root/third_party/sqlite/src/src/mutex_noop.c

DEFINITIONS

1. noopMutexInit
2. noopMutexEnd
3. noopMutexAlloc
4. noopMutexFree
5. noopMutexEnter
6. noopMutexTry
7. noopMutexLeave
8. sqlite3NoopMutex
9. debugMutexHeld
10. debugMutexNotheld
11. debugMutexInit
12. debugMutexEnd
13. debugMutexAlloc
14. debugMutexFree
15. debugMutexEnter
16. debugMutexTry
17. debugMutexLeave
18. sqlite3NoopMutex
19. sqlite3DefaultMutex

/*
** 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[6];
  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: {
      assert( id-2 >= 0 );
      assert( id-2 < (int)(sizeof(aStatic)/sizeof(aStatic[0])) );
      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 );
  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 *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 /* SQLITE_MUTEX_NOOP */
#endif /* SQLITE_MUTEX_OMIT */