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  /*
   *  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.
  */
 
 package org.apache.tomcat.jni;
 
Shm

Author(s):
Mladen Turk
Version:
$Revision: 515 $, $Date: 2008-03-17 22:02:23 +0100 (Mon, 17 Mar 2008) $
 
 
 public class Shm {

    
Create and make accessable a shared memory segment.
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.
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.

Parameters:
reqsize The desired size of the segment.
filename The file to use for shared memory on platforms that require it.
pool the pool from which to allocate the shared memory structure.
Returns:
The created shared memory structure.
 
     public static native long create(long reqsizeString filenamelong pool)
         throws Error;

    
Remove shared memory segment associated with a filename.
This function is only supported on platforms which support name-based shared memory segments, and will return APR_ENOTIMPL on platforms without such support.

Parameters:
filename The filename associated with shared-memory segment which needs to be removed
pool The pool used for file operations
 
     public static native int remove(String filenamelong pool);

    
Destroy a shared memory segment and associated memory.

Parameters:
m The shared memory segment structure to destroy.
 
     public static native int destroy(long m);

    
Attach to a shared memory segment that was created by another process.

Parameters:
filename The file used to create the original segment. (This MUST match the original filename.)
pool the pool from which to allocate the shared memory structure for this process.
Returns:
The created shared memory structure.
 
     public static native long attach(String filenamelong pool)
         throws Error;

    
Detach from a shared memory segment without destroying it.

Parameters:
m The shared memory structure representing the segment to detach from.
 
     public static native int detach(long 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.

Parameters:
m The shared memory segment from which to retrieve the base address.
Returns:
address, aligned by APR_ALIGN_DEFAULT.
    public static native long baseaddr(long m);

    
Retrieve the length of a shared memory segment in bytes.

Parameters:
m The shared memory segment from which to retrieve the segment length.
    public static native long size(long m);

    
Retrieve new ByteBuffer 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.

Parameters:
m The shared memory segment from which to retrieve the base address.
Returns:
address, aligned by APR_ALIGN_DEFAULT.
    public static native ByteBuffer buffer(long m);
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