2 * Gif extracting routines - derived from libungif
4 * Portions Copyright 2006 Mike McCormack
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.
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.
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
22 * Original copyright notice:
24 * The GIFLIB distribution is Copyright (c) 1997 Eric S. Raymond
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:
33 * The above copyright notice and this permission notice shall be included in
34 * all copies or substantial portions of the Software.
38 /******************************************************************************
39 * "Gif-Lib" - Yet another gif library.
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 ******************************************************************************
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 *****************************************************************************/
59 static void *ungif_alloc( size_t sz
)
61 return HeapAlloc( GetProcessHeap(), 0, sz
);
64 static void *ungif_calloc( size_t num
, size_t sz
)
66 return HeapAlloc( GetProcessHeap(), HEAP_ZERO_MEMORY
, num
*sz
);
69 static void *ungif_realloc( void *ptr
, size_t sz
)
71 return HeapReAlloc( GetProcessHeap(), 0, ptr
, sz
);
74 static void ungif_free( void *ptr
)
76 HeapFree( GetProcessHeap(), 0, ptr
);
79 #define LZ_MAX_CODE 4095 /* Biggest code possible in 12 bits. */
82 #define NO_SUCH_CODE 4098 /* Impossible code, to signal empty. */
84 typedef struct GifFilePrivateType
{
85 GifWord BitsPerPixel
, /* Bits per pixel (Codes uses at least this + 1). */
86 ClearCode
, /* The CLEAR LZ code. */
87 EOFCode
, /* The EOF LZ code. */
88 RunningCode
, /* The next code algorithm can generate. */
89 RunningBits
, /* The number of bits required to represent RunningCode. */
90 MaxCode1
, /* 1 bigger than max. possible code, in RunningBits bits. */
91 LastCode
, /* The code before the current code. */
92 CrntCode
, /* Current algorithm code. */
93 StackPtr
, /* For character stack (see below). */
94 CrntShiftState
; /* Number of bits in CrntShiftDWord. */
95 unsigned long CrntShiftDWord
; /* For bytes decomposition into codes. */
96 unsigned long PixelCount
; /* Number of pixels in image. */
97 InputFunc Read
; /* function to read gif input (TVT) */
98 GifByteType Buf
[256]; /* Compressed input is buffered here. */
99 GifByteType Stack
[LZ_MAX_CODE
]; /* Decoded pixels are stacked here. */
100 GifByteType Suffix
[LZ_MAX_CODE
+ 1]; /* So we can trace the codes. */
101 GifPrefixType Prefix
[LZ_MAX_CODE
+ 1];
102 } GifFilePrivateType
;
104 /* avoid extra function call in case we use fread (TVT) */
105 #define READ(_gif,_buf,_len) \
106 ((GifFilePrivateType*)_gif->Private)->Read(_gif,_buf,_len)
108 static int DGifGetWord(GifFileType
*GifFile
, GifWord
*Word
);
109 static int DGifSetupDecompress(GifFileType
*GifFile
);
110 static int DGifDecompressLine(GifFileType
*GifFile
, GifPixelType
*Line
, int LineLen
);
111 static int DGifGetPrefixChar(const GifPrefixType
*Prefix
, int Code
, int ClearCode
);
112 static int DGifDecompressInput(GifFileType
*GifFile
, int *Code
);
113 static int DGifBufferedInput(GifFileType
*GifFile
, GifByteType
*Buf
,
114 GifByteType
*NextByte
);
116 static int DGifGetExtensionNext(GifFileType
* GifFile
, GifByteType
** GifExtension
);
117 static int DGifGetCodeNext(GifFileType
* GifFile
, GifByteType
** GifCodeBlock
);
119 /******************************************************************************
120 * Miscellaneous utility functions
121 *****************************************************************************/
123 /* return smallest bitfield size n will fit in */
129 for (i
= 1; i
<= 8; i
++)
135 /******************************************************************************
136 * Color map object functions
137 *****************************************************************************/
140 * Allocate a color map of given size; initialize with contents of
141 * ColorMap if that pointer is non-NULL.
143 static ColorMapObject
*
144 MakeMapObject(int ColorCount
,
145 const GifColorType
* ColorMap
) {
147 ColorMapObject
*Object
;
149 /*** FIXME: Our ColorCount has to be a power of two. Is it necessary to
150 * make the user know that or should we automatically round up instead? */
151 if (ColorCount
!= (1 << BitSize(ColorCount
))) {
155 Object
= ungif_alloc(sizeof(ColorMapObject
));
156 if (Object
== NULL
) {
160 Object
->Colors
= ungif_calloc(ColorCount
, sizeof(GifColorType
));
161 if (Object
->Colors
== NULL
) {
165 Object
->ColorCount
= ColorCount
;
166 Object
->BitsPerPixel
= BitSize(ColorCount
);
169 memcpy(Object
->Colors
, ColorMap
, ColorCount
* sizeof(GifColorType
));
176 * Free a color map object
179 FreeMapObject(ColorMapObject
* Object
) {
181 if (Object
!= NULL
) {
182 ungif_free(Object
->Colors
);
185 * When we are willing to break API we need to make this function
186 * FreeMapObject(ColorMapObject **Object)
187 * and do this assignment to NULL here:
194 AddExtensionBlock(SavedImage
* New
,
196 const unsigned char ExtData
[]) {
200 if (New
->ExtensionBlocks
== NULL
)
201 New
->ExtensionBlocks
= ungif_alloc(sizeof(ExtensionBlock
));
203 New
->ExtensionBlocks
= ungif_realloc(New
->ExtensionBlocks
,
204 sizeof(ExtensionBlock
) *
205 (New
->ExtensionBlockCount
+ 1));
207 if (New
->ExtensionBlocks
== NULL
)
210 ep
= &New
->ExtensionBlocks
[New
->ExtensionBlockCount
++];
213 ep
->Bytes
= ungif_alloc(ep
->ByteCount
);
214 if (ep
->Bytes
== NULL
)
218 memcpy(ep
->Bytes
, ExtData
, Len
);
219 ep
->Function
= New
->Function
;
226 FreeExtension(SavedImage
* Image
)
230 if ((Image
== NULL
) || (Image
->ExtensionBlocks
== NULL
)) {
233 for (ep
= Image
->ExtensionBlocks
;
234 ep
< (Image
->ExtensionBlocks
+ Image
->ExtensionBlockCount
); ep
++)
235 ungif_free(ep
->Bytes
);
236 ungif_free(Image
->ExtensionBlocks
);
237 Image
->ExtensionBlocks
= NULL
;
240 /******************************************************************************
241 * Image block allocation functions
242 ******************************************************************************/
245 FreeSavedImages(GifFileType
* GifFile
) {
249 if ((GifFile
== NULL
) || (GifFile
->SavedImages
== NULL
)) {
252 for (sp
= GifFile
->SavedImages
;
253 sp
< GifFile
->SavedImages
+ GifFile
->ImageCount
; sp
++) {
254 if (sp
->ImageDesc
.ColorMap
) {
255 FreeMapObject(sp
->ImageDesc
.ColorMap
);
256 sp
->ImageDesc
.ColorMap
= NULL
;
259 ungif_free(sp
->RasterBits
);
261 if (sp
->ExtensionBlocks
)
264 ungif_free(GifFile
->SavedImages
);
265 GifFile
->SavedImages
=NULL
;
268 /******************************************************************************
269 * This routine should be called before any other DGif calls. Note that
270 * this routine is called automatically from DGif file open routines.
271 *****************************************************************************/
273 DGifGetScreenDesc(GifFileType
* GifFile
) {
275 int i
, BitsPerPixel
, SortFlag
;
278 /* Put the screen descriptor into the file: */
279 if (DGifGetWord(GifFile
, &GifFile
->SWidth
) == GIF_ERROR
||
280 DGifGetWord(GifFile
, &GifFile
->SHeight
) == GIF_ERROR
)
283 if (READ(GifFile
, Buf
, 3) != 3) {
286 GifFile
->SColorResolution
= (((Buf
[0] & 0x70) + 1) >> 4) + 1;
287 SortFlag
= (Buf
[0] & 0x08) != 0;
288 BitsPerPixel
= (Buf
[0] & 0x07) + 1;
289 GifFile
->SBackGroundColor
= Buf
[1];
290 GifFile
->SAspectRatio
= Buf
[2];
291 if (Buf
[0] & 0x80) { /* Do we have global color map? */
293 GifFile
->SColorMap
= MakeMapObject(1 << BitsPerPixel
, NULL
);
294 if (GifFile
->SColorMap
== NULL
) {
298 /* Get the global color map: */
299 GifFile
->SColorMap
->SortFlag
= SortFlag
;
300 for (i
= 0; i
< GifFile
->SColorMap
->ColorCount
; i
++) {
301 if (READ(GifFile
, Buf
, 3) != 3) {
302 FreeMapObject(GifFile
->SColorMap
);
303 GifFile
->SColorMap
= NULL
;
306 GifFile
->SColorMap
->Colors
[i
].Red
= Buf
[0];
307 GifFile
->SColorMap
->Colors
[i
].Green
= Buf
[1];
308 GifFile
->SColorMap
->Colors
[i
].Blue
= Buf
[2];
311 GifFile
->SColorMap
= NULL
;
317 /******************************************************************************
318 * This routine should be called before any attempt to read an image.
319 *****************************************************************************/
321 DGifGetRecordType(GifFileType
* GifFile
,
322 GifRecordType
* Type
) {
326 if (READ(GifFile
, &Buf
, 1) != 1) {
327 /* Wine-specific behavior: Native accepts broken GIF files that have no
328 * terminator, so we match this by treating EOF as a terminator. */
329 *Type
= TERMINATE_RECORD_TYPE
;
335 *Type
= IMAGE_DESC_RECORD_TYPE
;
338 *Type
= EXTENSION_RECORD_TYPE
;
341 *Type
= TERMINATE_RECORD_TYPE
;
344 *Type
= UNDEFINED_RECORD_TYPE
;
351 /******************************************************************************
352 * This routine should be called before any attempt to read an image.
353 * Note it is assumed the Image desc. header (',') has been read.
354 *****************************************************************************/
356 DGifGetImageDesc(GifFileType
* GifFile
) {
358 int i
, BitsPerPixel
, SortFlag
;
360 GifFilePrivateType
*Private
= GifFile
->Private
;
363 if (DGifGetWord(GifFile
, &GifFile
->Image
.Left
) == GIF_ERROR
||
364 DGifGetWord(GifFile
, &GifFile
->Image
.Top
) == GIF_ERROR
||
365 DGifGetWord(GifFile
, &GifFile
->Image
.Width
) == GIF_ERROR
||
366 DGifGetWord(GifFile
, &GifFile
->Image
.Height
) == GIF_ERROR
)
368 if (READ(GifFile
, Buf
, 1) != 1) {
371 BitsPerPixel
= (Buf
[0] & 0x07) + 1;
372 SortFlag
= (Buf
[0] & 0x20) != 0;
373 GifFile
->Image
.Interlace
= (Buf
[0] & 0x40);
374 if (Buf
[0] & 0x80) { /* Does this image have local color map? */
376 /*** FIXME: Why do we check both of these in order to do this?
377 * Why do we have both Image and SavedImages? */
378 if (GifFile
->Image
.ColorMap
&& GifFile
->SavedImages
== NULL
)
379 FreeMapObject(GifFile
->Image
.ColorMap
);
381 GifFile
->Image
.ColorMap
= MakeMapObject(1 << BitsPerPixel
, NULL
);
382 if (GifFile
->Image
.ColorMap
== NULL
) {
386 /* Get the image local color map: */
387 GifFile
->Image
.ColorMap
->SortFlag
= SortFlag
;
388 for (i
= 0; i
< GifFile
->Image
.ColorMap
->ColorCount
; i
++) {
389 if (READ(GifFile
, Buf
, 3) != 3) {
390 FreeMapObject(GifFile
->Image
.ColorMap
);
391 GifFile
->Image
.ColorMap
= NULL
;
394 GifFile
->Image
.ColorMap
->Colors
[i
].Red
= Buf
[0];
395 GifFile
->Image
.ColorMap
->Colors
[i
].Green
= Buf
[1];
396 GifFile
->Image
.ColorMap
->Colors
[i
].Blue
= Buf
[2];
398 } else if (GifFile
->Image
.ColorMap
) {
399 FreeMapObject(GifFile
->Image
.ColorMap
);
400 GifFile
->Image
.ColorMap
= NULL
;
403 if (GifFile
->SavedImages
) {
404 if ((GifFile
->SavedImages
= ungif_realloc(GifFile
->SavedImages
,
406 (GifFile
->ImageCount
+ 1))) == NULL
) {
410 if ((GifFile
->SavedImages
= ungif_alloc(sizeof(SavedImage
))) == NULL
) {
415 sp
= &GifFile
->SavedImages
[GifFile
->ImageCount
];
416 sp
->ImageDesc
= GifFile
->Image
;
417 if (GifFile
->Image
.ColorMap
!= NULL
) {
418 sp
->ImageDesc
.ColorMap
= MakeMapObject(
419 GifFile
->Image
.ColorMap
->ColorCount
,
420 GifFile
->Image
.ColorMap
->Colors
);
421 if (sp
->ImageDesc
.ColorMap
== NULL
) {
424 sp
->ImageDesc
.ColorMap
->SortFlag
= GifFile
->Image
.ColorMap
->SortFlag
;
426 sp
->RasterBits
= NULL
;
427 sp
->ExtensionBlockCount
= 0;
428 sp
->ExtensionBlocks
= NULL
;
430 GifFile
->ImageCount
++;
432 Private
->PixelCount
= (long)GifFile
->Image
.Width
*
433 (long)GifFile
->Image
.Height
;
435 DGifSetupDecompress(GifFile
); /* Reset decompress algorithm parameters. */
440 /******************************************************************************
441 * Get one full scanned line (Line) of length LineLen from GIF file.
442 *****************************************************************************/
444 DGifGetLine(GifFileType
* GifFile
,
449 GifFilePrivateType
*Private
= GifFile
->Private
;
452 LineLen
= GifFile
->Image
.Width
;
454 if ((Private
->PixelCount
-= LineLen
) > 0xffff0000UL
) {
458 if (DGifDecompressLine(GifFile
, Line
, LineLen
) == GIF_OK
) {
459 if (Private
->PixelCount
== 0) {
460 /* We probably would not be called any more, so lets clean
461 * everything before we return: need to flush out all rest of
462 * image until empty block (size 0) detected. We use GetCodeNext. */
464 if (DGifGetCodeNext(GifFile
, &Dummy
) == GIF_ERROR
)
466 while (Dummy
!= NULL
) ;
473 /******************************************************************************
474 * Get an extension block (see GIF manual) from gif file. This routine only
475 * returns the first data block, and DGifGetExtensionNext should be called
476 * after this one until NULL extension is returned.
477 * The Extension should NOT be freed by the user (not dynamically allocated).
478 * Note it is assumed the Extension desc. header ('!') has been read.
479 *****************************************************************************/
481 DGifGetExtension(GifFileType
* GifFile
,
483 GifByteType
** Extension
) {
487 if (READ(GifFile
, &Buf
, 1) != 1) {
492 return DGifGetExtensionNext(GifFile
, Extension
);
495 /******************************************************************************
496 * Get a following extension block (see GIF manual) from gif file. This
497 * routine should be called until NULL Extension is returned.
498 * The Extension should NOT be freed by the user (not dynamically allocated).
499 *****************************************************************************/
501 DGifGetExtensionNext(GifFileType
* GifFile
,
502 GifByteType
** Extension
) {
505 GifFilePrivateType
*Private
= GifFile
->Private
;
507 if (READ(GifFile
, &Buf
, 1) != 1) {
511 *Extension
= Private
->Buf
; /* Use private unused buffer. */
512 (*Extension
)[0] = Buf
; /* Pascal strings notation (pos. 0 is len.). */
513 if (READ(GifFile
, &((*Extension
)[1]), Buf
) != Buf
) {
522 /******************************************************************************
523 * Get 2 bytes (word) from the given file:
524 *****************************************************************************/
526 DGifGetWord(GifFileType
* GifFile
,
531 if (READ(GifFile
, c
, 2) != 2) {
535 *Word
= (((unsigned int)c
[1]) << 8) + c
[0];
539 /******************************************************************************
540 * Continue to get the image code in compressed form. This routine should be
541 * called until NULL block is returned.
542 * The block should NOT be freed by the user (not dynamically allocated).
543 *****************************************************************************/
545 DGifGetCodeNext(GifFileType
* GifFile
,
546 GifByteType
** CodeBlock
) {
549 GifFilePrivateType
*Private
= GifFile
->Private
;
551 if (READ(GifFile
, &Buf
, 1) != 1) {
556 *CodeBlock
= Private
->Buf
; /* Use private unused buffer. */
557 (*CodeBlock
)[0] = Buf
; /* Pascal strings notation (pos. 0 is len.). */
558 if (READ(GifFile
, &((*CodeBlock
)[1]), Buf
) != Buf
) {
563 Private
->Buf
[0] = 0; /* Make sure the buffer is empty! */
564 Private
->PixelCount
= 0; /* And local info. indicate image read. */
570 /******************************************************************************
571 * Setup the LZ decompression for this image:
572 *****************************************************************************/
574 DGifSetupDecompress(GifFileType
* GifFile
) {
577 GifByteType CodeSize
;
578 GifPrefixType
*Prefix
;
579 GifFilePrivateType
*Private
= GifFile
->Private
;
581 READ(GifFile
, &CodeSize
, 1); /* Read Code size from file. */
582 BitsPerPixel
= CodeSize
;
584 Private
->Buf
[0] = 0; /* Input Buffer empty. */
585 Private
->BitsPerPixel
= BitsPerPixel
;
586 Private
->ClearCode
= (1 << BitsPerPixel
);
587 Private
->EOFCode
= Private
->ClearCode
+ 1;
588 Private
->RunningCode
= Private
->EOFCode
+ 1;
589 Private
->RunningBits
= BitsPerPixel
+ 1; /* Number of bits per code. */
590 Private
->MaxCode1
= 1 << Private
->RunningBits
; /* Max. code + 1. */
591 Private
->StackPtr
= 0; /* No pixels on the pixel stack. */
592 Private
->LastCode
= NO_SUCH_CODE
;
593 Private
->CrntShiftState
= 0; /* No information in CrntShiftDWord. */
594 Private
->CrntShiftDWord
= 0;
596 Prefix
= Private
->Prefix
;
597 for (i
= 0; i
<= LZ_MAX_CODE
; i
++)
598 Prefix
[i
] = NO_SUCH_CODE
;
603 /******************************************************************************
604 * The LZ decompression routine:
605 * This version decompress the given gif file into Line of length LineLen.
606 * This routine can be called few times (one per scan line, for example), in
607 * order the complete the whole image.
608 *****************************************************************************/
610 DGifDecompressLine(GifFileType
* GifFile
,
615 int j
, CrntCode
, EOFCode
, ClearCode
, CrntPrefix
, LastCode
, StackPtr
;
616 GifByteType
*Stack
, *Suffix
;
617 GifPrefixType
*Prefix
;
618 GifFilePrivateType
*Private
= GifFile
->Private
;
620 StackPtr
= Private
->StackPtr
;
621 Prefix
= Private
->Prefix
;
622 Suffix
= Private
->Suffix
;
623 Stack
= Private
->Stack
;
624 EOFCode
= Private
->EOFCode
;
625 ClearCode
= Private
->ClearCode
;
626 LastCode
= Private
->LastCode
;
629 /* Let pop the stack off before continuing to read the gif file: */
630 while (StackPtr
!= 0 && i
< LineLen
)
631 Line
[i
++] = Stack
[--StackPtr
];
634 while (i
< LineLen
) { /* Decode LineLen items. */
635 if (DGifDecompressInput(GifFile
, &CrntCode
) == GIF_ERROR
)
638 if (CrntCode
== EOFCode
) {
639 /* Note, however, that usually we will not be here as we will stop
640 * decoding as soon as we got all the pixel, or EOF code will
641 * not be read at all, and DGifGetLine/Pixel clean everything. */
642 if (i
!= LineLen
- 1 || Private
->PixelCount
!= 0) {
646 } else if (CrntCode
== ClearCode
) {
647 /* We need to start over again: */
648 for (j
= 0; j
<= LZ_MAX_CODE
; j
++)
649 Prefix
[j
] = NO_SUCH_CODE
;
650 Private
->RunningCode
= Private
->EOFCode
+ 1;
651 Private
->RunningBits
= Private
->BitsPerPixel
+ 1;
652 Private
->MaxCode1
= 1 << Private
->RunningBits
;
653 LastCode
= Private
->LastCode
= NO_SUCH_CODE
;
655 /* It's a regular code - if in pixel range simply add it to output
656 * stream, otherwise trace to codes linked list until the prefix
657 * is in pixel range: */
658 if (CrntCode
< ClearCode
) {
659 /* This is simple - its pixel scalar, so add it to output: */
660 Line
[i
++] = CrntCode
;
662 /* It's a code to be traced: trace the linked list
663 * until the prefix is a pixel, while pushing the suffix
664 * pixels on our stack. If we done, pop the stack in reverse
665 * order (that's what stack is good for!) for output. */
666 if (Prefix
[CrntCode
] == NO_SUCH_CODE
) {
667 /* Only allowed if CrntCode is exactly the running code:
668 * In that case CrntCode = XXXCode, CrntCode or the
669 * prefix code is last code and the suffix char is
670 * exactly the prefix of last code! */
671 if (CrntCode
== Private
->RunningCode
- 2) {
672 CrntPrefix
= LastCode
;
673 Suffix
[Private
->RunningCode
- 2] =
674 Stack
[StackPtr
++] = DGifGetPrefixChar(Prefix
,
681 CrntPrefix
= CrntCode
;
683 /* Now (if image is O.K.) we should not get a NO_SUCH_CODE
684 * during the trace. As we might loop forever, in case of
685 * defective image, we count the number of loops we trace
686 * and stop if we got LZ_MAX_CODE. Obviously we cannot
687 * loop more than that. */
689 while (j
++ <= LZ_MAX_CODE
&&
690 CrntPrefix
> ClearCode
&& CrntPrefix
<= LZ_MAX_CODE
) {
691 Stack
[StackPtr
++] = Suffix
[CrntPrefix
];
692 CrntPrefix
= Prefix
[CrntPrefix
];
694 if (j
>= LZ_MAX_CODE
|| CrntPrefix
> LZ_MAX_CODE
) {
697 /* Push the last character on stack: */
698 Stack
[StackPtr
++] = CrntPrefix
;
700 /* Now lets pop all the stack into output: */
701 while (StackPtr
!= 0 && i
< LineLen
)
702 Line
[i
++] = Stack
[--StackPtr
];
704 if (LastCode
!= NO_SUCH_CODE
) {
705 Prefix
[Private
->RunningCode
- 2] = LastCode
;
707 if (CrntCode
== Private
->RunningCode
- 2) {
708 /* Only allowed if CrntCode is exactly the running code:
709 * In that case CrntCode = XXXCode, CrntCode or the
710 * prefix code is last code and the suffix char is
711 * exactly the prefix of last code! */
712 Suffix
[Private
->RunningCode
- 2] =
713 DGifGetPrefixChar(Prefix
, LastCode
, ClearCode
);
715 Suffix
[Private
->RunningCode
- 2] =
716 DGifGetPrefixChar(Prefix
, CrntCode
, ClearCode
);
723 Private
->LastCode
= LastCode
;
724 Private
->StackPtr
= StackPtr
;
729 /******************************************************************************
730 * Routine to trace the Prefixes linked list until we get a prefix which is
731 * not code, but a pixel value (less than ClearCode). Returns that pixel value.
732 * If image is defective, we might loop here forever, so we limit the loops to
733 * the maximum possible if image O.k. - LZ_MAX_CODE times.
