Apache Portable Runtime
apr_atomic.h
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00001 /* Licensed to the Apache Software Foundation (ASF) under one or more
00002  * contributor license agreements.  See the NOTICE file distributed with
00003  * this work for additional information regarding copyright ownership.
00004  * The ASF licenses this file to You under the Apache License, Version 2.0
00005  * (the "License"); you may not use this file except in compliance with
00006  * the License.  You may obtain a copy of the License at
00007  *
00008  *     http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 
00017 #ifndef APR_ATOMIC_H
00018 #define APR_ATOMIC_H
00019 
00020 /**
00021  * @file apr_atomic.h
00022  * @brief APR Atomic Operations
00023  */
00024 
00025 #include "apr.h"
00026 #include "apr_pools.h"
00027 
00028 #ifdef __cplusplus
00029 extern "C" {
00030 #endif
00031 
00032 /**
00033  * @defgroup apr_atomic Atomic Operations
00034  * @ingroup APR 
00035  * @{
00036  */
00037 
00038 /**
00039  * this function is required on some platforms to initialize the
00040  * atomic operation's internal structures
00041  * @param p pool
00042  * @return APR_SUCCESS on successful completion
00043  * @remark Programs do NOT need to call this directly. APR will call this
00044  *         automatically from apr_initialize.
00045  * @internal
00046  */
00047 APR_DECLARE(apr_status_t) apr_atomic_init(apr_pool_t *p);
00048 
00049 /*
00050  * Atomic operations on 32-bit values
00051  * Note: Each of these functions internally implements a memory barrier
00052  * on platforms that require it
00053  */
00054 
00055 /**
00056  * atomically read an apr_uint32_t from memory
00057  * @param mem the pointer
00058  */
00059 APR_DECLARE(apr_uint32_t) apr_atomic_read32(volatile apr_uint32_t *mem);
00060 
00061 /**
00062  * atomically set an apr_uint32_t in memory
00063  * @param mem pointer to the object
00064  * @param val value that the object will assume
00065  */
00066 APR_DECLARE(void) apr_atomic_set32(volatile apr_uint32_t *mem, apr_uint32_t val);
00067 
00068 /**
00069  * atomically add 'val' to an apr_uint32_t
00070  * @param mem pointer to the object
00071  * @param val amount to add
00072  * @return old value pointed to by mem
00073  */
00074 APR_DECLARE(apr_uint32_t) apr_atomic_add32(volatile apr_uint32_t *mem, apr_uint32_t val);
00075 
00076 /**
00077  * atomically subtract 'val' from an apr_uint32_t
00078  * @param mem pointer to the object
00079  * @param val amount to subtract
00080  */
00081 APR_DECLARE(void) apr_atomic_sub32(volatile apr_uint32_t *mem, apr_uint32_t val);
00082 
00083 /**
00084  * atomically increment an apr_uint32_t by 1
00085  * @param mem pointer to the object
00086  * @return old value pointed to by mem
00087  */
00088 APR_DECLARE(apr_uint32_t) apr_atomic_inc32(volatile apr_uint32_t *mem);
00089 
00090 /**
00091  * atomically decrement an apr_uint32_t by 1
00092  * @param mem pointer to the atomic value
00093  * @return zero if the value becomes zero on decrement, otherwise non-zero
00094  */
00095 APR_DECLARE(int) apr_atomic_dec32(volatile apr_uint32_t *mem);
00096 
00097 /**
00098  * compare an apr_uint32_t's value with 'cmp'.
00099  * If they are the same swap the value with 'with'
00100  * @param mem pointer to the value
00101  * @param with what to swap it with
00102  * @param cmp the value to compare it to
00103  * @return the old value of *mem
00104  */
00105 APR_DECLARE(apr_uint32_t) apr_atomic_cas32(volatile apr_uint32_t *mem, apr_uint32_t with,
00106                               apr_uint32_t cmp);
00107 
00108 /**
00109  * exchange an apr_uint32_t's value with 'val'.
00110  * @param mem pointer to the value
00111  * @param val what to swap it with
00112  * @return the old value of *mem
00113  */
00114 APR_DECLARE(apr_uint32_t) apr_atomic_xchg32(volatile apr_uint32_t *mem, apr_uint32_t val);
00115 
00116 /**
00117  * compare the pointer's value with cmp.
00118  * If they are the same swap the value with 'with'
00119  * @param mem pointer to the pointer
00120  * @param with what to swap it with
00121  * @param cmp the value to compare it to
00122  * @return the old value of the pointer
00123  */
00124 APR_DECLARE(void*) apr_atomic_casptr(volatile void **mem, void *with, const void *cmp);
00125 
00126 /**
00127  * exchange a pair of pointer values
00128  * @param mem pointer to the pointer
00129  * @param with what to swap it with
00130  * @return the old value of the pointer
00131  */
00132 APR_DECLARE(void*) apr_atomic_xchgptr(volatile void **mem, void *with);
00133 
00134 /** @} */
00135 
00136 #ifdef __cplusplus
00137 }
00138 #endif
00139 
00140 #endif  /* !APR_ATOMIC_H */
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