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+/*
+** 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
+**
+** $Id$
+*/
+#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 */