reactos/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
  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         /*** FIXME: Why do we check both of these in order to do this?
 409          * Why do we have both Image and SavedImages? */
 410         if (GifFile->Image.ColorMap && GifFile->SavedImages == NULL)
 411             FreeMapObject(GifFile->Image.ColorMap);
 412
 413         GifFile->Image.ColorMap = MakeMapObject(1 << BitsPerPixel, NULL);
 414         if (GifFile->Image.ColorMap == NULL) {
 415             return GIF_ERROR;
 416         }
 417
 418         /* Get the image local color map: */
 419         GifFile->Image.ColorMap->SortFlag = SortFlag;
 420         for (i = 0; i < GifFile->Image.ColorMap->ColorCount; i++) {
 421             if (READ(GifFile, Buf, 3) != 3) {
 422                 FreeMapObject(GifFile->Image.ColorMap);
 423                 GifFile->Image.ColorMap = NULL;
 424                 return GIF_ERROR;
 425             }
 426             GifFile->Image.ColorMap->Colors[i].Red = Buf[0];
 427             GifFile->Image.ColorMap->Colors[i].Green = Buf[1];
 428             GifFile->Image.ColorMap->Colors[i].Blue = Buf[2];
 429         }
 430     } else if (GifFile->Image.ColorMap) {
 431         FreeMapObject(GifFile->Image.ColorMap);
 432         GifFile->Image.ColorMap = NULL;
 433     }
 434
 435     if (GifFile->SavedImages) {
 436         if ((GifFile->SavedImages = ungif_realloc(GifFile->SavedImages,
 437                                       sizeof(SavedImage) *
 438                                       (GifFile->ImageCount + 1))) == NULL) {
 439             return GIF_ERROR;
 440         }
 441     } else {
 442         if ((GifFile->SavedImages = ungif_alloc(sizeof(SavedImage))) == NULL) {
 443             return GIF_ERROR;
 444         }
 445     }
 446
 447     sp = &GifFile->SavedImages[GifFile->ImageCount];
 448     sp->ImageDesc = GifFile->Image;
 449     if (GifFile->Image.ColorMap != NULL) {
 450         sp->ImageDesc.ColorMap = MakeMapObject(
 451                                  GifFile->Image.ColorMap->ColorCount,
 452                                  GifFile->Image.ColorMap->Colors);
 453         if (sp->ImageDesc.ColorMap == NULL) {
 454             return GIF_ERROR;
 455         }
 456         sp->ImageDesc.ColorMap->SortFlag = GifFile->Image.ColorMap->SortFlag;
 457     }
 458     sp->RasterBits = NULL;
 459     sp->Extensions.ExtensionBlockCount = 0;
 460     sp->Extensions.ExtensionBlocks = NULL;
 461
 462     GifFile->ImageCount++;
 463
 464     Private->PixelCount = (long)GifFile->Image.Width *
 465        (long)GifFile->Image.Height;
 466
 467     DGifSetupDecompress(GifFile);  /* Reset decompress algorithm parameters. */
 468
 469     return GIF_OK;
 470 }
 471
 472 /******************************************************************************
 473  * Get one full scanned line (Line) of length LineLen from GIF file.
 474  *****************************************************************************/
 475 static int
 476 DGifGetLine(GifFileType * GifFile,
 477             GifPixelType * Line,
 478             int LineLen) {
 479
 480     GifByteType *Dummy;
 481     GifFilePrivateType *Private = GifFile->Private;
 482
 483     if (!LineLen)
 484         LineLen = GifFile->Image.Width;
 485
 486     if ((Private->PixelCount -= LineLen) > 0xffff0000UL) {
 487         return GIF_ERROR;
 488     }
 489
 490     if (DGifDecompressLine(GifFile, Line, LineLen) == GIF_OK) {
 491         if (Private->PixelCount == 0) {
 492             /* We probably would not be called any more, so lets clean
 493              * everything before we return: need to flush out all rest of
 494              * image until empty block (size 0) detected. We use GetCodeNext. */
 495             do
 496                 if (DGifGetCodeNext(GifFile, &Dummy) == GIF_ERROR)
 497                     return GIF_ERROR;
 498             while (Dummy != NULL) ;
 499         }
 500         return GIF_OK;
 501     } else
 502         return GIF_ERROR;
 503 }
 504
 505 /******************************************************************************
 506  * Get an extension block (see GIF manual) from gif file. This routine only
 507  * returns the first data block, and DGifGetExtensionNext should be called
 508  * after this one until NULL extension is returned.
