1 /* +++ deflate.c */ 2 /* deflate.c -- compress data using the deflation algorithm 3 * Copyright (C) 1995-1996 Jean-loup Gailly. 4 * For conditions of distribution and use, see copyright notice in zlib.h 5 */ 6 7 /* 8 * ALGORITHM 9 * 10 * The "deflation" process depends on being able to identify portions 11 * of the input text which are identical to earlier input (within a 12 * sliding window trailing behind the input currently being processed). 13 * 14 * The most straightforward technique turns out to be the fastest for 15 * most input files: try all possible matches and select the longest. 16 * The key feature of this algorithm is that insertions into the string 17 * dictionary are very simple and thus fast, and deletions are avoided 18 * completely. Insertions are performed at each input character, whereas 19 * string matches are performed only when the previous match ends. So it 20 * is preferable to spend more time in matches to allow very fast string 21 * insertions and avoid deletions. The matching algorithm for small 22 * strings is inspired from that of Rabin & Karp. A brute force approach 23 * is used to find longer strings when a small match has been found. 24 * A similar algorithm is used in comic (by Jan-Mark Wams) and freeze 25 * (by Leonid Broukhis). 26 * A previous version of this file used a more sophisticated algorithm 27 * (by Fiala and Greene) which is guaranteed to run in linear amortized 28 * time, but has a larger average cost, uses more memory and is patented. 29 * However the F&G algorithm may be faster for some highly redundant 30 * files if the parameter max_chain_length (described below) is too large. 31 * 32 * ACKNOWLEDGEMENTS 33 * 34 * The idea of lazy evaluation of matches is due to Jan-Mark Wams, and 35 * I found it in 'freeze' written by Leonid Broukhis. 36 * Thanks to many people for bug reports and testing. 37 * 38 * REFERENCES 39 * 40 * Deutsch, L.P.,"DEFLATE Compressed Data Format Specification". 41 * Available in ftp://ds.internic.net/rfc/rfc1951.txt 42 * 43 * A description of the Rabin and Karp algorithm is given in the book 44 * "Algorithms" by R. Sedgewick, Addison-Wesley, p252. 45 * 46 * Fiala,E.R., and Greene,D.H. 47 * Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595 48 * 49 */ 50 51 #include <linux/module.h> 52 #include <linux/zutil.h> 53 #include "defutil.h" 54 55 56 /* =========================================================================== 57 * Function prototypes. 58 */ 59 typedef enum { 60 need_more, /* block not completed, need more input or more output */ 61 block_done, /* block flush performed */ 62 finish_started, /* finish started, need only more output at next deflate */ 63 finish_done /* finish done, accept no more input or output */ 64 } block_state; 65 66 typedef block_state (*compress_func) (deflate_state *s, int flush); 67 /* Compression function. Returns the block state after the call. */ 68 69 static void fill_window (deflate_state *s); 70 static block_state deflate_stored (deflate_state *s, int flush); 71 static block_state deflate_fast (deflate_state *s, int flush); 72 static block_state deflate_slow (deflate_state *s, int flush); 73 static void lm_init (deflate_state *s); 74 static void putShortMSB (deflate_state *s, uInt b); 75 static void flush_pending (z_streamp strm); 76 static int read_buf (z_streamp strm, Byte *buf, unsigned size); 77 static uInt longest_match (deflate_state *s, IPos cur_match); 78 79 #ifdef DEBUG_ZLIB 80 static void check_match (deflate_state *s, IPos start, IPos match, 81 int length); 82 #endif 83 84 /* =========================================================================== 85 * Local data 86 */ 87 88 #define NIL 0 89 /* Tail of hash chains */ 90 91 #ifndef TOO_FAR 92 # define TOO_FAR 4096 93 #endif 94 /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */ 95 96 #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1) 97 /* Minimum amount of lookahead, except at the end of the input file. 98 * See deflate.c for comments about the MIN_MATCH+1. 99 */ 100 101 /* Values for max_lazy_match, good_match and max_chain_length, depending on 102 * the desired pack level (0..9). The values given below have been tuned to 103 * exclude worst case performance for pathological files. Better values may be 104 * found for specific files. 105 */ 106 typedef struct config_s { 107 ush good_length; /* reduce lazy search above this match length */ 108 ush max_lazy; /* do not perform lazy search above this match length */ 109 ush nice_length; /* quit search above this match length */ 110 ush max_chain; 111 compress_func func; 112 } config; 113 114 static const config configuration_table[10] = { 115 /* good lazy nice chain */ 116 /* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */ 117 /* 1 */ {4, 4, 8, 4, deflate_fast}, /* maximum speed, no lazy matches */ 118 /* 2 */ {4, 5, 16, 8, deflate_fast}, 119 /* 3 */ {4, 6, 32, 32, deflate_fast}, 120 121 /* 4 */ {4, 4, 16, 16, deflate_slow}, /* lazy matches */ 122 /* 5 */ {8, 16, 32, 32, deflate_slow}, 123 /* 6 */ {8, 16, 128, 128, deflate_slow}, 124 /* 7 */ {8, 32, 128, 256, deflate_slow}, 125 /* 8 */ {32, 128, 258, 1024, deflate_slow}, 126 /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* maximum compression */ 127 128 /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4 129 * For deflate_fast() (levels <= 3) good is ignored and lazy has a different 130 * meaning. 