1 /*
   2  * Copyright (c) 1999, 2013, Oracle and/or its affiliates. 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.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package javax.sound.midi;
  27 
  28 
  29 /**
  30  * A <code>MetaMessage</code> is a <code>{@link MidiMessage}</code> that is not meaningful to synthesizers, but
  31  * that can be stored in a MIDI file and interpreted by a sequencer program.
  32  * (See the discussion in the <code>MidiMessage</code>
  33  * class description.)  The Standard MIDI Files specification defines
  34  * various types of meta-events, such as sequence number, lyric, cue point,
  35  * and set tempo.  There are also meta-events
  36  * for such information as lyrics, copyrights, tempo indications, time and key
  37  * signatures, markers, etc.  For more information, see the Standard MIDI Files 1.0
  38  * specification, which is part of the Complete MIDI 1.0 Detailed Specification
  39  * published by the MIDI Manufacturer's Association
  40  * (<a href = http://www.midi.org>http://www.midi.org</a>).
  41  *
  42  * <p>
  43  * When data is being transported using MIDI wire protocol,
  44  * a <code>{@link ShortMessage}</code> with the status value <code>0xFF</code> represents
  45  * a system reset message.  In MIDI files, this same status value denotes a <code>MetaMessage</code>.
  46  * The types of meta-message are distinguished from each other by the first byte
  47  * that follows the status byte <code>0xFF</code>.  The subsequent bytes are data
  48  * bytes.  As with system exclusive messages, there are an arbitrary number of
  49  * data bytes, depending on the type of <code>MetaMessage</code>.
  50  *
  51  * @see MetaEventListener
  52  *
  53  * @author David Rivas
  54  * @author Kara Kytle

  55  */
  56 
  57 public class MetaMessage extends MidiMessage {
  58 
  59 
  60     // Status byte defines
  61 
  62     /**
  63      * Status byte for <code>MetaMessage</code> (0xFF, or 255), which is used
  64      * in MIDI files.  It has the same value as SYSTEM_RESET, which
  65      * is used in the real-time "MIDI wire" protocol.

  66      * @see MidiMessage#getStatus
  67      */
  68     public static final int META                                                = 0xFF; // 255
  69 
  70     // Instance variables
  71 
  72     /**
  73      * The length of the actual message in the data array.
  74      * This is used to determine how many bytes of the data array
  75      * is the message, and how many are the status byte, the
  76      * type byte, and the variable-length-int describing the
  77      * length of the message.
  78      */
  79     private int dataLength = 0;
  80 
  81 
  82     /**
  83      * Constructs a new <code>MetaMessage</code>. The contents of
  84      * the message are not set here; use
  85      * {@link #setMessage(int, byte[], int) setMessage}
  86      * to set them subsequently.
  87      */
  88     public MetaMessage() {
  89         // Default meta message data: just the META status byte value
  90         this(new byte[]{(byte) META, 0});
  91     }
  92 
  93     /**
  94      * Constructs a new {@code MetaMessage} and sets the message parameters.
  95      * The contents of the message can be changed by using
  96      * the {@code setMessage} method.
  97      *
  98      * @param type   meta-message type (must be less than 128)
  99      * @param data   the data bytes in the MIDI message
 100      * @param length an amount of bytes in the {@code data} byte array;
 101      *     it should be non-negative and less than or equal to
 102      *     {@code data.length}
 103      * @throws InvalidMidiDataException if the parameter values do not specify
 104      *     a valid MIDI meta message
 105      * @see #setMessage(int, byte[], int)
 106      * @see #getType()
 107      * @see #getData()
 108      * @since 1.7
 109      */
 110     public MetaMessage(int type, byte[] data, int length)
 111             throws InvalidMidiDataException {
 112         super(null);
 113         setMessage(type, data, length); // can throw InvalidMidiDataException
 114     }
 115 
 116 
 117     /**
 118      * Constructs a new <code>MetaMessage</code>.
 119      * @param data an array of bytes containing the complete message.
 120      * The message data may be changed using the <code>setMessage</code>
 121      * method.
 122      * @see #setMessage
 123      */
 124     protected MetaMessage(byte[] data) {
 125         super(data);
 126         //$$fb 2001-10-06: need to calculate dataLength. Fix for bug #4511796
 127         if (data.length>=3) {
 128             dataLength=data.length-3;
 129             int pos=2;
 130             while (pos<data.length && (data[pos] & 0x80)!=0) {
 131                 dataLength--; pos++;
 132             }
 133         }
 134     }
 135 
 136 
 137     /**
 138      * Sets the message parameters for a <code>MetaMessage</code>.
 139      * Since only one status byte value, <code>0xFF</code>, is allowed for meta-messages,
 140      * it does not need to be specified here.  Calls to <code>{@link MidiMessage#getStatus getStatus}</code> return
 141      * <code>0xFF</code> for all meta-messages.

