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231 lines
9.0 KiB
Java
231 lines
9.0 KiB
Java
/*
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* Copyright (c) 1999, 2014, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package javax.sound.midi;
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/**
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* A {@code MetaMessage} is a {@link MidiMessage} that is not meaningful to
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* synthesizers, but that can be stored in a MIDI file and interpreted by a
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* sequencer program. (See the discussion in the {@code MidiMessage} class
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* description.) The Standard MIDI Files specification defines various types of
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* meta-events, such as sequence number, lyric, cue point, and set tempo. There
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* are also meta-events for such information as lyrics, copyrights, tempo
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* indications, time and key signatures, markers, etc. For more information, see
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* the Standard MIDI Files 1.0 specification, which is part of the Complete MIDI
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* 1.0 Detailed Specification published by the MIDI Manufacturer's Association
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* (<a href = http://www.midi.org>http://www.midi.org</a>).
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* <p>
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* When data is being transported using MIDI wire protocol, a
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* {@link ShortMessage} with the status value {@code 0xFF} represents a system
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* reset message. In MIDI files, this same status value denotes a
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* {@code MetaMessage}. The types of meta-message are distinguished from each
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* other by the first byte that follows the status byte {@code 0xFF}. The
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* subsequent bytes are data bytes. As with system exclusive messages, there are
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* an arbitrary number of data bytes, depending on the type of
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* {@code MetaMessage}.
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*
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* @author David Rivas
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* @author Kara Kytle
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* @see MetaEventListener
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*/
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public class MetaMessage extends MidiMessage {
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/**
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* Status byte for {@code MetaMessage} (0xFF, or 255), which is used in MIDI
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* files. It has the same value as SYSTEM_RESET, which is used in the
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* real-time "MIDI wire" protocol.
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*
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* @see MidiMessage#getStatus
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*/
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public static final int META = 0xFF; // 255
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/**
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* The length of the actual message in the data array. This is used to
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* determine how many bytes of the data array is the message, and how many
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* are the status byte, the type byte, and the variable-length-int
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* describing the length of the message.
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*/
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private int dataLength = 0;
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/**
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* Constructs a new {@code MetaMessage}. The contents of the message are not
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* set here; use {@link #setMessage(int, byte[], int) setMessage} to set
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* them subsequently.
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*/
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public MetaMessage() {
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// Default meta message data: just the META status byte value
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this(new byte[]{(byte) META, 0});
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}
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/**
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* Constructs a new {@code MetaMessage} and sets the message parameters. The
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* contents of the message can be changed by using the {@code setMessage}
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* method.
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*
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* @param type meta-message type (must be less than 128)
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* @param data the data bytes in the MIDI message
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* @param length an amount of bytes in the {@code data} byte array; it
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* should be non-negative and less than or equal to
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* {@code data.length}
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* @throws InvalidMidiDataException if the parameter values do not specify a
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* valid MIDI meta message
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* @see #setMessage(int, byte[], int)
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* @see #getType()
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* @see #getData()
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* @since 1.7
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*/
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public MetaMessage(int type, byte[] data, int length)
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throws InvalidMidiDataException {
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super(null);
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setMessage(type, data, length); // can throw InvalidMidiDataException
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}
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/**
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* Constructs a new {@code MetaMessage}.
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*
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* @param data an array of bytes containing the complete message. The
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* message data may be changed using the {@code setMessage} method.
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* @see #setMessage
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*/
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protected MetaMessage(byte[] data) {
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super(data);
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//$$fb 2001-10-06: need to calculate dataLength. Fix for bug #4511796
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if (data.length>=3) {
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dataLength=data.length-3;
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int pos=2;
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while (pos<data.length && (data[pos] & 0x80)!=0) {
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dataLength--; pos++;
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}
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}
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}
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/**
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* Sets the message parameters for a {@code MetaMessage}. Since only one
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* status byte value, {@code 0xFF}, is allowed for meta-messages, it does
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* not need to be specified here. Calls to
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* {@link MidiMessage#getStatus getStatus} return {@code 0xFF} for all
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* meta-messages.
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* <p>
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* The {@code type} argument should be a valid value for the byte that
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* follows the status byte in the {@code MetaMessage}. The {@code data}
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* argument should contain all the subsequent bytes of the
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* {@code MetaMessage}. In other words, the byte that specifies the type of
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* {@code MetaMessage} is not considered a data byte.
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*
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* @param type meta-message type (must be less than 128)
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* @param data the data bytes in the MIDI message
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* @param length the number of bytes in the {@code data} byte array
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* @throws InvalidMidiDataException if the parameter values do not specify a
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* valid MIDI meta message
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*/
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public void setMessage(int type, byte[] data, int length) throws InvalidMidiDataException {
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if (type >= 128 || type < 0) {
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throw new InvalidMidiDataException("Invalid meta event with type " + type);
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}
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if ((length > 0 && length > data.length) || length < 0) {
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throw new InvalidMidiDataException("length out of bounds: "+length);
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}
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this.length = 2 + getVarIntLength(length) + length;
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this.dataLength = length;
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this.data = new byte[this.length];
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this.data[0] = (byte) META; // status value for MetaMessages (meta events)
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this.data[1] = (byte) type; // MetaMessage type
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writeVarInt(this.data, 2, length); // write the length as a variable int
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if (length > 0) {
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System.arraycopy(data, 0, this.data, this.length - this.dataLength, this.dataLength);
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}
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}
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/**
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* Obtains the type of the {@code MetaMessage}.
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*
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* @return an integer representing the {@code MetaMessage} type
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*/
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public int getType() {
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if (length>=2) {
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return data[1] & 0xFF;
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}
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return 0;
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}
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/**
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* Obtains a copy of the data for the meta message. The returned array of
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* bytes does not include the status byte or the message length data. The
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* length of the data for the meta message is the length of the array. Note
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* that the length of the entire message includes the status byte and the
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* meta message type byte, and therefore may be longer than the returned
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* array.
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*
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* @return array containing the meta message data
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* @see MidiMessage#getLength
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*/
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public byte[] getData() {
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byte[] returnedArray = new byte[dataLength];
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System.arraycopy(data, (length - dataLength), returnedArray, 0, dataLength);
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return returnedArray;
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}
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/**
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* Creates a new object of the same class and with the same contents as this
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* object.
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*
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* @return a clone of this instance
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*/
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public Object clone() {
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byte[] newData = new byte[length];
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System.arraycopy(data, 0, newData, 0, newData.length);
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MetaMessage event = new MetaMessage(newData);
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return event;
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}
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// HELPER METHODS
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private int getVarIntLength(long value) {
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int length = 0;
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do {
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value = value >> 7;
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length++;
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} while (value > 0);
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return length;
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}
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private final static long mask = 0x7F;
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private void writeVarInt(byte[] data, int off, long value) {
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int shift=63; // number of bitwise left-shifts of mask
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// first screen out leading zeros
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while ((shift > 0) && ((value & (mask << shift)) == 0)) shift-=7;
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// then write actual values
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while (shift > 0) {
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data[off++]=(byte) (((value & (mask << shift)) >> shift) | 0x80);
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shift-=7;
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}
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data[off] = (byte) (value & mask);
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}
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}
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