dlls/windowscodecs/ungif.c

   1 /*
   2  * Gif extracting routines - derived from libungif
   3  *
   4  * Portions Copyright 2006 Mike McCormack
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  19  */
  20
  21 /*
  22  * Original copyright notice:
  23  *
  24  * The GIFLIB distribution is Copyright (c) 1997  Eric S. Raymond
  25  *
  26  * Permission is hereby granted, free of charge, to any person obtaining a copy
  27  * of this software and associated documentation files (the "Software"), to deal
  28  * in the Software without restriction, including without limitation the rights
  29  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  30  * copies of the Software, and to permit persons to whom the Software is
  31  * furnished to do so, subject to the following conditions:
  32  *
  33  * The above copyright notice and this permission notice shall be included in
  34  * all copies or substantial portions of the Software.
  35  */
  36
  37
  38 /******************************************************************************
  39  *   "Gif-Lib" - Yet another gif library.
  40  *
  41  * Written by:  Gershon Elber            IBM PC Ver 1.1,    Aug. 1990
  42  ******************************************************************************
  43  * The kernel of the GIF Decoding process can be found here.
  44  ******************************************************************************
  45  * History:
  46  * 16 Jun 89 - Version 1.0 by Gershon Elber.
  47  *  3 Sep 90 - Version 1.1 by Gershon Elber (Support for Gif89, Unique names).
  48  *****************************************************************************/
  49
  50 #include <stdlib.h>
  51 #include <string.h>
  52
  53 #include <stdarg.h>
  54 #include "windef.h"
  55 #include "winbase.h"
  56 #include "ungif.h"
  57 #include "wine/debug.h"
  58
  59 WINE_DEFAULT_DEBUG_CHANNEL(wincodecs);
  60
  61 static void *ungif_alloc( size_t sz )
  62 {
  63     return HeapAlloc( GetProcessHeap(), 0, sz );
  64 }
  65
  66 static void *ungif_calloc( size_t num, size_t sz )
  67 {
  68     return HeapAlloc( GetProcessHeap(), HEAP_ZERO_MEMORY, num*sz );
  69 }
  70
  71 static void *ungif_realloc( void *ptr, size_t sz )
  72 {
  73     return HeapReAlloc( GetProcessHeap(), 0, ptr, sz );
  74 }
  75
  76 static void ungif_free( void *ptr )
  77 {
  78     HeapFree( GetProcessHeap(), 0, ptr );
  79 }
  80
  81 #define LZ_MAX_CODE         4095    /* Biggest code possible in 12 bits. */
  82 #define LZ_BITS             12
  83
  84 #define NO_SUCH_CODE        4098    /* Impossible code, to signal empty. */
  85
  86 typedef struct GifFilePrivateType {
  87     GifWord BitsPerPixel,     /* Bits per pixel (Codes uses at least this + 1). */
  88       ClearCode,   /* The CLEAR LZ code. */
  89       EOFCode,     /* The EOF LZ code. */
  90       RunningCode, /* The next code algorithm can generate. */
  91       RunningBits, /* The number of bits required to represent RunningCode. */
  92       MaxCode1,    /* 1 bigger than max. possible code, in RunningBits bits. */
  93       LastCode,    /* The code before the current code. */
  94       CrntCode,    /* Current algorithm code. */
  95       StackPtr,    /* For character stack (see below). */
  96       CrntShiftState;    /* Number of bits in CrntShiftDWord. */
  97     unsigned long CrntShiftDWord;   /* For bytes decomposition into codes. */
  98     unsigned long PixelCount;   /* Number of pixels in image. */
  99     InputFunc Read;     /* function to read gif input (TVT) */
 100     GifByteType Buf[256];   /* Compressed input is buffered here. */
 101     GifByteType Stack[LZ_MAX_CODE]; /* Decoded pixels are stacked here. */
 102     GifByteType Suffix[LZ_MAX_CODE + 1];    /* So we can trace the codes. */
 103     GifPrefixType Prefix[LZ_MAX_CODE + 1];
 104 } GifFilePrivateType;
 105
 106 /* avoid extra function call in case we use fread (TVT) */
 107 #define READ(_gif,_buf,_len) \
 108     ((GifFilePrivateType*)_gif->Private)->Read(_gif,_buf,_len)
 109
 110 static int DGifGetWord(GifFileType *GifFile, GifWord *Word);
 111 static int DGifSetupDecompress(GifFileType *GifFile);
 112 static int DGifDecompressLine(GifFileType *GifFile, GifPixelType *Line, int LineLen);
 113 static int DGifGetPrefixChar(const GifPrefixType *Prefix, int Code, int ClearCode);
 114 static int DGifDecompressInput(GifFileType *GifFile, int *Code);
 115 static int DGifBufferedInput(GifFileType *GifFile, GifByteType *Buf,
 116                              GifByteType *NextByte);
 117
 118 static int DGifGetExtensionNext(GifFileType * GifFile, GifByteType ** GifExtension);
 119 static int DGifGetCodeNext(GifFileType * GifFile, GifByteType ** GifCodeBlock);
 120
 121 /******************************************************************************
 122  * Miscellaneous utility functions
 123  *****************************************************************************/
 124
 125 /* return smallest bitfield size n will fit in */
 126 static int
 127 BitSize(int n) {
 128
 129     register int i;
 130
 131     for (i = 1; i <= 8; i++)
 132         if ((1 << i) >= n)
 133             break;
 134     return (i);
 135 }
 136
 137 /******************************************************************************
 138  * Color map object functions
 139  *****************************************************************************/
 140
 141 /*
 142  * Allocate a color map of given size; initialize with contents of
 143  * ColorMap if that pointer is non-NULL.