131 */ 132 133 #define EQUAL 0 134 /* result of memcmp for equal strings */ 135 136 /* =========================================================================== 137 * Update a hash value with the given input byte 138 * IN assertion: all calls to UPDATE_HASH are made with consecutive 139 * input characters, so that a running hash key can be computed from the 140 * previous key instead of complete recalculation each time. 141 */ 142 #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask) 143 144 145 /* =========================================================================== 146 * Insert string str in the dictionary and set match_head to the previous head 147 * of the hash chain (the most recent string with same hash key). Return 148 * the previous length of the hash chain. 149 * IN assertion: all calls to INSERT_STRING are made with consecutive 150 * input characters and the first MIN_MATCH bytes of str are valid 151 * (except for the last MIN_MATCH-1 bytes of the input file). 152 */ 153 #define INSERT_STRING(s, str, match_head) \ 154 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \ 155 s->prev[(str) & s->w_mask] = match_head = s->head[s->ins_h], \ 156 s->head[s->ins_h] = (Pos)(str)) 157 158 /* =========================================================================== 159 * Initialize the hash table (avoiding 64K overflow for 16 bit systems). 160 * prev[] will be initialized on the fly. 161 */ 162 #define CLEAR_HASH(s) \ 163 s->head[s->hash_size-1] = NIL; \ 164 memset((char *)s->head, 0, (unsigned)(s->hash_size-1)*sizeof(*s->head)); 165 166 /* ========================================================================= */ 167 int zlib_deflateInit2( 168 z_streamp strm, 169 int level, 170 int method, 171 int windowBits, 172 int memLevel, 173 int strategy 174 ) 175 { 176 deflate_state *s; 177 int noheader = 0; 178 deflate_workspace *mem; 179 180 ush *overlay; 181 /* We overlay pending_buf and d_buf+l_buf. This works since the average 182 * output size for (length,distance) codes is <= 24 bits. 183 */ 184 185 if (strm == NULL) return Z_STREAM_ERROR; 186 187 strm->msg = NULL; 188 189 if (level == Z_DEFAULT_COMPRESSION) level = 6; 190 191 mem = (deflate_workspace *) strm->workspace; 192 193 if (windowBits < 0) { /* undocumented feature: suppress zlib header */ 194 noheader = 1; 195 windowBits = -windowBits; 196 } 197 if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED || 198 windowBits < 9 || windowBits > 15 || level < 0 || level > 9 || 199 strategy < 0 || strategy > Z_HUFFMAN_ONLY) { 200 return Z_STREAM_ERROR; 201 } 202 s = (deflate_state *) &(mem->deflate_memory); 203 strm->state = (struct internal_state *)s; 204 s->strm = strm; 205 206 s->noheader = noheader; 207 s->w_bits = windowBits; 208 s->w_size = 1 << s->w_bits; 209 s->w_mask = s->w_size - 1; 210 211 s->hash_bits = memLevel + 7; 212 s->hash_size = 1 << s->hash_bits; 213 s->hash_mask = s->hash_size - 1; 214 s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH); 215 216 s->window = (Byte *) mem->window_memory; 217 s->prev = (Pos *) mem->prev_memory; 218 s->head = (Pos *) mem->head_memory; 219 220 s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */ 221 222 overlay = (ush *) mem->overlay_memory; 223 s->pending_buf = (uch *) overlay; 224 s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L); 225 226 s->d_buf = overlay + s->lit_bufsize/sizeof(ush); 227 s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize; 228 229 s->level = level; 230 s->strategy = strategy; 231 s->method = (Byte)method; 232 233 return zlib_deflateReset(strm); 234 } 235 236 /* ========================================================================= */ 237 #if 0 238 int zlib_deflateSetDictionary( 239 z_streamp strm, 240 const Byte *dictionary, 241 uInt dictLength 242 ) 243 { 244 deflate_state *s; 245 uInt length = dictLength; 246 uInt n; 247 IPos hash_head = 0; 248 249 if (strm == NULL || strm->state == NULL || dictionary == NULL) 250 return Z_STREAM_ERROR; 251 252 s = (deflate_state *) strm->state; 253 if (s->status != INIT_STATE) return Z_STREAM_ERROR; 254 255 strm->adler = zlib_adler32(strm->adler, dictionary, dictLength); 256 257 if (length < MIN_MATCH) return Z_OK; 258 if (length > MAX_DIST(s)) { 259 length = MAX_DIST(s); 260 #ifndef USE_DICT_HEAD 261 dictionary += dictLength - length; /* use the tail of the dictionary */ 262 #endif 263 } 264 memcpy((char *)s->window, dictionary, length); 265 s->strstart = length; 266 s->block_start = (long)length; 267 268 /* Insert all strings in the hash table (except for the last two bytes). 269 * s->lookahead stays null, so s->ins_h will be recomputed at the next 270 * call of fill_window. 