 509  * The Extension should NOT be freed by the user (not dynamically allocated).
 510  * Note it is assumed the Extension desc. header ('!') has been read.
 511  *****************************************************************************/
 512 static int
 513 DGifGetExtension(GifFileType * GifFile,
 514                  int *ExtCode,
 515                  GifByteType ** Extension) {
 516
 517     GifByteType Buf;
 518
 519     if (READ(GifFile, &Buf, 1) != 1) {
 520         return GIF_ERROR;
 521     }
 522     *ExtCode = Buf;
 523
 524     return DGifGetExtensionNext(GifFile, Extension);
 525 }
 526
 527 /******************************************************************************
 528  * Get a following extension block (see GIF manual) from gif file. This
 529  * routine should be called until NULL Extension is returned.
 530  * The Extension should NOT be freed by the user (not dynamically allocated).
 531  *****************************************************************************/
 532 static int
 533 DGifGetExtensionNext(GifFileType * GifFile,
 534                      GifByteType ** Extension) {
 535
 536     GifByteType Buf;
 537     GifFilePrivateType *Private = GifFile->Private;
 538
 539     if (READ(GifFile, &Buf, 1) != 1) {
 540         return GIF_ERROR;
 541     }
 542     if (Buf > 0) {
 543         *Extension = Private->Buf;    /* Use private unused buffer. */
 544         (*Extension)[0] = Buf;  /* Pascal strings notation (pos. 0 is len.). */
 545         if (READ(GifFile, &((*Extension)[1]), Buf) != Buf) {
 546             return GIF_ERROR;
 547         }
 548     } else
 549         *Extension = NULL;
 550
 551     return GIF_OK;
 552 }
 553
 554 /******************************************************************************
 555  * Get 2 bytes (word) from the given file:
 556  *****************************************************************************/
 557 static int
 558 DGifGetWord(GifFileType * GifFile,
 559             GifWord *Word) {
 560
 561     unsigned char c[2];
 562
 563     if (READ(GifFile, c, 2) != 2) {
 564         return GIF_ERROR;
 565     }
 566
 567     *Word = (((unsigned int)c[1]) << 8) + c[0];
 568     return GIF_OK;
 569 }
 570
 571 /******************************************************************************
 572  * Continue to get the image code in compressed form. This routine should be
 573  * called until NULL block is returned.
 574  * The block should NOT be freed by the user (not dynamically allocated).
