dlls/windowscodecs/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
  53 #include <stdarg.h>
  54 #include "windef.h"
  55 #include "winbase.h"
  56 #include "ungif.h"
  57 #include "wine/debug.h"
  58
  59 WINE_DEFAULT_DEBUG_CHANNEL(wincodecs);
  60
  61 #define LZ_MAX_CODE         4095    /* Biggest code possible in 12 bits. */
  62 #define LZ_BITS             12
  63
  64 #define NO_SUCH_CODE        4098    /* Impossible code, to signal empty. */
  65
  66 typedef struct GifFilePrivateType {
  67     GifWord BitsPerPixel,     /* Bits per pixel (Codes uses at least this + 1). */
  68       ClearCode,   /* The CLEAR LZ code. */
  69       EOFCode,     /* The EOF LZ code. */
  70       RunningCode, /* The next code algorithm can generate. */
  71       RunningBits, /* The number of bits required to represent RunningCode. */
  72       MaxCode1,    /* 1 bigger than max. possible code, in RunningBits bits. */
  73       LastCode,    /* The code before the current code. */
  74       CrntCode,    /* Current algorithm code. */
  75       StackPtr,    /* For character stack (see below). */
  76       CrntShiftState;    /* Number of bits in CrntShiftDWord. */
  77     unsigned long CrntShiftDWord;   /* For bytes decomposition into codes. */
  78     unsigned long PixelCount;   /* Number of pixels in image. */
  79     InputFunc Read;     /* function to read gif input (TVT) */
  80     GifByteType Buf[256];   /* Compressed input is buffered here. */
  81     GifByteType Stack[LZ_MAX_CODE]; /* Decoded pixels are stacked here. */
  82     GifByteType Suffix[LZ_MAX_CODE + 1];    /* So we can trace the codes. */
  83     GifPrefixType Prefix[LZ_MAX_CODE + 1];
  84 } GifFilePrivateType;
  85
  86 /* avoid extra function call in case we use fread (TVT) */
  87 #define READ(_gif,_buf,_len) \
  88     ((GifFilePrivateType*)_gif->Private)->Read(_gif,_buf,_len)
  89
  90 static int DGifGetWord(GifFileType *GifFile, GifWord *Word);
  91 static int DGifSetupDecompress(GifFileType *GifFile);
  92 static int DGifDecompressLine(GifFileType *GifFile, GifPixelType *Line, int LineLen);
  93 static int DGifGetPrefixChar(const GifPrefixType *Prefix, int Code, int ClearCode);
  94 static int DGifDecompressInput(GifFileType *GifFile, int *Code);
  95 static int DGifBufferedInput(GifFileType *GifFile, GifByteType *Buf,
  96                              GifByteType *NextByte);
  97
  98 static int DGifGetExtensionNext(GifFileType * GifFile, GifByteType ** GifExtension);
  99 static int DGifGetCodeNext(GifFileType * GifFile, GifByteType ** GifCodeBlock);
 100
 101 /******************************************************************************
 102  * Miscellaneous utility functions
 103  *****************************************************************************/
 104
 105 /* return smallest bitfield size n will fit in */
 106 static int
 107 BitSize(int n) {
 108
 109     register int i;
 110
 111     for (i = 1; i <= 8; i++)
 112         if ((1 << i) >= n)
 113             break;
 114     return (i);
 115 }
 116
 117 /******************************************************************************
 118  * Color map object functions
 119  *****************************************************************************/
 120
 121 /*
 122  * Allocate a color map of given size; initialize with contents of
 123  * ColorMap if that pointer is non-NULL.