271 */ 272 s->ins_h = s->window[0]; 273 UPDATE_HASH(s, s->ins_h, s->window[1]); 274 for (n = 0; n <= length - MIN_MATCH; n++) { 275 INSERT_STRING(s, n, hash_head); 276 } 277 if (hash_head) hash_head = 0; /* to make compiler happy */ 278 return Z_OK; 279 } 280 #endif /* 0 */ 281 282 /* ========================================================================= */ 283 int zlib_deflateReset( 284 z_streamp strm 285 ) 286 { 287 deflate_state *s; 288 289 if (strm == NULL || strm->state == NULL) 290 return Z_STREAM_ERROR; 291 292 strm->total_in = strm->total_out = 0; 293 strm->msg = NULL; 294 strm->data_type = Z_UNKNOWN; 295 296 s = (deflate_state *)strm->state; 297 s->pending = 0; 298 s->pending_out = s->pending_buf; 299 300 if (s->noheader < 0) { 301 s->noheader = 0; /* was set to -1 by deflate(..., Z_FINISH); */ 302 } 303 s->status = s->noheader ? BUSY_STATE : INIT_STATE; 304 strm->adler = 1; 305 s->last_flush = Z_NO_FLUSH; 306 307 zlib_tr_init(s); 308 lm_init(s); 309 310 return Z_OK; 311 } 312 313 /* ========================================================================= */ 314 #if 0 315 int zlib_deflateParams( 316 z_streamp strm, 317 int level, 318 int strategy 319 ) 320 { 321 deflate_state *s; 322 compress_func func; 323 int err = Z_OK; 324 325 if (strm == NULL || strm->state == NULL) return Z_STREAM_ERROR; 326 s = (deflate_state *) strm->state; 327 328 if (level == Z_DEFAULT_COMPRESSION) { 329 level = 6; 330 } 331 if (level < 0 || level > 9 || strategy < 0 || strategy > Z_HUFFMAN_ONLY) { 332 return Z_STREAM_ERROR; 333 } 334 func = configuration_table[s->level].func; 335 336 if (func != configuration_table[level].func && strm->total_in != 0) { 337 /* Flush the last buffer: */ 338 err = zlib_deflate(strm, Z_PARTIAL_FLUSH); 339 } 340 if (s->level != level) { 341 s->level = level; 342 s->max_lazy_match = configuration_table[level].max_lazy; 343 s->good_match = configuration_table[level].good_length; 344 s->nice_match = configuration_table[level].nice_length; 345 s->max_chain_length = configuration_table[level].max_chain; 346 } 347 s->strategy = strategy; 348 return err; 349 } 350 #endif /* 0 */ 351 352 /* ========================================================================= 353 * Put a short in the pending buffer. The 16-bit value is put in MSB order. 354 * IN assertion: the stream state is correct and there is enough room in 355 * pending_buf. 356 */ 357 static void putShortMSB( 358 deflate_state *s, 359 uInt b 360 ) 361 { 362 put_byte(s, (Byte)(b >> 8)); 363 put_byte(s, (Byte)(b & 0xff)); 364 } 365 366 /* ========================================================================= 367 * Flush as much pending output as possible. All deflate() output goes 368 * through this function so some applications may wish to modify it 369 * to avoid allocating a large strm->next_out buffer and copying into it. 370 * (See also read_buf()). 371 */ 372 static void flush_pending( 373 z_streamp strm 374 ) 375 { 376 deflate_state *s = (deflate_state *) strm->state; 377 unsigned len = s->pending; 378 379 if (len > strm->avail_out) len = strm->avail_out; 380 if (len == 0) return; 381 382 if (strm->next_out != NULL) { 383 memcpy(strm->next_out, s->pending_out, len); 384 strm->next_out += len; 385 } 386 s->pending_out += len; 387 strm->total_out += len; 388 strm->avail_out -= len; 389 s->pending -= len; 390 if (s->pending == 0) { 391 s->pending_out = s->pending_buf; 392 } 393 } 394 395 /* ========================================================================= */ 396 int zlib_deflate( 397 z_streamp strm, 398 int flush 399 ) 400 { 401 int old_flush; /* value of flush param for previous deflate call */ 402 deflate_state *s; 403 404 if (strm == NULL || strm->state == NULL || 405 flush > Z_FINISH || flush < 0) { 406 return Z_STREAM_ERROR; 407 } 408 s = (deflate_state *) strm->state; 409 410 if ((strm->next_in == NULL && strm->avail_in != 0) || 411 (s->status == FINISH_STATE && flush != Z_FINISH)) { 412 return Z_STREAM_ERROR; 413 } 414 if (strm->avail_out == 0) return Z_BUF_ERROR; 415 416 s->strm = strm; /* just in case */ 417 old_flush = s->last_flush; 418 s->last_flush = flush; 419 420 /* Write the zlib header */ 421 if (s->status == INIT_STATE) { 422 423 uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8; 424 uInt level_flags = (s->level-1) >> 1; 425 426 if (level_flags > 3) level_flags = 3; 427 header |= (level_flags << 6); 428 if (s->strstart != 0) header |= PRESET_DICT; 429 header += 31 - (header % 31); 430 431 s->status = BUSY_STATE; 432 putShortMSB(s, header); 433 434 /* Save the adler32 of the preset dictionary: */ 435 if (s->strstart != 0) { 436 putShortMSB(s, (uInt)(strm->adler >> 16)); 437 putShortMSB(s, (uInt)(strm->adler & 0xffff)); 438 } 439 strm->adler = 1L; 440 } 441 442 /* Flush as much pending output as possible */ 443 if (s->pending != 0) { 444 flush_pending(strm); 445 if (strm->avail_out == 0) { 446 /* Since avail_out is 0, deflate will be called again with 447 * more output space, but possibly with both pending and 448 * avail_in equal to zero. There won't be anything to do, 449 * but this is not an error situation so make sure we 450 * return OK instead of BUF_ERROR at next call of deflate: 451 */ 452 s->last_flush = -1; 453 return Z_OK; 454 } 455 456 /* Make sure there is something to do and avoid duplicate consecutive 457 * flushes. For repeated and useless calls with Z_FINISH, we keep 458 * returning Z_STREAM_END instead of Z_BUFF_ERROR. 