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Diffstat (limited to 'include/apr_thread_cond.h')
| -rw-r--r-- | include/apr_thread_cond.h | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/include/apr_thread_cond.h b/include/apr_thread_cond.h new file mode 100644 index 0000000..199f1de --- /dev/null +++ b/include/apr_thread_cond.h @@ -0,0 +1,139 @@ +/* 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 */ |