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
  57 #include "ungif.h"
  58
  59 static void *ungif_alloc( size_t sz )
  60 {
  61     return HeapAlloc( GetProcessHeap(), 0, sz );
  62 }
  63
  64 static void *ungif_calloc( size_t num, size_t sz )
  65 {
  66     return HeapAlloc( GetProcessHeap(), HEAP_ZERO_MEMORY, num*sz );
  67 }
  68
  69 static void *ungif_realloc( void *ptr, size_t sz )
  70 {
  71     return HeapReAlloc( GetProcessHeap(), 0, ptr, sz );
  72 }
  73
  74 static void ungif_free( void *ptr )
  75 {
  76     HeapFree( GetProcessHeap(), 0, ptr );
  77 }
  78
  79 #define LZ_MAX_CODE         4095    /* Biggest code possible in 12 bits. */
  80 #define LZ_BITS             12
  81
  82 #define NO_SUCH_CODE        4098    /* Impossible code, to signal empty. */
  83
  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;
 103
 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)
 107
 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);
 115
 116 static int DGifGetExtensionNext(GifFileType * GifFile, GifByteType ** GifExtension);
 117 static int DGifGetCodeNext(GifFileType * GifFile, GifByteType ** GifCodeBlock);
 118
 119 /******************************************************************************
 120  * Miscellaneous utility functions
 121  *****************************************************************************/
 122
 123 /* return smallest bitfield size n will fit in */
 124 static int
 125 BitSize(int n) {
 126
 127     register int i;
 128
 129     for (i = 1; i <= 8; i++)
 130         if ((1 << i) >= n)
 131             break;
 132     return (i);
 133 }
 134
 135 /******************************************************************************
 136  * Color map object functions
 137  *****************************************************************************/
 138
 139 /*
 140  * Allocate a color map of given size; initialize with contents of
 141  * ColorMap if that pointer is non-NULL.
 142  */
 143 static ColorMapObject *
 144 MakeMapObject(int ColorCount,
 145               const GifColorType * ColorMap) {
 146
 147     ColorMapObject *Object;
 148
 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))) {
 152         return NULL;
 153     }
 154
 155     Object = ungif_alloc(sizeof(ColorMapObject));
 156     if (Object == NULL) {
 157         return NULL;
 158     }
 159
 160     Object->Colors = ungif_calloc(ColorCount, sizeof(GifColorType));
 161     if (Object->Colors == NULL) {
 162         ungif_free(Object);
 163         return NULL;
 164     }
 165
 166     Object->ColorCount = ColorCount;
 167     Object->BitsPerPixel = BitSize(ColorCount);
 168
 169     if (ColorMap) {
 170         memcpy(Object->Colors, ColorMap, ColorCount * sizeof(GifColorType));
 171     }
 172
 173     return (Object);
 174 }
 175
 176 /*
 177  * Free a color map object
 178  */
 179 static void
 180 FreeMapObject(ColorMapObject * Object) {
 181
 182     if (Object != NULL) {
 183         ungif_free(Object->Colors);
 184         ungif_free(Object);
 185         /*** FIXME:
 186          * When we are willing to break API we need to make this function
 187          * FreeMapObject(ColorMapObject **Object)
 188          * and do this assignment to NULL here:
 189          * *Object = NULL;
 190          */
 191     }
 192 }
 193
 194 static int
 195 AddExtensionBlock(Extensions *New,
 196                   int Len,
 197                   const unsigned char ExtData[]) {
 198
 199     ExtensionBlock *ep;
 200
 201     if (New->ExtensionBlocks == NULL)
 202         New->ExtensionBlocks = ungif_alloc(sizeof(ExtensionBlock));
 203     else
 204         New->ExtensionBlocks = ungif_realloc(New->ExtensionBlocks,
 205                                       sizeof(ExtensionBlock) *
 206                                       (New->ExtensionBlockCount + 1));
 207
 208     if (New->ExtensionBlocks == NULL)
 209         return (GIF_ERROR);
 210
 211     ep = &New->ExtensionBlocks[New->ExtensionBlockCount++];
 212
 213     ep->ByteCount=Len + 3;
 214     ep->Bytes = ungif_alloc(ep->ByteCount + 3);
 215     if (ep->Bytes == NULL)
 216         return (GIF_ERROR);
 217
 218     /* Extension Header */
 219     ep->Bytes[0] = 0x21;
 220     ep->Bytes[1] = New->Function;
 221     ep->Bytes[2] = Len;
 222
 223     if (ExtData) {
 224         memcpy(ep->Bytes + 3, ExtData, Len);