 124  */
 125 static ColorMapObject *
 126 MakeMapObject(int ColorCount,
 127               const GifColorType * ColorMap) {
 128
 129     ColorMapObject *Object;
 130
 131     /*** FIXME: Our ColorCount has to be a power of two.  Is it necessary to
 132      * make the user know that or should we automatically round up instead? */
 133     if (ColorCount != (1 << BitSize(ColorCount))) {
 134         return NULL;
 135     }
 136
 137     Object = malloc(sizeof(ColorMapObject));
 138     if (Object == NULL) {
 139         return NULL;
 140     }
 141
 142     Object->Colors = calloc(ColorCount, sizeof(GifColorType));
 143     if (Object->Colors == NULL) {
 144         free(Object);
 145         return NULL;
 146     }
 147
 148     Object->ColorCount = ColorCount;
 149     Object->BitsPerPixel = BitSize(ColorCount);
 150
 151     if (ColorMap) {
 152         memcpy(Object->Colors, ColorMap, ColorCount * sizeof(GifColorType));
 153     }
 154
 155     return (Object);
 156 }
 157
 158 /*
 159  * Free a color map object
 160  */
 161 static void
 162 FreeMapObject(ColorMapObject * Object) {
 163
 164     if (Object != NULL) {
 165         free(Object->Colors);
 166         free(Object);
 167         /*** FIXME:
 168          * When we are willing to break API we need to make this function
 169          * FreeMapObject(ColorMapObject **Object)
 170          * and do this assignment to NULL here:
 171          * *Object = NULL;
 172          */
 173     }
 174 }
 175
 176 static int
 177 AddExtensionBlock(Extensions *New,
 178                   int Len,
 179                   const unsigned char ExtData[]) {
 180
 181     ExtensionBlock *ep;
 182
 183     New->ExtensionBlocks = realloc(New->ExtensionBlocks,
 184                                    sizeof(ExtensionBlock) *
 185                                    (New->ExtensionBlockCount + 1));
 186
 187     if (New->ExtensionBlocks == NULL)
 188         return (GIF_ERROR);
 189
 190     ep = &New->ExtensionBlocks[New->ExtensionBlockCount++];
 191
 192     ep->ByteCount=Len + 3;
 193     ep->Bytes = malloc(ep->ByteCount + 3);
 194     if (ep->Bytes == NULL)
 195         return (GIF_ERROR);
 196
 197     /* Extension Header */
 198     ep->Bytes[0] = 0x21;
 199     ep->Bytes[1] = New->Function;
 200     ep->Bytes[2] = Len;
 201
 202     if (ExtData) {
 203         memcpy(ep->Bytes + 3, ExtData, Len);
 204         ep->Function = New->Function;
 205     }
 206
 207     return (GIF_OK);
 208 }
 209
 210 static int
 211 AppendExtensionBlock(Extensions *New,
 212                      int Len,
 213                      const unsigned char ExtData[])
 214 {
 215     ExtensionBlock *ep;
 216
 217     if (New->ExtensionBlocks == NULL)
 218         return (GIF_ERROR);
 219
 220     ep = &New->ExtensionBlocks[New->ExtensionBlockCount - 1];
 221
 222     ep->Bytes = realloc(ep->Bytes, ep->ByteCount + Len + 1);
 223     if (ep->Bytes == NULL)
 224         return (GIF_ERROR);
 225
 226     ep->Bytes[ep->ByteCount] = Len;
 227
 228     if (ExtData)
 229         memcpy(ep->Bytes + ep->ByteCount + 1, ExtData, Len);
 230
 231     ep->ByteCount += Len + 1;
 232
 233     return (GIF_OK);
 234 }
 235
 236 static void
 237 FreeExtension(Extensions *Extensions)
 238 {
 239     ExtensionBlock *ep;
 240
 241     if ((Extensions == NULL) || (Extensions->ExtensionBlocks == NULL)) {
 242         return;
 243     }
 244     for (ep = Extensions->ExtensionBlocks;
 245          ep < (Extensions->ExtensionBlocks + Extensions->ExtensionBlockCount); ep++)
 246         free(ep->Bytes);
 247     free(Extensions->ExtensionBlocks);
 248     Extensions->ExtensionBlocks = NULL;
 249 }
 250
 251 /******************************************************************************
 252  * Image block allocation functions
 253 ******************************************************************************/
 254
 255 static void
 256 FreeSavedImages(GifFileType * GifFile) {
 257
 258     SavedImage *sp;
 259
 260     if ((GifFile == NULL) || (GifFile->SavedImages == NULL)) {
 261         return;
 262     }
 263     for (sp = GifFile->SavedImages;
 264          sp < GifFile->SavedImages + GifFile->ImageCount; sp++) {
 265         if (sp->ImageDesc.ColorMap) {
 266             FreeMapObject(sp->ImageDesc.ColorMap);
 267             sp->ImageDesc.ColorMap = NULL;
 268         }
 269
 270         free(sp->RasterBits);
 271
 272         if (sp->Extensions.ExtensionBlocks)
 273             FreeExtension(&sp->Extensions);
 274     }
 275     free(GifFile->SavedImages);
 276     GifFile->SavedImages=NULL;
 277 }
 278
 279 /******************************************************************************
 280  * This routine should be called before any other DGif calls. Note that
 281  * this routine is called automatically from DGif file open routines.
 282  *****************************************************************************/
 283 static int
 284 DGifGetScreenDesc(GifFileType * GifFile) {
 285
 286     int i, BitsPerPixel, SortFlag;
 287     GifByteType Buf[3];
 288
 289     /* Put the screen descriptor into the file: */
 290     if (DGifGetWord(GifFile, &GifFile->SWidth) == GIF_ERROR ||
 291         DGifGetWord(GifFile, &GifFile->SHeight) == GIF_ERROR)
 292         return GIF_ERROR;
 293
 294     if (READ(GifFile, Buf, 3) != 3) {
 295         return GIF_ERROR;
 296     }
 297     GifFile->SColorResolution = (((Buf[0] & 0x70) + 1) >> 4) + 1;
 298     SortFlag = (Buf[0] & 0x08) != 0;
 299     BitsPerPixel = (Buf[0] & 0x07) + 1;
 300     GifFile->SColorTableSize = 1 << BitsPerPixel;
 301     GifFile->SBackGroundColor = Buf[1];
 302     GifFile->SAspectRatio = Buf[2];
 303     if (Buf[0] & 0x80) {    /* Do we have global color map? */
 304
 305         GifFile->SColorMap = MakeMapObject(1 << BitsPerPixel, NULL);
 306         if (GifFile->SColorMap == NULL) {
 307             return GIF_ERROR;
 308         }
 309
 310         /* Get the global color map: */
 311         GifFile->SColorMap->SortFlag = SortFlag;
 312         for (i = 0; i < GifFile->SColorMap->ColorCount; i++) {
 313             if (READ(GifFile, Buf, 3) != 3) {
 314                 FreeMapObject(GifFile->SColorMap);
 315                 GifFile->SColorMap = NULL;
 316                 return GIF_ERROR;
 317             }
 318             GifFile->SColorMap->Colors[i].Red = Buf[0];
 319             GifFile->SColorMap->Colors[i].Green = Buf[1];
 320             GifFile->SColorMap->Colors[i].Blue = Buf[2];
 321         }
 322     } else {
 323         GifFile->SColorMap = NULL;
 324     }
 325
 326     return GIF_OK;
 327 }
 328
 329 /******************************************************************************
 330  * This routine should be called before any attempt to read an image.
