1 /*
2 * Gif extracting routines - derived from libungif
3 *
4 * Portions Copyright 2006 Mike McCormack
5 *
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
19 */
20
21 /*
22 * Original copyright notice:
23 *
24 * The GIFLIB distribution is Copyright (c) 1997 Eric S. Raymond
25 *
26 * Permission is hereby granted, free of charge, to any person obtaining a copy
27 * of this software and associated documentation files (the "Software"), to deal
28 * in the Software without restriction, including without limitation the rights
29 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
30 * copies of the Software, and to permit persons to whom the Software is
31 * furnished to do so, subject to the following conditions:
32 *
33 * The above copyright notice and this permission notice shall be included in
34 * all copies or substantial portions of the Software.
35 */
36
37
38 /******************************************************************************
39 * "Gif-Lib" - Yet another gif library.
40 *
41 * Written by: Gershon Elber IBM PC Ver 1.1, Aug. 1990
42 ******************************************************************************
43 * The kernel of the GIF Decoding process can be found here.
44 ******************************************************************************
45 * History:
46 * 16 Jun 89 - Version 1.0 by Gershon Elber.
47 * 3 Sep 90 - Version 1.1 by Gershon Elber (Support for Gif89, Unique names).
48 *****************************************************************************/
49
50 #include <stdlib.h>
51 #include <string.h>
52 #include "ungif.h"
53
54 #include <stdarg.h>
55 #include "windef.h"
56 #include "winbase.h"
57
58 static void *ungif_alloc( size_t sz )
59 {
60 return HeapAlloc( GetProcessHeap(), 0, sz );
61 }
62
63 static void *ungif_calloc( size_t num, size_t sz )
64 {
65 return HeapAlloc( GetProcessHeap(), HEAP_ZERO_MEMORY, num*sz );
66 }
67
68 static void *ungif_realloc( void *ptr, size_t sz )
69 {
70 return HeapReAlloc( GetProcessHeap(), 0, ptr, sz );
71 }
72
73 static void ungif_free( void *ptr )
74 {
75 HeapFree( GetProcessHeap(), 0, ptr );
76 }
77
78 #define LZ_MAX_CODE 4095 /* Biggest code possible in 12 bits. */
79 #define LZ_BITS 12
80
81 #define NO_SUCH_CODE 4098 /* Impossible code, to signal empty. */
82
83 typedef struct GifFilePrivateType {
84 GifWord BitsPerPixel, /* Bits per pixel (Codes uses at least this + 1). */
85 ClearCode, /* The CLEAR LZ code. */
86 EOFCode, /* The EOF LZ code. */
87 RunningCode, /* The next code algorithm can generate. */
88 RunningBits, /* The number of bits required to represent RunningCode. */
89 MaxCode1, /* 1 bigger than max. possible code, in RunningBits bits. */
90 LastCode, /* The code before the current code. */
91 CrntCode, /* Current algorithm code. */
92 StackPtr, /* For character stack (see below). */
93 CrntShiftState; /* Number of bits in CrntShiftDWord. */
94 unsigned long CrntShiftDWord; /* For bytes decomposition into codes. */
95 unsigned long PixelCount; /* Number of pixels in image. */
96 InputFunc Read; /* function to read gif input (TVT) */
97 GifByteType Buf[256]; /* Compressed input is buffered here. */
98 GifByteType Stack[LZ_MAX_CODE]; /* Decoded pixels are stacked here. */
99 GifByteType Suffix[LZ_MAX_CODE + 1]; /* So we can trace the codes. */
100 GifPrefixType Prefix[LZ_MAX_CODE + 1];
101 } GifFilePrivateType;
102
103 /* avoid extra function call in case we use fread (TVT) */
104 #define READ(_gif,_buf,_len) \
105 ((GifFilePrivateType*)_gif->Private)->Read(_gif,_buf,_len)
106
107 static int DGifGetWord(GifFileType *GifFile, GifWord *Word);
108 static int DGifSetupDecompress(GifFileType *GifFile);
109 static int DGifDecompressLine(GifFileType *GifFile, GifPixelType *Line, int LineLen);
110 static int DGifGetPrefixChar(const GifPrefixType *Prefix, int Code, int ClearCode);
111 static int DGifDecompressInput(GifFileType *GifFile, int *Code);
112 static int DGifBufferedInput(GifFileType *GifFile, GifByteType *Buf,
113 GifByteType *NextByte);
114
115 static int DGifGetExtensionNext(GifFileType * GifFile, GifByteType ** GifExtension);
116 static int DGifGetCodeNext(GifFileType * GifFile, GifByteType ** GifCodeBlock);
117
118 /******************************************************************************
119 * Miscellaneous utility functions
120 *****************************************************************************/
121
122 /* return smallest bitfield size n will fit in */
123 static int
124 BitSize(int n) {
125
126 register int i;
127
128 for (i = 1; i <= 8; i++)
129 if ((1 << i) >= n)
130 break;
131 return (i);
132 }
133
134 /******************************************************************************
135 * Color map object functions
136 *****************************************************************************/
137
138 /*
139 * Allocate a color map of given size; initialize with contents of
140 * ColorMap if that pointer is non-NULL.
