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	/*
	* Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.util.zip;

	import java.io.OutputStream;
	import java.io.IOException;

	/**
	* This class implements a stream filter for writing compressed data in
	* the GZIP file format.
	* @author David Connelly
	* @since 1.1
	*
	*/
	public
	class GZIPOutputStream extends DeflaterOutputStream {
	/**
	* CRC-32 of uncompressed data.
	*/
	protected CRC32 crc = new CRC32();

	/*
	* GZIP header magic number.
	*/
	private static final int GZIP_MAGIC = 0x8b1f;

	/*
	* Trailer size in bytes.
	*
	*/
	private static final int TRAILER_SIZE = 8;

	/**
	* Creates a new output stream with the specified buffer size.
	*
	* <p>The new output stream instance is created as if by invoking
	* the 3-argument constructor GZIPOutputStream(out, size, false).
	*
	* @param out the output stream
	* @param size the output buffer size
	* @exception IOException If an I/O error has occurred.
	* @exception IllegalArgumentException if {@code size <= 0}
	*/
	public GZIPOutputStream(OutputStream out, int size) throws IOException {
	this(out, size, false);
	}

	/**
	* Creates a new output stream with the specified buffer size and
	* flush mode.
	*
	* @param out the output stream
	* @param size the output buffer size
	* @param syncFlush
	* if {@code true} invocation of the inherited
	* {@link DeflaterOutputStream#flush() flush()} method of
	* this instance flushes the compressor with flush mode
	* {@link Deflater#SYNC_FLUSH} before flushing the output
	* stream, otherwise only flushes the output stream
	* @exception IOException If an I/O error has occurred.
	* @exception IllegalArgumentException if {@code size <= 0}
	*
	* @since 1.7
	*/
	public GZIPOutputStream(OutputStream out, int size, boolean syncFlush)
	throws IOException
	{
	super(out, new Deflater(Deflater.DEFAULT_COMPRESSION, true),
	size,
	syncFlush);
	usesDefaultDeflater = true;
	writeHeader();
	crc.reset();
	}


	/**
	* Creates a new output stream with a default buffer size.
	*
	* <p>The new output stream instance is created as if by invoking
	* the 2-argument constructor GZIPOutputStream(out, false).
	*
	* @param out the output stream
	* @exception IOException If an I/O error has occurred.
	*/
	public GZIPOutputStream(OutputStream out) throws IOException {
	this(out, 512, false);
	}

	/**
	* Creates a new output stream with a default buffer size and
	* the specified flush mode.
	*
	* @param out the output stream
	* @param syncFlush
	* if {@code true} invocation of the inherited
	* {@link DeflaterOutputStream#flush() flush()} method of
	* this instance flushes the compressor with flush mode
	* {@link Deflater#SYNC_FLUSH} before flushing the output
	* stream, otherwise only flushes the output stream
	*
	* @exception IOException If an I/O error has occurred.
	*
	* @since 1.7
	*/
	public GZIPOutputStream(OutputStream out, boolean syncFlush)
	throws IOException
	{
	this(out, 512, syncFlush);
	}

	/**
	* Writes array of bytes to the compressed output stream. This method
	* will block until all the bytes are written.
	* @param buf the data to be written
	* @param off the start offset of the data
	* @param len the length of the data
	* @exception IOException If an I/O error has occurred.
	*/
	public synchronized void write(byte[] buf, int off, int len)
	throws IOException
	{
	super.write(buf, off, len);
	crc.update(buf, off, len);
	}

	/**
	* Finishes writing compressed data to the output stream without closing
	* the underlying stream. Use this method when applying multiple filters
	* in succession to the same output stream.
	* @exception IOException if an I/O error has occurred
	*/
	public void finish() throws IOException {
	if (!def.finished()) {
	def.finish();
	while (!def.finished()) {
	int len = def.deflate(buf, 0, buf.length);
	if (def.finished() && len <= buf.length - TRAILER_SIZE) {
	// last deflater buffer. Fit trailer at the end
	writeTrailer(buf, len);
	len = len + TRAILER_SIZE;
	out.write(buf, 0, len);
	return;
	}
	if (len > 0)
	out.write(buf, 0, len);
	}
	// if we can't fit the trailer at the end of the last
	// deflater buffer, we write it separately
	byte[] trailer = new byte[TRAILER_SIZE];
	writeTrailer(trailer, 0);
	out.write(trailer);
	}
	}

	/*
	* Writes GZIP member header.
	*/
	private void writeHeader() throws IOException {
	out.write(new byte[] {
	(byte) GZIP_MAGIC, // Magic number (short)
	(byte)(GZIP_MAGIC >> 8), // Magic number (short)
	Deflater.DEFLATED, // Compression method (CM)
	0, // Flags (FLG)
	0, // Modification time MTIME (int)
	0, // Modification time MTIME (int)
	0, // Modification time MTIME (int)
	0, // Modification time MTIME (int)
	0, // Extra flags (XFLG)
	0 // Operating system (OS)
	});
	}

	/*
	* Writes GZIP member trailer to a byte array, starting at a given
	* offset.
	*/
	private void writeTrailer(byte[] buf, int offset) throws IOException {
	writeInt((int)crc.getValue(), buf, offset); // CRC-32 of uncompr. data
	writeInt(def.getTotalIn(), buf, offset + 4); // Number of uncompr. bytes
	}

	/*
	* Writes integer in Intel byte order to a byte array, starting at a
	* given offset.
	*/
	private void writeInt(int i, byte[] buf, int offset) throws IOException {
	writeShort(i & 0xffff, buf, offset);
	writeShort((i >> 16) & 0xffff, buf, offset + 2);
	}

	/*
	* Writes short integer in Intel byte order to a byte array, starting
	* at a given offset
	*/
	private void writeShort(int s, byte[] buf, int offset) throws IOException {
	buf[offset] = (byte)(s & 0xff);
	buf[offset + 1] = (byte)((s >> 8) & 0xff);
	}
	}

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