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java/org/apache/tomcat/jni/Shm.java

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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.
+     * @throws Error An error occurred
+     */
+    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
+     * @return the operation status
+     */
+    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.
+     * @return the operation status
+     */
+    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.
+     * @throws Error An error occurred
+     */
+    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.
+     * @return the operation status
+     */
+    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.
+     * @return the length of the segment
+     */
+    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);
+
+}