459 */ 460 } else if (strm->avail_in == 0 && flush <= old_flush && 461 flush != Z_FINISH) { 462 return Z_BUF_ERROR; 463 } 464 465 /* User must not provide more input after the first FINISH: */ 466 if (s->status == FINISH_STATE && strm->avail_in != 0) { 467 return Z_BUF_ERROR; 468 } 469 470 /* Start a new block or continue the current one. 471 */ 472 if (strm->avail_in != 0 || s->lookahead != 0 || 473 (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) { 474 block_state bstate; 475 476 bstate = (*(configuration_table[s->level].func))(s, flush); 477 478 if (bstate == finish_started || bstate == finish_done) { 479 s->status = FINISH_STATE; 480 } 481 if (bstate == need_more || bstate == finish_started) { 482 if (strm->avail_out == 0) { 483 s->last_flush = -1; /* avoid BUF_ERROR next call, see above */ 484 } 485 return Z_OK; 486 /* If flush != Z_NO_FLUSH && avail_out == 0, the next call 487 * of deflate should use the same flush parameter to make sure 488 * that the flush is complete. So we don't have to output an 489 * empty block here, this will be done at next call. This also 490 * ensures that for a very small output buffer, we emit at most 491 * one empty block. 492 */ 493 } 494 if (bstate == block_done) { 495 if (flush == Z_PARTIAL_FLUSH) { 496 zlib_tr_align(s); 497 } else if (flush == Z_PACKET_FLUSH) { 498 /* Output just the 3-bit `stored' block type value, 499 but not a zero length. */ 500 zlib_tr_stored_type_only(s); 501 } else { /* FULL_FLUSH or SYNC_FLUSH */ 502 zlib_tr_stored_block(s, (char*)0, 0L, 0); 503 /* For a full flush, this empty block will be recognized 504 * as a special marker by inflate_sync(). 505 */ 506 if (flush == Z_FULL_FLUSH) { 507 CLEAR_HASH(s); /* forget history */ 508 } 509 } 510 flush_pending(strm); 511 if (strm->avail_out == 0) { 512 s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */ 513 return Z_OK; 514 } 515 } 516 } 517 Assert(strm->avail_out > 0, "bug2"); 518 519 if (flush != Z_FINISH) return Z_OK; 520 if (s->noheader) return Z_STREAM_END; 521 522 /* Write the zlib trailer (adler32) */ 523 putShortMSB(s, (uInt)(strm->adler >> 16)); 524 putShortMSB(s, (uInt)(strm->adler & 0xffff)); 525 flush_pending(strm); 526 /* If avail_out is zero, the application will call deflate again 527 * to flush the rest. 528 */ 529 s->noheader = -1; /* write the trailer only once! */ 530 return s->pending != 0 ? Z_OK : Z_STREAM_END; 531 } 532 533 /* ========================================================================= */ 534 int zlib_deflateEnd( 535 z_streamp strm 536 ) 537 { 538 int status; 539 deflate_state *s; 540 541 if (strm == NULL || strm->state == NULL) return Z_STREAM_ERROR; 542 s = (deflate_state *) strm->state; 543 544 status = s->status; 545 if (status != INIT_STATE && status != BUSY_STATE && 546 status != FINISH_STATE) { 547 return Z_STREAM_ERROR; 548 } 549 550 strm->state = NULL; 551 552 return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK; 553 } 554 555 /* ========================================================================= 556 * Copy the source state to the destination state. 557 */ 558 #if 0 559 int zlib_deflateCopy ( 560 z_streamp dest, 561 z_streamp source 562 ) 563 { 564 #ifdef MAXSEG_64K 565 return Z_STREAM_ERROR; 566 #else 567 deflate_state *ds; 568 deflate_state *ss; 569 ush *overlay; 570 deflate_workspace *mem; 571 572 573 if (source == NULL || dest == NULL || source->state == NULL) { 574 return Z_STREAM_ERROR; 575 } 576 577 ss = (deflate_state *) source->state; 578 579 *dest = *source; 580 581 mem = (deflate_workspace *) dest->workspace; 582 583 ds = &(mem->deflate_memory); 584 585 dest->state = (struct internal_state *) ds; 586 *ds = *ss; 587 ds->strm = dest; 588 589 ds->window = (Byte *) mem->window_memory; 590 ds->prev = (Pos *) mem->prev_memory; 591 ds->head = (Pos *) mem->head_memory; 592 overlay = (ush *) mem->overlay_memory; 593 ds->pending_buf = (uch *) overlay; 594 595 memcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte)); 596 memcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos)); 597 memcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos)); 598 memcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size); 599 600 ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf); 601 ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush); 602 ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize; 603 604 ds->l_desc.dyn_tree = ds->dyn_ltree; 605 ds->d_desc.dyn_tree = ds->dyn_dtree; 606 ds->bl_desc.dyn_tree = ds->bl_tree; 607 608 return Z_OK; 609 #endif 610 } 611 #endif /* 0 */ 612 613 /* =========================================================================== 614 * Read a new buffer from the current input stream, update the adler32 615 * and total number of bytes read. All deflate() input goes through 616 * this function so some applications may wish to modify it to avoid 617 * allocating a large strm->next_in buffer and copying from it. 618 * (See also flush_pending()). 619 */ 620 static int read_buf( 621 z_streamp strm, 622 Byte *buf, 623 unsigned size 624 ) 625 { 626 unsigned len = strm->avail_in; 627 628 if (len > size) len = size; 629 if (len == 0) return 0; 630 631 strm->avail_in -= len; 632 633 if (!