dll/win32/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 #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 NULL;
 152     }
 153
 154     Object = ungif_alloc(sizeof(ColorMapObject));
 155     if (Object == NULL) {
 156         return NULL;
 157     }
 158
 159     Object->Colors = ungif_calloc(ColorCount, sizeof(GifColorType));
 160     if (Object->Colors == 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         /* Wine-specific behavior: Native accepts broken GIF files that have no
 324          * terminator, so we match this by treating EOF as a terminator. */
 325         *Type = TERMINATE_RECORD_TYPE;
 326         return GIF_OK;
 327     }
 328
 329     switch (Buf) {
 330       case ',':
 331           *Type = IMAGE_DESC_RECORD_TYPE;
 332           break;
 333       case '!':
 334           *Type = EXTENSION_RECORD_TYPE;
 335           break;
 336       case ';':
 337           *Type = TERMINATE_RECORD_TYPE;
 338           break;
 339       default:
 340           *Type = UNDEFINED_RECORD_TYPE;
 341           return GIF_ERROR;
 342     }
 343
 344     return GIF_OK;
 345 }
 346
 347 /******************************************************************************
 348  * This routine should be called before any attempt to read an image.
 349  * Note it is assumed the Image desc. header (',') has been read.
 350  *****************************************************************************/
 351 static int
 352 DGifGetImageDesc(GifFileType * GifFile) {
 353
 354     int i, BitsPerPixel;
 355     GifByteType Buf[3];
 356     GifFilePrivateType *Private = GifFile->Private;
 357     SavedImage *sp;
 358
 359     if (DGifGetWord(GifFile, &GifFile->Image.Left) == GIF_ERROR ||
 360         DGifGetWord(GifFile, &GifFile->Image.Top) == GIF_ERROR ||
 361         DGifGetWord(GifFile, &GifFile->Image.Width) == GIF_ERROR ||
 362         DGifGetWord(GifFile, &GifFile->Image.Height) == GIF_ERROR)
 363         return GIF_ERROR;
 364     if (READ(GifFile, Buf, 1) != 1) {
 365         return GIF_ERROR;
 366     }
 367     BitsPerPixel = (Buf[0] & 0x07) + 1;
 368     GifFile->Image.Interlace = (Buf[0] & 0x40);
 369     if (Buf[0] & 0x80) {    /* Does this image have local color map? */
 370
 371         /*** FIXME: Why do we check both of these in order to do this?
 372          * Why do we have both Image and SavedImages? */
 373         if (GifFile->Image.ColorMap && GifFile->SavedImages == NULL)
 374             FreeMapObject(GifFile->Image.ColorMap);
 375
 376         GifFile->Image.ColorMap = MakeMapObject(1 << BitsPerPixel, NULL);
 377         if (GifFile->Image.ColorMap == NULL) {
 378             return GIF_ERROR;
 379         }
 380
 381         /* Get the image local color map: */
 382         for (i = 0; i < GifFile->Image.ColorMap->ColorCount; i++) {
 383             if (READ(GifFile, Buf, 3) != 3) {
 384                 FreeMapObject(GifFile->Image.ColorMap);
 385                 GifFile->Image.ColorMap = NULL;
 386                 return GIF_ERROR;
 387             }
 388             GifFile->Image.ColorMap->Colors[i].Red = Buf[0];
 389             GifFile->Image.ColorMap->Colors[i].Green = Buf[1];
 390             GifFile->Image.ColorMap->Colors[i].Blue = Buf[2];
 391         }
 392     } else if (GifFile->Image.ColorMap) {
 393         FreeMapObject(GifFile->Image.ColorMap);
 394         GifFile->Image.ColorMap = NULL;
 395     }
 396
 397     if (GifFile->SavedImages) {
 398         if ((GifFile->SavedImages = ungif_realloc(GifFile->SavedImages,
 399                                       sizeof(SavedImage) *
 400                                       (GifFile->ImageCount + 1))) == NULL) {
 401             return GIF_ERROR;
 402         }
 403     } else {
 404         if ((GifFile->SavedImages = ungif_alloc(sizeof(SavedImage))) == NULL) {
 405             return GIF_ERROR;
 406         }
 407     }
 408
 409     sp = &GifFile->SavedImages[GifFile->ImageCount];
 410     sp->ImageDesc = GifFile->Image;
 411     if (GifFile->Image.ColorMap != NULL) {
 412         sp->ImageDesc.ColorMap = MakeMapObject(
 413                                  GifFile->Image.ColorMap->ColorCount,
 414                                  GifFile->Image.ColorMap->Colors);
 415         if (sp->ImageDesc.ColorMap == NULL) {
 416             return GIF_ERROR;
 417         }
 418     }
 419     sp->RasterBits = NULL;
 420     sp->ExtensionBlockCount = 0;
 421     sp->ExtensionBlocks = NULL;
 422
 423     GifFile->ImageCount++;
 424
 425     Private->PixelCount = (long)GifFile->Image.Width *
 426        (long)GifFile->Image.Height;
 427
 428     DGifSetupDecompress(GifFile);  /* Reset decompress algorithm parameters. */
 429
 430     return GIF_OK;
 431 }
 432
 433 /******************************************************************************
 434  * Get one full scanned line (Line) of length LineLen from GIF file.
