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1: /* Deflater.java - Compress a data stream 2: Copyright (C) 1999, 2000, 2001, 2004, 2005 Free Software Foundation, Inc. 3: 4: This file is part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2, or (at your option) 9: any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; see the file COPYING. If not, write to the 18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19: 02110-1301 USA. 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: package java.util.zip; 39: 40: /** 41: * This is the Deflater class. The deflater class compresses input 42: * with the deflate algorithm described in RFC 1951. It has several 43: * compression levels and three different strategies described below. 44: * 45: * This class is <i>not</i> thread safe. This is inherent in the API, due 46: * to the split of deflate and setInput. 47: * 48: * @author Jochen Hoenicke 49: * @author Tom Tromey 50: */ 51: public class Deflater 52: { 53: /** 54: * The best and slowest compression level. This tries to find very 55: * long and distant string repetitions. 56: */ 57: public static final int BEST_COMPRESSION = 9; 58: /** 59: * The worst but fastest compression level. 60: */ 61: public static final int BEST_SPEED = 1; 62: /** 63: * The default compression level. 64: */ 65: public static final int DEFAULT_COMPRESSION = -1; 66: /** 67: * This level won't compress at all but output uncompressed blocks. 68: */ 69: public static final int NO_COMPRESSION = 0; 70: 71: /** 72: * The default strategy. 73: */ 74: public static final int DEFAULT_STRATEGY = 0; 75: /** 76: * This strategy will only allow longer string repetitions. It is 77: * useful for random data with a small character set. 78: */ 79: public static final int FILTERED = 1; 80: 81: /** 82: * This strategy will not look for string repetitions at all. It 83: * only encodes with Huffman trees (which means, that more common 84: * characters get a smaller encoding. 85: */ 86: public static final int HUFFMAN_ONLY = 2; 87: 88: /** 89: * The compression method. This is the only method supported so far. 90: * There is no need to use this constant at all. 91: */ 92: public static final int DEFLATED = 8; 93: 94: /* 95: * The Deflater can do the following state transitions: 96: * 97: * (1) -> INIT_STATE ----> INIT_FINISHING_STATE ---. 98: * / | (2) (5) | 99: * / v (5) | 100: * (3)| SETDICT_STATE ---> SETDICT_FINISHING_STATE |(3) 101: * \ | (3) | ,-------' 102: * | | | (3) / 103: * v v (5) v v 104: * (1) -> BUSY_STATE ----> FINISHING_STATE 105: * | (6) 106: * v 107: * FINISHED_STATE 108: * \_____________________________________/ 109: * | (7) 110: * v 111: * CLOSED_STATE 112: * 113: * (1) If we should produce a header we start in INIT_STATE, otherwise 114: * we start in BUSY_STATE. 115: * (2) A dictionary may be set only when we are in INIT_STATE, then 116: * we change the state as indicated. 117: * (3) Whether a dictionary is set or not, on the first call of deflate 118: * we change to BUSY_STATE. 119: * (4) -- intentionally left blank -- :) 120: * (5) FINISHING_STATE is entered, when flush() is called to indicate that 121: * there is no more INPUT. There are also states indicating, that 122: * the header wasn't written yet. 123: * (6) FINISHED_STATE is entered, when everything has been flushed to the 124: * internal pending output buffer. 125: * (7) At any time (7) 126: * 127: */ 128: 129: private static final int IS_SETDICT = 0x01; 130: private static final int IS_FLUSHING = 0x04; 131: private static final int IS_FINISHING = 0x08; 132: 133: private static final int INIT_STATE = 0x00; 134: private static final int SETDICT_STATE = 0x01; 135: private static final int INIT_FINISHING_STATE = 0x08; 136: private static final int SETDICT_FINISHING_STATE = 0x09; 137: private static final int BUSY_STATE = 0x10; 138: private static final int FLUSHING_STATE = 0x14; 139: private static final int FINISHING_STATE = 0x1c; 140: private static final int FINISHED_STATE = 0x1e; 141: private static final int CLOSED_STATE = 0x7f; 142: 143: /** Compression level. */ 144: private int level; 145: 146: /** should we include a header. */ 147: private boolean noHeader; 148: 149: /** The current state. */ 150: private int state; 151: 152: /** The total bytes of output written. */ 153: private long totalOut; 154: 155: /** The pending output. */ 156: private DeflaterPending pending; 157: 158: /** The deflater engine. */ 159: private DeflaterEngine engine; 160: 161: /** 162: * Creates a new deflater with default compression level. 