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/*
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* Copyright 1999-2003 Sun Microsystems, Inc. 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. Sun designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*/
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package javax.sound.midi;
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import java.io.ByteArrayOutputStream;
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import java.io.DataOutputStream;
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import java.io.IOException;
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/**
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* A <code>MetaMessage</code> is a <code>{@link MidiMessage}</code> that is not meaningful to synthesizers, but
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* that can be stored in a MIDI file and interpreted by a sequencer program.
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* (See the discussion in the <code>MidiMessage</code>
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* class description.) The Standard MIDI Files specification defines
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* various types of meta-events, such as sequence number, lyric, cue point,
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* and set tempo. There are also meta-events
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* for such information as lyrics, copyrights, tempo indications, time and key
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* signatures, markers, etc. For more information, see the Standard MIDI Files 1.0
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* specification, which is part of the Complete MIDI 1.0 Detailed Specification
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* 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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*
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* <p>
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* When data is being transported using MIDI wire protocol,
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* a <code>{@link ShortMessage}</code> with the status value <code>0xFF</code> represents
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* a system reset message. In MIDI files, this same status value denotes a <code>MetaMessage</code>.
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* The types of meta-message are distinguished from each other by the first byte
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* that follows the status byte <code>0xFF</code>. The subsequent bytes are data
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* bytes. As with system exclusive messages, there are an arbitrary number of
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* data bytes, depending on the type of <code>MetaMessage</code>.
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*
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* @see MetaEventListener
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*
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* @author David Rivas
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* @author Kara Kytle
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*/
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public class MetaMessage extends MidiMessage {
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// Status byte defines
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/**
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* Status byte for <code>MetaMessage</code> (0xFF, or 255), which is used
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* in MIDI files. It has the same value as SYSTEM_RESET, which
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* is used in the real-time "MIDI wire" protocol.
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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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// Default meta message data: just the META status byte value
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// $$kk: 09.09.99: need a real event here!!
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private static byte[] defaultMessage = { (byte)META, 0 };
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// Instance variables
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/**
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* The length of the actual message in the data array.
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* This is used to determine how many bytes of the data array
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* is the message, and how many are the status byte, the
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* type byte, and the variable-length-int describing the
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* 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</code>. The contents of
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* the message are not set here; use
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* {@link #setMessage(int, byte[], int) setMessage}
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* to set them subsequently.
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*/
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public MetaMessage() {
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//super(defaultMessage);
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this(defaultMessage);
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}
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/**
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* Constructs a new <code>MetaMessage</code>.
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* @param data an array of bytes containing the complete message.
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* The message data may be changed using the <code>setMessage</code>
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* 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</code>.
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* Since only one status byte value, <code>0xFF</code>, is allowed for meta-messages,
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* it does not need to be specified here. Calls to <code>{@link MidiMessage#getStatus getStatus}</code> return
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* <code>0xFF</code> for all meta-messages.
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* <p>
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* The <code>type</code> argument should be a valid value for the byte that
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* follows the status byte in the <code>MetaMessage</code>. The <code>data</code> argument
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* should contain all the subsequent bytes of the <code>MetaMessage</code>. In other words,
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* the byte that specifies the type of <code>MetaMessage</code> 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</code>
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* byte array
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* @throws <code>InvalidMidiDataException</code> if the
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* parameter values do not specify a 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</code>.
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* @return an integer representing the <code>MetaMessage</code> 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
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* array of bytes does not include the status byte or the message
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* length data. The length of the data for the meta message is
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* the length of the array. Note that the length of the entire
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* message includes the status byte and the meta message type
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* byte, and therefore may be longer than the returned array.
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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
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* as this object.
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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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