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1 /* $Header$ */
2
3 /*
4 * Copyright (c) 1988-1997 Sam Leffler
5 * Copyright (c) 1991-1997 Silicon Graphics, Inc.
6 *
7 * Permission to use, copy, modify, distribute, and sell this software and
8 * its documentation for any purpose is hereby granted without fee, provided
9 * that (i) the above copyright notices and this permission notice appear in
10 * all copies of the software and related documentation, and (ii) the names of
11 * Sam Leffler and Silicon Graphics may not be used in any advertising or
12 * publicity relating to the software without the specific, prior written
13 * permission of Sam Leffler and Silicon Graphics.
14 *
15 * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
17 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
18 *
19 * IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
20 * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
21 * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
22 * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
23 * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
24 * OF THIS SOFTWARE.
25 */
26
27 #include "tiffiop.h"
28 #ifdef LZW_SUPPORT
29 /*
30 * TIFF Library.
31 * Rev 5.0 Lempel-Ziv & Welch Compression Support
32 *
33 * This code is derived from the compress program whose code is
34 * derived from software contributed to Berkeley by James A. Woods,
35 * derived from original work by Spencer Thomas and Joseph Orost.
36 *
37 * The original Berkeley copyright notice appears below in its entirety.
38 */
39 /* Watcom C++ (or its make utility) doesn't like long filenames */
40 #ifdef __WATCOMC__
41 #include "tif_pred.h"
42 #else
43 #include "tif_predict.h"
44 #endif
45
46 #include <assert.h>
47 #include <stdio.h>
48
49 /*
50 * NB: The 5.0 spec describes a different algorithm than Aldus
51 * implements. Specifically, Aldus does code length transitions
52 * one code earlier than should be done (for real LZW).
53 * Earlier versions of this library implemented the correct
54 * LZW algorithm, but emitted codes in a bit order opposite
55 * to the TIFF spec. Thus, to maintain compatibility w/ Aldus
56 * we interpret MSB-LSB ordered codes to be images written w/
57 * old versions of this library, but otherwise adhere to the
58 * Aldus "off by one" algorithm.
59 *
60 * Future revisions to the TIFF spec are expected to "clarify this issue".
61 */
62 #define LZW_COMPAT /* include backwards compatibility code */
63 /*
64 * Each strip of data is supposed to be terminated by a CODE_EOI.
65 * If the following #define is included, the decoder will also
66 * check for end-of-strip w/o seeing this code. This makes the
67 * library more robust, but also slower.
68 */
69 #define LZW_CHECKEOS /* include checks for strips w/o EOI code */
70
71 #define MAXCODE(n) ((1L<<(n))-1)
72 /*
73 * The TIFF spec specifies that encoded bit
74 * strings range from 9 to 12 bits.
75 */
76 #define BITS_MIN 9 /* start with 9 bits */
77 #define BITS_MAX 12 /* max of 12 bit strings */
78 /* predefined codes */
79 #define CODE_CLEAR 256 /* code to clear string table */
80 #define CODE_EOI 257 /* end-of-information code */
81 #define CODE_FIRST 258 /* first free code entry */
82 #define CODE_MAX MAXCODE(BITS_MAX)
83 #define HSIZE 9001L /* 91% occupancy */
84 #define HSHIFT (13-8)
85 #ifdef LZW_COMPAT
86 /* NB: +1024 is for compatibility with old files */
87 #define CSIZE (MAXCODE(BITS_MAX)+1024L)
88 #else
89 #define CSIZE (MAXCODE(BITS_MAX)+1L)
90 #endif
91
92 /*
93 * State block for each open TIFF file using LZW
94 * compression/decompression. Note that the predictor
95 * state block must be first in this data structure.
96 */
97 typedef struct {
98 TIFFPredictorState predict; /* predictor super class */
99
100 u_short nbits; /* # of bits/code */
101 u_short maxcode; /* maximum code for lzw_nbits */
102 u_short free_ent; /* next free entry in hash table */
103 long nextdata; /* next bits of i/o */
104 long nextbits; /* # of valid bits in lzw_nextdata */
105 } LZWBaseState;
106
107 #define lzw_nbits base.nbits
108 #define lzw_maxcode base.maxcode
109 #define lzw_free_ent base.free_ent
110 #define lzw_nextdata base.nextdata
111 #define lzw_nextbits base.nextbits
112
113 /*
114 * Decoding-specific state.
115 */
116 typedef struct code_ent {
117 struct code_ent *next;
118 u_short length; /* string len, including this token */
119 u_char value; /* data value */
120 u_char firstchar; /* first token of string */
121 } code_t;
122
123 typedef int (LINKAGEMODE *decodeFunc)(TIFF*, tidata_t, tsize_t, tsample_t);
124
125 typedef struct {
126 LZWBaseState base;
127 long dec_nbitsmask; /* lzw_nbits 1 bits, right adjusted */
128 long dec_restart; /* restart count */
129 #ifdef LZW_CHECKEOS
130 long dec_bitsleft; /* available bits in raw data */
131 #endif
132 decodeFunc dec_decode; /* regular or backwards compatible */
133 code_t* dec_codep; /* current recognized code */
134 code_t* dec_oldcodep; /* previously recognized code */
135 code_t* dec_free_entp; /* next free entry */
136 code_t* dec_maxcodep; /* max available entry */
137 code_t* dec_codetab; /* kept separate for small machines */
138 } LZWDecodeState;
139
140 /*
141 * Encoding-specific state.
142 */
143 typedef uint16 hcode_t; /* codes fit in 16 bits */
144 typedef struct {
145 long hash;
146 hcode_t code;
147 } hash_t;
148
149 typedef struct {
150 LZWBaseState base;
151 int enc_oldcode; /* last code encountered */
152 long enc_checkpoint; /* point at which to clear table */
153 #define CHECK_GAP 10000 /* enc_ratio check interval */
154 long enc_ratio; /* current compression ratio */
155 long enc_incount; /* (input) data bytes encoded */
156 long enc_outcount; /* encoded (output) bytes */
157 tidata_t enc_rawlimit; /* bound on tif_rawdata buffer */
158 hash_t* enc_hashtab; /* kept separate for small machines */
159 } LZWEncodeState;
160
161 #define LZWState(tif) ((LZWBaseState*) (tif)->tif_data)
162 #define DecoderState(tif) ((LZWDecodeState*) LZWState(tif))
163 #define EncoderState(tif) ((LZWEncodeState*) LZWState(tif))
164
165 static int LINKAGEMODE LZWDecode(TIFF*, tidata_t, tsize_t, tsample_t);
166 #ifdef LZW_COMPAT
167 static int LINKAGEMODE LZWDecodeCompat(TIFF*, tidata_t, tsize_t, tsample_t);
168 #endif
169 static void cl_hash(LZWEncodeState*);
170
171 /*
172 * LZW Decoder.
173 */
174
175 #ifdef LZW_CHECKEOS
176 /*
177 * This check shouldn't be necessary because each
178 * strip is suppose to be terminated with CODE_EOI.
179 */
180 #define NextCode(_tif, _sp, _bp, _code, _get) { \
181 if ((_sp)->dec_bitsleft < nbits) { \
182 TIFFWarning(_tif->tif_name, \
183 "LZWDecode: Strip %d not terminated with EOI code", \
184 _tif->tif_curstrip); \
185 _code = CODE_EOI; \
186 } else { \
187 _get(_sp,_bp,_code); \
188 (_sp)->dec_bitsleft -= nbits; \
189 } \
190 }
191 #else
192 #define NextCode(tif, sp, bp, code, get) get(sp, bp, code)
193 #endif
194
195 static int
196 LZWSetupDecode(TIFF* tif)
197 {
198 LZWDecodeState* sp = DecoderState(tif);
199 static const char module[] = " LZWSetupDecode";
200 int code;
201
202 assert(sp != NULL);
203 if (sp->dec_codetab == NULL) {
204 sp->dec_codetab = (code_t*)_TIFFmalloc(CSIZE*sizeof (code_t));
205 if (sp->dec_codetab == NULL) {
206 TIFFError(module, "No space for LZW code table");
207 return (0);
208 }
209 /*
210 * Pre-load the table.
211 */
212 for (code = 255; code >= 0; code--) {
213 sp->dec_codetab[code].value = code;
214 sp->dec_codetab[code].firstchar = code;
215 sp->dec_codetab[code].length = 1;
216 sp->dec_codetab[code].next = NULL;
217 }
218 }
219 return (1);
220 }
221
222 /*
223 * Setup state for decoding a strip.
224 */
225 static int
226 LZWPreDecode(TIFF* tif, tsample_t s)
227 {
228 LZWDecodeState *sp = DecoderState(tif);
229
230 (void) s;
231 assert(sp != NULL);
232 /*
233 * Check for old bit-reversed codes.
234 */
235 if (tif->tif_rawdata[0] == 0 && (tif->tif_rawdata[1] & 0x1)) {
236 #ifdef LZW_COMPAT
237 if (!sp->dec_decode) {
238 TIFFWarning(tif->tif_name,
239 "Old-style LZW codes, convert file");
240 /*
241 * Override default decoding methods with
242 * ones that deal with the old coding.
243 * Otherwise the predictor versions set
244 * above will call the compatibility routines
245 * through the dec_decode method.
246 */
247 tif->tif_decoderow = LZWDecodeCompat;
248 tif->tif_decodestrip = LZWDecodeCompat;
249 tif->tif_decodetile = LZWDecodeCompat;
250 /*
251 * If doing horizontal differencing, must
252 * re-setup the predictor logic since we
253 * switched the basic decoder methods...
254 */
255 (*tif->tif_setupdecode)(tif);
256 sp->dec_decode = LZWDecodeCompat;
257 }
258 sp->lzw_maxcode = MAXCODE(BITS_MIN);
259 #else /* !LZW_COMPAT */
260 if (!sp->dec_decode) {
261 TIFFError(tif->tif_name,
262 "Old-style LZW codes not supported");
263 sp->dec_decode = LZWDecode;
264 }
265 return (0);
266 #endif/* !LZW_COMPAT */
267 } else {
268 sp->lzw_maxcode = MAXCODE(BITS_MIN)-1;
269 sp->dec_decode = LZWDecode;
270 }
271 sp->lzw_nbits = BITS_MIN;
272 sp->lzw_nextbits = 0;
273 sp->lzw_nextdata = 0;
274
275 sp->dec_restart = 0;
276 sp->dec_nbitsmask = MAXCODE(BITS_MIN);
277 #ifdef LZW_CHECKEOS
278 sp->dec_bitsleft = tif->tif_rawcc << 3;
279 #endif
280 sp->dec_free_entp = sp->dec_codetab + CODE_FIRST;
281 /*
282 * Zero entries that are not yet filled in. We do
283 * this to guard against bogus input data that causes
284 * us to index into undefined entries. If you can
285 * come up with a way to safely bounds-check input codes
286 * while decoding then you can remove this operation.
287 */
288 _TIFFmemset(sp->dec_free_entp, 0, (CSIZE-CODE_FIRST)*sizeof (code_t));
289 sp->dec_oldcodep = &sp->dec_codetab[-1];
290 sp->dec_maxcodep = &sp->dec_codetab[sp->dec_nbitsmask-1];
291 return (1);
292 }
293
294 /*
295 * Decode a "hunk of data".
296 */
297 #define GetNextCode(sp, bp, code) { \
298 nextdata = (nextdata<<8) | *(bp)++; \
299 nextbits += 8; \
300 if (nextbits < nbits) { \
301 nextdata = (nextdata<<8) | *(bp)++; \
302 nextbits += 8; \
303 } \
304 code = (hcode_t)((nextdata >> (nextbits-nbits)) & nbitsmask); \
305 nextbits -= nbits; \
306 }
307
308 static void
309 codeLoop(TIFF* tif)
310 {
311 TIFFError(tif->tif_name,
312 "LZWDecode: Bogus encoding, loop in the code table; scanline %d",
313 tif->tif_row);
314 }
315
316 static int
317 LZWDecode(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
318 {
319 LZWDecodeState *sp = DecoderState(tif);
320 char *op = (char*) op0;
321 long occ = (long) occ0;
322 char *tp;
323 u_char *bp;
324 hcode_t code;
325 int len;
326 long nbits, nextbits, nextdata, nbitsmask;
327 code_t *codep, *free_entp, *maxcodep, *oldcodep;
328
329 (void) s;
330 assert(sp != NULL);
331 /*
332 * Restart interrupted output operation.
333 */
334 if (sp->dec_restart) {
335 long residue;
336
337 codep = sp->dec_codep;
338 residue = codep->length - sp->dec_restart;
339 if (residue > occ) {
340 /*
341 * Residue from previous decode is sufficient
342 * to satisfy decode request. Skip to the
343 * start of the decoded string, place decoded
344 * values in the output buffer, and return.
345 */
346 sp->dec_restart += occ;
347 do {
348 codep = codep->next;
349 } while (--residue > occ && codep);
350 if (codep) {
351 tp = op + occ;
352 do {
353 *--tp = codep->value;
354 codep = codep->next;
355 } while (--occ && codep);
356 }
357 return (1);
358 }
359 /*
360 * Residue satisfies only part of the decode request.
361 */
362 op += residue, occ -= residue;
363 tp = op;
364 do {
365 int t;
366 --tp;
367 t = codep->value;
368 codep = codep->next;
369 *tp = t;
370 } while (--residue && codep);
371 sp->dec_restart = 0;
372 }
373
374 bp = (u_char *)tif->tif_rawcp;
375 nbits = sp->lzw_nbits;
376 nextdata = sp->lzw_nextdata;
377 nextbits = sp->lzw_nextbits;
378 nbitsmask = sp->dec_nbitsmask;
379 oldcodep = sp->dec_oldcodep;
380 free_entp = sp->dec_free_entp;
381 maxcodep = sp->dec_maxcodep;
382
383 while (occ > 0) {
384 NextCode(tif, sp, bp, code, GetNextCode);
385 if (code == CODE_EOI)
386 break;
387 if (code == CODE_CLEAR) {
388 free_entp = sp->dec_codetab + CODE_FIRST;
389 nbits = BITS_MIN;
390 nbitsmask = MAXCODE(BITS_MIN);
391 maxcodep = sp->dec_codetab + nbitsmask-1;
392 NextCode(tif, sp, bp, code, GetNextCode);
393 if (code == CODE_EOI)
394 break;
395 *op++ = code, occ--;
396 oldcodep = sp->dec_codetab + code;
397 continue;
398 }
399 codep = sp->dec_codetab + code;
400
401 /*
402 * Add the new entry to the code table.
403 */
404 assert(&sp->dec_codetab[0] <= free_entp && free_entp < &sp->dec_codetab[CSIZE]);
405 free_entp->next = oldcodep;
406 free_entp->firstchar = free_entp->next->firstchar;
407 free_entp->length = free_entp->next->length+1;
408 free_entp->value = (codep < free_entp) ?
409 codep->firstchar : free_entp->firstchar;
410 if (++free_entp > maxcodep) {
411 if (++nbits > BITS_MAX) /* should not happen */
412 nbits = BITS_MAX;
413 nbitsmask = MAXCODE(nbits);
414 maxcodep = sp->dec_codetab + nbitsmask-1;
415 }
416 oldcodep = codep;
417 if (code >= 256) {
418 /*
419 * Code maps to a string, copy string
420 * value to output (written in reverse).
421 */
422 if (codep->length > occ) {
423 /*
424 * String is too long for decode buffer,
425 * locate portion that will fit, copy to
426 * the decode buffer, and setup restart
427 * logic for the next decoding call.
428 */
429 sp->dec_codep = codep;
430 do {
431 codep = codep->next;
432 } while (codep && codep->length > occ);
433 if (codep) {
434 sp->dec_restart = occ;
435 tp = op + occ;
436 do {
437 *--tp = codep->value;
438 codep = codep->next;
439 } while (--occ && codep);
440 if (codep)
441 codeLoop(tif);
442 }
443 break;
444 }
445 len = codep->length;
446 tp = op + len;
447 do {
448 int t;
449 --tp;
450 t = codep->value;
451 codep = codep->next;
452 *tp = t;
453 } while (codep && tp > op);
454 if (codep) {
455 codeLoop(tif);
456 break;
457 }
458 op += len, occ -= len;
459 } else
460 *op++ = code, occ--;
461 }
462
463 tif->tif_rawcp = (tidata_t) bp;
464 sp->lzw_nbits = (u_short) nbits;
465 sp->lzw_nextdata = nextdata;
466 sp->lzw_nextbits = nextbits;
467 sp->dec_nbitsmask = nbitsmask;
468 sp->dec_oldcodep = oldcodep;
469 sp->dec_free_entp = free_entp;
470 sp->dec_maxcodep = maxcodep;
471
472 if (occ > 0) {
473 TIFFError(tif->tif_name,
474 "LZWDecode: Not enough data at scanline %d (short %d bytes)",
475 tif->tif_row, occ);
476 return (0);
477 }
478 return (1);
479 }
480
481 #ifdef LZW_COMPAT
482 /*
483 * Decode a "hunk of data" for old images.
484 */
485 #define GetNextCodeCompat(sp, bp, code) { \
486 nextdata |= (u_long) *(bp)++ << nextbits; \
487 nextbits += 8; \
488 if (nextbits < nbits) { \
489 nextdata |= (u_long) *(bp)++ << nextbits; \
490 nextbits += 8; \
491 } \
492 code = (hcode_t)(nextdata & nbitsmask); \
493 nextdata >>= nbits; \
494 nextbits -= nbits; \
495 }
496
497 static int LINKAGEMODE
498 LZWDecodeCompat(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
499 {
500 LZWDecodeState *sp = DecoderState(tif);
501 char *op = (char*) op0;
502 long occ = (long) occ0;
503 char *tp;
504 u_char *bp;
505 int code, nbits;
506 long nextbits, nextdata, nbitsmask;
507 code_t *codep, *free_entp, *maxcodep, *oldcodep;
508
509 (void) s;
510 assert(sp != NULL);
511 /*
512 * Restart interrupted output operation.
