| Inflater.java |
1 /*
2 * %W% %E%
3 *
4 * Copyright (c) 2008, Oracle and/or its affiliates. All rights reserved.
5 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6 */
7
8 package java.util.zip;
9
10 /**
11 * This class provides support for general purpose decompression using the
12 * popular ZLIB compression library. The ZLIB compression library was
13 * initially developed as part of the PNG graphics standard and is not
14 * protected by patents. It is fully described in the specifications at
15 * the <a href="package-summary.html#package_description">java.util.zip
16 * package description</a>.
17 *
18 * <p>The following code fragment demonstrates a trivial compression
19 * and decompression of a string using <tt>Deflater</tt> and
20 * <tt>Inflater</tt>.
21 *
22 * <blockquote><pre>
23 * try {
24 * // Encode a String into bytes
25 * String inputString = "blahblahblah€€";
26 * byte[] input = inputString.getBytes("UTF-8");
27 *
28 * // Compress the bytes
29 * byte[] output = new byte[100];
30 * Deflater compresser = new Deflater();
31 * compresser.setInput(input);
32 * compresser.finish();
33 * int compressedDataLength = compresser.deflate(output);
34 *
35 * // Decompress the bytes
36 * Inflater decompresser = new Inflater();
37 * decompresser.setInput(output, 0, compressedDataLength);
38 * byte[] result = new byte[100];
39 * int resultLength = decompresser.inflate(result);
40 * decompresser.end();
41 *
42 * // Decode the bytes into a String
43 * String outputString = new String(result, 0, resultLength, "UTF-8");
44 * } catch(java.io.UnsupportedEncodingException ex) {
45 * // handle
46 * } catch (java.util.zip.DataFormatException ex) {
47 * // handle
48 * }
49 * </pre></blockquote>
50 *
51 * @see Deflater
52 * @version 1.47, 04/07/06
53 * @author David Connelly
54 *
55 */
56 public
57 class Inflater {
58 private final ZStreamRef zsRef;
59 private byte[] buf = emptyBuf;
60 private int off, len;
61 private boolean finished;
62 private boolean needDict;
63
64 private static byte[] emptyBuf = new byte[0];
65
66 static {
67 /* Zip library is loaded from System.initializeSystemClass */
68 initIDs();
69 }
70
71 /**
72 * Creates a new decompressor. If the parameter 'nowrap' is true then
73 * the ZLIB header and checksum fields will not be used. This provides
74 * compatibility with the compression format used by both GZIP and PKZIP.
75 * <p>
76 * Note: When using the 'nowrap' option it is also necessary to provide
77 * an extra "dummy" byte as input. This is required by the ZLIB native
78 * library in order to support certain optimizations.
79 *
80 * @param nowrap if true then support GZIP compatible compression
81 */
82 public Inflater(boolean nowrap) {
83 zsRef = new ZStreamRef(init(nowrap));
84 }
85
86 /**
87 * Creates a new decompressor.
88 */
89 public Inflater() {
90 this(false);
91 }
92
93 /**
94 * Sets input data for decompression. Should be called whenever
95 * needsInput() returns true indicating that more input data is
96 * required.
97 * @param b the input data bytes
98 * @param off the start offset of the input data
99 * @param len the length of the input data
100 * @see Inflater#needsInput
101 */
102 public void setInput(byte[] b, int off, int len) {
103 if (b == null) {
104 throw new NullPointerException();
105 }
106 if (off < 0 || len < 0 || off > b.length - len) {
107 throw new ArrayIndexOutOfBoundsException();
108 }
109 synchronized (zsRef) {
110 this.buf = b;
111 this.off = off;
112 this.len = len;
113 }
114 }
115
116 /**
117 * Sets input data for decompression. Should be called whenever
118 * needsInput() returns true indicating that more input data is
119 * required.