 331  *****************************************************************************/
 332 static int
 333 DGifGetRecordType(GifFileType * GifFile,
 334                   GifRecordType * Type) {
 335
 336     GifByteType Buf;
 337
 338     if (READ(GifFile, &Buf, 1) != 1) {
 339         /* Wine-specific behavior: Native accepts broken GIF files that have no
 340          * terminator, so we match this by treating EOF as a terminator. */
 341         *Type = TERMINATE_RECORD_TYPE;
 342         return GIF_OK;
 343     }
 344
 345     switch (Buf) {
 346       case ',':
 347           *Type = IMAGE_DESC_RECORD_TYPE;
 348           break;
 349       case '!':
 350           *Type = EXTENSION_RECORD_TYPE;
 351           break;
 352       case ';':
 353           *Type = TERMINATE_RECORD_TYPE;
 354           break;
 355       default:
 356           *Type = UNDEFINED_RECORD_TYPE;
 357           return GIF_ERROR;
 358     }
 359
 360     return GIF_OK;
 361 }
 362
 363 /******************************************************************************
 364  * This routine should be called before any attempt to read an image.
 365  * Note it is assumed the Image desc. header (',') has been read.
 366  *****************************************************************************/
 367 static int
 368 DGifGetImageDesc(GifFileType * GifFile) {
 369
 370     int i, BitsPerPixel, SortFlag;
 371     GifByteType Buf[3];
 372     GifFilePrivateType *Private = GifFile->Private;
 373     SavedImage *sp;
 374
 375     if (DGifGetWord(GifFile, &GifFile->Image.Left) == GIF_ERROR ||
 376         DGifGetWord(GifFile, &GifFile->Image.Top) == GIF_ERROR ||
 377         DGifGetWord(GifFile, &GifFile->Image.Width) == GIF_ERROR ||
 378         DGifGetWord(GifFile, &GifFile->Image.Height) == GIF_ERROR)
 379         return GIF_ERROR;
 380     if (READ(GifFile, Buf, 1) != 1) {
 381         return GIF_ERROR;
 382     }
 383     BitsPerPixel = (Buf[0] & 0x07) + 1;
 384     SortFlag = (Buf[0] & 0x20) != 0;
 385     GifFile->Image.Interlace = (Buf[0] & 0x40);
 386     if (Buf[0] & 0x80) {    /* Does this image have local color map? */
 387
 388         FreeMapObject(GifFile->Image.ColorMap);
 389
 390         GifFile->Image.ColorMap = MakeMapObject(1 << BitsPerPixel, NULL);
 391         if (GifFile->Image.ColorMap == NULL) {
 392             return GIF_ERROR;
 393         }
 394
 395         /* Get the image local color map: */
 396         GifFile->Image.ColorMap->SortFlag = SortFlag;
 397         for (i = 0; i < GifFile->Image.ColorMap->ColorCount; i++) {
 398             if (READ(GifFile, Buf, 3) != 3) {
 399                 FreeMapObject(GifFile->Image.ColorMap);
 400                 GifFile->Image.ColorMap = NULL;
 401                 return GIF_ERROR;
 402             }
 403             GifFile->Image.ColorMap->Colors[i].Red = Buf[0];
 404             GifFile->Image.ColorMap->Colors[i].Green = Buf[1];
 405             GifFile->Image.ColorMap->Colors[i].Blue = Buf[2];
 406         }
 407     } else if (GifFile->Image.ColorMap) {
 408         FreeMapObject(GifFile->Image.ColorMap);
 409         GifFile->Image.ColorMap = NULL;
 410     }
 411
 412     if ((GifFile->SavedImages = realloc(GifFile->SavedImages,
 413                                         sizeof(SavedImage) *
 414                                         (GifFile->ImageCount + 1))) == NULL) {
 415         return GIF_ERROR;
 416     }
 417
 418     sp = &GifFile->SavedImages[GifFile->ImageCount];
 419     sp->ImageDesc = GifFile->Image;
 420     if (GifFile->Image.ColorMap != NULL) {
 421         sp->ImageDesc.ColorMap = MakeMapObject(
 422                                  GifFile->Image.ColorMap->ColorCount,
 423                                  GifFile->Image.ColorMap->Colors);
 424         if (sp->ImageDesc.ColorMap == NULL) {
 425             return GIF_ERROR;
 426         }
 427         sp->ImageDesc.ColorMap->SortFlag = GifFile->Image.ColorMap->SortFlag;
 428     }
 429     sp->RasterBits = NULL;
 430     sp->Extensions.ExtensionBlockCount = 0;
 431     sp->Extensions.ExtensionBlocks = NULL;
 432
 433     GifFile->ImageCount++;
 434
 435     Private->PixelCount = GifFile->Image.Width * GifFile->Image.Height;
 436
 437     DGifSetupDecompress(GifFile);  /* Reset decompress algorithm parameters. */
 438
 439     return GIF_OK;
 440 }
 441
 442 /******************************************************************************
 443  * Get one full scanned line (Line) of length LineLen from GIF file.
