SharedMemoryConnection.java

/*
 * Copyright (c) 1999, 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package com.sun.tools.jdi;

import com.sun.jdi.*;
import com.sun.jdi.connect.*;
import com.sun.jdi.connect.spi.*;

import java.io.IOException;

class SharedMemoryConnection extends Connection {
    private long id;
    private Object receiveLock = new Object();
    private Object sendLock = new Object();
    private Object closeLock = new Object();
    private boolean closed = false;

    private native byte receiveByte0(long id) throws IOException;
    private native void sendByte0(long id, byte b) throws IOException;
    private native void close0(long id);
    private native byte[] receivePacket0(long id)throws IOException;
    private native void sendPacket0(long id, byte b[]) throws IOException;

    // handshake with the target VM
    void handshake(long handshakeTimeout) throws IOException {
        byte[] hello = "JDWP-Handshake".getBytes("UTF-8");

        for (int i=0; i<hello.length; i++) {
            sendByte0(id, hello[i]);
        }
        for (int i=0; i<hello.length; i++) {
            byte b = receiveByte0(id);
            if (b != hello[i]) {
                throw new IOException("handshake failed - unrecognized message from target VM");
            }
        }
    }


    SharedMemoryConnection(long id) throws IOException {
        this.id = id;
    }

    public void close() {
        synchronized (closeLock) {
            if (!closed) {
                close0(id);
                closed = true;
            }
        }
    }

    public boolean isOpen() {
        synchronized (closeLock) {
            return !closed;
        }
    }

    public byte[] readPacket() throws IOException {
        if (!isOpen()) {
            throw new ClosedConnectionException("Connection closed");
        }
        byte b[];
        try {
            // only one thread may be reading at a time
            synchronized (receiveLock) {
                b  = receivePacket0(id);
            }
        } catch (IOException ioe) {
            if (!isOpen()) {
                throw new ClosedConnectionException("Connection closed");
            } else {
                throw ioe;
            }
        }
        return b;
    }

    public void writePacket(byte b[]) throws IOException {
        if (!isOpen()) {
            throw new ClosedConnectionException("Connection closed");
        }

        /*
         * Check the packet size
         */
        if (b.length < 11) {
            throw new IllegalArgumentException("packet is insufficient size");
        }
        int b0 = b[0] & 0xff;
        int b1 = b[1] & 0xff;
        int b2 = b[2] & 0xff;
        int b3 = b[3] & 0xff;
        int len = ((b0 << 24) | (b1 << 16) | (b2 << 8) | (b3 << 0));
        if (len < 11) {
            throw new IllegalArgumentException("packet is insufficient size");
        }

        /*
         * Check that the byte array contains the complete packet
         */
        if (len > b.length) {
            throw new IllegalArgumentException("length mis-match");
        }

        try {
            // only one thread may be writing at a time
            synchronized(sendLock) {
                sendPacket0(id, b);
            }
        } catch (IOException ioe) {
            if (!isOpen()) {
               throw new ClosedConnectionException("Connection closed");
            } else {
               throw ioe;
            }
        }
    }
}