141 */
142 static ColorMapObject *
143 MakeMapObject(int ColorCount,
144 const GifColorType * ColorMap) {
145
146 ColorMapObject *Object;
147
148 /*** FIXME: Our ColorCount has to be a power of two. Is it necessary to
149 * make the user know that or should we automatically round up instead? */
150 if (ColorCount != (1 << BitSize(ColorCount))) {
151 return ((ColorMapObject *) NULL);
152 }
153
154 Object = ungif_alloc(sizeof(ColorMapObject));
155 if (Object == (ColorMapObject *) NULL) {
156 return ((ColorMapObject *) NULL);
157 }
158
159 Object->Colors = ungif_calloc(ColorCount, sizeof(GifColorType));
160 if (Object->Colors == (GifColorType *) NULL) {
161 return NULL;
162 }
163
164 Object->ColorCount = ColorCount;
165 Object->BitsPerPixel = BitSize(ColorCount);
166
167 if (ColorMap) {
168 memcpy(Object->Colors, ColorMap, ColorCount * sizeof(GifColorType));
169 }
170
171 return (Object);
172 }
173
174 /*
175 * Free a color map object
176 */
177 static void
178 FreeMapObject(ColorMapObject * Object) {
179
180 if (Object != NULL) {
181 ungif_free(Object->Colors);
182 ungif_free(Object);
183 /*** FIXME:
184 * When we are willing to break API we need to make this function
185 * FreeMapObject(ColorMapObject **Object)
186 * and do this assignment to NULL here:
187 * *Object = NULL;
188 */
189 }
190 }
191
192 static int
193 AddExtensionBlock(SavedImage * New,
194 int Len,
195 const unsigned char ExtData[]) {
196
197 ExtensionBlock *ep;
198
199 if (New->ExtensionBlocks == NULL)
200 New->ExtensionBlocks = ungif_alloc(sizeof(ExtensionBlock));
201 else
202 New->ExtensionBlocks = ungif_realloc(New->ExtensionBlocks,
203 sizeof(ExtensionBlock) *
204 (New->ExtensionBlockCount + 1));
205
206 if (New->ExtensionBlocks == NULL)
207 return (GIF_ERROR);
208
209 ep = &New->ExtensionBlocks[New->ExtensionBlockCount++];
210
211 ep->ByteCount=Len;
212 ep->Bytes = ungif_alloc(ep->ByteCount);
213 if (ep->Bytes == NULL)
214 return (GIF_ERROR);
215
216 if (ExtData) {
217 memcpy(ep->Bytes, ExtData, Len);
218 ep->Function = New->Function;
219 }
220
221 return (GIF_OK);
222 }
223
224 static void
225 FreeExtension(SavedImage * Image)
226 {
227 ExtensionBlock *ep;
228
229 if ((Image == NULL) || (Image->ExtensionBlocks == NULL)) {
230 return;
231 }
232 for (ep = Image->ExtensionBlocks;
233 ep < (Image->ExtensionBlocks + Image->ExtensionBlockCount); ep++)
234 ungif_free(ep->Bytes);
235 ungif_free(Image->ExtensionBlocks);
236 Image->ExtensionBlocks = NULL;
237 }
238
239 /******************************************************************************
240 * Image block allocation functions
241 ******************************************************************************/
242
243 static void
244 FreeSavedImages(GifFileType * GifFile) {
245
246 SavedImage *sp;
247
248 if ((GifFile == NULL) || (GifFile->SavedImages == NULL)) {
249 return;
250 }
251 for (sp = GifFile->SavedImages;
252 sp < GifFile->SavedImages + GifFile->ImageCount; sp++) {
253 if (sp->ImageDesc.ColorMap) {
254 FreeMapObject(sp->ImageDesc.ColorMap);
255 sp->ImageDesc.ColorMap = NULL;
256 }
257
258 ungif_free(sp->RasterBits);
259
260 if (sp->ExtensionBlocks)
261 FreeExtension(sp);
262 }
263 ungif_free(GifFile->SavedImages);
264 GifFile->SavedImages=NULL;
265 }
266
267 /******************************************************************************
268 * This routine should be called before any other DGif calls. Note that
269 * this routine is called automatically from DGif file open routines.
270 *****************************************************************************/
271 static int
272 DGifGetScreenDesc(GifFileType * GifFile) {
273
274 int i, BitsPerPixel;
275 GifByteType Buf[3];
276
277 /* Put the screen descriptor into the file: */
278 if (DGifGetWord(GifFile, &GifFile->SWidth) == GIF_ERROR ||
279 DGifGetWord(GifFile, &GifFile->SHeight) == GIF_ERROR)
280 return GIF_ERROR;
281
282 if (READ(GifFile, Buf, 3) != 3) {
283 return GIF_ERROR;
284 }
285 GifFile->SColorResolution = (((Buf[0] & 0x70) + 1) >> 4) + 1;
286 BitsPerPixel = (Buf[0] & 0x07) + 1;
287 GifFile->SBackGroundColor = Buf[1];
288 if (Buf[0] & 0x80) { /* Do we have global color map? */
289
290 GifFile->SColorMap = MakeMapObject(1 << BitsPerPixel, NULL);
291 if (GifFile->SColorMap == NULL) {
292 return GIF_ERROR;
293 }
294
295 /* Get the global color map: */
296 for (i = 0; i < GifFile->SColorMap->ColorCount; i++) {
297 if (READ(GifFile, Buf, 3) != 3) {
298 FreeMapObject(GifFile->SColorMap);
299 GifFile->SColorMap = NULL;
300 return GIF_ERROR;
301 }
302 GifFile->SColorMap->Colors[i].Red = Buf[0];
303 GifFile->SColorMap->Colors[i].Green = Buf[1];
304 GifFile->SColorMap->Colors[i].Blue = Buf[2];
305 }
306 } else {
307 GifFile->SColorMap = NULL;
308 }
309
310 return GIF_OK;
311 }
312
313 /******************************************************************************
314 * This routine should be called before any attempt to read an image.
315 *****************************************************************************/
316 static int
317 DGifGetRecordType(GifFileType * GifFile,
318 GifRecordType * Type) {
319
320 GifByteType Buf;
321
322 if (READ(GifFile, &Buf, 1) != 1) {
323 return GIF_ERROR;
324 }
325
326 switch (Buf) {
327 case ',':
328 *Type = IMAGE_DESC_RECORD_TYPE;
329 break;
330 case '!':
331 *Type = EXTENSION_RECORD_TYPE;
332 break;
333 case ';':
334 *Type = TERMINATE_RECORD_TYPE;
335 break;
336 default:
337 *Type = UNDEFINED_RECORD_TYPE;
338 return GIF_ERROR;
339 }
340
341 return GIF_OK;
342 }
343
344 /******************************************************************************
345 * This routine should be called before any attempt to read an image.
346 * Note it is assumed the Image desc. header (',') has been read.
347 *****************************************************************************/
348 static int
349 DGifGetImageDesc(GifFileType * GifFile) {
350
351 int i, BitsPerPixel;
352 GifByteType Buf[3];
353 GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;
354 SavedImage *sp;
355
356 if (DGifGetWord(GifFile, &GifFile->Image.Left) == GIF_ERROR ||
357 DGifGetWord(GifFile, &GifFile->Image.Top) == GIF_ERROR ||
358 DGifGetWord(GifFile, &GifFile->Image.Width) == GIF_ERROR ||
359 DGifGetWord(GifFile, &GifFile->Image.Height) == GIF_ERROR)
360 return GIF_ERROR;
361 if (READ(GifFile, Buf, 1) != 1) {
362 return GIF_ERROR;
363 }
364 BitsPerPixel = (Buf[0] & 0x07) + 1;
365 GifFile->Image.Interlace = (Buf[0] & 0x40);
366 if (Buf[0] & 0x80) { /* Does this image have local color map? */
367
368 /*** FIXME: Why do we check both of these in order to do this?
369 * Why do we have both Image and SavedImages? */
370 if (GifFile->Image.ColorMap && GifFile->SavedImages == NULL)
371 FreeMapObject(GifFile->Image.ColorMap);
372
373 GifFile->Image.ColorMap = MakeMapObject(1 << BitsPerPixel, NULL);
374 if (GifFile->Image.ColorMap == NULL) {
375 return GIF_ERROR;
376 }
377
378 /* Get the image local color map: */
379 for (i = 0; i < GifFile->Image.ColorMap->ColorCount; i++) {
380 if (READ(GifFile, Buf, 3) != 3) {
381 FreeMapObject(GifFile->Image.ColorMap);
382 GifFile->Image.ColorMap = NULL;
383 return GIF_ERROR;
384 }
385 GifFile->Image.ColorMap->Colors[i].Red = Buf[0];
386 GifFile->Image.ColorMap->Colors[i].Green = Buf[1];
387 GifFile->Image.ColorMap->Colors[i].Blue = Buf[2];
388 }
389 } else if (GifFile->Image.ColorMap) {
390 FreeMapObject(GifFile->Image.ColorMap);
391 GifFile->Image.ColorMap = NULL;
392 }
393
394 if (GifFile->SavedImages) {
395 if ((GifFile->SavedImages = ungif_realloc(GifFile->SavedImages,
396 sizeof(SavedImage) *
397 (GifFile->ImageCount + 1))) == NULL) {
398 return GIF_ERROR;
399 }
400 } else {
401 if ((GifFile->SavedImages = ungif_alloc(sizeof(SavedImage))) == NULL) {
402 return GIF_ERROR;
403 }
404 }
405
406 sp = &GifFile->SavedImages[GifFile->ImageCount];
407 sp->ImageDesc = GifFile->Image;
408 if (GifFile->Image.ColorMap != NULL) {
409 sp->ImageDesc.ColorMap = MakeMapObject(
410 GifFile->Image.ColorMap->ColorCount,
411 GifFile->Image.ColorMap->Colors);
412 if (sp->ImageDesc.ColorMap == NULL) {
413 return GIF_ERROR;
414 }
415 }
416 sp->RasterBits = (unsigned char *)NULL;
417 sp->ExtensionBlockCount = 0;
418 sp->ExtensionBlocks = (ExtensionBlock *) NULL;
419
420 GifFile->ImageCount++;
421
422 Private->PixelCount = (long)GifFile->Image.Width *
423 (long)GifFile->Image.Height;
424
425 DGifSetupDecompress(GifFile); /* Reset decompress algorithm parameters. */
426
427 return GIF_OK;
428 }
429
430 /******************************************************************************
431 * Get one full scanned line (Line) of length LineLen from GIF file.
432 *****************************************************************************/
433 static int
434 DGifGetLine(GifFileType * GifFile,
435 GifPixelType * Line,
436 int LineLen) {
437
438 GifByteType *Dummy;
439 GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;
440
441 if (!LineLen)
442 LineLen = GifFile->Image.Width;
443
444 if ((Private->PixelCount -= LineLen) > 0xffff0000UL) {
445 return GIF_ERROR;
446 }
447
448 if (DGifDecompressLine(GifFile, Line, LineLen) == GIF_OK) {
449 if (Private->PixelCount == 0) {
450 /* We probably would not be called any more, so lets clean
451 * everything before we return: need to flush out all rest of
452 * image until empty block (size 0) detected. We use GetCodeNext. */
453 do
454 if (DGifGetCodeNext(GifFile, &Dummy) == GIF_ERROR)
455 return GIF_ERROR;
456 while (Dummy != NULL) ;
457 }
458 return GIF_OK;
459 } else
460 return GIF_ERROR;
461 }
462
463 /******************************************************************************
464 * Get an extension block (see GIF manual) from gif file. This routine only
465 * returns the first data block, and DGifGetExtensionNext should be called
466 * after this one until NULL extension is returned.
467 * The Extension should NOT be freed by the user (not dynamically allocated).
468 * Note it is assumed the Extension desc. header ('!') has been read.
469 *****************************************************************************/
470 static int
471 DGifGetExtension(GifFileType * GifFile,
472 int *ExtCode,
473 GifByteType ** Extension) {
474
475 GifByteType Buf;
476
477 if (READ(GifFile, &Buf, 1) != 1) {
478 return GIF_ERROR;
479 }
480 *ExtCode = Buf;
481
482 return DGifGetExtensionNext(GifFile, Extension);
483 }
484
485 /******************************************************************************
486 * Get a following extension block (see GIF manual) from gif file. This
487 * routine should be called until NULL Extension is returned.
488 * The Extension should NOT be freed by the user (not dynamically allocated).
489 *****************************************************************************/
490 static int
491 DGifGetExtensionNext(GifFileType * GifFile,
492 GifByteType ** Extension) {
493
494 GifByteType Buf;
495 GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;
496
497 if (READ(GifFile, &Buf, 1) != 1) {
498 return GIF_ERROR;
499 }
500 if (Buf > 0) {
501 *Extension = Private->Buf; /* Use private unused buffer. */
502 (*Extension)[0] = Buf; /* Pascal strings notation (pos. 0 is len.). */
503 if (READ(GifFile, &((*Extension)[1]), Buf) != Buf) {
504 return GIF_ERROR;
505 }
506 } else
507 *Extension = NULL;
508
509 return GIF_OK;
510 }
511
512 /******************************************************************************
513 * Get 2 bytes (word) from the given file:
514 *****************************************************************************/
515 static int
516 DGifGetWord(GifFileType * GifFile,
517 GifWord *Word) {
518
519 unsigned char c[2];
520
521 if (READ(GifFile, c, 2) != 2) {
522 return GIF_ERROR;
523 }
524
525 *Word = (((unsigned int)c[1]) << 8) + c[0];
526 return GIF_OK;
527 }
528
529 /******************************************************************************
530 * Continue to get the image code in compressed form. This routine should be
531 * called until NULL block is returned.
532 * The block should NOT be freed by the user (not dynamically allocated).
533 *****************************************************************************/
534 static int
535 DGifGetCodeNext(GifFileType * GifFile,
536 GifByteType ** CodeBlock) {
537
538 GifByteType Buf;
539 GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;
540
541 if (READ(GifFile, &Buf, 1) != 1) {
542 return GIF_ERROR;
543 }
544
545 if (Buf > 0) {
546 *CodeBlock = Private->Buf; /* Use private unused buffer. */
547 (*CodeBlock)[0] = Buf; /* Pascal strings notation (pos. 0 is len.). */
548 if (READ(GifFile, &((*CodeBlock)[1]), Buf) != Buf) {
549 return GIF_ERROR;
550 }
551 } else {
552 *CodeBlock = NULL;
553 Private->Buf[0] = 0; /* Make sure the buffer is empty! */
554 Private->PixelCount = 0; /* And local info. indicate image read. */
555 }
556
557 return GIF_OK;
558 }
559
560 /******************************************************************************
561 * Setup the LZ decompression for this image:
562 *****************************************************************************/
563 static int
564 DGifSetupDecompress(GifFileType * GifFile) {
565
566 int i, BitsPerPixel;
567 GifByteType CodeSize;
568 GifPrefixType *Prefix;
569 GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;
570
571 READ(GifFile, &CodeSize, 1); /* Read Code size from file. */
572 BitsPerPixel = CodeSize;
573
574 Private->Buf[0] = 0; /* Input Buffer empty. */
575 Private->BitsPerPixel = BitsPerPixel;
576 Private->ClearCode = (1 << BitsPerPixel);
577 Private->EOFCode = Private->ClearCode + 1;
578 Private->RunningCode = Private->EOFCode + 1;
579 Private->RunningBits = BitsPerPixel + 1; /* Number of bits per code. */
580 Private->MaxCode1 = 1 << Private->RunningBits; /* Max. code + 1. */
581 Private->StackPtr = 0; /* No pixels on the pixel stack. */
582 Private->LastCode = NO_SUCH_CODE;
583 Private->CrntShiftState = 0; /* No information in CrntShiftDWord. */
584 Private->CrntShiftDWord = 0;
585
586 Prefix = Private->Prefix;
587 for (i = 0; i <= LZ_MAX_CODE; i++)
588 Prefix[i] = NO_SUCH_CODE;
589
590 return GIF_OK;
591 }
592
593 /******************************************************************************
594 * The LZ decompression routine:
595 * This version decompress the given gif file into Line of length LineLen.
596 * This routine can be called few times (one per scan line, for example), in
597 * order the complete the whole image.
598 *****************************************************************************/
599 static int
600 DGifDecompressLine(GifFileType * GifFile,
601 GifPixelType * Line,
602 int LineLen) {
603
604 int i = 0;
605 int j, CrntCode, EOFCode, ClearCode, CrntPrefix, LastCode, StackPtr;
606 GifByteType *Stack, *Suffix;
607 GifPrefixType *Prefix;
608 GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;
609
610 StackPtr = Private->StackPtr;
611 Prefix = Private->Prefix;
612 Suffix = Private->Suffix;
613 Stack = Private->Stack;
614 EOFCode = Private->EOFCode;
615 ClearCode = Private->ClearCode;
616 LastCode = Private->LastCode;
617
618 if (StackPtr != 0) {
619 /* Let pop the stack off before continuing to read the gif file: */
620 while (StackPtr != 0 && i < LineLen)
621 Line[i++] = Stack[--StackPtr];
622 }
623
624 while (i < LineLen) { /* Decode LineLen items. */
625 if (DGifDecompressInput(GifFile, &CrntCode) == GIF_ERROR)
626 return GIF_ERROR;
627
628 if (CrntCode == EOFCode) {
629 /* Note, however, that usually we will not be here as we will stop
630 * decoding as soon as we got all the pixel, or EOF code will
631 * not be read at all, and DGifGetLine/Pixel clean everything. */
632 if (i != LineLen - 1 || Private->PixelCount != 0) {
633 return GIF_ERROR;
634 }
635 i++;
636 } else if (CrntCode == ClearCode) {
637 /* We need to start over again: */
638 for (j = 0; j <= LZ_MAX_CODE; j++)
639 Prefix[j] = NO_SUCH_CODE;
640 Private->RunningCode = Private->EOFCode + 1;
641 Private->RunningBits = Private->BitsPerPixel + 1;
642 Private->MaxCode1 = 1 << Private->RunningBits;
643 LastCode = Private->LastCode = NO_SUCH_CODE;
644 } else {
645 /* It's a regular code - if in pixel range simply add it to output
646 * stream, otherwise trace to codes linked list until the prefix
647 * is in pixel range: */
648 if (CrntCode < ClearCode) {
649 /* This is simple - its pixel scalar, so add it to output: */
650 Line[i++] = CrntCode;
651 } else {
652 /* It's a code to be traced: trace the linked list
653 * until the prefix is a pixel, while pushing the suffix
654 * pixels on our stack. If we done, pop the stack in reverse
655 * order (that's what stack is good for!) for output. */
656 if (Prefix[CrntCode] == NO_SUCH_CODE) {
657 /* Only allowed if CrntCode is exactly the running code:
658 * In that case CrntCode = XXXCode, CrntCode or the
659 * prefix code is last code and the suffix char is
660 * exactly the prefix of last code! */
661 if (CrntCode == Private->RunningCode - 2) {
662 CrntPrefix = LastCode;
663 Suffix[Private->RunningCode - 2] =
664 Stack[StackPtr++] = DGifGetPrefixChar(Prefix,
665 LastCode,
666 ClearCode);
667 } else {
668 return GIF_ERROR;
669 }
670 } else
671 CrntPrefix = CrntCode;
672
673 /* Now (if image is O.K.) we should not get a NO_SUCH_CODE
674 * during the trace. As we might loop forever, in case of
675 * defective image, we count the number of loops we trace
676 * and stop if we got LZ_MAX_CODE. Obviously we cannot
677 * loop more than that. */
678 j = 0;
679 while (j++ <= LZ_MAX_CODE &&
680 CrntPrefix > ClearCode && CrntPrefix <= LZ_MAX_CODE) {
681 Stack[StackPtr++] = Suffix[CrntPrefix];
682 CrntPrefix = Prefix[CrntPrefix];
683 }
684 if (j >= LZ_MAX_CODE || CrntPrefix > LZ_MAX_CODE) {
685 return GIF_ERROR;
686 }
687 /* Push the last character on stack: */
688 Stack[StackPtr++] = CrntPrefix;
689
690 /* Now lets pop all the stack into output: */
691 while (StackPtr != 0 && i < LineLen)
692 Line[i++] = Stack[--StackPtr];
693 }
694 if (LastCode != NO_SUCH_CODE) {
695 Prefix[Private->RunningCode - 2] = LastCode;
696
697 if (CrntCode == Private->RunningCode - 2) {
698 /* Only allowed if CrntCode is exactly the running code:
699 * In that case CrntCode = XXXCode, CrntCode or the
700 * prefix code is last code and the suffix char is
701 * exactly the prefix of last code! */
702 Suffix[Private->RunningCode - 2] =
703 DGifGetPrefixChar(Prefix, LastCode, ClearCode);
704 } else {
705 Suffix[Private->RunningCode - 2] =
706 DGifGetPrefixChar(Prefix, CrntCode, ClearCode);
707 }
708 }
709 LastCode = CrntCode;
710 }
711 }
712
713 Private->LastCode = LastCode;
714 Private->StackPtr = StackPtr;
715
716 return GIF_OK;
717 }
718
719 /******************************************************************************
720 * Routine to trace the Prefixes linked list until we get a prefix which is
721 * not code, but a pixel value (less than ClearCode). Returns that pixel value.
722 * If image is defective, we might loop here forever, so we limit the loops to
723 * the maximum possible if image O.k. - LZ_MAX_CODE times.
724 *****************************************************************************/
725 static int
726 DGifGetPrefixChar(const GifPrefixType *Prefix,
727 int Code,
728 int ClearCode) {
729
730 int i = 0;
731
732 while (Code > ClearCode && i++ <= LZ_MAX_CODE)
733 Code = Prefix[Code];
734 return Code;
735 }
736
737 /******************************************************************************
738 * The LZ decompression input routine:
739 * This routine is responsible for the decompression of the bit stream from
740 * 8 bits (bytes) packets, into the real codes.
741 * Returns GIF_OK if read successfully.
742 *****************************************************************************/
743 static int
744 DGifDecompressInput(GifFileType * GifFile,
745 int *Code) {
746
747 GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;
748
749 GifByteType NextByte;
750 static const unsigned short CodeMasks[] = {
751 0x0000, 0x0001, 0x0003, 0x0007,
752 0x000f, 0x001f, 0x003f, 0x007f,
753 0x00ff, 0x01ff, 0x03ff, 0x07ff,
754 0x0fff
755 };
756 /* The image can't contain more than LZ_BITS per code. */
757 if (Private->RunningBits > LZ_BITS) {
758 return GIF_ERROR;
759 }
760
761 while (Private->CrntShiftState < Private->RunningBits) {
762 /* Needs to get more bytes from input stream for next code: */
763 if (DGifBufferedInput(GifFile, Private->Buf, &NextByte) == GIF_ERROR) {
764 return GIF_ERROR;
765 }
766 Private->CrntShiftDWord |=
767 ((unsigned long)NextByte) << Private->CrntShiftState;
768 Private->CrntShiftState += 8;
769 }
770 *Code = Private->CrntShiftDWord & CodeMasks[Private->RunningBits];
771
772 Private->CrntShiftDWord >>= Private->RunningBits;
773 Private->CrntShiftState -= Private->RunningBits;
774
775 /* If code cannot fit into RunningBits bits, must raise its size. Note
776 * however that codes above 4095 are used for special signaling.
777 * If we're using LZ_BITS bits already and we're at the max code, just
778 * keep using the table as it is, don't increment Private->RunningCode.
779 */
780 if (Private->RunningCode < LZ_MAX_CODE + 2 &&
781 ++Private->RunningCode > Private->MaxCode1 &&
782 Private->RunningBits < LZ_BITS) {
783 Private->MaxCode1 <<= 1;
784 Private->RunningBits++;
785 }
786 return GIF_OK;
787 }
788
789 /******************************************************************************
790 * This routines read one gif data block at a time and buffers it internally
791 * so that the decompression routine could access it.
792 * The routine returns the next byte from its internal buffer (or read next
793 * block in if buffer empty) and returns GIF_OK if successful.
794 *****************************************************************************/
795 static int
796 DGifBufferedInput(GifFileType * GifFile,
797 GifByteType * Buf,
798 GifByteType * NextByte) {
799
800 if (Buf[0] == 0) {
801 /* Needs to read the next buffer - this one is empty: */
802 if (READ(GifFile, Buf, 1) != 1) {
803 return GIF_ERROR;
804 }
805 /* There shouldn't be any empty data blocks here as the LZW spec
806 * says the LZW termination code should come first. Therefore we
807 * shouldn't be inside this routine at that point.
808 */
809 if (Buf[0] == 0) {
810 return GIF_ERROR;
811 }
812 if (READ(GifFile, &Buf[1], Buf[0]) != Buf[0]) {
813 return GIF_ERROR;
814 }
815 *NextByte = Buf[1];
816 Buf[1] = 2; /* We use now the second place as last char read! */
817 Buf[0]--;
818 } else {
819 *NextByte = Buf[Buf[1]++];
820 Buf[0]--;
821 }
822
823 return GIF_OK;
824 }
825
826 /******************************************************************************
827 * This routine reads an entire GIF into core, hanging all its state info off
828 * the GifFileType pointer. Call DGifOpenFileName() or DGifOpenFileHandle()
829 * first to initialize I/O. Its inverse is EGifSpew().