((deflate_state *)(strm->state))->noheader) { 634 strm->adler = zlib_adler32(strm->adler, strm->next_in, len); 635 } 636 memcpy(buf, strm->next_in, len); 637 strm->next_in += len; 638 strm->total_in += len; 639 640 return (int)len; 641 } 642 643 /* =========================================================================== 644 * Initialize the "longest match" routines for a new zlib stream 645 */ 646 static void lm_init( 647 deflate_state *s 648 ) 649 { 650 s->window_size = (ulg)2L*s->w_size; 651 652 CLEAR_HASH(s); 653 654 /* Set the default configuration parameters: 655 */ 656 s->max_lazy_match = configuration_table[s->level].max_lazy; 657 s->good_match = configuration_table[s->level].good_length; 658 s->nice_match = configuration_table[s->level].nice_length; 659 s->max_chain_length = configuration_table[s->level].max_chain; 660 661 s->strstart = 0; 662 s->block_start = 0L; 663 s->lookahead = 0; 664 s->match_length = s->prev_length = MIN_MATCH-1; 665 s->match_available = 0; 666 s->ins_h = 0; 667 } 668 669 /* =========================================================================== 670 * Set match_start to the longest match starting at the given string and 671 * return its length. Matches shorter or equal to prev_length are discarded, 672 * in which case the result is equal to prev_length and match_start is 673 * garbage. 674 * IN assertions: cur_match is the head of the hash chain for the current 675 * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1 676 * OUT assertion: the match length is not greater than s->lookahead. 677 */ 678 /* For 80x86 and 680x0, an optimized version will be provided in match.asm or 679 * match.S. The code will be functionally equivalent. 680 */ 681 static uInt longest_match( 682 deflate_state *s, 683 IPos cur_match /* current match */ 684 ) 685 { 686 unsigned chain_length = s->max_chain_length;/* max hash chain length */ 687 register Byte *scan = s->window + s->strstart; /* current string */ 688 register Byte *match; /* matched string */ 689 register int len; /* length of current match */ 690 int best_len = s->prev_length; /* best match length so far */ 691 int nice_match = s->nice_match; /* stop if match long enough */ 692 IPos limit = s->strstart > (IPos)MAX_DIST(s) ? 693 s->strstart - (IPos)MAX_DIST(s) : NIL; 694 /* Stop when cur_match becomes <= limit. To simplify the code, 695 * we prevent matches with the string of window index 0. 696 */ 697 Pos *prev = s->prev; 698 uInt wmask = s->w_mask; 699 700 #ifdef UNALIGNED_OK 701 /* Compare two bytes at a time. Note: this is not always beneficial. 702 * Try with and without -DUNALIGNED_OK to check. 703 */ 704 register Byte *strend = s->window + s->strstart + MAX_MATCH - 1; 705 register ush scan_start = *(ush*)scan; 706 register ush scan_end = *(ush*)(scan+best_len-1); 707 #else 708 register Byte *strend = s->window + s->strstart + MAX_MATCH; 709 register Byte scan_end1 = scan[best_len-1]; 710 register Byte scan_end = scan[best_len]; 711 #endif 712 713 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16. 714 * It is easy to get rid of this optimization if necessary. 715 */ 716 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever"); 717 718 /* Do not waste too much time if we already have a good match: */ 719 if (s->prev_length >= s->good_match) { 720 chain_length >>= 2; 721 } 722 /* Do not look for matches beyond the end of the input. This is necessary 723 * to make deflate deterministic. 724 */ 725 if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead; 726 727 Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead"); 728 729 do { 730 Assert(cur_match < s->strstart, "no future"); 731 match = s->window + cur_match; 732 733 /* Skip to next match if the match length cannot increase 734 * or if the match length is less than 2: 735 */ 736 #if (defined(UNALIGNED_OK) && MAX_MATCH == 258) 737 /* This code assumes sizeof(unsigned short) == 2. Do not use 738 * UNALIGNED_OK if your compiler uses a different size. 739 */ 740 if (*(ush*)(match+best_len-1) != scan_end || 741 *(ush*)match != scan_start) continue; 742 743 /* It is not necessary to compare scan[2] and match[2] since they are 744 * always equal when the other bytes match, given that the hash keys 745 * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at 746 * strstart+3, +5, ... up to strstart+257. We check for insufficient 747 * lookahead only every 4th comparison; the 128th check will be made 748 * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is 749 * necessary to put more guard bytes at the end of the window, or 750 * to check more often for insufficient lookahead. 751 */ 752 Assert(scan[2] == match[2], "scan[2]?"); 753 scan++, match++; 754 do { 755 } while (*(ush*)(scan+=2) == *(ush*)(match+=2) && 756 *(ush*)(scan+=2) == *(ush*)(match+=2) && 757 *(ush*)(scan+=2) == *(ush*)(match+=2) && 758 *(ush*)(scan+=2) == *(ush*)(match+=2) && 759 scan < strend); 760 /* The funny "do {}" generates better code on most compilers */ 761 762 /* Here, scan <= window+strstart+257 */ 763 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan"); 764 if (*scan == *match) scan++; 765 766 len = (MAX_MATCH - 1) - (int)(strend-scan); 767 scan = strend - (MAX_MATCH-1); 768 769 #else /* UNALIGNED_OK */ 770 771 if (match[best_len] != scan_end || 772 match[best_len-1] != scan_end1 || 773 *match != *scan || 774 *++match != scan[1]) continue; 775 776 /* The check at best_len-1 can be removed because it will be made 777 * again later. (This heuristic is not always a win.) 778 * It is not necessary to compare scan[2] and match[2] since they 779 * are always equal when the other bytes match, given that 780 * the hash keys are equal and that HASH_BITS >= 8. 781 */ 782 scan += 2, match++; 783 Assert(*scan == *match, "match[2]?"); 784 785 /* We check for insufficient lookahead only every 8th comparison; 786 * the 256th check will be made at strstart+258. 