 444  *****************************************************************************/
 445 static int
 446 DGifGetLine(GifFileType * GifFile,
 447             GifPixelType * Line,
 448             int LineLen) {
 449
 450     GifByteType *Dummy;
 451     GifFilePrivateType *Private = GifFile->Private;
 452
 453     if (!LineLen)
 454         LineLen = GifFile->Image.Width;
 455
 456     if ((Private->PixelCount -= LineLen) > 0xffff0000UL) {
 457         return GIF_ERROR;
 458     }
 459
 460     if (DGifDecompressLine(GifFile, Line, LineLen) == GIF_OK) {
 461         if (Private->PixelCount == 0) {
 462             /* We probably would not be called any more, so lets clean
 463              * everything before we return: need to flush out all rest of
 464              * image until empty block (size 0) detected. We use GetCodeNext. */
 465             do
 466                 if (DGifGetCodeNext(GifFile, &Dummy) == GIF_ERROR)
 467                 {
 468                     WARN("GIF is not properly terminated\n");
 469                     break;
 470                 }
 471             while (Dummy != NULL) ;
 472         }
 473         return GIF_OK;
 474     } else
 475         return GIF_ERROR;
 476 }
 477
 478 /******************************************************************************
 479  * Get an extension block (see GIF manual) from gif file. This routine only
 480  * returns the first data block, and DGifGetExtensionNext should be called
 481  * after this one until NULL extension is returned.
 482  * The Extension should NOT be freed by the user (not dynamically allocated).
 483  * Note it is assumed the Extension desc. header ('!') has been read.
 484  *****************************************************************************/
 485 static int
 486 DGifGetExtension(GifFileType * GifFile,
 487                  int *ExtCode,
 488                  GifByteType ** Extension) {
 489
 490     GifByteType Buf;
 491
 492     if (READ(GifFile, &Buf, 1) != 1) {
 493         return GIF_ERROR;
 494     }
 495     *ExtCode = Buf;
 496
 497     return DGifGetExtensionNext(GifFile, Extension);
 498 }
 499
 500 /******************************************************************************
 501  * Get a following extension block (see GIF manual) from gif file. This
 502  * routine should be called until NULL Extension is returned.
 503  * The Extension should NOT be freed by the user (not dynamically allocated).
 504  *****************************************************************************/
 505 static int
 506 DGifGetExtensionNext(GifFileType * GifFile,
 507                      GifByteType ** Extension) {
 508
 509     GifByteType Buf;
 510     GifFilePrivateType *Private = GifFile->Private;
 511
 512     if (READ(GifFile, &Buf, 1) != 1) {
 513         return GIF_ERROR;
 514     }
 515     if (Buf > 0) {
 516         *Extension = Private->Buf;    /* Use private unused buffer. */
 517         (*Extension)[0] = Buf;  /* Pascal strings notation (pos. 0 is len.). */
 518         if (READ(GifFile, &((*Extension)[1]), Buf) != Buf) {
 519             return GIF_ERROR;
 520         }
 521     } else
 522         *Extension = NULL;
 523
 524     return GIF_OK;
 525 }
 526
 527 /******************************************************************************
 528  * Get 2 bytes (word) from the given file:
 529  *****************************************************************************/
 530 static int
 531 DGifGetWord(GifFileType * GifFile,
 532             GifWord *Word) {
 533
 534     unsigned char c[2];
 535
 536     if (READ(GifFile, c, 2) != 2) {
 537         return GIF_ERROR;
 538     }
 539
 540     *Word = (((unsigned int)c[1]) << 8) + c[0];
 541     return GIF_OK;
 542 }
 543
 544 /******************************************************************************
 545  * Continue to get the image code in compressed form. This routine should be
 546  * called until NULL block is returned.
 547  * The block should NOT be freed by the user (not dynamically allocated).
