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package javax.sound.midi;
/**
* A {@code MetaMessage} is a {@link MidiMessage} that is not meaningful to
* synthesizers, but that can be stored in a MIDI file and interpreted by a
* sequencer program. (See the discussion in the {@code MidiMessage} class
* description.) The Standard MIDI Files specification defines various types of
* meta-events, such as sequence number, lyric, cue point, and set tempo. There
* are also 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>
* When data is being transported using MIDI wire protocol, a
* {@link ShortMessage} with the status value {@code 0xFF} represents a system
* reset message. In MIDI files, this same status value denotes a
* {@code MetaMessage}. The types of meta-message are distinguished from each
* other by the first byte that follows the status byte {@code 0xFF}. The
* subsequent bytes are data bytes. As with system exclusive messages, there are
* an arbitrary number of data bytes, depending on the type of
* {@code MetaMessage}.
*
* @author David Rivas
* @author Kara Kytle
* @see MetaEventListener
*/
public class MetaMessage extends MidiMessage {
/**
* Status byte for {@code MetaMessage} (0xFF, or 255), which is used in MIDI
* files. It has the same value as {@link ShortMessage#SYSTEM_RESET}, which
* is used in the real-time "MIDI wire" protocol.
*
* @see MidiMessage#getStatus
*/
public static final int META = 0xFF; // 255
/**
* The length of the actual message in the data array. This is used to
* determine how many bytes of the data array is the message, and how many
* are the status byte, the type byte, and the variable-length-int
* describing the length of the message.
*/
private int dataLength = 0;
/**
* Constructs a new {@code MetaMessage}. The contents of the message are not
* set here; use {@link #setMessage(int, byte[], int) setMessage} to set
* them subsequently.
*/
public MetaMessage() {
// Default meta message data: just the META status byte value
this(new byte[]{(byte) META, 0});
}
/**
* Constructs a new {@code MetaMessage} and sets the message parameters. The
* contents of the message can be changed by using the {@code setMessage}
* method.
*
* @param type meta-message type (must be less than 128)
* @param data the data bytes in the MIDI message
* @param length an amount of bytes in the {@code data} byte array; it
* should be non-negative and less than or equal to
* {@code data.length}
* @throws InvalidMidiDataException if the parameter values do not specify a
* valid MIDI meta message
* @see #setMessage(int, byte[], int)
* @see #getType()
* @see #getData()
* @since 1.7
*/
public MetaMessage(int type, byte[] data, int length)
throws InvalidMidiDataException {
super(null);
setMessage(type, data, length); // can throw InvalidMidiDataException
}
/**
* Constructs a new {@code MetaMessage}.
*
* @param data an array of bytes containing the complete message. The
* message data may be changed using the {@code setMessage} method.
* @see #setMessage
*/
protected MetaMessage(byte[] data) {
super(data);
//$$fb 2001-10-06: need to calculate dataLength. Fix for bug #4511796
if (data.length>=3) {
dataLength=data.length-3;
int pos=2;
while (pos<data.length && (data[pos] & 0x80)!=0) {
dataLength--; pos++;
}
}
}
/**
* Sets the message parameters for a {@code MetaMessage}. Since only one
* status byte value, {@code 0xFF}, is allowed for meta-messages, it does
* not need to be specified here. Calls to
* {@link MidiMessage#getStatus getStatus} return {@code 0xFF} for all
* meta-messages.
* <p>
* The {@code type} argument should be a valid value for the byte that
* follows the status byte in the {@code MetaMessage}. The {@code data}
* argument should contain all the subsequent bytes of the
* {@code MetaMessage}. In other words, the byte that specifies the type of
* {@code MetaMessage} is not considered a data byte.
*
* @param type meta-message type (must be less than 128)
* @param data the data bytes in the MIDI message
* @param length the number of bytes in the {@code data} byte array
* @throws InvalidMidiDataException if the parameter values do not specify a
* valid MIDI meta message
*/
public void setMessage(int type, byte[] data, int length) throws InvalidMidiDataException {
if (type >= 128 || type < 0) {
throw new InvalidMidiDataException("Invalid meta event with type " + type);
}
if ((length > 0 && length > data.length) || length < 0) {
throw new InvalidMidiDataException("length out of bounds: "+length);
}
this.length = 2 + getVarIntLength(length) + length;
this.dataLength = length;
this.data = new byte[this.length];
this.data[0] = (byte) META; // status value for MetaMessages (meta events)
this.data[1] = (byte) type; // MetaMessage type
writeVarInt(this.data, 2, length); // write the length as a variable int
if (length > 0) {
System.arraycopy(data, 0, this.data, this.length - this.dataLength, this.dataLength);
}
}
/**
* Obtains the type of the {@code MetaMessage}.
*
* @return an integer representing the {@code MetaMessage} type
*/
public int getType() {
if (length>=2) {
return data[1] & 0xFF;
}
return 0;
}
/**
* Obtains a copy of the data for the meta message. The returned array of
* bytes does not include the status byte or the message length data. The
* length of the data for the meta message is the length of the array. Note
* that the length of the entire message includes the status byte and the
* meta message type byte, and therefore may be longer than the returned
* array.
*
* @return array containing the meta message data
* @see MidiMessage#getLength
*/
public byte[] getData() {
byte[] returnedArray = new byte[dataLength];
System.arraycopy(data, (length - dataLength), returnedArray, 0, dataLength);
return returnedArray;
}
/**
* Creates a new object of the same class and with the same contents as this
* object.
*
* @return a clone of this instance
*/
@Override
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