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    */
MetaMessage()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    */
MetaMessage(byte[] data)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    */
setMessage(int type, byte[] data, int length)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    */
getType()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    */
getData()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    */
clone()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 }
177