1 /*
   2  * Copyright (c) 1999, 2014, 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
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  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  * A {@code MetaMessage} is a {@link MidiMessage} that is not meaningful to
  30  * synthesizers, but that can be stored in a MIDI file and interpreted by a
  31  * sequencer program. (See the discussion in the {@code MidiMessage} class
  32  * description.) The Standard MIDI Files specification defines various types of
  33  * meta-events, such as sequence number, lyric, cue point, and set tempo. There
  34  * are also meta-events for such information as lyrics, copyrights, tempo
  35  * indications, time and key signatures, markers, etc. For more information, see
  36  * the Standard MIDI Files 1.0 specification, which is part of the Complete MIDI
  37  * 1.0 Detailed Specification published by the MIDI Manufacturer's Association

  38  * (<a href = http://www.midi.org>http://www.midi.org</a>).

  39  * <p>
  40  * When data is being transported using MIDI wire protocol, a
  41  * {@link ShortMessage} with the status value {@code 0xFF} represents a system
  42  * reset message. In MIDI files, this same status value denotes a
  43  * {@code MetaMessage}. The types of meta-message are distinguished from each
  44  * other by the first byte that follows the status byte {@code 0xFF}. The
  45  * subsequent bytes are data bytes. As with system exclusive messages, there are
  46  * an arbitrary number of data bytes, depending on the type of
  47  * {@code MetaMessage}.

  48  *
  49  * @author David Rivas
  50  * @author Kara Kytle
  51  * @see MetaEventListener
  52  */

  53 public class MetaMessage extends MidiMessage {
  54 



  55     /**
  56      * Status byte for {@code MetaMessage} (0xFF, or 255), which is used in MIDI
  57      * files. It has the same value as SYSTEM_RESET, which is used in the
  58      * real-time "MIDI wire" protocol.
  59      *
  60      * @see MidiMessage#getStatus
  61      */
  62     public static final int META                                                = 0xFF; // 255
  63 


  64     /**
  65      * The length of the actual message in the data array. This is used to
  66      * determine how many bytes of the data array is the message, and how many
  67      * are the status byte, the type byte, and the variable-length-int
  68      * describing the length of the message.

  69      */
  70     private int dataLength = 0;
  71 

  72     /**
  73      * Constructs a new {@code MetaMessage}. The contents of the message are not
  74      * set here; use {@link #setMessage(int, byte[], int) setMessage} to set
  75      * them subsequently.

  76      */
  77     public MetaMessage() {
  78         // Default meta message data: just the META status byte value
  79         this(new byte[]{(byte) META, 0});
  80     }
  81 
  82     /**
  83      * Constructs a new {@code MetaMessage} and sets the message parameters. The
  84      * contents of the message can be changed by using the {@code setMessage}
  85      * method.
  86      *
  87      * @param  type meta-message type (must be less than 128)
  88      * @param  data the data bytes in the MIDI message
  89      * @param  length an amount of bytes in the {@code data} byte array; it
  90      *         should be non-negative and less than or equal to
  91      *         {@code data.length}
  92      * @throws InvalidMidiDataException if the parameter values do not specify a
  93      *         valid MIDI meta message
  94      * @see #setMessage(int, byte[], int)
  95      * @see #getType()
  96      * @see #getData()
  97      * @since 1.7
  98      */
  99     public MetaMessage(int type, byte[] data, int length)
 100             throws InvalidMidiDataException {
 101         super(null);
 102         setMessage(type, data, length); // can throw InvalidMidiDataException
 103     }
 104 

 105     /**
 106      * Constructs a new {@code MetaMessage}.
 107      *
 108      * @param  data an array of bytes containing the complete message. The
 109      *         message data may be changed using the {@code setMessage} method.
 110      * @see #setMessage
 111      */
 112     protected MetaMessage(byte[] data) {
 113         super(data);
 114         //$$fb 2001-10-06: need to calculate dataLength. Fix for bug #4511796
 115         if (data.length>=3) {
 116             dataLength=data.length-3;
 117             int pos=2;
 118             while (pos<data.length && (data[pos] & 0x80)!=0) {
 119                 dataLength--; pos++;
 120             }
 121         }
 122     }
 123 

