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Diffstat (limited to 'include/apr_shm.h')
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diff --git a/include/apr_shm.h b/include/apr_shm.h new file mode 100644 index 0000000..635c654 --- /dev/null +++ b/include/apr_shm.h @@ -0,0 +1,229 @@ +/* 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" +#include "apr_perms_set.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 accessible a shared memory segment with default + * properties. + * @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); + +/** + * Special processing flags for apr_shm_create_ex() and apr_shm_attach_ex(). + */ +#define APR_SHM_NS_LOCAL 1 /* Create or attach to named shared memory + * segment in the "Local" namespace on + * Windows. (Ignored on other platforms.) + * By default, the "Global" namespace is + * used for privileged processes and the + * "Local" namespace is used otherwise. + */ +#define APR_SHM_NS_GLOBAL 2 /* Create or attach to named shared memory + * segment in the "Global" namespace on + * Windows. (Ignored on other platforms.) + */ + +/** + * Create and make accessible a shared memory segment with platform- + * specific processing. + * @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. + * @param flags mask of APR_SHM_* (defined above) + * @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_ex(apr_shm_t **m, + apr_size_t reqsize, + const char *filename, + apr_pool_t *pool, + apr_int32_t flags); + +/** + * 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 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); + +/** + * Delete named resource associated with a shared memory segment, + * preventing attachments to the resource. + * @param m The shared memory segment structure to delete. + * @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 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_delete(apr_shm_t *m); + +/** + * 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); + +/** + * Attach to a shared memory segment that was created + * by another process, with platform-specific processing. + * @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. + * @param flags mask of APR_SHM_* (defined above) + */ +APR_DECLARE(apr_status_t) apr_shm_attach_ex(apr_shm_t **m, + const char *filename, + apr_pool_t *pool, + apr_int32_t flags); + +/** + * 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); + +/** + * Set shared memory permissions. + */ +APR_PERMS_SET_IMPLEMENT(shm); + +/** + * Get the pool used by this shared memory segment. + */ +APR_POOL_DECLARE_ACCESSOR(shm); + +/** @} */ + +#ifdef __cplusplus +} +#endif + +#endif /* APR_SHM_T */ |