001    /* MetaMessage.java -- A meta message for MIDI files.
002       Copyright (C) 2005 Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    
039    package 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     */
048    public 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    }