 225         ep->Function = New->Function;
 226     }
 227
 228     return (GIF_OK);
 229 }
 230
 231 static int
 232 AppendExtensionBlock(Extensions *New,
 233                      int Len,
 234                      const unsigned char ExtData[])
 235 {
 236     ExtensionBlock *ep;
 237
 238     if (New->ExtensionBlocks == NULL)
 239         return (GIF_ERROR);
 240
 241     ep = &New->ExtensionBlocks[New->ExtensionBlockCount - 1];
 242
 243     ep->Bytes = ungif_realloc(ep->Bytes, ep->ByteCount + Len + 1);
 244     if (ep->Bytes == NULL)
 245         return (GIF_ERROR);
 246
 247     ep->Bytes[ep->ByteCount] = Len;
 248
 249     if (ExtData)
 250         memcpy(ep->Bytes + ep->ByteCount + 1, ExtData, Len);
 251
 252     ep->ByteCount += Len + 1;
 253
 254     return (GIF_OK);
 255 }
 256
 257 static void
 258 FreeExtension(Extensions *Extensions)
 259 {
 260     ExtensionBlock *ep;
 261
 262     if ((Extensions == NULL) || (Extensions->ExtensionBlocks == NULL)) {
 263         return;
 264     }
 265     for (ep = Extensions->ExtensionBlocks;
 266          ep < (Extensions->ExtensionBlocks + Extensions->ExtensionBlockCount); ep++)
 267         ungif_free(ep->Bytes);
 268     ungif_free(Extensions->ExtensionBlocks);
 269     Extensions->ExtensionBlocks = NULL;
 270 }
 271
 272 /******************************************************************************
 273  * Image block allocation functions
 274 ******************************************************************************/
 275
 276 static void
 277 FreeSavedImages(GifFileType * GifFile) {
 278
 279     SavedImage *sp;
 280
 281     if ((GifFile == NULL) || (GifFile->SavedImages == NULL)) {
 282         return;
 283     }
 284     for (sp = GifFile->SavedImages;
 285          sp < GifFile->SavedImages + GifFile->ImageCount; sp++) {
 286         if (sp->ImageDesc.ColorMap) {
 287             FreeMapObject(sp->ImageDesc.ColorMap);
 288             sp->ImageDesc.ColorMap = NULL;
 289         }
 290
 291         ungif_free(sp->RasterBits);
 292
 293         if (sp->Extensions.ExtensionBlocks)
 294             FreeExtension(&sp->Extensions);
 295     }
 296     ungif_free(GifFile->SavedImages);
 297     GifFile->SavedImages=NULL;
 298 }
 299
 300 /******************************************************************************
 301  * This routine should be called before any other DGif calls. Note that
 302  * this routine is called automatically from DGif file open routines.
 303  *****************************************************************************/
 304 static int
 305 DGifGetScreenDesc(GifFileType * GifFile) {
 306
 307     int i, BitsPerPixel, SortFlag;
 308     GifByteType Buf[3];
 309
 310     /* Put the screen descriptor into the file: */
 311     if (DGifGetWord(GifFile, &GifFile->SWidth) == GIF_ERROR ||
 312         DGifGetWord(GifFile, &GifFile->SHeight) == GIF_ERROR)
 313         return GIF_ERROR;
 314
 315     if (READ(GifFile, Buf, 3) != 3) {
 316         return GIF_ERROR;
 317     }
 318     GifFile->SColorResolution = (((Buf[0] & 0x70) + 1) >> 4) + 1;
 319     SortFlag = (Buf[0] & 0x08) != 0;
 320     BitsPerPixel = (Buf[0] & 0x07) + 1;
 321     GifFile->SBackGroundColor = Buf[1];
 322     GifFile->SAspectRatio = Buf[2];
 323     if (Buf[0] & 0x80) {    /* Do we have global color map? */
 324
 325         GifFile->SColorMap = MakeMapObject(1 << BitsPerPixel, NULL);
 326         if (GifFile->SColorMap == NULL) {
 327             return GIF_ERROR;
 328         }
 329
 330         /* Get the global color map: */
 331         GifFile->SColorMap->SortFlag = SortFlag;
 332         for (i = 0; i < GifFile->SColorMap->ColorCount; i++) {
 333             if (READ(GifFile, Buf, 3) != 3) {
 334                 FreeMapObject(GifFile->SColorMap);
 335                 GifFile->SColorMap = NULL;
 336                 return GIF_ERROR;
 337             }
 338             GifFile->SColorMap->Colors[i].Red = Buf[0];
 339             GifFile->SColorMap->Colors[i].Green = Buf[1];
 340             GifFile->SColorMap->Colors[i].Blue = Buf[2];
 341         }
 342     } else {
 343         GifFile->SColorMap = NULL;
 344     }
 345
 346     return GIF_OK;
 347 }
 348
 349 /******************************************************************************
 350  * This routine should be called before any attempt to read an image.
