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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_ATOMIC_H
#define APR_ATOMIC_H
/**
* @file apr_atomic.h
* @brief APR Atomic Operations
*/
#include "apr.h"
#include "apr_pools.h"
#ifdef __cplusplus
extern "C" {
#endif
/**
* @defgroup apr_atomic Atomic Operations
* @ingroup APR
* @{
*/
/**
* this function is required on some platforms to initialize the
* atomic operation's internal structures
* @param p pool
* @return APR_SUCCESS on successful completion
* @remark Programs do NOT need to call this directly. APR will call this
* automatically from apr_initialize.
* @internal
*/
APR_DECLARE(apr_status_t) apr_atomic_init(apr_pool_t *p);
/*
* Atomic operations on 32-bit values
* Note: Each of these functions internally implements a memory barrier
* on platforms that require it
*/
/**
* atomically read an apr_uint32_t from memory
* @param mem the pointer
*/
APR_DECLARE(apr_uint32_t) apr_atomic_read32(volatile apr_uint32_t *mem);
/**
* atomically set an apr_uint32_t in memory
* @param mem pointer to the object
* @param val value that the object will assume
*/
APR_DECLARE(void) apr_atomic_set32(volatile apr_uint32_t *mem, apr_uint32_t val);
/**
* atomically add 'val' to an apr_uint32_t
* @param mem pointer to the object
* @param val amount to add
* @return old value pointed to by mem
*/
APR_DECLARE(apr_uint32_t) apr_atomic_add32(volatile apr_uint32_t *mem, apr_uint32_t val);
/**
* atomically subtract 'val' from an apr_uint32_t
* @param mem pointer to the object
* @param val amount to subtract
*/
APR_DECLARE(void) apr_atomic_sub32(volatile apr_uint32_t *mem, apr_uint32_t val);
/**
* atomically increment an apr_uint32_t by 1
* @param mem pointer to the object
* @return old value pointed to by mem
*/
APR_DECLARE(apr_uint32_t) apr_atomic_inc32(volatile apr_uint32_t *mem);
/**
* atomically decrement an apr_uint32_t by 1
* @param mem pointer to the atomic value
* @return zero if the value becomes zero on decrement, otherwise non-zero
*/
APR_DECLARE(int) apr_atomic_dec32(volatile apr_uint32_t *mem);
/**
* compare an apr_uint32_t's value with 'cmp'.
* If they are the same swap the value with 'with'
* @param mem pointer to the value
* @param with what to swap it with
* @param cmp the value to compare it to
* @return the old value of *mem
*/
APR_DECLARE(apr_uint32_t) apr_atomic_cas32(volatile apr_uint32_t *mem, apr_uint32_t with,
apr_uint32_t cmp);
/**
* exchange an apr_uint32_t's value with 'val'.
* @param mem pointer to the value
* @param val what to swap it with
* @return the old value of *mem
*/
APR_DECLARE(apr_uint32_t) apr_atomic_xchg32(volatile apr_uint32_t *mem, apr_uint32_t val);
/**
* compare the pointer's value with cmp.
* If they are the same swap the value with 'with'
* @param mem pointer to the pointer
* @param with what to swap it with
* @param cmp the value to compare it to
* @return the old value of the pointer
*/
APR_DECLARE(void*) apr_atomic_casptr(volatile void **mem, void *with, const void *cmp);
/**
* exchange a pair of pointer values
* @param mem pointer to the pointer
* @param with what to swap it with
* @return the old value of the pointer
*/
APR_DECLARE(void*) apr_atomic_xchgptr(volatile void **mem, void *with);
/** @} */
#ifdef __cplusplus
}
#endif
#endif /* !APR_ATOMIC_H */
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