[sql] Import reference version of SQLite 3.17..

third_party/sqlite/sqlite-src-3170000/src/test_journal.c

+/*
+** 2008 Jan 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 code for a VFS layer that acts as a wrapper around
+** an existing VFS. The code in this file attempts to verify that SQLite
+** correctly populates and syncs a journal file before writing to a
+** corresponding database file.
+**
+** INTERFACE
+**
+**   The public interface to this wrapper VFS is two functions:
+**
+**     jt_register()
+**     jt_unregister()
+**
+**   See header comments associated with those two functions below for 
+**   details.
+**
+** LIMITATIONS
+**
+**   This wrapper will not work if "PRAGMA synchronous = off" is used.
+**
+** OPERATION
+**
+**  Starting a Transaction:
+**
+**   When a write-transaction is started, the contents of the database is
+**   inspected and the following data stored as part of the database file 
+**   handle (type struct jt_file):
+**
+**     a) The page-size of the database file.
+**     b) The number of pages that are in the database file.
+**     c) The set of page numbers corresponding to free-list leaf pages.
+**     d) A check-sum for every page in the database file.
+**
+**   The start of a write-transaction is deemed to have occurred when a 
+**   28-byte journal header is written to byte offset 0 of the journal 
+**   file.
+**
+**  Syncing the Journal File:
+**
+**   Whenever the xSync method is invoked to sync a journal-file, the
+**   contents of the journal file are read. For each page written to
+**   the journal file, a check-sum is calculated and compared to the  
+**   check-sum calculated for the corresponding database page when the
+**   write-transaction was initialized. The success of the comparison
+**   is assert()ed. So if SQLite has written something other than the
+**   original content to the database file, an assert() will fail.
+**
+**   Additionally, the set of page numbers for which records exist in
+**   the journal file is added to (unioned with) the set of page numbers
+**   corresponding to free-list leaf pages collected when the 
+**   write-transaction was initialized. This set comprises the page-numbers 
+**   corresponding to those pages that SQLite may now safely modify.
+**
+**  Writing to the Database File:
+**
+**   When a block of data is written to a database file, the following
+**   invariants are asserted:
+**
+**     a) That the block of data is an aligned block of page-size bytes.
+**
+**     b) That if the page being written did not exist when the 
+**        transaction was started (i.e. the database file is growing), then
+**        the journal-file must have been synced at least once since
+**        the start of the transaction.
+**
+**     c) That if the page being written did exist when the transaction 
+**        was started, then the page must have either been a free-list
+**        leaf page at the start of the transaction, or else must have
+**        been stored in the journal file prior to the most recent sync.
+**
+**  Closing a Transaction:
+**
+**   When a transaction is closed, all data collected at the start of
+**   the transaction, or following an xSync of a journal-file, is 
+**   discarded. The end of a transaction is recognized when any one 
+**   of the following occur:
+**
+**     a) A block of zeroes (or anything else that is not a valid 
+**        journal-header) is written to the start of the journal file.
+**
+**     b) A journal file is truncated to zero bytes in size using xTruncate.
+**
+**     c) The journal file is deleted using xDelete.
+*/
+#if SQLITE_TEST          /* This file is used for testing only */
+
+#include "sqlite3.h"
+#include "sqliteInt.h"
+
+/*
+** Maximum pathname length supported by the jt backend.
+*/
+#define JT_MAX_PATHNAME 512
+
+/*
+** Name used to identify this VFS.
+*/
+#define JT_VFS_NAME "jt"
+
+typedef struct jt_file jt_file;
+struct jt_file {
+  sqlite3_file base;
+  const char *zName;       /* Name of open file */
+  int flags;               /* Flags the file was opened with */
+
+  /* The following are only used by database file file handles */
+  int eLock;               /* Current lock held on the file */
+  u32 nPage;               /* Size of file in pages when transaction started */
+  u32 nPagesize;           /* Page size when transaction started */
+  Bitvec *pWritable;       /* Bitvec of pages that may be written to the file */
+  u32 *aCksum;             /* Checksum for first nPage pages */
+  int nSync;               /* Number of times journal file has been synced */
+
+  /* Only used by journal file-handles */
+  sqlite3_int64 iMaxOff;   /* Maximum offset written to this transaction */
+
+  jt_file *pNext;          /* All files are stored in a linked list */
+  sqlite3_file *pReal;     /* The file handle for the underlying vfs */
+};
+
+/*
+** Method declarations for jt_file.