120 * @param b the input data bytes
121 * @see Inflater#needsInput
122 */
123 public void setInput(byte[] b) {
124 setInput(b, 0, b.length);
125 }
126
127 /**
128 * Sets the preset dictionary to the given array of bytes. Should be
129 * called when inflate() returns 0 and needsDictionary() returns true
130 * indicating that a preset dictionary is required. The method getAdler()
131 * can be used to get the Adler-32 value of the dictionary needed.
132 * @param b the dictionary data bytes
133 * @param off the start offset of the data
134 * @param len the length of the data
135 * @see Inflater#needsDictionary
136 * @see Inflater#getAdler
137 */
138 public void setDictionary(byte[] b, int off, int len) {
139 if (b == null) {
140 throw new NullPointerException();
141 }
142 if (off < 0 || len < 0 || off > b.length - len) {
143 throw new ArrayIndexOutOfBoundsException();
144 }
145 synchronized (zsRef) {
146 ensureOpen();
147 setDictionary(zsRef.address(), b, off, len);
148 needDict = false;
149 }
150 }
151
152 /**
153 * Sets the preset dictionary to the given array of bytes. Should be
154 * called when inflate() returns 0 and needsDictionary() returns true
155 * indicating that a preset dictionary is required. The method getAdler()
156 * can be used to get the Adler-32 value of the dictionary needed.
157 * @param b the dictionary data bytes
158 * @see Inflater#needsDictionary
159 * @see Inflater#getAdler
160 */
161 public void setDictionary(byte[] b) {
162 setDictionary(b, 0, b.length);
163 }
164
165 /**
166 * Returns the total number of bytes remaining in the input buffer.
167 * This can be used to find out what bytes still remain in the input
168 * buffer after decompression has finished.
169 * @return the total number of bytes remaining in the input buffer
170 */
171 public int getRemaining() {
172 synchronized (zsRef) {
173 return len;
174 }
175 }
176
177 /**
178 * Returns true if no data remains in the input buffer. This can
179 * be used to determine if #setInput should be called in order
180 * to provide more input.
181 * @return true if no data remains in the input buffer
182 */
183 public boolean needsInput() {
184 synchronized (zsRef) {
185 return len <= 0;
186 }
187 }
188
189 /**
190 * Returns true if a preset dictionary is needed for decompression.
191 * @return true if a preset dictionary is needed for decompression
192 * @see Inflater#setDictionary
193 */
194 public boolean needsDictionary() {
195 synchronized (zsRef) {
196 return needDict;
197 }
198 }
199
200 /**
201 * Returns true if the end of the compressed data stream has been
202 * reached.
203 * @return true if the end of the compressed data stream has been
204 * reached
205 */
206 public boolean finished() {
207 synchronized (zsRef) {
208 return finished;
209 }
210 }
211
212 /**
213 * Uncompresses bytes into specified buffer. Returns actual number
214 * of bytes uncompressed. A return value of 0 indicates that
215 * needsInput() or needsDictionary() should be called in order to
216 * determine if more input data or a preset dictionary is required.
217 * In the latter case, getAdler() can be used to get the Adler-32
218 * value of the dictionary required.
219 * @param b the buffer for the uncompressed data
220 * @param off the start offset of the data
221 * @param len the maximum number of uncompressed bytes
222 * @return the actual number of uncompressed bytes
223 * @exception DataFormatException if the compressed data format is invalid
224 * @see Inflater#needsInput
225 * @see Inflater#needsDictionary
226 */
227 public int inflate(byte[] b, int off, int len)
228 throws DataFormatException
229 {
230 if (b == null) {
231 throw new NullPointerException();
232 }
233 if (off < 0 || len < 0 || off > b.length - len) {
234 throw new ArrayIndexOutOfBoundsException();
235 }
236 synchronized (zsRef) {
237 ensureOpen();
238 return inflateBytes(zsRef.address(), b, off, len);
239 }
240 }
241
242 /**
243 * Uncompresses bytes into specified buffer. Returns actual number
244 * of bytes uncompressed. A return value of 0 indicates that
245 * needsInput() or needsDictionary() should be called in order to
246 * determine if more input data or a preset dictionary is required.