 575  *****************************************************************************/
 576 static int
 577 DGifGetCodeNext(GifFileType * GifFile,
 578                 GifByteType ** CodeBlock) {
 579
 580     GifByteType Buf;
 581     GifFilePrivateType *Private = GifFile->Private;
 582
 583     if (READ(GifFile, &Buf, 1) != 1) {
 584         return GIF_ERROR;
 585     }
 586
 587     if (Buf > 0) {
 588         *CodeBlock = Private->Buf;    /* Use private unused buffer. */
 589         (*CodeBlock)[0] = Buf;  /* Pascal strings notation (pos. 0 is len.). */
 590         if (READ(GifFile, &((*CodeBlock)[1]), Buf) != Buf) {
 591             return GIF_ERROR;
 592         }
 593     } else {
 594         *CodeBlock = NULL;
 595         Private->Buf[0] = 0;    /* Make sure the buffer is empty! */
 596         Private->PixelCount = 0;    /* And local info. indicate image read. */
 597     }
 598
 599     return GIF_OK;
 600 }
 601
 602 /******************************************************************************
 603  * Setup the LZ decompression for this image:
 604  *****************************************************************************/
 605 static int
 606 DGifSetupDecompress(GifFileType * GifFile) {
 607
 608     int i, BitsPerPixel;
 609     GifByteType CodeSize;
 610     GifPrefixType *Prefix;
 611     GifFilePrivateType *Private = GifFile->Private;
 612
 613     READ(GifFile, &CodeSize, 1);    /* Read Code size from file. */
 614     BitsPerPixel = CodeSize;
 615
 616     Private->Buf[0] = 0;    /* Input Buffer empty. */
 617     Private->BitsPerPixel = BitsPerPixel;
 618     Private->ClearCode = (1 << BitsPerPixel);
 619     Private->EOFCode = Private->ClearCode + 1;
 620     Private->RunningCode = Private->EOFCode + 1;
 621     Private->RunningBits = BitsPerPixel + 1;    /* Number of bits per code. */
 622     Private->MaxCode1 = 1 << Private->RunningBits;    /* Max. code + 1. */
 623     Private->StackPtr = 0;    /* No pixels on the pixel stack. */
 624     Private->LastCode = NO_SUCH_CODE;
 625     Private->CrntShiftState = 0;    /* No information in CrntShiftDWord. */
 626     Private->CrntShiftDWord = 0;
 627
 628     Prefix = Private->Prefix;
 629     for (i = 0; i <= LZ_MAX_CODE; i++)
 630         Prefix[i] = NO_SUCH_CODE;
 631
 632     return GIF_OK;
 633 }
 634
 635 /******************************************************************************
 636  * The LZ decompression routine:
 637  * This version decompress the given gif file into Line of length LineLen.
 638  * This routine can be called few times (one per scan line, for example), in
 639  * order the complete the whole image.
 640  *****************************************************************************/
 641 static int
 642 DGifDecompressLine(GifFileType * GifFile,
 643                    GifPixelType * Line,
 644                    int LineLen) {
 645
 646     int i = 0;
 647     int j, CrntCode, EOFCode, ClearCode, CrntPrefix, LastCode, StackPtr;
 648     GifByteType *Stack, *Suffix;
 649     GifPrefixType *Prefix;
 650     GifFilePrivateType *Private = GifFile->Private;
 651
 652     StackPtr = Private->StackPtr;
 653     Prefix = Private->Prefix;
 654     Suffix = Private->Suffix;
 655     Stack = Private->Stack;
 656     EOFCode = Private->EOFCode;
 657     ClearCode = Private->ClearCode;
 658     LastCode = Private->LastCode;
 659
 660     if (StackPtr != 0) {
 661         /* Let pop the stack off before continuing to read the gif file: */
 662         while (StackPtr != 0 && i < LineLen)
 663             Line[i++] = Stack[--StackPtr];
 664     }
 665
 666     while (i < LineLen) {    /* Decode LineLen items. */
 667         if (DGifDecompressInput(GifFile, &CrntCode) == GIF_ERROR)
 668             return GIF_ERROR;
 669
 670         if (CrntCode == EOFCode) {
 671             /* Note, however, that usually we will not be here as we will stop
 672              * decoding as soon as we got all the pixel, or EOF code will
 673              * not be read at all, and DGifGetLine/Pixel clean everything.  */
 674             if (i != LineLen - 1 || Private->PixelCount != 0) {
 675                 return GIF_ERROR;
 676             }
 677             i++;
 678         } else if (CrntCode == ClearCode) {
 679             /* We need to start over again: */
 680             for (j = 0; j <= LZ_MAX_CODE; j++)
 681                 Prefix[j] = NO_SUCH_CODE;
 682             Private->RunningCode = Private->EOFCode + 1;
 683             Private->RunningBits = Private->BitsPerPixel + 1;
 684             Private->MaxCode1 = 1 << Private->RunningBits;
 685             LastCode = Private->LastCode = NO_SUCH_CODE;
 686         } else {
 687             /* It's a regular code - if in pixel range simply add it to output
 688              * stream, otherwise trace to codes linked list until the prefix
 689              * is in pixel range: */
 690             if (CrntCode < ClearCode) {
 691                 /* This is simple - its pixel scalar, so add it to output: */
 692                 Line[i++] = CrntCode;
 693             } else {
 694                 /* It's a code to be traced: trace the linked list
 695                  * until the prefix is a pixel, while pushing the suffix
 696                  * pixels on our stack. If we done, pop the stack in reverse
 697                  * order (that's what stack is good for!) for output.  */
 698                 if (Prefix[CrntCode] == NO_SUCH_CODE) {
 699                     /* Only allowed if CrntCode is exactly the running code:
 700                      * In that case CrntCode = XXXCode, CrntCode or the
 701                      * prefix code is last code and the suffix char is
 702                      * exactly the prefix of last code! */
 703                     if (CrntCode == Private->RunningCode - 2) {
 704                         CrntPrefix = LastCode;
 705                         Suffix[Private->RunningCode - 2] =
 706                            Stack[StackPtr++] = DGifGetPrefixChar(Prefix,
 707                                                                  LastCode,
 708                                                                  ClearCode);
 709                     } else {
 710                         return GIF_ERROR;
 711                     }
 712                 } else
 713                     CrntPrefix = CrntCode;
 714
 715                 /* Now (if image is O.K.) we should not get a NO_SUCH_CODE
 716                  * during the trace. As we might loop forever, in case of
 717                  * defective image, we count the number of loops we trace
 718                  * and stop if we got LZ_MAX_CODE. Obviously we cannot
 719                  * loop more than that.  */
 720                 j = 0;
 721                 while (j++ <= LZ_MAX_CODE &&
 722                        CrntPrefix > ClearCode && CrntPrefix <= LZ_MAX_CODE) {
 723                     Stack[StackPtr++] = Suffix[CrntPrefix];
 724                     CrntPrefix = Prefix[CrntPrefix];
 725                 }
 726                 if (j >= LZ_MAX_CODE || CrntPrefix > LZ_MAX_CODE) {
 727                     return GIF_ERROR;
 728                 }
 729                 /* Push the last character on stack: */
 730                 Stack[StackPtr++] = CrntPrefix;
 731
 732                 /* Now lets pop all the stack into output: */
 733                 while (StackPtr != 0 && i < LineLen)
 734                     Line[i++] = Stack[--StackPtr];
 735             }
 736             if (LastCode != NO_SUCH_CODE) {
 737                 Prefix[Private->RunningCode - 2] = LastCode;
 738
 739                 if (CrntCode == Private->RunningCode - 2) {
 740                     /* Only allowed if CrntCode is exactly the running code:
 741                      * In that case CrntCode = XXXCode, CrntCode or the
 742                      * prefix code is last code and the suffix char is
 743                      * exactly the prefix of last code! */
 744                     Suffix[Private->RunningCode - 2] =
 745                        DGifGetPrefixChar(Prefix, LastCode, ClearCode);
 746                 } else {
 747                     Suffix[Private->RunningCode - 2] =
 748                        DGifGetPrefixChar(Prefix, CrntCode, ClearCode);
 749                 }
 750             }
 751             LastCode = CrntCode;
 752         }
 753     }
 754
 755     Private->LastCode = LastCode;
 756     Private->StackPtr = StackPtr;
 757
 758     return GIF_OK;
 759 }
 760
 761 /******************************************************************************
 762  * Routine to trace the Prefixes linked list until we get a prefix which is
 763  * not code, but a pixel value (less than ClearCode). Returns that pixel value.
