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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;
import java.nio.ByteBuffer;
/** Shm
*
* @author Mladen Turk
*/
public class Shm {
/**
* Create and make accessible a shared memory segment.
* <br />
* A note about Anonymous vs. Named shared memory segments:<br />
* Not all platforms support anonymous shared memory segments, but in
* some cases it is preferred 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.
* <br />
* A note about allocation sizes:<br />
* 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.
* @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.
* @return The created shared memory structure.
*
*/
public static native long create(long reqsize, String filename, long pool)
throws Error;
/**
* Remove shared memory segment associated with a filename.
* <br />
* This function is only supported on platforms which support
* name-based shared memory segments, and will return APR_ENOTIMPL on
* platforms without such support.
* @param filename The filename associated with shared-memory segment which
* needs to be removed
* @param pool The pool used for file operations
*/
public static native int remove(String filename, long pool);
/**
* Destroy a shared memory segment and associated memory.
* @param 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.
* @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.
* @return The created shared memory structure.
*/
public static native long attach(String filename, long pool)
throws Error;
/**
* Detach from a shared memory segment without destroying it.
* @param 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.
* @param m The shared memory segment from which to retrieve
* the base address.
* @return address, aligned by APR_ALIGN_DEFAULT.
*/
public static native long baseaddr(long m);
/**
* Retrieve the length of a shared memory segment in bytes.
* @param 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.
* @param m The shared memory segment from which to retrieve
* the base address.
* @return address, aligned by APR_ALIGN_DEFAULT.
*/
public static native ByteBuffer buffer(long m);
}
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