+*/
+static int jtClose(sqlite3_file*);
+static int jtRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
+static int jtWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64 iOfst);
+static int jtTruncate(sqlite3_file*, sqlite3_int64 size);
+static int jtSync(sqlite3_file*, int flags);
+static int jtFileSize(sqlite3_file*, sqlite3_int64 *pSize);
+static int jtLock(sqlite3_file*, int);
+static int jtUnlock(sqlite3_file*, int);
+static int jtCheckReservedLock(sqlite3_file*, int *);
+static int jtFileControl(sqlite3_file*, int op, void *pArg);
+static int jtSectorSize(sqlite3_file*);
+static int jtDeviceCharacteristics(sqlite3_file*);
+
+/*
+** Method declarations for jt_vfs.
+*/
+static int jtOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
+static int jtDelete(sqlite3_vfs*, const char *zName, int syncDir);
+static int jtAccess(sqlite3_vfs*, const char *zName, int flags, int *);
+static int jtFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
+static void *jtDlOpen(sqlite3_vfs*, const char *zFilename);
+static void jtDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
+static void (*jtDlSym(sqlite3_vfs*,void*, const char *zSymbol))(void);
+static void jtDlClose(sqlite3_vfs*, void*);
+static int jtRandomness(sqlite3_vfs*, int nByte, char *zOut);
+static int jtSleep(sqlite3_vfs*, int microseconds);
+static int jtCurrentTime(sqlite3_vfs*, double*);
+static int jtCurrentTimeInt64(sqlite3_vfs*, sqlite3_int64*);
+static int jtGetLastError(sqlite3_vfs*, int, char*);
+
+static sqlite3_vfs jt_vfs = {
+  2,                             /* iVersion */
+  sizeof(jt_file),               /* szOsFile */
+  JT_MAX_PATHNAME,               /* mxPathname */
+  0,                             /* pNext */
+  JT_VFS_NAME,                   /* zName */
+  0,                             /* pAppData */
+  jtOpen,                        /* xOpen */
+  jtDelete,                      /* xDelete */
+  jtAccess,                      /* xAccess */
+  jtFullPathname,                /* xFullPathname */
+  jtDlOpen,                      /* xDlOpen */
+  jtDlError,                     /* xDlError */
+  jtDlSym,                       /* xDlSym */
+  jtDlClose,                     /* xDlClose */
+  jtRandomness,                  /* xRandomness */
+  jtSleep,                       /* xSleep */
+  jtCurrentTime,                 /* xCurrentTime */
+  jtGetLastError,                /* xGetLastError */
+  jtCurrentTimeInt64             /* xCurrentTimeInt64 */
+};
+
+static sqlite3_io_methods jt_io_methods = {
+  1,                             /* iVersion */
+  jtClose,                       /* xClose */
+  jtRead,                        /* xRead */
+  jtWrite,                       /* xWrite */
+  jtTruncate,                    /* xTruncate */
+  jtSync,                        /* xSync */
+  jtFileSize,                    /* xFileSize */
+  jtLock,                        /* xLock */
+  jtUnlock,                      /* xUnlock */
+  jtCheckReservedLock,           /* xCheckReservedLock */
+  jtFileControl,                 /* xFileControl */
+  jtSectorSize,                  /* xSectorSize */
+  jtDeviceCharacteristics        /* xDeviceCharacteristics */
+};
+
+struct JtGlobal {
+  sqlite3_vfs *pVfs;             /* Parent VFS */
+  jt_file *pList;                /* List of all open files */
+};
+static struct JtGlobal g = {0, 0};
+
+/*
+** Functions to obtain and relinquish a mutex to protect g.pList. The
+** STATIC_PRNG mutex is reused, purely for the sake of convenience.