 435  *****************************************************************************/
 436 static int
 437 DGifGetLine(GifFileType * GifFile,
 438             GifPixelType * Line,
 439             int LineLen) {
 440
 441     GifByteType *Dummy;
 442     GifFilePrivateType *Private = GifFile->Private;
 443
 444     if (!LineLen)
 445         LineLen = GifFile->Image.Width;
 446
 447     if ((Private->PixelCount -= LineLen) > 0xffff0000UL) {
 448         return GIF_ERROR;
 449     }
 450
 451     if (DGifDecompressLine(GifFile, Line, LineLen) == GIF_OK) {
 452         if (Private->PixelCount == 0) {
 453             /* We probably would not be called any more, so lets clean
 454              * everything before we return: need to flush out all rest of
 455              * image until empty block (size 0) detected. We use GetCodeNext. */
 456             do
 457                 if (DGifGetCodeNext(GifFile, &Dummy) == GIF_ERROR)
 458                     return GIF_ERROR;
 459             while (Dummy != NULL) ;
 460         }
 461         return GIF_OK;
 462     } else
 463         return GIF_ERROR;
 464 }
 465
 466 /******************************************************************************
 467  * Get an extension block (see GIF manual) from gif file. This routine only
 468  * returns the first data block, and DGifGetExtensionNext should be called
 469  * after this one until NULL extension is returned.
 470  * The Extension should NOT be freed by the user (not dynamically allocated).
 471  * Note it is assumed the Extension desc. header ('!') has been read.
 472  *****************************************************************************/
 473 static int
 474 DGifGetExtension(GifFileType * GifFile,
 475                  int *ExtCode,
 476                  GifByteType ** Extension) {
 477
 478     GifByteType Buf;
 479
 480     if (READ(GifFile, &Buf, 1) != 1) {
 481         return GIF_ERROR;
 482     }
 483     *ExtCode = Buf;
 484
 485     return DGifGetExtensionNext(GifFile, Extension);
 486 }
 487
 488 /******************************************************************************
 489  * Get a following extension block (see GIF manual) from gif file. This
 490  * routine should be called until NULL Extension is returned.
 491  * The Extension should NOT be freed by the user (not dynamically allocated).
