1/* deflate.c -- compress data using the deflation algorithm 2 * Copyright (C) 1995-2002 Jean-loup Gailly. 3 * For conditions of distribution and use, see copyright notice in zlib.h 4 */ 5 6/* 7 * ALGORITHM 8 * 9 * The "deflation" process depends on being able to identify portions 10 * of the input text which are identical to earlier input (within a 11 * sliding window trailing behind the input currently being processed). 12 * 13 * The most straightforward technique turns out to be the fastest for 14 * most input files: try all possible matches and select the longest. 15 * The key feature of this algorithm is that insertions into the string 16 * dictionary are very simple and thus fast, and deletions are avoided 17 * completely. Insertions are performed at each input character, whereas 18 * string matches are performed only when the previous match ends. So it 19 * is preferable to spend more time in matches to allow very fast string 20 * insertions and avoid deletions. The matching algorithm for small 21 * strings is inspired from that of Rabin & Karp. A brute force approach 22 * is used to find longer strings when a small match has been found. 23 * A similar algorithm is used in comic (by Jan-Mark Wams) and freeze 24 * (by Leonid Broukhis). 25 * A previous version of this file used a more sophisticated algorithm 26 * (by Fiala and Greene) which is guaranteed to run in linear amortized 27 * time, but has a larger average cost, uses more memory and is patented. 28 * However the F&G algorithm may be faster for some highly redundant 29 * files if the parameter max_chain_length (described below) is too large. 30 * 31 * ACKNOWLEDGEMENTS 32 * 33 * The idea of lazy evaluation of matches is due to Jan-Mark Wams, and 34 * I found it in 'freeze' written by Leonid Broukhis. 35 * Thanks to many people for bug reports and testing. 36 * 37 * REFERENCES 38 * 39 * Deutsch, L.P.,"DEFLATE Compressed Data Format Specification". 40 * Available in ftp://ds.internic.net/rfc/rfc1951.txt 41 * 42 * A description of the Rabin and Karp algorithm is given in the book 43 * "Algorithms" by R. Sedgewick, Addison-Wesley, p252. 44 * 45 * Fiala,E.R., and Greene,D.H. 46 * Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595 47 * 48 */ 49 50/* $Id: deflate.c 14574 2005-10-29 16:27:43Z bonefish $ */ 51/* @(#) $Id: deflate.c 14574 2005-10-29 16:27:43Z bonefish $ */ 52 53#include "deflate.h" 54 55const char deflate_copyright[] = 56 " deflate 1.1.4 Copyright 1995-2002 Jean-loup Gailly "; 57/* 58 If you use the zlib library in a product, an acknowledgment is welcome 59 in the documentation of your product. If for some reason you cannot 60 include such an acknowledgment, I would appreciate that you keep this 61 copyright string in the executable of your product. 62 */ 63 64/* =========================================================================== 65 * Function prototypes. 66 */ 67typedef enum { 68 need_more, /* block not completed, need more input or more output */ 69 block_done, /* block flush performed */ 70 finish_started, /* finish started, need only more output at next deflate */ 71 finish_done /* finish done, accept no more input or output */ 72} block_state; 73 74typedef block_state (*compress_func) OF((deflate_state *s, int flush)); 75/* Compression function. Returns the block state after the call. */ 76 77local void fill_window OF((deflate_state *s)); 78local block_state deflate_stored OF((deflate_state *s, int flush)); 79local block_state deflate_fast OF((deflate_state *s, int flush)); 80local block_state deflate_slow OF((deflate_state *s, int flush)); 81local void lm_init OF((deflate_state *s)); 82local void putShortMSB OF((deflate_state *s, uInt b)); 83local void flush_pending OF((z_streamp strm)); 84local int read_buf OF((z_streamp strm, Bytef *buf, unsigned size)); 85#ifdef ASMV 86 void match_init OF((void)); /* asm code initialization */ 87 uInt longest_match OF((deflate_state *s, IPos cur_match)); 88#else 89local uInt longest_match OF((deflate_state *s, IPos cur_match)); 90#endif 91 92#ifdef DEBUG 93local void check_match OF((deflate_state *s, IPos start, IPos match, 94 int length)); 95#endif 96 97/* =========================================================================== 98 * Local data 99 */ 100 101#define NIL 0 102/* Tail of hash chains */ 103 104#ifndef TOO_FAR 105# define TOO_FAR 4096 106#endif 107/* Matches of length 3 are discarded if their distance exceeds TOO_FAR */ 108 109#define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1) 110/* Minimum amount of lookahead, except at the end of the input file. 111 * See deflate.c for comments about the MIN_MATCH+1. 112 */ 113 114/* Values for max_lazy_match, good_match and max_chain_length, depending on 115 * the desired pack level (0..9). The values given below have been tuned to 116 * exclude worst case performance for pathological files. Better values may be 117 * found for specific files. 118 */ 119typedef struct config_s { 120 ush good_length; /* reduce lazy search above this match length */ 121 ush max_lazy; /* do not perform lazy search above this match length */ 122 ush nice_length; /* quit search above this match length */ 123 ush max_chain; 124 compress_func func; 125} config; 126 127local const config configuration_table[10] = { 128/* good lazy nice chain */ 129/* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */ 130/* 1 */ {4, 4, 8, 4, deflate_fast}, /* maximum speed, no lazy matches */ 131/* 2 */ {4, 5, 16, 8, deflate_fast}, 132/* 3 */ {4, 6, 32, 32, deflate_fast}, 133 134/* 4 */ {4, 4, 16, 16, deflate_slow}, /* lazy matches */ 135/* 5 */ {8, 16, 32, 32, deflate_slow}, 136/* 6 */ {8, 16, 128, 128, deflate_slow}, 137/* 7 */ {8, 32, 128, 256, deflate_slow}, 138/* 8 */ {32, 128, 258, 1024, deflate_slow}, 139/* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* maximum compression */ 140 141/* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4 142 * For deflate_fast() (levels <= 3) good is ignored and lazy has a different 143 * meaning. 