dlls/oleaut32/ungif.c

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