 351  *****************************************************************************/
 352 static int
 353 DGifGetRecordType(GifFileType * GifFile,
 354                   GifRecordType * Type) {
 355
 356     GifByteType Buf;
 357
 358     if (READ(GifFile, &Buf, 1) != 1) {
 359         /* Wine-specific behavior: Native accepts broken GIF files that have no
 360          * terminator, so we match this by treating EOF as a terminator. */
 361         *Type = TERMINATE_RECORD_TYPE;
 362         return GIF_OK;
 363     }
 364
 365     switch (Buf) {
 366       case ',':
 367           *Type = IMAGE_DESC_RECORD_TYPE;
 368           break;
 369       case '!':
 370           *Type = EXTENSION_RECORD_TYPE;
 371           break;
 372       case ';':
 373           *Type = TERMINATE_RECORD_TYPE;
 374           break;
 375       default:
 376           *Type = UNDEFINED_RECORD_TYPE;
 377           return GIF_ERROR;
 378     }
 379
 380     return GIF_OK;
 381 }
 382
 383 /******************************************************************************
 384  * This routine should be called before any attempt to read an image.
 385  * Note it is assumed the Image desc. header (',') has been read.
 386  *****************************************************************************/
 387 static int
 388 DGifGetImageDesc(GifFileType * GifFile) {
 389
 390     int i, BitsPerPixel, SortFlag;
 391     GifByteType Buf[3];
 392     GifFilePrivateType *Private = GifFile->Private;
 393     SavedImage *sp;
 394
 395     if (DGifGetWord(GifFile, &GifFile->Image.Left) == GIF_ERROR ||
 396         DGifGetWord(GifFile, &GifFile->Image.Top) == GIF_ERROR ||
 397         DGifGetWord(GifFile, &GifFile->Image.Width) == GIF_ERROR ||
 398         DGifGetWord(GifFile, &GifFile->Image.Height) == GIF_ERROR)
 399         return GIF_ERROR;
 400     if (READ(GifFile, Buf, 1) != 1) {
 401         return GIF_ERROR;
 402     }
 403     BitsPerPixel = (Buf[0] & 0x07) + 1;
 404     SortFlag = (Buf[0] & 0x20) != 0;
 405     GifFile->Image.Interlace = (Buf[0] & 0x40);
 406     if (Buf[0] & 0x80) {    /* Does this image have local color map? */
 407
 408         FreeMapObject(GifFile->Image.ColorMap);
 409
 410         GifFile->Image.ColorMap = MakeMapObject(1 << BitsPerPixel, NULL);
 411         if (GifFile->Image.ColorMap == NULL) {
 412             return GIF_ERROR;
 413         }
 414
 415         /* Get the image local color map: */
 416         GifFile->Image.ColorMap->SortFlag = SortFlag;
 417         for (i = 0; i < GifFile->Image.ColorMap->ColorCount; i++) {
 418             if (READ(GifFile, Buf, 3) != 3) {
 419                 FreeMapObject(GifFile->Image.ColorMap);
 420                 GifFile->Image.ColorMap = NULL;
 421                 return GIF_ERROR;
 422             }
 423             GifFile->Image.ColorMap->Colors[i].Red = Buf[0];
 424             GifFile->Image.ColorMap->Colors[i].Green = Buf[1];
 425             GifFile->Image.ColorMap->Colors[i].Blue = Buf[2];
 426         }
 427     } else if (GifFile->Image.ColorMap) {
 428         FreeMapObject(GifFile->Image.ColorMap);
 429         GifFile->Image.ColorMap = NULL;
 430     }
 431
 432     if (GifFile->SavedImages) {
 433         if ((GifFile->SavedImages = ungif_realloc(GifFile->SavedImages,
 434                                       sizeof(SavedImage) *
 435                                       (GifFile->ImageCount + 1))) == NULL) {
 436             return GIF_ERROR;
 437         }
 438     } else {
 439         if ((GifFile->SavedImages = ungif_alloc(sizeof(SavedImage))) == NULL) {
 440             return GIF_ERROR;
 441         }
 442     }
 443
 444     sp = &GifFile->SavedImages[GifFile->ImageCount];
 445     sp->ImageDesc = GifFile->Image;
 446     if (GifFile->Image.ColorMap != NULL) {
 447         sp->ImageDesc.ColorMap = MakeMapObject(
 448                                  GifFile->Image.ColorMap->ColorCount,
 449                                  GifFile->Image.ColorMap->Colors);
 450         if (sp->ImageDesc.ColorMap == NULL) {
 451             return GIF_ERROR;
 452         }
 453         sp->ImageDesc.ColorMap->SortFlag = GifFile->Image.ColorMap->SortFlag;
 454     }
 455     sp->RasterBits = NULL;
 456     sp->Extensions.ExtensionBlockCount = 0;
 457     sp->Extensions.ExtensionBlocks = NULL;
 458
 459     GifFile->ImageCount++;
 460
 461     Private->PixelCount = (long)GifFile->Image.Width *
 462        (long)GifFile->Image.Height;
 463
 464     DGifSetupDecompress(GifFile);  /* Reset decompress algorithm parameters. */
 465
 466     return GIF_OK;
 467 }
 468
 469 /******************************************************************************
 470  * Get one full scanned line (Line) of length LineLen from GIF file.
