/*

 * Copyright (c) 1998, 2017, 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 java.io.IOException;

public class Packet extends Object {

    public final static short NoFlags = 0x0;

    public final static short Reply = 0x80;

    public final static short ReplyNoError = 0x0;

    static int uID = 1;

    final static byte[] nullData = new byte[0];

    // Note! flags, cmdSet, and cmd are all byte values.

    // We represent them as shorts to make them easier

    // to work with.

    int id;

    short flags;

    short cmdSet;

    short cmd;

    short errorCode;

    byte[] data;

    volatile boolean replied = false;

    /**

     * Return byte representation of the packet

     */

    public byte[] toByteArray() {

        int len = data.length + 11;

        byte b[] = new byte[len];

        b[0] = (byte)((len >>> 24) & 0xff);

        b[1] = (byte)((len >>> 16) & 0xff);

        b[2] = (byte)((len >>>  8) & 0xff);

        b[3] = (byte)((len >>>  0) & 0xff);

        b[4] = (byte)((id >>> 24) & 0xff);

        b[5] = (byte)((id >>> 16) & 0xff);

        b[6] = (byte)((id >>>  8) & 0xff);

        b[7] = (byte)((id >>>  0) & 0xff);

        b[8] = (byte)flags;

        if ((flags & Packet.Reply) == 0) {

            b[9] = (byte)cmdSet;

            b[10] = (byte)cmd;

        } else {

            b[9] = (byte)((errorCode >>>  8) & 0xff);

            b[10] = (byte)((errorCode >>>  0) & 0xff);

        }

        if (data.length > 0) {

            System.arraycopy(data, 0, b, 11, data.length);

        }

        return b;

    }

    /**

     * Create a packet from its byte array representation

     */

    public static Packet fromByteArray(byte b[]) throws IOException {

        if (b.length < 11) {

            throw new IOException("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 != b.length) {

            throw new IOException("length size mis-match");

        }

        int b4 = b[4] & 0xff;

        int b5 = b[5] & 0xff;

        int b6 = b[6] & 0xff;

        int b7 = b[7] & 0xff;

        Packet p = new Packet();

        p.id = ((b4 << 24) | (b5 << 16) | (b6 << 8) | (b7 << 0));

        p.flags = (short)(b[8] & 0xff);

        if ((p.flags & Packet.Reply) == 0) {

            p.cmdSet = (short)(b[9] & 0xff);

            p.cmd = (short)(b[10] & 0xff);

        } else {

            short b9 = (short)(b[9] & 0xff);

            short b10 = (short)(b[10] & 0xff);

            p.errorCode = (short)((b9 << 8) + (b10 << 0));

        }

        p.data = new byte[b.length - 11];

        System.arraycopy(b, 11, p.data, 0, p.data.length);

        return p;

    }

    Packet() {

        id = uniqID();

        flags = NoFlags;

        data = nullData;

    }

    static synchronized private int uniqID() {

        /*

         * JDWP spec does not require this id to be sequential and

         * increasing, but our implementation does. See

         * VirtualMachine.notifySuspend, for example.

         */

        return uID++;

    }

}