 764  * If image is defective, we might loop here forever, so we limit the loops to
 765  * the maximum possible if image O.k. - LZ_MAX_CODE times.
 766  *****************************************************************************/
 767 static int
 768 DGifGetPrefixChar(const GifPrefixType *Prefix,
 769                   int Code,
 770                   int ClearCode) {
 771
 772     int i = 0;
 773
 774     while (Code > ClearCode && i++ <= LZ_MAX_CODE)
 775         Code = Prefix[Code];
 776     return Code;
 777 }
 778
 779 /******************************************************************************
 780  * The LZ decompression input routine:
 781  * This routine is responsible for the decompression of the bit stream from
 782  * 8 bits (bytes) packets, into the real codes.
 783  * Returns GIF_OK if read successfully.
 784  *****************************************************************************/
 785 static int
 786 DGifDecompressInput(GifFileType * GifFile,
 787                     int *Code) {
 788
 789     GifFilePrivateType *Private = GifFile->Private;
 790
 791     GifByteType NextByte;
 792     static const unsigned short CodeMasks[] = {
 793         0x0000, 0x0001, 0x0003, 0x0007,
 794         0x000f, 0x001f, 0x003f, 0x007f,
 795         0x00ff, 0x01ff, 0x03ff, 0x07ff,
 796         0x0fff
 797     };
 798     /* The image can't contain more than LZ_BITS per code. */
 799     if (Private->RunningBits > LZ_BITS) {
 800         return GIF_ERROR;
 801     }
 802
 803     while (Private->CrntShiftState < Private->RunningBits) {
 804         /* Needs to get more bytes from input stream for next code: */
 805         if (DGifBufferedInput(GifFile, Private->Buf, &NextByte) == GIF_ERROR) {
 806             return GIF_ERROR;
 807         }
 808         Private->CrntShiftDWord |=
 809            ((unsigned long)NextByte) << Private->CrntShiftState;
 810         Private->CrntShiftState += 8;
 811     }
 812     *Code = Private->CrntShiftDWord & CodeMasks[Private->RunningBits];
 813
 814     Private->CrntShiftDWord >>= Private->RunningBits;
 815     Private->CrntShiftState -= Private->RunningBits;
 816
 817     /* If code cannot fit into RunningBits bits, must raise its size. Note
 818      * however that codes above 4095 are used for special signaling.
 819      * If we're using LZ_BITS bits already and we're at the max code, just
 820      * keep using the table as it is, don't increment Private->RunningCode.
 821      */
 822     if (Private->RunningCode < LZ_MAX_CODE + 2 &&
 823             ++Private->RunningCode > Private->MaxCode1 &&
 824             Private->RunningBits < LZ_BITS) {
 825         Private->MaxCode1 <<= 1;
 826         Private->RunningBits++;
 827     }
 828     return GIF_OK;
 829 }
 830
 831 /******************************************************************************
 832  * This routines read one gif data block at a time and buffers it internally
 833  * so that the decompression routine could access it.
 834  * The routine returns the next byte from its internal buffer (or read next
 835  * block in if buffer empty) and returns GIF_OK if successful.
 836  *****************************************************************************/
 837 static int
 838 DGifBufferedInput(GifFileType * GifFile,
 839                   GifByteType * Buf,
 840                   GifByteType * NextByte) {
 841
 842     if (Buf[0] == 0) {
 843         /* Needs to read the next buffer - this one is empty: */
 844         if (READ(GifFile, Buf, 1) != 1) {
 845             return GIF_ERROR;
 846         }
 847         /* There shouldn't be any empty data blocks here as the LZW spec
 848          * says the LZW termination code should come first.  Therefore we
 849          * shouldn't be inside this routine at that point.
