1 /*
2 * Copyright 1999-2003 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package javax.sound.midi;
27
28 import java.io.ByteArrayOutputStream;
29 import java.io.DataOutputStream;
30 import java.io.IOException;
31
32
33 /**
34 * A <code>MetaMessage</code> is a <code>{@link MidiMessage}</code> that is not meaningful to synthesizers, but
35 * that can be stored in a MIDI file and interpreted by a sequencer program.
36 * (See the discussion in the <code>MidiMessage</code>
37 * class description.) The Standard MIDI Files specification defines
38 * various types of meta-events, such as sequence number, lyric, cue point,
39 * and set tempo. There are also meta-events
40 * for such information as lyrics, copyrights, tempo indications, time and key
41 * signatures, markers, etc. For more information, see the Standard MIDI Files 1.0
42 * specification, which is part of the Complete MIDI 1.0 Detailed Specification
43 * published by the MIDI Manufacturer's Association
44 * (<a href = http://www.midi.org>http://www.midi.org</a>).
45 *
46 * <p>
47 * When data is being transported using MIDI wire protocol,
48 * a <code>{@link ShortMessage}</code> with the status value <code>0xFF</code> represents
49 * a system reset message. In MIDI files, this same status value denotes a <code>MetaMessage</code>.
50 * The types of meta-message are distinguished from each other by the first byte
51 * that follows the status byte <code>0xFF</code>. The subsequent bytes are data
52 * bytes. As with system exclusive messages, there are an arbitrary number of
53 * data bytes, depending on the type of <code>MetaMessage</code>.
54 *
55 * @see MetaEventListener
56 *
57 * @author David Rivas
58 * @author Kara Kytle
59 */
60
61 public class MetaMessage extends MidiMessage {
62
63
64 // Status byte defines
65
66 /**
67 * Status byte for <code>MetaMessage</code> (0xFF, or 255), which is used
68 * in MIDI files. It has the same value as SYSTEM_RESET, which
69 * is used in the real-time "MIDI wire" protocol.
70 * @see MidiMessage#getStatus
71 */
72 public static final int META = 0xFF; // 255
73
74
75 // Default meta message data: just the META status byte value
76 // $$kk: 09.09.99: need a real event here!!
77
78 private static byte[] defaultMessage = { (byte)META, 0 };
79
80
81
82 // Instance variables
83
84 /**
85 * The length of the actual message in the data array.
86 * This is used to determine how many bytes of the data array
87 * is the message, and how many are the status byte, the
88 * type byte, and the variable-length-int describing the
89 * length of the message.
90 */
91 private int dataLength = 0;
92
93
94 /**
95 * Constructs a new <code>MetaMessage</code>. The contents of
96 * the message are not set here; use
97 * {@link #setMessage(int, byte[], int) setMessage}
98 * to set them subsequently.
99 */
100 public MetaMessage() {
101 //super(defaultMessage);
102 this(defaultMessage);
103 }
104
105
106 /**
107 * Constructs a new <code>MetaMessage</code>.
108 * @param data an array of bytes containing the complete message.
109 * The message data may be changed using the <code>setMessage</code>
110 * method.
111 * @see #setMessage
112 */
113 protected MetaMessage(byte[] data) {
114 super(data);
115 //$$fb 2001-10-06: need to calculate dataLength. Fix for bug #4511796
116 if (data.length>=3) {
117 dataLength=data.length-3;
118 int pos=2;
119 while (pos<data.length && (data[pos] & 0x80)!=0) {
120 dataLength--; pos++;
121 }
122 }
123 }
124
125
126 /**
127 * Sets the message parameters for a <code>MetaMessage</code>.
128 * Since only one status byte value, <code>0xFF</code>, is allowed for meta-messages,
129 * it does not need to be specified here. Calls to <code>{@link MidiMessage#getStatus getStatus}</code> return
130 * <code>0xFF</code> for all meta-messages.
131 * <p>
132 * The <code>type</code> argument should be a valid value for the byte that
133 * follows the status byte in the <code>MetaMessage</code>. The <code>data</code> argument
134 * should contain all the subsequent bytes of the <code>MetaMessage</code>. In other words,
135 * the byte that specifies the type of <code>MetaMessage</code> is not considered a data byte.
136 *
137 * @param type meta-message type (must be less than 128)
138 * @param data the data bytes in the MIDI message
139 * @param length the number of bytes in the <code>data</code>
140 * byte array
141 * @throws <code>InvalidMidiDataException</code> if the
142 * parameter values do not specify a valid MIDI meta message
143 */
144 public void setMessage(int type, byte[] data, int length) throws InvalidMidiDataException {
145
146 if (type >= 128 || type < 0) {
147 throw new InvalidMidiDataException("Invalid meta event with type " + type);
148 }
149 if ((length > 0 && length > data.length) || length < 0) {
150 throw new InvalidMidiDataException("length out of bounds: "+length);
151 }
152
153 this.length = 2 + getVarIntLength(length) + length;
154 this.dataLength = length;
155 this.data = new byte[this.length];
156 this.data[0] = (byte) META; // status value for MetaMessages (meta events)
157 this.data[1] = (byte) type; // MetaMessage type
158 writeVarInt(this.data, 2, length); // write the length as a variable int
159 if (length > 0) {
160 System.arraycopy(data, 0, this.data, this.length - this.dataLength, this.dataLength);
161 }
162 }
163
164
165 /**
166 * Obtains the type of the <code>MetaMessage</code>.
167 * @return an integer representing the <code>MetaMessage</code> type
168 */
169 public int getType() {
170 if (length>=2) {
171 return data[1] & 0xFF;
172 }
173 return 0;
174 }
175
176
177
178 /**
179 * Obtains a copy of the data for the meta message. The returned
180 * array of bytes does not include the status byte or the message
181 * length data. The length of the data for the meta message is
182 * the length of the array. Note that the length of the entire
183 * message includes the status byte and the meta message type
184 * byte, and therefore may be longer than the returned array.
185 * @return array containing the meta message data.
186 * @see MidiMessage#getLength
187 */
188 public byte[] getData() {
189 byte[] returnedArray = new byte[dataLength];
190 System.arraycopy(data, (length - dataLength), returnedArray, 0, dataLength);
191 return returnedArray;
192 }
193
194
195 /**
196 * Creates a new object of the same class and with the same contents
197 * as this object.
198 * @return a clone of this instance
199 */
200 public Object clone() {
201 byte[] newData = new byte[length];
202 System.arraycopy(data, 0, newData, 0, newData.length);
203
204 MetaMessage event = new MetaMessage(newData);
205 return event;
206 }
207
208 // HELPER METHODS
209
210 private int getVarIntLength(long value) {
211 int length = 0;
212 do {
213 value = value >> 7;
214 length++;
215 } while (value > 0);
216 return length;
217 }
218
219 private final static long mask = 0x7F;
220
221 private void writeVarInt(byte[] data, int off, long value) {
222 int shift=63; // number of bitwise left-shifts of mask
223 // first screen out leading zeros
224 while ((shift > 0) && ((value & (mask << shift)) == 0)) shift-=7;
225 // then write actual values
226 while (shift > 0) {
227 data[off++]=(byte) (((value & (mask << shift)) >> shift) | 0x80);
228 shift-=7;
229 }
230 data[off] = (byte) (value & mask);
231 }
232
233 }
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