787 */ 788 do { 789 } while (*++scan == *++match && *++scan == *++match && 790 *++scan == *++match && *++scan == *++match && 791 *++scan == *++match && *++scan == *++match && 792 *++scan == *++match && *++scan == *++match && 793 scan < strend); 794 795 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan"); 796 797 len = MAX_MATCH - (int)(strend - scan); 798 scan = strend - MAX_MATCH; 799 800 #endif /* UNALIGNED_OK */ 801 802 if (len > best_len) { 803 s->match_start = cur_match; 804 best_len = len; 805 if (len >= nice_match) break; 806 #ifdef UNALIGNED_OK 807 scan_end = *(ush*)(scan+best_len-1); 808 #else 809 scan_end1 = scan[best_len-1]; 810 scan_end = scan[best_len]; 811 #endif 812 } 813 } while ((cur_match = prev[cur_match & wmask]) > limit 814 && --chain_length != 0); 815 816 if ((uInt)best_len <= s->lookahead) return best_len; 817 return s->lookahead; 818 } 819 820 #ifdef DEBUG_ZLIB 821 /* =========================================================================== 822 * Check that the match at match_start is indeed a match. 823 */ 824 static void check_match( 825 deflate_state *s, 826 IPos start, 827 IPos match, 828 int length 829 ) 830 { 831 /* check that the match is indeed a match */ 832 if (memcmp((char *)s->window + match, 833 (char *)s->window + start, length) != EQUAL) { 834 fprintf(stderr, " start %u, match %u, length %d\n", 835 start, match, length); 836 do { 837 fprintf(stderr, "%c%c", s->window[match++], s->window[start++]); 838 } while (--length != 0); 839 z_error("invalid match"); 840 } 841 if (z_verbose > 1) { 842 fprintf(stderr,"\\[%d,%d]", start-match, length); 843 do { putc(s->window[start++], stderr); } while (--length != 0); 844 } 845 } 846 #else 847 # define check_match(s, start, match, length) 848 #endif 849 850 /* =========================================================================== 851 * Fill the window when the lookahead becomes insufficient. 852 * Updates strstart and lookahead. 853 * 854 * IN assertion: lookahead < MIN_LOOKAHEAD 855 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD 856 * At least one byte has been read, or avail_in == 0; reads are 857 * performed for at least two bytes (required for the zip translate_eol 858 * option -- not supported here). 859 */ 860 static void fill_window( 861 deflate_state *s 862 ) 863 { 864 register unsigned n, m; 865 register Pos *p; 866 unsigned more; /* Amount of free space at the end of the window. */ 867 uInt wsize = s->w_size; 868 869 do { 870 more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart); 871 872 /* Deal with !@#$% 64K limit: */ 873 if (more == 0 && s->strstart == 0 && s->lookahead == 0) { 874 more = wsize; 875 876 } else if (more == (unsigned)(-1)) { 877 /* Very unlikely, but possible on 16 bit machine if strstart == 0 878 * and lookahead == 1 (input done one byte at time) 879 */ 880 more--; 881 882 /* If the window is almost full and there is insufficient lookahead, 883 * move the upper half to the lower one to make room in the upper half. 884 */ 885 } else if (s->strstart >= wsize+MAX_DIST(s)) { 886 887 memcpy((char *)s->window, (char *)s->window+wsize, 888 (unsigned)wsize); 889 s->match_start -= wsize; 890 s->strstart -= wsize; /* we now have strstart >= MAX_DIST */ 891 s->block_start -= (long) wsize; 892 893 /* Slide the hash table (could be avoided with 32 bit values 894 at the expense of memory usage). We slide even when level == 0 895 to keep the hash table consistent if we switch back to level > 0 896 later. (Using level 0 permanently is not an optimal usage of 897 zlib, so we don't care about this pathological case.) 898 */ 899 n = s->hash_size; 900 p = &s->head[n]; 901 do { 902 m = *--p; 903 *p = (Pos)(m >= wsize ? m-wsize : NIL); 904 } while (--n); 905 906 n = wsize; 907 p = &s->prev[n]; 908 do { 909 m = *--p; 910 *p = (Pos)(m >= wsize ? m-wsize : NIL); 911 /* If n is not on any hash chain, prev[n] is garbage but 912 * its value will never be used. 913 */ 914 } while (--n); 915 more += wsize; 916 } 917 if (s->strm->avail_in == 0) return; 918 919 /* If there was no sliding: 920 * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 && 921 * more == window_size - lookahead - strstart 922 * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1) 923 * => more >= window_size - 2*WSIZE + 2 924 * In the BIG_MEM or MMAP case (not yet supported), 925 * window_size == input_size + MIN_LOOKAHEAD && 926 * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD. 927 * Otherwise, window_size == 2*WSIZE so more >= 2. 928 * If there was sliding, more >= WSIZE. So in all cases, more >= 2. 929 */ 930 Assert(more >= 2, "more < 2"); 931 932 n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more); 933 s->lookahead += n; 934 935 /* Initialize the hash value now that we have some input: */ 936 if (s->lookahead >= MIN_MATCH) { 937 s->ins_h = s->window[s->strstart]; 938 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]); 939 #if MIN_MATCH != 3 940 Call UPDATE_HASH() MIN_MATCH-3 more times 941 #endif 942 } 943 /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage, 944 * but this is not important since only literal bytes will be emitted. 945 */ 946 947 } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0); 948 } 949 950 /* =========================================================================== 951 * Flush the current block, with given end-of-file flag. 952 * IN assertion: strstart is set to the end of the current match. 