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/* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef APR_THREAD_RWLOCK_H
#define APR_THREAD_RWLOCK_H
/**
* @file apr_thread_rwlock.h
* @brief APR Reader/Writer Lock Routines
*/
#include "apr.h"
#include "apr_pools.h"
#include "apr_errno.h"
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
#if APR_HAS_THREADS
/**
* @defgroup apr_thread_rwlock Reader/Writer Lock Routines
* @ingroup APR
* @{
*/
/** Opaque read-write thread-safe lock. */
typedef struct apr_thread_rwlock_t apr_thread_rwlock_t;
/**
* Note: The following operations have undefined results: unlocking a
* read-write lock which is not locked in the calling thread; write
* locking a read-write lock which is already locked by the calling
* thread; destroying a read-write lock more than once; clearing or
* destroying the pool from which a <b>locked</b> read-write lock is
* allocated.
*/
/**
* Create and initialize a read-write lock that can be used to synchronize
* threads.
* @param rwlock the memory address where the newly created readwrite lock
* will be stored.
* @param pool the pool from which to allocate the mutex.
*/
APR_DECLARE(apr_status_t) apr_thread_rwlock_create(apr_thread_rwlock_t **rwlock,
apr_pool_t *pool);
/**
* Acquire a shared-read lock on the given read-write lock. This will allow
* multiple threads to enter the same critical section while they have acquired
* the read lock.
* @param rwlock the read-write lock on which to acquire the shared read.
*/
APR_DECLARE(apr_status_t) apr_thread_rwlock_rdlock(apr_thread_rwlock_t *rwlock);
/**
* Attempt to acquire the shared-read lock on the given read-write lock. This
* is the same as apr_thread_rwlock_rdlock(), only that the function fails
* if there is another thread holding the write lock, or if there are any
* write threads blocking on the lock. If the function fails for this case,
* APR_EBUSY will be returned. Note: it is important that the
* APR_STATUS_IS_EBUSY(s) macro be used to determine if the return value was
* APR_EBUSY, for portability reasons.
* @param rwlock the rwlock on which to attempt the shared read.
*/
APR_DECLARE(apr_status_t) apr_thread_rwlock_tryrdlock(apr_thread_rwlock_t *rwlock);
/**
* Acquire an exclusive-write lock on the given read-write lock. This will
* allow only one single thread to enter the critical sections. If there
* are any threads currently holding the read-lock, this thread is put to
* sleep until it can have exclusive access to the lock.
* @param rwlock the read-write lock on which to acquire the exclusive write.
*/
APR_DECLARE(apr_status_t) apr_thread_rwlock_wrlock(apr_thread_rwlock_t *rwlock);
/**
* Attempt to acquire the exclusive-write lock on the given read-write lock.
* This is the same as apr_thread_rwlock_wrlock(), only that the function fails
* if there is any other thread holding the lock (for reading or writing),
* in which case the function will return APR_EBUSY. Note: it is important
* that the APR_STATUS_IS_EBUSY(s) macro be used to determine if the return
* value was APR_EBUSY, for portability reasons.
* @param rwlock the rwlock on which to attempt the exclusive write.
*/
APR_DECLARE(apr_status_t) apr_thread_rwlock_trywrlock(apr_thread_rwlock_t *rwlock);
/**
* Release either the read or write lock currently held by the calling thread
* associated with the given read-write lock.
* @param rwlock the read-write lock to be released (unlocked).
*/
APR_DECLARE(apr_status_t) apr_thread_rwlock_unlock(apr_thread_rwlock_t *rwlock);
/**
* Destroy the read-write lock and free the associated memory.
* @param rwlock the rwlock to destroy.
*/
APR_DECLARE(apr_status_t) apr_thread_rwlock_destroy(apr_thread_rwlock_t *rwlock);
/**
* Get the pool used by this thread_rwlock.
* @return apr_pool_t the pool
*/
APR_POOL_DECLARE_ACCESSOR(thread_rwlock);
#endif /* APR_HAS_THREADS */
/** @} */
#ifdef __cplusplus
}
#endif
#endif /* ! APR_THREAD_RWLOCK_H */
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