SQLITE_DISABLE_DIRSYNC
-  if( (dirSync & 1)!=0 ){
-    int fd;
-    rc = osOpenDirectory(zPath, &fd);
-    if( rc==SQLITE_OK ){
-#if OS_VXWORKS
-      if( fsync(fd)==-1 )
-#else
-      if( fsync(fd) )
-#endif
-      {
-        rc = unixLogError(SQLITE_IOERR_DIR_FSYNC, "fsync", zPath);
-      }
-      robust_close(0, fd, __LINE__);
-    }else if( rc==SQLITE_CANTOPEN ){
-      rc = SQLITE_OK;
-    }
-  }
-#endif
-  return rc;
-}
-
-/*
-** Test the existence of or access permissions of file zPath. The
-** test performed depends on the value of flags:
-**
-**     SQLITE_ACCESS_EXISTS: Return 1 if the file exists
-**     SQLITE_ACCESS_READWRITE: Return 1 if the file is read and writable.
-**     SQLITE_ACCESS_READONLY: Return 1 if the file is readable.
-**
-** Otherwise return 0.
-*/
-static int unixAccess(
-  sqlite3_vfs *NotUsed,   /* The VFS containing this xAccess method */
-  const char *zPath,      /* Path of the file to examine */
-  int flags,              /* What do we want to learn about the zPath file? */
-  int *pResOut            /* Write result boolean here */
-){
-  int amode = 0;
-  UNUSED_PARAMETER(NotUsed);
-  SimulateIOError( return SQLITE_IOERR_ACCESS; );
-  switch( flags ){
-    case SQLITE_ACCESS_EXISTS:
-      amode = F_OK;
-      break;
-    case SQLITE_ACCESS_READWRITE:
-      amode = W_OK|R_OK;
-      break;
-    case SQLITE_ACCESS_READ:
-      amode = R_OK;
-      break;
-
-    default:
-      assert(!"Invalid flags argument");
-  }
-  *pResOut = (osAccess(zPath, amode)==0);
-  if( flags==SQLITE_ACCESS_EXISTS && *pResOut ){
-    struct stat buf;
-    if( 0==osStat(zPath, &buf) && buf.st_size==0 ){
-      *pResOut = 0;
-    }
-  }
-  return SQLITE_OK;
-}
-
-
-/*
-** Turn a relative pathname into a full pathname. The relative path
-** is stored as a nul-terminated string in the buffer pointed to by
-** zPath. 
-**
-** zOut points to a buffer of at least sqlite3_vfs.mxPathname bytes 
-** (in this case, MAX_PATHNAME bytes). The full-path is written to
-** this buffer before returning.
-*/
-static int unixFullPathname(
-  sqlite3_vfs *pVfs,            /* Pointer to vfs object */
-  const char *zPath,            /* Possibly relative input path */
-  int nOut,                     /* Size of output buffer in bytes */
-  char *zOut                    /* Output buffer */
-){
-
-  /* It's odd to simulate an io-error here, but really this is just
-  ** using the io-error infrastructure to test that SQLite handles this
-  ** function failing. This function could fail if, for example, the
-  ** current working directory has been unlinked.
-  */
-  SimulateIOError( return SQLITE_ERROR );
-
-  assert( pVfs->mxPathname==MAX_PATHNAME );
-  UNUSED_PARAMETER(pVfs);
-
-  zOut[nOut-1] = '\0';
-  if( zPath[0]=='/' ){
-    sqlite3_snprintf(nOut, zOut, "%s", zPath);
-  }else{
-    int nCwd;
-    if( osGetcwd(zOut, nOut-1)==0 ){
-      return unixLogError(SQLITE_CANTOPEN_BKPT, "getcwd", zPath);
-    }
-    nCwd = (int)strlen(zOut);
-    sqlite3_snprintf(nOut-nCwd, &zOut[nCwd], "/%s", zPath);
-  }
-  return SQLITE_OK;
-}
-
-
-#ifndef SQLITE_OMIT_LOAD_EXTENSION
-/*
-** Interfaces for opening a shared library, finding entry points
-** within the shared library, and closing the shared library.
-*/
-#include <dlfcn.h>
-static void *unixDlOpen(sqlite3_vfs *NotUsed, const char *zFilename){
-  UNUSED_PARAMETER(NotUsed);
-  return dlopen(zFilename, RTLD_NOW | RTLD_GLOBAL);
-}
-
-/*
-** SQLite calls this function immediately after a call to unixDlSym() or
-** unixDlOpen() fails (returns a null pointer). If a more detailed error
-** message is available, it is written to zBufOut. If no error message
-** is available, zBufOut is left unmodified and SQLite uses a default
-** error message.
-*/
-static void unixDlError(sqlite3_vfs *NotUsed, int nBuf, char *zBufOut){
-  const char *zErr;
-  UNUSED_PARAMETER(NotUsed);
-  unixEnterMutex();
-  zErr = dlerror();
-  if( zErr ){
-    sqlite3_snprintf(nBuf, zBufOut, "%s", zErr);
-  }
-  unixLeaveMutex();
-}
-static void (*unixDlSym(sqlite3_vfs *NotUsed, void *p, const char*zSym))(void){
-  /* 
-  ** GCC with -pedantic-errors says that C90 does not allow a void* to be
-  ** cast into a pointer to a function.  And yet the library dlsym() routine
-  ** returns a void* which is really a pointer to a function.  So how do we
-  ** use dlsym() with -pedantic-errors?
-  **
-  ** Variable x below is defined to be a pointer to a function taking
-  ** parameters void* and const char* and returning a pointer to a function.
-  ** We initialize x by assigning it a pointer to the dlsym() function.
-  ** (That assignment requires a cast.)  Then we call the function that
-  ** x points to.  
-  **
-  ** This work-around is unlikely to work correctly on any system where
-  ** you really cannot cast a function pointer into void*.  But then, on the
-  ** other hand, dlsym() will not work on such a system either, so we have
-  ** not really lost anything.
-  */
-  void (*(*x)(void*,const char*))(void);
-  UNUSED_PARAMETER(NotUsed);
-  x = (void(*(*)(void*,const char*))(void))dlsym;
-  return (*x)(p, zSym);
-}
-static void unixDlClose(sqlite3_vfs *NotUsed, void *pHandle){
-  UNUSED_PARAMETER(NotUsed);
-  dlclose(pHandle);
-}
-#else /* if SQLITE_OMIT_LOAD_EXTENSION is defined: */
-  #define unixDlOpen  0
-  #define unixDlError 0
-  #define unixDlSym   0
-  #define unixDlClose 0
-#endif
-
-/*
-** Write nBuf bytes of random data to the supplied buffer zBuf.
-*/
-static int unixRandomness(sqlite3_vfs *NotUsed, int nBuf, char *zBuf){
-  UNUSED_PARAMETER(NotUsed);
-  assert((size_t)nBuf>=(sizeof(time_t)+sizeof(int)));
-
-  /* We have to initialize zBuf to prevent valgrind from reporting
-  ** errors.  The reports issued by valgrind are incorrect - we would
-  ** prefer that the randomness be increased by making use of the
-  ** uninitialized space in zBuf - but valgrind errors tend to worry
-  ** some users.  Rather than argue, it seems easier just to initialize
-  ** the whole array and silence valgrind, even if that means less randomness
-  ** in the random seed.
-  **
-  ** When testing, initializing zBuf[] to zero is all we do.  That means
-  ** that we always use the same random number sequence.  This makes the
-  ** tests repeatable.
-  */
-  memset(zBuf, 0, nBuf);
-  randomnessPid = getpid();  
-#if !defined(SQLITE_TEST)
-  {
-    int fd, got;
-    fd = robust_open("/dev/urandom", O_RDONLY, 0);
-    if( fd<0 ){
-      time_t t;
-      time(&t);
-      memcpy(zBuf, &t, sizeof(t));
-      memcpy(&zBuf[sizeof(t)], &randomnessPid, sizeof(randomnessPid));
-      assert( sizeof(t)+sizeof(randomnessPid)<=(size_t)nBuf );
-      nBuf = sizeof(t) + sizeof(randomnessPid);
-    }else{
-      do{ got = osRead(fd, zBuf, nBuf); }while( got<0 && errno==EINTR );
-      robust_close(0, fd, __LINE__);
-    }
-  }
-#endif
-  return nBuf;
-}
-
-
-/*
-** Sleep for a little while.  Return the amount of time slept.
-** The argument is the number of microseconds we want to sleep.
-** The return value is the number of microseconds of sleep actually
-** requested from the underlying operating system, a number which
-** might be greater than or equal to the argument, but not less
-** than the argument.
-*/
-static int unixSleep(sqlite3_vfs *NotUsed, int microseconds){
-#if OS_VXWORKS
-  struct timespec sp;
-
-  sp.tv_sec = microseconds / 1000000;
-  sp.tv_nsec = (microseconds % 1000000) * 1000;
-  nanosleep(&sp, NULL);
-  UNUSED_PARAMETER(NotUsed);
-  return microseconds;
-#elif defined(HAVE_USLEEP) && HAVE_USLEEP
-  usleep(microseconds);
-  UNUSED_PARAMETER(NotUsed);
-  return microseconds;
-#else
-  int seconds = (microseconds+999999)/1000000;
-  sleep(seconds);
-  UNUSED_PARAMETER(NotUsed);
-  return seconds*1000000;
-#endif
-}
-
-/*
-** The following variable, if set to a non-zero value, is interpreted as
-** the number of seconds since 1970 and is used to set the result of
-** sqlite3OsCurrentTime() during testing.
-*/
-#ifdef SQLITE_TEST
-int sqlite3_current_time = 0;  /* Fake system time in seconds since 1970. */
-#endif
-
-/*
-** Find the current time (in Universal Coordinated Time).  Write into *piNow
-** the current time and date as a Julian Day number times 86_400_000.  In
-** other words, write into *piNow the number of milliseconds since the Julian
-** epoch of noon in Greenwich on November 24, 4714 B.C according to the
-** proleptic Gregorian calendar.
-**
-** On success, return SQLITE_OK.  Return SQLITE_ERROR if the time and date 
-** cannot be found.
-*/
-static int unixCurrentTimeInt64(sqlite3_vfs *NotUsed, sqlite3_int64 *piNow){
-  static const sqlite3_int64 unixEpoch = 24405875*(sqlite3_int64)8640000;
-  int rc = SQLITE_OK;
-#if defined(NO_GETTOD)
-  time_t t;
-  time(&t);
-  *piNow = ((sqlite3_int64)t)*1000 + unixEpoch;
-#elif OS_VXWORKS
-  struct timespec sNow;
-  clock_gettime(CLOCK_REALTIME, &sNow);
-  *piNow = unixEpoch + 1000*(sqlite3_int64)sNow.tv_sec + sNow.tv_nsec/1000000;
-#else
-  struct timeval sNow;
-  if( gettimeofday(&sNow, 0)==0 ){
-    *piNow = unixEpoch + 1000*(sqlite3_int64)sNow.tv_sec + sNow.tv_usec/1000;
-  }else{
-    rc = SQLITE_ERROR;
-  }
-#endif
-
-#ifdef SQLITE_TEST
-  if( sqlite3_current_time ){
-    *piNow = 1000*(sqlite3_int64)sqlite3_current_time + unixEpoch;
-  }
-#endif
-  UNUSED_PARAMETER(NotUsed);
-  return rc;
-}
-
-/*
-** Find the current time (in Universal Coordinated Time).  Write the
-** current time and date as a Julian Day number into *prNow and
-** return 0.  Return 1 if the time and date cannot be found.
-*/
-static int unixCurrentTime(sqlite3_vfs *NotUsed, double *prNow){
-  sqlite3_int64 i = 0;
-  int rc;
-  UNUSED_PARAMETER(NotUsed);
-  rc = unixCurrentTimeInt64(0, &i);
-  *prNow = i/86400000.0;
-  return rc;
-}
-
-/*
-** We added the xGetLastError() method with the intention of providing
-** better low-level error messages when operating-system problems come up
-** during SQLite operation.  But so far, none of that has been implemented
-** in the core.  So this routine is never called.  For now, it is merely
-** a place-holder.
-*/
-static int unixGetLastError(sqlite3_vfs *NotUsed, int NotUsed2, char *NotUsed3){
-  UNUSED_PARAMETER(NotUsed);
-  UNUSED_PARAMETER(NotUsed2);
-  UNUSED_PARAMETER(NotUsed3);
-  return 0;
-}
-
-
-/*
-************************ End of sqlite3_vfs methods ***************************
-******************************************************************************/
-
-/******************************************************************************
-************************** Begin Proxy Locking ********************************
-**
-** Proxy locking is a "uber-locking-method" in this sense:  It uses the
-** other locking methods on secondary lock files.  Proxy locking is a
-** meta-layer over top of the primitive locking implemented above.  For
-** this reason, the division that implements of proxy locking is deferred
-** until late in the file (here) after all of the other I/O methods have
-** been defined - so that the primitive locking methods are available
-** as services to help with the implementation of proxy locking.
-**
-****
-**
-** The default locking schemes in SQLite use byte-range locks on the
-** database file to coordinate safe, concurrent access by multiple readers
-** and writers [http://sqlite.org/lockingv3.html].  The five file locking
-** states (UNLOCKED, PENDING, SHARED, RESERVED, EXCLUSIVE) are implemented
-** as POSIX read & write locks over fixed set of locations (via fsctl),
-** on AFP and SMB only exclusive byte-range locks are available via fsctl
-** with _IOWR('z', 23, struct ByteRangeLockPB2) to track the same 5 states.
-** To simulate a F_RDLCK on the shared range, on AFP a randomly selected
-** address in the shared range is taken for a SHARED lock, the entire
-** shared range is taken for an EXCLUSIVE lock):
-**
-**      PENDING_BYTE        0x40000000
-**      RESERVED_BYTE       0x40000001
-**      SHARED_RANGE        0x40000002 -> 0x40000200
-**
-** This works well on the local file system, but shows a nearly 100x
-** slowdown in read performance on AFP because the AFP client disables
-** the read cache when byte-range locks are present.  Enabling the read
-** cache exposes a cache coherency problem that is present on all OS X
-** supported network file systems.  NFS and AFP both observe the
-** close-to-open semantics for ensuring cache coherency
-** [http://nfs.sourceforge.net/#faq_a8], which does not effectively
-** address the requirements for concurrent database access by multiple
-** readers and writers
-** [http://www.nabble.com/SQLite-on-NFS-cache-coherency-td15655701.html].
-**
-** To address the performance and cache coherency issues, proxy file locking
-** changes the way database access is controlled by limiting access to a
-** single host at a time and moving file locks off of the database file
-** and onto a proxy file on the local file system.  
-**
-**
-** Using proxy locks
-** -----------------
-**
-** C APIs
-**
-**  sqlite3_file_control(db, dbname, SQLITE_SET_LOCKPROXYFILE,
-**                       <proxy_path> | ":auto:");
-**  sqlite3_file_control(db, dbname, SQLITE_GET_LOCKPROXYFILE, &<proxy_path>);
-**
-**
-** SQL pragmas
-**
-**  PRAGMA [database.]lock_proxy_file=<proxy_path> | :auto:
-**  PRAGMA [database.]lock_proxy_file
-**
-** Specifying ":auto:" means that if there is a conch file with a matching
-** host ID in it, the proxy path in the conch file will be used, otherwise
-** a proxy path based on the user's temp dir
-** (via confstr(_CS_DARWIN_USER_TEMP_DIR,...)) will be used and the
-** actual proxy file name is generated from the name and path of the
-** database file.  For example:
-**
-**       For database path "/Users/me/foo.db" 
-**       The lock path will be "<tmpdir>/sqliteplocks/_Users_me_foo.db:auto:")
-**
-** Once a lock proxy is configured for a database connection, it can not
-** be removed, however it may be switched to a different proxy path via
-** the above APIs (assuming the conch file is not being held by another
-** connection or process). 