953 */ 954 #define FLUSH_BLOCK_ONLY(s, eof) { \ 955 zlib_tr_flush_block(s, (s->block_start >= 0L ? \ 956 (char *)&s->window[(unsigned)s->block_start] : \ 957 NULL), \ 958 (ulg)((long)s->strstart - s->block_start), \ 959 (eof)); \ 960 s->block_start = s->strstart; \ 961 flush_pending(s->strm); \ 962 Tracev((stderr,"[FLUSH]")); \ 963 } 964 965 /* Same but force premature exit if necessary. */ 966 #define FLUSH_BLOCK(s, eof) { \ 967 FLUSH_BLOCK_ONLY(s, eof); \ 968 if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \ 969 } 970 971 /* =========================================================================== 972 * Copy without compression as much as possible from the input stream, return 973 * the current block state. 974 * This function does not insert new strings in the dictionary since 975 * uncompressible data is probably not useful. This function is used 976 * only for the level=0 compression option. 977 * NOTE: this function should be optimized to avoid extra copying from 978 * window to pending_buf. 979 */ 980 static block_state deflate_stored( 981 deflate_state *s, 982 int flush 983 ) 984 { 985 /* Stored blocks are limited to 0xffff bytes, pending_buf is limited 986 * to pending_buf_size, and each stored block has a 5 byte header: 987 */ 988 ulg max_block_size = 0xffff; 989 ulg max_start; 990 991 if (max_block_size > s->pending_buf_size - 5) { 992 max_block_size = s->pending_buf_size - 5; 993 } 994 995 /* Copy as much as possible from input to output: */ 996 for (;;) { 997 /* Fill the window as much as possible: */ 998 if (s->lookahead <= 1) { 999 1000 Assert(s->strstart < s->w_size+MAX_DIST(s) || 1001 s->block_start >= (long)s->w_size, "slide too late"); 1002 1003 fill_window(s); 1004 if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more; 1005 1006 if (s->lookahead == 0) break; /* flush the current block */ 1007 } 1008 Assert(s->block_start >= 0L, "block gone"); 1009 1010 s->strstart += s->lookahead; 1011 s->lookahead = 0; 1012 1013 /* Emit a stored block if pending_buf will be full: */ 1014 max_start = s->block_start + max_block_size; 1015 if (s->strstart == 0 || (ulg)s->strstart >= max_start) { 1016 /* strstart == 0 is possible when wraparound on 16-bit machine */ 1017 s->lookahead = (uInt)(s->strstart - max_start); 1018 s->strstart = (uInt)max_start; 1019 FLUSH_BLOCK(s, 0); 1020 } 1021 /* Flush if we may have to slide, otherwise block_start may become 1022 * negative and the data will be gone: 1023 */ 1024 if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) { 1025 FLUSH_BLOCK(s, 0); 1026 } 1027 } 1028 FLUSH_BLOCK(s, flush == Z_FINISH); 1029 return flush == Z_FINISH ? finish_done : block_done; 1030 } 1031 1032 /* =========================================================================== 1033 * Compress as much as possible from the input stream, return the current 1034 * block state. 1035 * This function does not perform lazy evaluation of matches and inserts 1036 * new strings in the dictionary only for unmatched strings or for short 1037 * matches. It is used only for the fast compression options. 1038 */ 1039 static block_state deflate_fast( 1040 deflate_state *s, 1041 int flush 1042 ) 1043 { 1044 IPos hash_head = NIL; /* head of the hash chain */ 1045 int bflush; /* set if current block must be flushed */ 1046 1047 for (;;) { 1048 /* Make sure that we always have enough lookahead, except 1049 * at the end of the input file. We need MAX_MATCH bytes 1050 * for the next match, plus MIN_MATCH bytes to insert the 1051 * string following the next match. 1052 */ 1053 if (s->lookahead < MIN_LOOKAHEAD) { 1054 fill_window(s); 1055 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) { 1056 return need_more; 1057 } 1058 if (s->lookahead == 0) break; /* flush the current block */ 1059 } 1060 1061 /* Insert the string window[strstart .. strstart+2] in the 1062 * dictionary, and set hash_head to the head of the hash chain: 1063 */ 1064 if (s->lookahead >= MIN_MATCH) { 1065 INSERT_STRING(s, s->strstart, hash_head); 1066 } 1067 1068 /* Find the longest match, discarding those <= prev_length. 1069 * At this point we have always match_length < MIN_MATCH 1070 */ 1071 if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) { 1072 /* To simplify the code, we prevent matches with the string 1073 * of window index 0 (in particular we have to avoid a match 1074 * of the string with itself at the start of the input file). 1075 */ 1076 if (s->strategy != Z_HUFFMAN_ONLY) { 1077 s->match_length = longest_match (s, hash_head); 1078 } 1079 /* longest_match() sets match_start */ 1080 } 1081 if (s->match_length >= MIN_MATCH) { 1082 check_match(s, s->strstart, s->match_start, s->match_length); 1083 1084 bflush = zlib_tr_tally(s, s->strstart - s->match_start, 1085 s->match_length - MIN_MATCH); 1086 1087 s->lookahead -= s->match_length; 1088 1089 /* Insert new strings in the hash table only if the match length 1090 * is not too large. This saves time but degrades compression. 1091 */ 1092 if (s->match_length <= s->max_insert_length && 1093 s->lookahead >= MIN_MATCH) { 1094 s->match_length--; /* string at strstart already in hash table */ 1095 do { 1096 s->strstart++; 1097 INSERT_STRING(s, s->strstart, hash_head); 1098 /* strstart never exceeds WSIZE-MAX_MATCH, so there are 1099 * always MIN_MATCH bytes ahead. 