 492  *****************************************************************************/
 493 static int
 494 DGifGetExtensionNext(GifFileType * GifFile,
 495                      GifByteType ** Extension) {
 496
 497     GifByteType Buf;
 498     GifFilePrivateType *Private = GifFile->Private;
 499
 500     if (READ(GifFile, &Buf, 1) != 1) {
 501         return GIF_ERROR;
 502     }
 503     if (Buf > 0) {
 504         *Extension = Private->Buf;    /* Use private unused buffer. */
 505         (*Extension)[0] = Buf;  /* Pascal strings notation (pos. 0 is len.). */
 506         if (READ(GifFile, &((*Extension)[1]), Buf) != Buf) {
 507             return GIF_ERROR;
 508         }
 509     } else
 510         *Extension = NULL;
 511
 512     return GIF_OK;
 513 }
 514
 515 /******************************************************************************
 516  * Get 2 bytes (word) from the given file:
 517  *****************************************************************************/
 518 static int
 519 DGifGetWord(GifFileType * GifFile,
 520             GifWord *Word) {
 521
 522     unsigned char c[2];
 523
 524     if (READ(GifFile, c, 2) != 2) {
 525         return GIF_ERROR;
 526     }
 527
 528     *Word = (((unsigned int)c[1]) << 8) + c[0];
 529     return GIF_OK;
 530 }
 531
 532 /******************************************************************************
 533  * Continue to get the image code in compressed form. This routine should be
 534  * called until NULL block is returned.
 535  * The block should NOT be freed by the user (not dynamically allocated).
 536  *****************************************************************************/
 537 static int
 538 DGifGetCodeNext(GifFileType * GifFile,
 539                 GifByteType ** CodeBlock) {
 540
 541     GifByteType Buf;
 542     GifFilePrivateType *Private = GifFile->Private;
 543
 544     if (READ(GifFile, &Buf, 1) != 1) {
 545         return GIF_ERROR;
 546     }
 547
 548     if (Buf > 0) {
 549         *CodeBlock = Private->Buf;    /* Use private unused buffer. */
 550         (*CodeBlock)[0] = Buf;  /* Pascal strings notation (pos. 0 is len.). */
 551         if (READ(GifFile, &((*CodeBlock)[1]), Buf) != Buf) {
 552             return GIF_ERROR;
 553         }
 554     } else {
 555         *CodeBlock = NULL;
 556         Private->Buf[0] = 0;    /* Make sure the buffer is empty! */
 557         Private->PixelCount = 0;    /* And local info. indicate image read. */
 558     }
 559
 560     return GIF_OK;
 561 }
 562
 563 /******************************************************************************
 564  * Setup the LZ decompression for this image:
 565  *****************************************************************************/
 566 static int
 567 DGifSetupDecompress(GifFileType * GifFile) {
 568
 569     int i, BitsPerPixel;
 570     GifByteType CodeSize;
 571     GifPrefixType *Prefix;
 572     GifFilePrivateType *Private = GifFile->Private;
 573
 574     READ(GifFile, &CodeSize, 1);    /* Read Code size from file. */
 575     BitsPerPixel = CodeSize;
 576
 577     Private->Buf[0] = 0;    /* Input Buffer empty. */
 578     Private->BitsPerPixel = BitsPerPixel;
 579     Private->ClearCode = (1 << BitsPerPixel);
 580     Private->EOFCode = Private->ClearCode + 1;
 581     Private->RunningCode = Private->EOFCode + 1;
 582     Private->RunningBits = BitsPerPixel + 1;    /* Number of bits per code. */
 583     Private->MaxCode1 = 1 << Private->RunningBits;    /* Max. code + 1. */
 584     Private->StackPtr = 0;    /* No pixels on the pixel stack. */
 585     Private->LastCode = NO_SUCH_CODE;
 586     Private->CrntShiftState = 0;    /* No information in CrntShiftDWord. */
 587     Private->CrntShiftDWord = 0;
 588
 589     Prefix = Private->Prefix;
 590     for (i = 0; i <= LZ_MAX_CODE; i++)
 591         Prefix[i] = NO_SUCH_CODE;
 592
 593     return GIF_OK;
 594 }
 595
 596 /******************************************************************************
 597  * The LZ decompression routine:
 598  * This version decompress the given gif file into Line of length LineLen.
 599  * This routine can be called few times (one per scan line, for example), in
 600  * order the complete the whole image.