734 *****************************************************************************/
736 DGifGetPrefixChar(const GifPrefixType
*Prefix
,
742 while (Code
> ClearCode
&& i
++ <= LZ_MAX_CODE
)
747 /******************************************************************************
748 * The LZ decompression input routine:
749 * This routine is responsible for the decompression of the bit stream from
750 * 8 bits (bytes) packets, into the real codes.
751 * Returns GIF_OK if read successfully.
752 *****************************************************************************/
754 DGifDecompressInput(GifFileType
* GifFile
,
757 GifFilePrivateType
*Private
= GifFile
->Private
;
759 GifByteType NextByte
;
760 static const unsigned short CodeMasks
[] = {
761 0x0000, 0x0001, 0x0003, 0x0007,
762 0x000f, 0x001f, 0x003f, 0x007f,
763 0x00ff, 0x01ff, 0x03ff, 0x07ff,
766 /* The image can't contain more than LZ_BITS per code. */
767 if (Private
->RunningBits
> LZ_BITS
) {
771 while (Private
->CrntShiftState
< Private
->RunningBits
) {
772 /* Needs to get more bytes from input stream for next code: */
773 if (DGifBufferedInput(GifFile
, Private
->Buf
, &NextByte
) == GIF_ERROR
) {
776 Private
->CrntShiftDWord
|=
777 ((unsigned long)NextByte
) << Private
->CrntShiftState
;
778 Private
->CrntShiftState
+= 8;
780 *Code
= Private
->CrntShiftDWord
& CodeMasks
[Private
->RunningBits
];
782 Private
->CrntShiftDWord
>>= Private
->RunningBits
;
783 Private
->CrntShiftState
-= Private
->RunningBits
;
785 /* If code cannot fit into RunningBits bits, must raise its size. Note
786 * however that codes above 4095 are used for special signaling.
787 * If we're using LZ_BITS bits already and we're at the max code, just
788 * keep using the table as it is, don't increment Private->RunningCode.
790 if (Private
->RunningCode
< LZ_MAX_CODE
+ 2 &&
791 ++Private
->RunningCode
> Private
->MaxCode1
&&
792 Private
->RunningBits
< LZ_BITS
) {
793 Private
->MaxCode1
<<= 1;
794 Private
->RunningBits
++;
799 /******************************************************************************
800 * This routines read one gif data block at a time and buffers it internally
801 * so that the decompression routine could access it.
802 * The routine returns the next byte from its internal buffer (or read next
803 * block in if buffer empty) and returns GIF_OK if successful.
804 *****************************************************************************/
806 DGifBufferedInput(GifFileType
* GifFile
,
808 GifByteType
* NextByte
) {
811 /* Needs to read the next buffer - this one is empty: */
812 if (READ(GifFile
, Buf
, 1) != 1) {
815 /* There shouldn't be any empty data blocks here as the LZW spec
816 * says the LZW termination code should come first. Therefore we
817 * shouldn't be inside this routine at that point.
822 if (READ(GifFile
, &Buf
[1], Buf
[0]) != Buf
[0]) {
826 Buf
[1] = 2; /* We use now the second place as last char read! */
829 *NextByte
= Buf
[Buf
[1]++];
836 /******************************************************************************
837 * This routine reads an entire GIF into core, hanging all its state info off
838 * the GifFileType pointer. Call DGifOpenFileName() or DGifOpenFileHandle()
839 * first to initialize I/O. Its inverse is EGifSpew().