513 */
514 if (sp->dec_restart) {
515 long residue;
516
517 codep = sp->dec_codep;
518 residue = codep->length - sp->dec_restart;
519 if (residue > occ) {
520 /*
521 * Residue from previous decode is sufficient
522 * to satisfy decode request. Skip to the
523 * start of the decoded string, place decoded
524 * values in the output buffer, and return.
525 */
526 sp->dec_restart += occ;
527 do {
528 codep = codep->next;
529 } while (--residue > occ);
530 tp = op + occ;
531 do {
532 *--tp = codep->value;
533 codep = codep->next;
534 } while (--occ);
535 return (1);
536 }
537 /*
538 * Residue satisfies only part of the decode request.
539 */
540 op += residue, occ -= residue;
541 tp = op;
542 do {
543 *--tp = codep->value;
544 codep = codep->next;
545 } while (--residue);
546 sp->dec_restart = 0;
547 }
548
549 bp = (u_char *)tif->tif_rawcp;
550 nbits = sp->lzw_nbits;
551 nextdata = sp->lzw_nextdata;
552 nextbits = sp->lzw_nextbits;
553 nbitsmask = sp->dec_nbitsmask;
554 oldcodep = sp->dec_oldcodep;
555 free_entp = sp->dec_free_entp;
556 maxcodep = sp->dec_maxcodep;
557
558 while (occ > 0) {
559 NextCode(tif, sp, bp, code, GetNextCodeCompat);
560 if (code == CODE_EOI)
561 break;
562 if (code == CODE_CLEAR) {
563 free_entp = sp->dec_codetab + CODE_FIRST;
564 nbits = BITS_MIN;
565 nbitsmask = MAXCODE(BITS_MIN);
566 maxcodep = sp->dec_codetab + nbitsmask;
567 NextCode(tif, sp, bp, code, GetNextCodeCompat);
568 if (code == CODE_EOI)
569 break;
570 *op++ = code, occ--;
571 oldcodep = sp->dec_codetab + code;
572 continue;
573 }
574 codep = sp->dec_codetab + code;
575
576 /*
577 * Add the new entry to the code table.
578 */
579 assert(&sp->dec_codetab[0] <= free_entp && free_entp < &sp->dec_codetab[CSIZE]);
580 free_entp->next = oldcodep;
581 free_entp->firstchar = free_entp->next->firstchar;
582 free_entp->length = free_entp->next->length+1;
583 free_entp->value = (codep < free_entp) ?
584 codep->firstchar : free_entp->firstchar;
585 if (++free_entp > maxcodep) {
586 if (++nbits > BITS_MAX) /* should not happen */
587 nbits = BITS_MAX;
588 nbitsmask = MAXCODE(nbits);
589 maxcodep = sp->dec_codetab + nbitsmask;
590 }
591 oldcodep = codep;
592 if (code >= 256) {
593 /*
594 * Code maps to a string, copy string
595 * value to output (written in reverse).
596 */
597 if (codep->length > occ) {
598 /*
599 * String is too long for decode buffer,
600 * locate portion that will fit, copy to
601 * the decode buffer, and setup restart
602 * logic for the next decoding call.
603 */
604 sp->dec_codep = codep;
605 do {
606 codep = codep->next;
607 } while (codep->length > occ);
608 sp->dec_restart = occ;
609 tp = op + occ;
610 do {
611 *--tp = codep->value;
612 codep = codep->next;
613 } while (--occ);
614 break;
615 }
616 op += codep->length, occ -= codep->length;
617 tp = op;
618 do {
619 *--tp = codep->value;
620 } while( (codep = codep->next) != NULL);
621 } else
622 *op++ = code, occ--;
623 }
624
625 tif->tif_rawcp = (tidata_t) bp;
626 sp->lzw_nbits = nbits;
627 sp->lzw_nextdata = nextdata;
628 sp->lzw_nextbits = nextbits;
629 sp->dec_nbitsmask = nbitsmask;
630 sp->dec_oldcodep = oldcodep;
631 sp->dec_free_entp = free_entp;
632 sp->dec_maxcodep = maxcodep;
633
634 if (occ > 0) {
635 TIFFError(tif->tif_name,
636 "LZWDecodeCompat: Not enough data at scanline %d (short %d bytes)",
637 tif->tif_row, occ);
638 return (0);
639 }
640 return (1);
641 }
642 #endif /* LZW_COMPAT */
643
644 /*
645 * LZW Encoding.
646 */
647
648 static int
649 LZWSetupEncode(TIFF* tif)
650 {
651 LZWEncodeState* sp = EncoderState(tif);
652 static const char module[] = "LZWSetupEncode";
653
654 assert(sp != NULL);
655 sp->enc_hashtab = (hash_t*) _TIFFmalloc(HSIZE*sizeof (hash_t));
656 if (sp->enc_hashtab == NULL) {
657 TIFFError(module, "No space for LZW hash table");
658 return (0);
659 }
660 return (1);
661 }
662
663 /*
664 * Reset encoding state at the start of a strip.
665 */
666 static int
667 LZWPreEncode(TIFF* tif, tsample_t s)
668 {
669 LZWEncodeState *sp = EncoderState(tif);
670
671 (void) s;
672 assert(sp != NULL);
673 sp->lzw_nbits = BITS_MIN;
674 sp->lzw_maxcode = MAXCODE(BITS_MIN);
675 sp->lzw_free_ent = CODE_FIRST;
676 sp->lzw_nextbits = 0;
677 sp->lzw_nextdata = 0;
678 sp->enc_checkpoint = CHECK_GAP;
679 sp->enc_ratio = 0;
680 sp->enc_incount = 0;
681 sp->enc_outcount = 0;
682 /*
683 * The 4 here insures there is space for 2 max-sized
684 * codes in LZWEncode and LZWPostDecode.
685 */
686 sp->enc_rawlimit = tif->tif_rawdata + tif->tif_rawdatasize-1 - 4;
687 cl_hash(sp); /* clear hash table */
688 sp->enc_oldcode = (hcode_t) -1; /* generates CODE_CLEAR in LZWEncode */
689 return (1);
690 }
691
692 #define CALCRATIO(sp, rat) { \
693 if (incount > 0x007fffff) { /* NB: shift will overflow */\
694 rat = outcount >> 8; \
695 rat = (rat == 0 ? 0x7fffffff : incount/rat); \
696 } else \
697 rat = (incount<<8) / outcount; \
698 }
699 #define PutNextCode(op, c) { \
700 nextdata = (nextdata << nbits) | c; \
701 nextbits += nbits; \
702 *op++ = (u_char)(nextdata >> (nextbits-8)); \
703 nextbits -= 8; \
704 if (nextbits >= 8) { \
705 *op++ = (u_char)(nextdata >> (nextbits-8)); \
706 nextbits -= 8; \
707 } \
708 outcount += nbits; \
709 }
710
711 /*
712 * Encode a chunk of pixels.
713 *
714 * Uses an open addressing double hashing (no chaining) on the
715 * prefix code/next character combination. We do a variant of
716 * Knuth's algorithm D (vol. 3, sec. 6.4) along with G. Knott's
717 * relatively-prime secondary probe. Here, the modular division
718 * first probe is gives way to a faster exclusive-or manipulation.
719 * Also do block compression with an adaptive reset, whereby the
720 * code table is cleared when the compression ratio decreases,
721 * but after the table fills. The variable-length output codes
722 * are re-sized at this point, and a CODE_CLEAR is generated
723 * for the decoder.
724 */
725 static int LINKAGEMODE
726 LZWEncode(TIFF* tif, tidata_t bp, tsize_t cc, tsample_t s)
727 {
728 register LZWEncodeState *sp = EncoderState(tif);
729 register long fcode;
730 register hash_t *hp;
731 register int h, c;
732 hcode_t ent;
733 long disp;
734 long incount, outcount, checkpoint;
735 long nextdata, nextbits;
736 int free_ent, maxcode, nbits;
737 tidata_t op, limit;
738
739 (void) s;
740 if (sp == NULL)
741 return (0);
742 /*
743 * Load local state.
744 */
745 incount = sp->enc_incount;
746 outcount = sp->enc_outcount;
747 checkpoint = sp->enc_checkpoint;
748 nextdata = sp->lzw_nextdata;
749 nextbits = sp->lzw_nextbits;
750 free_ent = sp->lzw_free_ent;
751 maxcode = sp->lzw_maxcode;
752 nbits = sp->lzw_nbits;
753 op = tif->tif_rawcp;
754 limit = sp->enc_rawlimit;
755 ent = sp->enc_oldcode;
756
757 if (ent == (hcode_t) -1 && cc > 0) {
758 /*
759 * NB: This is safe because it can only happen
760 * at the start of a strip where we know there
761 * is space in the data buffer.
762 */
763 PutNextCode(op, CODE_CLEAR);
764 ent = *bp++; cc--; incount++;
765 }
766 while (cc > 0) {
767 c = *bp++; cc--; incount++;
768 fcode = ((long)c << BITS_MAX) + ent;
769 h = (c << HSHIFT) ^ ent; /* xor hashing */
770 #ifdef _WINDOWS
771 /*
772 * Check hash index for an overflow.
773 */
774 if (h >= HSIZE)
775 h -= HSIZE;
776 #endif
777 hp = &sp->enc_hashtab[h];
778 if (hp->hash == fcode) {
779 ent = hp->code;
780 continue;
781 }
782 if (hp->hash >= 0) {
783 /*
784 * Primary hash failed, check secondary hash.
785 */
786 disp = HSIZE - h;
787 if (h == 0)
788 disp = 1;
789 do {
790 /*
791 * Avoid pointer arithmetic 'cuz of
792 * wraparound problems with segments.
793 */
794 if ((h -= disp) < 0)
795 h += HSIZE;
796 hp = &sp->enc_hashtab[h];
797 if (hp->hash == fcode) {
798 ent = hp->code;
799 goto hit;
800 }
801 } while (hp->hash >= 0);
802 }
803 /*
804 * New entry, emit code and add to table.
805 */
806 /*
807 * Verify there is space in the buffer for the code
808 * and any potential Clear code that might be emitted
809 * below. The value of limit is setup so that there
810 * are at least 4 bytes free--room for 2 codes.
811 */
812 if (op > limit) {
813 tif->tif_rawcc = (tsize_t)(op - tif->tif_rawdata);
814 TIFFFlushData1(tif);
815 op = tif->tif_rawdata;
816 }
817 PutNextCode(op, ent);
818 ent = c;
819 hp->code = free_ent++;
820 hp->hash = fcode;
821 if (free_ent == CODE_MAX-1) {
822 /* table is full, emit clear code and reset */
823 cl_hash(sp);
824 sp->enc_ratio = 0;
825 incount = 0;
826 outcount = 0;
827 free_ent = CODE_FIRST;
828 PutNextCode(op, CODE_CLEAR);
829 nbits = BITS_MIN;
830 maxcode = MAXCODE(BITS_MIN);
831 } else {
832 /*
833 * If the next entry is going to be too big for
834 * the code size, then increase it, if possible.
835 */
836 if (free_ent > maxcode) {
837 nbits++;
838 assert(nbits <= BITS_MAX);
839 maxcode = (int) MAXCODE(nbits);
840 } else if (incount >= checkpoint) {
841 long rat;
842 /*
843 * Check compression ratio and, if things seem
844 * to be slipping, clear the hash table and
845 * reset state. The compression ratio is a
846 * 24+8-bit fractional number.
847 */
848 checkpoint = incount+CHECK_GAP;
849 CALCRATIO(sp, rat);
850 if (rat <= sp->enc_ratio) {
851 cl_hash(sp);
852 sp->enc_ratio = 0;
853 incount = 0;
854 outcount = 0;
855 free_ent = CODE_FIRST;
856 PutNextCode(op, CODE_CLEAR);
857 nbits = BITS_MIN;
858 maxcode = MAXCODE(BITS_MIN);
859 } else
860 sp->enc_ratio = rat;
861 }
862 }
863 hit:
864 ;
865 }
866
867 /*
868 * Restore global state.
869 */
870 sp->enc_incount = incount;
871 sp->enc_outcount = outcount;
872 sp->enc_checkpoint = checkpoint;
873 sp->enc_oldcode = ent;
874 sp->lzw_nextdata = nextdata;
875 sp->lzw_nextbits = nextbits;
876 sp->lzw_free_ent = free_ent;
877 sp->lzw_maxcode = maxcode;
878 sp->lzw_nbits = nbits;
879 tif->tif_rawcp = op;
880 return (1);
881 }
882
883 /*
884 * Finish off an encoded strip by flushing the last
885 * string and tacking on an End Of Information code.
