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