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Diffstat (limited to '')
| -rw-r--r-- | src/mutex_noop.c | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/src/mutex_noop.c b/src/mutex_noop.c new file mode 100644 index 0000000..ecc84b4 --- /dev/null +++ b/src/mutex_noop.c @@ -0,0 +1,215 @@ +/* +** 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) */ |