Logo Search packages:      
Sourcecode: giflib version File versions  Download package

dgif_lib.c

/******************************************************************************
*   "Gif-Lib" - Yet another gif library.                          *
*                                                           *
* Written by:  Gershon Elber              IBM PC Ver 1.1,   Aug. 1990     *
*******************************************************************************
* The kernel of the GIF Decoding process can be found here.             *
*******************************************************************************
* History:                                                  *
* 16 Jun 89 - Version 1.0 by Gershon Elber.                             *
*  3 Sep 90 - Version 1.1 by Gershon Elber (Support for Gif89, Unique names). *
******************************************************************************/


#ifdef __MSDOS__
#include <io.h>
#include <alloc.h>
#include <stdlib.h>
#include <sys\stat.h>
#else
#include <sys/types.h>
#include <sys/stat.h>
#endif /* __MSDOS__ */

#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include "gif_lib.h"
#include "gif_hash.h"

#define PROGRAM_NAME    "GIFLIB"

#define COMMENT_EXT_FUNC_CODE 0xfe /* Extension function code for comment. */
#define GIF_STAMP "GIFVER"     /* First chars in file - GIF stamp. */
#define GIF_STAMP_LEN   sizeof(GIF_STAMP) - 1
#define GIF_VERSION_POS 3           /* Version first character in stamp. */

#define LZ_MAX_CODE     4095        /* Biggest code possible in 12 bits. */
#define LZ_BITS         12

#define FILE_STATE_READ       0x01/* 1 write, 0 read - EGIF_LIB compatible.*/

#define FLUSH_OUTPUT          4096    /* Impossible code, to signal flush. */
#define FIRST_CODE            4097    /* Impossible code, to signal first. */
#define NO_SUCH_CODE          4098    /* Impossible code, to signal empty. */

#define IS_READABLE(Private)  (!(Private->FileState & FILE_STATE_READ))

typedef struct GifFilePrivateType {
    int FileState,
      FileHandle,                  /* Where all this data goes to! */
      BitsPerPixel,         /* Bits per pixel (Codes uses at list this + 1). */
      ClearCode,                           /* The CLEAR LZ code. */
      EOFCode,                               /* The EOF LZ code. */
      RunningCode,                /* The next code algorithm can generate. */
      RunningBits,/* The number of bits required to represent RunningCode. */
      MaxCode1,  /* 1 bigger than max. possible code, in RunningBits bits. */
      LastCode,                 /* The code before the current code. */
      CrntCode,                       /* Current algorithm code. */
      StackPtr,                  /* For character stack (see below). */
      CrntShiftState;                 /* Number of bits in CrntShiftDWord. */
    unsigned long CrntShiftDWord;     /* For bytes decomposition into codes. */
    unsigned long PixelCount;              /* Number of pixels in image. */
    FILE *File;                                   /* File as stream. */
    GifByteType Buf[256];            /* Compressed input is buffered here. */
    GifByteType Stack[LZ_MAX_CODE];  /* Decoded pixels are stacked here. */
    GifByteType Suffix[LZ_MAX_CODE+1];           /* So we can trace the codes. */
    unsigned int Prefix[LZ_MAX_CODE+1];
} GifFilePrivateType;

#ifdef SYSV
static char *VersionStr =
        "Gif library module,\t\tGershon Elber\n\
      (C) Copyright 1989 Gershon Elber, Non commercial use only.\n";
#else
static char *VersionStr =
      PROGRAM_NAME
      "     IBMPC "
      GIF_LIB_VERSION
      "     Gershon Elber,    "
      __DATE__ ",   " __TIME__ "\n"
      "(C) Copyright 1989 Gershon Elber, Non commercial use only.\n";
#endif /* SYSV */

extern int _GifError;

static int DGifGetWord(FILE *File, int *Word);
static int DGifSetupDecompress(GifFileType *GifFile);
static int DGifDecompressLine(GifFileType *GifFile, GifPixelType *Line,
                                                int LineLen);
static int DGifGetPrefixChar(unsigned int *Prefix, int Code, int ClearCode);
static int DGifDecompressInput(GifFilePrivateType *Private, int *Code);
static int DGifBufferedInput(FILE *File, GifByteType *Buf,
                                         GifByteType *NextByte);

