001/* MetaMessage.java -- A meta message for MIDI files.
002   Copyright (C) 2005 Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package javax.sound.midi;
040
041/**
042 * A system exclusive MIDI message.
043 * 
044 * @author Anthony Green (green@redhat.com)
045 * @since 1.3
046 *
047 */
048public class MetaMessage extends MidiMessage
049{
050  /**
051   * The META status code.  Only valid for MIDI files, not the wire protocol.
052   */
053  public static final int META = 0xFF;
054  
055  // The length of the variable length data length encoding.
056  private int lengthLength = 0;
057  
058  /**
059   * Create a default valid meta message.
060   * 
061   * The official specs don't specify what message is to be
062   * created.  For now, we create a zero length meta message 
063   * with a type code of 0.
064   */
065  public MetaMessage()
066  {
067    super(new byte[4]);
068    data[0] = (byte) META;
069    data[1] = (byte) 0; // Type
070    data[2] = (byte) 1; // Length length
071    data[3] = (byte) 0; // Length
072    lengthLength = 1;
073  }
074  
075  /**
076   * Create a MetaMessage object.
077   * @param data a complete system exclusive message
078   */
079  protected MetaMessage(byte[] data)
080  {
081    super(data);
082    int index = 2;
083    lengthLength = 1;
084    while ((data[index++] & 0x80) > 0)
085      lengthLength++;
086  }
087  
088  /**
089   * Set the meta message.
090   *  
091   * @param type the meta type byte (< 128)
092   * @param data the message data
093   * @param length the length of the message data
094   * @throws InvalidMidiDataException if this message is invalid
095   */
096  public void setMessage(int type, byte[] data, int length)
097    throws InvalidMidiDataException
098  {
099    if (type > 127)
100      throw new InvalidMidiDataException("Meta type 0x"
101                                         + Integer.toHexString(type)
102                                         + " must be less than 128");
103
104    // For a nice description of how variable length values are handled, 
105    // see http://www.borg.com/~jglatt/tech/midifile.htm
106    
107    // First compute the length of the length value
108    lengthLength = 0;
109    int lengthValue = length;
110    do {
111      lengthValue = lengthValue >> 7;
112      lengthLength++;
113    } while (lengthValue > 0);
114    
115    // Now allocate our data array
116    this.length = 2 + lengthLength + length;
117    this.data = new byte[this.length];
118    this.data[0] = (byte) META;
119    this.data[1] = (byte) type;
120    
121    // Now compute the length representation
122    long buffer = length & 0x7F;
123    while ((length >>= 7) > 0)
124    {
125      buffer <<= 8;
126      buffer |= ((length & 0x7F) | 0x80);
127    }
128    
129    // Now store the variable length length value
130    int index = 2;
131    do
132    {
133      this.data[index++] = (byte) (buffer & 0xFF);
134      if ((buffer & 0x80) == 0)
135        break;
136      buffer >>= 8;
137    } while (true);
138 
139    // Now copy the real data.
140    System.arraycopy(data, 0, this.data, index, length);
141  }
142  
143  /**
144   * Get the meta message type.
145   * 
146   * @return the meta message type
147   */
148  public int getType()
149  {
150    return data[1];
151  }
152  
153  /**
154   * Get the data for this message, not including the status,
155   * type, or length information.
156   * 
157   * @return the message data, not including status, type or lenght info
158   */
159  public byte[] getData()
160  {
161    int dataLength = length - 2 - lengthLength;
162    byte[] result = new byte[dataLength];
163    System.arraycopy(data, 2 + lengthLength, result, 0, dataLength);
164    return result;
165  }
166  
167  /* Create a deep-copy clone of this object.
168   * @see java.lang.Object#clone()
169   */
170  public Object clone()
171  {
172    byte message[] = new byte[length];
173    System.arraycopy(data, 0, message, 0, length);
174    return new MetaMessage(message); 
175  }
176}