 144  */
 145 static ColorMapObject *
 146 MakeMapObject(int ColorCount,
 147               const GifColorType * ColorMap) {
 148
 149     ColorMapObject *Object;
 150
 151     /*** FIXME: Our ColorCount has to be a power of two.  Is it necessary to
 152      * make the user know that or should we automatically round up instead? */
 153     if (ColorCount != (1 << BitSize(ColorCount))) {
 154         return NULL;
 155     }
 156
 157     Object = ungif_alloc(sizeof(ColorMapObject));
 158     if (Object == NULL) {
 159         return NULL;
 160     }
 161
 162     Object->Colors = ungif_calloc(ColorCount, sizeof(GifColorType));
 163     if (Object->Colors == NULL) {
 164         ungif_free(Object);
 165         return NULL;
 166     }
 167
 168     Object->ColorCount = ColorCount;
 169     Object->BitsPerPixel = BitSize(ColorCount);
 170
 171     if (ColorMap) {
 172         memcpy(Object->Colors, ColorMap, ColorCount * sizeof(GifColorType));
 173     }
 174
 175     return (Object);
 176 }
 177
 178 /*
 179  * Free a color map object
 180  */
 181 static void
 182 FreeMapObject(ColorMapObject * Object) {
 183
 184     if (Object != NULL) {
 185         ungif_free(Object->Colors);
 186         ungif_free(Object);
 187         /*** FIXME:
 188          * When we are willing to break API we need to make this function
 189          * FreeMapObject(ColorMapObject **Object)
 190          * and do this assignment to NULL here:
 191          * *Object = NULL;
 192          */
 193     }
 194 }
 195
 196 static int
 197 AddExtensionBlock(Extensions *New,
 198                   int Len,
 199                   const unsigned char ExtData[]) {
 200
 201     ExtensionBlock *ep;
 202
 203     if (New->ExtensionBlocks == NULL)
 204         New->ExtensionBlocks = ungif_alloc(sizeof(ExtensionBlock));
 205     else
 206         New->ExtensionBlocks = ungif_realloc(New->ExtensionBlocks,
 207                                       sizeof(ExtensionBlock) *
 208                                       (New->ExtensionBlockCount + 1));
 209
 210     if (New->ExtensionBlocks == NULL)
 211         return (GIF_ERROR);
 212
 213     ep = &New->ExtensionBlocks[New->ExtensionBlockCount++];
 214
 215     ep->ByteCount=Len + 3;
 216     ep->Bytes = ungif_alloc(ep->ByteCount + 3);
 217     if (ep->Bytes == NULL)
 218         return (GIF_ERROR);
 219
 220     /* Extension Header */
 221     ep->Bytes[0] = 0x21;
 222     ep->Bytes[1] = New->Function;
 223     ep->Bytes[2] = Len;
 224
 225     if (ExtData) {
 226         memcpy(ep->Bytes + 3, ExtData, Len);
 227         ep->Function = New->Function;
 228     }
 229
 230     return (GIF_OK);
 231 }
 232
 233 static int
 234 AppendExtensionBlock(Extensions *New,
 235                      int Len,
 236                      const unsigned char ExtData[])
 237 {
 238     ExtensionBlock *ep;
 239
 240     if (New->ExtensionBlocks == NULL)
 241         return (GIF_ERROR);
 242
 243     ep = &New->ExtensionBlocks[New->ExtensionBlockCount - 1];
 244
 245     ep->Bytes = ungif_realloc(ep->Bytes, ep->ByteCount + Len + 1);
 246     if (ep->Bytes == NULL)
 247         return (GIF_ERROR);
 248
 249     ep->Bytes[ep->ByteCount] = Len;
 250
 251     if (ExtData)
 252         memcpy(ep->Bytes + ep->ByteCount + 1, ExtData, Len);
 253
 254     ep->ByteCount += Len + 1;
 255
 256     return (GIF_OK);
 257 }
 258
 259 static void
 260 FreeExtension(Extensions *Extensions)
 261 {
 262     ExtensionBlock *ep;
 263
 264     if ((Extensions == NULL) || (Extensions->ExtensionBlocks == NULL)) {
 265         return;
 266     }
 267     for (ep = Extensions->ExtensionBlocks;
 268          ep < (Extensions->ExtensionBlocks + Extensions->ExtensionBlockCount); ep++)
 269         ungif_free(ep->Bytes);
 270     ungif_free(Extensions->ExtensionBlocks);
 271     Extensions->ExtensionBlocks = NULL;
 272 }
 273
 274 /******************************************************************************
 275  * Image block allocation functions
 276 ******************************************************************************/
 277
 278 static void
 279 FreeSavedImages(GifFileType * GifFile) {
 280
 281     SavedImage *sp;
 282
 283     if ((GifFile == NULL) || (GifFile->SavedImages == NULL)) {
 284         return;
 285     }
 286     for (sp = GifFile->SavedImages;
 287          sp < GifFile->SavedImages + GifFile->ImageCount; sp++) {
 288         if (sp->ImageDesc.ColorMap) {
 289             FreeMapObject(sp->ImageDesc.ColorMap);
 290             sp->ImageDesc.ColorMap = NULL;
 291         }
 292
 293         ungif_free(sp->RasterBits);
 294
 295         if (sp->Extensions.ExtensionBlocks)
 296             FreeExtension(&sp->Extensions);
 297     }
 298     ungif_free(GifFile->SavedImages);
 299     GifFile->SavedImages=NULL;
 300 }
 301
 302 /******************************************************************************
 303  * This routine should be called before any other DGif calls. Note that
 304  * this routine is called automatically from DGif file open routines.
