SysexMessage


1   /*
2    * @(#)SysexMessage.java    1.26 03/12/19
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package javax.sound.midi;
9   
10  /**
11   * A <code>SysexMessage</code> object represents a MIDI system exclusive message.
12   * <p>
13   * When a system exclusive message is read from a MIDI file, it always has
14   * a defined length.  Data from a system exclusive message from a MIDI file
15   * should be stored in the data array of a <code>SysexMessage</code> as
16   * follows: the system exclusive message status byte (0xF0 or 0xF7), all
17   * message data bytes, and finally the end-of-exclusive flag (0xF7).
18   * The length reported by the <code>SysexMessage</code> object is therefore
19   * the length of the system exclusive data plus two: one byte for the status
20   * byte and one for the end-of-exclusive flag.
21   * <p>
22   * As dictated by the Standard MIDI Files specification, two status byte values are legal
23   * for a <code>SysexMessage</code> read from a MIDI file:
24   * <ul>
25   * <li>0xF0: System Exclusive message (same as in MIDI wire protocol)</li>
26   * <li>0xF7: Special System Exclusive message</li>
27   * </ul>
28   * <p>
29   * When Java Sound is used to handle system exclusive data that is being received
30   * using MIDI wire protocol, it should place the data in one or more
31   * <code>SysexMessages</code>.  In this case, the length of the system exclusive data
32   * is not known in advance; the end of the system exclusive data is marked by an
33   * end-of-exclusive flag (0xF7) in the MIDI wire byte stream.
34   * <ul>
35   * <li>0xF0: System Exclusive message (same as in MIDI wire protocol)</li>
36   * <li>0xF7: End of Exclusive (EOX)</li>
37   * </ul>
38   * The first <code>SysexMessage</code> object containing data for a particular system
39   * exclusive message should have the status value 0xF0.  If this message contains all
40   * the system exclusive data
41   * for the message, it should end with the status byte 0xF7 (EOX).
42   * Otherwise, additional system exclusive data should be sent in one or more
43   * <code>SysexMessages</code> with a status value of 0xF7.  The <code>SysexMessage</code>
44   * containing the last of the data for the system exclusive message should end with the
45   * value 0xF7 (EOX) to mark the end of the system exclusive message.
46   * <p>
47   * If system exclusive data from <code>SysexMessages</code> objects is being transmitted
48   * using MIDI wire protocol, only the initial 0xF0 status byte, the system exclusive
49   * data itself, and the final 0xF7 (EOX) byte should be propagated; any 0xF7 status
50   * bytes used to indicate that a <code>SysexMessage</code> contains continuing system
51   * exclusive data should not be propagated via MIDI wire protocol.
52   *
53   * @version 1.26, 03/12/19
54   * @author David Rivas
55   * @author Kara Kytle
56   * @author Florian Bomers
57   */
58  public class SysexMessage extends MidiMessage   {
59  
60  
61      // Status byte defines
62  
63  
64      /**
65       * Status byte for System Exclusive message (0xF0, or 240).
66       * @see MidiMessage#getStatus
67       */
68      public static final int SYSTEM_EXCLUSIVE            = 0xF0; // 240
69  
70  
71      /**
72       * Status byte for Special System Exclusive message (0xF7, or 247), which is used
73       * in MIDI files.  It has the same value as END_OF_EXCLUSIVE, which
74       * is used in the real-time "MIDI wire" protocol.
75       * @see MidiMessage#getStatus
76       */
77      public static final int SPECIAL_SYSTEM_EXCLUSIVE    = 0xF7; // 247
78  
79  
80      // Instance variables
81  
82  
83      /*
84       * The data bytes for this system exclusive message.  These are
85       * initialized to <code>null</code> and are set explicitly
86       * by {@link #setMessage(int, byte[], int, long) setMessage}.
87       */
88      //protected byte[] data = null;
89  
90  
91      /**
92       * Constructs a new <code>SysexMessage</code>. The
93       * contents of the new message are guaranteed to specify
94       * a valid MIDI message.  Subsequently, you may set the
95       * contents of the message using one of the <code>setMessage</code>
96       * methods.
97       * @see #setMessage
98       */
99      public SysexMessage() {
100     this(new byte[2]);
101     // Default sysex message data: SOX followed by EOX
102     data[0] = (byte) (SYSTEM_EXCLUSIVE & 0xFF);
103     data[1] = (byte) (ShortMessage.END_OF_EXCLUSIVE & 0xFF);
104     }
105 
106 
107     /**
108      * Constructs a new <code>SysexMessage</code>.
109      * @param data an array of bytes containing the complete message.
110      * The message data may be changed using the <code>setMessage</code>
111      * method.
112      * @see #setMessage
113      */
114     protected SysexMessage(byte[] data) {
115     super(data);
116     }
117 
118 
119     /**
120      * Sets the data for the system exclusive message.   The
121      * first byte of the data array must be a valid system
122      * exclusive status byte (0xF0 or 0xF7).
123      * @param data the system exclusive message data
124      * @param length the length of the valid message data in
125      * the array, including the status byte.
126      */
127     public void setMessage(byte[] data, int length) throws InvalidMidiDataException   {
128     int status = (data[0] & 0xFF);
129     if ((status != 0xF0) && (status != 0xF7)) {
130         throw new InvalidMidiDataException  ("Invalid status byte for sysex message: 0x" + Integer.toHexString(status));
131     }
132     super.setMessage(data, length);
133     }
134 
135 
136     /**
137      * Sets the data for the system exclusive message.
138      * @param status the status byte for the message (0xF0 or 0xF7)
139      * @param data the system exclusive message data
140      * @param length the length of the valid message data in
141      * the array
142      */
143     public void setMessage(int status, byte[] data, int length) throws InvalidMidiDataException   {
144     if ( (status != 0xF0) && (status != 0xF7) ) {
145         throw new InvalidMidiDataException  ("Invalid status byte for sysex message: 0x" + Integer.toHexString(status));
146     }
147     if (length < 0 || length > data.length) {
148         throw new IndexOutOfBoundsException  ("length out of bounds: "+length);
149     }
150     this.length = length + 1;
151 
152     if (this.data==null || this.data.length < this.length) {
153         this.data = new byte[this.length];
154     }
155 
156     this.data[0] = (byte) (status & 0xFF);
157     if (length > 0) {
158         System.arraycopy(data, 0, this.data, 1, length);
159     }
160     }
161 
162 
163     /**
164      * Obtains a copy of the data for the system exclusive message.
165      * The returned array of bytes does not include the status byte.
166      * @return array containing the system exclusive message data.
167      */
168     public byte[] getData() {
169     byte[] returnedArray = new byte[length - 1];
170     System.arraycopy(data, 1, returnedArray, 0, (length - 1));
171     return returnedArray;
172     }
173 
174 
175     /**
176      * Creates a new object of the same class and with the same contents
177      * as this object.
178      * @return a clone of this instance
179      */
180     public Object   clone() {
181     byte[] newData = new byte[length];
182     System.arraycopy(data, 0, newData, 0, newData.length);
183     SysexMessage   event = new SysexMessage  (newData);
184     return event;
185     }
186 }
187
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags