[sql] Import reference version of SQLite 3.17..

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

+/*
+** 2008 October 07
+**
+** 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 C functions that implement mutexes.
+**
+** This implementation in this file does not provide any mutual
+** exclusion and is thus suitable for use only in applications
+** that use SQLite in a single thread.  The routines defined
+** here are place-holders.  Applications can substitute working
+** mutex routines at start-time using the
+**
+**     sqlite3_config(SQLITE_CONFIG_MUTEX,...)
+**
+** interface.
+**
+** If compiled with SQLITE_DEBUG, then additional logic is inserted
+** that does error checking on mutexes to make sure they are being
+** called correctly.
+*/
+#include "sqliteInt.h"
+
+#ifndef SQLITE_MUTEX_OMIT
+
+#ifndef SQLITE_DEBUG
+/*
+** Stub routines for all mutex methods.
+**
+** This routines provide no mutual exclusion or error checking.
+*/
+static int noopMutexInit(void){ return SQLITE_OK; }
+static int noopMutexEnd(void){ return SQLITE_OK; }
+static sqlite3_mutex *noopMutexAlloc(int id){ 
+  UNUSED_PARAMETER(id);
+  return (sqlite3_mutex*)8; 
+}
+static void noopMutexFree(sqlite3_mutex *p){ UNUSED_PARAMETER(p); return; }
+static void noopMutexEnter(sqlite3_mutex *p){ UNUSED_PARAMETER(p); return; }
+static int noopMutexTry(sqlite3_mutex *p){
+  UNUSED_PARAMETER(p);
+  return SQLITE_OK;
+}
+static void noopMutexLeave(sqlite3_mutex *p){ UNUSED_PARAMETER(p); return; }
+
+sqlite3_mutex_methods const *sqlite3NoopMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
+    noopMutexInit,
+    noopMutexEnd,
+    noopMutexAlloc,
+    noopMutexFree,
+    noopMutexEnter,
+    noopMutexTry,
+    noopMutexLeave,
+
+    0,
+    0,
+  };
+
+  return &sMutex;
+}
+#endif /* !SQLITE_DEBUG */
+
+#ifdef SQLITE_DEBUG
+/*
+** In this implementation, error checking is provided for testing
+** and debugging purposes.  The mutexes still do not provide any
+** mutual exclusion.
+*/
+
+/*
+** The mutex object
+*/
+typedef struct sqlite3_debug_mutex {
+  int id;     /* The mutex type */
+  int cnt;    /* Number of entries without a matching leave */
+} sqlite3_debug_mutex;
+
+/*
+** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
+** intended for use inside assert() statements.
+*/
+static int debugMutexHeld(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  return p==0 || p->cnt>0;
+}
+static int debugMutexNotheld(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  return p==0 || p->cnt==0;
+}
+
+/*
+** Initialize and deinitialize the mutex subsystem.
+*/
+static int debugMutexInit(void){ return SQLITE_OK; }
+static int debugMutexEnd(void){ return SQLITE_OK; }
+
+/*
+** The sqlite3_mutex_alloc() routine allocates a new
+** mutex and returns a pointer to it.  If it returns NULL
+** that means that a mutex could not be allocated. 
+*/
+static sqlite3_mutex *debugMutexAlloc(int id){
+  static sqlite3_debug_mutex aStatic[SQLITE_MUTEX_STATIC_VFS3 - 1];
+  sqlite3_debug_mutex *pNew = 0;
+  switch( id ){
+    case SQLITE_MUTEX_FAST:
+    case SQLITE_MUTEX_RECURSIVE: {
+      pNew = sqlite3Malloc(sizeof(*pNew));
+      if( pNew ){
+        pNew->id = id;
+        pNew->cnt = 0;
+      }
+      break;
+    }
+    default: {
+#ifdef SQLITE_ENABLE_API_ARMOR
+      if( id-2<0 || id-2>=ArraySize(aStatic) ){
+        (void)SQLITE_MISUSE_BKPT;
+        return 0;
+      }
+#endif
+      pNew = &aStatic[id-2];
+      pNew->id = id;
+      break;
+    }
+  }
+  return (sqlite3_mutex*)pNew;
+}
+
+/*
+** This routine deallocates a previously allocated mutex.
+*/
+static void debugMutexFree(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( p->cnt==0 );
+  if( p->id==SQLITE_MUTEX_RECURSIVE || p->id==SQLITE_MUTEX_FAST ){
+    sqlite3_free(p);
+  }else{
+#ifdef SQLITE_ENABLE_API_ARMOR
+    (void)SQLITE_MISUSE_BKPT;
+#endif
+  }
+}
+
+/*
+** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
+** to enter a mutex.  If another thread is already within the mutex,
+** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
+** SQLITE_BUSY.  The sqlite3_mutex_try() interface returns SQLITE_OK
+** upon successful entry.  Mutexes created using SQLITE_MUTEX_RECURSIVE can
+** be entered multiple times by the same thread.  In such cases the,
+** mutex must be exited an equal number of times before another thread
+** can enter.  If the same thread tries to enter any other kind of mutex
+** more than once, the behavior is undefined.
+*/
+static void debugMutexEnter(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
+  p->cnt++;
+}
+static int debugMutexTry(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
+  p->cnt++;
+  return SQLITE_OK;
+}
+
+/*
+** The sqlite3_mutex_leave() routine exits a mutex that was
+** previously entered by the same thread.  The behavior
+** is undefined if the mutex is not currently entered or
+** is not currently allocated.  SQLite will never do either.
+*/
+static void debugMutexLeave(sqlite3_mutex *pX){
+  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
+  assert( debugMutexHeld(pX) );
+  p->cnt--;
+  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
+}
+
+sqlite3_mutex_methods const *sqlite3NoopMutex(void){
+  static const sqlite3_mutex_methods sMutex = {
+    debugMutexInit,
+    debugMutexEnd,
+    debugMutexAlloc,
+    debugMutexFree,
+    debugMutexEnter,
+    debugMutexTry,
+    debugMutexLeave,
+
+    debugMutexHeld,
+    debugMutexNotheld
+  };
+
+  return &sMutex;
+}
+#endif /* SQLITE_DEBUG */
+
+/*
+** If compiled with SQLITE_MUTEX_NOOP, then the no-op mutex implementation
+** is used regardless of the run-time threadsafety setting.
+*/
+#ifdef SQLITE_MUTEX_NOOP
+sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
+  return sqlite3NoopMutex();
+}
+#endif /* defined(SQLITE_MUTEX_NOOP) */
+#endif /* !defined(SQLITE_MUTEX_OMIT) */