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/* * @(#)MidiMessage.java 1.30 05/11/17 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package javax.sound.midi; /** * <code>MidiMessage</code> is the base class for MIDI messages. They include * not only the standard MIDI messages that a synthesizer can respond to, but also * "meta-events" that can be used by sequencer programs. There are meta-events * for such information as lyrics, copyrights, tempo indications, time and key * signatures, markers, etc. For more information, see the Standard MIDI Files 1.0 * specification, which is part of the Complete MIDI 1.0 Detailed Specification * published by the MIDI Manufacturer's Association * (<a href = http://www.midi.org>http://www.midi.org</a>). * <p> * The base <code>MidiMessage</code> class provides access to three types of * information about a MIDI message: * <ul> * <li>The messages's status byte</li> * <li>The total length of the message in bytes (the status byte plus any data bytes)</li> * <li>A byte array containing the complete message</li> * </ul> * * <code>MidiMessage</code> includes methods to get, but not set, these values. * Setting them is a subclass responsibility. * <p> * <a name="integersVsBytes"></a> * The MIDI standard expresses MIDI data in bytes. However, because * Java<sup>TM</sup> uses signed bytes, the Java Sound API uses integers * instead of bytes when expressing MIDI data. For example, the * {@link #getStatus()} method of * <code>MidiMessage</code> returns MIDI status bytes as integers. If you are * processing MIDI data that originated outside Java Sound and now * is encoded as signed bytes, the bytes can * can be converted to integers using this conversion: * <center><code>int i = (int)(byte & 0xFF)</code></center> * <p> * If you simply need to pass a known MIDI byte value as a method parameter, * it can be expressed directly as an integer, using (for example) decimal or * hexidecimal notation. For instance, to pass the "active sensing" status byte * as the first argument to ShortMessage's * {@link ShortMessage#setMessage(int) setMessage(int)} * method, you can express it as 254 or 0xFE. * * @see Track * @see Sequence * @see Receiver * * @version 1.30, 05/11/17 * @author David Rivas * @author Kara Kytle */ public abstract class MidiMessage implements Cloneable { // Instance variables /** * The MIDI message data. The first byte is the status * byte for the message; subsequent bytes up to the length * of the message are data bytes for this message. * @see #getLength */ protected byte[] data; /** * The number of bytes in the MIDI message, including the * status byte and any data bytes. * @see #getLength */ protected int length = 0; /** * Constructs a new <code>MidiMessage</code>. This protected * constructor is called by concrete subclasses, which should * ensure that the data array specifies a complete, valid MIDI * message. * * @param data an array of bytes containing the complete message. * The message data may be changed using the <code>setMessage</code> * method. * * @see #setMessage */ protected MidiMessage(byte[] data) { this.data = data; if (data != null) { this.length = data.length; } } /** * Sets the data for the MIDI message. This protected * method is called by concrete subclasses, which should * ensure that the data array specifies a complete, valid MIDI * message. */ protected void setMessage(byte[] data, int length) throws InvalidMidiDataException { if (length < 0 || (length > 0 && length > data.length)) { throw new IndexOutOfBoundsException("length out of bounds: "+length); } this.length = length; if (this.data == null || this.data.length < this.length) { this.data = new byte[this.length]; } System.arraycopy(data, 0, this.data, 0, length); } /** * Obtains the MIDI message data. The first byte of the returned byte * array is the status byte of the message. Any subsequent bytes up to * the length of the message are data bytes. The byte array may have a * length which is greater than that of the actual message; the total * length of the message in bytes is reported by the <code>{@link #getLength}</code> * method. * * @return the byte array containing the complete <code>MidiMessage</code> data */ public byte[] getMessage() { byte[] returnedArray = new byte[length]; System.arraycopy(data, 0, returnedArray, 0, length); return returnedArray; } /** * Obtains the status byte for the MIDI message. The status "byte" is * represented as an integer; see the * <a href="#integersVsBytes">discussion</a> in the * <code>MidiMessage</code> class description. * * @return the integer representation of this event's status byte */ public int getStatus() { if (length > 0) { return (data[0] & 0xFF); } return 0; } /** * Obtains the total length of the MIDI message in bytes. A * MIDI message consists of one status byte and zero or more * data bytes. The return value ranges from 1 for system real-time messages, * to 2 or 3 for channel messages, to any value for meta and system * exclusive messages. * * @return the length of the message in bytes */ public int getLength() { return length; } /** * Creates a new object of the same class and with the same contents * as this object. * @return a clone of this instance. */ public abstract Object clone(); }