 548  *****************************************************************************/
 549 static int
 550 DGifGetCodeNext(GifFileType * GifFile,
 551                 GifByteType ** CodeBlock) {
 552
 553     GifByteType Buf;
 554     GifFilePrivateType *Private = GifFile->Private;
 555
 556     if (READ(GifFile, &Buf, 1) != 1) {
 557         return GIF_ERROR;
 558     }
 559
 560     if (Buf > 0) {
 561         *CodeBlock = Private->Buf;    /* Use private unused buffer. */
 562         (*CodeBlock)[0] = Buf;  /* Pascal strings notation (pos. 0 is len.). */
 563         if (READ(GifFile, &((*CodeBlock)[1]), Buf) != Buf) {
 564             return GIF_ERROR;
 565         }
 566     } else {
 567         *CodeBlock = NULL;
 568         Private->Buf[0] = 0;    /* Make sure the buffer is empty! */
 569         Private->PixelCount = 0;    /* And local info. indicate image read. */
 570     }
 571
 572     return GIF_OK;
 573 }
 574
 575 /******************************************************************************
 576  * Setup the LZ decompression for this image:
 577  *****************************************************************************/
 578 static int
 579 DGifSetupDecompress(GifFileType * GifFile) {
 580
 581     int i, BitsPerPixel;
 582     GifByteType CodeSize;
 583     GifPrefixType *Prefix;
 584     GifFilePrivateType *Private = GifFile->Private;
 585
 586     READ(GifFile, &CodeSize, 1);    /* Read Code size from file. */
 587     BitsPerPixel = CodeSize;
 588
 589     Private->Buf[0] = 0;    /* Input Buffer empty. */
 590     Private->BitsPerPixel = BitsPerPixel;
 591     Private->ClearCode = (1 << BitsPerPixel);
 592     Private->EOFCode = Private->ClearCode + 1;
 593     Private->RunningCode = Private->EOFCode + 1;
 594     Private->RunningBits = BitsPerPixel + 1;    /* Number of bits per code. */
 595     Private->MaxCode1 = 1 << Private->RunningBits;    /* Max. code + 1. */
 596     Private->StackPtr = 0;    /* No pixels on the pixel stack. */
 597     Private->LastCode = NO_SUCH_CODE;
 598     Private->CrntShiftState = 0;    /* No information in CrntShiftDWord. */
 599     Private->CrntShiftDWord = 0;
 600
 601     Prefix = Private->Prefix;
 602     for (i = 0; i <= LZ_MAX_CODE; i++)
 603         Prefix[i] = NO_SUCH_CODE;
 604
 605     return GIF_OK;
 606 }
 607
 608 /******************************************************************************
 609  * The LZ decompression routine:
 610  * This version decompress the given gif file into Line of length LineLen.
 611  * This routine can be called few times (one per scan line, for example), in
 612  * order the complete the whole image.
 613  *****************************************************************************/
 614 static int
 615 DGifDecompressLine(GifFileType * GifFile,
 616                    GifPixelType * Line,
 617                    int LineLen) {
 618
 619     int i = 0;
 620     int j, CrntCode, EOFCode, ClearCode, CrntPrefix, LastCode, StackPtr;
 621     GifByteType *Stack, *Suffix;
 622     GifPrefixType *Prefix;
 623     GifFilePrivateType *Private = GifFile->Private;
 624
 625     StackPtr = Private->StackPtr;
 626     Prefix = Private->Prefix;
 627     Suffix = Private->Suffix;
 628     Stack = Private->Stack;
 629     EOFCode = Private->EOFCode;
 630     ClearCode = Private->ClearCode;
 631     LastCode = Private->LastCode;
 632
 633     if (StackPtr != 0) {
 634         /* Let pop the stack off before continuing to read the gif file: */
 635         while (StackPtr != 0 && i < LineLen)
 636             Line[i++] = Stack[--StackPtr];
 637     }
 638
 639     while (i < LineLen) {    /* Decode LineLen items. */
 640         if (DGifDecompressInput(GifFile, &CrntCode) == GIF_ERROR)
 641             return GIF_ERROR;
 642
 643         if (CrntCode == EOFCode) {
 644             /* Note, however, that usually we will not be here as we will stop
 645              * decoding as soon as we got all the pixel, or EOF code will
 646              * not be read at all, and DGifGetLine/Pixel clean everything.  */
 647             if (i != LineLen - 1 || Private->PixelCount != 0) {
 648                 return GIF_ERROR;
 649             }
 650             i++;
 651         } else if (CrntCode == ClearCode) {
 652             /* We need to start over again: */
 653             for (j = 0; j <= LZ_MAX_CODE; j++)
 654                 Prefix[j] = NO_SUCH_CODE;
 655             Private->RunningCode = Private->EOFCode + 1;
 656             Private->RunningBits = Private->BitsPerPixel + 1;
 657             Private->MaxCode1 = 1 << Private->RunningBits;
 658             LastCode = Private->LastCode = NO_SUCH_CODE;
 659         } else {
 660             /* It's a regular code - if in pixel range simply add it to output
 661              * stream, otherwise trace to codes linked list until the prefix
 662              * is in pixel range: */
 663             if (CrntCode < ClearCode) {
 664                 /* This is simple - its pixel scalar, so add it to output: */
 665                 Line[i++] = CrntCode;
 666             } else {
 667                 /* It's a code to be traced: trace the linked list
 668                  * until the prefix is a pixel, while pushing the suffix
 669                  * pixels on our stack. If we done, pop the stack in reverse
 670                  * order (that's what stack is good for!) for output.  */
 671                 if (Prefix[CrntCode] == NO_SUCH_CODE) {
 672                     /* Only allowed if CrntCode is exactly the running code:
 673                      * In that case CrntCode = XXXCode, CrntCode or the
 674                      * prefix code is last code and the suffix char is
 675                      * exactly the prefix of last code! */
 676                     if (CrntCode == Private->RunningCode - 2) {
 677                         CrntPrefix = LastCode;
 678                         Suffix[Private->RunningCode - 2] =
 679                            Stack[StackPtr++] = DGifGetPrefixChar(Prefix,
 680                                                                  LastCode,
 681                                                                  ClearCode);
 682                     } else {
 683                         return GIF_ERROR;
 684                     }
 685                 } else
 686                     CrntPrefix = CrntCode;
 687
 688                 /* Now (if image is O.K.) we should not get a NO_SUCH_CODE
 689                  * during the trace. As we might loop forever, in case of
 690                  * defective image, we count the number of loops we trace
 691                  * and stop if we got LZ_MAX_CODE. Obviously we cannot
 692                  * loop more than that.  */
 693                 j = 0;
 694                 while (j++ <= LZ_MAX_CODE &&
 695                        CrntPrefix > ClearCode && CrntPrefix <= LZ_MAX_CODE) {
 696                     Stack[StackPtr++] = Suffix[CrntPrefix];
 697                     CrntPrefix = Prefix[CrntPrefix];
 698                 }
 699                 if (j >= LZ_MAX_CODE || CrntPrefix > LZ_MAX_CODE) {
 700                     return GIF_ERROR;
 701                 }
 702                 /* Push the last character on stack: */
 703                 Stack[StackPtr++] = CrntPrefix;
 704
 705                 /* Now lets pop all the stack into output: */
 706                 while (StackPtr != 0 && i < LineLen)
 707                     Line[i++] = Stack[--StackPtr];
 708             }
 709             if (LastCode != NO_SUCH_CODE) {
 710                 Prefix[Private->RunningCode - 2] = LastCode;
 711
 712                 if (CrntCode == Private->RunningCode - 2) {
 713                     /* Only allowed if CrntCode is exactly the running code:
 714                      * In that case CrntCode = XXXCode, CrntCode or the
 715                      * prefix code is last code and the suffix char is
 716                      * exactly the prefix of last code! */
 717                     Suffix[Private->RunningCode - 2] =
 718                        DGifGetPrefixChar(Prefix, LastCode, ClearCode);
 719                 } else {
 720                     Suffix[Private->RunningCode - 2] =
 721                        DGifGetPrefixChar(Prefix, CrntCode, ClearCode);
 722                 }
 723             }
 724             LastCode = CrntCode;
 725         }
 726     }
 727
 728     Private->LastCode = LastCode;
 729     Private->StackPtr = StackPtr;
 730
 731     return GIF_OK;
 732 }
 733
 734 /******************************************************************************
 735  * Routine to trace the Prefixes linked list until we get a prefix which is
 736  * not code, but a pixel value (less than ClearCode). Returns that pixel value.
 737  * If image is defective, we might loop here forever, so we limit the loops to
 738  * the maximum possible if image O.k. - LZ_MAX_CODE times.
 739  *****************************************************************************/
 740 static int
 741 DGifGetPrefixChar(const GifPrefixType *Prefix,
 742                   int Code,
 743                   int ClearCode) {
 744
 745     int i = 0;
 746
 747     while (Code > ClearCode && i++ <= LZ_MAX_CODE)
 748         Code = Prefix[Code];
 749     return Code;
 750 }
 751
 752 /******************************************************************************
 753  * The LZ decompression input routine:
 754  * This routine is responsible for the decompression of the bit stream from
 755  * 8 bits (bytes) packets, into the real codes.
 756  * Returns GIF_OK if read successfully.
 757  *****************************************************************************/
 758 static int
 759 DGifDecompressInput(GifFileType * GifFile,
 760                     int *Code) {
 761
 762     GifFilePrivateType *Private = GifFile->Private;
 763
 764     GifByteType NextByte;
 765     static const unsigned short CodeMasks[] = {
 766         0x0000, 0x0001, 0x0003, 0x0007,
 767         0x000f, 0x001f, 0x003f, 0x007f,
 768         0x00ff, 0x01ff, 0x03ff, 0x07ff,
 769         0x0fff
 770     };
 771     /* The image can't contain more than LZ_BITS per code. */
 772     if (Private->RunningBits > LZ_BITS) {
 773         return GIF_ERROR;
 774     }
 775
 776     while (Private->CrntShiftState < Private->RunningBits) {
 777         /* Needs to get more bytes from input stream for next code: */
 778         if (DGifBufferedInput(GifFile, Private->Buf, &NextByte) == GIF_ERROR) {
 779             return GIF_ERROR;
 780         }
 781         Private->CrntShiftDWord |=
 782            ((unsigned long)NextByte) << Private->CrntShiftState;
 783         Private->CrntShiftState += 8;
 784     }
 785     *Code = Private->CrntShiftDWord & CodeMasks[Private->RunningBits];
 786
 787     Private->CrntShiftDWord >>= Private->RunningBits;
 788     Private->CrntShiftState -= Private->RunningBits;
 789
 790     /* If code cannot fit into RunningBits bits, must raise its size. Note
 791      * however that codes above 4095 are used for special signaling.