840 ******************************************************************************/
842 DGifSlurp(GifFileType
* GifFile
) {
845 GifRecordType RecordType
;
847 GifByteType
*ExtData
;
848 SavedImage temp_save
;
850 temp_save
.ExtensionBlocks
= NULL
;
851 temp_save
.ExtensionBlockCount
= 0;
854 if (DGifGetRecordType(GifFile
, &RecordType
) == GIF_ERROR
)
857 switch (RecordType
) {
858 case IMAGE_DESC_RECORD_TYPE
:
859 if (DGifGetImageDesc(GifFile
) == GIF_ERROR
)
862 sp
= &GifFile
->SavedImages
[GifFile
->ImageCount
- 1];
863 ImageSize
= sp
->ImageDesc
.Width
* sp
->ImageDesc
.Height
;
865 sp
->RasterBits
= ungif_alloc(ImageSize
* sizeof(GifPixelType
));
866 if (sp
->RasterBits
== NULL
) {
869 if (DGifGetLine(GifFile
, sp
->RasterBits
, ImageSize
) ==
872 if (temp_save
.ExtensionBlocks
) {
873 sp
->ExtensionBlocks
= temp_save
.ExtensionBlocks
;
874 sp
->ExtensionBlockCount
= temp_save
.ExtensionBlockCount
;
876 temp_save
.ExtensionBlocks
= NULL
;
877 temp_save
.ExtensionBlockCount
= 0;
879 /* FIXME: The following is wrong. It is left in only for
880 * backwards compatibility. Someday it should go away. Use
881 * the sp->ExtensionBlocks->Function variable instead. */
882 sp
->Function
= sp
->ExtensionBlocks
[0].Function
;
886 case EXTENSION_RECORD_TYPE
:
887 if (DGifGetExtension(GifFile
, &temp_save
.Function
, &ExtData
) ==
890 while (ExtData
!= NULL
) {
892 /* Create an extension block with our data */
893 if (AddExtensionBlock(&temp_save
, ExtData
[0], &ExtData
[1])
897 if (DGifGetExtensionNext(GifFile
, &ExtData
) == GIF_ERROR
)
899 temp_save
.Function
= 0;
903 case TERMINATE_RECORD_TYPE
:
906 default: /* Should be trapped by DGifGetRecordType */
909 } while (RecordType
!= TERMINATE_RECORD_TYPE
);
911 /* Just in case the Gif has an extension block without an associated
912 * image... (Should we save this into a savefile structure with no image
913 * instead? Have to check if the present writing code can handle that as
915 if (temp_save
.ExtensionBlocks
)
916 FreeExtension(&temp_save
);
921 /******************************************************************************
922 * GifFileType constructor with user supplied input function (TVT)
923 *****************************************************************************/
925 DGifOpen(void *userData
,
926 InputFunc readFunc
) {
928 unsigned char Buf
[GIF_STAMP_LEN
+ 1];
929 GifFileType
*GifFile
;
930 GifFilePrivateType
*Private
;
932 GifFile
= ungif_alloc(sizeof(GifFileType
));
933 if (GifFile
== NULL
) {
937 memset(GifFile
, '\0', sizeof(GifFileType
));
939 Private
= ungif_alloc(sizeof(GifFilePrivateType
));
945 GifFile
->Private
= (void*)Private
;
947 Private
->Read
= readFunc
; /* TVT */
948 GifFile
->UserData
= userData
; /* TVT */
950 /* Lets see if this is a GIF file: */
951 if (READ(GifFile
, Buf
, GIF_STAMP_LEN
) != GIF_STAMP_LEN
) {
957 /* The GIF Version number is ignored at this time. Maybe we should do
958 * something more useful with it. */
959 Buf
[GIF_STAMP_LEN
] = 0;
960 if (memcmp(GIF_STAMP
, Buf
, GIF_VERSION_POS
) != 0) {
966 if (DGifGetScreenDesc(GifFile
) == GIF_ERROR
) {
975 /******************************************************************************
976 * This routine should be called last, to close the GIF file.
977 *****************************************************************************/
979 DGifCloseFile(GifFileType
* GifFile
) {
981 GifFilePrivateType
*Private
;
986 Private
= GifFile
->Private
;
988 if (GifFile
->Image
.ColorMap
) {
989 FreeMapObject(GifFile
->Image
.ColorMap
);
990 GifFile
->Image
.ColorMap
= NULL
;
993 if (GifFile
->SColorMap
) {
994 FreeMapObject(GifFile
->SColorMap
);
995 GifFile
->SColorMap
= NULL
;
1001 if (GifFile
->SavedImages
) {
1002 FreeSavedImages(GifFile
);
1003 GifFile
->SavedImages
= NULL
;
1006 ungif_free(GifFile
);