144 */ 145 146#define EQUAL 0 147/* result of memcmp for equal strings */ 148 149/* PDFlib GmbH: conflicts with Visual Studio.NET 150struct static_tree_desc_s {int dummy;}; */ /* for buggy compilers */ 151 152/* =========================================================================== 153 * Update a hash value with the given input byte 154 * IN assertion: all calls to to UPDATE_HASH are made with consecutive 155 * input characters, so that a running hash key can be computed from the 156 * previous key instead of complete recalculation each time. 157 */ 158#define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask) 159 160 161/* =========================================================================== 162 * Insert string str in the dictionary and set match_head to the previous head 163 * of the hash chain (the most recent string with same hash key). Return 164 * the previous length of the hash chain. 165 * If this file is compiled with -DFASTEST, the compression level is forced 166 * to 1, and no hash chains are maintained. 167 * IN assertion: all calls to to INSERT_STRING are made with consecutive 168 * input characters and the first MIN_MATCH bytes of str are valid 169 * (except for the last MIN_MATCH-1 bytes of the input file). 170 */ 171#ifdef FASTEST 172#define INSERT_STRING(s, str, match_head) \ 173 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \ 174 match_head = s->head[s->ins_h], \ 175 s->head[s->ins_h] = (Pos)(str)) 176#else 177#define INSERT_STRING(s, str, match_head) \ 178 (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \ 179 s->prev[(str) & s->w_mask] = match_head = s->head[s->ins_h], \ 180 s->head[s->ins_h] = (Pos)(str)) 181#endif 182 183/* =========================================================================== 184 * Initialize the hash table (avoiding 64K overflow for 16 bit systems). 185 * prev[] will be initialized on the fly. 186 */ 187#define CLEAR_HASH(s) \ 188 s->head[s->hash_size-1] = NIL; \ 189 zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head)); 190 191/* ========================================================================= */ 192int ZEXPORT deflateInit_( 193 z_streamp strm, 194 int level, 195 const char *version, 196 int stream_size) 197{ 198 return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL, 199 Z_DEFAULT_STRATEGY, version, stream_size); 200 /* To do: ignore strm->next_in if we use it as window */ 201} 202 203/* ========================================================================= */ 204int ZEXPORT deflateInit2_( 205 z_streamp strm, 206 int level, 207 int method, 208 int windowBits, 209 int memLevel, 210 int strategy, 211 const char *version, 212 int stream_size) 213{ 214 deflate_state *s; 215 int noheader = 0; 216 static const char* my_version = ZLIB_VERSION; 217 218 ushf *overlay; 219 /* We overlay pending_buf and d_buf+l_buf. This works since the average 220 * output size for (length,distance) codes is <= 24 bits. 221 */ 222 223 if (version == Z_NULL || version[0] != my_version[0] || 224 stream_size != sizeof(z_stream)) { 225 return Z_VERSION_ERROR; 226 } 227 if (strm == Z_NULL) return Z_STREAM_ERROR; 228 229 strm->msg = Z_NULL; 230 if (strm->zalloc == Z_NULL) { 231 strm->zalloc = zcalloc; 232 strm->opaque = (voidpf)0; 233 } 234 if (strm->zfree == Z_NULL) strm->zfree = zcfree; 235 236 if (level == Z_DEFAULT_COMPRESSION) level = 6; 237#ifdef FASTEST 238 level = 1; 239#endif 240 241 if (windowBits < 0) { /* undocumented feature: suppress zlib header */ 242 noheader = 1; 243 windowBits = -windowBits; 244 } 245 if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED || 246 windowBits < 9 || windowBits > 15 || level < 0 || level > 9 || 247 strategy < 0 || strategy > Z_HUFFMAN_ONLY) { 248 return Z_STREAM_ERROR; 249 } 250 s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state)); 251 if (s == Z_NULL) return Z_MEM_ERROR; 252 strm->state = (struct internal_state FAR *)s; 253 s->data_type = Z_UNKNOWN; 254 s->strm = strm; 255 256 s->noheader = noheader; 257 s->w_bits = windowBits; 258 s->w_size = 1 << s->w_bits; 259 s->w_mask = s->w_size - 1; 260 261 s->hash_bits = memLevel + 7; 262 s->hash_size = 1 << s->hash_bits; 263 s->hash_mask = s->hash_size - 1; 264 s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH); 265 266 s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte)); 267 /* we don't use calloc -> to satisfy purify 268 * at least here memset is needed */ 269 memset((void *)s->window, 0, (size_t) s->w_size * 2*sizeof(Byte)); 270 271 s->prev = (Posf *) ZALLOC(strm, s->w_size, sizeof(Pos)); 272 s->head = (Posf *) ZALLOC(strm, s->hash_size, sizeof(Pos)); 273 274 s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */ 275 276 overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2); 277 s->pending_buf = (uchf *) overlay; 278 s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L); 279 280 if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL || 281 s->pending_buf == Z_NULL) { 282 strm->msg = (char*)ERR_MSG(Z_MEM_ERROR); 283 deflateEnd (strm); 284 return Z_MEM_ERROR; 285 } 286 s->d_buf = overlay + s->lit_bufsize/sizeof(ush); 287 s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize; 288 289 s->level = level; 290 s->strategy = strategy; 291 s->method = (Byte)method; 292 293 return deflateReset(strm); 294} 295 296/* ========================================================================= */ 297int ZEXPORT deflateSetDictionary ( 298 z_streamp strm, 299 const Bytef *dictionary, 300 uInt dictLength) 301{ 302 deflate_state *s; 303 uInt length = dictLength; 304 uInt n; 305 IPos hash_head = 0; 306 307 if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL || 308 strm->state->status != INIT_STATE) return Z_STREAM_ERROR; 309 310 s = strm->state; 311 strm->adler = adler32(strm->adler, dictionary, dictLength); 312 313 if (length < MIN_MATCH) return Z_OK; 314 if (length > MAX_DIST(s)) { 315 length = MAX_DIST(s); 316#ifndef USE_DICT_HEAD 317 dictionary += dictLength - length; /* use the tail of the dictionary */ 318#endif 319 } 320 zmemcpy(s->window, dictionary, length); 321 s->strstart = length; 322 s->block_start = (long)length; 323 324 /* Insert all strings in the hash table (except for the last two bytes). 