 792      * If we're using LZ_BITS bits already and we're at the max code, just
 793      * keep using the table as it is, don't increment Private->RunningCode.
 794      */
 795     if (Private->RunningCode < LZ_MAX_CODE + 2 &&
 796             ++Private->RunningCode > Private->MaxCode1 &&
 797             Private->RunningBits < LZ_BITS) {
 798         Private->MaxCode1 <<= 1;
 799         Private->RunningBits++;
 800     }
 801     return GIF_OK;
 802 }
 803
 804 /******************************************************************************
 805  * This routines read one gif data block at a time and buffers it internally
 806  * so that the decompression routine could access it.
 807  * The routine returns the next byte from its internal buffer (or read next
 808  * block in if buffer empty) and returns GIF_OK if successful.
 809  *****************************************************************************/
 810 static int
 811 DGifBufferedInput(GifFileType * GifFile,
 812                   GifByteType * Buf,
 813                   GifByteType * NextByte) {
 814
 815     if (Buf[0] == 0) {
 816         /* Needs to read the next buffer - this one is empty: */
 817         if (READ(GifFile, Buf, 1) != 1) {
 818             return GIF_ERROR;
 819         }
 820         /* There shouldn't be any empty data blocks here as the LZW spec
 821          * says the LZW termination code should come first.  Therefore we
 822          * shouldn't be inside this routine at that point.
 823          */
 824         if (Buf[0] == 0) {
 825             return GIF_ERROR;
 826         }
 827         if (READ(GifFile, &Buf[1], Buf[0]) != Buf[0]) {
 828             return GIF_ERROR;
 829         }
 830         *NextByte = Buf[1];
 831         Buf[1] = 2;    /* We use now the second place as last char read! */
 832         Buf[0]--;
 833     } else {
 834         *NextByte = Buf[Buf[1]++];
 835         Buf[0]--;
 836     }
 837
 838     return GIF_OK;
 839 }
 840
 841 /******************************************************************************
 842  * This routine reads an entire GIF into core, hanging all its state info off
 843  * the GifFileType pointer.  Call DGifOpenFileName() or DGifOpenFileHandle()
 844  * first to initialize I/O.  Its inverse is EGifSpew().
 845  ******************************************************************************/
 846 int
 847 DGifSlurp(GifFileType * GifFile) {
 848
 849     int ImageSize;
 850     GifRecordType RecordType;
 851     SavedImage *sp;
 852     GifByteType *ExtData;
 853     Extensions temp_save;
 854
 855     temp_save.ExtensionBlocks = NULL;
 856     temp_save.ExtensionBlockCount = 0;
 857
 858     do {
 859         if (DGifGetRecordType(GifFile, &RecordType) == GIF_ERROR)
 860             return (GIF_ERROR);
 861
 862         switch (RecordType) {
 863           case IMAGE_DESC_RECORD_TYPE:
 864               if (DGifGetImageDesc(GifFile) == GIF_ERROR)
 865                   return (GIF_ERROR);
 866
 867               sp = &GifFile->SavedImages[GifFile->ImageCount - 1];
 868               ImageSize = sp->ImageDesc.Width * sp->ImageDesc.Height;
 869
 870               sp->RasterBits = malloc(ImageSize * sizeof(GifPixelType));
 871               if (sp->RasterBits == NULL) {
 872                   return GIF_ERROR;
 873               }
 874               if (DGifGetLine(GifFile, sp->RasterBits, ImageSize) ==
 875                   GIF_ERROR)
 876                   return (GIF_ERROR);
 877               if (temp_save.ExtensionBlocks) {
 878                   sp->Extensions.ExtensionBlocks = temp_save.ExtensionBlocks;
 879                   sp->Extensions.ExtensionBlockCount = temp_save.ExtensionBlockCount;
 880
 881                   temp_save.ExtensionBlocks = NULL;
 882                   temp_save.ExtensionBlockCount = 0;
 883
 884                   /* FIXME: The following is wrong.  It is left in only for
 885                    * backwards compatibility.  Someday it should go away. Use
 886                    * the sp->ExtensionBlocks->Function variable instead. */
 887                   sp->Extensions.Function = sp->Extensions.ExtensionBlocks[0].Function;
 888               }
 889               break;
 890
 891           case EXTENSION_RECORD_TYPE:
 892           {
 893               int Function;
 894               Extensions *Extensions;
 895
 896               if (DGifGetExtension(GifFile, &Function, &ExtData) == GIF_ERROR)
 897                   return (GIF_ERROR);
 898
 899               if (GifFile->ImageCount || Function == GRAPHICS_EXT_FUNC_CODE)
 900                   Extensions = &temp_save;
 901               else
 902                   Extensions = &GifFile->Extensions;
