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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 */