/*
* Copyright (c) 1996, 2002, 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
*
*/
public
class GZIPOutputStream extends DeflaterOutputStream {
/**
* CRC-32 of uncompressed data.
*/
protected CRC32 crc = new CRC32();
/*
* GZIP header magic number.
*/
private final static int GZIP_MAGIC = 0x8b1f;
/*
* Trailer size in bytes.
*
*/
private final static int TRAILER_SIZE = 8;
/**
* Creates a new output stream with the specified buffer size.
* @param out the output stream
* @param size the output buffer size
* @exception IOException If an I/O error has occurred.
* @exception IllegalArgumentException if size is <= 0
*/
public GZIPOutputStream(OutputStream out, int size) throws IOException {
super(out, new Deflater(Deflater.DEFAULT_COMPRESSION, true), size);
usesDefaultDeflater = true;
writeHeader();
crc.reset();
}
/**
* Creates a new output stream with a default buffer size.
* @param out the output stream
* @exception IOException If an I/O error has occurred.
*/
public GZIPOutputStream(OutputStream out) throws IOException {
this(out, 512);
}
/**
* 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 final static byte[] header = {
(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)
};
private void writeHeader() throws IOException {
out.write(header);
}
/*
* 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);
}
}