 305  *****************************************************************************/
 306 static int
 307 DGifGetScreenDesc(GifFileType * GifFile) {
 308
 309     int i, BitsPerPixel, SortFlag;
 310     GifByteType Buf[3];
 311
 312     /* Put the screen descriptor into the file: */
 313     if (DGifGetWord(GifFile, &GifFile->SWidth) == GIF_ERROR ||
 314         DGifGetWord(GifFile, &GifFile->SHeight) == GIF_ERROR)
 315         return GIF_ERROR;
 316
 317     if (READ(GifFile, Buf, 3) != 3) {
 318         return GIF_ERROR;
 319     }
 320     GifFile->SColorResolution = (((Buf[0] & 0x70) + 1) >> 4) + 1;
 321     SortFlag = (Buf[0] & 0x08) != 0;
 322     BitsPerPixel = (Buf[0] & 0x07) + 1;
 323     GifFile->SBackGroundColor = Buf[1];
 324     GifFile->SAspectRatio = Buf[2];
 325     if (Buf[0] & 0x80) {    /* Do we have global color map? */
 326
 327         GifFile->SColorMap = MakeMapObject(1 << BitsPerPixel, NULL);
 328         if (GifFile->SColorMap == NULL) {
 329             return GIF_ERROR;
 330         }
 331
 332         /* Get the global color map: */
 333         GifFile->SColorMap->SortFlag = SortFlag;
 334         for (i = 0; i < GifFile->SColorMap->ColorCount; i++) {
 335             if (READ(GifFile, Buf, 3) != 3) {
 336                 FreeMapObject(GifFile->SColorMap);
 337                 GifFile->SColorMap = NULL;
 338                 return GIF_ERROR;
 339             }
 340             GifFile->SColorMap->Colors[i].Red = Buf[0];
 341             GifFile->SColorMap->Colors[i].Green = Buf[1];
 342             GifFile->SColorMap->Colors[i].Blue = Buf[2];
 343         }
 344     } else {
 345         GifFile->SColorMap = NULL;
 346     }
 347
 348     return GIF_OK;
 349 }
 350
 351 /******************************************************************************
 352  * This routine should be called before any attempt to read an image.
 353  *****************************************************************************/
 354 static int
 355 DGifGetRecordType(GifFileType * GifFile,
 356                   GifRecordType * Type) {
 357
 358     GifByteType Buf;
 359
 360     if (READ(GifFile, &Buf, 1) != 1) {
 361         /* Wine-specific behavior: Native accepts broken GIF files that have no
 362          * terminator, so we match this by treating EOF as a terminator. */
 363         *Type = TERMINATE_RECORD_TYPE;
 364         return GIF_OK;
 365     }
 366
 367     switch (Buf) {
 368       case ',':
 369           *Type = IMAGE_DESC_RECORD_TYPE;
 370           break;
 371       case '!':
 372           *Type = EXTENSION_RECORD_TYPE;
 373           break;
 374       case ';':
 375           *Type = TERMINATE_RECORD_TYPE;
 376           break;
 377       default:
 378           *Type = UNDEFINED_RECORD_TYPE;
 379           return GIF_ERROR;
 380     }
 381
 382     return GIF_OK;
 383 }
 384
 385 /******************************************************************************
 386  * This routine should be called before any attempt to read an image.
 387  * Note it is assumed the Image desc. header (',') has been read.
