/* Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #ifndef APR_SHM_H #define APR_SHM_H /** * @file apr_shm.h * @brief APR Shared Memory Routines */ #include "apr.h" #include "apr_pools.h" #include "apr_errno.h" #ifdef __cplusplus extern "C" { #endif /* __cplusplus */ /** * @defgroup apr_shm Shared Memory Routines * @ingroup APR * @{ */ /** * Private, platform-specific data struture representing a shared memory * segment. */ typedef struct apr_shm_t apr_shm_t; /** * Create and make accessable a shared memory segment. * @param m The shared memory structure to create. * @param reqsize The desired size of the segment. * @param filename The file to use for shared memory on platforms that * require it. * @param pool the pool from which to allocate the shared memory * structure. * @remark A note about Anonymous vs. Named shared memory segments: * Not all plaforms support anonymous shared memory segments, but in * some cases it is prefered over other types of shared memory * implementations. Passing a NULL 'file' parameter to this function * will cause the subsystem to use anonymous shared memory segments. * If such a system is not available, APR_ENOTIMPL is returned. * @remark A note about allocation sizes: * On some platforms it is necessary to store some metainformation * about the segment within the actual segment. In order to supply * the caller with the requested size it may be necessary for the * implementation to request a slightly greater segment length * from the subsystem. In all cases, the apr_shm_baseaddr_get() * function will return the first usable byte of memory. * */ APR_DECLARE(apr_status_t) apr_shm_create(apr_shm_t **m, apr_size_t reqsize, const char *filename, apr_pool_t *pool); /** * Remove named resource associated with a shared memory segment, * preventing attachments to the resource, but not destroying it. * @param filename The filename associated with shared-memory segment which * needs to be removed * @param pool The pool used for file operations * @remark This function is only supported on platforms which support * name-based shared memory segments, and will return APR_ENOTIMPL on * platforms without such support. Removing the file while the shm * is in use is not entirely portable, caller may use this to enhance * obscurity of the resource, but be prepared for the the call to fail, * and for concurrent attempts to create a resource of the same name * to also fail. The pool cleanup of apr_shm_create (apr_shm_destroy) * also removes the named resource. */ APR_DECLARE(apr_status_t) apr_shm_remove(const char *filename, apr_pool_t *pool); /** * Destroy a shared memory segment and associated memory. * @param m The shared memory segment structure to destroy. */ APR_DECLARE(apr_status_t) apr_shm_destroy(apr_shm_t *m); /** * Attach to a shared memory segment that was created * by another process. * @param m The shared memory structure to create. * @param filename The file used to create the original segment. * (This MUST match the original filename.) * @param pool the pool from which to allocate the shared memory * structure for this process. */ APR_DECLARE(apr_status_t) apr_shm_attach(apr_shm_t **m, const char *filename, apr_pool_t *pool); /** * Detach from a shared memory segment without destroying it. * @param m The shared memory structure representing the segment * to detach from. */ APR_DECLARE(apr_status_t) apr_shm_detach(apr_shm_t *m); /** * Retrieve the base address of the shared memory segment. * NOTE: This address is only usable within the callers address * space, since this API does not guarantee that other attaching * processes will maintain the same address mapping. * @param m The shared memory segment from which to retrieve * the base address. * @return address, aligned by APR_ALIGN_DEFAULT. */ APR_DECLARE(void *) apr_shm_baseaddr_get(const apr_shm_t *m); /** * Retrieve the length of a shared memory segment in bytes. * @param m The shared memory segment from which to retrieve * the segment length. */ APR_DECLARE(apr_size_t) apr_shm_size_get(const apr_shm_t *m); /** * Get the pool used by this shared memory segment. */ APR_POOL_DECLARE_ACCESSOR(shm); /** @} */ #ifdef __cplusplus } #endif #endif /* APR_SHM_T */