/*+
−
** 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.+
−
**+
−
** The 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.  But this implementation+
−
** does do a lot of error checking on mutexes to make sure they+
−
** are called correctly and at appropriate times.  Hence, this+
−
** implementation is suitable for testing.+
−
** debugging purposes+
−
**+
−
** $Id: mutex.cpp 1282 2008-11-13 09:31:33Z LarsPson $+
−
*/+
−
#include "sqliteInt.h"+
−
+
−
#ifdef SQLITE_MUTEX_NOOP_DEBUG+
−
/*+
−
** In this implementation, mutexes do not provide any mutual exclusion.+
−
** But the error checking is provided.  This implementation is useful+
−
** for test purposes.+
−
*/+
−
+
−
/*+
−
** The mutex object+
−
*/+
−
struct sqlite3_mutex {+
−
  int id;     /* The mutex type */+
−
  int cnt;    /* Number of entries without a matching leave */+
−
};+
−
+
−
/*+
−
** 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. +
−
*/+
−
sqlite3_mutex *sqlite3_mutex_alloc(int id){+
−
  static sqlite3_mutex aStatic[5];+
−
  sqlite3_mutex *pNew = 0;+
−
  switch( id ){+
−
    case SQLITE_MUTEX_FAST:+
−
    case SQLITE_MUTEX_RECURSIVE: {+
−
      pNew = sqlite3_malloc(sizeof(*pNew));+
−
      if( pNew ){+
−
        pNew->id = id;+
−
        pNew->cnt = 0;+
−
      }+
−
      break;+
−
    }+
−
    default: {+
−
      assert( id-2 >= 0 );+
−
      assert( id-2 < sizeof(aStatic)/sizeof(aStatic[0]) );+
−
      pNew = &aStatic[id-2];+
−
      pNew->id = id;+
−
      break;+
−
    }+
−
  }+
−
  return pNew;+
−
}+
−
+
−
/*+
−
** This routine deallocates a previously allocated mutex.+
−
*/+
−
void sqlite3_mutex_free(sqlite3_mutex *p){+
−
  assert( 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.+
−
*/+
−
void sqlite3_mutex_enter(sqlite3_mutex *p){+
−
  assert( p );+
−
  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );+
−
  p->cnt++;+
−
}+
−
int sqlite3_mutex_try(sqlite3_mutex *p){+
−
  assert( p );+
−
  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(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.+
−
*/+
−
void sqlite3_mutex_leave(sqlite3_mutex *p){+
−
  assert( p );+
−
  assert( sqlite3_mutex_held(p) );+
−
  p->cnt--;+
−
  assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );+
−
}+
−
+
−
/*+
−
** 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->cnt>0;+
−
}+
−
int sqlite3_mutex_notheld(sqlite3_mutex *p){+
−
  return p==0 || p->cnt==0;+
−
}+
−
#endif /* SQLITE_MUTEX_NOOP_DEBUG */+
−