325 * s->lookahead stays null, so s->ins_h will be recomputed at the next 326 * call of fill_window. 327 */ 328 s->ins_h = s->window[0]; 329 UPDATE_HASH(s, s->ins_h, s->window[1]); 330 for (n = 0; n <= length - MIN_MATCH; n++) { 331 INSERT_STRING(s, n, hash_head); 332 } 333 if (hash_head) hash_head = 0; /* to make compiler happy */ 334 return Z_OK; 335} 336 337/* ========================================================================= */ 338int ZEXPORT deflateReset ( 339 z_streamp strm) 340{ 341 deflate_state *s; 342 343 if (strm == Z_NULL || strm->state == Z_NULL || 344 strm->zalloc == Z_NULL || strm->zfree == Z_NULL) return Z_STREAM_ERROR; 345 346 strm->total_in = strm->total_out = 0; 347 strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */ 348 strm->data_type = Z_UNKNOWN; 349 350 s = (deflate_state *)strm->state; 351 s->pending = 0; 352 s->pending_out = s->pending_buf; 353 354 if (s->noheader < 0) { 355 s->noheader = 0; /* was set to -1 by deflate(..., Z_FINISH); */ 356 } 357 s->status = s->noheader ? BUSY_STATE : INIT_STATE; 358 strm->adler = 1; 359 s->last_flush = Z_NO_FLUSH; 360 361 _tr_init(s); 362 lm_init(s); 363 364 return Z_OK; 365} 366 367/* ========================================================================= */ 368int ZEXPORT deflateParams( 369 z_streamp strm, 370 int level, 371 int strategy) 372{ 373 deflate_state *s; 374 compress_func func; 375 int err = Z_OK; 376 377 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR; 378 s = strm->state; 379 380 if (level == Z_DEFAULT_COMPRESSION) { 381 level = 6; 382 } 383 if (level < 0 || level > 9 || strategy < 0 || strategy > Z_HUFFMAN_ONLY) { 384 return Z_STREAM_ERROR; 385 } 386 func = configuration_table[s->level].func; 387 388 if (func != configuration_table[level].func && strm->total_in != 0) { 389 /* Flush the last buffer: */ 390 err = deflate(strm, Z_PARTIAL_FLUSH); 391 } 392 if (s->level != level) { 393 s->level = level; 394 s->max_lazy_match = configuration_table[level].max_lazy; 395 s->good_match = configuration_table[level].good_length; 396 s->nice_match = configuration_table[level].nice_length; 397 s->max_chain_length = configuration_table[level].max_chain; 398 } 399 s->strategy = strategy; 400 return err; 401} 402 403/* ========================================================================= 404 * Put a short in the pending buffer. The 16-bit value is put in MSB order. 405 * IN assertion: the stream state is correct and there is enough room in 406 * pending_buf. 407 */ 408local void putShortMSB ( 409 deflate_state *s, 410 uInt b) 411{ 412 put_byte(s, (Byte)(b >> 8)); 413 put_byte(s, (Byte)(b & 0xff)); 414} 415 416/* ========================================================================= 417 * Flush as much pending output as possible. All deflate() output goes 418 * through this function so some applications may wish to modify it 419 * to avoid allocating a large strm->next_out buffer and copying into it. 420 * (See also read_buf()). 421 */ 422local void flush_pending( 423 z_streamp strm) 424{ 425 unsigned len = strm->state->pending; 426 427 if (len > strm->avail_out) len = strm->avail_out; 428 if (len == 0) return; 429 430 zmemcpy(strm->next_out, strm->state->pending_out, len); 431 strm->next_out += len; 432 strm->state->pending_out += len; 433 strm->total_out += len; 434 strm->avail_out -= len; 435 strm->state->pending -= len; 436 if (strm->state->pending == 0) { 437 strm->state->pending_out = strm->state->pending_buf; 438 } 439} 440 441/* ========================================================================= */ 442int ZEXPORT deflate ( 443 z_streamp strm, 444 int flush) 445{ 446 int old_flush; /* value of flush param for previous deflate call */ 447 deflate_state *s; 448 449 if (strm == Z_NULL || strm->state == Z_NULL || 450 flush > Z_FINISH || flush < 0) { 451 return Z_STREAM_ERROR; 452 } 453 s = strm->state; 454 455 if (strm->next_out == Z_NULL || 456 (strm->next_in == Z_NULL && strm->avail_in != 0) || 457 (s->status == FINISH_STATE && flush != Z_FINISH)) { 458 ERR_RETURN(strm, Z_STREAM_ERROR); 459 } 460 if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR); 461 462 s->strm = strm; /* just in case */ 463 old_flush = s->last_flush; 464 s->last_flush = flush; 465 466 /* Write the zlib header */ 467 if (s->status == INIT_STATE) { 468 469 uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8; 470 uInt level_flags = (s->level-1) >> 1; 471 472 if (level_flags > 3) level_flags = 3; 473 header |= (level_flags << 6); 474 if (s->strstart != 0) header |= PRESET_DICT; 475 header += 31 - (header % 31); 476 477 s->status = BUSY_STATE; 478 putShortMSB(s, header); 479 480 /* Save the adler32 of the preset dictionary: */ 481 if (s->strstart != 0) { 482 putShortMSB(s, (uInt)(strm->adler >> 16)); 483 putShortMSB(s, (uInt)(strm->adler & 0xffff)); 484 } 485 strm->adler = 1L; 486 } 487 488 /* Flush as much pending output as possible */ 489 if (s->pending != 0) { 490 flush_pending(strm); 491 if (strm->avail_out == 0) { 492 /* Since avail_out is 0, deflate will be called again with 493 * more output space, but possibly with both pending and 494 * avail_in equal to zero. There won't be anything to do, 495 * but this is not an error situation so make sure we 496 * return OK instead of BUF_ERROR at next call of deflate: 497 */ 498 s->last_flush = -1; 499 return Z_OK; 500 } 501 502 /* Make sure there is something to do and avoid duplicate consecutive 503 * flushes. For repeated and useless calls with Z_FINISH, we keep 504 * returning Z_STREAM_END instead of Z_BUFF_ERROR. 