+*/
+static void enterJtMutex(void){
+  sqlite3_mutex_enter(sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_PRNG));
+}
+static void leaveJtMutex(void){
+  sqlite3_mutex_leave(sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_PRNG));
+}
+
+extern int sqlite3_io_error_pending;
+extern int sqlite3_io_error_hit;
+static void stop_ioerr_simulation(int *piSave, int *piSave2){
+  *piSave = sqlite3_io_error_pending;
+  *piSave2 = sqlite3_io_error_hit;
+  sqlite3_io_error_pending = -1;
+  sqlite3_io_error_hit = 0;
+}
+static void start_ioerr_simulation(int iSave, int iSave2){
+  sqlite3_io_error_pending = iSave;
+  sqlite3_io_error_hit = iSave2;
+}
+
+/*
+** The jt_file pointed to by the argument may or may not be a file-handle
+** open on a main database file. If it is, and a transaction is currently
+** opened on the file, then discard all transaction related data.
+*/
+static void closeTransaction(jt_file *p){
+  sqlite3BitvecDestroy(p->pWritable);
+  sqlite3_free(p->aCksum);
+  p->pWritable = 0;
+  p->aCksum = 0;
+  p->nSync = 0;
+}
+
+/*
+** Close an jt-file.
+*/
+static int jtClose(sqlite3_file *pFile){
+  jt_file **pp;
+  jt_file *p = (jt_file *)pFile;
+
+  closeTransaction(p);
+  enterJtMutex();
+  if( p->zName ){
+    for(pp=&g.pList; *pp!=p; pp=&(*pp)->pNext);
+    *pp = p->pNext;
+  }
+  leaveJtMutex();
+  sqlite3OsClose(p->pReal);
+  return SQLITE_OK;
+}
+
+/*
+** Read data from an jt-file.
+*/
+static int jtRead(
+  sqlite3_file *pFile, 
+  void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsRead(p->pReal, zBuf, iAmt, iOfst);
+}
+
+/*
+** Parameter zJournal is the name of a journal file that is currently 
+** open. This function locates and returns the handle opened on the
+** corresponding database file by the pager that currently has the
+** journal file opened. This file-handle is identified by the 
+** following properties:
+**
+**   a) SQLITE_OPEN_MAIN_DB was specified when the file was opened.
+**
+**   b) The file-name specified when the file was opened matches
+**      all but the final 8 characters of the journal file name.
+**
+**   c) There is currently a reserved lock on the file. This 
+**      condition is waived if the noLock argument is non-zero.
+**/
+static jt_file *locateDatabaseHandle(const char *zJournal, int noLock){
+  jt_file *pMain = 0;
+  enterJtMutex();
+  for(pMain=g.pList; pMain; pMain=pMain->pNext){
+    int nName = (int)(strlen(zJournal) - strlen("-journal"));
+    if( (pMain->flags&SQLITE_OPEN_MAIN_DB)
+     && ((int)strlen(pMain->zName)==nName)
+     && 0==memcmp(pMain->zName, zJournal, nName)
+     && ((pMain->eLock>=SQLITE_LOCK_RESERVED) || noLock)
+    ){
+      break;
+    }
+  }
+  leaveJtMutex();
+  return pMain;
+}
+
+/*
+** Parameter z points to a buffer of 4 bytes in size containing a 
+** unsigned 32-bit integer stored in big-endian format. Decode the 
+** integer and return its value.
+*/
+static u32 decodeUint32(const unsigned char *z){
+  return (z[0]<<24) + (z[1]<<16) + (z[2]<<8) + z[3];
+}
+
+/*
+** Calculate a checksum from the buffer of length n bytes pointed to
+** by parameter z.
+*/
+static u32 genCksum(const unsigned char *z, int n){
+  int i;
+  u32 cksum = 0;
+  for(i=0; i<n; i++){
+    cksum = cksum + z[i] + (cksum<<3);
+  }
+  return cksum;
+}
+
+/*
+** The first argument, zBuf, points to a buffer containing a 28 byte
+** serialized journal header. This function deserializes four of the
+** integer fields contained in the journal header and writes their
+** values to the output variables.