 471  *****************************************************************************/
 472 static int
 473 DGifGetLine(GifFileType * GifFile,
 474             GifPixelType * Line,
 475             int LineLen) {
 476
 477     GifByteType *Dummy;
 478     GifFilePrivateType *Private = GifFile->Private;
 479
 480     if (!LineLen)
 481         LineLen = GifFile->Image.Width;
 482
 483     if ((Private->PixelCount -= LineLen) > 0xffff0000UL) {
 484         return GIF_ERROR;
 485     }
 486
 487     if (DGifDecompressLine(GifFile, Line, LineLen) == GIF_OK) {
 488         if (Private->PixelCount == 0) {
 489             /* We probably would not be called any more, so lets clean
 490              * everything before we return: need to flush out all rest of
 491              * image until empty block (size 0) detected. We use GetCodeNext. */
 492             do
 493                 if (DGifGetCodeNext(GifFile, &Dummy) == GIF_ERROR)
 494                     return GIF_ERROR;
 495             while (Dummy != NULL) ;
 496         }
 497         return GIF_OK;
 498     } else
 499         return GIF_ERROR;
 500 }
 501
 502 /******************************************************************************
 503  * Get an extension block (see GIF manual) from gif file. This routine only
 504  * returns the first data block, and DGifGetExtensionNext should be called
 505  * after this one until NULL extension is returned.
 506  * The Extension should NOT be freed by the user (not dynamically allocated).
 507  * Note it is assumed the Extension desc. header ('!') has been read.
 508  *****************************************************************************/
 509 static int
 510 DGifGetExtension(GifFileType * GifFile,
 511                  int *ExtCode,
 512                  GifByteType ** Extension) {
 513
 514     GifByteType Buf;
 515
 516     if (READ(GifFile, &Buf, 1) != 1) {
 517         return GIF_ERROR;
 518     }
 519     *ExtCode = Buf;
 520
 521     return DGifGetExtensionNext(GifFile, Extension);
 522 }
 523
 524 /******************************************************************************
 525  * Get a following extension block (see GIF manual) from gif file. This
 526  * routine should be called until NULL Extension is returned.
 527  * The Extension should NOT be freed by the user (not dynamically allocated).
 528  *****************************************************************************/
 529 static int
 530 DGifGetExtensionNext(GifFileType * GifFile,
 531                      GifByteType ** Extension) {
 532
 533     GifByteType Buf;
 534     GifFilePrivateType *Private = GifFile->Private;
 535
 536     if (READ(GifFile, &Buf, 1) != 1) {
 537         return GIF_ERROR;
 538     }
 539     if (Buf > 0) {
 540         *Extension = Private->Buf;    /* Use private unused buffer. */
 541         (*Extension)[0] = Buf;  /* Pascal strings notation (pos. 0 is len.). */
 542         if (READ(GifFile, &((*Extension)[1]), Buf) != Buf) {
 543             return GIF_ERROR;
 544         }
 545     } else
 546         *Extension = NULL;
 547
 548     return GIF_OK;
 549 }
 550
 551 /******************************************************************************
 552  * Get 2 bytes (word) from the given file:
 553  *****************************************************************************/
 554 static int
 555 DGifGetWord(GifFileType * GifFile,
 556             GifWord *Word) {
 557
 558     unsigned char c[2];
 559
 560     if (READ(GifFile, c, 2) != 2) {
 561         return GIF_ERROR;
 562     }
 563
 564     *Word = (((unsigned int)c[1]) << 8) + c[0];
 565     return GIF_OK;
 566 }
 567
 568 /******************************************************************************
 569  * Continue to get the image code in compressed form. This routine should be
 570  * called until NULL block is returned.
 571  * The block should NOT be freed by the user (not dynamically allocated).
