/*

 * Copyright 1999-2003 Sun Microsystems, Inc.  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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package javax.sound.midi;

import java.io.ByteArrayOutputStream;

import java.io.DataOutputStream;

import java.io.IOException;

/**

 * A <code>MetaMessage</code> is a <code>{@link MidiMessage}</code> that is not meaningful to synthesizers, but

 * that can be stored in a MIDI file and interpreted by a sequencer program.

 * (See the discussion in the <code>MidiMessage</code>

 * class description.)  The Standard MIDI Files specification defines

 * various types of meta-events, such as sequence number, lyric, cue point,

 * and set tempo.  There are also meta-events

 * for such information as lyrics, copyrights, tempo indications, time and key

 * signatures, markers, etc.  For more information, see the Standard MIDI Files 1.0

 * specification, which is part of the Complete MIDI 1.0 Detailed Specification

 * published by the MIDI Manufacturer's Association

 * (<a href = http://www.midi.org>http://www.midi.org</a>).

 *

 * <p>

 * When data is being transported using MIDI wire protocol,

 * a <code>{@link ShortMessage}</code> with the status value <code>0xFF</code> represents

 * a system reset message.  In MIDI files, this same status value denotes a <code>MetaMessage</code>.

 * The types of meta-message are distinguished from each other by the first byte

 * that follows the status byte <code>0xFF</code>.  The subsequent bytes are data

 * bytes.  As with system exclusive messages, there are an arbitrary number of

 * data bytes, depending on the type of <code>MetaMessage</code>.

 *

 * @see MetaEventListener

 *

 * @author David Rivas

 * @author Kara Kytle

 */

public class MetaMessage extends MidiMessage {

    // Status byte defines

    /**

     * Status byte for <code>MetaMessage</code> (0xFF, or 255), which is used

     * in MIDI files.  It has the same value as SYSTEM_RESET, which

     * is used in the real-time "MIDI wire" protocol.

     * @see MidiMessage#getStatus

     */

    public static final int META                                                = 0xFF; // 255

    // Default meta message data: just the META status byte value

    // $$kk: 09.09.99: need a real event here!!

    private static byte[] defaultMessage                                = { (byte)META, 0 };

    // Instance variables

    /**

     * The length of the actual message in the data array.

     * This is used to determine how many bytes of the data array

     * is the message, and how many are the status byte, the

     * type byte, and the variable-length-int describing the

     * length of the message.

     */

    private int dataLength = 0;

    /**

     * Constructs a new <code>MetaMessage</code>. The contents of

     * the message are not set here; use

     * {@link #setMessage(int, byte[], int) setMessage}

     * to set them subsequently.

     */

    public MetaMessage() {

        //super(defaultMessage);

        this(defaultMessage);

    }

    /**

     * Constructs a new <code>MetaMessage</code>.

     * @param data an array of bytes containing the complete message.

     * The message data may be changed using the <code>setMessage</code>

     * method.

     * @see #setMessage

     */

    protected MetaMessage(byte[] data) {

        super(data);

        //$$fb 2001-10-06: need to calculate dataLength. Fix for bug #4511796

        if (data.length>=3) {

            dataLength=data.length-3;

            int pos=2;

            while (pos<data.length && (data[pos] & 0x80)!=0) {

                dataLength--; pos++;

            }

        }

    }

    /**

     * Sets the message parameters for a <code>MetaMessage</code>.

     * Since only one status byte value, <code>0xFF</code>, is allowed for meta-messages,

     * it does not need to be specified here.  Calls to <code>{@link MidiMessage#getStatus getStatus}</code> return

     * <code>0xFF</code> for all meta-messages.

     * <p>

     * The <code>type</code> argument should be a valid value for the byte that

     * follows the status byte in the <code>MetaMessage</code>.  The <code>data</code> argument

     * should contain all the subsequent bytes of the <code>MetaMessage</code>.  In other words,

     * the byte that specifies the type of <code>MetaMessage</code> is not considered a data byte.

     *

     * @param type              meta-message type (must be less than 128)

     * @param data              the data bytes in the MIDI message

     * @param length    the number of bytes in the <code>data</code>

     * byte array

     * @throws                  <code>InvalidMidiDataException</code>  if the

     * parameter values do not specify a valid MIDI meta message

     */

    public void setMessage(int type, byte[] data, int length) throws InvalidMidiDataException {

        if (type >= 128 || type < 0) {

            throw new InvalidMidiDataException("Invalid meta event with type " + type);

        }

        if ((length > 0 && length > data.length) || length < 0) {

            throw new InvalidMidiDataException("length out of bounds: "+length);

        }

        this.length = 2 + getVarIntLength(length) + length;

        this.dataLength = length;

        this.data = new byte[this.length];

        this.data[0] = (byte) META;        // status value for MetaMessages (meta events)

        this.data[1] = (byte) type;        // MetaMessage type

        writeVarInt(this.data, 2, length); // write the length as a variable int

        if (length > 0) {

            System.arraycopy(data, 0, this.data, this.length - this.dataLength, this.dataLength);

        }

    }

    /**

     * Obtains the type of the <code>MetaMessage</code>.

     * @return an integer representing the <code>MetaMessage</code> type

     */

    public int getType() {

        if (length>=2) {

            return data[1] & 0xFF;

        }

        return 0;

    }

    /**

     * Obtains a copy of the data for the meta message.  The returned

     * array of bytes does not include the status byte or the message

     * length data.  The length of the data for the meta message is

     * the length of the array.  Note that the length of the entire

     * message includes the status byte and the meta message type

     * byte, and therefore may be longer than the returned array.

     * @return array containing the meta message data.

     * @see MidiMessage#getLength

     */

    public byte[] getData() {

        byte[] returnedArray = new byte[dataLength];

        System.arraycopy(data, (length - dataLength), returnedArray, 0, dataLength);

        return returnedArray;

    }

    /**

     * Creates a new object of the same class and with the same contents

     * as this object.

     * @return a clone of this instance

     */

    public Object clone() {

        byte[] newData = new byte[length];

        System.arraycopy(data, 0, newData, 0, newData.length);

        MetaMessage event = new MetaMessage(newData);

        return event;

    }

    // HELPER METHODS

    private int getVarIntLength(long value) {

        int length = 0;

        do {

            value = value >> 7;

            length++;

        } while (value > 0);

        return length;

    }

    private final static long mask = 0x7F;

    private void writeVarInt(byte[] data, int off, long value) {

        int shift=63; // number of bitwise left-shifts of mask

        // first screen out leading zeros

        while ((shift > 0) && ((value & (mask << shift)) == 0)) shift-=7;

        // then write actual values

        while (shift > 0) {

            data[off++]=(byte) (((value & (mask << shift)) >> shift) | 0x80);

            shift-=7;

        }

        data[off] = (byte) (value & mask);

    }

}