 850          */
 851         if (Buf[0] == 0) {
 852             return GIF_ERROR;
 853         }
 854         if (READ(GifFile, &Buf[1], Buf[0]) != Buf[0]) {
 855             return GIF_ERROR;
 856         }
 857         *NextByte = Buf[1];
 858         Buf[1] = 2;    /* We use now the second place as last char read! */
 859         Buf[0]--;
 860     } else {
 861         *NextByte = Buf[Buf[1]++];
 862         Buf[0]--;
 863     }
 864
 865     return GIF_OK;
 866 }
 867
 868 /******************************************************************************
 869  * This routine reads an entire GIF into core, hanging all its state info off
 870  * the GifFileType pointer.  Call DGifOpenFileName() or DGifOpenFileHandle()
 871  * first to initialize I/O.  Its inverse is EGifSpew().
 872  ******************************************************************************/
 873 int
 874 DGifSlurp(GifFileType * GifFile) {
 875
 876     int ImageSize;
 877     GifRecordType RecordType;
 878     SavedImage *sp;
 879     GifByteType *ExtData;
 880     Extensions temp_save;
 881
 882     temp_save.ExtensionBlocks = NULL;
 883     temp_save.ExtensionBlockCount = 0;
 884
 885     do {
 886         if (DGifGetRecordType(GifFile, &RecordType) == GIF_ERROR)
 887             return (GIF_ERROR);
 888
 889         switch (RecordType) {
 890           case IMAGE_DESC_RECORD_TYPE:
 891               if (DGifGetImageDesc(GifFile) == GIF_ERROR)
 892                   return (GIF_ERROR);
 893
 894               sp = &GifFile->SavedImages[GifFile->ImageCount - 1];
 895               ImageSize = sp->ImageDesc.Width * sp->ImageDesc.Height;
 896
 897               sp->RasterBits = ungif_alloc(ImageSize * sizeof(GifPixelType));
 898               if (sp->RasterBits == NULL) {
 899                   return GIF_ERROR;
 900               }
 901               if (DGifGetLine(GifFile, sp->RasterBits, ImageSize) ==
 902                   GIF_ERROR)
 903                   return (GIF_ERROR);
 904               if (temp_save.ExtensionBlocks) {
 905                   sp->Extensions.ExtensionBlocks = temp_save.ExtensionBlocks;
 906                   sp->Extensions.ExtensionBlockCount = temp_save.ExtensionBlockCount;
 907
 908                   temp_save.ExtensionBlocks = NULL;
 909                   temp_save.ExtensionBlockCount = 0;
 910
 911                   /* FIXME: The following is wrong.  It is left in only for
 912                    * backwards compatibility.  Someday it should go away. Use
 913                    * the sp->ExtensionBlocks->Function variable instead. */
 914                   sp->Extensions.Function = sp->Extensions.ExtensionBlocks[0].Function;
 915               }
 916               break;
 917
 918           case EXTENSION_RECORD_TYPE:
 919           {
 920               int Function;
 921               Extensions *Extensions;
 922
 923               if (DGifGetExtension(GifFile, &Function, &ExtData) == GIF_ERROR)
 924                   return (GIF_ERROR);
 925
 926               if (GifFile->ImageCount || Function == GRAPHICS_EXT_FUNC_CODE)
 927                   Extensions = &temp_save;
 928               else
 929                   Extensions = &GifFile->Extensions;
 930
 931               Extensions->Function = Function;
 932
 933               /* Create an extension block with our data */
 934               if (AddExtensionBlock(Extensions, ExtData[0], &ExtData[1]) == GIF_ERROR)
 935                   return (GIF_ERROR);
 936
 937               while (ExtData != NULL) {
 938                   int Len;
 939                   GifByteType *Data;
 940
 941                   if (DGifGetExtensionNext(GifFile, &ExtData) == GIF_ERROR)
 942                       return (GIF_ERROR);
 943
 944                   if (ExtData)
 945                   {
 946                       Len = ExtData[0];