163: */ 164: public Deflater() 165: { 166: this(DEFAULT_COMPRESSION, false); 167: } 168: 169: /** 170: * Creates a new deflater with given compression level. 171: * @param lvl the compression level, a value between NO_COMPRESSION 172: * and BEST_COMPRESSION, or DEFAULT_COMPRESSION. 173: * @exception IllegalArgumentException if lvl is out of range. 174: */ 175: public Deflater(int lvl) 176: { 177: this(lvl, false); 178: } 179: 180: /** 181: * Creates a new deflater with given compression level. 182: * @param lvl the compression level, a value between NO_COMPRESSION 183: * and BEST_COMPRESSION. 184: * @param nowrap true, iff we should suppress the deflate header at the 185: * beginning and the adler checksum at the end of the output. This is 186: * useful for the GZIP format. 187: * @exception IllegalArgumentException if lvl is out of range. 188: */ 189: public Deflater(int lvl, boolean nowrap) 190: { 191: if (lvl == DEFAULT_COMPRESSION) 192: lvl = 6; 193: else if (lvl < NO_COMPRESSION || lvl > BEST_COMPRESSION) 194: throw new IllegalArgumentException(); 195: 196: pending = new DeflaterPending(); 197: engine = new DeflaterEngine(pending); 198: this.noHeader = nowrap; 199: setStrategy(DEFAULT_STRATEGY); 200: setLevel(lvl); 201: reset(); 202: } 203: 204: /** 205: * Resets the deflater. The deflater acts afterwards as if it was 206: * just created with the same compression level and strategy as it 207: * had before. 208: */ 209: public void reset() 210: { 211: state = (noHeader ? BUSY_STATE : INIT_STATE); 212: totalOut = 0; 213: pending.reset(); 214: engine.reset(); 215: } 216: 217: /** 218: * Frees all objects allocated by the compressor. There's no 219: * reason to call this, since you can just rely on garbage 220: * collection. Exists only for compatibility against Sun's JDK, 221: * where the compressor allocates native memory. 222: * If you call any method (even reset) afterwards the behaviour is 223: * <i>undefined</i>. 224: */ 225: public void end() 226: { 227: engine = null; 228: pending = null; 229: state = CLOSED_STATE; 230: } 231: 232: /** 233: * Gets the current adler checksum of the data that was processed so 234: * far. 235: */ 236: public int getAdler() 237: { 238: return engine.getAdler(); 239: } 240: 241: /** 242: * Gets the number of input bytes processed so far. 243: */ 244: @Deprecated 245: public int getTotalIn() 246: { 247: return (int) engine.getTotalIn(); 248: } 249: 250: /** 251: * Gets the number of input bytes processed so far. 252: * @since 1.5 253: */ 254: public long getBytesRead() 255: { 256: return engine.getTotalIn(); 257: } 258: 259: /** 260: * Gets the number of output bytes so far. 261: */ 262: @Deprecated 263: public int getTotalOut() 264: { 265: return (int) totalOut; 266: } 267: 268: /** 269: * Gets the number of output bytes so far. 270: * @since 1.5 271: */ 272: public long getBytesWritten() 273: { 274: return totalOut; 275: } 276: 277: /** 278: * Finalizes this object. 279: */ 280: protected void finalize() 281: { 282: /* Exists solely for compatibility. We don't have any native state. */ 283: } 284: 285: /** 286: * Flushes the current input block. Further calls to deflate() will 287: * produce enough output to inflate everything in the current input 288: * block. This is not part of Sun's JDK so I have made it package 289: * private. It is used by DeflaterOutputStream to implement 290: * flush(). 