| Deflater.java |
1 /*
2 * %W% %E%
3 *
4 * Copyright (c) 2006, 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 compression 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 Inflater
52 * @version %I%, %G%
53 * @author David Connelly
54 */
55 public
56 class Deflater {
57
58 private final ZStreamRef zsRef;
59 private byte[] buf = new byte[0];
60 private int off, len;
61 private int level, strategy;
62 private boolean setParams;
63 private boolean finish, finished;
64
65 /**
66 * Compression method for the deflate algorithm (the only one currently
67 * supported).
68 */
69 public static final int DEFLATED = 8;
70
71 /**
72 * Compression level for no compression.
73 */
74 public static final int NO_COMPRESSION = 0;
75
76 /**
77 * Compression level for fastest compression.
78 */
79 public static final int BEST_SPEED = 1;
80
81 /**
82 * Compression level for best compression.
83 */
84 public static final int BEST_COMPRESSION = 9;
85
86 /**
87 * Default compression level.
88 */
89 public static final int DEFAULT_COMPRESSION = -1;
90
91 /**
92 * Compression strategy best used for data consisting mostly of small
93 * values with a somewhat random distribution. Forces more Huffman coding
94 * and less string matching.
95 */
96 public static final int FILTERED = 1;
97
98 /**
99 * Compression strategy for Huffman coding only.
100 */
101 public static final int HUFFMAN_ONLY = 2;
102
103 /**
104 * Default compression strategy.
105 */
106 public static final int DEFAULT_STRATEGY = 0;
107
108 static {
109 /* Zip library is loaded from System.initializeSystemClass */
110 initIDs();
111 }
112
113 /**
114 * Creates a new compressor using the specified compression level.
115 * If 'nowrap' is true then the ZLIB header and checksum fields will
116 * not be used in order to support the compression format used in
117 * both GZIP and PKZIP.
118 * @param level the compression level (0-9)
119 * @param nowrap if true then use GZIP compatible compression
120 */
121 public Deflater(int level, boolean nowrap) {
122 this.level = level;
123 this.strategy = DEFAULT_STRATEGY;
124 this.zsRef = new ZStreamRef(init(level, DEFAULT_STRATEGY, nowrap));
125 }
126
127 /**
128 * Creates a new compressor using the specified compression level.
129 * Compressed data will be generated in ZLIB format.
130 * @param level the compression level (0-9)
131 */
132 public Deflater(int level) {
133 this(level, false);
134 }
135
136 /**
137 * Creates a new compressor with the default compression level.
138 * Compressed data will be generated in ZLIB format.
139 */
140 public Deflater() {
141 this(DEFAULT_COMPRESSION, false);
142 }
143
144 /**
145 * Sets input data for compression. This should be called whenever
146 * needsInput() returns true indicating that more input data is required.
147 * @param b the input data bytes
148 * @param off the start offset of the data
149 * @param len the length of the data
150 * @see Deflater#needsInput
151 */
152 public void setInput(byte[] b, int off, int len) {
153 if (b== null) {
154 throw new NullPointerException();
155 }
156 if (off < 0 || len < 0 || off > b.length - len) {
157 throw new ArrayIndexOutOfBoundsException();
158 }
159 synchronized (zsRef) {
160 this.buf = b;
161 this.off = off;
162 this.len = len;
163 }
164 }
165
166 /**
167 * Sets input data for compression. This should be called whenever
168 * needsInput() returns true indicating that more input data is required.
169 * @param b the input data bytes
170 * @see Deflater#needsInput
171 */
172 public void setInput(byte[] b) {
173 setInput(b, 0, b.length);
174 }
175
176 /**
177 * Sets preset dictionary for compression. A preset dictionary is used
178 * when the history buffer can be predetermined. When the data is later
179 * uncompressed with Inflater.inflate(), Inflater.getAdler() can be called
180 * in order to get the Adler-32 value of the dictionary required for
181 * decompression.
182 * @param b the dictionary data bytes
183 * @param off the start offset of the data
184 * @param len the length of the data
185 * @see Inflater#inflate
186 * @see Inflater#getAdler
187 */
188 public void setDictionary(byte[] b, int off, int len) {
189 if (b == null) {
190 throw new NullPointerException();
191 }
192 if (off < 0 || len < 0 || off > b.length - len) {
193 throw new ArrayIndexOutOfBoundsException();
194 }
195 synchronized (zsRef) {
196 ensureOpen();
197 setDictionary(zsRef.address(), b, off, len);
198 }
199 }
200
201 /**
202 * Sets preset dictionary for compression. A preset dictionary is used
203 * when the history buffer can be predetermined. When the data is later
204 * uncompressed with Inflater.inflate(), Inflater.getAdler() can be called
205 * in order to get the Adler-32 value of the dictionary required for
206 * decompression.
207 * @param b the dictionary data bytes
208 * @see Inflater#inflate
209 * @see Inflater#getAdler
210 */
211 public void setDictionary(byte[] b) {
212 setDictionary(b, 0, b.length);
213 }
214
215 /**
216 * Sets the compression strategy to the specified value.
217 * @param strategy the new compression strategy
218 * @exception IllegalArgumentException if the compression strategy is
219 * invalid
220 */
221 public void setStrategy(int strategy) {
222 switch (strategy) {
223 case DEFAULT_STRATEGY:
224 case FILTERED:
225 case HUFFMAN_ONLY:
226 break;
227 default:
228 throw new IllegalArgumentException();
229 }
230 synchronized (zsRef) {
231 if (this.strategy != strategy) {
232 this.strategy = strategy;
233 setParams = true;
234 }
235 }
236 }
237
238 /**
239 * Sets the current compression level to the specified value.
