[sql] Import reference version of SQLite 3.17..

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

+/*
+** 2007 August 14
+**
+** 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 file contains code that is common across all mutex implementations.
+*/
+#include "sqliteInt.h"
+
+#if defined(SQLITE_DEBUG) && !defined(SQLITE_MUTEX_OMIT)
+/*
+** For debugging purposes, record when the mutex subsystem is initialized
+** and uninitialized so that we can assert() if there is an attempt to
+** allocate a mutex while the system is uninitialized.
+*/
+static SQLITE_WSD int mutexIsInit = 0;
+#endif /* SQLITE_DEBUG && !defined(SQLITE_MUTEX_OMIT) */
+
+
+#ifndef SQLITE_MUTEX_OMIT
+/*
+** Initialize the mutex system.
+*/
+int sqlite3MutexInit(void){ 
+  int rc = SQLITE_OK;
+  if( !sqlite3GlobalConfig.mutex.xMutexAlloc ){
+    /* If the xMutexAlloc method has not been set, then the user did not
+    ** install a mutex implementation via sqlite3_config() prior to 
+    ** sqlite3_initialize() being called. This block copies pointers to
+    ** the default implementation into the sqlite3GlobalConfig structure.
+    */
+    sqlite3_mutex_methods const *pFrom;
+    sqlite3_mutex_methods *pTo = &sqlite3GlobalConfig.mutex;
+
+    if( sqlite3GlobalConfig.bCoreMutex ){
+      pFrom = sqlite3DefaultMutex();
+    }else{
+      pFrom = sqlite3NoopMutex();
+    }
+    pTo->xMutexInit = pFrom->xMutexInit;
+    pTo->xMutexEnd = pFrom->xMutexEnd;
+    pTo->xMutexFree = pFrom->xMutexFree;
+    pTo->xMutexEnter = pFrom->xMutexEnter;
+    pTo->xMutexTry = pFrom->xMutexTry;
+    pTo->xMutexLeave = pFrom->xMutexLeave;
+    pTo->xMutexHeld = pFrom->xMutexHeld;
+    pTo->xMutexNotheld = pFrom->xMutexNotheld;
+    sqlite3MemoryBarrier();
+    pTo->xMutexAlloc = pFrom->xMutexAlloc;
+  }
+  assert( sqlite3GlobalConfig.mutex.xMutexInit );
+  rc = sqlite3GlobalConfig.mutex.xMutexInit();
+
+#ifdef SQLITE_DEBUG
+  GLOBAL(int, mutexIsInit) = 1;
+#endif
+
+  return rc;
+}
+
+/*
+** Shutdown the mutex system. This call frees resources allocated by
+** sqlite3MutexInit().
+*/
+int sqlite3MutexEnd(void){
+  int rc = SQLITE_OK;
+  if( sqlite3GlobalConfig.mutex.xMutexEnd ){
+    rc = sqlite3GlobalConfig.mutex.xMutexEnd();
+  }
+
+#ifdef SQLITE_DEBUG
+  GLOBAL(int, mutexIsInit) = 0;
+#endif
+
+  return rc;
+}
+
+/*
+** Retrieve a pointer to a static mutex or allocate a new dynamic one.
+*/
+sqlite3_mutex *sqlite3_mutex_alloc(int id){
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( id<=SQLITE_MUTEX_RECURSIVE && sqlite3_initialize() ) return 0;
+  if( id>SQLITE_MUTEX_RECURSIVE && sqlite3MutexInit() ) return 0;
+#endif
+  assert( sqlite3GlobalConfig.mutex.xMutexAlloc );
+  return sqlite3GlobalConfig.mutex.xMutexAlloc(id);
+}
+
+sqlite3_mutex *sqlite3MutexAlloc(int id){
+  if( !sqlite3GlobalConfig.bCoreMutex ){
+    return 0;
+  }
+  assert( GLOBAL(int, mutexIsInit) );
+  assert( sqlite3GlobalConfig.mutex.xMutexAlloc );
+  return sqlite3GlobalConfig.mutex.xMutexAlloc(id);
+}
+
+/*
+** Free a dynamic mutex.
+*/
+void sqlite3_mutex_free(sqlite3_mutex *p){
+  if( p ){
+    assert( sqlite3GlobalConfig.mutex.xMutexFree );
+    sqlite3GlobalConfig.mutex.xMutexFree(p);
+  }
+}
+
+/*
+** Obtain the mutex p. If some other thread already has the mutex, block
+** until it can be obtained.
+*/
+void sqlite3_mutex_enter(sqlite3_mutex *p){
+  if( p ){
+    assert( sqlite3GlobalConfig.mutex.xMutexEnter );
+    sqlite3GlobalConfig.mutex.xMutexEnter(p);
+  }
+}
+
+/*
+** Obtain the mutex p. If successful, return SQLITE_OK. Otherwise, if another
+** thread holds the mutex and it cannot be obtained, return SQLITE_BUSY.
+*/
+int sqlite3_mutex_try(sqlite3_mutex *p){
+  int rc = SQLITE_OK;
+  if( p ){
+    assert( sqlite3GlobalConfig.mutex.xMutexTry );
+    return sqlite3GlobalConfig.mutex.xMutexTry(p);
+  }
+  return rc;
+}
+
+/*
+** 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. If a NULL pointer is passed as an argument
+** this function is a no-op.
+*/
+void sqlite3_mutex_leave(sqlite3_mutex *p){
+  if( p ){
+    assert( sqlite3GlobalConfig.mutex.xMutexLeave );
+    sqlite3GlobalConfig.mutex.xMutexLeave(p);
+  }
+}
+
+#ifndef NDEBUG
+/*
+** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
+** intended for use inside assert() statements.
+*/
+int sqlite3_mutex_held(sqlite3_mutex *p){
+  assert( p==0 || sqlite3GlobalConfig.mutex.xMutexHeld );
+  return p==0 || sqlite3GlobalConfig.mutex.xMutexHeld(p);
+}
+int sqlite3_mutex_notheld(sqlite3_mutex *p){
+  assert( p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld );
+  return p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld(p);
+}
+#endif
+
+#endif /* !defined(SQLITE_MUTEX_OMIT) */