+**
+** SQLITE_OK is returned if the journal-header is successfully 
+** decoded. Otherwise, SQLITE_ERROR.
+*/
+static int decodeJournalHdr(
+  const unsigned char *zBuf,         /* Input: 28 byte journal header */
+  u32 *pnRec,                        /* Out: Number of journalled records */
+  u32 *pnPage,                       /* Out: Original database page count */
+  u32 *pnSector,                     /* Out: Sector size in bytes */
+  u32 *pnPagesize                    /* Out: Page size in bytes */
+){
+  unsigned char aMagic[] = { 0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7 };
+  if( memcmp(aMagic, zBuf, 8) ) return SQLITE_ERROR;
+  if( pnRec ) *pnRec = decodeUint32(&zBuf[8]);
+  if( pnPage ) *pnPage = decodeUint32(&zBuf[16]);
+  if( pnSector ) *pnSector = decodeUint32(&zBuf[20]);
+  if( pnPagesize ) *pnPagesize = decodeUint32(&zBuf[24]);
+  return SQLITE_OK;
+}
+
+/*
+** This function is called when a new transaction is opened, just after
+** the first journal-header is written to the journal file.
+*/
+static int openTransaction(jt_file *pMain, jt_file *pJournal){
+  unsigned char *aData;
+  sqlite3_file *p = pMain->pReal;
+  int rc = SQLITE_OK;
+
+  closeTransaction(pMain);
+  aData = sqlite3_malloc(pMain->nPagesize);
+  pMain->pWritable = sqlite3BitvecCreate(pMain->nPage);
+  pMain->aCksum = sqlite3_malloc(sizeof(u32) * (pMain->nPage + 1));
+  pJournal->iMaxOff = 0;
+
+  if( !pMain->pWritable || !pMain->aCksum || !aData ){
+    rc = SQLITE_IOERR_NOMEM;
+  }else if( pMain->nPage>0 ){
+    u32 iTrunk;
+    int iSave;
+    int iSave2;
+
+    stop_ioerr_simulation(&iSave, &iSave2);
+
+    /* Read the database free-list. Add the page-number for each free-list
+    ** leaf to the jt_file.pWritable bitvec.
+    */
+    rc = sqlite3OsRead(p, aData, pMain->nPagesize, 0);
+    if( rc==SQLITE_OK ){
+      u32 nDbsize = decodeUint32(&aData[28]);
+      if( nDbsize>0 && memcmp(&aData[24], &aData[92], 4)==0 ){
+        u32 iPg;
+        for(iPg=nDbsize+1; iPg<=pMain->nPage; iPg++){
+          sqlite3BitvecSet(pMain->pWritable, iPg);
+        }
+      }
+    }
+    iTrunk = decodeUint32(&aData[32]);
+    while( rc==SQLITE_OK && iTrunk>0 ){
+      u32 nLeaf;
+      u32 iLeaf;
+      sqlite3_int64 iOff = (i64)(iTrunk-1)*pMain->nPagesize;
+      rc = sqlite3OsRead(p, aData, pMain->nPagesize, iOff);
+      nLeaf = decodeUint32(&aData[4]);
+      for(iLeaf=0; rc==SQLITE_OK && iLeaf<nLeaf; iLeaf++){
+        u32 pgno = decodeUint32(&aData[8+4*iLeaf]);
+        sqlite3BitvecSet(pMain->pWritable, pgno);
+      }
+      iTrunk = decodeUint32(aData);
+    }
+
+    /* Calculate and store a checksum for each page in the database file. */
+    if( rc==SQLITE_OK ){
+      int ii;
+      for(ii=0; rc==SQLITE_OK && ii<(int)pMain->nPage; ii++){
+        i64 iOff = (i64)(pMain->nPagesize) * (i64)ii;
+        if( iOff==PENDING_BYTE ) continue;
+        rc = sqlite3OsRead(pMain->pReal, aData, pMain->nPagesize, iOff);
+        pMain->aCksum[ii] = genCksum(aData, pMain->nPagesize);
+        if( ii+1==(int)pMain->nPage && rc==SQLITE_IOERR_SHORT_READ ){
+          rc = SQLITE_OK;
+        }
+      }
+    }
+
+    start_ioerr_simulation(iSave, iSave2);
+  }
+
+  sqlite3_free(aData);
+  return rc;
+}
+
+/*
+** The first argument to this function is a handle open on a journal file.