 388  *****************************************************************************/
 389 static int
 390 DGifGetImageDesc(GifFileType * GifFile) {
 391
 392     int i, BitsPerPixel, SortFlag;
 393     GifByteType Buf[3];
 394     GifFilePrivateType *Private = GifFile->Private;
 395     SavedImage *sp;
 396
 397     if (DGifGetWord(GifFile, &GifFile->Image.Left) == GIF_ERROR ||
 398         DGifGetWord(GifFile, &GifFile->Image.Top) == GIF_ERROR ||
 399         DGifGetWord(GifFile, &GifFile->Image.Width) == GIF_ERROR ||
 400         DGifGetWord(GifFile, &GifFile->Image.Height) == GIF_ERROR)
 401         return GIF_ERROR;
 402     if (READ(GifFile, Buf, 1) != 1) {
 403         return GIF_ERROR;
 404     }
 405     BitsPerPixel = (Buf[0] & 0x07) + 1;
 406     SortFlag = (Buf[0] & 0x20) != 0;
 407     GifFile->Image.Interlace = (Buf[0] & 0x40);
 408     if (Buf[0] & 0x80) {    /* Does this image have local color map? */
 409
 410         FreeMapObject(GifFile->Image.ColorMap);
 411
 412         GifFile->Image.ColorMap = MakeMapObject(1 << BitsPerPixel, NULL);
 413         if (GifFile->Image.ColorMap == NULL) {
 414             return GIF_ERROR;
 415         }
 416
 417         /* Get the image local color map: */
 418         GifFile->Image.ColorMap->SortFlag = SortFlag;
 419         for (i = 0; i < GifFile->Image.ColorMap->ColorCount; i++) {
 420             if (READ(GifFile, Buf, 3) != 3) {
 421                 FreeMapObject(GifFile->Image.ColorMap);
 422                 GifFile->Image.ColorMap = NULL;
 423                 return GIF_ERROR;
 424             }
 425             GifFile->Image.ColorMap->Colors[i].Red = Buf[0];
 426             GifFile->Image.ColorMap->Colors[i].Green = Buf[1];
 427             GifFile->Image.ColorMap->Colors[i].Blue = Buf[2];
 428         }
 429     } else if (GifFile->Image.ColorMap) {
 430         FreeMapObject(GifFile->Image.ColorMap);
 431         GifFile->Image.ColorMap = NULL;
 432     }
 433
 434     if (GifFile->SavedImages) {
 435         if ((GifFile->SavedImages = ungif_realloc(GifFile->SavedImages,
 436                                       sizeof(SavedImage) *
 437                                       (GifFile->ImageCount + 1))) == NULL) {
 438             return GIF_ERROR;
 439         }
 440     } else {
 441         if ((GifFile->SavedImages = ungif_alloc(sizeof(SavedImage))) == NULL) {
 442             return GIF_ERROR;
 443         }
 444     }
 445
 446     sp = &GifFile->SavedImages[GifFile->ImageCount];
 447     sp->ImageDesc = GifFile->Image;
 448     if (GifFile->Image.ColorMap != NULL) {
 449         sp->ImageDesc.ColorMap = MakeMapObject(
 450                                  GifFile->Image.ColorMap->ColorCount,
 451                                  GifFile->Image.ColorMap->Colors);
 452         if (sp->ImageDesc.ColorMap == NULL) {
 453             return GIF_ERROR;
 454         }
 455         sp->ImageDesc.ColorMap->SortFlag = GifFile->Image.ColorMap->SortFlag;
 456     }
 457     sp->RasterBits = NULL;
 458     sp->Extensions.ExtensionBlockCount = 0;
 459     sp->Extensions.ExtensionBlocks = NULL;
 460
 461     GifFile->ImageCount++;
 462
 463     Private->PixelCount = (long)GifFile->Image.Width *
 464        (long)GifFile->Image.Height;
 465
 466     DGifSetupDecompress(GifFile);  /* Reset decompress algorithm parameters. */
 467
 468     return GIF_OK;
 469 }
 470
 471 /******************************************************************************
 472  * Get one full scanned line (Line) of length LineLen from GIF file.
 473  *****************************************************************************/
 474 static int
 475 DGifGetLine(GifFileType * GifFile,
 476             GifPixelType * Line,
 477             int LineLen) {
 478
 479     GifByteType *Dummy;
 480     GifFilePrivateType *Private = GifFile->Private;
 481
 482     if (!LineLen)
 483         LineLen = GifFile->Image.Width;
 484
 485     if ((Private->PixelCount -= LineLen) > 0xffff0000UL) {
 486         return GIF_ERROR;
 487     }
 488
 489     if (DGifDecompressLine(GifFile, Line, LineLen) == GIF_OK) {
 490         if (Private->PixelCount == 0) {
 491             /* We probably would not be called any more, so lets clean
 492              * everything before we return: need to flush out all rest of
 493              * image until empty block (size 0) detected. We use GetCodeNext. */
 494             do
 495                 if (DGifGetCodeNext(GifFile, &Dummy) == GIF_ERROR)
 496                 {
 497                     WARN("GIF is not properly terminated\n");
 498                     break;
 499                 }
 500             while (Dummy != NULL) ;
 501         }
 502         return GIF_OK;
 503     } else
 504         return GIF_ERROR;
 505 }
 506
 507 /******************************************************************************
 508  * Get an extension block (see GIF manual) from gif file. This routine only
 509  * returns the first data block, and DGifGetExtensionNext should be called
 510  * after this one until NULL extension is returned.
 511  * The Extension should NOT be freed by the user (not dynamically allocated).
 512  * Note it is assumed the Extension desc. header ('!') has been read.
 513  *****************************************************************************/
 514 static int
 515 DGifGetExtension(GifFileType * GifFile,
 516                  int *ExtCode,
 517                  GifByteType ** Extension) {
 518
 519     GifByteType Buf;
 520
 521     if (READ(GifFile, &Buf, 1) != 1) {
 522         return GIF_ERROR;
 523     }
 524     *ExtCode = Buf;
 525
 526     return DGifGetExtensionNext(GifFile, Extension);
 527 }
 528
 529 /******************************************************************************
 530  * Get a following extension block (see GIF manual) from gif file. This
 531  * routine should be called until NULL Extension is returned.
 532  * The Extension should NOT be freed by the user (not dynamically allocated).