886 */
887 static int
888 LZWPostEncode(TIFF* tif)
889 {
890 register LZWEncodeState *sp = EncoderState(tif);
891 tidata_t op = tif->tif_rawcp;
892 long nextbits = sp->lzw_nextbits;
893 long nextdata = sp->lzw_nextdata;
894 long outcount = sp->enc_outcount;
895 int nbits = sp->lzw_nbits;
896
897 if (op > sp->enc_rawlimit) {
898 tif->tif_rawcc = (tsize_t)(op - tif->tif_rawdata);
899 TIFFFlushData1(tif);
900 op = tif->tif_rawdata;
901 }
902 if (sp->enc_oldcode != (hcode_t) -1) {
903 PutNextCode(op, sp->enc_oldcode);
904 sp->enc_oldcode = (hcode_t) -1;
905 }
906 PutNextCode(op, CODE_EOI);
907 if (nextbits > 0)
908 *op++ = (u_char)(nextdata << (8-nextbits));
909 tif->tif_rawcc = (tsize_t)(op - tif->tif_rawdata);
910 return (1);
911 }
912
913 /*
914 * Reset encoding hash table.
915 */
916 static void
917 cl_hash(LZWEncodeState* sp)
918 {
919 register hash_t *hp = &sp->enc_hashtab[HSIZE-1];
920 register long i = HSIZE-8;
921
922 do {
923 i -= 8;
924 hp[-7].hash = -1;
925 hp[-6].hash = -1;
926 hp[-5].hash = -1;
927 hp[-4].hash = -1;
928 hp[-3].hash = -1;
929 hp[-2].hash = -1;
930 hp[-1].hash = -1;
931 hp[ 0].hash = -1;
932 hp -= 8;
933 } while (i >= 0);
934 for (i += 8; i > 0; i--, hp--)
935 hp->hash = -1;
936 }
937
938 static void
939 LZWCleanup(TIFF* tif)
940 {
941 if (tif->tif_data) {
942 if (tif->tif_mode == O_RDONLY) {
943 if (DecoderState(tif)->dec_codetab)
944 _TIFFfree(DecoderState(tif)->dec_codetab);
945 } else {
946 if (EncoderState(tif)->enc_hashtab)
947 _TIFFfree(EncoderState(tif)->enc_hashtab);
948 }
949 _TIFFfree(tif->tif_data);
950 tif->tif_data = NULL;
951 }
952 }
953
954 int
955 TIFFInitLZW(TIFF* tif, int scheme)
956 {
957 assert(scheme == COMPRESSION_LZW);
958 /*
959 * Allocate state block so tag methods have storage to record values.
960 */
961 if (tif->tif_mode == O_RDONLY) {
962 tif->tif_data = (tidata_t) _TIFFmalloc(sizeof (LZWDecodeState));
963 if (tif->tif_data == NULL)
964 goto bad;
965 DecoderState(tif)->dec_codetab = NULL;
966 DecoderState(tif)->dec_decode = NULL;
967 } else {
968 tif->tif_data = (tidata_t) _TIFFmalloc(sizeof (LZWEncodeState));
969 if (tif->tif_data == NULL)
970 goto bad;
971 EncoderState(tif)->enc_hashtab = NULL;
972 }
973 /*
974 * Install codec methods.
975 */
976 tif->tif_setupdecode = LZWSetupDecode;
977 tif->tif_predecode = LZWPreDecode;
978 tif->tif_decoderow = LZWDecode;
979 tif->tif_decodestrip = LZWDecode;
980 tif->tif_decodetile = LZWDecode;
981 tif->tif_setupencode = LZWSetupEncode;
982 tif->tif_preencode = LZWPreEncode;
983 tif->tif_postencode = LZWPostEncode;
984 tif->tif_encoderow = LZWEncode;
985 tif->tif_encodestrip = LZWEncode;
986 tif->tif_encodetile = LZWEncode;
987 tif->tif_cleanup = LZWCleanup;
988 /*
989 * Setup predictor setup.
990 */
991 (void) TIFFPredictorInit(tif);
992 return (1);
993 bad:
994 TIFFError("TIFFInitLZW", "No space for LZW state block");
995 return (0);
996 }
997
998 /*
999 * Copyright (c) 1985, 1986 The Regents of the University of California.
1000 * All rights reserved.
1001 *
1002 * This code is derived from software contributed to Berkeley by
1003 * James A. Woods, derived from original work by Spencer Thomas
1004 * and Joseph Orost.
1005 *
1006 * Redistribution and use in source and binary forms are permitted
1007 * provided that the above copyright notice and this paragraph are
1008 * duplicated in all such forms and that any documentation,
1009 * advertising materials, and other materials related to such
1010 * distribution and use acknowledge that the software was developed
1011 * by the University of California, Berkeley. The name of the
1012 * University may not be used to endorse or promote products derived
1013 * from this software without specific prior written permission.
1014 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
1015 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
1016 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
1017 */
1018 #endif /* LZW_SUPPORT */
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