/******************************************************************************
*   Open a new gif file for read, given by its name.                    *
*   Returns GifFileType pointer dynamically allocated which serves as the gif *
* info record. _GifError is cleared if succesfull.                      *
******************************************************************************/
GifFileType *DGifOpenFileName(const char *FileName)
{
    int FileHandle;

    if ((FileHandle = open(FileName, O_RDONLY
#ifdef __MSDOS__
                             | O_BINARY
#endif /* __MSDOS__ */
                                       )) == -1) {
      _GifError = D_GIF_ERR_OPEN_FAILED;
      return NULL;
    }

    return DGifOpenFileHandle(FileHandle);
}

/******************************************************************************
*   Update a new gif file, given its file handle.                       *
*   Returns GifFileType pointer dynamically allocated which serves as the gif *
* info record. _GifError is cleared if succesfull.                      *
******************************************************************************/
GifFileType *DGifOpenFileHandle(int FileHandle)
{
    char Buf[GIF_STAMP_LEN+1];
    GifFileType *GifFile;
    GifFilePrivateType *Private;
    FILE *f;

#ifdef __MSDOS__
    setmode(FileHandle, O_BINARY);    /* Make sure it is in binary mode. */
    f = fdopen(FileHandle, "rb");            /* Make it into a stream: */
    setvbuf(f, NULL, _IOFBF, GIF_FILE_BUFFER_SIZE);/* And inc. stream buffer.*/
#else
    f = fdopen(FileHandle, "r");             /* Make it into a stream: */
#endif /* __MSDOS__ */

    if ((GifFile = (GifFileType *) malloc(sizeof(GifFileType))) == NULL) {
      _GifError = D_GIF_ERR_NOT_ENOUGH_MEM;
      return NULL;
    }

    memset(GifFile, '\0', sizeof(GifFileType));

    if ((Private = (GifFilePrivateType *) malloc(sizeof(GifFilePrivateType)))
      == NULL) {
      _GifError = D_GIF_ERR_NOT_ENOUGH_MEM;
      free((char *) GifFile);
      return NULL;
    }
    GifFile->Private = (VoidPtr) Private;
    Private->FileHandle = FileHandle;
    Private->File = f;
    Private->FileState = 0;   /* Make sure bit 0 = 0 (File open for read). */

    /* Lets see if this is a GIF file: */
    if (fread(Buf, 1, GIF_STAMP_LEN, Private->File) != GIF_STAMP_LEN) {
      _GifError = D_GIF_ERR_READ_FAILED;
      free((char *) Private);
      free((char *) GifFile);
      return NULL;
    }

    /* The GIF Version number is ignored at this time. Maybe we should do    */
    /* something more useful with it.                                  */
    Buf[GIF_STAMP_LEN] = 0;
    if (strncmp(GIF_STAMP, Buf, GIF_VERSION_POS) != 0) {
      _GifError = D_GIF_ERR_NOT_GIF_FILE;
      free((char *) Private);
      free((char *) GifFile);
      return NULL;
    }

    if (DGifGetScreenDesc(GifFile) == GIF_ERROR) {
      free((char *) Private);
      free((char *) GifFile);
      return NULL;
    }

    _GifError = 0;

    return GifFile;
}

/******************************************************************************
*   This routine should be called before any other DGif calls. Note that      *
* this routine is called automatically from DGif file open routines.          *
******************************************************************************/
int DGifGetScreenDesc(GifFileType *GifFile)
{
    int i, BitsPerPixel;
    GifByteType Buf[3];
    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;

    if (!IS_READABLE(Private)) {
      /* This file was NOT open for reading: */
      _GifError = D_GIF_ERR_NOT_READABLE;
      return GIF_ERROR;
    }

    /* Put the screen descriptor into the file: */
    if (DGifGetWord(Private->File, &GifFile->SWidth) == GIF_ERROR ||
      DGifGetWord(Private->File, &GifFile->SHeight) == GIF_ERROR)
      return GIF_ERROR;

    if (fread(Buf, 1, 3, Private->File) != 3) {
      _GifError = D_GIF_ERR_READ_FAILED;
      return GIF_ERROR;
    }
    GifFile->SColorResolution = (((Buf[0] & 0x70) + 1) >> 4) + 1;
    BitsPerPixel = (Buf[0] & 0x07) + 1;
    GifFile->SBackGroundColor = Buf[1];
    if (Buf[0] & 0x80) {                 /* Do we have global color map? */

      GifFile->SColorMap = MakeMapObject(1 << BitsPerPixel, NULL);