 903
 904               Extensions->Function = Function;
 905
 906               if (ExtData)
 907               {
 908                   /* Create an extension block with our data */
 909                   if (AddExtensionBlock(Extensions, ExtData[0], &ExtData[1]) == GIF_ERROR)
 910                       return (GIF_ERROR);
 911               }
 912               else /* Empty extension block */
 913               {
 914                   if (AddExtensionBlock(Extensions, 0, NULL) == GIF_ERROR)
 915                       return (GIF_ERROR);
 916               }
 917
 918               while (ExtData != NULL) {
 919                   int Len;
 920                   GifByteType *Data;
 921
 922                   if (DGifGetExtensionNext(GifFile, &ExtData) == GIF_ERROR)
 923                       return (GIF_ERROR);
 924
 925                   if (ExtData)
 926                   {
 927                       Len = ExtData[0];
 928                       Data = &ExtData[1];
 929                   }
 930                   else
 931                   {
 932                       Len = 0;
 933                       Data = NULL;
 934                   }
 935
 936                   if (AppendExtensionBlock(Extensions, Len, Data) == GIF_ERROR)
 937                       return (GIF_ERROR);
 938               }
 939               break;
 940           }
 941
 942           case TERMINATE_RECORD_TYPE:
 943               break;
 944
 945           default:    /* Should be trapped by DGifGetRecordType */
 946               break;
 947         }
 948     } while (RecordType != TERMINATE_RECORD_TYPE);
 949
 950     /* Just in case the Gif has an extension block without an associated
 951      * image... (Should we save this into a savefile structure with no image
 952      * instead? Have to check if the present writing code can handle that as
 953      * well.... */
 954     if (temp_save.ExtensionBlocks)
 955         FreeExtension(&temp_save);
 956
 957     return (GIF_OK);
 958 }
 959
 960 /******************************************************************************
 961  * GifFileType constructor with user supplied input function (TVT)
 962  *****************************************************************************/
 963 GifFileType *
 964 DGifOpen(void *userData,
 965          InputFunc readFunc) {
 966
 967     unsigned char Buf[GIF_STAMP_LEN + 1];
 968     GifFileType *GifFile;
 969     GifFilePrivateType *Private;
 970
 971     GifFile = malloc(sizeof(GifFileType));
 972     if (GifFile == NULL) {
 973         return NULL;
 974     }
 975
 976     memset(GifFile, '\0', sizeof(GifFileType));
 977
 978     Private = malloc(sizeof(GifFilePrivateType));
 979     if (!Private) {
 980         free(GifFile);
 981         return NULL;
 982     }
 983
 984     GifFile->Private = (void*)Private;
 985
 986     Private->Read = readFunc;    /* TVT */
 987     GifFile->UserData = userData;    /* TVT */
 988
 989     /* Lets see if this is a GIF file: */
 990     if (READ(GifFile, Buf, GIF_STAMP_LEN) != GIF_STAMP_LEN) {
 991         free(Private);
 992         free(GifFile);
 993         return NULL;
 994     }
 995
 996     /* The GIF Version number is ignored at this time. Maybe we should do
 997      * something more useful with it. */
 998     Buf[GIF_STAMP_LEN] = 0;
 999     if (memcmp(GIF_STAMP, Buf, GIF_VERSION_POS) != 0) {
1000         free(Private);
1001         free(GifFile);
1002         return NULL;
1003     }
1004
1005     if (DGifGetScreenDesc(GifFile) == GIF_ERROR) {
1006         free(Private);
1007         free(GifFile);
1008         return NULL;
1009     }
1010
1011     return GifFile;
1012 }
1013
1014 /******************************************************************************
1015  * This routine should be called last, to close the GIF file.
1016  *****************************************************************************/
1017 int
1018 DGifCloseFile(GifFileType * GifFile) {
1019
1020     GifFilePrivateType *Private;
1021
1022     if (GifFile == NULL)
1023         return GIF_ERROR;
1024
1025     Private = GifFile->Private;
1026
1027     if (GifFile->Image.ColorMap) {
1028         FreeMapObject(GifFile->Image.ColorMap);
1029         GifFile->Image.ColorMap = NULL;
1030     }
1031
1032     if (GifFile->SColorMap) {
1033         FreeMapObject(GifFile->SColorMap);
1034         GifFile->SColorMap = NULL;
1035     }
1036
1037     free(Private);
1038     Private = NULL;
1039
1040     if (GifFile->SavedImages) {
1041         FreeSavedImages(GifFile);
1042         GifFile->SavedImages = NULL;
1043     }
1044
1045     FreeExtension(&GifFile->Extensions);
1046
1047     free(GifFile);
1048
1049     return GIF_OK;
1050 }