SQLite

**    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 for
** use by the SQLite core.
**
** $Id: mutex.c,v 1.11 2007/08/25 14:39:46 drh Exp $
*/
/*
** If SQLITE_MUTEX_APPDEF is defined, then this whole module is
** omitted and equivalent functionality must be provided by the
** application that links against the SQLite library.
*/
#ifndef SQLITE_MUTEX_APPDEF

  return p==0 || p->cnt==0;
}
#endif /* SQLITE_MUTEX_NOOP_DEBUG */



#ifdef SQLITE_MUTEX_PTHREAD
/******************** Pthread Mutex Implementation *********************
**
** This implementation of mutexes is built using a version of pthreads that
** has native support for recursive mutexes.
*/
#include <pthread.h>

/*
** Each recursive mutex is an instance of the following structure.
*/
struct sqlite3_mutex {

    { PTHREAD_MUTEX_INITIALIZER, },
    { PTHREAD_MUTEX_INITIALIZER, },
    { PTHREAD_MUTEX_INITIALIZER, },
    { PTHREAD_MUTEX_INITIALIZER, },
  };
  sqlite3_mutex *p;
  switch( iType ){
    case SQLITE_MUTEX_RECURSIVE: {
      static pthread_mutex_t initMutex = PTHREAD_MUTEX_INITIALIZER;
      static int isInit = 0;
      static pthread_mutexattr_t recursiveAttr;
      if( !isInit ){
        pthread_mutex_lock(&initMutex);
        if( !isInit ){
          pthread_mutexattr_init(&recursiveAttr);
          pthread_mutexattr_settype(&recursiveAttr, PTHREAD_MUTEX_RECURSIVE);
        }
        isInit = 1;
        pthread_mutex_unlock(&initMutex);
      }
      p = sqlite3MallocZero( sizeof(*p) );
      if( p ){
        p->id = iType;
        pthread_mutex_init(&p->mutex, &recursiveAttr);
      }
      break;
    }
    case SQLITE_MUTEX_FAST: {
      p = sqlite3MallocZero( sizeof(*p) );
      if( p ){
        p->id = iType;
        pthread_mutex_init(&p->mutex, 0);
      }
      break;
    }

** 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.
*/
void sqlite3_mutex_enter(sqlite3_mutex *p){



  assert( p );
  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
    pthread_mutex_lock(&p->mutex);

  p->owner = pthread_self();
  p->nRef++;
  }

int sqlite3_mutex_try(sqlite3_mutex *p){

  int rc;




  assert( p );
  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
  if( pthread_mutex_trylock(&p->mutex)==0 ){
    p->owner = pthread_self();
    p->nRef++;
    rc = SQLITE_OK;
  }else{
    rc = SQLITE_BUSY;
  }
  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 or
** is not currently allocated.  SQLite will never do either.
*/
void sqlite3_mutex_leave(sqlite3_mutex *p){

  assert( p );
  assert( sqlite3_mutex_held(p) );
  p->nRef--;

    pthread_mutex_unlock(&p->mutex);
  }


/*
** 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 || (p->nRef!=0 && pthread_equal(p->owner, pthread_self()));

** 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.
*/
void sqlite3_mutex_enter(sqlite3_mutex *p){
  assert( p );
  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
  EnterCriticalSection(&p->mutex);
  p->owner = GetCurrentThreadId(); 
  p->nRef++;
}
int sqlite3_mutex_try(sqlite3_mutex *p){
  int rc;
  assert( p );
  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
  if( TryEnterCriticalSection(&p->mutex) ){
    p->owner = GetCurrentThreadId();
    p->nRef++;
    rc = SQLITE_OK;
  }else{
    rc = SQLITE_BUSY;
  }

/*
** 2001 September 15
**
** 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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.600 2007/08/25 14:39:46 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_
#include "sqliteLimit.h"

#define _XOPEN_SOURCE 500  /* Needed to enable pthread recursive mutexes */

#if defined(SQLITE_TCL) || defined(TCLSH)
# include <tcl.h>
#endif

/*
** Many people are failing to set -DNDEBUG=1 when compiling SQLite.