 572  *****************************************************************************/
 573 static int
 574 DGifGetCodeNext(GifFileType * GifFile,
 575                 GifByteType ** CodeBlock) {
 576
 577     GifByteType Buf;
 578     GifFilePrivateType *Private = GifFile->Private;
 579
 580     if (READ(GifFile, &Buf, 1) != 1) {
 581         return GIF_ERROR;
 582     }
 583
 584     if (Buf > 0) {
 585         *CodeBlock = Private->Buf;    /* Use private unused buffer. */
 586         (*CodeBlock)[0] = Buf;  /* Pascal strings notation (pos. 0 is len.). */
 587         if (READ(GifFile, &((*CodeBlock)[1]), Buf) != Buf) {
 588             return GIF_ERROR;
 589         }
 590     } else {
 591         *CodeBlock = NULL;
 592         Private->Buf[0] = 0;    /* Make sure the buffer is empty! */
 593         Private->PixelCount = 0;    /* And local info. indicate image read. */
 594     }
 595
 596     return GIF_OK;
 597 }
 598
 599 /******************************************************************************
 600  * Setup the LZ decompression for this image:
 601  *****************************************************************************/
 602 static int
 603 DGifSetupDecompress(GifFileType * GifFile) {
 604
 605     int i, BitsPerPixel;
 606     GifByteType CodeSize;
 607     GifPrefixType *Prefix;
 608     GifFilePrivateType *Private = GifFile->Private;
 609
 610     READ(GifFile, &CodeSize, 1);    /* Read Code size from file. */
 611     BitsPerPixel = CodeSize;
 612
 613     Private->Buf[0] = 0;    /* Input Buffer empty. */
 614     Private->BitsPerPixel = BitsPerPixel;
 615     Private->ClearCode = (1 << BitsPerPixel);
 616     Private->EOFCode = Private->ClearCode + 1;
 617     Private->RunningCode = Private->EOFCode + 1;
 618     Private->RunningBits = BitsPerPixel + 1;    /* Number of bits per code. */
 619     Private->MaxCode1 = 1 << Private->RunningBits;    /* Max. code + 1. */
 620     Private->StackPtr = 0;    /* No pixels on the pixel stack. */
 621     Private->LastCode = NO_SUCH_CODE;
 622     Private->CrntShiftState = 0;    /* No information in CrntShiftDWord. */
 623     Private->CrntShiftDWord = 0;
 624
 625     Prefix = Private->Prefix;
 626     for (i = 0; i <= LZ_MAX_CODE; i++)
 627         Prefix[i] = NO_SUCH_CODE;
 628
 629     return GIF_OK;
 630 }
 631
 632 /******************************************************************************
 633  * The LZ decompression routine:
 634  * This version decompress the given gif file into Line of length LineLen.
 635  * This routine can be called few times (one per scan line, for example), in
 636  * order the complete the whole image.
 637  *****************************************************************************/
 638 static int
 639 DGifDecompressLine(GifFileType * GifFile,
 640                    GifPixelType * Line,
 641                    int LineLen) {
 642
 643     int i = 0;
 644     int j, CrntCode, EOFCode, ClearCode, CrntPrefix, LastCode, StackPtr;
 645     GifByteType *Stack, *Suffix;
 646     GifPrefixType *Prefix;
 647     GifFilePrivateType *Private = GifFile->Private;
 648
 649     StackPtr = Private->StackPtr;
 650     Prefix = Private->Prefix;
 651     Suffix = Private->Suffix;
 652     Stack = Private->Stack;
 653     EOFCode = Private->EOFCode;
 654     ClearCode = Private->ClearCode;
 655     LastCode = Private->LastCode;
 656
 657     if (StackPtr != 0) {
 658         /* Let pop the stack off before continuing to read the gif file: */
 659         while (StackPtr != 0 && i < LineLen)
 660             Line[i++] = Stack[--StackPtr];
 661     }
 662
 663     while (i < LineLen) {    /* Decode LineLen items. */
 664         if (DGifDecompressInput(GifFile, &CrntCode) == GIF_ERROR)
 665             return GIF_ERROR;
 666
 667         if (CrntCode == EOFCode) {
 668             /* Note, however, that usually we will not be here as we will stop
 669              * decoding as soon as we got all the pixel, or EOF code will
 670              * not be read at all, and DGifGetLine/Pixel clean everything.  */
 671             if (i != LineLen - 1 || Private->PixelCount != 0) {
 672                 return GIF_ERROR;
 673             }
 674             i++;
 675         } else if (CrntCode == ClearCode) {
 676             /* We need to start over again: */
 677             for (j = 0; j <= LZ_MAX_CODE; j++)
 678                 Prefix[j] = NO_SUCH_CODE;
 679             Private->RunningCode = Private->EOFCode + 1;
 680             Private->RunningBits = Private->BitsPerPixel + 1;
 681             Private->MaxCode1 = 1 << Private->RunningBits;
 682             LastCode = Private->LastCode = NO_SUCH_CODE;
 683         } else {
 684             /* It's a regular code - if in pixel range simply add it to output
 685              * stream, otherwise trace to codes linked list until the prefix
 686              * is in pixel range: */
 687             if (CrntCode < ClearCode) {
 688                 /* This is simple - its pixel scalar, so add it to output: */
 689                 Line[i++] = CrntCode;
 690             } else {
 691                 /* It's a code to be traced: trace the linked list
 692                  * until the prefix is a pixel, while pushing the suffix
 693                  * pixels on our stack. If we done, pop the stack in reverse
 694                  * order (that's what stack is good for!) for output.  */
 695                 if (Prefix[CrntCode] == NO_SUCH_CODE) {
 696                     /* Only allowed if CrntCode is exactly the running code:
 697                      * In that case CrntCode = XXXCode, CrntCode or the
 698                      * prefix code is last code and the suffix char is
 699                      * exactly the prefix of last code! */
 700                     if (CrntCode == Private->RunningCode - 2) {
 701                         CrntPrefix = LastCode;
 702                         Suffix[Private->RunningCode - 2] =
 703                            Stack[StackPtr++] = DGifGetPrefixChar(Prefix,
 704                                                                  LastCode,
 705                                                                  ClearCode);
 706                     } else {
 707                         return GIF_ERROR;
 708                     }
 709                 } else
 710                     CrntPrefix = CrntCode;
 711
 712                 /* Now (if image is O.K.) we should not get a NO_SUCH_CODE
 713                  * during the trace. As we might loop forever, in case of
 714                  * defective image, we count the number of loops we trace
 715                  * and stop if we got LZ_MAX_CODE. Obviously we cannot
 716                  * loop more than that.  */
 717                 j = 0;
 718                 while (j++ <= LZ_MAX_CODE &&
 719                        CrntPrefix > ClearCode && CrntPrefix <= LZ_MAX_CODE) {
 720                     Stack[StackPtr++] = Suffix[CrntPrefix];
 721                     CrntPrefix = Prefix[CrntPrefix];
 722                 }
 723                 if (j >= LZ_MAX_CODE || CrntPrefix > LZ_MAX_CODE) {
 724                     return GIF_ERROR;
 725                 }
 726                 /* Push the last character on stack: */
 727                 Stack[StackPtr++] = CrntPrefix;
 728
 729                 /* Now lets pop all the stack into output: */
 730                 while (StackPtr != 0 && i < LineLen)
 731                     Line[i++] = Stack[--StackPtr];
 732             }
 733             if (LastCode != NO_SUCH_CODE) {
 734                 Prefix[Private->RunningCode - 2] = LastCode;
 735
 736                 if (CrntCode == Private->RunningCode - 2) {
 737                     /* Only allowed if CrntCode is exactly the running code:
 738                      * In that case CrntCode = XXXCode, CrntCode or the
 739                      * prefix code is last code and the suffix char is
 740                      * exactly the prefix of last code! */
 741                     Suffix[Private->RunningCode - 2] =
 742                        DGifGetPrefixChar(Prefix, LastCode, ClearCode);
 743                 } else {
 744                     Suffix[Private->RunningCode - 2] =
 745                        DGifGetPrefixChar(Prefix, CrntCode, ClearCode);
 746                 }
 747             }
 748             LastCode = CrntCode;
 749         }
 750     }
 751
 752     Private->LastCode = LastCode;
 753     Private->StackPtr = StackPtr;
 754
 755     return GIF_OK;
 756 }
 757
 758 /******************************************************************************
 759  * Routine to trace the Prefixes linked list until we get a prefix which is
 760  * not code, but a pixel value (less than ClearCode). Returns that pixel value.
 761  * If image is defective, we might loop here forever, so we limit the loops to
 762  * the maximum possible if image O.k. - LZ_MAX_CODE times.
 763  *****************************************************************************/
 764 static int
 765 DGifGetPrefixChar(const GifPrefixType *Prefix,
 766                   int Code,
 767                   int ClearCode) {
 768
 769     int i = 0;
 770
 771     while (Code > ClearCode && i++ <= LZ_MAX_CODE)
 772         Code = Prefix[Code];
 773     return Code;
 774 }
 775
 776 /******************************************************************************
 777  * The LZ decompression input routine:
 778  * This routine is responsible for the decompression of the bit stream from
 779  * 8 bits (bytes) packets, into the real codes.
 780  * Returns GIF_OK if read successfully.
 781  *****************************************************************************/
 782 static int
 783 DGifDecompressInput(GifFileType * GifFile,
 784                     int *Code) {
 785
 786     GifFilePrivateType *Private = GifFile->Private;
 787
 788     GifByteType NextByte;
 789     static const unsigned short CodeMasks[] = {
 790         0x0000, 0x0001, 0x0003, 0x0007,
 791         0x000f, 0x001f, 0x003f, 0x007f,
 792         0x00ff, 0x01ff, 0x03ff, 0x07ff,
 793         0x0fff
 794     };
 795     /* The image can't contain more than LZ_BITS per code. */
 796     if (Private->RunningBits > LZ_BITS) {
 797         return GIF_ERROR;
 798     }
 799
 800     while (Private->CrntShiftState < Private->RunningBits) {
 801         /* Needs to get more bytes from input stream for next code: */
 802         if (DGifBufferedInput(GifFile, Private->Buf, &NextByte) == GIF_ERROR) {
 803             return GIF_ERROR;
 804         }
 805         Private->CrntShiftDWord |=
 806            ((unsigned long)NextByte) << Private->CrntShiftState;
 807         Private->CrntShiftState += 8;
 808     }
 809     *Code = Private->CrntShiftDWord & CodeMasks[Private->RunningBits];
 810
 811     Private->CrntShiftDWord >>= Private->RunningBits;
 812     Private->CrntShiftState -= Private->RunningBits;
 813
 814     /* If code cannot fit into RunningBits bits, must raise its size. Note
 815      * however that codes above 4095 are used for special signaling.