+** This function reads the journal file and adds the page number for each
+** page in the journal to the Bitvec object passed as the second argument.
+*/
+static int readJournalFile(jt_file *p, jt_file *pMain){
+  int rc = SQLITE_OK;
+  unsigned char zBuf[28];
+  sqlite3_file *pReal = p->pReal;
+  sqlite3_int64 iOff = 0;
+  sqlite3_int64 iSize = p->iMaxOff;
+  unsigned char *aPage;
+  int iSave;
+  int iSave2;
+
+  aPage = sqlite3_malloc(pMain->nPagesize);
+  if( !aPage ){
+    return SQLITE_IOERR_NOMEM;
+  }
+
+  stop_ioerr_simulation(&iSave, &iSave2);
+
+  while( rc==SQLITE_OK && iOff<iSize ){
+    u32 nRec, nPage, nSector, nPagesize;
+    u32 ii;
+
+    /* Read and decode the next journal-header from the journal file. */
+    rc = sqlite3OsRead(pReal, zBuf, 28, iOff);
+    if( rc!=SQLITE_OK 
+     || decodeJournalHdr(zBuf, &nRec, &nPage, &nSector, &nPagesize) 
+    ){
+      goto finish_rjf;
+    }
+    iOff += nSector;
+
+    if( nRec==0 ){
+      /* A trick. There might be another journal-header immediately 
+      ** following this one. In this case, 0 records means 0 records, 
+      ** not "read until the end of the file". See also ticket #2565.
+      */
+      if( iSize>=(iOff+nSector) ){
+        rc = sqlite3OsRead(pReal, zBuf, 28, iOff);
+        if( rc!=SQLITE_OK || 0==decodeJournalHdr(zBuf, 0, 0, 0, 0) ){
+          continue;
+        }
+      }
+      nRec = (u32)((iSize-iOff) / (pMain->nPagesize+8));
+    }
+
+    /* Read all the records that follow the journal-header just read. */
+    for(ii=0; rc==SQLITE_OK && ii<nRec && iOff<iSize; ii++){
+      u32 pgno;
+      rc = sqlite3OsRead(pReal, zBuf, 4, iOff);
+      if( rc==SQLITE_OK ){
+        pgno = decodeUint32(zBuf);
+        if( pgno>0 && pgno<=pMain->nPage ){
+          if( 0==sqlite3BitvecTest(pMain->pWritable, pgno) ){
+            rc = sqlite3OsRead(pReal, aPage, pMain->nPagesize, iOff+4);
+            if( rc==SQLITE_OK ){
+              u32 cksum = genCksum(aPage, pMain->nPagesize);
+              assert( cksum==pMain->aCksum[pgno-1] );
+            }
+          }
+          sqlite3BitvecSet(pMain->pWritable, pgno);
+        }
+        iOff += (8 + pMain->nPagesize);
+      }
+    }
+
+    iOff = ((iOff + (nSector-1)) / nSector) * nSector;
+  }
+
+finish_rjf:
+  start_ioerr_simulation(iSave, iSave2);
+  sqlite3_free(aPage);
+  if( rc==SQLITE_IOERR_SHORT_READ ){
+    rc = SQLITE_OK;
+  }
+  return rc;
+}
+
+/*
+** Write data to an jt-file.