 142      * <p>
 143      * The <code>type</code> argument should be a valid value for the byte that
 144      * follows the status byte in the <code>MetaMessage</code>.  The <code>data</code> argument
 145      * should contain all the subsequent bytes of the <code>MetaMessage</code>.  In other words,
 146      * the byte that specifies the type of <code>MetaMessage</code> is not considered a data byte.

 147      *
 148      * @param type              meta-message type (must be less than 128)
 149      * @param data              the data bytes in the MIDI message
 150      * @param length    the number of bytes in the <code>data</code>
 151      * byte array
 152      * @throws                  InvalidMidiDataException  if the
 153      * parameter values do not specify a valid MIDI meta message
 154      */
 155     public void setMessage(int type, byte[] data, int length) throws InvalidMidiDataException {
 156 
 157         if (type >= 128 || type < 0) {
 158             throw new InvalidMidiDataException("Invalid meta event with type " + type);
 159         }
 160         if ((length > 0 && length > data.length) || length < 0) {
 161             throw new InvalidMidiDataException("length out of bounds: "+length);
 162         }
 163 
 164         this.length = 2 + getVarIntLength(length) + length;
 165         this.dataLength = length;
 166         this.data = new byte[this.length];
 167         this.data[0] = (byte) META;        // status value for MetaMessages (meta events)
 168         this.data[1] = (byte) type;        // MetaMessage type
 169         writeVarInt(this.data, 2, length); // write the length as a variable int
 170         if (length > 0) {
 171             System.arraycopy(data, 0, this.data, this.length - this.dataLength, this.dataLength);
 172         }
 173     }
 174 
 175 
 176     /**
 177      * Obtains the type of the <code>MetaMessage</code>.
 178      * @return an integer representing the <code>MetaMessage</code> type

 179      */
 180     public int getType() {
 181         if (length>=2) {
 182             return data[1] & 0xFF;
 183         }
 184         return 0;
 185     }
 186 
 187 
 188 
 189     /**
 190      * Obtains a copy of the data for the meta message.  The returned
 191      * array of bytes does not include the status byte or the message
 192      * length data.  The length of the data for the meta message is
 193      * the length of the array.  Note that the length of the entire
 194      * message includes the status byte and the meta message type
 195      * byte, and therefore may be longer than the returned array.
 196      * @return array containing the meta message data.

 197      * @see MidiMessage#getLength
 198      */
 199     public byte[] getData() {
 200         byte[] returnedArray = new byte[dataLength];
 201         System.arraycopy(data, (length - dataLength), returnedArray, 0, dataLength);
 202         return returnedArray;
 203     }
 204 
 205 
 206     /**
 207      * Creates a new object of the same class and with the same contents
 208      * as this object.

 209      * @return a clone of this instance
 210      */
 211     public Object clone() {
 212         byte[] newData = new byte[length];
 213         System.arraycopy(data, 0, newData, 0, newData.length);
 214 
 215         MetaMessage event = new MetaMessage(newData);
 216         return event;
 217     }
 218 
 219     // HELPER METHODS
 220 
 221     private int getVarIntLength(long value) {
 222         int length = 0;
 223         do {
 224             value = value >> 7;
 225             length++;
 226         } while (value > 0);
 227         return length;
 228     }
 229 
 230     private final static long mask = 0x7F;
 231 
 232     private void writeVarInt(byte[] data, int off, long value) {
 233         int shift=63; // number of bitwise left-shifts of mask
 234         // first screen out leading zeros
 235         while ((shift > 0) && ((value & (mask << shift)) == 0)) shift-=7;
 236         // then write actual values
 237         while (shift > 0) {
 238             data[off++]=(byte) (((value & (mask << shift)) >> shift) | 0x80);
 239             shift-=7;
 240         }
 241         data[off] = (byte) (value & mask);
 242     }
 243 
 244 }
--- EOF ---