 816      * If we're using LZ_BITS bits already and we're at the max code, just
 817      * keep using the table as it is, don't increment Private->RunningCode.
 818      */
 819     if (Private->RunningCode < LZ_MAX_CODE + 2 &&
 820             ++Private->RunningCode > Private->MaxCode1 &&
 821             Private->RunningBits < LZ_BITS) {
 822         Private->MaxCode1 <<= 1;
 823         Private->RunningBits++;
 824     }
 825     return GIF_OK;
 826 }
 827
 828 /******************************************************************************
 829  * This routines read one gif data block at a time and buffers it internally
 830  * so that the decompression routine could access it.
 831  * The routine returns the next byte from its internal buffer (or read next
 832  * block in if buffer empty) and returns GIF_OK if successful.
 833  *****************************************************************************/
 834 static int
 835 DGifBufferedInput(GifFileType * GifFile,
 836                   GifByteType * Buf,
 837                   GifByteType * NextByte) {
 838
 839     if (Buf[0] == 0) {
 840         /* Needs to read the next buffer - this one is empty: */
 841         if (READ(GifFile, Buf, 1) != 1) {
 842             return GIF_ERROR;
 843         }
 844         /* There shouldn't be any empty data blocks here as the LZW spec
 845          * says the LZW termination code should come first.  Therefore we
 846          * shouldn't be inside this routine at that point.
 847          */
 848         if (Buf[0] == 0) {
 849             return GIF_ERROR;
 850         }
 851         if (READ(GifFile, &Buf[1], Buf[0]) != Buf[0]) {
 852             return GIF_ERROR;
 853         }
 854         *NextByte = Buf[1];
 855         Buf[1] = 2;    /* We use now the second place as last char read! */
 856         Buf[0]--;
 857     } else {
 858         *NextByte = Buf[Buf[1]++];
 859         Buf[0]--;
 860     }
 861
 862     return GIF_OK;
 863 }
 864
 865 /******************************************************************************
 866  * This routine reads an entire GIF into core, hanging all its state info off
 867  * the GifFileType pointer.  Call DGifOpenFileName() or DGifOpenFileHandle()
 868  * first to initialize I/O.  Its inverse is EGifSpew().
 869  ******************************************************************************/
 870 int
 871 DGifSlurp(GifFileType * GifFile) {
 872
 873     int ImageSize;
 874     GifRecordType RecordType;
 875     SavedImage *sp;
 876     GifByteType *ExtData;
 877     Extensions temp_save;
 878
 879     temp_save.ExtensionBlocks = NULL;
 880     temp_save.ExtensionBlockCount = 0;
 881
 882     do {
 883         if (DGifGetRecordType(GifFile, &RecordType) == GIF_ERROR)
 884             return (GIF_ERROR);
 885
 886         switch (RecordType) {
 887           case IMAGE_DESC_RECORD_TYPE:
 888               if (DGifGetImageDesc(GifFile) == GIF_ERROR)
 889                   return (GIF_ERROR);
 890
 891               sp = &GifFile->SavedImages[GifFile->ImageCount - 1];
 892               ImageSize = sp->ImageDesc.Width * sp->ImageDesc.Height;
 893
 894               sp->RasterBits = ungif_alloc(ImageSize * sizeof(GifPixelType));
 895               if (sp->RasterBits == NULL) {
 896                   return GIF_ERROR;
 897               }
 898               if (DGifGetLine(GifFile, sp->RasterBits, ImageSize) ==
 899                   GIF_ERROR)
 900                   return (GIF_ERROR);
 901               if (temp_save.ExtensionBlocks) {
 902                   sp->Extensions.ExtensionBlocks = temp_save.ExtensionBlocks;
 903                   sp->Extensions.ExtensionBlockCount = temp_save.ExtensionBlockCount;
 904
 905                   temp_save.ExtensionBlocks = NULL;
 906                   temp_save.ExtensionBlockCount = 0;
 907
 908                   /* FIXME: The following is wrong.  It is left in only for
 909                    * backwards compatibility.  Someday it should go away. Use
 910                    * the sp->ExtensionBlocks->Function variable instead. */
 911                   sp->Extensions.Function = sp->Extensions.ExtensionBlocks[0].Function;
 912               }
 913               break;
 914
 915           case EXTENSION_RECORD_TYPE:
 916           {
 917               int Function;
 918               Extensions *Extensions;
 919
 920               if (DGifGetExtension(GifFile, &Function, &ExtData) == GIF_ERROR)
 921                   return (GIF_ERROR);
 922
 923               if (GifFile->ImageCount || Function == GRAPHICS_EXT_FUNC_CODE)
