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/**
* @copyright
* ====================================================================
* 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.
* ====================================================================
* @endcopyright
*
* @file svn_mutex.h
* @brief Structures and functions for mutual exclusion
*/
#ifndef SVN_MUTEX_H
#define SVN_MUTEX_H
#include <apr_thread_mutex.h>
#include "svn_error.h"
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
/**
* This is a simple wrapper around @c apr_thread_mutex_t and will be a
* valid identifier even if APR does not support threading.
*/
#if APR_HAS_THREADS
/** A mutex for synchronization between threads. It may be NULL, in
* which case no synchronization will take place. The latter is useful
* when implementing some functionality with optional synchronization.
*/
typedef apr_thread_mutex_t svn_mutex__t;
#else
/** Dummy definition. The content will never be actually accessed.
*/
typedef void svn_mutex__t;
#endif
/** Initialize the @a *mutex. If @a mutex_required is TRUE, the mutex will
* actually be created with a lifetime defined by @a result_pool. Otherwise,
* the pointer will be set to @c NULL and svn_mutex__lock() as well as
* svn_mutex__unlock() will be no-ops.
*
* If threading is not supported by APR, this function is a no-op.
*/
svn_error_t *
svn_mutex__init(svn_mutex__t **mutex,
svn_boolean_t mutex_required,
apr_pool_t *result_pool);
/** Acquire the @a mutex, if that has been enabled in svn_mutex__init().
* Make sure to call svn_mutex__unlock() some time later in the same
* thread to release the mutex again. Recursive locking are not supported.
*
* @note You should use #SVN_MUTEX__WITH_LOCK instead of explicit lock
* acquisition and release.
*/
svn_error_t *
svn_mutex__lock(svn_mutex__t *mutex);
/** Release the @a mutex, previously acquired using svn_mutex__lock()
* that has been enabled in svn_mutex__init().
*
* Since this is often used as part of the calling function's exit
* sequence, we accept that function's current return code in @a err.
* If it is not #SVN_NO_ERROR, it will be used as the return value -
* irrespective of the possible internal failures during unlock. If @a err
* is #SVN_NO_ERROR, internal failures of this function will be
* reported in the return value.
*
* @note You should use #SVN_MUTEX__WITH_LOCK instead of explicit lock
* acquisition and release.
*/
svn_error_t *
svn_mutex__unlock(svn_mutex__t *mutex,
svn_error_t *err);
/** Acquires the @a mutex, executes the expression @a expr and finally
* releases the @a mutex. If any of these steps fail, the function using
* this macro will return an #svn_error_t. This macro guarantees that
* the @a mutex will always be unlocked again if it got locked successfully
* by the first step.
*
* @note Prefer using this macro instead of explicit lock acquisition and
* release.
*/
#define SVN_MUTEX__WITH_LOCK(mutex, expr) \
do { \
svn_mutex__t *svn_mutex__m = (mutex); \
SVN_ERR(svn_mutex__lock(svn_mutex__m)); \
SVN_ERR(svn_mutex__unlock(svn_mutex__m, (expr))); \
} while (0)
#ifdef __cplusplus
}
#endif /* __cplusplus */
#endif /* SVN_MUTEX_H */
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