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apr_shm.h

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00001 /* Copyright 2000-2004 The Apache Software Foundation
00002  *
00003  * Licensed under the Apache License, Version 2.0 (the "License");
00004  * you may not use this file except in compliance with the License.
00005  * You may obtain a copy of the License at
00006  *
00007  *     http://www.apache.org/licenses/LICENSE-2.0
00008  *
00009  * Unless required by applicable law or agreed to in writing, software
00010  * distributed under the License is distributed on an "AS IS" BASIS,
00011  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00012  * See the License for the specific language governing permissions and
00013  * limitations under the License.
00014  */
00015 
00016 #ifndef APR_SHM_H
00017 #define APR_SHM_H
00018 
00019 /**
00020  * @file apr_shm.h
00021  * @brief APR Shared Memory Routines
00022  */
00023 
00024 #include "apr.h"
00025 #include "apr_pools.h"
00026 #include "apr_errno.h"
00027 
00028 #ifdef __cplusplus
00029 extern "C" {
00030 #endif /* __cplusplus */
00031 
00032 /**
00033  * @defgroup apr_shm Shared Memory Routines
00034  * @ingroup APR 
00035  * @{
00036  */
00037 
00038 /**
00039  * Private, platform-specific data struture representing a shared memory
00040  * segment.
00041  */
00042 typedef struct apr_shm_t apr_shm_t;
00043 
00044 /**
00045  * Create and make accessable a shared memory segment.
00046  * @param m The shared memory structure to create.
00047  * @param reqsize The desired size of the segment.
00048  * @param filename The file to use for shared memory on platforms that
00049  *        require it.
00050  * @param pool the pool from which to allocate the shared memory
00051  *        structure.
00052  * @remark A note about Anonymous vs. Named shared memory segments:
00053  *         Not all plaforms support anonymous shared memory segments, but in
00054  *         some cases it is prefered over other types of shared memory
00055  *         implementations. Passing a NULL 'file' parameter to this function
00056  *         will cause the subsystem to use anonymous shared memory segments.
00057  *         If such a system is not available, APR_ENOTIMPL is returned.
00058  * @remark A note about allocation sizes:
00059  *         On some platforms it is necessary to store some metainformation
00060  *         about the segment within the actual segment. In order to supply
00061  *         the caller with the requested size it may be necessary for the
00062  *         implementation to request a slightly greater segment length
00063  *         from the subsystem. In all cases, the apr_shm_baseaddr_get()
00064  *         function will return the first usable byte of memory.
00065  * 
00066  */
00067 APR_DECLARE(apr_status_t) apr_shm_create(apr_shm_t **m,
00068                                          apr_size_t reqsize,
00069                                          const char *filename,
00070                                          apr_pool_t *pool);
00071 
00072 /**
00073  * Remove shared memory segment associated with a filename.
00074  * @param filename The filename associated with shared-memory segment which
00075  *        needs to be removed
00076  * @param pool The pool used for file operations
00077  * @remark This function is only supported on platforms which support
00078  * name-based shared memory segments, and will return APR_ENOTIMPL on
00079  * platforms without such support.
00080  */
00081 APR_DECLARE(apr_status_t) apr_shm_remove(const char *filename,
00082                                          apr_pool_t *pool);
00083 
00084 /**
00085  * Destroy a shared memory segment and associated memory.
00086  * @param m The shared memory segment structure to destroy.
00087  */
00088 APR_DECLARE(apr_status_t) apr_shm_destroy(apr_shm_t *m);
00089 
00090 /**
00091  * Attach to a shared memory segment that was created
00092  * by another process.
00093  * @param m The shared memory structure to create.
00094  * @param filename The file used to create the original segment.
00095  *        (This MUST match the original filename.)
00096  * @param pool the pool from which to allocate the shared memory
00097  *        structure for this process.
00098  */
00099 APR_DECLARE(apr_status_t) apr_shm_attach(apr_shm_t **m,
00100                                          const char *filename,
00101                                          apr_pool_t *pool);
00102 
00103 /**
00104  * Detach from a shared memory segment without destroying it.
00105  * @param m The shared memory structure representing the segment
00106  *        to detach from.
00107  */
00108 APR_DECLARE(apr_status_t) apr_shm_detach(apr_shm_t *m);
00109 
00110 /**
00111  * Retrieve the base address of the shared memory segment.
00112  * NOTE: This address is only usable within the callers address
00113  * space, since this API does not guarantee that other attaching
00114  * processes will maintain the same address mapping.
00115  * @param m The shared memory segment from which to retrieve
00116  *        the base address.
00117  * @return address, aligned by APR_ALIGN_DEFAULT.
00118  */
00119 APR_DECLARE(void *) apr_shm_baseaddr_get(const apr_shm_t *m);
00120 
00121 /**
00122  * Retrieve the length of a shared memory segment in bytes.
00123  * @param m The shared memory segment from which to retrieve
00124  *        the segment length.
00125  */
00126 APR_DECLARE(apr_size_t) apr_shm_size_get(const apr_shm_t *m);
00127 
00128 /**
00129  * Get the pool used by this shared memory segment.
00130  */
00131 APR_POOL_DECLARE_ACCESSOR(shm);
00132 
00133 /** @} */ 
00134 
00135 #ifdef __cplusplus
00136 }
00137 #endif
00138 
00139 #endif  /* APR_SHM_T */

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