505 */ 506 } else if (strm->avail_in == 0 && flush <= old_flush && 507 flush != Z_FINISH) { 508 ERR_RETURN(strm, Z_BUF_ERROR); 509 } 510 511 /* User must not provide more input after the first FINISH: */ 512 if (s->status == FINISH_STATE && strm->avail_in != 0) { 513 ERR_RETURN(strm, Z_BUF_ERROR); 514 } 515 516 /* Start a new block or continue the current one. 517 */ 518 if (strm->avail_in != 0 || s->lookahead != 0 || 519 (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) { 520 block_state bstate; 521 522 bstate = (*(configuration_table[s->level].func))(s, flush); 523 524 if (bstate == finish_started || bstate == finish_done) { 525 s->status = FINISH_STATE; 526 } 527 if (bstate == need_more || bstate == finish_started) { 528 if (strm->avail_out == 0) { 529 s->last_flush = -1; /* avoid BUF_ERROR next call, see above */ 530 } 531 return Z_OK; 532 /* If flush != Z_NO_FLUSH && avail_out == 0, the next call 533 * of deflate should use the same flush parameter to make sure 534 * that the flush is complete. So we don't have to output an 535 * empty block here, this will be done at next call. This also 536 * ensures that for a very small output buffer, we emit at most 537 * one empty block. 538 */ 539 } 540 if (bstate == block_done) { 541 if (flush == Z_PARTIAL_FLUSH) { 542 _tr_align(s); 543 } else { /* FULL_FLUSH or SYNC_FLUSH */ 544 _tr_stored_block(s, (char*)0, 0L, 0); 545 /* For a full flush, this empty block will be recognized 546 * as a special marker by inflate_sync(). 547 */ 548 if (flush == Z_FULL_FLUSH) { 549 CLEAR_HASH(s); /* forget history */ 550 } 551 } 552 flush_pending(strm); 553 if (strm->avail_out == 0) { 554 s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */ 555 return Z_OK; 556 } 557 } 558 } 559 Assert(strm->avail_out > 0, "bug2"); 560 561 if (flush != Z_FINISH) return Z_OK; 562 if (s->noheader) return Z_STREAM_END; 563 564 /* Write the zlib trailer (adler32) */ 565 putShortMSB(s, (uInt)(strm->adler >> 16)); 566 putShortMSB(s, (uInt)(strm->adler & 0xffff)); 567 flush_pending(strm); 568 /* If avail_out is zero, the application will call deflate again 569 * to flush the rest. 570 */ 571 s->noheader = -1; /* write the trailer only once! */ 572 return s->pending != 0 ? Z_OK : Z_STREAM_END; 573} 574 575/* ========================================================================= */ 576int ZEXPORT deflateEnd ( 577 z_streamp strm) 578{ 579 int status; 580 581 if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR; 582 583 status = strm->state->status; 584 if (status != INIT_STATE && status != BUSY_STATE && 585 status != FINISH_STATE) { 586 return Z_STREAM_ERROR; 587 } 588 589 /* Deallocate in reverse order of allocations: */ 590 TRY_FREE(strm, strm->state->pending_buf); 591 TRY_FREE(strm, strm->state->head); 592 TRY_FREE(strm, strm->state->prev); 593 TRY_FREE(strm, strm->state->window); 594 595 ZFREE(strm, strm->state); 596 strm->state = Z_NULL; 597 598 return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK; 599} 600 601/* ========================================================================= 602 * Copy the source state to the destination state. 603 * To simplify the source, this is not supported for 16-bit MSDOS (which 604 * doesn't have enough memory anyway to duplicate compression states). 605 */ 606int ZEXPORT deflateCopy ( 607 z_streamp dest, 608 z_streamp source) 609{ 610#ifdef MAXSEG_64K 611 return Z_STREAM_ERROR; 612#else 613 deflate_state *ds; 614 deflate_state *ss; 615 ushf *overlay; 616 617 618 if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) { 619 return Z_STREAM_ERROR; 620 } 621 622 ss = source->state; 623 624 *dest = *source; 625 626 ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state)); 627 if (ds == Z_NULL) return Z_MEM_ERROR; 628 dest->state = (struct internal_state FAR *) ds; 629 *ds = *ss; 630 ds->strm = dest; 631 632 ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte)); 633 ds->prev = (Posf *) ZALLOC(dest, ds->w_size, sizeof(Pos)); 634 ds->head = (Posf *) ZALLOC(dest, ds->hash_size, sizeof(Pos)); 635 overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2); 636 ds->pending_buf = (uchf *) overlay; 637 638 if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL || 639 ds->pending_buf == Z_NULL) { 640 deflateEnd (dest); 641 return Z_MEM_ERROR; 642 } 643 /* following zmemcpy do not work for 16-bit MSDOS */ 644 zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte)); 645 zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos)); 646 zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos)); 647 zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size); 648 649 ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf); 650 ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush); 651 ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize; 652 653 ds->l_desc.dyn_tree = ds->dyn_ltree; 654 ds->d_desc.dyn_tree = ds->dyn_dtree; 655 ds->bl_desc.dyn_tree = ds->bl_tree; 656 657 return Z_OK; 658#endif 659} 660 661/* =========================================================================== 662 * Read a new buffer from the current input stream, update the adler32 663 * and total number of bytes read. All deflate() input goes through 664 * this function so some applications may wish to modify it to avoid 665 * allocating a large strm->next_in buffer and copying from it. 666 * (See also flush_pending()). 667 */ 668local int read_buf( 669 z_streamp strm, 670 Bytef *buf, 671 unsigned size) 672{ 673 unsigned len = strm->avail_in; 674 675 if (len > size) len = size; 676 if (len == 0) return 0; 677 678 strm->avail_in -= len; 679 680 if (!strm->state->noheader) { 681 strm->adler = adler32(strm->adler, strm->next_in, len); 682 } 683 zmemcpy(buf, strm->next_in, len); 684 strm->next_in += len; 685 strm->total_in += len; 686 687 return (int)len; 688} 689 690/* =========================================================================== 691 * Initialize the "longest match" routines for a new zlib stream 692 */ 693local void lm_init ( 694 deflate_state *s) 695{ 696 s->window_size = (ulg)2L*s->w_size; 697 698 CLEAR_HASH(s); 699 700 /* Set the default configuration parameters: 701 */ 702 s->max_lazy_match = configuration_table[s->level].max_lazy; 703 s->good_match = configuration_table[s->level].good_length; 704 s->nice_match = configuration_table[s->level].nice_length; 705 s->max_chain_length = configuration_table[s->level].max_chain; 706 707 s->strstart = 0; 708 s->block_start = 0L; 709 s->lookahead = 0; 710 s->match_length = s->prev_length = MIN_MATCH-1; 711 s->match_available = 0; 712 s->ins_h = 0; 713#ifdef ASMV 714 match_init(); /* initialize the asm code */ 715#endif 716} 717 718/* =========================================================================== 719 * Set match_start to the longest match starting at the given string and 720 * return its length. Matches shorter or equal to prev_length are discarded, 721 * in which case the result is equal to prev_length and match_start is 722 * garbage. 723 * IN assertions: cur_match is the head of the hash chain for the current 724 * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1 725 * OUT assertion: the match length is not greater than s->lookahead. 726 */ 727#ifndef ASMV 728/* For 80x86 and 680x0, an optimized version will be provided in match.asm or 729 * match.S. The code will be functionally equivalent. 730 */ 731#ifndef FASTEST 732local uInt longest_match( 733 deflate_state *s, 734 IPos cur_match) /* current match */ 735{ 736 unsigned chain_length = s->max_chain_length;/* max hash chain length */ 737 register Bytef *scan = s->window + s->strstart; /* current string */ 738 register Bytef *match; /* matched string */ 739 register int len; /* length of current match */ 740 int best_len = s->prev_length; /* best match length so far */ 741 int nice_match = s->nice_match; /* stop if match long enough */ 742 IPos limit = s->strstart > (IPos)MAX_DIST(s) ? 743 s->strstart - (IPos)MAX_DIST(s) : NIL; 744 /* Stop when cur_match becomes <= limit. To simplify the code, 745 * we prevent matches with the string of window index 0. 746 */ 747 Posf *prev = s->prev; 748 uInt wmask = s->w_mask; 749 750#ifdef UNALIGNED_OK 751 /* Compare two bytes at a time. Note: this is not always beneficial. 752 * Try with and without -DUNALIGNED_OK to check. 753 */ 754 register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1; 755 register ush scan_start = *(ushf*)scan; 756 register ush scan_end = *(ushf*)(scan+best_len-1); 757#else 758 register Bytef *strend = s->window + s->strstart + MAX_MATCH; 759 register Byte scan_end1 = scan[best_len-1]; 760 register Byte scan_end = scan[best_len]; 761#endif 762 763 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16. 764 * It is easy to get rid of this optimization if necessary. 765 */ 766 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever"); 767 768 /* Do not waste too much time if we already have a good match: */ 769 if (s->prev_length >= s->good_match) { 770 chain_length >>= 2; 771 } 772 /* Do not look for matches beyond the end of the input. This is necessary 773 * to make deflate deterministic. 774 */ 775 if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead; 776 777 Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead"); 778 779 do { 780 Assert(cur_match < s->strstart, "no future"); 781 match = s->window + cur_match; 782 783 /* Skip to next match if the match length cannot increase 784 * or if the match length is less than 2: 785 */ 786#if (defined(UNALIGNED_OK) && MAX_MATCH == 258) 787 /* This code assumes sizeof(unsigned short) == 2. Do not use 788 * UNALIGNED_OK if your compiler uses a different size. 789 */ 790 if (*(ushf*)(match+best_len-1) != scan_end || 791 *(ushf*)match != scan_start) continue; 792 793 /* It is not necessary to compare scan[2] and match[2] since they are 794 * always equal when the other bytes match, given that the hash keys 795 * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at 796 * strstart+3, +5, ... up to strstart+257. We check for insufficient 797 * lookahead only every 4th comparison; the 128th check will be made 798 * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is 799 * necessary to put more guard bytes at the end of the window, or 800 * to check more often for insufficient lookahead. 801 */ 802 Assert(scan[2] == match[2], "scan[2]?"); 803 scan++, match++; 804 do { 805 } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) && 806 *(ushf*)(scan+=2) == *(ushf*)(match+=2) && 807 *(ushf*)(scan+=2) == *(ushf*)(match+=2) && 808 *(ushf*)(scan+=2) == *(ushf*)(match+=2) && 809 scan < strend); 810 /* The funny "do {}" generates better code on most compilers */ 811 812 /* Here, scan <= window+strstart+257 */ 813 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan"); 814 if (*scan == *match) scan++; 815 816 len = (MAX_MATCH - 1) - (int)(strend-scan); 817 scan = strend - (MAX_MATCH-1); 818 819#else /* UNALIGNED_OK */ 820 821 if (match[best_len] != scan_end || 822 match[best_len-1] != scan_end1 || 823 *match != *scan || 824 *++match != scan[1]) continue; 825 826 /* The check at best_len-1 can be removed because it will be made 827 * again later. (This heuristic is not always a win.) 828 * It is not necessary to compare scan[2] and match[2] since they 829 * are always equal when the other bytes match, given that 830 * the hash keys are equal and that HASH_BITS >= 8. 831 */ 832 scan += 2, match++; 833 Assert(*scan == *match, "match[2]?"); 834 835 /* We check for insufficient lookahead only every 8th comparison; 836 * the 256th check will be made at strstart+258. 837 */ 838 do { 839 } while (*++scan == *++match && *++scan == *++match && 840 *++scan == *++match && *++scan == *++match && 841 *++scan == *++match && *++scan == *++match && 842 *++scan == *++match && *++scan == *++match && 843 scan < strend); 844 845 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan"); 846 847 len = MAX_MATCH - (int)(strend - scan); 848 scan = strend - MAX_MATCH; 849 850#endif /* UNALIGNED_OK */ 851 852 if (len > best_len) { 853 s->match_start = cur_match; 854 best_len = len; 855 if (len >= nice_match) break; 856#ifdef UNALIGNED_OK 857 scan_end = *(ushf*)(scan+best_len-1); 858#else 859 scan_end1 = scan[best_len-1]; 860 scan_end = scan[best_len]; 861#endif 862 } 863 } while ((cur_match = prev[cur_match & wmask]) > limit 864 && --chain_length != 0); 865 866 if ((uInt)best_len <= s->lookahead) return (uInt)best_len; 867 return s->lookahead; 868} 869 870#else /* FASTEST */ 871/* --------------------------------------------------------------------------- 872 * Optimized version for level == 1 only 873 */ 874local uInt longest_match( 875 deflate_state *s, 876 IPos cur_match) /* current match */ 877{ 878 register Bytef *scan = s->window + s->strstart; /* current string */ 879 register Bytef *match; /* matched string */ 880 register int len; /* length of current match */ 881 register Bytef *strend = s->window + s->strstart + MAX_MATCH; 882 883 /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16. 884 * It is easy to get rid of this optimization if necessary. 885 */ 886 Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever"); 887 888 Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead"); 889 890 Assert(cur_match < s->strstart, "no future"); 891 892 match = s->window + cur_match; 893 894 /* Return failure if the match length is less than 2: 895 */ 896 if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1; 897 898 /* The check at best_len-1 can be removed because it will be made 899 * again later. (This heuristic is not always a win.) 900 * It is not necessary to compare scan[2] and match[2] since they 901 * are always equal when the other bytes match, given that 902 * the hash keys are equal and that HASH_BITS >= 8. 903 */ 904 scan += 2, match += 2; 905 Assert(*scan == *match, "match[2]?"); 906 907 /* We check for insufficient lookahead only every 8th comparison; 908 * the 256th check will be made at strstart+258. 909 */ 910 do { 911 } while (*++scan == *++match && *++scan == *++match && 912 *++scan == *++match && *++scan == *++match && 913 *++scan == *++match && *++scan == *++match && 914 *++scan == *++match && *++scan == *++match && 915 scan < strend); 916 917 Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan"); 918 919 len = MAX_MATCH - (int)(strend - scan); 920 921 if (len < MIN_MATCH) return MIN_MATCH - 1; 922 923 s->match_start = cur_match; 924 return len <= s->lookahead ? len : s->lookahead; 925} 926#endif /* FASTEST */ 927#endif /* ASMV */ 928 929#ifdef DEBUG 930/* =========================================================================== 931 * Check that the match at match_start is indeed a match. 932 */ 933local void check_match( 934 deflate_state *s, 935 IPos start, IPos match, 936 int length) 937{ 938 /* check that the match is indeed a match */ 939 if (zmemcmp(s->window + match, 940 s->window + start, length) != EQUAL) { 941 fprintf(stderr, " start %u, match %u, length %d\n", 942 start, match, length); 943 do { 944 fprintf(stderr, "%c%c", s->window[match++], s->window[start++]); 945 } while (--length != 0); 946 z_error("invalid match"); 947 } 948 if (z_verbose > 1) { 949 fprintf(stderr,"\\[%d,%d]", start-match, length); 950 do { putc(s->window[start++], stderr); } while (--length != 0); 951 } 952} 953#else 954# define check_match(s, start, match, length) 955#endif 956 957/* =========================================================================== 958 * Fill the window when the lookahead becomes insufficient. 959 * Updates strstart and lookahead. 960 * 961 * IN assertion: lookahead < MIN_LOOKAHEAD 962 * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD 963 * At least one byte has been read, or avail_in == 0; reads are 964 * performed for at least two bytes (required for the zip translate_eol 965 * option -- not supported here). 966 */ 967local void fill_window( 968 deflate_state *s) 969{ 970 register unsigned n, m; 971 register Posf *p; 972 unsigned more; /* Amount of free space at the end of the window. */ 973 uInt wsize = s->w_size; 974 975 do { 976 more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart); 977 978 /* Deal with !@#$% 64K limit: */ 979 if (more == 0 && s->strstart == 0 && s->lookahead == 0) { 980 more = wsize; 981 982 } else if (more == (unsigned)(-1)) { 983 /* Very unlikely, but possible on 16 bit machine if strstart == 0 984 * and lookahead == 1 (input done one byte at time) 985 */ 986 more--; 987 988 /* If the window is almost full and there is insufficient lookahead, 989 * move the upper half to the lower one to make room in the upper half. 990 */ 991 } else if (s->strstart >= wsize+MAX_DIST(s)) { 992 993 zmemcpy(s->window, s->window+wsize, (unsigned)wsize); 994 s->match_start -= wsize; 995 s->strstart -= wsize; /* we now have strstart >= MAX_DIST */ 996 s->block_start -= (long) wsize; 997 998 /* Slide the hash table (could be avoided with 32 bit values 999 at the expense of memory usage). We slide even when level == 0 1000 to keep the hash table consistent if we switch back to level > 0 1001 later. (Using level 0 permanently is not an optimal usage of 1002 zlib, so we don't care about this pathological case.) 1003 */ 1004 n = s->hash_size; 1005 p = &s->head[n]; 1006 do { 1007 m = *--p; 1008 *p = (Pos)(m >= wsize ? m-wsize : NIL); 1009 } while (--n); 1010 1011 n = wsize; 1012#ifndef FASTEST 1013 p = &s->prev[n]; 1014 do { 1015 m = *--p; 1016 *p = (Pos)(m >= wsize ? m-wsize : NIL); 1017 /* If n is not on any hash chain, prev[n] is garbage but 1018 * its value will never be used. 1019 */ 1020 } while (--n); 1021#endif 1022 more += wsize; 1023 } 1024 if (s->strm->avail_in == 0) return; 1025 1026 /* If there was no sliding: 1027 * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 && 1028 * more == window_size - lookahead - strstart 1029 * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1) 1030 * => more >= window_size - 2*WSIZE + 2 1031 * In the BIG_MEM or MMAP case (not yet supported), 1032 * window_size == input_size + MIN_LOOKAHEAD && 1033 * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD. 1034 * Otherwise, window_size == 2*WSIZE so more >= 2. 1035 * If there was sliding, more >= WSIZE. So in all cases, more >= 2. 1036 */ 1037 Assert(more >= 2, "more < 2"); 1038 1039 n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more); 1040 s->lookahead += n; 1041 1042 /* Initialize the hash value now that we have some input: */ 1043 if (s->lookahead >= MIN_MATCH) { 1044 s->ins_h = s->window[s->strstart]; 1045 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]); 1046#if MIN_MATCH != 3 1047 Call UPDATE_HASH() MIN_MATCH-3 more times 1048#endif 1049 } 1050 /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage, 1051 * but this is not important since only literal bytes will be emitted. 1052 */ 1053 1054 } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0); 1055} 1056 1057/* =========================================================================== 1058 * Flush the current block, with given end-of-file flag. 1059 * IN assertion: strstart is set to the end of the current match. 1060 */ 1061#define FLUSH_BLOCK_ONLY(s, eof) { \ 1062 _tr_flush_block(s, (s->block_start >= 0L ? \ 1063 (charf *)&s->window[(unsigned)s->block_start] : \ 1064 (charf *)Z_NULL), \ 1065 (ulg)((long)s->strstart - s->block_start), \ 1066 (eof)); \ 1067 s->block_start = s->strstart; \ 1068 flush_pending(s->strm); \ 1069 Tracev((stderr,"[FLUSH]")); \ 1070} 1071 1072/* Same but force premature exit if necessary. */ 1073#define FLUSH_BLOCK(s, eof) { \ 1074 FLUSH_BLOCK_ONLY(s, eof); \ 1075 if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \ 1076} 1077 1078/* =========================================================================== 1079 * Copy without compression as much as possible from the input stream, return 1080 * the current block state. 1081 * This function does not insert new strings in the dictionary since 1082 * uncompressible data is probably not useful. This function is used 1083 * only for the level=0 compression option. 1084 * NOTE: this function should be optimized to avoid extra copying from 1085 * window to pending_buf. 1086 */ 1087local block_state deflate_stored( 1088 deflate_state *s, 1089 int flush) 1090{ 1091 /* Stored blocks are limited to 0xffff bytes, pending_buf is limited 1092 * to pending_buf_size, and each stored block has a 5 byte header: 1093 */ 1094 ulg max_block_size = 0xffff; 1095 ulg max_start; 1096 1097 if (max_block_size > s->pending_buf_size - 5) { 1098 max_block_size = s->pending_buf_size - 5; 1099 } 1100 1101 /* Copy as much as possible from input to output: */ 1102 for (;;) { 1103 /* Fill the window as much as possible: */ 1104 if (s->lookahead <= 1) { 1105 1106 Assert(s->strstart < s->w_size+MAX_DIST(s) || 1107 s->block_start >= (long)s->w_size, "slide too late"); 1108 1109 fill_window(s); 1110 if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more; 1111 1112 if (s->lookahead == 0) break; /* flush the current block */ 1113 } 1114 Assert(s->block_start >= 0L, "block gone"); 1115 1116 s->strstart += s->lookahead; 1117 s->lookahead = 0; 1118 1119 /* Emit a stored block if pending_buf will be full: */ 1120 max_start = s->block_start + max_block_size; 1121 if (s->strstart == 0 || (ulg)s->strstart >= max_start) { 1122 /* strstart == 0 is possible when wraparound on 16-bit machine */ 1123 s->lookahead = (uInt)(s->strstart - max_start); 1124 s->strstart = (uInt)max_start; 1125 FLUSH_BLOCK(s, 0); 1126 } 1127 /* Flush if we may have to slide, otherwise block_start may become 1128 * negative and the data will be gone: 1129 */ 1130 if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) { 1131 FLUSH_BLOCK(s, 0); 1132 } 1133 } 1134 FLUSH_BLOCK(s, flush == Z_FINISH); 1135 return flush == Z_FINISH ? finish_done : block_done; 1136} 1137 1138/* =========================================================================== 1139 * Compress as much as possible from the input stream, return the current 1140 * block state. 1141 * This function does not perform lazy evaluation of matches and inserts 1142 * new strings in the dictionary only for unmatched strings or for short 1143 * matches. It is used only for the fast compression options. 1144 */ 1145local block_state deflate_fast( 1146 deflate_state *s, 1147 int flush) 1148{ 1149 IPos hash_head = NIL; /* head of the hash chain */ 1150 int bflush; /* set if current block must be flushed */ 1151 1152 for (;;) { 1153 /* Make sure that we always have enough lookahead, except 1154 * at the end of the input file. We need MAX_MATCH bytes 1155 * for the next match, plus MIN_MATCH bytes to insert the 1156 * string following the next match. 1157 */ 1158 if (s->lookahead < MIN_LOOKAHEAD) { 1159 fill_window(s); 1160 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) { 1161 return need_more; 1162 } 1163 if (s->lookahead == 0) break; /* flush the current block */ 1164 } 1165 1166 /* Insert the string window[strstart .. strstart+2] in the 1167 * dictionary, and set hash_head to the head of the hash chain: 1168 */ 1169 if (s->lookahead >= MIN_MATCH) { 1170 INSERT_STRING(s, s->strstart, hash_head); 1171 } 1172 1173 /* Find the longest match, discarding those <= prev_length. 1174 * At this point we have always match_length < MIN_MATCH 1175 */ 1176 if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) { 1177 /* To simplify the code, we prevent matches with the string 1178 * of window index 0 (in particular we have to avoid a match 1179 * of the string with itself at the start of the input file). 1180 */ 1181 if (s->strategy != Z_HUFFMAN_ONLY) { 1182 s->match_length = longest_match (s, hash_head); 1183 } 1184 /* longest_match() sets match_start */ 1185 } 1186 if (s->match_length >= MIN_MATCH) { 1187 check_match(s, s->strstart, s->match_start, s->match_length); 1188 1189 _tr_tally_dist(s, s->strstart - s->match_start, 1190 s->match_length - MIN_MATCH, bflush); 1191 1192 s->lookahead -= s->match_length; 1193 1194 /* Insert new strings in the hash table only if the match length 1195 * is not too large. This saves time but degrades compression. 1196 */ 1197#ifndef FASTEST 1198 if (s->match_length <= s->max_insert_length && 1199 s->lookahead >= MIN_MATCH) { 1200 s->match_length--;/* string at strstart already in hash table */ 1201 do { 1202 s->strstart++; 1203 INSERT_STRING(s, s->strstart, hash_head); 1204 /* strstart never exceeds WSIZE-MAX_MATCH, so there are 1205 * always MIN_MATCH bytes ahead. 1206 */ 1207 } while (--s->match_length != 0); 1208 s->strstart++; 1209 } else 1210#endif 1211 { 1212 s->strstart += s->match_length; 1213 s->match_length = 0; 1214 s->ins_h = s->window[s->strstart]; 1215 UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]); 1216#if MIN_MATCH != 3 1217 Call UPDATE_HASH() MIN_MATCH-3 more times 1218#endif 1219 /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not 1220 * matter since it will be recomputed at next deflate call. 1221 */ 1222 } 1223 } else { 1224 /* No match, output a literal byte */ 1225 Tracevv((stderr,"%c", s->window[s->strstart])); 1226 _tr_tally_lit (s, s->window[s->strstart], bflush); 1227 s->lookahead--; 1228 s->strstart++; 1229 } 1230 if (bflush) FLUSH_BLOCK(s, 0); 1231 } 1232 FLUSH_BLOCK(s, flush == Z_FINISH); 1233 return flush == Z_FINISH ? finish_done : block_done; 1234} 1235 1236/* =========================================================================== 1237 * Same as above, but achieves better compression. We use a lazy 1238 * evaluation for matches: a match is finally adopted only if there is 1239 * no better match at the next window position. 1240 */ 1241local block_state deflate_slow( 1242 deflate_state *s, 1243 int flush) 1244{ 1245 IPos hash_head = NIL; /* head of hash chain */ 1246 int bflush; /* set if current block must be flushed */ 1247 1248 /* Process the input block. */ 1249 for (;;) { 1250 /* Make sure that we always have enough lookahead, except 1251 * at the end of the input file. We need MAX_MATCH bytes 1252 * for the next match, plus MIN_MATCH bytes to insert the 1253 * string following the next match. 1254 */ 1255 if (s->lookahead < MIN_LOOKAHEAD) { 1256 fill_window(s); 1257 if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) { 1258 return need_more; 1259 } 1260 if (s->lookahead == 0) break; /* flush the current block */ 1261 } 1262 1263 /* Insert the string window[strstart .. strstart+2] in the 1264 * dictionary, and set hash_head to the head of the hash chain: 1265 */ 1266 if (s->lookahead >= MIN_MATCH) { 1267 INSERT_STRING(s, s->strstart, hash_head); 1268 } 1269 1270 /* Find the longest match, discarding those <= prev_length. 1271 */ 1272 s->prev_length = s->match_length, s->prev_match = s->match_start; 1273 s->match_length = MIN_MATCH-1; 1274 1275 if (hash_head != NIL && s->prev_length < s->max_lazy_match && 1276 s->strstart - hash_head <= MAX_DIST(s)) { 1277 /* To simplify the code, we prevent matches with the string 1278 * of window index 0 (in particular we have to avoid a match 1279 * of the string with itself at the start of the input file). 1280 */ 1281 if (s->strategy != Z_HUFFMAN_ONLY) { 1282 s->match_length = longest_match (s, hash_head); 1283 } 1284 /* longest_match() sets match_start */ 1285 1286 if (s->match_length <= 5 && (s->strategy == Z_FILTERED || 1287 (s->match_length == MIN_MATCH && 1288 s->strstart - s->match_start > TOO_FAR))) { 1289 1290 /* If prev_match is also MIN_MATCH, match_start is garbage 1291 * but we will ignore the current match anyway. 1292 */ 1293 s->match_length = MIN_MATCH-1; 1294 } 1295 } 1296 /* If there was a match at the previous step and the current 1297 * match is not better, output the previous match: 1298 */ 1299 if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) { 1300 uInt max_insert = s->strstart + s->lookahead - MIN_MATCH; 1301 /* Do not insert strings in hash table beyond this. */ 1302 1303 check_match(s, s->strstart-1, s->prev_match, s->prev_length); 1304 1305 _tr_tally_dist(s, s->strstart -1 - s->prev_match, 1306 s->prev_length - MIN_MATCH, bflush); 1307 1308 /* Insert in hash table all strings up to the end of the match. 1309 * strstart-1 and strstart are already inserted. If there is not 1310 * enough lookahead, the last two strings are not inserted in 1311 * the hash table. 1312 */ 1313 s->lookahead -= s->prev_length-1; 1314 s->prev_length -= 2; 1315 do { 1316 if (++s->strstart <= max_insert) { 1317 INSERT_STRING(s, s->strstart, hash_head); 1318 } 1319 } while (--s->prev_length != 0); 1320 s->match_available = 0; 1321 s->match_length = MIN_MATCH-1; 1322 s->strstart++; 1323 1324 if (bflush) FLUSH_BLOCK(s, 0); 1325 1326 } else if (s->match_available) { 1327 /* If there was no match at the previous position, output a 1328 * single literal. If there was a match but the current match 1329 * is longer, truncate the previous match to a single literal. 1330 */ 1331 Tracevv((stderr,"%c", s->window[s->strstart-1])); 1332 _tr_tally_lit(s, s->window[s->strstart-1], bflush); 1333 if (bflush) { 1334 FLUSH_BLOCK_ONLY(s, 0); 1335 } 1336 s->strstart++; 1337 s->lookahead--; 1338 if (s->strm->avail_out == 0) return need_more; 1339 } else { 1340 /* There is no previous match to compare with, wait for 1341 * the next step to decide. 1342 */ 1343 s->match_available = 1; 1344 s->strstart++; 1345 s->lookahead--; 1346 } 1347 } 1348 Assert (flush != Z_NO_FLUSH, "no flush?"); 1349 if (s->match_available) { 1350 Tracevv((stderr,"%c", s->window[s->strstart-1])); 1351 _tr_tally_lit(s, s->window[s->strstart-1], bflush); 1352 s->match_available = 0; 1353 } 1354 FLUSH_BLOCK(s, flush == Z_FINISH); 1355 return flush == Z_FINISH ? finish_done : block_done; 1356} 1357