291: */ 292: void flush() { 293: state |= IS_FLUSHING; 294: } 295: 296: /** 297: * Finishes the deflater with the current input block. It is an error 298: * to give more input after this method was called. This method must 299: * be called to force all bytes to be flushed. 300: */ 301: public void finish() { 302: state |= IS_FLUSHING | IS_FINISHING; 303: } 304: 305: /** 306: * Returns true iff the stream was finished and no more output bytes 307: * are available. 308: */ 309: public boolean finished() 310: { 311: return state == FINISHED_STATE && pending.isFlushed(); 312: } 313: 314: /** 315: * Returns true, if the input buffer is empty. 316: * You should then call setInput(). <br> 317: * 318: * <em>NOTE</em>: This method can also return true when the stream 319: * was finished. 320: */ 321: public boolean needsInput() 322: { 323: return engine.needsInput(); 324: } 325: 326: /** 327: * Sets the data which should be compressed next. This should be only 328: * called when needsInput indicates that more input is needed. 329: * If you call setInput when needsInput() returns false, the 330: * previous input that is still pending will be thrown away. 331: * The given byte array should not be changed, before needsInput() returns 332: * true again. 333: * This call is equivalent to <code>setInput(input, 0, input.length)</code>. 334: * @param input the buffer containing the input data. 335: * @exception IllegalStateException if the buffer was finished() or ended(). 336: */ 337: public void setInput(byte[] input) 338: { 339: setInput(input, 0, input.length); 340: } 341: 342: /** 343: * Sets the data which should be compressed next. This should be 344: * only called when needsInput indicates that more input is needed. 345: * The given byte array should not be changed, before needsInput() returns 346: * true again. 347: * @param input the buffer containing the input data. 348: * @param off the start of the data. 349: * @param len the length of the data. 350: * @exception IllegalStateException if the buffer was finished() or ended() 351: * or if previous input is still pending. 352: */ 353: public void setInput(byte[] input, int off, int len) 354: { 355: if ((state & IS_FINISHING) != 0) 356: throw new IllegalStateException("finish()/end() already called"); 357: engine.setInput(input, off, len); 358: } 359: 360: /** 361: * Sets the compression level. There is no guarantee of the exact 362: * position of the change, but if you call this when needsInput is 363: * true the change of compression level will occur somewhere near 364: * before the end of the so far given input. 365: * @param lvl the new compression level. 366: */ 367: public void setLevel(int lvl) 368: { 369: if (lvl == DEFAULT_COMPRESSION) 370: lvl = 6; 371: else if (lvl < NO_COMPRESSION || lvl > BEST_COMPRESSION) 372: throw new IllegalArgumentException(); 373: 374: 375: if (level != lvl) 376: { 377: level = lvl; 378: engine.setLevel(lvl); 379: } 380: } 381: 382: /** 383: * Sets the compression strategy. Strategy is one of 384: * DEFAULT_STRATEGY, HUFFMAN_ONLY and FILTERED. For the exact 385: * position where the strategy is changed, the same as for 386: * setLevel() applies. 387: * @param stgy the new compression strategy. 388: */ 389: public void setStrategy(int stgy) 390: { 391: if (stgy != DEFAULT_STRATEGY && stgy != FILTERED 392: && stgy != HUFFMAN_ONLY) 393: throw new IllegalArgumentException(); 394: engine.setStrategy(stgy); 395: } 396: 397: /** 398: * Deflates the current input block to the given array. It returns 399: * the number of bytes compressed, or 0 if either 400: * needsInput() or finished() returns true or length is zero. 401: * @param output the buffer where to write the compressed data. 402: */ 403: public int deflate(byte[] output) 404: { 405: return deflate(output, 0, output.length); 406: } 407: 408: /** 409: * Deflates the current input block to the given array. It returns 410: * the number of bytes compressed, or 0 if either 411: * needsInput() or finished() returns true or length is zero. 412: * @param output the buffer where to write the compressed data. 413: * @param offset the offset into the output array. 