      /* Get the global color map: */
      for (i = 0; i < GifFile->SColorMap->ColorCount; i++) {
          if (fread(Buf, 1, 3, Private->File) != 3) {
            _GifError = D_GIF_ERR_READ_FAILED;
            return GIF_ERROR;
          }
          GifFile->SColorMap->Colors[i].Red = Buf[0];
          GifFile->SColorMap->Colors[i].Green = Buf[1];
          GifFile->SColorMap->Colors[i].Blue = Buf[2];
      }
    }

    return GIF_OK;
}

/******************************************************************************
*   This routine should be called before any attemp to read an image.         *
******************************************************************************/
int DGifGetRecordType(GifFileType *GifFile, GifRecordType *Type)
{
    GifByteType Buf;
    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;

    if (!IS_READABLE(Private)) {
      /* This file was NOT open for reading: */
      _GifError = D_GIF_ERR_NOT_READABLE;
      return GIF_ERROR;
    }

    if (fread(&Buf, 1, 1, Private->File) != 1) {
      _GifError = D_GIF_ERR_READ_FAILED;
      return GIF_ERROR;
    }

    switch (Buf) {
      case ',':
          *Type = IMAGE_DESC_RECORD_TYPE;
          break;
      case '!':
          *Type = EXTENSION_RECORD_TYPE;
          break;
      case ';':
          *Type = TERMINATE_RECORD_TYPE;
          break;
      default:
          *Type = UNDEFINED_RECORD_TYPE;
          _GifError = D_GIF_ERR_WRONG_RECORD;
          return GIF_ERROR;
    }

    return GIF_OK;
}

/******************************************************************************
*   This routine should be called before any attemp to read an image.         *
*   Note it is assumed the Image desc. header (',') has been read.            *
******************************************************************************/
int DGifGetImageDesc(GifFileType *GifFile)
{
    int i, BitsPerPixel;
    GifByteType Buf[3];
    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;

    if (!IS_READABLE(Private)) {
      /* This file was NOT open for reading: */
      _GifError = D_GIF_ERR_NOT_READABLE;
      return GIF_ERROR;
    }

    if (DGifGetWord(Private->File, &GifFile->Image.Left) == GIF_ERROR ||
      DGifGetWord(Private->File, &GifFile->Image.Top) == GIF_ERROR ||
      DGifGetWord(Private->File, &GifFile->Image.Width) == GIF_ERROR ||
      DGifGetWord(Private->File, &GifFile->Image.Height) == GIF_ERROR)
      return GIF_ERROR;
    if (fread(Buf, 1, 1, Private->File) != 1) {
      _GifError = D_GIF_ERR_READ_FAILED;
      return GIF_ERROR;
    }
    BitsPerPixel = (Buf[0] & 0x07) + 1;
    GifFile->Image.Interlace = (Buf[0] & 0x40);
    if (Buf[0] & 0x80) {          /* Does this image have local color map? */

      if (GifFile->Image.ColorMap && GifFile->SavedImages == NULL)
          FreeMapObject(GifFile->Image.ColorMap);

      GifFile->Image.ColorMap = MakeMapObject(1 << BitsPerPixel, NULL);
    
      /* Get the image local color map: */
      for (i = 0; i < GifFile->Image.ColorMap->ColorCount; i++) {
          if (fread(Buf, 1, 3, Private->File) != 3) {
            _GifError = D_GIF_ERR_READ_FAILED;
            return GIF_ERROR;
          }
          GifFile->Image.ColorMap->Colors[i].Red = Buf[0];
          GifFile->Image.ColorMap->Colors[i].Green = Buf[1];
          GifFile->Image.ColorMap->Colors[i].Blue = Buf[2];
      }
    }

    if (GifFile->SavedImages) {
      SavedImage  *sp;

      if ((GifFile->SavedImages = (SavedImage *)realloc(GifFile->SavedImages,
                sizeof(SavedImage) * (GifFile->ImageCount + 1))) == NULL) {
          _GifError = D_GIF_ERR_NOT_ENOUGH_MEM;
          return GIF_ERROR;
      }

      sp = &GifFile->SavedImages[GifFile->ImageCount];
      memcpy(&sp->ImageDesc, &GifFile->Image, sizeof(GifImageDesc));
      sp->RasterBits = (char *)NULL;
      sp->ExtensionBlockCount = 0;
      sp->ExtensionBlocks = (ExtensionBlock *)NULL;
    }

    GifFile->ImageCount++;

    Private->PixelCount = (long) GifFile->Image.Width *
                      (long) GifFile->Image.Height;

    DGifSetupDecompress(GifFile);  /* Reset decompress algorithm parameters. */

    return GIF_OK;
}

/******************************************************************************
*  Get one full scanned line (Line) of length LineLen from GIF file.          *
******************************************************************************/
int DGifGetLine(GifFileType *GifFile, GifPixelType *Line, int LineLen)
{
    GifByteType *Dummy;
    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;

    if (!IS_READABLE(Private)) {
      /* This file was NOT open for reading: */
      _GifError = D_GIF_ERR_NOT_READABLE;
      return GIF_ERROR;
    }

    if (!LineLen) LineLen = GifFile->Image.Width;