-**
-**
-** How proxy locking works
-** -----------------------
-**
-** Proxy file locking relies primarily on two new supporting files: 
-**
-**   *  conch file to limit access to the database file to a single host
-**      at a time
-**
-**   *  proxy file to act as a proxy for the advisory locks normally
-**      taken on the database
-**
-** The conch file - to use a proxy file, sqlite must first "hold the conch"
-** by taking an sqlite-style shared lock on the conch file, reading the
-** contents and comparing the host's unique host ID (see below) and lock
-** proxy path against the values stored in the conch.  The conch file is
-** stored in the same directory as the database file and the file name
-** is patterned after the database file name as ".<databasename>-conch".
-** If the conch file does not exist, or its contents do not match the
-** host ID and/or proxy path, then the lock is escalated to an exclusive
-** lock and the conch file contents is updated with the host ID and proxy
-** path and the lock is downgraded to a shared lock again.  If the conch
-** is held by another process (with a shared lock), the exclusive lock
-** will fail and SQLITE_BUSY is returned.
-**
-** The proxy file - a single-byte file used for all advisory file locks
-** normally taken on the database file.   This allows for safe sharing
-** of the database file for multiple readers and writers on the same
-** host (the conch ensures that they all use the same local lock file).
-**
-** Requesting the lock proxy does not immediately take the conch, it is
-** only taken when the first request to lock database file is made.  
-** This matches the semantics of the traditional locking behavior, where
-** opening a connection to a database file does not take a lock on it.
-** The shared lock and an open file descriptor are maintained until 
-** the connection to the database is closed. 
-**
-** The proxy file and the lock file are never deleted so they only need
-** to be created the first time they are used.
-**
-** Configuration options
-** ---------------------
-**
-**  SQLITE_PREFER_PROXY_LOCKING
-**
-**       Database files accessed on non-local file systems are
-**       automatically configured for proxy locking, lock files are
-**       named automatically using the same logic as
-**       PRAGMA lock_proxy_file=":auto:"
-**    
-**  SQLITE_PROXY_DEBUG
-**
-**       Enables the logging of error messages during host id file
-**       retrieval and creation
-**
-**  LOCKPROXYDIR
-**
-**       Overrides the default directory used for lock proxy files that
-**       are named automatically via the ":auto:" setting
-**
-**  SQLITE_DEFAULT_PROXYDIR_PERMISSIONS
-**
-**       Permissions to use when creating a directory for storing the
-**       lock proxy files, only used when LOCKPROXYDIR is not set.
-**    
-**    
-** As mentioned above, when compiled with SQLITE_PREFER_PROXY_LOCKING,
-** setting the environment variable SQLITE_FORCE_PROXY_LOCKING to 1 will
-** force proxy locking to be used for every database file opened, and 0
-** will force automatic proxy locking to be disabled for all database
-** files (explicitly calling the SQLITE_SET_LOCKPROXYFILE pragma or
-** sqlite_file_control API is not affected by SQLITE_FORCE_PROXY_LOCKING).
-*/
-
-/*
-** Proxy locking is only available on MacOSX 
-*/
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-
-/*
-** The proxyLockingContext has the path and file structures for the remote 
-** and local proxy files in it
-*/
-typedef struct proxyLockingContext proxyLockingContext;
-struct proxyLockingContext {
-  unixFile *conchFile;         /* Open conch file */
-  char *conchFilePath;         /* Name of the conch file */
-  unixFile *lockProxy;         /* Open proxy lock file */
-  char *lockProxyPath;         /* Name of the proxy lock file */
-  char *dbPath;                /* Name of the open file */
-  int conchHeld;               /* 1 if the conch is held, -1 if lockless */
-  void *oldLockingContext;     /* Original lockingcontext to restore on close */
-  sqlite3_io_methods const *pOldMethod;     /* Original I/O methods for close */
-};
-
-/* 
-** The proxy lock file path for the database at dbPath is written into lPath, 
-** which must point to valid, writable memory large enough for a maxLen length
-** file path. 
-*/
-static int proxyGetLockPath(const char *dbPath, char *lPath, size_t maxLen){
-  int len;
-  int dbLen;
-  int i;
-
-#ifdef LOCKPROXYDIR
-  len = strlcpy(lPath, LOCKPROXYDIR, maxLen);
-#else
-# ifdef _CS_DARWIN_USER_TEMP_DIR
-  {
-    if( !confstr(_CS_DARWIN_USER_TEMP_DIR, lPath, maxLen) ){
-      OSTRACE(("GETLOCKPATH  failed %s errno=%d pid=%d\n",
-               lPath, errno, getpid()));
-      return SQLITE_IOERR_LOCK;
-    }
-    len = strlcat(lPath, "sqliteplocks", maxLen);    
-  }
-# else
-  len = strlcpy(lPath, "/tmp/", maxLen);
-# endif
-#endif
-
-  if( lPath[len-1]!='/' ){
-    len = strlcat(lPath, "/", maxLen);
-  }
-  
-  /* transform the db path to a unique cache name */
-  dbLen = (int)strlen(dbPath);
-  for( i=0; i<dbLen && (i+len+7)<(int)maxLen; i++){
-    char c = dbPath[i];
-    lPath[i+len] = (c=='/')?'_':c;
-  }
-  lPath[i+len]='\0';
-  strlcat(lPath, ":auto:", maxLen);
-  OSTRACE(("GETLOCKPATH  proxy lock path=%s pid=%d\n", lPath, getpid()));
-  return SQLITE_OK;
-}
-
-/* 
- ** Creates the lock file and any missing directories in lockPath
- */
-static int proxyCreateLockPath(const char *lockPath){
-  int i, len;
-  char buf[MAXPATHLEN];
-  int start = 0;
-  
-  assert(lockPath!=NULL);
-  /* try to create all the intermediate directories */
-  len = (int)strlen(lockPath);
-  buf[0] = lockPath[0];
-  for( i=1; i<len; i++ ){
-    if( lockPath[i] == '/' && (i - start > 0) ){
-      /* only mkdir if leaf dir != "." or "/" or ".." */
-      if( i-start>2 || (i-start==1 && buf[start] != '.' && buf[start] != '/') 
-         || (i-start==2 && buf[start] != '.' && buf[start+1] != '.') ){
-        buf[i]='\0';
-        if( osMkdir(buf, SQLITE_DEFAULT_PROXYDIR_PERMISSIONS) ){
-          int err=errno;
-          if( err!=EEXIST ) {
-            OSTRACE(("CREATELOCKPATH  FAILED creating %s, "
-                     "'%s' proxy lock path=%s pid=%d\n",
-                     buf, strerror(err), lockPath, getpid()));
-            return err;
-          }
-        }
-      }
-      start=i+1;
-    }
-    buf[i] = lockPath[i];
-  }
-  OSTRACE(("CREATELOCKPATH  proxy lock path=%s pid=%d\n", lockPath, getpid()));
-  return 0;
-}
-
-/*
-** Create a new VFS file descriptor (stored in memory obtained from
-** sqlite3_malloc) and open the file named "path" in the file descriptor.
-**
-** The caller is responsible not only for closing the file descriptor
-** but also for freeing the memory associated with the file descriptor.
-*/
-static int proxyCreateUnixFile(
-    const char *path,        /* path for the new unixFile */
-    unixFile **ppFile,       /* unixFile created and returned by ref */
-    int islockfile           /* if non zero missing dirs will be created */
-) {
-  int fd = -1;
-  unixFile *pNew;
-  int rc = SQLITE_OK;
-  int openFlags = O_RDWR | O_CREAT;
-  sqlite3_vfs dummyVfs;
-  int terrno = 0;
-  UnixUnusedFd *pUnused = NULL;
-
-  /* 1. first try to open/create the file
-  ** 2. if that fails, and this is a lock file (not-conch), try creating
-  ** the parent directories and then try again.
