209 lines
8.4 KiB
C
209 lines
8.4 KiB
C
/* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef APR_SHM_H
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#define APR_SHM_H
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/**
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* @file apr_shm.h
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* @brief APR Shared Memory Routines
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*/
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#include "apr.h"
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#include "apr_pools.h"
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#include "apr_errno.h"
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#ifdef __cplusplus
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extern "C" {
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#endif /* __cplusplus */
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/**
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* @defgroup apr_shm Shared Memory Routines
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* @ingroup APR
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* @{
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*/
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/**
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* Private, platform-specific data struture representing a shared memory
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* segment.
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*/
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typedef struct apr_shm_t apr_shm_t;
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/**
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* Create and make accessible a shared memory segment with default
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* properties.
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* @param m The shared memory structure to create.
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* @param reqsize The desired size of the segment.
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* @param filename The file to use for shared memory on platforms that
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* require it.
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* @param pool the pool from which to allocate the shared memory
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* structure.
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* @remark A note about Anonymous vs. Named shared memory segments:
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* Not all plaforms support anonymous shared memory segments, but in
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* some cases it is prefered over other types of shared memory
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* implementations. Passing a NULL 'file' parameter to this function
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* will cause the subsystem to use anonymous shared memory segments.
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* If such a system is not available, APR_ENOTIMPL is returned.
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* @remark A note about allocation sizes:
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* On some platforms it is necessary to store some metainformation
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* about the segment within the actual segment. In order to supply
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* the caller with the requested size it may be necessary for the
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* implementation to request a slightly greater segment length
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* from the subsystem. In all cases, the apr_shm_baseaddr_get()
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* function will return the first usable byte of memory.
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*
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*/
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APR_DECLARE(apr_status_t) apr_shm_create(apr_shm_t **m,
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apr_size_t reqsize,
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const char *filename,
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apr_pool_t *pool);
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/**
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* Special processing flags for apr_shm_create_ex() and apr_shm_attach_ex().
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*/
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#define APR_SHM_NS_LOCAL 1 /* Create or attach to named shared memory
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* segment in the "Local" namespace on
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* Windows. (Ignored on other platforms.)
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* By default, the "Global" namespace is
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* used for privileged processes and the
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* "Local" namespace is used otherwise.
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*/
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#define APR_SHM_NS_GLOBAL 2 /* Create or attach to named shared memory
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* segment in the "Global" namespace on
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* Windows. (Ignored on other platforms.)
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*/
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/**
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* Create and make accessible a shared memory segment with platform-
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* specific processing.
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* @param m The shared memory structure to create.
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* @param reqsize The desired size of the segment.
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* @param filename The file to use for shared memory on platforms that
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* require it.
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* @param pool the pool from which to allocate the shared memory
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* structure.
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* @param flags mask of APR_SHM_* (defined above)
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* @remark A note about Anonymous vs. Named shared memory segments:
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* Not all plaforms support anonymous shared memory segments, but in
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* some cases it is prefered over other types of shared memory
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* implementations. Passing a NULL 'file' parameter to this function
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* will cause the subsystem to use anonymous shared memory segments.
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* If such a system is not available, APR_ENOTIMPL is returned.
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* @remark A note about allocation sizes:
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* On some platforms it is necessary to store some metainformation
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* about the segment within the actual segment. In order to supply
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* the caller with the requested size it may be necessary for the
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* implementation to request a slightly greater segment length
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* from the subsystem. In all cases, the apr_shm_baseaddr_get()
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* function will return the first usable byte of memory.
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*
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*/
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APR_DECLARE(apr_status_t) apr_shm_create_ex(apr_shm_t **m,
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apr_size_t reqsize,
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const char *filename,
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apr_pool_t *pool,
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apr_int32_t flags);
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/**
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* Remove named resource associated with a shared memory segment,
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* preventing attachments to the resource, but not destroying it.
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* @param filename The filename associated with shared-memory segment which
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* needs to be removed
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* @param pool The pool used for file operations
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* @remark This function is only supported on platforms which support
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* name-based shared memory segments, and will return APR_ENOTIMPL on
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* platforms without such support. Removing the file while the shm
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* is in use is not entirely portable, caller may use this to enhance
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* obscurity of the resource, but be prepared for the call to fail,
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* and for concurrent attempts to create a resource of the same name
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* to also fail. The pool cleanup of apr_shm_create (apr_shm_destroy)
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* also removes the named resource.
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*/
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APR_DECLARE(apr_status_t) apr_shm_remove(const char *filename,
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apr_pool_t *pool);
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/**
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* Destroy a shared memory segment and associated memory.
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* @param m The shared memory segment structure to destroy.
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*/
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APR_DECLARE(apr_status_t) apr_shm_destroy(apr_shm_t *m);
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/**
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* Attach to a shared memory segment that was created
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* by another process.
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* @param m The shared memory structure to create.
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* @param filename The file used to create the original segment.
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* (This MUST match the original filename.)
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* @param pool the pool from which to allocate the shared memory
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* structure for this process.
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*/
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APR_DECLARE(apr_status_t) apr_shm_attach(apr_shm_t **m,
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const char *filename,
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apr_pool_t *pool);
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/**
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* Attach to a shared memory segment that was created
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* by another process, with platform-specific processing.
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* @param m The shared memory structure to create.
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* @param filename The file used to create the original segment.
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* (This MUST match the original filename.)
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* @param pool the pool from which to allocate the shared memory
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* structure for this process.
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* @param flags mask of APR_SHM_* (defined above)
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*/
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APR_DECLARE(apr_status_t) apr_shm_attach_ex(apr_shm_t **m,
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const char *filename,
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apr_pool_t *pool,
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apr_int32_t flags);
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/**
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* Detach from a shared memory segment without destroying it.
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* @param m The shared memory structure representing the segment
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* to detach from.
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*/
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APR_DECLARE(apr_status_t) apr_shm_detach(apr_shm_t *m);
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/**
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* Retrieve the base address of the shared memory segment.
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* NOTE: This address is only usable within the callers address
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* space, since this API does not guarantee that other attaching
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* processes will maintain the same address mapping.
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* @param m The shared memory segment from which to retrieve
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* the base address.
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* @return address, aligned by APR_ALIGN_DEFAULT.
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*/
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APR_DECLARE(void *) apr_shm_baseaddr_get(const apr_shm_t *m);
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/**
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* Retrieve the length of a shared memory segment in bytes.
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* @param m The shared memory segment from which to retrieve
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* the segment length.
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*/
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APR_DECLARE(apr_size_t) apr_shm_size_get(const apr_shm_t *m);
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/**
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* Get the pool used by this shared memory segment.
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*/
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APR_POOL_DECLARE_ACCESSOR(shm);
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/** @} */
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#ifdef __cplusplus
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}
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#endif
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#endif /* APR_SHM_T */
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