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 }