-  ** 3. if that fails, try to open the file read-only
-  ** otherwise return BUSY (if lock file) or CANTOPEN for the conch file
-  */
-  pUnused = findReusableFd(path, openFlags);
-  if( pUnused ){
-    fd = pUnused->fd;
-  }else{
-    pUnused = sqlite3_malloc(sizeof(*pUnused));
-    if( !pUnused ){
-      return SQLITE_NOMEM;
-    }
-  }
-  if( fd<0 ){
-    fd = robust_open(path, openFlags, 0);
-    terrno = errno;
-    if( fd<0 && errno==ENOENT && islockfile ){
-      if( proxyCreateLockPath(path) == SQLITE_OK ){
-        fd = robust_open(path, openFlags, 0);
-      }
-    }
-  }
-  if( fd<0 ){
-    openFlags = O_RDONLY;
-    fd = robust_open(path, openFlags, 0);
-    terrno = errno;
-  }
-  if( fd<0 ){
-    if( islockfile ){
-      return SQLITE_BUSY;
-    }
-    switch (terrno) {
-      case EACCES:
-        return SQLITE_PERM;
-      case EIO: 
-        return SQLITE_IOERR_LOCK; /* even though it is the conch */
-      default:
-        return SQLITE_CANTOPEN_BKPT;
-    }
-  }
-  
-  pNew = (unixFile *)sqlite3_malloc(sizeof(*pNew));
-  if( pNew==NULL ){
-    rc = SQLITE_NOMEM;
-    goto end_create_proxy;
-  }
-  memset(pNew, 0, sizeof(unixFile));
-  pNew->openFlags = openFlags;
-  memset(&dummyVfs, 0, sizeof(dummyVfs));
-  dummyVfs.pAppData = (void*)&autolockIoFinder;
-  dummyVfs.zName = "dummy";
-  pUnused->fd = fd;
-  pUnused->flags = openFlags;
-  pNew->pUnused = pUnused;
-  
-  rc = fillInUnixFile(&dummyVfs, fd, (sqlite3_file*)pNew, path, 0);
-  if( rc==SQLITE_OK ){
-    *ppFile = pNew;
-    return SQLITE_OK;
-  }
-end_create_proxy:    
-  robust_close(pNew, fd, __LINE__);
-  sqlite3_free(pNew);
-  sqlite3_free(pUnused);
-  return rc;
-}
-
-#ifdef SQLITE_TEST
-/* simulate multiple hosts by creating unique hostid file paths */
-int sqlite3_hostid_num = 0;
-#endif
-
-#define PROXY_HOSTIDLEN    16  /* conch file host id length */
-
-/* Not always defined in the headers as it ought to be */
-extern int gethostuuid(uuid_t id, const struct timespec *wait);
-
-/* get the host ID via gethostuuid(), pHostID must point to PROXY_HOSTIDLEN 
-** bytes of writable memory.
-*/
-static int proxyGetHostID(unsigned char *pHostID, int *pError){
-  assert(PROXY_HOSTIDLEN == sizeof(uuid_t));
-  memset(pHostID, 0, PROXY_HOSTIDLEN);
-#if defined(__MAX_OS_X_VERSION_MIN_REQUIRED)\
-               && __MAC_OS_X_VERSION_MIN_REQUIRED<1050
-  {
-    static const struct timespec timeout = {1, 0}; /* 1 sec timeout */
-    if( gethostuuid(pHostID, &timeout) ){
-      int err = errno;
-      if( pError ){
-        *pError = err;
-      }
-      return SQLITE_IOERR;
-    }
-  }
-#else
-  UNUSED_PARAMETER(pError);
-#endif
-#ifdef SQLITE_TEST
-  /* simulate multiple hosts by creating unique hostid file paths */
-  if( sqlite3_hostid_num != 0){
-    pHostID[0] = (char)(pHostID[0] + (char)(sqlite3_hostid_num & 0xFF));
-  }
-#endif
-  
-  return SQLITE_OK;
-}
-
-/* The conch file contains the header, host id and lock file path
- */
-#define PROXY_CONCHVERSION 2   /* 1-byte header, 16-byte host id, path */
-#define PROXY_HEADERLEN    1   /* conch file header length */
-#define PROXY_PATHINDEX    (PROXY_HEADERLEN+PROXY_HOSTIDLEN)
-#define PROXY_MAXCONCHLEN  (PROXY_HEADERLEN+PROXY_HOSTIDLEN+MAXPATHLEN)
-
-/* 
-** Takes an open conch file, copies the contents to a new path and then moves 
-** it back.  The newly created file's file descriptor is assigned to the
-** conch file structure and finally the original conch file descriptor is 
-** closed.  Returns zero if successful.
-*/
-static int proxyBreakConchLock(unixFile *pFile, uuid_t myHostID){
-  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
-  unixFile *conchFile = pCtx->conchFile;
-  char tPath[MAXPATHLEN];
-  char buf[PROXY_MAXCONCHLEN];
-  char *cPath = pCtx->conchFilePath;
-  size_t readLen = 0;
-  size_t pathLen = 0;
-  char errmsg[64] = "";
-  int fd = -1;
-  int rc = -1;
-  UNUSED_PARAMETER(myHostID);
-
-  /* create a new path by replace the trailing '-conch' with '-break' */
-  pathLen = strlcpy(tPath, cPath, MAXPATHLEN);
-  if( pathLen>MAXPATHLEN || pathLen<6 || 
-     (strlcpy(&tPath[pathLen-5], "break", 6) != 5) ){
-    sqlite3_snprintf(sizeof(errmsg),errmsg,"path error (len %d)",(int)pathLen);
-    goto end_breaklock;
-  }
-  /* read the conch content */
-  readLen = osPread(conchFile->h, buf, PROXY_MAXCONCHLEN, 0);
-  if( readLen<PROXY_PATHINDEX ){
-    sqlite3_snprintf(sizeof(errmsg),errmsg,"read error (len %d)",(int)readLen);
-    goto end_breaklock;
-  }
-  /* write it out to the temporary break file */
-  fd = robust_open(tPath, (O_RDWR|O_CREAT|O_EXCL), 0);
-  if( fd<0 ){
-    sqlite3_snprintf(sizeof(errmsg), errmsg, "create failed (%d)", errno);
-    goto end_breaklock;
-  }
-  if( osPwrite(fd, buf, readLen, 0) != (ssize_t)readLen ){
-    sqlite3_snprintf(sizeof(errmsg), errmsg, "write failed (%d)", errno);
-    goto end_breaklock;
-  }
-  if( rename(tPath, cPath) ){
-    sqlite3_snprintf(sizeof(errmsg), errmsg, "rename failed (%d)", errno);
-    goto end_breaklock;
-  }
-  rc = 0;
-  fprintf(stderr, "broke stale lock on %s\n", cPath);
-  robust_close(pFile, conchFile->h, __LINE__);
-  conchFile->h = fd;
-  conchFile->openFlags = O_RDWR | O_CREAT;
-
-end_breaklock:
-  if( rc ){
-    if( fd>=0 ){
-      osUnlink(tPath);
-      robust_close(pFile, fd, __LINE__);
-    }
-    fprintf(stderr, "failed to break stale lock on %s, %s\n", cPath, errmsg);
-  }
-  return rc;
-}
-
-/* Take the requested lock on the conch file and break a stale lock if the 
-** host id matches.
-*/
-static int proxyConchLock(unixFile *pFile, uuid_t myHostID, int lockType){
-  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
-  unixFile *conchFile = pCtx->conchFile;
-  int rc = SQLITE_OK;
-  int nTries = 0;
-  struct timespec conchModTime;
-  
-  memset(&conchModTime, 0, sizeof(conchModTime));
-  do {
-    rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, lockType);
-    nTries ++;
-    if( rc==SQLITE_BUSY ){
-      /* If the lock failed (busy):
-       * 1st try: get the mod time of the conch, wait 0.5s and try again. 
-       * 2nd try: fail if the mod time changed or host id is different, wait 
-       *           10 sec and try again
-       * 3rd try: break the lock unless the mod time has changed.
