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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.
     * 
* A note about Anonymous vs. Named shared memory segments:
* 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. *
* 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. * @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. *
* 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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