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/* $Id$ */
/*
* Copyright (C)2003-2007 Benny Prijono <benny@prijono.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Note:
*
* DO NOT BUILD THIS FILE DIRECTLY. THIS FILE WILL BE INCLUDED BY os_core_*.c
* WHEN MACRO PJ_EMULATE_RWMUTEX IS SET.
*/
/*
* os_rwmutex.c:
*
* Implementation of Read-Write mutex for platforms that lack it (e.g.
* Win32, RTEMS).
*/
struct pj_rwmutex_t
{
pj_mutex_t *read_lock;
/* write_lock must use semaphore, because write_lock may be released
* by thread other than the thread that acquire the write_lock in the
* first place.
*/
pj_sem_t *write_lock;
pj_int32_t reader_count;
};
/*
* Create reader/writer mutex.
*
*/
PJ_DEF(pj_status_t) pj_rwmutex_create(pj_pool_t *pool, const char *name,
pj_rwmutex_t **p_mutex)
{
pj_status_t status;
pj_rwmutex_t *rwmutex;
PJ_ASSERT_RETURN(pool && p_mutex, PJ_EINVAL);
*p_mutex = NULL;
rwmutex = pj_pool_alloc(pool, sizeof(struct pj_rwmutex_t));
status = pj_mutex_create_simple(pool, name, &rwmutex ->read_lock);
if (status != PJ_SUCCESS)
return status;
status = pj_sem_create(pool, name, 1, 1, &rwmutex->write_lock);
if (status != PJ_SUCCESS) {
pj_mutex_destroy(rwmutex->read_lock);
return status;
}
rwmutex->reader_count = 0;
*p_mutex = rwmutex;
return PJ_SUCCESS;
}
/*
* Lock the mutex for reading.
*
*/
PJ_DEF(pj_status_t) pj_rwmutex_lock_read(pj_rwmutex_t *mutex)
{
pj_status_t status;
PJ_ASSERT_RETURN(mutex, PJ_EINVAL);
status = pj_mutex_lock(mutex->read_lock);
if (status != PJ_SUCCESS) {
pj_assert(!"This pretty much is unexpected");
return status;
}
mutex->reader_count++;
pj_assert(mutex->reader_count < 0x7FFFFFF0L);
if (mutex->reader_count == 1)
pj_sem_wait(mutex->write_lock);
status = pj_mutex_unlock(mutex->read_lock);
return status;
}
/*
* Lock the mutex for writing.
*
*/
PJ_DEF(pj_status_t) pj_rwmutex_lock_write(pj_rwmutex_t *mutex)
{
PJ_ASSERT_RETURN(mutex, PJ_EINVAL);
return pj_sem_wait(mutex->write_lock);
}
/*
* Release read lock.
*
*/
PJ_DEF(pj_status_t) pj_rwmutex_unlock_read(pj_rwmutex_t *mutex)
{
pj_status_t status;
PJ_ASSERT_RETURN(mutex, PJ_EINVAL);
status = pj_mutex_lock(mutex->read_lock);
if (status != PJ_SUCCESS) {
pj_assert(!"This pretty much is unexpected");
return status;
}
pj_assert(mutex->reader_count >= 1);
--mutex->reader_count;
if (mutex->reader_count == 0)
pj_sem_post(mutex->write_lock);
status = pj_mutex_unlock(mutex->read_lock);
return status;
}
/*
* Release write lock.
*
*/
PJ_DEF(pj_status_t) pj_rwmutex_unlock_write(pj_rwmutex_t *mutex)
{
PJ_ASSERT_RETURN(mutex, PJ_EINVAL);
pj_assert(mutex->reader_count <= 1);
return pj_sem_post(mutex->write_lock);
}
/*
* Destroy reader/writer mutex.
*
*/
PJ_DEF(pj_status_t) pj_rwmutex_destroy(pj_rwmutex_t *mutex)
{
PJ_ASSERT_RETURN(mutex, PJ_EINVAL);
pj_mutex_destroy(mutex->read_lock);
pj_sem_destroy(mutex->write_lock);
return PJ_SUCCESS;
}
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