diff options
Diffstat (limited to 'src/mutex.c')
-rw-r--r-- | src/mutex.c | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/src/mutex.c b/src/mutex.c new file mode 100644 index 0000000..869a4ae --- /dev/null +++ b/src/mutex.c @@ -0,0 +1,153 @@ +/* +** 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 */ |