diff options
Diffstat (limited to 'pjlib/src/pj/os_rwmutex.c')
| -rw-r--r-- | pjlib/src/pj/os_rwmutex.c | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/pjlib/src/pj/os_rwmutex.c b/pjlib/src/pj/os_rwmutex.c new file mode 100644 index 0000000..d392353 --- /dev/null +++ b/pjlib/src/pj/os_rwmutex.c @@ -0,0 +1,163 @@ +/* $Id: os_rwmutex.c 3553 2011-05-05 06:14:19Z nanang $ */ +/* + * Copyright (C) 2008-2011 Teluu Inc. (http://www.teluu.com) + * Copyright (C) 2003-2008 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_T(pool, 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; +} + |