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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_COND_H
#define APR_THREAD_COND_H
/**
* @file apr_thread_cond.h
* @brief APR Condition Variable Routines
*/
#include "apr.h"
#include "apr_pools.h"
#include "apr_errno.h"
#include "apr_time.h"
#include "apr_thread_mutex.h"
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
#if APR_HAS_THREADS || defined(DOXYGEN)
/**
* @defgroup apr_thread_cond Condition Variable Routines
* @ingroup APR
* @{
*/
/** Opaque structure for thread condition variables */
typedef struct apr_thread_cond_t apr_thread_cond_t;
/**
* Note: destroying a condition variable (or likewise, destroying or
* clearing the pool from which a condition variable was allocated) if
* any threads are blocked waiting on it gives undefined results.
*/
/**
* Create and initialize a condition variable that can be used to signal
* and schedule threads in a single process.
* @param cond the memory address where the newly created condition variable
* will be stored.
* @param pool the pool from which to allocate the condition.
*/
APR_DECLARE(apr_status_t) apr_thread_cond_create(apr_thread_cond_t **cond,
apr_pool_t *pool);
/**
* Put the active calling thread to sleep until signaled to wake up. Each
* condition variable must be associated with a mutex, and that mutex must
* be locked before calling this function, or the behavior will be
* undefined. As the calling thread is put to sleep, the given mutex
* will be simultaneously released; and as this thread wakes up the lock
* is again simultaneously acquired.
* @param cond the condition variable on which to block.
* @param mutex the mutex that must be locked upon entering this function,
* is released while the thread is asleep, and is again acquired before
* returning from this function.
* @remark Spurious wakeups may occur. Before and after every call to wait on
* a condition variable, the caller should test whether the condition is already
* met.
*/
APR_DECLARE(apr_status_t) apr_thread_cond_wait(apr_thread_cond_t *cond,
apr_thread_mutex_t *mutex);
/**
* Put the active calling thread to sleep until signaled to wake up or
* the timeout is reached. Each condition variable must be associated
* with a mutex, and that mutex must be locked before calling this
* function, or the behavior will be undefined. As the calling thread
* is put to sleep, the given mutex will be simultaneously released;
* and as this thread wakes up the lock is again simultaneously acquired.
* @param cond the condition variable on which to block.
* @param mutex the mutex that must be locked upon entering this function,
* is released while the thread is asleep, and is again acquired before
* returning from this function.
* @param timeout The amount of time in microseconds to wait. This is
* a maximum, not a minimum. If the condition is signaled, we
* will wake up before this time, otherwise the error APR_TIMEUP
* is returned.
*/
APR_DECLARE(apr_status_t) apr_thread_cond_timedwait(apr_thread_cond_t *cond,
apr_thread_mutex_t *mutex,
apr_interval_time_t timeout);
/**
* Signals a single thread, if one exists, that is blocking on the given
* condition variable. That thread is then scheduled to wake up and acquire
* the associated mutex. Although it is not required, if predictable scheduling
* is desired, that mutex must be locked while calling this function.
* @param cond the condition variable on which to produce the signal.
* @remark If no threads are waiting on the condition variable, nothing happens.
*/
APR_DECLARE(apr_status_t) apr_thread_cond_signal(apr_thread_cond_t *cond);
/**
* Signals all threads blocking on the given condition variable.
* Each thread that was signaled is then scheduled to wake up and acquire
* the associated mutex. This will happen in a serialized manner.
* @param cond the condition variable on which to produce the broadcast.
* @remark If no threads are waiting on the condition variable, nothing happens.
*/
APR_DECLARE(apr_status_t) apr_thread_cond_broadcast(apr_thread_cond_t *cond);
/**
* Destroy the condition variable and free the associated memory.
* @param cond the condition variable to destroy.
*/
APR_DECLARE(apr_status_t) apr_thread_cond_destroy(apr_thread_cond_t *cond);
/**
* Get the pool used by this thread_cond.
* @return apr_pool_t the pool
*/
APR_POOL_DECLARE_ACCESSOR(thread_cond);
#endif /* APR_HAS_THREADS */
/** @} */
#ifdef __cplusplus
}
#endif
#endif /* ! APR_THREAD_COND_H */
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