240 * @param level the new compression level (0-9)
241 * @exception IllegalArgumentException if the compression level is invalid
242 */
243 public void setLevel(int level) {
244 if ((level < 0 || level > 9) && level != DEFAULT_COMPRESSION) {
245 throw new IllegalArgumentException("invalid compression level");
246 }
247 synchronized (zsRef) {
248 if (this.level != level) {
249 this.level = level;
250 setParams = true;
251 }
252 }
253 }
254
255 /**
256 * Returns true if the input data buffer is empty and setInput()
257 * should be called in order to provide more input.
258 * @return true if the input data buffer is empty and setInput()
259 * should be called in order to provide more input
260 */
261 public boolean needsInput() {
262 return len <= 0;
263 }
264
265 /**
266 * When called, indicates that compression should end with the current
267 * contents of the input buffer.
268 */
269 public void finish() {
270 synchronized (zsRef) {
271 finish = true;
272 }
273 }
274
275 /**
276 * Returns true if the end of the compressed data output stream has
277 * been reached.
278 * @return true if the end of the compressed data output stream has
279 * been reached
280 */
281 public boolean finished() {
282 synchronized (zsRef) {
283 return finished;
284 }
285 }
286
287 /**
288 * Fills specified buffer with compressed data. Returns actual number
289 * of bytes of compressed data. A return value of 0 indicates that
290 * needsInput() should be called in order to determine if more input
291 * data is required.
292 * @param b the buffer for the compressed data
293 * @param off the start offset of the data
294 * @param len the maximum number of bytes of compressed data
295 * @return the actual number of bytes of compressed data
296 */
297 public int deflate(byte[] b, int off, int len) {
298 if (b == null) {
299 throw new NullPointerException();
300 }
301 if (off < 0 || len < 0 || off > b.length - len) {
302 throw new ArrayIndexOutOfBoundsException();
303 }
304 synchronized (zsRef) {
305 ensureOpen();
306 return deflateBytes(zsRef.address(), b, off, len);
307 }
308 }
309
310 /**
311 * Fills specified buffer with compressed data. Returns actual number
312 * of bytes of compressed data. A return value of 0 indicates that
313 * needsInput() should be called in order to determine if more input
314 * data is required.
315 * @param b the buffer for the compressed data
316 * @return the actual number of bytes of compressed data
317 */
318 public int deflate(byte[] b) {
319 return deflate(b, 0, b.length);
320 }
321
322 /**
323 * Returns the ADLER-32 value of the uncompressed data.
324 * @return the ADLER-32 value of the uncompressed data
325 */
326 public int getAdler() {
327 synchronized (zsRef) {
328 ensureOpen();
329 return getAdler(zsRef.address());
330 }
331 }
332
333 /**
334 * Returns the total number of uncompressed bytes input so far.
335 *
336 * <p>Since the number of bytes may be greater than
337 * Integer.MAX_VALUE, the {@link #getBytesRead()} method is now
338 * the preferred means of obtaining this information.</p>
339 *
340 * @return the total number of uncompressed bytes input so far
341 */
342 public int getTotalIn() {
343 return (int) getBytesRead();
344 }
345
346 /**
347 * Returns the total number of uncompressed bytes input so far.</p>
348 *
349 * @return the total (non-negative) number of uncompressed bytes input so far
350 * @since 1.5
351 */
352 public long getBytesRead() {
353 synchronized (zsRef) {
354 ensureOpen();
355 return getBytesRead(zsRef.address());
356 }
357 }
358
359 /**
360 * Returns the total number of compressed bytes output so far.
361 *
362 * <p>Since the number of bytes may be greater than
363 * Integer.MAX_VALUE, the {@link #getBytesWritten()} method is now
364 * the preferred means of obtaining this information.</p>
365 *
366 * @return the total number of compressed bytes output so far
367 */
368 public int getTotalOut() {
369 return (int) getBytesWritten();
370 }
371
372 /**
373 * Returns the total number of compressed bytes output so far.</p>
374 *
375 * @return the total (non-negative) number of compressed bytes output so far
376 * @since 1.5
377 */
378 public long getBytesWritten() {
379 synchronized (zsRef) {
380 ensureOpen();
381 return getBytesWritten(zsRef.address());
382 }
383 }
384
385 /**
386 * Resets deflater so that a new set of input data can be processed.
387 * Keeps current compression level and strategy settings.
388 */
389 public void reset() {
390 synchronized (zsRef) {
391 ensureOpen();
392 reset(zsRef.address());
393 finish = false;
394 finished = false;
395 off = len = 0;
396 }
397 }
398
399 /**
400 * Closes the compressor and discards any unprocessed input.
401 * This method should be called when the compressor is no longer
402 * being used, but will also be called automatically by the
403 * finalize() method. Once this method is called, the behavior
404 * of the Deflater object is undefined.
405 */
406 public void end() {
407 synchronized (zsRef) {
408 long addr = zsRef.address();
409 zsRef.clear();
410 if (addr != 0) {
411 end(addr);
412 buf = null;
413 }
414 }
415 }
416
417 /**
418 * Closes the compressor when garbage is collected.
419 */
420 protected void finalize() {
421 end();
422 }
423
424 private void ensureOpen() {
425 assert Thread.holdsLock(zsRef);
426 if (zsRef.address() == 0)
427 throw new NullPointerException("Deflater has been closed");
428 }
429
430 private static native void initIDs();
431 private native static long init(int level, int strategy, boolean nowrap);
432 private native static void setDictionary(long addr, byte[] b, int off,
433 int len);
434 private native int deflateBytes(long addr, byte[] b, int off, int len);
435 private native static int getAdler(long addr);
436 private native static long getBytesRead(long addr);
437 private native static long getBytesWritten(long addr);
438 private native static void reset(long addr);
439 private native static void end(long addr);
440 }
441