001 /* GZIPOutputStream.java - Create a file in gzip format
002 Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038 package java.util.zip;
039
040 import java.io.IOException;
041 import java.io.OutputStream;
042
043 /**
044 * This filter stream is used to compress a stream into a "GZIP" stream.
045 * The "GZIP" format is described in RFC 1952.
046 *
047 * @author John Leuner
048 * @author Tom Tromey
049 * @since JDK 1.1
050 */
051
052 /* Written using on-line Java Platform 1.2 API Specification
053 * and JCL book.
054 * Believed complete and correct.
055 */
056
057 public class GZIPOutputStream extends DeflaterOutputStream
058 {
059 /**
060 * CRC-32 value for uncompressed data
061 */
062 protected CRC32 crc;
063
064 /**
065 * Creates a GZIPOutputStream with the default buffer size
066 *
067 * @param out The stream to read data (to be compressed) from
068 *
069 */
070 public GZIPOutputStream(OutputStream out) throws IOException
071 {
072 this(out, 4096);
073 }
074
075 /**
076 * Creates a GZIPOutputStream with the specified buffer size
077 *
078 * @param out The stream to read compressed data from
079 * @param size Size of the buffer to use
080 */
081 public GZIPOutputStream(OutputStream out, int size) throws IOException
082 {
083 super(out, new Deflater(Deflater.DEFAULT_COMPRESSION, true), size);
084 crc = new CRC32();
085 int mod_time = (int) (System.currentTimeMillis() / 1000L);
086 byte[] gzipHeader =
087 {
088 /* The two magic bytes */
089 (byte) GZIPInputStream.GZIP_MAGIC,
090 (byte) (GZIPInputStream.GZIP_MAGIC >> 8),
091
092 /* The compression type */
093 (byte) Deflater.DEFLATED,
094
095 /* The flags (not set) */
096 0,
097
098 /* The modification time */
099 (byte) mod_time, (byte) (mod_time >> 8),
100 (byte) (mod_time >> 16), (byte) (mod_time >> 24),
101
102 /* The extra flags */
103 0,
104
105 /* The OS type (unknown) */
106 (byte) 255
107 };
108
109 out.write(gzipHeader);
110 // System.err.println("wrote GZIP header (" + gzipHeader.length + " bytes )");
111 }
112
113 public synchronized void write(byte[] buf, int off, int len)
114 throws IOException
115 {
116 super.write(buf, off, len);
117 crc.update(buf, off, len);
118 }
119
120 /**
121 * Writes remaining compressed output data to the output stream
122 * and closes it.
123 */
124 public void close() throws IOException
125 {
126 finish();
127 out.close();
128 }
129
130 public void finish() throws IOException
131 {
132 super.finish();
133
134 int totalin = def.getTotalIn();
135 int crcval = (int) (crc.getValue() & 0xffffffff);
136
137 // System.err.println("CRC val is " + Integer.toHexString( crcval ) + " and length " + Integer.toHexString(totalin));
138
139 byte[] gzipFooter =
140 {
141 (byte) crcval, (byte) (crcval >> 8),
142 (byte) (crcval >> 16), (byte) (crcval >> 24),
143
144 (byte) totalin, (byte) (totalin >> 8),
145 (byte) (totalin >> 16), (byte) (totalin >> 24)
146 };
147
148 out.write(gzipFooter);
149 // System.err.println("wrote GZIP trailer (" + gzipFooter.length + " bytes )");
150 }
151 }