+*/
+static int jtWrite(
+  sqlite3_file *pFile, 
+  const void *zBuf, 
+  int iAmt, 
+  sqlite_int64 iOfst
+){
+  int rc;
+  jt_file *p = (jt_file *)pFile;
+  if( p->flags&SQLITE_OPEN_MAIN_JOURNAL ){
+    if( iOfst==0 ){
+      jt_file *pMain = locateDatabaseHandle(p->zName, 0);
+      assert( pMain );
+  
+      if( iAmt==28 ){
+        /* Zeroing the first journal-file header. This is the end of a
+        ** transaction. */
+        closeTransaction(pMain);
+      }else if( iAmt!=12 ){
+        /* Writing the first journal header to a journal file. This happens
+        ** when a transaction is first started.  */
+        u8 *z = (u8 *)zBuf;
+        pMain->nPage = decodeUint32(&z[16]);
+        pMain->nPagesize = decodeUint32(&z[24]);
+        if( SQLITE_OK!=(rc=openTransaction(pMain, p)) ){
+          return rc;
+        }
+      }
+    }
+    if( p->iMaxOff<(iOfst + iAmt) ){
+      p->iMaxOff = iOfst + iAmt;
+    }
+  }
+
+  if( p->flags&SQLITE_OPEN_MAIN_DB && p->pWritable ){
+    if( iAmt<(int)p->nPagesize 
+     && p->nPagesize%iAmt==0 
+     && iOfst>=(PENDING_BYTE+512) 
+     && iOfst+iAmt<=PENDING_BYTE+p->nPagesize
+    ){
+      /* No-op. This special case is hit when the backup code is copying a
+      ** to a database with a larger page-size than the source database and
+      ** it needs to fill in the non-locking-region part of the original
+      ** pending-byte page.
+      */
+    }else{
+      u32 pgno = (u32)(iOfst/p->nPagesize + 1);
+      assert( (iAmt==1||iAmt==(int)p->nPagesize) &&
+              ((iOfst+iAmt)%p->nPagesize)==0 );
+      assert( pgno<=p->nPage || p->nSync>0 );
+      assert( pgno>p->nPage || sqlite3BitvecTest(p->pWritable, pgno) );
+    }
+  }
+
+  rc = sqlite3OsWrite(p->pReal, zBuf, iAmt, iOfst);
+  if( (p->flags&SQLITE_OPEN_MAIN_JOURNAL) && iAmt==12 ){
+    jt_file *pMain = locateDatabaseHandle(p->zName, 0);
+    int rc2 = readJournalFile(p, pMain);
+    if( rc==SQLITE_OK ) rc = rc2;
+  }
+  return rc;
+}
+
+/*
+** Truncate an jt-file.
+*/
+static int jtTruncate(sqlite3_file *pFile, sqlite_int64 size){
+  jt_file *p = (jt_file *)pFile;
+  if( p->flags&SQLITE_OPEN_MAIN_JOURNAL && size==0 ){
+    /* Truncating a journal file. This is the end of a transaction. */
+    jt_file *pMain = locateDatabaseHandle(p->zName, 0);
+    closeTransaction(pMain);
+  }
+  if( p->flags&SQLITE_OPEN_MAIN_DB && p->pWritable ){
+    u32 pgno;
+    u32 locking_page = (u32)(PENDING_BYTE/p->nPagesize+1);
+    for(pgno=(u32)(size/p->nPagesize+1); pgno<=p->nPage; pgno++){
+      assert( pgno==locking_page || sqlite3BitvecTest(p->pWritable, pgno) );
+    }
+  }
+  return sqlite3OsTruncate(p->pReal, size);
+}
+
+/*
+** Sync an jt-file.
+*/
+static int jtSync(sqlite3_file *pFile, int flags){
+  jt_file *p = (jt_file *)pFile;
+
+  if( p->flags&SQLITE_OPEN_MAIN_JOURNAL ){
+    int rc;
+    jt_file *pMain;                   /* The associated database file */
+
+    /* The journal file is being synced. At this point, we inspect the 
+    ** contents of the file up to this point and set each bit in the 
+    ** jt_file.pWritable bitvec of the main database file associated with
+    ** this journal file.