 947                       Data = &ExtData[1];
 948                   }
 949                   else
 950                   {
 951                       Len = 0;
 952                       Data = NULL;
 953                   }
 954
 955                   if (AppendExtensionBlock(Extensions, Len, Data) == GIF_ERROR)
 956                       return (GIF_ERROR);
 957               }
 958               break;
 959           }
 960
 961           case TERMINATE_RECORD_TYPE:
 962               break;
 963
 964           default:    /* Should be trapped by DGifGetRecordType */
 965               break;
 966         }
 967     } while (RecordType != TERMINATE_RECORD_TYPE);
 968
 969     /* Just in case the Gif has an extension block without an associated
 970      * image... (Should we save this into a savefile structure with no image
 971      * instead? Have to check if the present writing code can handle that as
 972      * well.... */
 973     if (temp_save.ExtensionBlocks)
 974         FreeExtension(&temp_save);
 975
 976     return (GIF_OK);
 977 }
 978
 979 /******************************************************************************
 980  * GifFileType constructor with user supplied input function (TVT)
 981  *****************************************************************************/
 982 GifFileType *
 983 DGifOpen(void *userData,
 984          InputFunc readFunc) {
 985
 986     unsigned char Buf[GIF_STAMP_LEN + 1];
 987     GifFileType *GifFile;
 988     GifFilePrivateType *Private;
 989
 990     GifFile = ungif_alloc(sizeof(GifFileType));
 991     if (GifFile == NULL) {
 992         return NULL;
 993     }
 994
 995     memset(GifFile, '\0', sizeof(GifFileType));
 996
 997     Private = ungif_alloc(sizeof(GifFilePrivateType));
 998     if (!Private) {
 999         ungif_free(GifFile);
1000         return NULL;
1001     }
1002
1003     GifFile->Private = (void*)Private;
1004
1005     Private->Read = readFunc;    /* TVT */
1006     GifFile->UserData = userData;    /* TVT */
1007
1008     /* Lets see if this is a GIF file: */
1009     if (READ(GifFile, Buf, GIF_STAMP_LEN) != GIF_STAMP_LEN) {
1010         ungif_free(Private);
1011         ungif_free(GifFile);
1012         return NULL;
1013     }
1014
1015     /* The GIF Version number is ignored at this time. Maybe we should do
1016      * something more useful with it. */
1017     Buf[GIF_STAMP_LEN] = 0;
1018     if (memcmp(GIF_STAMP, Buf, GIF_VERSION_POS) != 0) {
1019         ungif_free(Private);
1020         ungif_free(GifFile);
1021         return NULL;
1022     }
1023
1024     if (DGifGetScreenDesc(GifFile) == GIF_ERROR) {
1025         ungif_free(Private);
1026         ungif_free(GifFile);
1027         return NULL;
1028     }
1029
1030     return GifFile;
1031 }
1032
1033 /******************************************************************************
1034  * This routine should be called last, to close the GIF file.
1035  *****************************************************************************/
1036 int
1037 DGifCloseFile(GifFileType * GifFile) {
1038
1039     GifFilePrivateType *Private;
1040
1041     if (GifFile == NULL)
1042         return GIF_ERROR;
1043
1044     Private = GifFile->Private;
1045
1046     if (GifFile->Image.ColorMap) {
1047         FreeMapObject(GifFile->Image.ColorMap);
1048         GifFile->Image.ColorMap = NULL;
1049     }
1050
1051     if (GifFile->SColorMap) {
1052         FreeMapObject(GifFile->SColorMap);
1053         GifFile->SColorMap = NULL;
1054     }
1055
1056     ungif_free(Private);
1057     Private = NULL;
1058
1059     if (GifFile->SavedImages) {
1060         FreeSavedImages(GifFile);
1061         GifFile->SavedImages = NULL;
1062     }
1063
1064     FreeExtension(&GifFile->Extensions);
1065
1066     ungif_free(GifFile);
1067
1068     return GIF_OK;
1069 }