/*
** 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.
**
** $Id: mutex_noop.c,v 1.3 2008/12/05 17:17:08 drh Exp $
*/
#include "sqliteInt.h"
#if defined(SQLITE_MUTEX_NOOP) && !defined(SQLITE_DEBUG)
/*
** Stub routines for all mutex methods.
**
** This routines provide no mutual exclusion or error checking.
*/
static int noopMutexHeld(sqlite3_mutex *p){ return 1; }
static int noopMutexNotheld(sqlite3_mutex *p){ return 1; }
static int noopMutexInit(void){ return SQLITE_OK; }
static int noopMutexEnd(void){ return SQLITE_OK; }
static sqlite3_mutex *noopMutexAlloc(int id){ return (sqlite3_mutex*)8; }
static void noopMutexFree(sqlite3_mutex *p){ return; }
static void noopMutexEnter(sqlite3_mutex *p){ return; }
static int noopMutexTry(sqlite3_mutex *p){ return SQLITE_OK; }
static void noopMutexLeave(sqlite3_mutex *p){ return; }
sqlite3_mutex_methods *sqlite3DefaultMutex(void){
static sqlite3_mutex_methods sMutex = {
noopMutexInit,
noopMutexEnd,
noopMutexAlloc,
noopMutexFree,
noopMutexEnter,
noopMutexTry,
noopMutexLeave,
noopMutexHeld,
noopMutexNotheld
};
return &sMutex;
}
#endif /* defined(SQLITE_MUTEX_NOOP) && !defined(SQLITE_DEBUG) */
#if defined(SQLITE_MUTEX_NOOP) && defined(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
*/
struct sqlite3_mutex {
int id; /* The mutex type */
int cnt; /* Number of entries without a matching leave */
};
/*
** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
** intended for use inside assert() statements.
*/
static int debugMutexHeld(sqlite3_mutex *p){
return p==0 || p->cnt>0;
}
static int debugMutexNotheld(sqlite3_mutex *p){
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_mutex aStatic[6];
sqlite3_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: {
assert( id-2 >= 0 );
assert( id-2 < (int)(sizeof(aStatic)/sizeof(aStatic[0])) );
pNew = &aStatic[id-2];
pNew->id = id;
break;
}
}
return pNew;
}
/*
** This routine deallocates a previously allocated mutex.
*/
static void debugMutexFree(sqlite3_mutex *p){
assert( p->cnt==0 );
assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE );
sqlite3_free(p);
}
/*
** 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 *p){
assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(p) );
p->cnt++;
}
static int debugMutexTry(sqlite3_mutex *p){
assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(p) );
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 *p){
assert( debugMutexHeld(p) );
p->cnt--;
assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(p) );
}
sqlite3_mutex_methods *sqlite3DefaultMutex(void){
static sqlite3_mutex_methods sMutex = {
debugMutexInit,
debugMutexEnd,
debugMutexAlloc,
debugMutexFree,
debugMutexEnter,
debugMutexTry,
debugMutexLeave,
debugMutexHeld,
debugMutexNotheld
};
return &sMutex;
}
#endif /* defined(SQLITE_MUTEX_NOOP) && defined(SQLITE_DEBUG) */