1 /*
2 * Copyright (c) 1996, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.util.zip;
27
28 import java.io.OutputStream;
29 import java.io.IOException;
30
31 /**
32 * This class implements a stream filter for writing compressed data in
33 * the GZIP file format.
34 * @author David Connelly
35 *
36 */
37 public
38 class GZIPOutputStream extends DeflaterOutputStream {
39 /**
40 * CRC-32 of uncompressed data.
41 */
42 protected CRC32 crc = new CRC32();
43
44 /*
45 * GZIP header magic number.
46 */
47 private final static int GZIP_MAGIC = 0x8b1f;
48
49 /*
50 * Trailer size in bytes.
51 *
52 */
53 private final static int TRAILER_SIZE = 8;
54
55 /**
56 * Creates a new output stream with the specified buffer size.
57 *
58 * <p>The new output stream instance is created as if by invoking
59 * the 3-argument constructor GZIPOutputStream(out, size, false).
60 *
61 * @param out the output stream
62 * @param size the output buffer size
63 * @exception IOException If an I/O error has occurred.
64 * @exception IllegalArgumentException if {@code size <= 0}
65 */
66 public GZIPOutputStream(OutputStream out, int size) throws IOException {
67 this(out, size, false);
68 }
69
70 /**
71 * Creates a new output stream with the specified buffer size and
72 * flush mode.
73 *
74 * @param out the output stream
75 * @param size the output buffer size
76 * @param syncFlush
77 * if {@code true} invocation of the inherited
78 * {@link DeflaterOutputStream#flush() flush()} method of
79 * this instance flushes the compressor with flush mode
80 * {@link Deflater#SYNC_FLUSH} before flushing the output
81 * stream, otherwise only flushes the output stream
82 * @exception IOException If an I/O error has occurred.
83 * @exception IllegalArgumentException if {@code size <= 0}
84 *
85 * @since 1.7
86 */
87 public GZIPOutputStream(OutputStream out, int size, boolean syncFlush)
88 throws IOException
89 {
90 super(out, new Deflater(Deflater.DEFAULT_COMPRESSION, true),
91 size,
92 syncFlush);
93 usesDefaultDeflater = true;
94 writeHeader();
95 crc.reset();
96 }
97
98
99 /**
100 * Creates a new output stream with a default buffer size.
101 *
102 * <p>The new output stream instance is created as if by invoking
103 * the 2-argument constructor GZIPOutputStream(out, false).
104 *
105 * @param out the output stream
106 * @exception IOException If an I/O error has occurred.
107 */
108 public GZIPOutputStream(OutputStream out) throws IOException {
109 this(out, 512, false);
110 }
111
112 /**
113 * Creates a new output stream with a default buffer size and
114 * the specified flush mode.
115 *
116 * @param out the output stream
117 * @param syncFlush
118 * if {@code true} invocation of the inherited
119 * {@link DeflaterOutputStream#flush() flush()} method of
120 * this instance flushes the compressor with flush mode
121 * {@link Deflater#SYNC_FLUSH} before flushing the output
122 * stream, otherwise only flushes the output stream
123 *
124 * @exception IOException If an I/O error has occurred.
125 *
126 * @since 1.7
127 */
128 public GZIPOutputStream(OutputStream out, boolean syncFlush)
129 throws IOException
130 {
131 this(out, 512, syncFlush);
132 }
133
134 /**
135 * Writes array of bytes to the compressed output stream. This method
136 * will block until all the bytes are written.
137 * @param buf the data to be written
138 * @param off the start offset of the data
139 * @param len the length of the data
140 * @exception IOException If an I/O error has occurred.
141 */
142 public synchronized void write(byte[] buf, int off, int len)
143 throws IOException
144 {
145 super.write(buf, off, len);
146 crc.update(buf, off, len);
147 }
148
149 /**
150 * Finishes writing compressed data to the output stream without closing
151 * the underlying stream. Use this method when applying multiple filters
152 * in succession to the same output stream.
153 * @exception IOException if an I/O error has occurred
154 */
155 public void finish() throws IOException {
156 if (!def.finished()) {
157 def.finish();
158 while (!def.finished()) {
159 int len = def.deflate(buf, 0, buf.length);
160 if (def.finished() && len <= buf.length - TRAILER_SIZE) {
161 // last deflater buffer. Fit trailer at the end
162 writeTrailer(buf, len);
163 len = len + TRAILER_SIZE;
164 out.write(buf, 0, len);
165 return;
166 }
167 if (len > 0)
168 out.write(buf, 0, len);
169 }
170 // if we can't fit the trailer at the end of the last
171 // deflater buffer, we write it separately
172 byte[] trailer = new byte[TRAILER_SIZE];
173 writeTrailer(trailer, 0);
174 out.write(trailer);
175 }
176 }
177
178 /*
179 * Writes GZIP member header.
180 */
181 private void writeHeader() throws IOException {
182 out.write(new byte[] {
183 (byte) GZIP_MAGIC, // Magic number (short)
184 (byte)(GZIP_MAGIC >> 8), // Magic number (short)
185 Deflater.DEFLATED, // Compression method (CM)
186 0, // Flags (FLG)
187 0, // Modification time MTIME (int)
188 0, // Modification time MTIME (int)
189 0, // Modification time MTIME (int)
190 0, // Modification time MTIME (int)
191 0, // Extra flags (XFLG)
192 0 // Operating system (OS)
193 });
194 }
195
196 /*
197 * Writes GZIP member trailer to a byte array, starting at a given
198 * offset.
199 */
200 private void writeTrailer(byte[] buf, int offset) throws IOException {
201 writeInt((int)crc.getValue(), buf, offset); // CRC-32 of uncompr. data
202 writeInt(def.getTotalIn(), buf, offset + 4); // Number of uncompr. bytes
203 }
204
205 /*
206 * Writes integer in Intel byte order to a byte array, starting at a
207 * given offset.
208 */
209 private void writeInt(int i, byte[] buf, int offset) throws IOException {
210 writeShort(i & 0xffff, buf, offset);
211 writeShort((i >> 16) & 0xffff, buf, offset + 2);
212 }
213
214 /*
215 * Writes short integer in Intel byte order to a byte array, starting
216 * at a given offset
217 */
218 private void writeShort(int s, byte[] buf, int offset) throws IOException {
219 buf[offset] = (byte)(s & 0xff);
220 buf[offset + 1] = (byte)((s >> 8) & 0xff);
221 }
222 }