 533  *****************************************************************************/
 534 static int
 535 DGifGetExtensionNext(GifFileType * GifFile,
 536                      GifByteType ** Extension) {
 537
 538     GifByteType Buf;
 539     GifFilePrivateType *Private = GifFile->Private;
 540
 541     if (READ(GifFile, &Buf, 1) != 1) {
 542         return GIF_ERROR;
 543     }
 544     if (Buf > 0) {
 545         *Extension = Private->Buf;    /* Use private unused buffer. */
 546         (*Extension)[0] = Buf;  /* Pascal strings notation (pos. 0 is len.). */
 547         if (READ(GifFile, &((*Extension)[1]), Buf) != Buf) {
 548             return GIF_ERROR;
 549         }
 550     } else
 551         *Extension = NULL;
 552
 553     return GIF_OK;
 554 }
 555
 556 /******************************************************************************
 557  * Get 2 bytes (word) from the given file:
 558  *****************************************************************************/
 559 static int
 560 DGifGetWord(GifFileType * GifFile,
 561             GifWord *Word) {
 562
 563     unsigned char c[2];
 564
 565     if (READ(GifFile, c, 2) != 2) {
 566         return GIF_ERROR;
 567     }
 568
 569     *Word = (((unsigned int)c[1]) << 8) + c[0];
 570     return GIF_OK;
 571 }
 572
 573 /******************************************************************************
 574  * Continue to get the image code in compressed form. This routine should be
 575  * called until NULL block is returned.
 576  * The block should NOT be freed by the user (not dynamically allocated).
 577  *****************************************************************************/
 578 static int
 579 DGifGetCodeNext(GifFileType * GifFile,
 580                 GifByteType ** CodeBlock) {
 581
 582     GifByteType Buf;
 583     GifFilePrivateType *Private = GifFile->Private;
 584
 585     if (READ(GifFile, &Buf, 1) != 1) {
 586         return GIF_ERROR;
 587     }
 588
 589     if (Buf > 0) {
 590         *CodeBlock = Private->Buf;    /* Use private unused buffer. */
 591         (*CodeBlock)[0] = Buf;  /* Pascal strings notation (pos. 0 is len.). */
 592         if (READ(GifFile, &((*CodeBlock)[1]), Buf) != Buf) {
 593             return GIF_ERROR;
 594         }
 595     } else {
 596         *CodeBlock = NULL;
 597         Private->Buf[0] = 0;    /* Make sure the buffer is empty! */
 598         Private->PixelCount = 0;    /* And local info. indicate image read. */
 599     }
 600
 601     return GIF_OK;
 602 }
 603
 604 /******************************************************************************
 605  * Setup the LZ decompression for this image:
 606  *****************************************************************************/
 607 static int
 608 DGifSetupDecompress(GifFileType * GifFile) {
 609
 610     int i, BitsPerPixel;
 611     GifByteType CodeSize;
 612     GifPrefixType *Prefix;
 613     GifFilePrivateType *Private = GifFile->Private;
 614
 615     READ(GifFile, &CodeSize, 1);    /* Read Code size from file. */
 616     BitsPerPixel = CodeSize;
 617
 618     Private->Buf[0] = 0;    /* Input Buffer empty. */
 619     Private->BitsPerPixel = BitsPerPixel;
 620     Private->ClearCode = (1 << BitsPerPixel);
 621     Private->EOFCode = Private->ClearCode + 1;
 622     Private->RunningCode = Private->EOFCode + 1;
 623     Private->RunningBits = BitsPerPixel + 1;    /* Number of bits per code. */
 624     Private->MaxCode1 = 1 << Private->RunningBits;    /* Max. code + 1. */
 625     Private->StackPtr = 0;    /* No pixels on the pixel stack. */
 626     Private->LastCode = NO_SUCH_CODE;
 627     Private->CrntShiftState = 0;    /* No information in CrntShiftDWord. */
 628     Private->CrntShiftDWord = 0;
 629
 630     Prefix = Private->Prefix;
 631     for (i = 0; i <= LZ_MAX_CODE; i++)
 632         Prefix[i] = NO_SUCH_CODE;
 633
 634     return GIF_OK;
 635 }
 636
 637 /******************************************************************************
 638  * The LZ decompression routine:
 639  * This version decompress the given gif file into Line of length LineLen.
 640  * This routine can be called few times (one per scan line, for example), in
 641  * order the complete the whole image.