 124     /**
 125      * Sets the message parameters for a {@code MetaMessage}. Since only one
 126      * status byte value, {@code 0xFF}, is allowed for meta-messages, it does
 127      * not need to be specified here. Calls to
 128      * {@link MidiMessage#getStatus getStatus} return {@code 0xFF} for all
 129      * meta-messages.
 130      * <p>
 131      * The {@code type} argument should be a valid value for the byte that
 132      * follows the status byte in the {@code MetaMessage}. The {@code data}
 133      * argument should contain all the subsequent bytes of the
 134      * {@code MetaMessage}. In other words, the byte that specifies the type of
 135      * {@code MetaMessage} 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} byte array
 140      * @throws InvalidMidiDataException if the parameter values do not specify a
 141      *         valid MIDI meta message

 142      */
 143     public void setMessage(int type, byte[] data, int length) throws InvalidMidiDataException {
 144 
 145         if (type >= 128 || type < 0) {
 146             throw new InvalidMidiDataException("Invalid meta event with type " + type);
 147         }
 148         if ((length > 0 && length > data.length) || length < 0) {
 149             throw new InvalidMidiDataException("length out of bounds: "+length);
 150         }
 151 
 152         this.length = 2 + getVarIntLength(length) + length;
 153         this.dataLength = length;
 154         this.data = new byte[this.length];
 155         this.data[0] = (byte) META;        // status value for MetaMessages (meta events)
 156         this.data[1] = (byte) type;        // MetaMessage type
 157         writeVarInt(this.data, 2, length); // write the length as a variable int
 158         if (length > 0) {
 159             System.arraycopy(data, 0, this.data, this.length - this.dataLength, this.dataLength);
 160         }
 161     }
 162 

 163     /**
 164      * Obtains the type of the {@code MetaMessage}.
 165      *
 166      * @return an integer representing the {@code MetaMessage} type
 167      */
 168     public int getType() {
 169         if (length>=2) {
 170             return data[1] & 0xFF;
 171         }
 172         return 0;
 173     }
 174 


 175     /**
 176      * Obtains a copy of the data for the meta message. The returned array of
 177      * bytes does not include the status byte or the message length data. The
 178      * length of the data for the meta message is the length of the array. Note
 179      * that the length of the entire message includes the status byte and the
 180      * meta message type byte, and therefore may be longer than the returned
 181      * array.
 182      *
 183      * @return array containing the meta message data
 184      * @see MidiMessage#getLength
 185      */
 186     public byte[] getData() {
 187         byte[] returnedArray = new byte[dataLength];
 188         System.arraycopy(data, (length - dataLength), returnedArray, 0, dataLength);
 189         return returnedArray;
 190     }
 191 

 192     /**
 193      * Creates a new object of the same class and with the same contents as this
 194      * object.
 195      *
 196      * @return a clone of this instance
 197      */
 198     public Object clone() {
 199         byte[] newData = new byte[length];
 200         System.arraycopy(data, 0, newData, 0, newData.length);
 201 
 202         MetaMessage event = new MetaMessage(newData);
 203         return event;
 204     }
 205 
 206     // HELPER METHODS
 207 
 208     private int getVarIntLength(long value) {
 209         int length = 0;
 210         do {
 211             value = value >> 7;
 212             length++;
 213         } while (value > 0);
 214         return length;
 215     }
 216 
 217     private final static long mask = 0x7F;
 218 
 219     private void writeVarInt(byte[] data, int off, long value) {
 220         int shift=63; // number of bitwise left-shifts of mask
 221         // first screen out leading zeros
 222         while ((shift > 0) && ((value & (mask << shift)) == 0)) shift-=7;
 223         // then write actual values
 224         while (shift > 0) {
 225             data[off++]=(byte) (((value & (mask << shift)) >> shift) | 0x80);
 226             shift-=7;
 227         }
 228         data[off] = (byte) (value & mask);
 229     }

 230 }
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