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_SHM_H 18 #define APR_SHM_H 19 20 /** 21 * @file apr_shm.h 22 * @brief APR Shared Memory Routines 23 */ 24 25 #include "apr.h" 26 #include "apr_pools.h" 27 #include "apr_errno.h" 28 29 #ifdef __cplusplus 30 extern "C" { 31 #endif /* __cplusplus */ 32 33 /** 34 * @defgroup apr_shm Shared Memory Routines 35 * @ingroup APR 36 * @{ 37 */ 38 39 /** 40 * Private, platform-specific data struture representing a shared memory 41 * segment. 42 */ 43 typedef struct apr_shm_t apr_shm_t; 44 45 /** 46 * Create and make accessible a shared memory segment with default 47 * properties. 48 * @param m The shared memory structure to create. 49 * @param reqsize The desired size of the segment. 50 * @param filename The file to use for shared memory on platforms that 51 * require it. 52 * @param pool the pool from which to allocate the shared memory 53 * structure. 54 * @remark A note about Anonymous vs. Named shared memory segments: 55 * Not all plaforms support anonymous shared memory segments, but in 56 * some cases it is prefered over other types of shared memory 57 * implementations. Passing a NULL 'file' parameter to this function 58 * will cause the subsystem to use anonymous shared memory segments. 59 * If such a system is not available, APR_ENOTIMPL is returned. 60 * @remark A note about allocation sizes: 61 * On some platforms it is necessary to store some metainformation 62 * about the segment within the actual segment. In order to supply 63 * the caller with the requested size it may be necessary for the 64 * implementation to request a slightly greater segment length 65 * from the subsystem. In all cases, the apr_shm_baseaddr_get() 66 * function will return the first usable byte of memory. 67 * 68 */ 69 APR_DECLARE(apr_status_t) apr_shm_create(apr_shm_t **m, 70 apr_size_t reqsize, 71 const char *filename, 72 apr_pool_t *pool); 73 74 /** 75 * Special processing flags for apr_shm_create_ex() and apr_shm_attach_ex(). 76 */ 77 #define APR_SHM_NS_LOCAL 1 /* Create or attach to named shared memory 78 * segment in the "Local" namespace on 79 * Windows. (Ignored on other platforms.) 80 * By default, the "Global" namespace is 81 * used for privileged processes and the 82 * "Local" namespace is used otherwise. 83 */ 84 #define APR_SHM_NS_GLOBAL 2 /* Create or attach to named shared memory 85 * segment in the "Global" namespace on 86 * Windows. (Ignored on other platforms.) 87 */ 88 89 /** 90 * Create and make accessible a shared memory segment with platform- 91 * specific processing. 92 * @param m The shared memory structure to create. 93 * @param reqsize The desired size of the segment. 94 * @param filename The file to use for shared memory on platforms that 95 * require it. 96 * @param pool the pool from which to allocate the shared memory 97 * structure. 98 * @param flags mask of APR_SHM_* (defined above) 99 * @remark A note about Anonymous vs. Named shared memory segments: 100 * Not all plaforms support anonymous shared memory segments, but in 101 * some cases it is prefered over other types of shared memory 102 * implementations. Passing a NULL 'file' parameter to this function 103 * will cause the subsystem to use anonymous shared memory segments. 104 * If such a system is not available, APR_ENOTIMPL is returned. 105 * @remark A note about allocation sizes: 106 * On some platforms it is necessary to store some metainformation 107 * about the segment within the actual segment. In order to supply 108 * the caller with the requested size it may be necessary for the 109 * implementation to request a slightly greater segment length 110 * from the subsystem. In all cases, the apr_shm_baseaddr_get() 111 * function will return the first usable byte of memory. 112 * 113 */ 114 APR_DECLARE(apr_status_t) apr_shm_create_ex(apr_shm_t **m, 115 apr_size_t reqsize, 116 const char *filename, 117 apr_pool_t *pool, 118 apr_int32_t flags); 119 120 /** 121 * Remove named resource associated with a shared memory segment, 122 * preventing attachments to the resource, but not destroying it. 123 * @param filename The filename associated with shared-memory segment which 124 * needs to be removed 125 * @param pool The pool used for file operations 126 * @remark This function is only supported on platforms which support 127 * name-based shared memory segments, and will return APR_ENOTIMPL on 128 * platforms without such support. Removing the file while the shm 129 * is in use is not entirely portable, caller may use this to enhance 130 * obscurity of the resource, but be prepared for the call to fail, 131 * and for concurrent attempts to create a resource of the same name 132 * to also fail. The pool cleanup of apr_shm_create (apr_shm_destroy) 133 * also removes the named resource. 134 */ 135 APR_DECLARE(apr_status_t) apr_shm_remove(const char *filename, 136 apr_pool_t *pool); 137 138 /** 139 * Destroy a shared memory segment and associated memory. 140 * @param m The shared memory segment structure to destroy. 141 */ 142 APR_DECLARE(apr_status_t) apr_shm_destroy(apr_shm_t *m); 143 144 /** 145 * Attach to a shared memory segment that was created 146 * by another process. 147 * @param m The shared memory structure to create. 148 * @param filename The file used to create the original segment. 149 * (This MUST match the original filename.) 150 * @param pool the pool from which to allocate the shared memory 151 * structure for this process. 152 */ 153 APR_DECLARE(apr_status_t) apr_shm_attach(apr_shm_t **m, 154 const char *filename, 155 apr_pool_t *pool); 156 157 /** 158 * Attach to a shared memory segment that was created 159 * by another process, with platform-specific processing. 160 * @param m The shared memory structure to create. 161 * @param filename The file used to create the original segment. 162 * (This MUST match the original filename.) 163 * @param pool the pool from which to allocate the shared memory 164 * structure for this process. 165 * @param flags mask of APR_SHM_* (defined above) 166 */ 167 APR_DECLARE(apr_status_t) apr_shm_attach_ex(apr_shm_t **m, 168 const char *filename, 169 apr_pool_t *pool, 170 apr_int32_t flags); 171 172 /** 173 * Detach from a shared memory segment without destroying it. 174 * @param m The shared memory structure representing the segment 175 * to detach from. 176 */ 177 APR_DECLARE(apr_status_t) apr_shm_detach(apr_shm_t *m); 178 179 /** 180 * Retrieve the base address of the shared memory segment. 181 * NOTE: This address is only usable within the callers address 182 * space, since this API does not guarantee that other attaching 183 * processes will maintain the same address mapping. 184 * @param m The shared memory segment from which to retrieve 185 * the base address. 186 * @return address, aligned by APR_ALIGN_DEFAULT. 187 */ 188 APR_DECLARE(void *) apr_shm_baseaddr_get(const apr_shm_t *m); 189 190 /** 191 * Retrieve the length of a shared memory segment in bytes. 192 * @param m The shared memory segment from which to retrieve 193 * the segment length. 194 */ 195 APR_DECLARE(apr_size_t) apr_shm_size_get(const apr_shm_t *m); 196 197 /** 198 * Get the pool used by this shared memory segment. 199 */ 200 APR_POOL_DECLARE_ACCESSOR(shm); 201 202 /** @} */ 203 204 #ifdef __cplusplus 205 } 206 #endif 207 208 #endif /* APR_SHM_T */ 209