include/apr-0/apr_shm.h

   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 accessable a shared memory segment.
  47  * @param m The shared memory structure to create.
  48  * @param reqsize The desired size of the segment.
  49  * @param filename The file to use for shared memory on platforms that
  50  *        require it.
  51  * @param pool the pool from which to allocate the shared memory
  52  *        structure.
  53  * @remark A note about Anonymous vs. Named shared memory segments:
  54  *         Not all plaforms support anonymous shared memory segments, but in
  55  *         some cases it is prefered over other types of shared memory
  56  *         implementations. Passing a NULL 'file' parameter to this function
  57  *         will cause the subsystem to use anonymous shared memory segments.
  58  *         If such a system is not available, APR_ENOTIMPL is returned.
  59  * @remark A note about allocation sizes:
  60  *         On some platforms it is necessary to store some metainformation
  61  *         about the segment within the actual segment. In order to supply
  62  *         the caller with the requested size it may be necessary for the
  63  *         implementation to request a slightly greater segment length
  64  *         from the subsystem. In all cases, the apr_shm_baseaddr_get()
  65  *         function will return the first usable byte of memory.
  66  *
  67  */
  68 APR_DECLARE(apr_status_t) apr_shm_create(apr_shm_t **m,
  69                                          apr_size_t reqsize,
  70                                          const char *filename,
  71                                          apr_pool_t *pool);
  72
  73 /**
  74  * Destroy a shared memory segment and associated memory.
  75  * @param m The shared memory segment structure to destroy.
  76  */
  77 APR_DECLARE(apr_status_t) apr_shm_destroy(apr_shm_t *m);
  78
  79 /**
  80  * Attach to a shared memory segment that was created
  81  * by another process.
  82  * @param m The shared memory structure to create.
  83  * @param filename The file used to create the original segment.
  84  *        (This MUST match the original filename.)
  85  * @param pool the pool from which to allocate the shared memory
  86  *        structure for this process.
  87  */
  88 APR_DECLARE(apr_status_t) apr_shm_attach(apr_shm_t **m,
  89                                          const char *filename,
  90                                          apr_pool_t *pool);
  91
  92 /**
  93  * Detach from a shared memory segment without destroying it.
  94  * @param m The shared memory structure representing the segment
  95  *        to detach from.
  96  */
  97 APR_DECLARE(apr_status_t) apr_shm_detach(apr_shm_t *m);
  98
  99 /**
 100  * Retrieve the base address of the shared memory segment.
 101  * NOTE: This address is only usable within the callers address
 102  * space, since this API does not guarantee that other attaching
 103  * processes will maintain the same address mapping.
 104  * @param m The shared memory segment from which to retrieve
 105  *        the base address.
 106  */
 107 APR_DECLARE(void *) apr_shm_baseaddr_get(const apr_shm_t *m);
 108
 109 /**
 110  * Retrieve the length of a shared memory segment in bytes.
 111  * @param m The shared memory segment from which to retrieve
 112  *        the segment length.
 113  */
 114 APR_DECLARE(apr_size_t) apr_shm_size_get(const apr_shm_t *m);
 115
 116 /**
 117  * Get the pool used by this shared memory segment.
 118  */
 119 APR_POOL_DECLARE_ACCESSOR(shm);
 120
 121 /** @} */
 122
 123 #ifdef __cplusplus
 124 }
 125 #endif
 126
 127 #endif  /* APR_SHM_T */