1 /* Licensed to the Apache Software Foundation (ASF) under one or more 2 * contributor license agreements. See the NOTICE file distributed with 3 * this work for additional information regarding copyright ownership. 4 * The ASF licenses this file to You under the Apache License, Version 2.0 5 * (the "License"); you may not use this file except in compliance with 6 * the License. You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef APR_ATOMIC_H 18 #define APR_ATOMIC_H 19 20 /** 21 * @file apr_atomic.h 22 * @brief APR Atomic Operations 23 */ 24 25 #include "apr.h" 26 #include "apr_pools.h" 27 28 #ifdef __cplusplus 29 extern "C" { 30 #endif 31 32 /** 33 * @defgroup apr_atomic Atomic Operations 34 * @ingroup APR 35 * @{ 36 */ 37 38 /** 39 * this function is required on some platforms to initialize the 40 * atomic operation's internal structures 41 * @param p pool 42 * @return APR_SUCCESS on successful completion 43 * @remark Programs do NOT need to call this directly. APR will call this 44 * automatically from apr_initialize. 45 * @internal 46 */ 47 APR_DECLARE(apr_status_t) apr_atomic_init(apr_pool_t *p); 48 49 /* 50 * Atomic operations on 32-bit values 51 * Note: Each of these functions internally implements a memory barrier 52 * on platforms that require it 53 */ 54 55 /** 56 * atomically read an apr_uint32_t from memory 57 * @param mem the pointer 58 */ 59 APR_DECLARE(apr_uint32_t) apr_atomic_read32(volatile apr_uint32_t *mem); 60 61 /** 62 * atomically set an apr_uint32_t in memory 63 * @param mem pointer to the object 64 * @param val value that the object will assume 65 */ 66 APR_DECLARE(void) apr_atomic_set32(volatile apr_uint32_t *mem, apr_uint32_t val); 67 68 /** 69 * atomically add 'val' to an apr_uint32_t 70 * @param mem pointer to the object 71 * @param val amount to add 72 * @return old value pointed to by mem 73 */ 74 APR_DECLARE(apr_uint32_t) apr_atomic_add32(volatile apr_uint32_t *mem, apr_uint32_t val); 75 76 /** 77 * atomically subtract 'val' from an apr_uint32_t 78 * @param mem pointer to the object 79 * @param val amount to subtract 80 */ 81 APR_DECLARE(void) apr_atomic_sub32(volatile apr_uint32_t *mem, apr_uint32_t val); 82 83 /** 84 * atomically increment an apr_uint32_t by 1 85 * @param mem pointer to the object 86 * @return old value pointed to by mem 87 */ 88 APR_DECLARE(apr_uint32_t) apr_atomic_inc32(volatile apr_uint32_t *mem); 89 90 /** 91 * atomically decrement an apr_uint32_t by 1 92 * @param mem pointer to the atomic value 93 * @return zero if the value becomes zero on decrement, otherwise non-zero 94 */ 95 APR_DECLARE(int) apr_atomic_dec32(volatile apr_uint32_t *mem); 96 97 /** 98 * compare an apr_uint32_t's value with 'cmp'. 99 * If they are the same swap the value with 'with' 100 * @param mem pointer to the value 101 * @param with what to swap it with 102 * @param cmp the value to compare it to 103 * @return the old value of *mem 104 */ 105 APR_DECLARE(apr_uint32_t) apr_atomic_cas32(volatile apr_uint32_t *mem, apr_uint32_t with, 106 apr_uint32_t cmp); 107 108 /** 109 * exchange an apr_uint32_t's value with 'val'. 110 * @param mem pointer to the value 111 * @param val what to swap it with 112 * @return the old value of *mem 113 */ 114 APR_DECLARE(apr_uint32_t) apr_atomic_xchg32(volatile apr_uint32_t *mem, apr_uint32_t val); 115 116 /** 117 * compare the pointer's value with cmp. 118 * If they are the same swap the value with 'with' 119 * @param mem pointer to the pointer 120 * @param with what to swap it with 121 * @param cmp the value to compare it to 122 * @return the old value of the pointer 123 */ 124 APR_DECLARE(void*) apr_atomic_casptr(volatile void **mem, void *with, const void *cmp); 125 126 /** 127 * exchange a pair of pointer values 128 * @param mem pointer to the pointer 129 * @param with what to swap it with 130 * @return the old value of the pointer 131 */ 132 APR_DECLARE(void*) apr_atomic_xchgptr(volatile void **mem, void *with); 133 134 /** @} */ 135 136 #ifdef __cplusplus 137 } 138 #endif 139 140 #endif /* !APR_ATOMIC_H */ 141