-       */
-      struct stat buf;
-      if( osFstat(conchFile->h, &buf) ){
-        pFile->lastErrno = errno;
-        return SQLITE_IOERR_LOCK;
-      }
-      
-      if( nTries==1 ){
-        conchModTime = buf.st_mtimespec;
-        usleep(500000); /* wait 0.5 sec and try the lock again*/
-        continue;  
-      }
-
-      assert( nTries>1 );
-      if( conchModTime.tv_sec != buf.st_mtimespec.tv_sec || 
-         conchModTime.tv_nsec != buf.st_mtimespec.tv_nsec ){
-        return SQLITE_BUSY;
-      }
-      
-      if( nTries==2 ){  
-        char tBuf[PROXY_MAXCONCHLEN];
-        int len = osPread(conchFile->h, tBuf, PROXY_MAXCONCHLEN, 0);
-        if( len<0 ){
-          pFile->lastErrno = errno;
-          return SQLITE_IOERR_LOCK;
-        }
-        if( len>PROXY_PATHINDEX && tBuf[0]==(char)PROXY_CONCHVERSION){
-          /* don't break the lock if the host id doesn't match */
-          if( 0!=memcmp(&tBuf[PROXY_HEADERLEN], myHostID, PROXY_HOSTIDLEN) ){
-            return SQLITE_BUSY;
-          }
-        }else{
-          /* don't break the lock on short read or a version mismatch */
-          return SQLITE_BUSY;
-        }
-        usleep(10000000); /* wait 10 sec and try the lock again */
-        continue; 
-      }
-      
-      assert( nTries==3 );
-      if( 0==proxyBreakConchLock(pFile, myHostID) ){
-        rc = SQLITE_OK;
-        if( lockType==EXCLUSIVE_LOCK ){
-          rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, SHARED_LOCK);          
-        }
-        if( !rc ){
-          rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, lockType);
-        }
-      }
-    }
-  } while( rc==SQLITE_BUSY && nTries<3 );
-  
-  return rc;
-}
-
-/* Takes the conch by taking a shared lock and read the contents conch, if 
-** lockPath is non-NULL, the host ID and lock file path must match.  A NULL 
-** lockPath means that the lockPath in the conch file will be used if the 
-** host IDs match, or a new lock path will be generated automatically 
-** and written to the conch file.
-*/
-static int proxyTakeConch(unixFile *pFile){
-  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
-  
-  if( pCtx->conchHeld!=0 ){
-    return SQLITE_OK;
-  }else{
-    unixFile *conchFile = pCtx->conchFile;
-    uuid_t myHostID;
-    int pError = 0;
-    char readBuf[PROXY_MAXCONCHLEN];
-    char lockPath[MAXPATHLEN];
-    char *tempLockPath = NULL;
-    int rc = SQLITE_OK;
-    int createConch = 0;
-    int hostIdMatch = 0;
-    int readLen = 0;
-    int tryOldLockPath = 0;
-    int forceNewLockPath = 0;
-    
-    OSTRACE(("TAKECONCH  %d for %s pid=%d\n", conchFile->h,
-             (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"), getpid()));
-
-    rc = proxyGetHostID(myHostID, &pError);
-    if( (rc&0xff)==SQLITE_IOERR ){
-      pFile->lastErrno = pError;
-      goto end_takeconch;
-    }
-    rc = proxyConchLock(pFile, myHostID, SHARED_LOCK);
-    if( rc!=SQLITE_OK ){
-      goto end_takeconch;
-    }
-    /* read the existing conch file */
-    readLen = seekAndRead((unixFile*)conchFile, 0, readBuf, PROXY_MAXCONCHLEN);
-    if( readLen<0 ){
-      /* I/O error: lastErrno set by seekAndRead */
-      pFile->lastErrno = conchFile->lastErrno;
-      rc = SQLITE_IOERR_READ;
-      goto end_takeconch;
-    }else if( readLen<=(PROXY_HEADERLEN+PROXY_HOSTIDLEN) || 
-             readBuf[0]!=(char)PROXY_CONCHVERSION ){
-      /* a short read or version format mismatch means we need to create a new 
-      ** conch file. 
-      */
-      createConch = 1;
-    }
-    /* if the host id matches and the lock path already exists in the conch
-    ** we'll try to use the path there, if we can't open that path, we'll 
-    ** retry with a new auto-generated path 
-    */
-    do { /* in case we need to try again for an :auto: named lock file */
-
-      if( !createConch && !forceNewLockPath ){
-        hostIdMatch = !memcmp(&readBuf[PROXY_HEADERLEN], myHostID, 
-                                  PROXY_HOSTIDLEN);
-        /* if the conch has data compare the contents */
-        if( !pCtx->lockProxyPath ){
-          /* for auto-named local lock file, just check the host ID and we'll
-           ** use the local lock file path that's already in there
-           */
-          if( hostIdMatch ){
-            size_t pathLen = (readLen - PROXY_PATHINDEX);
-            
-            if( pathLen>=MAXPATHLEN ){
-              pathLen=MAXPATHLEN-1;
-            }
-            memcpy(lockPath, &readBuf[PROXY_PATHINDEX], pathLen);
-            lockPath[pathLen] = 0;
-            tempLockPath = lockPath;
-            tryOldLockPath = 1;
-            /* create a copy of the lock path if the conch is taken */
-            goto end_takeconch;
-          }
-        }else if( hostIdMatch
-               && !strncmp(pCtx->lockProxyPath, &readBuf[PROXY_PATHINDEX],
-                           readLen-PROXY_PATHINDEX)
-        ){
-          /* conch host and lock path match */
-          goto end_takeconch; 
-        }
-      }
-      
-      /* if the conch isn't writable and doesn't match, we can't take it */
-      if( (conchFile->openFlags&O_RDWR) == 0 ){
-        rc = SQLITE_BUSY;
-        goto end_takeconch;
-      }
-      
-      /* either the conch didn't match or we need to create a new one */
-      if( !pCtx->lockProxyPath ){
-        proxyGetLockPath(pCtx->dbPath, lockPath, MAXPATHLEN);
-        tempLockPath = lockPath;
-        /* create a copy of the lock path _only_ if the conch is taken */
-      }
-      
-      /* update conch with host and path (this will fail if other process
-      ** has a shared lock already), if the host id matches, use the big
-      ** stick.
-      */
-      futimes(conchFile->h, NULL);
-      if( hostIdMatch && !createConch ){
-        if( conchFile->pInode && conchFile->pInode->nShared>1 ){
-          /* We are trying for an exclusive lock but another thread in this
-           ** same process is still holding a shared lock. */
-          rc = SQLITE_BUSY;
-        } else {          
-          rc = proxyConchLock(pFile, myHostID, EXCLUSIVE_LOCK);
-        }
-      }else{
-        rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, EXCLUSIVE_LOCK);
-      }
-      if( rc==SQLITE_OK ){
-        char writeBuffer[PROXY_MAXCONCHLEN];
-        int writeSize = 0;
-        
-        writeBuffer[0] = (char)PROXY_CONCHVERSION;
-        memcpy(&writeBuffer[PROXY_HEADERLEN], myHostID, PROXY_HOSTIDLEN);
-        if( pCtx->lockProxyPath!=NULL ){
-          strlcpy(&writeBuffer[PROXY_PATHINDEX], pCtx->lockProxyPath, MAXPATHLEN);
-        }else{
-          strlcpy(&writeBuffer[PROXY_PATHINDEX], tempLockPath, MAXPATHLEN);
-        }
-        writeSize = PROXY_PATHINDEX + strlen(&writeBuffer[PROXY_PATHINDEX]);
-        robust_ftruncate(conchFile->h, writeSize);
-        rc = unixWrite((sqlite3_file *)conchFile, writeBuffer, writeSize, 0);
-        fsync(conchFile->h);
-        /* If we created a new conch file (not just updated the contents of a 
-         ** valid conch file), try to match the permissions of the database 
-         */
-        if( rc==SQLITE_OK && createConch ){
-          struct stat buf;
-          int err = osFstat(pFile->h, &buf);
-          if( err==0 ){
-            mode_t cmode = buf.st_mode&(S_IRUSR|S_IWUSR | S_IRGRP|S_IWGRP |
-                                        S_IROTH|S_IWOTH);
-            /* try to match the database file R/W permissions, ignore failure */
-#ifndef SQLITE_PROXY_DEBUG
-            osFchmod(conchFile->h, cmode);
-#else
-            do{
-              rc = osFchmod(conchFile->h, cmode);
-            }while( rc==(-1) && errno==EINTR );
-            if( rc!=0 ){
-              int code = errno;
-              fprintf(stderr, "fchmod %o FAILED with %d %s\n",
-                      cmode, code, strerror(code));
-            } else {
-              fprintf(stderr, "fchmod %o SUCCEDED\n",cmode);
-            }
-          }else{
-            int code = errno;
-            fprintf(stderr, "STAT FAILED[%d] with %d %s\n", 
-                    err, code, strerror(code));
