| /* |
| ** 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 */ |
| |
| |
| #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(); |
| } |
| memcpy(pTo, pFrom, offsetof(sqlite3_mutex_methods, xMutexAlloc)); |
| memcpy(&pTo->xMutexFree, &pFrom->xMutexFree, |
| sizeof(*pTo) - offsetof(sqlite3_mutex_methods, xMutexFree)); |
| pTo->xMutexAlloc = pFrom->xMutexAlloc; |
| } |
| 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( sqlite3_initialize() ) return 0; |
| #endif |
| return sqlite3GlobalConfig.mutex.xMutexAlloc(id); |
| } |
| |
| sqlite3_mutex *sqlite3MutexAlloc(int id){ |
| if( !sqlite3GlobalConfig.bCoreMutex ){ |
| return 0; |
| } |
| assert( GLOBAL(int, mutexIsInit) ); |
| return sqlite3GlobalConfig.mutex.xMutexAlloc(id); |
| } |
| |
| /* |
| ** Free a dynamic mutex. |
| */ |
| void sqlite3_mutex_free(sqlite3_mutex *p){ |
| if( p ){ |
| 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 ){ |
| 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 ){ |
| 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 ){ |
| 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){ |
| return p==0 || sqlite3GlobalConfig.mutex.xMutexHeld(p); |
| } |
| int sqlite3_mutex_notheld(sqlite3_mutex *p){ |
| return p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld(p); |
| } |
| #endif |
| |
| #endif /* SQLITE_MUTEX_OMIT */ |