127 lines
3.7 KiB
C
Executable File
127 lines
3.7 KiB
C
Executable File
/*
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** 2007 August 14
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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** This file contains the C functions that implement mutexes.
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**
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** The implementation in this file does not provide any mutual
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** exclusion and is thus suitable for use only in applications
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** that use SQLite in a single thread. But this implementation
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** does do a lot of error checking on mutexes to make sure they
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** are called correctly and at appropriate times. Hence, this
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** implementation is suitable for testing.
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** debugging purposes
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**
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** $Id: mutex.c,v 1.16 2007/09/10 16:13:00 danielk1977 Exp $
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*/
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#include "sqliteInt.h"
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#ifdef SQLITE_MUTEX_NOOP_DEBUG
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/*
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** In this implementation, mutexes do not provide any mutual exclusion.
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** But the error checking is provided. This implementation is useful
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** for test purposes.
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*/
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/*
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** The mutex object
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*/
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struct sqlite3_mutex {
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int id; /* The mutex type */
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int cnt; /* Number of entries without a matching leave */
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};
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/*
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** The sqlite3_mutex_alloc() routine allocates a new
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** mutex and returns a pointer to it. If it returns NULL
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** that means that a mutex could not be allocated.
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*/
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sqlite3_mutex *sqlite3_mutex_alloc(int id){
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static sqlite3_mutex aStatic[5];
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sqlite3_mutex *pNew = 0;
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switch( id ){
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case SQLITE_MUTEX_FAST:
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case SQLITE_MUTEX_RECURSIVE: {
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pNew = sqlite3_malloc(sizeof(*pNew));
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if( pNew ){
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pNew->id = id;
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pNew->cnt = 0;
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}
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break;
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}
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default: {
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assert( id-2 >= 0 );
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assert( id-2 < sizeof(aStatic)/sizeof(aStatic[0]) );
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pNew = &aStatic[id-2];
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pNew->id = id;
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break;
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}
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}
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return pNew;
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}
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/*
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** This routine deallocates a previously allocated mutex.
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*/
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void sqlite3_mutex_free(sqlite3_mutex *p){
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assert( p );
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assert( p->cnt==0 );
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assert( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE );
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sqlite3_free(p);
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}
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/*
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** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
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** to enter a mutex. If another thread is already within the mutex,
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** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
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** SQLITE_BUSY. The sqlite3_mutex_try() interface returns SQLITE_OK
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** upon successful entry. Mutexes created using SQLITE_MUTEX_RECURSIVE can
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** be entered multiple times by the same thread. In such cases the,
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** mutex must be exited an equal number of times before another thread
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** can enter. If the same thread tries to enter any other kind of mutex
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** more than once, the behavior is undefined.
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*/
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void sqlite3_mutex_enter(sqlite3_mutex *p){
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assert( p );
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assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
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p->cnt++;
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}
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int sqlite3_mutex_try(sqlite3_mutex *p){
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assert( p );
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assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
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p->cnt++;
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return SQLITE_OK;
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}
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/*
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** The sqlite3_mutex_leave() routine exits a mutex that was
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** previously entered by the same thread. The behavior
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** is undefined if the mutex is not currently entered or
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** is not currently allocated. SQLite will never do either.
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*/
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void sqlite3_mutex_leave(sqlite3_mutex *p){
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assert( p );
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assert( sqlite3_mutex_held(p) );
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p->cnt--;
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assert( p->id==SQLITE_MUTEX_RECURSIVE || sqlite3_mutex_notheld(p) );
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}
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/*
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** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
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** intended for use inside assert() statements.
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*/
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int sqlite3_mutex_held(sqlite3_mutex *p){
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return p==0 || p->cnt>0;
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}
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int sqlite3_mutex_notheld(sqlite3_mutex *p){
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return p==0 || p->cnt==0;
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}
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#endif /* SQLITE_MUTEX_NOOP_DEBUG */
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