 601  *****************************************************************************/
 602 static int
 603 DGifDecompressLine(GifFileType * GifFile,
 604                    GifPixelType * Line,
 605                    int LineLen) {
 606
 607     int i = 0;
 608     int j, CrntCode, EOFCode, ClearCode, CrntPrefix, LastCode, StackPtr;
 609     GifByteType *Stack, *Suffix;
 610     GifPrefixType *Prefix;
 611     GifFilePrivateType *Private = GifFile->Private;
 612
 613     StackPtr = Private->StackPtr;
 614     Prefix = Private->Prefix;
 615     Suffix = Private->Suffix;
 616     Stack = Private->Stack;
 617     EOFCode = Private->EOFCode;
 618     ClearCode = Private->ClearCode;
 619     LastCode = Private->LastCode;
 620
 621     if (StackPtr != 0) {
 622         /* Let pop the stack off before continuing to read the gif file: */
 623         while (StackPtr != 0 && i < LineLen)
 624             Line[i++] = Stack[--StackPtr];
 625     }
 626
 627     while (i < LineLen) {    /* Decode LineLen items. */
 628         if (DGifDecompressInput(GifFile, &CrntCode) == GIF_ERROR)
 629             return GIF_ERROR;
 630
 631         if (CrntCode == EOFCode) {
 632             /* Note, however, that usually we will not be here as we will stop
 633              * decoding as soon as we got all the pixel, or EOF code will
 634              * not be read at all, and DGifGetLine/Pixel clean everything.  */
 635             if (i != LineLen - 1 || Private->PixelCount != 0) {
 636                 return GIF_ERROR;
 637             }
 638             i++;
 639         } else if (CrntCode == ClearCode) {
 640             /* We need to start over again: */
 641             for (j = 0; j <= LZ_MAX_CODE; j++)
 642                 Prefix[j] = NO_SUCH_CODE;
 643             Private->RunningCode = Private->EOFCode + 1;
 644             Private->RunningBits = Private->BitsPerPixel + 1;
 645             Private->MaxCode1 = 1 << Private->RunningBits;
 646             LastCode = Private->LastCode = NO_SUCH_CODE;
 647         } else {
 648             /* It's a regular code - if in pixel range simply add it to output
 649              * stream, otherwise trace to codes linked list until the prefix
 650              * is in pixel range: */
 651             if (CrntCode < ClearCode) {
 652                 /* This is simple - its pixel scalar, so add it to output: */
 653                 Line[i++] = CrntCode;
 654             } else {
 655                 /* It's a code to be traced: trace the linked list
 656                  * until the prefix is a pixel, while pushing the suffix
 657                  * pixels on our stack. If we done, pop the stack in reverse
 658                  * order (that's what stack is good for!) for output.  */
 659                 if (Prefix[CrntCode] == NO_SUCH_CODE) {
 660                     /* Only allowed if CrntCode is exactly the running code:
 661                      * In that case CrntCode = XXXCode, CrntCode or the
 662                      * prefix code is last code and the suffix char is
 663                      * exactly the prefix of last code! */
 664                     if (CrntCode == Private->RunningCode - 2) {
 665                         CrntPrefix = LastCode;
 666                         Suffix[Private->RunningCode - 2] =
 667                            Stack[StackPtr++] = DGifGetPrefixChar(Prefix,
 668                                                                  LastCode,
 669                                                                  ClearCode);
 670                     } else {
 671                         return GIF_ERROR;
 672                     }
 673                 } else
 674                     CrntPrefix = CrntCode;
 675
 676                 /* Now (if image is O.K.) we should not get a NO_SUCH_CODE
 677                  * during the trace. As we might loop forever, in case of
 678                  * defective image, we count the number of loops we trace
 679                  * and stop if we got LZ_MAX_CODE. Obviously we cannot
 680                  * loop more than that.  */
 681                 j = 0;
 682                 while (j++ <= LZ_MAX_CODE &&
 683                        CrntPrefix > ClearCode && CrntPrefix <= LZ_MAX_CODE) {
 684                     Stack[StackPtr++] = Suffix[CrntPrefix];
