/* 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 */