247 * In the latter case, getAdler() can be used to get the Adler-32
248 * value of the dictionary required.
249 * @param b the buffer for the uncompressed data
250 * @return the actual number of uncompressed bytes
251 * @exception DataFormatException if the compressed data format is invalid
252 * @see Inflater#needsInput
253 * @see Inflater#needsDictionary
254 */
255 public int inflate(byte[] b) throws DataFormatException {
256 return inflate(b, 0, b.length);
257 }
258
259 /**
260 * Returns the ADLER-32 value of the uncompressed data.
261 * @return the ADLER-32 value of the uncompressed data
262 */
263 public int getAdler() {
264 synchronized (zsRef) {
265 ensureOpen();
266 return getAdler(zsRef.address());
267 }
268 }
269
270 /**
271 * Returns the total number of compressed bytes input so far.
272 *
273 * <p>Since the number of bytes may be greater than
274 * Integer.MAX_VALUE, the {@link #getBytesRead()} method is now
275 * the preferred means of obtaining this information.</p>
276 *
277 * @return the total number of compressed bytes input so far
278 */
279 public int getTotalIn() {
280 return (int) getBytesRead();
281 }
282
283 /**
284 * Returns the total number of compressed bytes input so far.</p>
285 *
286 * @return the total (non-negative) number of compressed bytes input so far
287 * @since 1.5
288 */
289 public long getBytesRead() {
290 synchronized (zsRef) {
291 ensureOpen();
292 return getBytesRead(zsRef.address());
293 }
294 }
295
296 /**
297 * Returns the total number of uncompressed bytes output so far.
298 *
299 * <p>Since the number of bytes may be greater than
300 * Integer.MAX_VALUE, the {@link #getBytesWritten()} method is now
301 * the preferred means of obtaining this information.</p>
302 *
303 * @return the total number of uncompressed bytes output so far
304 */
305 public int getTotalOut() {
306 return (int) getBytesWritten();
307 }
308
309 /**
310 * Returns the total number of uncompressed bytes output so far.</p>
311 *
312 * @return the total (non-negative) number of uncompressed bytes output so far
313 * @since 1.5
314 */
315 public long getBytesWritten() {
316 synchronized (zsRef) {
317 ensureOpen();
318 return getBytesWritten(zsRef.address());
319 }
320 }
321
322 /**
323 * Resets inflater so that a new set of input data can be processed.
324 */
325 public void reset() {
326 synchronized (zsRef) {
327 ensureOpen();
328 reset(zsRef.address());
329 buf = emptyBuf;
330 finished = false;
331 needDict = false;
332 off = len = 0;
333 }
334 }
335
336 /**
337 * Closes the decompressor and discards any unprocessed input.
338 * This method should be called when the decompressor is no longer
339 * being used, but will also be called automatically by the finalize()
340 * method. Once this method is called, the behavior of the Inflater
341 * object is undefined.
342 */
343 public void end() {
344 synchronized (zsRef) {
345 long addr = zsRef.address();
346 zsRef.clear();
347 if (addr != 0) {
348 end(addr);
349 buf = null;
350 }
351 }
352 }
353
354 /**
355 * Closes the decompressor when garbage is collected.
356 */
357 protected void finalize() {
358 end();
359 }
360
361 private void ensureOpen () {
362 assert Thread.holdsLock(zsRef);
363 if (zsRef.address() == 0)
364 throw new NullPointerException("Inflater has been closed");
365 }
366
367 private native static void initIDs();
368 private native static long init(boolean nowrap);
369 private native static void setDictionary(long addr, byte[] b, int off,
370 int len);
371 private native int inflateBytes(long addr, byte[] b, int off, int len)
372 throws DataFormatException;
373 private native static int getAdler(long addr);
374 private native static long getBytesRead(long addr);
375 private native static long getBytesWritten(long addr);
376 private native static void reset(long addr);
377 private native static void end(long addr);
378 }
379