-#endif
-          }
-        }
-      }
-      conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, SHARED_LOCK);
-      
-    end_takeconch:
-      OSTRACE(("TRANSPROXY: CLOSE  %d\n", pFile->h));
-      if( rc==SQLITE_OK && pFile->openFlags ){
-        int fd;
-        if( pFile->h>=0 ){
-          robust_close(pFile, pFile->h, __LINE__);
-        }
-        pFile->h = -1;
-        fd = robust_open(pCtx->dbPath, pFile->openFlags, 0);
-        OSTRACE(("TRANSPROXY: OPEN  %d\n", fd));
-        if( fd>=0 ){
-          pFile->h = fd;
-        }else{
-          rc=SQLITE_CANTOPEN_BKPT; /* SQLITE_BUSY? proxyTakeConch called
-           during locking */
-        }
-      }
-      if( rc==SQLITE_OK && !pCtx->lockProxy ){
-        char *path = tempLockPath ? tempLockPath : pCtx->lockProxyPath;
-        rc = proxyCreateUnixFile(path, &pCtx->lockProxy, 1);
-        if( rc!=SQLITE_OK && rc!=SQLITE_NOMEM && tryOldLockPath ){
-          /* we couldn't create the proxy lock file with the old lock file path
-           ** so try again via auto-naming 
-           */
-          forceNewLockPath = 1;
-          tryOldLockPath = 0;
-          continue; /* go back to the do {} while start point, try again */
-        }
-      }
-      if( rc==SQLITE_OK ){
-        /* Need to make a copy of path if we extracted the value
-         ** from the conch file or the path was allocated on the stack
-         */
-        if( tempLockPath ){
-          pCtx->lockProxyPath = sqlite3DbStrDup(0, tempLockPath);
-          if( !pCtx->lockProxyPath ){
-            rc = SQLITE_NOMEM;
-          }
-        }
-      }
-      if( rc==SQLITE_OK ){
-        pCtx->conchHeld = 1;
-        
-        if( pCtx->lockProxy->pMethod == &afpIoMethods ){
-          afpLockingContext *afpCtx;
-          afpCtx = (afpLockingContext *)pCtx->lockProxy->lockingContext;
-          afpCtx->dbPath = pCtx->lockProxyPath;
-        }
-      } else {
-        conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
-      }
-      OSTRACE(("TAKECONCH  %d %s\n", conchFile->h,
-               rc==SQLITE_OK?"ok":"failed"));
-      return rc;
-    } while (1); /* in case we need to retry the :auto: lock file - 
-                 ** we should never get here except via the 'continue' call. */
-  }
-}
-
-/*
-** If pFile holds a lock on a conch file, then release that lock.
-*/
-static int proxyReleaseConch(unixFile *pFile){
-  int rc = SQLITE_OK;         /* Subroutine return code */
-  proxyLockingContext *pCtx;  /* The locking context for the proxy lock */
-  unixFile *conchFile;        /* Name of the conch file */
-
-  pCtx = (proxyLockingContext *)pFile->lockingContext;
-  conchFile = pCtx->conchFile;
-  OSTRACE(("RELEASECONCH  %d for %s pid=%d\n", conchFile->h,
-           (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"), 
-           getpid()));
-  if( pCtx->conchHeld>0 ){
-    rc = conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
-  }
-  pCtx->conchHeld = 0;
-  OSTRACE(("RELEASECONCH  %d %s\n", conchFile->h,
-           (rc==SQLITE_OK ? "ok" : "failed")));
-  return rc;
-}
-
-/*
-** Given the name of a database file, compute the name of its conch file.
-** Store the conch filename in memory obtained from sqlite3_malloc().
-** Make *pConchPath point to the new name.  Return SQLITE_OK on success
-** or SQLITE_NOMEM if unable to obtain memory.
-**
-** The caller is responsible for ensuring that the allocated memory
-** space is eventually freed.
-**
-** *pConchPath is set to NULL if a memory allocation error occurs.
-*/
-static int proxyCreateConchPathname(char *dbPath, char **pConchPath){
-  int i;                        /* Loop counter */
-  int len = (int)strlen(dbPath); /* Length of database filename - dbPath */
-  char *conchPath;              /* buffer in which to construct conch name */
-
-  /* Allocate space for the conch filename and initialize the name to
-  ** the name of the original database file. */  
-  *pConchPath = conchPath = (char *)sqlite3_malloc(len + 8);
-  if( conchPath==0 ){
-    return SQLITE_NOMEM;
-  }
-  memcpy(conchPath, dbPath, len+1);
-  
-  /* now insert a "." before the last / character */
-  for( i=(len-1); i>=0; i-- ){
-    if( conchPath[i]=='/' ){
-      i++;
-      break;
-    }
-  }
-  conchPath[i]='.';
-  while ( i<len ){
-    conchPath[i+1]=dbPath[i];
-    i++;
-  }
-
-  /* append the "-conch" suffix to the file */
-  memcpy(&conchPath[i+1], "-conch", 7);
-  assert( (int)strlen(conchPath) == len+7 );
-
-  return SQLITE_OK;
-}
-
-
-/* Takes a fully configured proxy locking-style unix file and switches
-** the local lock file path 
-*/
-static int switchLockProxyPath(unixFile *pFile, const char *path) {
-  proxyLockingContext *pCtx = (proxyLockingContext*)pFile->lockingContext;
-  char *oldPath = pCtx->lockProxyPath;
-  int rc = SQLITE_OK;
-
-  if( pFile->eFileLock!=NO_LOCK ){
-    return SQLITE_BUSY;
-  }  
-
-  /* nothing to do if the path is NULL, :auto: or matches the existing path */
-  if( !path || path[0]=='\0' || !strcmp(path, ":auto:") ||
-    (oldPath && !strncmp(oldPath, path, MAXPATHLEN)) ){
-    return SQLITE_OK;
-  }else{
-    unixFile *lockProxy = pCtx->lockProxy;
-    pCtx->lockProxy=NULL;
-    pCtx->conchHeld = 0;
-    if( lockProxy!=NULL ){
-      rc=lockProxy->pMethod->xClose((sqlite3_file *)lockProxy);
-      if( rc ) return rc;
-      sqlite3_free(lockProxy);
-    }
-    sqlite3_free(oldPath);
-    pCtx->lockProxyPath = sqlite3DbStrDup(0, path);
-  }
-  
-  return rc;
-}
-
-/*
-** pFile is a file that has been opened by a prior xOpen call.  dbPath
-** is a string buffer at least MAXPATHLEN+1 characters in size.
-**
-** This routine find the filename associated with pFile and writes it
-** int dbPath.
-*/
-static int proxyGetDbPathForUnixFile(unixFile *pFile, char *dbPath){
-#if defined(__APPLE__)
-  if( pFile->pMethod == &afpIoMethods ){
-    /* afp style keeps a reference to the db path in the filePath field 
-    ** of the struct */
-    assert( (int)strlen((char*)pFile->lockingContext)<=MAXPATHLEN );
-    strlcpy(dbPath, ((afpLockingContext *)pFile->lockingContext)->dbPath, MAXPATHLEN);
-  } else
-#endif
-  if( pFile->pMethod == &dotlockIoMethods ){
-    /* dot lock style uses the locking context to store the dot lock
-    ** file path */
-    int len = strlen((char *)pFile->lockingContext) - strlen(DOTLOCK_SUFFIX);
-    memcpy(dbPath, (char *)pFile->lockingContext, len + 1);
-  }else{
-    /* all other styles use the locking context to store the db file path */
-    assert( strlen((char*)pFile->lockingContext)<=MAXPATHLEN );
-    strlcpy(dbPath, (char *)pFile->lockingContext, MAXPATHLEN);
-  }
-  return SQLITE_OK;
-}
-
-/*
-** Takes an already filled in unix file and alters it so all file locking 
-** will be performed on the local proxy lock file.  The following fields
-** are preserved in the locking context so that they can be restored and 
-** the unix structure properly cleaned up at close time:
-**  ->lockingContext
-**  ->pMethod
-*/
-static int proxyTransformUnixFile(unixFile *pFile, const char *path) {
-  proxyLockingContext *pCtx;
-  char dbPath[MAXPATHLEN+1];       /* Name of the database file */
-  char *lockPath=NULL;
-  int rc = SQLITE_OK;
-  
-  if( pFile->eFileLock!=NO_LOCK ){
-    return SQLITE_BUSY;
-  }
-  proxyGetDbPathForUnixFile(pFile, dbPath);
-  if( !path || path[0]=='\0' || !strcmp(path, ":auto:") ){
-    lockPath=NULL;
-  }else{
-    lockPath=(char *)path;
-  }
-  
-  OSTRACE(("TRANSPROXY  %d for %s pid=%d\n", pFile->h,
-           (lockPath ? lockPath : ":auto:"), getpid()));
-
-  pCtx = sqlite3_malloc( sizeof(*pCtx) );
-  if( pCtx==0 ){
-    return SQLITE_NOMEM;
-  }
-  memset(pCtx, 0, sizeof(*pCtx));
-
-  rc = proxyCreateConchPathname(dbPath, &pCtx->conchFilePath);
-  if( rc==SQLITE_OK ){
-    rc = proxyCreateUnixFile(pCtx->conchFilePath, &pCtx->conchFile, 0);
-    if( rc==SQLITE_CANTOPEN && ((pFile->openFlags&O_RDWR) == 0) ){
-      /* if (a) the open flags are not O_RDWR, (b) the conch isn't there, and
-      ** (c) the file system is read-only, then enable no-locking access.