830 ******************************************************************************/
831 int
832 DGifSlurp(GifFileType * GifFile) {
833
834 int ImageSize;
835 GifRecordType RecordType;
836 SavedImage *sp;
837 GifByteType *ExtData;
838 SavedImage temp_save;
839
840 temp_save.ExtensionBlocks = NULL;
841 temp_save.ExtensionBlockCount = 0;
842
843 do {
844 if (DGifGetRecordType(GifFile, &RecordType) == GIF_ERROR)
845 return (GIF_ERROR);
846
847 switch (RecordType) {
848 case IMAGE_DESC_RECORD_TYPE:
849 if (DGifGetImageDesc(GifFile) == GIF_ERROR)
850 return (GIF_ERROR);
851
852 sp = &GifFile->SavedImages[GifFile->ImageCount - 1];
853 ImageSize = sp->ImageDesc.Width * sp->ImageDesc.Height;
854
855 sp->RasterBits = ungif_alloc(ImageSize * sizeof(GifPixelType));
856 if (sp->RasterBits == NULL) {
857 return GIF_ERROR;
858 }
859 if (DGifGetLine(GifFile, sp->RasterBits, ImageSize) ==
860 GIF_ERROR)
861 return (GIF_ERROR);
862 if (temp_save.ExtensionBlocks) {
863 sp->ExtensionBlocks = temp_save.ExtensionBlocks;
864 sp->ExtensionBlockCount = temp_save.ExtensionBlockCount;
865
866 temp_save.ExtensionBlocks = NULL;
867 temp_save.ExtensionBlockCount = 0;
868
869 /* FIXME: The following is wrong. It is left in only for
870 * backwards compatibility. Someday it should go away. Use
871 * the sp->ExtensionBlocks->Function variable instead. */
872 sp->Function = sp->ExtensionBlocks[0].Function;
873 }
874 break;
875
876 case EXTENSION_RECORD_TYPE:
877 if (DGifGetExtension(GifFile, &temp_save.Function, &ExtData) ==
878 GIF_ERROR)
879 return (GIF_ERROR);
880 while (ExtData != NULL) {
881
882 /* Create an extension block with our data */
883 if (AddExtensionBlock(&temp_save, ExtData[0], &ExtData[1])
884 == GIF_ERROR)
885 return (GIF_ERROR);
886
887 if (DGifGetExtensionNext(GifFile, &ExtData) == GIF_ERROR)
888 return (GIF_ERROR);
889 temp_save.Function = 0;
890 }
891 break;
892
893 case TERMINATE_RECORD_TYPE:
894 break;
895
896 default: /* Should be trapped by DGifGetRecordType */
897 break;
898 }
899 } while (RecordType != TERMINATE_RECORD_TYPE);
900
901 /* Just in case the Gif has an extension block without an associated
902 * image... (Should we save this into a savefile structure with no image
903 * instead? Have to check if the present writing code can handle that as
904 * well.... */
905 if (temp_save.ExtensionBlocks)
906 FreeExtension(&temp_save);
907
908 return (GIF_OK);
909 }
910
911 /******************************************************************************
912 * GifFileType constructor with user supplied input function (TVT)
913 *****************************************************************************/
914 GifFileType *
915 DGifOpen(void *userData,
916 InputFunc readFunc) {
917
918 unsigned char Buf[GIF_STAMP_LEN + 1];
919 GifFileType *GifFile;
920 GifFilePrivateType *Private;
921
922 GifFile = ungif_alloc(sizeof(GifFileType));
923 if (GifFile == NULL) {
924 return NULL;
925 }
926
927 memset(GifFile, '\0', sizeof(GifFileType));
928
929 Private = ungif_alloc(sizeof(GifFilePrivateType));
930 if (!Private) {
931 ungif_free(GifFile);
932 return NULL;
933 }
934
935 GifFile->Private = (void*)Private;
936
937 Private->Read = readFunc; /* TVT */
938 GifFile->UserData = userData; /* TVT */
939
940 /* Lets see if this is a GIF file: */
941 if (READ(GifFile, Buf, GIF_STAMP_LEN) != GIF_STAMP_LEN) {
942 ungif_free(Private);
943 ungif_free(GifFile);
944 return NULL;
945 }
946
947 /* The GIF Version number is ignored at this time. Maybe we should do
948 * something more useful with it. */
949 Buf[GIF_STAMP_LEN] = 0;
950 if (memcmp(GIF_STAMP, Buf, GIF_VERSION_POS) != 0) {
951 ungif_free(Private);
952 ungif_free(GifFile);
953 return NULL;
954 }
955
956 if (DGifGetScreenDesc(GifFile) == GIF_ERROR) {
957 ungif_free(Private);
958 ungif_free(GifFile);
959 return NULL;
960 }
961
962 return GifFile;
963 }
964
965 /******************************************************************************
966 * This routine should be called last, to close the GIF file.
967 *****************************************************************************/
968 int
969 DGifCloseFile(GifFileType * GifFile) {
970
971 GifFilePrivateType *Private;
972
973 if (GifFile == NULL)
974 return GIF_ERROR;
975
976 Private = (GifFilePrivateType *) GifFile->Private;
977
978 if (GifFile->Image.ColorMap) {
979 FreeMapObject(GifFile->Image.ColorMap);
980 GifFile->Image.ColorMap = NULL;
981 }
982
983 if (GifFile->SColorMap) {
984 FreeMapObject(GifFile->SColorMap);
985 GifFile->SColorMap = NULL;
986 }
987
988 ungif_free(Private);
989 Private = NULL;
990
991 if (GifFile->SavedImages) {
992 FreeSavedImages(GifFile);
993 GifFile->SavedImages = NULL;
994 }
995
996 ungif_free(GifFile);
997
998 return GIF_OK;
999 }
1000
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