1100 */ 1101 } while (--s->match_length != 0); 1102 s->strstart++; 1103 } else { 1104 s->strstart += s->match_length; 1105 s->match_length = 0; 1106 s->ins_h = s->window[s->strstart]; 1107 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]); 1108 #if MIN_MATCH != 3 1109 Call UPDATE_HASH() MIN_MATCH-3 more times 1110 #endif 1111 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not 1112 * matter since it will be recomputed at next deflate call. 1113 */ 1114 } 1115 } else { 1116 /* No match, output a literal byte */ 1117 Tracevv((stderr,"%c", s->window[s->strstart])); 1118 bflush = zlib_tr_tally (s, 0, s->window[s->strstart]); 1119 s->lookahead--; 1120 s->strstart++; 1121 } 1122 if (bflush) FLUSH_BLOCK(s, 0); 1123 } 1124 FLUSH_BLOCK(s, flush == Z_FINISH); 1125 return flush == Z_FINISH ? finish_done : block_done; 1126 } 1127 1128 /* =========================================================================== 1129 * Same as above, but achieves better compression. We use a lazy 1130 * evaluation for matches: a match is finally adopted only if there is 1131 * no better match at the next window position. 1132 */ 1133 static block_state deflate_slow( 1134 deflate_state *s, 1135 int flush 1136 ) 1137 { 1138 IPos hash_head = NIL; /* head of hash chain */ 1139 int bflush; /* set if current block must be flushed */ 1140 1141 /* Process the input block. */ 1142 for (;;) { 1143 /* Make sure that we always have enough lookahead, except 1144 * at the end of the input file. We need MAX_MATCH bytes 1145 * for the next match, plus MIN_MATCH bytes to insert the 1146 * string following the next match. 1147 */ 1148 if (s->lookahead < MIN_LOOKAHEAD) { 1149 fill_window(s); 1150 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) { 1151 return need_more; 1152 } 1153 if (s->lookahead == 0) break; /* flush the current block */ 1154 } 1155 1156 /* Insert the string window[strstart .. strstart+2] in the 1157 * dictionary, and set hash_head to the head of the hash chain: 1158 */ 1159 if (s->lookahead >= MIN_MATCH) { 1160 INSERT_STRING(s, s->strstart, hash_head); 1161 } 1162 1163 /* Find the longest match, discarding those <= prev_length. 1164 */ 1165 s->prev_length = s->match_length, s->prev_match = s->match_start; 1166 s->match_length = MIN_MATCH-1; 1167 1168 if (hash_head != NIL && s->prev_length < s->max_lazy_match && 1169 s->strstart - hash_head <= MAX_DIST(s)) { 1170 /* To simplify the code, we prevent matches with the string 1171 * of window index 0 (in particular we have to avoid a match 1172 * of the string with itself at the start of the input file). 1173 */ 1174 if (s->strategy != Z_HUFFMAN_ONLY) { 1175 s->match_length = longest_match (s, hash_head); 1176 } 1177 /* longest_match() sets match_start */ 1178 1179 if (s->match_length <= 5 && (s->strategy == Z_FILTERED || 1180 (s->match_length == MIN_MATCH && 1181 s->strstart - s->match_start > TOO_FAR))) { 1182 1183 /* If prev_match is also MIN_MATCH, match_start is garbage 1184 * but we will ignore the current match anyway. 1185 */ 1186 s->match_length = MIN_MATCH-1; 1187 } 1188 } 1189 /* If there was a match at the previous step and the current 1190 * match is not better, output the previous match: 1191 */ 1192 if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) { 1193 uInt max_insert = s->strstart + s->lookahead - MIN_MATCH; 1194 /* Do not insert strings in hash table beyond this. */ 1195 1196 check_match(s, s->strstart-1, s->prev_match, s->prev_length); 1197 1198 bflush = zlib_tr_tally(s, s->strstart -1 - s->prev_match, 1199 s->prev_length - MIN_MATCH); 1200 1201 /* Insert in hash table all strings up to the end of the match. 1202 * strstart-1 and strstart are already inserted. If there is not 1203 * enough lookahead, the last two strings are not inserted in 1204 * the hash table. 1205 */ 1206 s->lookahead -= s->prev_length-1; 1207 s->prev_length -= 2; 1208 do { 1209 if (++s->strstart <= max_insert) { 1210 INSERT_STRING(s, s->strstart, hash_head); 1211 } 1212 } while (--s->prev_length != 0); 1213 s->match_available = 0; 1214 s->match_length = MIN_MATCH-1; 1215 s->strstart++; 1216 1217 if (bflush) FLUSH_BLOCK(s, 0); 1218 1219 } else if (s->match_available) { 1220 /* If there was no match at the previous position, output a 1221 * single literal. If there was a match but the current match 1222 * is longer, truncate the previous match to a single literal. 1223 */ 1224 Tracevv((stderr,"%c", s->window[s->strstart-1])); 1225 if (zlib_tr_tally (s, 0, s->window[s->strstart-1])) { 1226 FLUSH_BLOCK_ONLY(s, 0); 1227 } 1228 s->strstart++; 1229 s->lookahead--; 1230 if (s->strm->avail_out == 0) return need_more; 1231 } else { 1232 /* There is no previous match to compare with, wait for 1233 * the next step to decide. 1234 */ 1235 s->match_available = 1; 1236 s->strstart++; 1237 s->lookahead--; 1238 } 1239 } 1240 Assert (flush != Z_NO_FLUSH, "no flush?"); 1241 if (s->match_available) { 1242 Tracevv((stderr,"%c", s->window[s->strstart-1])); 1243 zlib_tr_tally (s, 0, s->window[s->strstart-1]); 1244 s->match_available = 0; 1245 } 1246 FLUSH_BLOCK(s, flush == Z_FINISH); 1247 return flush == Z_FINISH ? finish_done : block_done; 1248 } 1249 1250 int zlib_deflate_workspacesize(void) 1251 { 1252 return sizeof(deflate_workspace); 1253 } 1254