414: * @param length the maximum number of bytes that may be written. 415: * @exception IllegalStateException if end() was called. 416: * @exception IndexOutOfBoundsException if offset and/or length 417: * don't match the array length. 418: */ 419: public int deflate(byte[] output, int offset, int length) 420: { 421: int origLength = length; 422: 423: if (state == CLOSED_STATE) 424: throw new IllegalStateException("Deflater closed"); 425: 426: if (state < BUSY_STATE) 427: { 428: /* output header */ 429: int header = (DEFLATED + 430: ((DeflaterConstants.MAX_WBITS - 8) << 4)) << 8; 431: int level_flags = (level - 1) >> 1; 432: if (level_flags < 0 || level_flags > 3) 433: level_flags = 3; 434: header |= level_flags << 6; 435: if ((state & IS_SETDICT) != 0) 436: /* Dictionary was set */ 437: header |= DeflaterConstants.PRESET_DICT; 438: header += 31 - (header % 31); 439: 440: pending.writeShortMSB(header); 441: if ((state & IS_SETDICT) != 0) 442: { 443: int chksum = engine.getAdler(); 444: engine.resetAdler(); 445: pending.writeShortMSB(chksum >> 16); 446: pending.writeShortMSB(chksum & 0xffff); 447: } 448: 449: state = BUSY_STATE | (state & (IS_FLUSHING | IS_FINISHING)); 450: } 451: 452: for (;;) 453: { 454: int count = pending.flush(output, offset, length); 455: offset += count; 456: totalOut += count; 457: length -= count; 458: if (length == 0 || state == FINISHED_STATE) 459: break; 460: 461: if (!engine.deflate((state & IS_FLUSHING) != 0, 462: (state & IS_FINISHING) != 0)) 463: { 464: if (state == BUSY_STATE) 465: /* We need more input now */ 466: return origLength - length; 467: else if (state == FLUSHING_STATE) 468: { 469: if (level != NO_COMPRESSION) 470: { 471: /* We have to supply some lookahead. 8 bit lookahead 472: * are needed by the zlib inflater, and we must fill 473: * the next byte, so that all bits are flushed. 474: */ 475: int neededbits = 8 + ((-pending.getBitCount()) & 7); 476: while (neededbits > 0) 477: { 478: /* write a static tree block consisting solely of 479: * an EOF: 480: */ 481: pending.writeBits(2, 10); 482: neededbits -= 10; 483: } 484: } 485: state = BUSY_STATE; 486: } 487: else if (state == FINISHING_STATE) 488: { 489: pending.alignToByte(); 490: /* We have completed the stream */ 491: if (!noHeader) 492: { 493: int adler = engine.getAdler(); 494: pending.writeShortMSB(adler >> 16); 495: pending.writeShortMSB(adler & 0xffff); 496: } 497: state = FINISHED_STATE; 498: } 499: } 500: } 501: 502: return origLength - length; 503: } 504: 505: /** 506: * Sets the dictionary which should be used in the deflate process. 507: * This call is equivalent to <code>setDictionary(dict, 0, 508: * dict.length)</code>. 509: * @param dict the dictionary. 510: * @exception IllegalStateException if setInput () or deflate () 511: * were already called or another dictionary was already set. 512: */ 513: public void setDictionary(byte[] dict) 514: { 515: setDictionary(dict, 0, dict.length); 516: } 517: 518: /** 519: * Sets the dictionary which should be used in the deflate process. 520: * The dictionary should be a byte array containing strings that are 521: * likely to occur in the data which should be compressed. The 522: * dictionary is not stored in the compressed output, only a 523: * checksum. To decompress the output you need to supply the same 524: * dictionary again. 525: * @param dict the dictionary. 526: * @param offset an offset into the dictionary. 527: * @param length the length of the dictionary. 528: * @exception IllegalStateException if setInput () or deflate () were 529: * already called or another dictionary was already set. 530: */ 531: public void setDictionary(byte[] dict, int offset, int length) 532: { 533: if (state != INIT_STATE) 534: throw new IllegalStateException(); 535: 536: state = SETDICT_STATE; 537: engine.setDictionary(dict, offset, length); 538: } 539: }
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