 642  *****************************************************************************/
 643 static int
 644 DGifDecompressLine(GifFileType * GifFile,
 645                    GifPixelType * Line,
 646                    int LineLen) {
 647
 648     int i = 0;
 649     int j, CrntCode, EOFCode, ClearCode, CrntPrefix, LastCode, StackPtr;
 650     GifByteType *Stack, *Suffix;
 651     GifPrefixType *Prefix;
 652     GifFilePrivateType *Private = GifFile->Private;
 653
 654     StackPtr = Private->StackPtr;
 655     Prefix = Private->Prefix;
 656     Suffix = Private->Suffix;
 657     Stack = Private->Stack;
 658     EOFCode = Private->EOFCode;
 659     ClearCode = Private->ClearCode;
 660     LastCode = Private->LastCode;
 661
 662     if (StackPtr != 0) {
 663         /* Let pop the stack off before continuing to read the gif file: */
 664         while (StackPtr != 0 && i < LineLen)
 665             Line[i++] = Stack[--StackPtr];
 666     }
 667
 668     while (i < LineLen) {    /* Decode LineLen items. */
 669         if (DGifDecompressInput(GifFile, &CrntCode) == GIF_ERROR)
 670             return GIF_ERROR;
 671
 672         if (CrntCode == EOFCode) {
 673             /* Note, however, that usually we will not be here as we will stop
 674              * decoding as soon as we got all the pixel, or EOF code will
 675              * not be read at all, and DGifGetLine/Pixel clean everything.  */
 676             if (i != LineLen - 1 || Private->PixelCount != 0) {
 677                 return GIF_ERROR;
 678             }
 679             i++;
 680         } else if (CrntCode == ClearCode) {
 681             /* We need to start over again: */
 682             for (j = 0; j <= LZ_MAX_CODE; j++)
 683                 Prefix[j] = NO_SUCH_CODE;
 684             Private->RunningCode = Private->EOFCode + 1;
 685             Private->RunningBits = Private->BitsPerPixel + 1;
 686             Private->MaxCode1 = 1 << Private->RunningBits;
 687             LastCode = Private->LastCode = NO_SUCH_CODE;
 688         } else {
 689             /* It's a regular code - if in pixel range simply add it to output
 690              * stream, otherwise trace to codes linked list until the prefix
 691              * is in pixel range: */
 692             if (CrntCode < ClearCode) {
 693                 /* This is simple - its pixel scalar, so add it to output: */
 694                 Line[i++] = CrntCode;
 695             } else {
 696                 /* It's a code to be traced: trace the linked list
 697                  * until the prefix is a pixel, while pushing the suffix
 698                  * pixels on our stack. If we done, pop the stack in reverse
 699                  * order (that's what stack is good for!) for output.  */
 700                 if (Prefix[CrntCode] == NO_SUCH_CODE) {
 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                     if (CrntCode == Private->RunningCode - 2) {
 706                         CrntPrefix = LastCode;
 707                         Suffix[Private->RunningCode - 2] =
 708                            Stack[StackPtr++] = DGifGetPrefixChar(Prefix,
 709                                                                  LastCode,
 710                                                                  ClearCode);
 711                     } else {
 712                         return GIF_ERROR;
 713                     }
 714                 } else
 715                     CrntPrefix = CrntCode;
 716
 717                 /* Now (if image is O.K.) we should not get a NO_SUCH_CODE
 718                  * during the trace. As we might loop forever, in case of
 719                  * defective image, we count the number of loops we trace
 720                  * and stop if we got LZ_MAX_CODE. Obviously we cannot
 721                  * loop more than that.  */
 722                 j = 0;
 723                 while (j++ <= LZ_MAX_CODE &&
 724                        CrntPrefix > ClearCode && CrntPrefix <= LZ_MAX_CODE) {
 725                     Stack[StackPtr++] = Suffix[CrntPrefix];
 726                     CrntPrefix = Prefix[CrntPrefix];
 727                 }
 728                 if (j >= LZ_MAX_CODE || CrntPrefix > LZ_MAX_CODE) {
 729                     return GIF_ERROR;
 730                 }
 731                 /* Push the last character on stack: */
 732                 Stack[StackPtr++] = CrntPrefix;
 733
 734                 /* Now lets pop all the stack into output: */
 735                 while (StackPtr != 0 && i < LineLen)
 736                     Line[i++] = Stack[--StackPtr];
 737             }
 738             if (LastCode != NO_SUCH_CODE) {
 739                 Prefix[Private->RunningCode - 2] = LastCode;
 740
 741                 if (CrntCode == Private->RunningCode - 2) {
 742                     /* Only allowed if CrntCode is exactly the running code:
 743                      * In that case CrntCode = XXXCode, CrntCode or the
 744                      * prefix code is last code and the suffix char is
 745                      * exactly the prefix of last code! */
 746                     Suffix[Private->RunningCode - 2] =
 747                        DGifGetPrefixChar(Prefix, LastCode, ClearCode);
 748                 } else {
 749                     Suffix[Private->RunningCode - 2] =
 750                        DGifGetPrefixChar(Prefix, CrntCode, ClearCode);
 751                 }
 752             }
 753             LastCode = CrntCode;
 754         }
 755     }
 756
 757     Private->LastCode = LastCode;
 758     Private->StackPtr = StackPtr;
 759
 760     return GIF_OK;
 761 }
 762
 763 /******************************************************************************
 764  * Routine to trace the Prefixes linked list until we get a prefix which is
 765  * not code, but a pixel value (less than ClearCode). Returns that pixel value.
 766  * If image is defective, we might loop here forever, so we limit the loops to
 767  * the maximum possible if image O.k. - LZ_MAX_CODE times.
 768  *****************************************************************************/
 769 static int
 770 DGifGetPrefixChar(const GifPrefixType *Prefix,
 771                   int Code,
 772                   int ClearCode) {
 773
 774     int i = 0;
 775
 776     while (Code > ClearCode && i++ <= LZ_MAX_CODE)
 777         Code = Prefix[Code];
 778     return Code;
 779 }
 780
 781 /******************************************************************************
 782  * The LZ decompression input routine:
 783  * This routine is responsible for the decompression of the bit stream from
 784  * 8 bits (bytes) packets, into the real codes.
 785  * Returns GIF_OK if read successfully.