+    */
+    pMain = locateDatabaseHandle(p->zName, 0);
+
+    /* Set the bitvec values */
+    if( pMain && pMain->pWritable ){
+      pMain->nSync++;
+      rc = readJournalFile(p, pMain);
+      if( rc!=SQLITE_OK ){
+        return rc;
+      }
+    }
+  }
+
+  return sqlite3OsSync(p->pReal, flags);
+}
+
+/*
+** Return the current file-size of an jt-file.
+*/
+static int jtFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsFileSize(p->pReal, pSize);
+}
+
+/*
+** Lock an jt-file.
+*/
+static int jtLock(sqlite3_file *pFile, int eLock){
+  int rc;
+  jt_file *p = (jt_file *)pFile;
+  rc = sqlite3OsLock(p->pReal, eLock);
+  if( rc==SQLITE_OK && eLock>p->eLock ){
+    p->eLock = eLock;
+  }
+  return rc;
+}
+
+/*
+** Unlock an jt-file.
+*/
+static int jtUnlock(sqlite3_file *pFile, int eLock){
+  int rc;
+  jt_file *p = (jt_file *)pFile;
+  rc = sqlite3OsUnlock(p->pReal, eLock);
+  if( rc==SQLITE_OK && eLock<p->eLock ){
+    p->eLock = eLock;
+  }
+  return rc;
+}
+
+/*
+** Check if another file-handle holds a RESERVED lock on an jt-file.
+*/
+static int jtCheckReservedLock(sqlite3_file *pFile, int *pResOut){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsCheckReservedLock(p->pReal, pResOut);
+}
+
+/*
+** File control method. For custom operations on an jt-file.
+*/
+static int jtFileControl(sqlite3_file *pFile, int op, void *pArg){
+  jt_file *p = (jt_file *)pFile;
+  return p->pReal->pMethods->xFileControl(p->pReal, op, pArg);
+}
+
+/*
+** Return the sector-size in bytes for an jt-file.
+*/
+static int jtSectorSize(sqlite3_file *pFile){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsSectorSize(p->pReal);
+}
+
+/*
+** Return the device characteristic flags supported by an jt-file.
+*/
+static int jtDeviceCharacteristics(sqlite3_file *pFile){
+  jt_file *p = (jt_file *)pFile;
+  return sqlite3OsDeviceCharacteristics(p->pReal);
+}
+
+/*
+** Open an jt file handle.
+*/
+static int jtOpen(
+  sqlite3_vfs *pVfs,
+  const char *zName,
+  sqlite3_file *pFile,
+  int flags,
+  int *pOutFlags
+){
+  int rc;
+  jt_file *p = (jt_file *)pFile;
+  pFile->pMethods = 0;
+  p->pReal = (sqlite3_file *)&p[1];
+  p->pReal->pMethods = 0;
+  rc = sqlite3OsOpen(g.pVfs, zName, p->pReal, flags, pOutFlags);
+  assert( rc==SQLITE_OK || p->pReal->pMethods==0 );
+  if( rc==SQLITE_OK ){
+    pFile->pMethods = &jt_io_methods;
+    p->eLock = 0;
+    p->zName = zName;
+    p->flags = flags;
+    p->pNext = 0;
+    p->pWritable = 0;
+    p->aCksum = 0;
+    enterJtMutex();
+    if( zName ){
+      p->pNext = g.pList;
+      g.pList = p;
+    }
+    leaveJtMutex();
+  }
+  return rc;
+}
+
+/*
+** Delete the file located at zPath. If the dirSync argument is true,
+** ensure the file-system modifications are synced to disk before
+** returning.
+*/
+static int jtDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
+  int nPath = (int)strlen(zPath);
+  if( nPath>8 && 0==strcmp("-journal", &zPath[nPath-8]) ){
+    /* Deleting a journal file. The end of a transaction. */
+    jt_file *pMain = locateDatabaseHandle(zPath, 0);
+    if( pMain ){
+      closeTransaction(pMain);
+    }
+  }
+
+  return sqlite3OsDelete(g.pVfs, zPath, dirSync);
+}
+
+/*
+** Test for access permissions. Return true if the requested permission
+** is available, or false otherwise.