 924                   Extensions = &temp_save;
 925               else
 926                   Extensions = &GifFile->Extensions;
 927
 928               Extensions->Function = Function;
 929
 930               /* Create an extension block with our data */
 931               if (AddExtensionBlock(Extensions, ExtData[0], &ExtData[1]) == GIF_ERROR)
 932                   return (GIF_ERROR);
 933
 934               while (ExtData != NULL) {
 935                   int Len;
 936                   GifByteType *Data;
 937
 938                   if (DGifGetExtensionNext(GifFile, &ExtData) == GIF_ERROR)
 939                       return (GIF_ERROR);
 940
 941                   if (ExtData)
 942                   {
 943                       Len = ExtData[0];
 944                       Data = &ExtData[1];
 945                   }
 946                   else
 947                   {
 948                       Len = 0;
 949                       Data = NULL;
 950                   }
 951
 952                   if (AppendExtensionBlock(Extensions, Len, Data) == GIF_ERROR)
 953                       return (GIF_ERROR);
 954               }
 955               break;
 956           }
 957
 958           case TERMINATE_RECORD_TYPE:
 959               break;
 960
 961           default:    /* Should be trapped by DGifGetRecordType */
 962               break;
 963         }
 964     } while (RecordType != TERMINATE_RECORD_TYPE);
 965
 966     /* Just in case the Gif has an extension block without an associated
 967      * image... (Should we save this into a savefile structure with no image
 968      * instead? Have to check if the present writing code can handle that as
 969      * well.... */
 970     if (temp_save.ExtensionBlocks)
 971         FreeExtension(&temp_save);
 972
 973     return (GIF_OK);
 974 }
 975
 976 /******************************************************************************
 977  * GifFileType constructor with user supplied input function (TVT)
 978  *****************************************************************************/
 979 GifFileType *
 980 DGifOpen(void *userData,
 981          InputFunc readFunc) {
 982
 983     unsigned char Buf[GIF_STAMP_LEN + 1];
 984     GifFileType *GifFile;
 985     GifFilePrivateType *Private;
 986
 987     GifFile = ungif_alloc(sizeof(GifFileType));
 988     if (GifFile == NULL) {
 989         return NULL;
 990     }
 991
 992     memset(GifFile, '\0', sizeof(GifFileType));
 993
 994     Private = ungif_alloc(sizeof(GifFilePrivateType));
 995     if (!Private) {
 996         ungif_free(GifFile);
 997         return NULL;
 998     }
 999
1000     GifFile->Private = (void*)Private;
1001
1002     Private->Read = readFunc;    /* TVT */
1003     GifFile->UserData = userData;    /* TVT */
1004
1005     /* Lets see if this is a GIF file: */
1006     if (READ(GifFile, Buf, GIF_STAMP_LEN) != GIF_STAMP_LEN) {
1007         ungif_free(Private);
1008         ungif_free(GifFile);
1009         return NULL;
1010     }
1011
1012     /* The GIF Version number is ignored at this time. Maybe we should do
1013      * something more useful with it. */
1014     Buf[GIF_STAMP_LEN] = 0;
1015     if (memcmp(GIF_STAMP, Buf, GIF_VERSION_POS) != 0) {
1016         ungif_free(Private);
1017         ungif_free(GifFile);
1018         return NULL;
1019     }
1020
1021     if (DGifGetScreenDesc(GifFile) == GIF_ERROR) {
1022         ungif_free(Private);
1023         ungif_free(GifFile);
1024         return NULL;
1025     }
1026
1027     return GifFile;
1028 }
1029
1030 /******************************************************************************
1031  * This routine should be called last, to close the GIF file.
1032  *****************************************************************************/
1033 int
1034 DGifCloseFile(GifFileType * GifFile) {
1035
1036     GifFilePrivateType *Private;
1037
1038     if (GifFile == NULL)
1039         return GIF_ERROR;
1040
1041     Private = GifFile->Private;
1042
1043     if (GifFile->Image.ColorMap) {
1044         FreeMapObject(GifFile->Image.ColorMap);
1045         GifFile->Image.ColorMap = NULL;
1046     }
1047
1048     if (GifFile->SColorMap) {
1049         FreeMapObject(GifFile->SColorMap);
1050         GifFile->SColorMap = NULL;
1051     }
1052
1053     ungif_free(Private);
1054     Private = NULL;
1055
1056     if (GifFile->SavedImages) {
1057         FreeSavedImages(GifFile);
1058         GifFile->SavedImages = NULL;
1059     }
1060
1061     FreeExtension(&GifFile->Extensions);
1062
1063     ungif_free(GifFile);
1064
1065     return GIF_OK;
1066 }