 786  *****************************************************************************/
 787 static int
 788 DGifDecompressInput(GifFileType * GifFile,
 789                     int *Code) {
 790
 791     GifFilePrivateType *Private = GifFile->Private;
 792
 793     GifByteType NextByte;
 794     static const unsigned short CodeMasks[] = {
 795         0x0000, 0x0001, 0x0003, 0x0007,
 796         0x000f, 0x001f, 0x003f, 0x007f,
 797         0x00ff, 0x01ff, 0x03ff, 0x07ff,
 798         0x0fff
 799     };
 800     /* The image can't contain more than LZ_BITS per code. */
 801     if (Private->RunningBits > LZ_BITS) {
 802         return GIF_ERROR;
 803     }
 804
 805     while (Private->CrntShiftState < Private->RunningBits) {
 806         /* Needs to get more bytes from input stream for next code: */
 807         if (DGifBufferedInput(GifFile, Private->Buf, &NextByte) == GIF_ERROR) {
 808             return GIF_ERROR;
 809         }
 810         Private->CrntShiftDWord |=
 811            ((unsigned long)NextByte) << Private->CrntShiftState;
 812         Private->CrntShiftState += 8;
 813     }
 814     *Code = Private->CrntShiftDWord & CodeMasks[Private->RunningBits];
 815
 816     Private->CrntShiftDWord >>= Private->RunningBits;
 817     Private->CrntShiftState -= Private->RunningBits;
 818
 819     /* If code cannot fit into RunningBits bits, must raise its size. Note
 820      * however that codes above 4095 are used for special signaling.
 821      * If we're using LZ_BITS bits already and we're at the max code, just
 822      * keep using the table as it is, don't increment Private->RunningCode.
 823      */
 824     if (Private->RunningCode < LZ_MAX_CODE + 2 &&
 825             ++Private->RunningCode > Private->MaxCode1 &&
 826             Private->RunningBits < LZ_BITS) {
 827         Private->MaxCode1 <<= 1;
 828         Private->RunningBits++;
 829     }
 830     return GIF_OK;
 831 }
 832
 833 /******************************************************************************
 834  * This routines read one gif data block at a time and buffers it internally
 835  * so that the decompression routine could access it.
 836  * The routine returns the next byte from its internal buffer (or read next
 837  * block in if buffer empty) and returns GIF_OK if successful.
 838  *****************************************************************************/
 839 static int
 840 DGifBufferedInput(GifFileType * GifFile,
 841                   GifByteType * Buf,
 842                   GifByteType * NextByte) {
 843
 844     if (Buf[0] == 0) {
 845         /* Needs to read the next buffer - this one is empty: */
 846         if (READ(GifFile, Buf, 1) != 1) {
 847             return GIF_ERROR;
 848         }
 849         /* There shouldn't be any empty data blocks here as the LZW spec
 850          * says the LZW termination code should come first.  Therefore we
 851          * shouldn't be inside this routine at that point.
 852          */
 853         if (Buf[0] == 0) {
 854             return GIF_ERROR;
 855         }
 856         if (READ(GifFile, &Buf[1], Buf[0]) != Buf[0]) {
 857             return GIF_ERROR;
 858         }
 859         *NextByte = Buf[1];
 860         Buf[1] = 2;    /* We use now the second place as last char read! */
 861         Buf[0]--;
 862     } else {
 863         *NextByte = Buf[Buf[1]++];
 864         Buf[0]--;
 865     }
 866
 867     return GIF_OK;
 868 }
 869
 870 /******************************************************************************
 871  * This routine reads an entire GIF into core, hanging all its state info off
 872  * the GifFileType pointer.  Call DGifOpenFileName() or DGifOpenFileHandle()
 873  * first to initialize I/O.  Its inverse is EGifSpew().
 874  ******************************************************************************/
 875 int
 876 DGifSlurp(GifFileType * GifFile) {
 877
 878     int ImageSize;
 879     GifRecordType RecordType;
 880     SavedImage *sp;
 881     GifByteType *ExtData;
 882     Extensions temp_save;
 883
 884     temp_save.ExtensionBlocks = NULL;
 885     temp_save.ExtensionBlockCount = 0;
 886
 887     do {
 888         if (DGifGetRecordType(GifFile, &RecordType) == GIF_ERROR)
 889             return (GIF_ERROR);
 890
 891         switch (RecordType) {
 892           case IMAGE_DESC_RECORD_TYPE:
 893               if (DGifGetImageDesc(GifFile) == GIF_ERROR)
 894                   return (GIF_ERROR);
 895
 896               sp = &GifFile->SavedImages[GifFile->ImageCount - 1];
 897               ImageSize = sp->ImageDesc.Width * sp->ImageDesc.Height;
 898
 899               sp->RasterBits = ungif_alloc(ImageSize * sizeof(GifPixelType));
 900               if (sp->RasterBits == NULL) {
 901                   return GIF_ERROR;
 902               }
 903               if (DGifGetLine(GifFile, sp->RasterBits, ImageSize) ==
 904                   GIF_ERROR)
 905                   return (GIF_ERROR);
 906               if (temp_save.ExtensionBlocks) {
 907                   sp->Extensions.ExtensionBlocks = temp_save.ExtensionBlocks;
 908                   sp->Extensions.ExtensionBlockCount = temp_save.ExtensionBlockCount;
 909
 910                   temp_save.ExtensionBlocks = NULL;
 911                   temp_save.ExtensionBlockCount = 0;
 912
 913                   /* FIXME: The following is wrong.  It is left in only for
 914                    * backwards compatibility.  Someday it should go away. Use