+*/
+static int jtAccess(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int flags, 
+  int *pResOut
+){
+  return sqlite3OsAccess(g.pVfs, zPath, flags, pResOut);
+}
+
+/*
+** Populate buffer zOut with the full canonical pathname corresponding
+** to the pathname in zPath. zOut is guaranteed to point to a buffer
+** of at least (JT_MAX_PATHNAME+1) bytes.
+*/
+static int jtFullPathname(
+  sqlite3_vfs *pVfs, 
+  const char *zPath, 
+  int nOut, 
+  char *zOut
+){
+  return sqlite3OsFullPathname(g.pVfs, zPath, nOut, zOut);
+}
+
+/*
+** Open the dynamic library located at zPath and return a handle.
+*/
+static void *jtDlOpen(sqlite3_vfs *pVfs, const char *zPath){
+  return g.pVfs->xDlOpen(g.pVfs, zPath);
+}
+
+/*
+** Populate the buffer zErrMsg (size nByte bytes) with a human readable
+** utf-8 string describing the most recent error encountered associated 
+** with dynamic libraries.
+*/
+static void jtDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
+  g.pVfs->xDlError(g.pVfs, nByte, zErrMsg);
+}
+
+/*
+** Return a pointer to the symbol zSymbol in the dynamic library pHandle.
+*/
+static void (*jtDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){
+  return g.pVfs->xDlSym(g.pVfs, p, zSym);
+}
+
+/*
+** Close the dynamic library handle pHandle.
+*/
+static void jtDlClose(sqlite3_vfs *pVfs, void *pHandle){
+  g.pVfs->xDlClose(g.pVfs, pHandle);
+}
+
+/*
+** Populate the buffer pointed to by zBufOut with nByte bytes of 
+** random data.
+*/
+static int jtRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
+  return sqlite3OsRandomness(g.pVfs, nByte, zBufOut);
+}
+
+/*
+** Sleep for nMicro microseconds. Return the number of microseconds 
+** actually slept.
+*/
+static int jtSleep(sqlite3_vfs *pVfs, int nMicro){
+  return sqlite3OsSleep(g.pVfs, nMicro);
+}
+
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int jtCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
+  return g.pVfs->xCurrentTime(g.pVfs, pTimeOut);
+}
+/*
+** Return the current time as a Julian Day number in *pTimeOut.
+*/
+static int jtCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *pTimeOut){
+  return g.pVfs->xCurrentTimeInt64(g.pVfs, pTimeOut);
+}
+
+static int jtGetLastError(sqlite3_vfs *pVfs, int n, char *z){
+  return g.pVfs->xGetLastError(g.pVfs, n, z);
+}
+
+/**************************************************************************
+** Start of public API.
+*/
+
+/*
+** Configure the jt VFS as a wrapper around the VFS named by parameter 
+** zWrap. If the isDefault parameter is true, then the jt VFS is installed
+** as the new default VFS for SQLite connections. If isDefault is not
+** true, then the jt VFS is installed as non-default. In this case it
+** is available via its name, "jt".
+*/
+int jt_register(char *zWrap, int isDefault){
+  g.pVfs = sqlite3_vfs_find(zWrap);
+  if( g.pVfs==0 ){
+    return SQLITE_ERROR;
+  }
+  jt_vfs.szOsFile = sizeof(jt_file) + g.pVfs->szOsFile;
+  if( g.pVfs->iVersion==1 ){
+    jt_vfs.iVersion = 1;
+  }else if( g.pVfs->xCurrentTimeInt64==0 ){
+    jt_vfs.xCurrentTimeInt64 = 0;
+  }
+  sqlite3_vfs_register(&jt_vfs, isDefault);
+  return SQLITE_OK;
+}
+
+/*
+** Uninstall the jt VFS, if it is installed.
+*/
+void jt_unregister(void){
+  sqlite3_vfs_unregister(&jt_vfs);
+}
+
+#endif