old-autovect-branch/libjava/classpath/javax/sound/midi/MetaMessage.java

   1 /* MetaMessage.java -- A meta message for MIDI files.
   2    Copyright (C) 2005 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package javax.sound.midi;
  40
  41 /**
  42  * A system exclusive MIDI message.
  43  *
  44  * @author Anthony Green (green@redhat.com)
  45  * @since 1.3
  46  *
  47  */
  48 public class MetaMessage extends MidiMessage
  49 {
  50   /**
  51    * The META status code.  Only valid for MIDI files, not the wire protocol.
  52    */
  53   public static final int META = 0xFF;
  54
  55   // The length of the variable length data length encoding.
  56   private int lengthLength = 0;
  57
  58   /**
  59    * Create a default valid meta message.
  60    *
  61    * The official specs don't specify what message is to be
  62    * created.  For now, we create a zero length meta message
  63    * with a type code of 0.
  64    */
  65   public MetaMessage()
  66   {
  67     super(new byte[4]);
  68     data[0] = (byte) META;
  69     data[1] = (byte) 0; // Type
  70     data[2] = (byte) 1; // Length length
  71     data[3] = (byte) 0; // Length
  72     lengthLength = 1;
  73   }
  74
  75   /**
  76    * Create a MetaMessage object.
  77    * @param data a complete system exclusive message
  78    */
  79   public MetaMessage(byte[] data)
  80   {
  81     super(data);
  82     int index = 2;
  83     lengthLength = 1;
  84     while ((data[index++] & 0x80) > 0)
  85       lengthLength++;
  86   }
  87
  88   /**
  89    * Set the meta message.
  90    *
  91    * @param type the meta type byte (< 128)
  92    * @param data the message data
  93    * @param length the length of the message data
  94    * @throws InvalidMidiDataException if this message is invalid
  95    */
  96   public void setMessage(int type, byte[] data, int length)
  97     throws InvalidMidiDataException
  98   {
  99     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 }