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apr_thread_cond.h

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00001 /* Copyright 2000-2004 The Apache Software Foundation
00002  *
00003  * Licensed under the Apache License, Version 2.0 (the "License");
00004  * you may not use this file except in compliance with the License.
00005  * You may obtain a copy of the License at
00006  *
00007  *     http://www.apache.org/licenses/LICENSE-2.0
00008  *
00009  * Unless required by applicable law or agreed to in writing, software
00010  * distributed under the License is distributed on an "AS IS" BASIS,
00011  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00012  * See the License for the specific language governing permissions and
00013  * limitations under the License.
00014  */
00015 
00016 #ifndef APR_THREAD_COND_H
00017 #define APR_THREAD_COND_H
00018 
00019 /**
00020  * @file apr_thread_cond.h
00021  * @brief APR Condition Variable Routines
00022  */
00023 
00024 #include "apr.h"
00025 #include "apr_pools.h"
00026 #include "apr_errno.h"
00027 #include "apr_time.h"
00028 #include "apr_thread_mutex.h"
00029 
00030 #ifdef __cplusplus
00031 extern "C" {
00032 #endif /* __cplusplus */
00033 
00034 #if APR_HAS_THREADS || defined(DOXYGEN)
00035 
00036 /**
00037  * @defgroup apr_thread_cond Condition Variable Routines
00038  * @ingroup APR 
00039  * @{
00040  */
00041 
00042 /** Opaque structure for thread condition variables */
00043 typedef struct apr_thread_cond_t apr_thread_cond_t;
00044 
00045 /**
00046  * Note: destroying a condition variable (or likewise, destroying or
00047  * clearing the pool from which a condition variable was allocated) if
00048  * any threads are blocked waiting on it gives undefined results.
00049  */
00050 
00051 /**
00052  * Create and initialize a condition variable that can be used to signal
00053  * and schedule threads in a single process.
00054  * @param cond the memory address where the newly created condition variable
00055  *        will be stored.
00056  * @param pool the pool from which to allocate the mutex.
00057  */
00058 APR_DECLARE(apr_status_t) apr_thread_cond_create(apr_thread_cond_t **cond,
00059                                                  apr_pool_t *pool);
00060 
00061 /**
00062  * Put the active calling thread to sleep until signaled to wake up. Each
00063  * condition variable must be associated with a mutex, and that mutex must
00064  * be locked before  calling this function, or the behavior will be
00065  * undefined. As the calling thread is put to sleep, the given mutex
00066  * will be simultaneously released; and as this thread wakes up the lock
00067  * is again simultaneously acquired.
00068  * @param cond the condition variable on which to block.
00069  * @param mutex the mutex that must be locked upon entering this function,
00070  *        is released while the thread is asleep, and is again acquired before
00071  *        returning from this function.
00072  */
00073 APR_DECLARE(apr_status_t) apr_thread_cond_wait(apr_thread_cond_t *cond,
00074                                                apr_thread_mutex_t *mutex);
00075 
00076 /**
00077  * Put the active calling thread to sleep until signaled to wake up or
00078  * the timeout is reached. Each condition variable must be associated
00079  * with a mutex, and that mutex must be locked before calling this
00080  * function, or the behavior will be undefined. As the calling thread
00081  * is put to sleep, the given mutex will be simultaneously released;
00082  * and as this thread wakes up the lock is again simultaneously acquired.
00083  * @param cond the condition variable on which to block.
00084  * @param mutex the mutex that must be locked upon entering this function,
00085  *        is released while the thread is asleep, and is again acquired before
00086  *        returning from this function.
00087  * @param timeout The amount of time in microseconds to wait. This is 
00088  *        a maximum, not a minimum. If the condition is signaled, we 
00089  *        will wake up before this time, otherwise the error APR_TIMEUP
00090  *        is returned.
00091  */
00092 APR_DECLARE(apr_status_t) apr_thread_cond_timedwait(apr_thread_cond_t *cond,
00093                                                     apr_thread_mutex_t *mutex,
00094                                                     apr_interval_time_t timeout);
00095 
00096 /**
00097  * Signals a single thread, if one exists, that is blocking on the given
00098  * condition variable. That thread is then scheduled to wake up and acquire
00099  * the associated mutex. Although it is not required, if predictable scheduling
00100  * is desired, that mutex must be locked while calling this function.
00101  * @param cond the condition variable on which to produce the signal.
00102  */
00103 APR_DECLARE(apr_status_t) apr_thread_cond_signal(apr_thread_cond_t *cond);
00104 
00105 /**
00106  * Signals all threads blocking on the given condition variable.
00107  * Each thread that was signaled is then scheduled to wake up and acquire
00108  * the associated mutex. This will happen in a serialized manner.
00109  * @param cond the condition variable on which to produce the broadcast.
00110  */
00111 APR_DECLARE(apr_status_t) apr_thread_cond_broadcast(apr_thread_cond_t *cond);
00112 
00113 /**
00114  * Destroy the condition variable and free the associated memory.
00115  * @param cond the condition variable to destroy.
00116  */
00117 APR_DECLARE(apr_status_t) apr_thread_cond_destroy(apr_thread_cond_t *cond);
00118 
00119 /**
00120  * Get the pool used by this thread_cond.
00121  * @return apr_pool_t the pool
00122  */
00123 APR_POOL_DECLARE_ACCESSOR(thread_cond);
00124 
00125 #endif /* APR_HAS_THREADS */
00126 
00127 /** @} */
00128 
00129 #ifdef __cplusplus
00130 }
00131 #endif
00132 
00133 #endif  /* ! APR_THREAD_COND_H */

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