-      ** Ugh, since O_RDONLY==0x0000 we test for !O_RDWR since unixOpen asserts
-      ** that openFlags will have only one of O_RDONLY or O_RDWR.
-      */
-      struct statfs fsInfo;
-      struct stat conchInfo;
-      int goLockless = 0;
-
-      if( osStat(pCtx->conchFilePath, &conchInfo) == -1 ) {
-        int err = errno;
-        if( (err==ENOENT) && (statfs(dbPath, &fsInfo) != -1) ){
-          goLockless = (fsInfo.f_flags&MNT_RDONLY) == MNT_RDONLY;
-        }
-      }
-      if( goLockless ){
-        pCtx->conchHeld = -1; /* read only FS/ lockless */
-        rc = SQLITE_OK;
-      }
-    }
-  }  
-  if( rc==SQLITE_OK && lockPath ){
-    pCtx->lockProxyPath = sqlite3DbStrDup(0, lockPath);
-  }
-
-  if( rc==SQLITE_OK ){
-    pCtx->dbPath = sqlite3DbStrDup(0, dbPath);
-    if( pCtx->dbPath==NULL ){
-      rc = SQLITE_NOMEM;
-    }
-  }
-  if( rc==SQLITE_OK ){
-    /* all memory is allocated, proxys are created and assigned, 
-    ** switch the locking context and pMethod then return.
-    */
-    pCtx->oldLockingContext = pFile->lockingContext;
-    pFile->lockingContext = pCtx;
-    pCtx->pOldMethod = pFile->pMethod;
-    pFile->pMethod = &proxyIoMethods;
-  }else{
-    if( pCtx->conchFile ){ 
-      pCtx->conchFile->pMethod->xClose((sqlite3_file *)pCtx->conchFile);
-      sqlite3_free(pCtx->conchFile);
-    }
-    sqlite3DbFree(0, pCtx->lockProxyPath);
-    sqlite3_free(pCtx->conchFilePath); 
-    sqlite3_free(pCtx);
-  }
-  OSTRACE(("TRANSPROXY  %d %s\n", pFile->h,
-           (rc==SQLITE_OK ? "ok" : "failed")));
-  return rc;
-}
-
-
-/*
-** This routine handles sqlite3_file_control() calls that are specific
-** to proxy locking.
-*/
-static int proxyFileControl(sqlite3_file *id, int op, void *pArg){
-  switch( op ){
-    case SQLITE_GET_LOCKPROXYFILE: {
-      unixFile *pFile = (unixFile*)id;
-      if( pFile->pMethod == &proxyIoMethods ){
-        proxyLockingContext *pCtx = (proxyLockingContext*)pFile->lockingContext;
-        proxyTakeConch(pFile);
-        if( pCtx->lockProxyPath ){
-          *(const char **)pArg = pCtx->lockProxyPath;
-        }else{
-          *(const char **)pArg = ":auto: (not held)";
-        }
-      } else {
-        *(const char **)pArg = NULL;
-      }
-      return SQLITE_OK;
-    }
-    case SQLITE_SET_LOCKPROXYFILE: {
-      unixFile *pFile = (unixFile*)id;
-      int rc = SQLITE_OK;
-      int isProxyStyle = (pFile->pMethod == &proxyIoMethods);
-      if( pArg==NULL || (const char *)pArg==0 ){
-        if( isProxyStyle ){
-          /* turn off proxy locking - not supported */
-          rc = SQLITE_ERROR /*SQLITE_PROTOCOL? SQLITE_MISUSE?*/;
-        }else{
-          /* turn off proxy locking - already off - NOOP */
-          rc = SQLITE_OK;
-        }
-      }else{
-        const char *proxyPath = (const char *)pArg;
-        if( isProxyStyle ){
-          proxyLockingContext *pCtx = 
-            (proxyLockingContext*)pFile->lockingContext;
-          if( !strcmp(pArg, ":auto:") 
-           || (pCtx->lockProxyPath &&
-               !strncmp(pCtx->lockProxyPath, proxyPath, MAXPATHLEN))
-          ){
-            rc = SQLITE_OK;
-          }else{
-            rc = switchLockProxyPath(pFile, proxyPath);
-          }
-        }else{
-          /* turn on proxy file locking */
-          rc = proxyTransformUnixFile(pFile, proxyPath);
-        }
-      }
-      return rc;
-    }
-    default: {
-      assert( 0 );  /* The call assures that only valid opcodes are sent */
-    }
-  }
-  /*NOTREACHED*/
-  return SQLITE_ERROR;
-}
-
-/*
-** Within this division (the proxying locking implementation) the procedures
-** above this point are all utilities.  The lock-related methods of the
-** proxy-locking sqlite3_io_method object follow.
-*/
-
-
-/*
-** This routine checks if there is a RESERVED lock held on the specified
-** file by this or any other process. If such a lock is held, set *pResOut
-** to a non-zero value otherwise *pResOut is set to zero.  The return value
-** is set to SQLITE_OK unless an I/O error occurs during lock checking.
-*/
-static int proxyCheckReservedLock(sqlite3_file *id, int *pResOut) {
-  unixFile *pFile = (unixFile*)id;
-  int rc = proxyTakeConch(pFile);
-  if( rc==SQLITE_OK ){
-    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
-    if( pCtx->conchHeld>0 ){
-      unixFile *proxy = pCtx->lockProxy;
-      return proxy->pMethod->xCheckReservedLock((sqlite3_file*)proxy, pResOut);
-    }else{ /* conchHeld < 0 is lockless */
-      pResOut=0;
-    }
-  }
-  return rc;
-}
-
-/*
-** Lock the file with the lock specified by parameter eFileLock - one
-** of the following:
-**
-**     (1) SHARED_LOCK
-**     (2) RESERVED_LOCK
-**     (3) PENDING_LOCK
-**     (4) EXCLUSIVE_LOCK
-**
-** Sometimes when requesting one lock state, additional lock states
-** are inserted in between.  The locking might fail on one of the later
-** transitions leaving the lock state different from what it started but
-** still short of its goal.  The following chart shows the allowed
-** transitions and the inserted intermediate states:
-**
-**    UNLOCKED -> SHARED
-**    SHARED -> RESERVED
-**    SHARED -> (PENDING) -> EXCLUSIVE
-**    RESERVED -> (PENDING) -> EXCLUSIVE
-**    PENDING -> EXCLUSIVE
-**
-** This routine will only increase a lock.  Use the sqlite3OsUnlock()
-** routine to lower a locking level.
