001 /*
002 * Copyright 1996-2006 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025
026 package java.util.zip;
027
028 import java.io.SequenceInputStream;
029 import java.io.ByteArrayInputStream;
030 import java.io.InputStream;
031 import java.io.IOException;
032 import java.io.EOFException;
033
034 /**
035 * This class implements a stream filter for reading compressed data in
036 * the GZIP file format.
037 *
038 * @see InflaterInputStream
039 * @version 1.39, 05/05/07
040 * @author David Connelly
041 *
042 */
043 public class GZIPInputStream extends InflaterInputStream {
044 /**
045 * CRC-32 for uncompressed data.
046 */
047 protected CRC32 crc = new CRC32();
048
049 /**
050 * Indicates end of input stream.
051 */
052 protected boolean eos;
053
054 private boolean closed = false;
055
056 /**
057 * Check to make sure that this stream has not been closed
058 */
059 private void ensureOpen() throws IOException {
060 if (closed) {
061 throw new IOException("Stream closed");
062 }
063 }
064
065 /**
066 * Creates a new input stream with the specified buffer size.
067 * @param in the input stream
068 * @param size the input buffer size
069 * @exception IOException if an I/O error has occurred
070 * @exception IllegalArgumentException if size is <= 0
071 */
072 public GZIPInputStream(InputStream in, int size) throws IOException {
073 super (in, new Inflater(true), size);
074 usesDefaultInflater = true;
075 readHeader();
076 crc.reset();
077 }
078
079 /**
080 * Creates a new input stream with a default buffer size.
081 * @param in the input stream
082 * @exception IOException if an I/O error has occurred
083 */
084 public GZIPInputStream(InputStream in) throws IOException {
085 this (in, 512);
086 }
087
088 /**
089 * Reads uncompressed data into an array of bytes. If <code>len</code> is not
090 * zero, the method will block until some input can be decompressed; otherwise,
091 * no bytes are read and <code>0</code> is returned.
092 * @param buf the buffer into which the data is read
093 * @param off the start offset in the destination array <code>b</code>
094 * @param len the maximum number of bytes read
095 * @return the actual number of bytes read, or -1 if the end of the
096 * compressed input stream is reached
097 * @exception NullPointerException If <code>buf</code> is <code>null</code>.
098 * @exception IndexOutOfBoundsException If <code>off</code> is negative,
099 * <code>len</code> is negative, or <code>len</code> is greater than
100 * <code>buf.length - off</code>
101 * @exception IOException if an I/O error has occurred or the compressed
102 * input data is corrupt
103 */
104 public int read(byte[] buf, int off, int len) throws IOException {
105 ensureOpen();
106 if (eos) {
107 return -1;
108 }
109 len = super .read(buf, off, len);
110 if (len == -1) {
111 readTrailer();
112 eos = true;
113 } else {
114 crc.update(buf, off, len);
115 }
116 return len;
117 }
118
119 /**
120 * Closes this input stream and releases any system resources associated
121 * with the stream.
122 * @exception IOException if an I/O error has occurred
123 */
124 public void close() throws IOException {
125 if (!closed) {
126 super .close();
127 eos = true;
128 closed = true;
129 }
130 }
131
132 /**
133 * GZIP header magic number.
134 */
135 public final static int GZIP_MAGIC = 0x8b1f;
136
137 /*
138 * File header flags.
139 */
140 private final static int FTEXT = 1; // Extra text
141 private final static int FHCRC = 2; // Header CRC
142 private final static int FEXTRA = 4; // Extra field
143 private final static int FNAME = 8; // File name
144 private final static int FCOMMENT = 16; // File comment
145
146 /*
147 * Reads GZIP member header.
148 */
149 private void readHeader() throws IOException {
150 CheckedInputStream in = new CheckedInputStream(this .in, crc);
151 crc.reset();
152 // Check header magic
153 if (readUShort(in) != GZIP_MAGIC) {
154 throw new IOException("Not in GZIP format");
155 }
156 // Check compression method
157 if (readUByte(in) != 8) {
158 throw new IOException("Unsupported compression method");
159 }
160 // Read flags
161 int flg = readUByte(in);
162 // Skip MTIME, XFL, and OS fields
163 skipBytes(in, 6);
164 // Skip optional extra field
165 if ((flg & FEXTRA) == FEXTRA) {
166 skipBytes(in, readUShort(in));
167 }
168 // Skip optional file name
169 if ((flg & FNAME) == FNAME) {
170 while (readUByte(in) != 0)
171 ;
172 }
173 // Skip optional file comment
174 if ((flg & FCOMMENT) == FCOMMENT) {
175 while (readUByte(in) != 0)
176 ;
177 }
178 // Check optional header CRC
179 if ((flg & FHCRC) == FHCRC) {
180 int v = (int) crc.getValue() & 0xffff;
181 if (readUShort(in) != v) {
182 throw new IOException("Corrupt GZIP header");
183 }
184 }
185 }
186
187 /*
188 * Reads GZIP member trailer.
189 */
190 private void readTrailer() throws IOException {
191 InputStream in = this .in;
192 int n = inf.getRemaining();
193 if (n > 0) {
194 in = new SequenceInputStream(new ByteArrayInputStream(buf,
195 len - n, n), in);
196 }
197 // Uses left-to-right evaluation order
198 if ((readUInt(in) != crc.getValue()) ||
199 // rfc1952; ISIZE is the input size modulo 2^32
200 (readUInt(in) != (inf.getBytesWritten() & 0xffffffffL)))
201 throw new IOException("Corrupt GZIP trailer");
202 }
203
204 /*
205 * Reads unsigned integer in Intel byte order.
206 */
207 private long readUInt(InputStream in) throws IOException {
208 long s = readUShort(in);
209 return ((long) readUShort(in) << 16) | s;
210 }
211
212 /*
213 * Reads unsigned short in Intel byte order.
214 */
215 private int readUShort(InputStream in) throws IOException {
216 int b = readUByte(in);
217 return ((int) readUByte(in) << 8) | b;
218 }
219
220 /*
221 * Reads unsigned byte.
222 */
223 private int readUByte(InputStream in) throws IOException {
224 int b = in.read();
225 if (b == -1) {
226 throw new EOFException();
227 }
228 if (b < -1 || b > 255) {
229 // Report on this.in, not argument in; see read{Header, Trailer}.
230 throw new IOException(this .in.getClass().getName()
231 + ".read() returned value out of range -1..255: "
232 + b);
233 }
234 return b;
235 }
236
237 private byte[] tmpbuf = new byte[128];
238
239 /*
240 * Skips bytes of input data blocking until all bytes are skipped.
241 * Does not assume that the input stream is capable of seeking.
242 */
243 private void skipBytes(InputStream in, int n) throws IOException {
244 while (n > 0) {
245 int len = in.read(tmpbuf, 0, n < tmpbuf.length ? n
246 : tmpbuf.length);
247 if (len == -1) {
248 throw new EOFException();
249 }
250 n -= len;
251 }
252 }
253 }
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