 685                     CrntPrefix = Prefix[CrntPrefix];
 686                 }
 687                 if (j >= LZ_MAX_CODE || CrntPrefix > LZ_MAX_CODE) {
 688                     return GIF_ERROR;
 689                 }
 690                 /* Push the last character on stack: */
 691                 Stack[StackPtr++] = CrntPrefix;
 692
 693                 /* Now lets pop all the stack into output: */
 694                 while (StackPtr != 0 && i < LineLen)
 695                     Line[i++] = Stack[--StackPtr];
 696             }
 697             if (LastCode != NO_SUCH_CODE) {
 698                 Prefix[Private->RunningCode - 2] = LastCode;
 699
 700                 if (CrntCode == Private->RunningCode - 2) {
 701                     /* Only allowed if CrntCode is exactly the running code:
 702                      * In that case CrntCode = XXXCode, CrntCode or the
 703                      * prefix code is last code and the suffix char is
 704                      * exactly the prefix of last code! */
 705                     Suffix[Private->RunningCode - 2] =
 706                        DGifGetPrefixChar(Prefix, LastCode, ClearCode);
 707                 } else {
 708                     Suffix[Private->RunningCode - 2] =
 709                        DGifGetPrefixChar(Prefix, CrntCode, ClearCode);
 710                 }
 711             }
 712             LastCode = CrntCode;
 713         }
 714     }
 715
 716     Private->LastCode = LastCode;
 717     Private->StackPtr = StackPtr;
 718
 719     return GIF_OK;
 720 }
 721
 722 /******************************************************************************
 723  * Routine to trace the Prefixes linked list until we get a prefix which is
 724  * not code, but a pixel value (less than ClearCode). Returns that pixel value.
 725  * If image is defective, we might loop here forever, so we limit the loops to
 726  * the maximum possible if image O.k. - LZ_MAX_CODE times.
 727  *****************************************************************************/
 728 static int
 729 DGifGetPrefixChar(const GifPrefixType *Prefix,
 730                   int Code,
 731                   int ClearCode) {
 732
 733     int i = 0;
 734
 735     while (Code > ClearCode && i++ <= LZ_MAX_CODE)
 736         Code = Prefix[Code];
 737     return Code;
 738 }
 739
 740 /******************************************************************************
 741  * The LZ decompression input routine:
 742  * This routine is responsible for the decompression of the bit stream from
 743  * 8 bits (bytes) packets, into the real codes.
 744  * Returns GIF_OK if read successfully.
 745  *****************************************************************************/
 746 static int
 747 DGifDecompressInput(GifFileType * GifFile,
 748                     int *Code) {
 749
 750     GifFilePrivateType *Private = GifFile->Private;
 751
 752     GifByteType NextByte;
 753     static const unsigned short CodeMasks[] = {
 754         0x0000, 0x0001, 0x0003, 0x0007,
 755         0x000f, 0x001f, 0x003f, 0x007f,
 756         0x00ff, 0x01ff, 0x03ff, 0x07ff,
 757         0x0fff
 758     };
 759     /* The image can't contain more than LZ_BITS per code. */
 760     if (Private->RunningBits > LZ_BITS) {
 761         return GIF_ERROR;
 762     }
 763
 764     while (Private->CrntShiftState < Private->RunningBits) {
 765         /* Needs to get more bytes from input stream for next code: */
 766         if (DGifBufferedInput(GifFile, Private->Buf, &NextByte) == GIF_ERROR) {
 767             return GIF_ERROR;
 768         }
 769         Private->CrntShiftDWord |=
 770            ((unsigned long)NextByte) << Private->CrntShiftState;
 771         Private->CrntShiftState += 8;
 772     }
 773     *Code = Private->CrntShiftDWord & CodeMasks[Private->RunningBits];
 774
 775     Private->CrntShiftDWord >>= Private->RunningBits;
 776     Private->CrntShiftState -= Private->RunningBits;
 777
 778     /* If code cannot fit into RunningBits bits, must raise its size. Note
 779      * however that codes above 4095 are used for special signaling.
 780      * If we're using LZ_BITS bits already and we're at the max code, just
 781      * keep using the table as it is, don't increment Private->RunningCode.