 915                    * the sp->ExtensionBlocks->Function variable instead. */
 916                   sp->Extensions.Function = sp->Extensions.ExtensionBlocks[0].Function;
 917               }
 918               break;
 919
 920           case EXTENSION_RECORD_TYPE:
 921           {
 922               int Function;
 923               Extensions *Extensions;
 924
 925               if (DGifGetExtension(GifFile, &Function, &ExtData) == GIF_ERROR)
 926                   return (GIF_ERROR);
 927
 928               if (GifFile->ImageCount || Function == GRAPHICS_EXT_FUNC_CODE)
 929                   Extensions = &temp_save;
 930               else
 931                   Extensions = &GifFile->Extensions;
 932
 933               Extensions->Function = Function;
 934
 935               if (ExtData)
 936               {
 937                   /* Create an extension block with our data */
 938                   if (AddExtensionBlock(Extensions, ExtData[0], &ExtData[1]) == GIF_ERROR)
 939                       return (GIF_ERROR);
 940               }
 941               else /* Empty extension block */
 942               {
 943                   if (AddExtensionBlock(Extensions, 0, NULL) == GIF_ERROR)
 944                       return (GIF_ERROR);
 945               }
 946
 947               while (ExtData != NULL) {
 948                   int Len;
 949                   GifByteType *Data;
 950
 951                   if (DGifGetExtensionNext(GifFile, &ExtData) == GIF_ERROR)
 952                       return (GIF_ERROR);
 953
 954                   if (ExtData)
 955                   {
 956                       Len = ExtData[0];
 957                       Data = &ExtData[1];
 958                   }
 959                   else
 960                   {
 961                       Len = 0;
 962                       Data = NULL;
 963                   }
 964
 965                   if (AppendExtensionBlock(Extensions, Len, Data) == GIF_ERROR)
 966                       return (GIF_ERROR);
 967               }
 968               break;
 969           }
 970
 971           case TERMINATE_RECORD_TYPE:
 972               break;
 973
 974           default:    /* Should be trapped by DGifGetRecordType */
 975               break;
 976         }
 977     } while (RecordType != TERMINATE_RECORD_TYPE);
 978
 979     /* Just in case the Gif has an extension block without an associated
 980      * image... (Should we save this into a savefile structure with no image
 981      * instead? Have to check if the present writing code can handle that as
 982      * well.... */
 983     if (temp_save.ExtensionBlocks)
 984         FreeExtension(&temp_save);
 985
 986     return (GIF_OK);
 987 }
 988
 989 /******************************************************************************
 990  * GifFileType constructor with user supplied input function (TVT)
 991  *****************************************************************************/
 992 GifFileType *
 993 DGifOpen(void *userData,
 994          InputFunc readFunc) {
 995
 996     unsigned char Buf[GIF_STAMP_LEN + 1];
 997     GifFileType *GifFile;
 998     GifFilePrivateType *Private;
 999
1000     GifFile = ungif_alloc(sizeof(GifFileType));
1001     if (GifFile == NULL) {
1002         return NULL;
1003     }
1004
1005     memset(GifFile, '\0', sizeof(GifFileType));
1006
1007     Private = ungif_alloc(sizeof(GifFilePrivateType));
1008     if (!Private) {
1009         ungif_free(GifFile);
1010         return NULL;
1011     }
1012
1013     GifFile->Private = (void*)Private;
1014
1015     Private->Read = readFunc;    /* TVT */
1016     GifFile->UserData = userData;    /* TVT */
1017
1018     /* Lets see if this is a GIF file: */
1019     if (READ(GifFile, Buf, GIF_STAMP_LEN) != GIF_STAMP_LEN) {
1020         ungif_free(Private);
1021         ungif_free(GifFile);
1022         return NULL;
1023     }
1024
1025     /* The GIF Version number is ignored at this time. Maybe we should do
1026      * something more useful with it. */
1027     Buf[GIF_STAMP_LEN] = 0;
1028     if (memcmp(GIF_STAMP, Buf, GIF_VERSION_POS) != 0) {
1029         ungif_free(Private);
1030         ungif_free(GifFile);
1031         return NULL;
1032     }
1033
1034     if (DGifGetScreenDesc(GifFile) == GIF_ERROR) {
1035         ungif_free(Private);
1036         ungif_free(GifFile);
1037         return NULL;
1038     }
1039
1040     return GifFile;
1041 }
1042
1043 /******************************************************************************
1044  * This routine should be called last, to close the GIF file.
1045  *****************************************************************************/
1046 int
1047 DGifCloseFile(GifFileType * GifFile) {
1048
1049     GifFilePrivateType *Private;
1050
1051     if (GifFile == NULL)
1052         return GIF_ERROR;
1053
1054     Private = GifFile->Private;
1055
1056     if (GifFile->Image.ColorMap) {
1057         FreeMapObject(GifFile->Image.ColorMap);
1058         GifFile->Image.ColorMap = NULL;
1059     }
1060
1061     if (GifFile->SColorMap) {
1062         FreeMapObject(GifFile->SColorMap);
1063         GifFile->SColorMap = NULL;
1064     }
1065
1066     ungif_free(Private);
1067     Private = NULL;
1068
1069     if (GifFile->SavedImages) {
1070         FreeSavedImages(GifFile);
1071         GifFile->SavedImages = NULL;
1072     }
1073
1074     FreeExtension(&GifFile->Extensions);
1075
1076     ungif_free(GifFile);
1077
1078     return GIF_OK;
1079 }