-*/
-static int proxyLock(sqlite3_file *id, int eFileLock) {
-  unixFile *pFile = (unixFile*)id;
-  int rc = proxyTakeConch(pFile);
-  if( rc==SQLITE_OK ){
-    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
-    if( pCtx->conchHeld>0 ){
-      unixFile *proxy = pCtx->lockProxy;
-      rc = proxy->pMethod->xLock((sqlite3_file*)proxy, eFileLock);
-      pFile->eFileLock = proxy->eFileLock;
-    }else{
-      /* conchHeld < 0 is lockless */
-    }
-  }
-  return rc;
-}
-
-
-/*
-** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
-** must be either NO_LOCK or SHARED_LOCK.
-**
-** If the locking level of the file descriptor is already at or below
-** the requested locking level, this routine is a no-op.
-*/
-static int proxyUnlock(sqlite3_file *id, int eFileLock) {
-  unixFile *pFile = (unixFile*)id;
-  int rc = proxyTakeConch(pFile);
-  if( rc==SQLITE_OK ){
-    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
-    if( pCtx->conchHeld>0 ){
-      unixFile *proxy = pCtx->lockProxy;
-      rc = proxy->pMethod->xUnlock((sqlite3_file*)proxy, eFileLock);
-      pFile->eFileLock = proxy->eFileLock;
-    }else{
-      /* conchHeld < 0 is lockless */
-    }
-  }
-  return rc;
-}
-
-/*
-** Close a file that uses proxy locks.
-*/
-static int proxyClose(sqlite3_file *id) {
-  if( id ){
-    unixFile *pFile = (unixFile*)id;
-    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
-    unixFile *lockProxy = pCtx->lockProxy;
-    unixFile *conchFile = pCtx->conchFile;
-    int rc = SQLITE_OK;
-    
-    if( lockProxy ){
-      rc = lockProxy->pMethod->xUnlock((sqlite3_file*)lockProxy, NO_LOCK);
-      if( rc ) return rc;
-      rc = lockProxy->pMethod->xClose((sqlite3_file*)lockProxy);
-      if( rc ) return rc;
-      sqlite3_free(lockProxy);
-      pCtx->lockProxy = 0;
-    }
-    if( conchFile ){
-      if( pCtx->conchHeld ){
-        rc = proxyReleaseConch(pFile);
-        if( rc ) return rc;
-      }
-      rc = conchFile->pMethod->xClose((sqlite3_file*)conchFile);
-      if( rc ) return rc;
-      sqlite3_free(conchFile);
-    }
-    sqlite3DbFree(0, pCtx->lockProxyPath);
-    sqlite3_free(pCtx->conchFilePath);
-    sqlite3DbFree(0, pCtx->dbPath);
-    /* restore the original locking context and pMethod then close it */
-    pFile->lockingContext = pCtx->oldLockingContext;
-    pFile->pMethod = pCtx->pOldMethod;
-    sqlite3_free(pCtx);
-    return pFile->pMethod->xClose(id);
-  }
-  return SQLITE_OK;
-}
-
-
-
-#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
-/*
-** The proxy locking style is intended for use with AFP filesystems.
-** And since AFP is only supported on MacOSX, the proxy locking is also
-** restricted to MacOSX.
-** 
-**
-******************* End of the proxy lock implementation **********************
-******************************************************************************/
-
-/*
-** Initialize the operating system interface.
-**
-** This routine registers all VFS implementations for unix-like operating
-** systems.  This routine, and the sqlite3_os_end() routine that follows,
-** should be the only routines in this file that are visible from other
-** files.
-**
-** This routine is called once during SQLite initialization and by a
-** single thread.  The memory allocation and mutex subsystems have not
-** necessarily been initialized when this routine is called, and so they
-** should not be used.
-*/
-int sqlite3_os_init(void){ 
-  /* 
-  ** The following macro defines an initializer for an sqlite3_vfs object.
-  ** The name of the VFS is NAME.  The pAppData is a pointer to a pointer
-  ** to the "finder" function.  (pAppData is a pointer to a pointer because
-  ** silly C90 rules prohibit a void* from being cast to a function pointer
-  ** and so we have to go through the intermediate pointer to avoid problems
-  ** when compiling with -pedantic-errors on GCC.)
-  **
-  ** The FINDER parameter to this macro is the name of the pointer to the
-  ** finder-function.  The finder-function returns a pointer to the
-  ** sqlite_io_methods object that implements the desired locking
-  ** behaviors.  See the division above that contains the IOMETHODS
-  ** macro for addition information on finder-functions.
-  **
-  ** Most finders simply return a pointer to a fixed sqlite3_io_methods
-  ** object.  But the "autolockIoFinder" available on MacOSX does a little
-  ** more than that; it looks at the filesystem type that hosts the 
-  ** database file and tries to choose an locking method appropriate for
-  ** that filesystem time.
-  */
-  #define UNIXVFS(VFSNAME, FINDER) {                        \
-    3,                    /* iVersion */                    \
-    sizeof(unixFile),     /* szOsFile */                    \
-    MAX_PATHNAME,         /* mxPathname */                  \
-    0,                    /* pNext */                       \
-    VFSNAME,              /* zName */                       \
-    (void*)&FINDER,       /* pAppData */                    \
-    unixOpen,             /* xOpen */                       \
-    unixDelete,           /* xDelete */                     \
-    unixAccess,           /* xAccess */                     \
-    unixFullPathname,     /* xFullPathname */               \
-    unixDlOpen,           /* xDlOpen */                     \
-    unixDlError,          /* xDlError */                    \
-    unixDlSym,            /* xDlSym */                      \
-    unixDlClose,          /* xDlClose */                    \
-    unixRandomness,       /* xRandomness */                 \
-    unixSleep,            /* xSleep */                      \
-    unixCurrentTime,      /* xCurrentTime */                \
-    unixGetLastError,     /* xGetLastError */               \
-    unixCurrentTimeInt64, /* xCurrentTimeInt64 */           \
-    unixSetSystemCall,    /* xSetSystemCall */              \
-    unixGetSystemCall,    /* xGetSystemCall */              \
-    unixNextSystemCall,   /* xNextSystemCall */             \
-  }
-
-  /*
-  ** All default VFSes for unix are contained in the following array.
-  **
-  ** Note that the sqlite3_vfs.pNext field of the VFS object is modified
-  ** by the SQLite core when the VFS is registered.  So the following
-  ** array cannot be const.
-  */
-  static sqlite3_vfs aVfs[] = {
-#if SQLITE_ENABLE_LOCKING_STYLE && (OS_VXWORKS || defined(__APPLE__))
-    UNIXVFS("unix",          autolockIoFinder ),
-#else
-    UNIXVFS("unix",          posixIoFinder ),
-#endif
-    UNIXVFS("unix-none",     nolockIoFinder ),
-    UNIXVFS("unix-dotfile",  dotlockIoFinder ),
-    UNIXVFS("unix-excl",     posixIoFinder ),
-#if OS_VXWORKS
-    UNIXVFS("unix-namedsem", semIoFinder ),
-#endif
-#if SQLITE_ENABLE_LOCKING_STYLE
-    UNIXVFS("unix-posix",    posixIoFinder ),
-#if !OS_VXWORKS
-    UNIXVFS("unix-flock",    flockIoFinder ),
-#endif
-#endif
-#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
-    UNIXVFS("unix-afp",      afpIoFinder ),
-    UNIXVFS("unix-nfs",      nfsIoFinder ),
-    UNIXVFS("unix-proxy",    proxyIoFinder ),
-#endif
-  };
-  unsigned int i;          /* Loop counter */
-
-  /* Double-check that the aSyscall[] array has been constructed
-  ** correctly.  See ticket [bb3a86e890c8e96ab] */
-  assert( ArraySize(aSyscall)==25 );
-
-  /* Register all VFSes defined in the aVfs[] array */
-  for(i=0; i<(sizeof(aVfs)/sizeof(sqlite3_vfs)); i++){
-    sqlite3_vfs_register(&aVfs[i], i==0);
-  }
-  return SQLITE_OK; 
-}
-
-/*
-** Shutdown the operating system interface.
-**
-** Some operating systems might need to do some cleanup in this routine,
-** to release dynamically allocated objects.  But not on unix.
-** This routine is a no-op for unix.
-*/
-int sqlite3_os_end(void){ 
-  return SQLITE_OK; 
-}
- 
-#endif /* SQLITE_OS_UNIX */