 782      */
 783     if (Private->RunningCode < LZ_MAX_CODE + 2 &&
 784             ++Private->RunningCode > Private->MaxCode1 &&
 785             Private->RunningBits < LZ_BITS) {
 786         Private->MaxCode1 <<= 1;
 787         Private->RunningBits++;
 788     }
 789     return GIF_OK;
 790 }
 791
 792 /******************************************************************************
 793  * This routines read one gif data block at a time and buffers it internally
 794  * so that the decompression routine could access it.
 795  * The routine returns the next byte from its internal buffer (or read next
 796  * block in if buffer empty) and returns GIF_OK if successful.
 797  *****************************************************************************/
 798 static int
 799 DGifBufferedInput(GifFileType * GifFile,
 800                   GifByteType * Buf,
 801                   GifByteType * NextByte) {
 802
 803     if (Buf[0] == 0) {
 804         /* Needs to read the next buffer - this one is empty: */
 805         if (READ(GifFile, Buf, 1) != 1) {
 806             return GIF_ERROR;
 807         }
 808         /* There shouldn't be any empty data blocks here as the LZW spec
 809          * says the LZW termination code should come first.  Therefore we
 810          * shouldn't be inside this routine at that point.
 811          */
 812         if (Buf[0] == 0) {
 813             return GIF_ERROR;
 814         }
 815         if (READ(GifFile, &Buf[1], Buf[0]) != Buf[0]) {
 816             return GIF_ERROR;
 817         }
 818         *NextByte = Buf[1];
 819         Buf[1] = 2;    /* We use now the second place as last char read! */
 820         Buf[0]--;
 821     } else {
 822         *NextByte = Buf[Buf[1]++];
 823         Buf[0]--;
 824     }
 825
 826     return GIF_OK;
 827 }
 828
 829 /******************************************************************************
 830  * This routine reads an entire GIF into core, hanging all its state info off
 831  * the GifFileType pointer.  Call DGifOpenFileName() or DGifOpenFileHandle()
 832  * first to initialize I/O.  Its inverse is EGifSpew().
 833  ******************************************************************************/
 834 int
 835 DGifSlurp(GifFileType * GifFile) {
 836
 837     int ImageSize;
 838     GifRecordType RecordType;
 839     SavedImage *sp;
 840     GifByteType *ExtData;
 841     SavedImage temp_save;
 842
 843     temp_save.ExtensionBlocks = NULL;
 844     temp_save.ExtensionBlockCount = 0;
 845
 846     do {
 847         if (DGifGetRecordType(GifFile, &RecordType) == GIF_ERROR)
 848             return (GIF_ERROR);
 849
 850         switch (RecordType) {
 851           case IMAGE_DESC_RECORD_TYPE:
 852               if (DGifGetImageDesc(GifFile) == GIF_ERROR)
 853                   return (GIF_ERROR);
 854
 855               sp = &GifFile->SavedImages[GifFile->ImageCount - 1];
 856               ImageSize = sp->ImageDesc.Width * sp->ImageDesc.Height;
 857
 858               sp->RasterBits = ungif_alloc(ImageSize * sizeof(GifPixelType));
 859               if (sp->RasterBits == NULL) {
 860                   return GIF_ERROR;
 861               }
 862               if (DGifGetLine(GifFile, sp->RasterBits, ImageSize) ==
 863                   GIF_ERROR)
 864                   return (GIF_ERROR);
 865               if (temp_save.ExtensionBlocks) {
 866                   sp->ExtensionBlocks = temp_save.ExtensionBlocks;
 867                   sp->ExtensionBlockCount = temp_save.ExtensionBlockCount;
 868
 869                   temp_save.ExtensionBlocks = NULL;
 870                   temp_save.ExtensionBlockCount = 0;
 871
 872                   /* FIXME: The following is wrong.  It is left in only for
 873                    * backwards compatibility.  Someday it should go away. Use
 874                    * the sp->ExtensionBlocks->Function variable instead. */
 875                   sp->Function = sp->ExtensionBlocks[0].Function;
 876               }
 877               break;
 878
 879           case EXTENSION_RECORD_TYPE:
 880               if (DGifGetExtension(GifFile, &temp_save.Function, &ExtData) ==
 881                   GIF_ERROR)
 882                   return (GIF_ERROR);
 883               while (ExtData != NULL) {
 884
 885                   /* Create an extension block with our data */
 886                   if (AddExtensionBlock(&temp_save, ExtData[0], &ExtData[1])
 887                       == GIF_ERROR)
 888                       return (GIF_ERROR);
 889
 890                   if (DGifGetExtensionNext(GifFile, &ExtData) == GIF_ERROR)
 891                       return (GIF_ERROR);
 892                   temp_save.Function = 0;
 893               }
 894               break;
 895
 896           case TERMINATE_RECORD_TYPE:
 897               break;
 898
 899           default:    /* Should be trapped by DGifGetRecordType */
 900               break;
 901         }
 902     } while (RecordType != TERMINATE_RECORD_TYPE);
 903
 904     /* Just in case the Gif has an extension block without an associated
 905      * image... (Should we save this into a savefile structure with no image
 906      * instead? Have to check if the present writing code can handle that as
 907      * well.... */
 908     if (temp_save.ExtensionBlocks)
 909         FreeExtension(&temp_save);
 910
 911     return (GIF_OK);
 912 }
 913
 914 /******************************************************************************
 915  * GifFileType constructor with user supplied input function (TVT)
 916  *****************************************************************************/
 917 GifFileType *
 918 DGifOpen(void *userData,
 919          InputFunc readFunc) {
 920
 921     unsigned char Buf[GIF_STAMP_LEN + 1];
 922     GifFileType *GifFile;
 923     GifFilePrivateType *Private;
 924
 925     GifFile = ungif_alloc(sizeof(GifFileType));
 926     if (GifFile == NULL) {
 927         return NULL;
 928     }
 929
 930     memset(GifFile, '\0', sizeof(GifFileType));
 931
 932     Private = ungif_alloc(sizeof(GifFilePrivateType));
 933     if (!Private) {
 934         ungif_free(GifFile);
 935         return NULL;
 936     }
 937
 938     GifFile->Private = (void*)Private;
 939
 940     Private->Read = readFunc;    /* TVT */
 941     GifFile->UserData = userData;    /* TVT */
 942
 943     /* Lets see if this is a GIF file: */
 944     if (READ(GifFile, Buf, GIF_STAMP_LEN) != GIF_STAMP_LEN) {
 945         ungif_free(Private);
 946         ungif_free(GifFile);
 947         return NULL;
 948     }
 949
 950     /* The GIF Version number is ignored at this time. Maybe we should do
 951      * something more useful with it. */
 952     Buf[GIF_STAMP_LEN] = 0;
 953     if (memcmp(GIF_STAMP, Buf, GIF_VERSION_POS) != 0) {
 954         ungif_free(Private);
 955         ungif_free(GifFile);
 956         return NULL;
 957     }
 958
 959     if (DGifGetScreenDesc(GifFile) == GIF_ERROR) {
 960         ungif_free(Private);
 961         ungif_free(GifFile);
 962         return NULL;
 963     }
 964
 965     return GifFile;
 966 }
 967
 968 /******************************************************************************
 969  * This routine should be called last, to close the GIF file.
 970  *****************************************************************************/
 971 int
 972 DGifCloseFile(GifFileType * GifFile) {
 973
 974     GifFilePrivateType *Private;
 975
 976     if (GifFile == NULL)
 977         return GIF_ERROR;
 978
 979     Private = GifFile->Private;
 980
 981     if (GifFile->Image.ColorMap) {
 982         FreeMapObject(GifFile->Image.ColorMap);
 983         GifFile->Image.ColorMap = NULL;
 984     }
 985
 986     if (GifFile->SColorMap) {
 987         FreeMapObject(GifFile->SColorMap);
 988         GifFile->SColorMap = NULL;
 989     }
 990
 991     ungif_free(Private);
 992     Private = NULL;
 993
 994     if (GifFile->SavedImages) {
 995         FreeSavedImages(GifFile);
 996         GifFile->SavedImages = NULL;
 997     }
 998
 999     ungif_free(GifFile);
1000
1001     return GIF_OK;
1002 }