#if defined(__MSDOS__) || defined(__GNUC__)
    if ((Private->PixelCount -= LineLen) > 0xffff0000UL) {
#else
    if ((Private->PixelCount -= LineLen) > 0xffff0000) {
#endif /* __MSDOS__ */
      _GifError = D_GIF_ERR_DATA_TOO_BIG;
      return GIF_ERROR;
    }

    if (DGifDecompressLine(GifFile, Line, LineLen) == GIF_OK) {
      if (Private->PixelCount == 0) {
          /* We probably would not be called any more, so lets clean         */
          /* everything before we return: need to flush out all rest of    */
          /* image until empty block (size 0) detected. We use GetCodeNext.*/
          do if (DGifGetCodeNext(GifFile, &Dummy) == GIF_ERROR)
            return GIF_ERROR;
          while (Dummy != NULL);
      }
      return GIF_OK;
    }
    else
      return GIF_ERROR;
}

/******************************************************************************
* Put one pixel (Pixel) into GIF file.                                  *
******************************************************************************/
int DGifGetPixel(GifFileType *GifFile, GifPixelType Pixel)
{
    GifByteType *Dummy;
    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;

    if (!IS_READABLE(Private)) {
      /* This file was NOT open for reading: */
      _GifError = D_GIF_ERR_NOT_READABLE;
      return GIF_ERROR;
    }

#if defined(__MSDOS__) || defined(__GNUC__)
    if (--Private->PixelCount > 0xffff0000UL)
#else
    if (--Private->PixelCount > 0xffff0000)
#endif /* __MSDOS__ */
    {
      _GifError = D_GIF_ERR_DATA_TOO_BIG;
      return GIF_ERROR;
    }

    if (DGifDecompressLine(GifFile, &Pixel, 1) == GIF_OK) {
      if (Private->PixelCount == 0) {
          /* We probably would not be called any more, so lets clean         */
          /* everything before we return: need to flush out all rest of    */
          /* image until empty block (size 0) detected. We use GetCodeNext.*/
          do if (DGifGetCodeNext(GifFile, &Dummy) == GIF_ERROR)
            return GIF_ERROR;
          while (Dummy != NULL);
      }
      return GIF_OK;
    }
    else
      return GIF_ERROR;
}

/******************************************************************************
*   Get an extension block (see GIF manual) from gif file. This routine only  *
* returns the first data block, and DGifGetExtensionNext shouldbe called      *
* after this one until NULL extension is returned.                      *
*   The Extension should NOT be freed by the user (not dynamically allocated).*
*   Note it is assumed the Extension desc. header ('!') has been read.        *
******************************************************************************/
int DGifGetExtension(GifFileType *GifFile, int *ExtCode,
                                        GifByteType **Extension)
{
    GifByteType Buf;
    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;

    if (!IS_READABLE(Private)) {
      /* This file was NOT open for reading: */
      _GifError = D_GIF_ERR_NOT_READABLE;
      return GIF_ERROR;
    }

    if (fread(&Buf, 1, 1, Private->File) != 1) {
      _GifError = D_GIF_ERR_READ_FAILED;
      return GIF_ERROR;
    }
    *ExtCode = Buf;

    return DGifGetExtensionNext(GifFile, Extension);
}

/******************************************************************************
*   Get a following extension block (see GIF manual) from gif file. This      *
* routine sould be called until NULL Extension is returned.             *
*   The Extension should NOT be freed by the user (not dynamically allocated).*
******************************************************************************/
int DGifGetExtensionNext(GifFileType *GifFile, GifByteType **Extension)
{
    GifByteType Buf;
    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;

    if (fread(&Buf, 1, 1, Private->File) != 1) {
      _GifError = D_GIF_ERR_READ_FAILED;
      return GIF_ERROR;
    }
    if (Buf > 0) {
      *Extension = Private->Buf;           /* Use private unused buffer. */
      (*Extension)[0] = Buf;  /* Pascal strings notation (pos. 0 is len.). */
      if (fread(&((*Extension)[1]), 1, Buf, Private->File) != Buf) {
          _GifError = D_GIF_ERR_READ_FAILED;
          return GIF_ERROR;
      }
    }
    else
      *Extension = NULL;

    return GIF_OK;
}

/******************************************************************************
*   This routine should be called last, to close the GIF file.                *
******************************************************************************/
int DGifCloseFile(GifFileType *GifFile)
{
    GifFilePrivateType *Private;
    FILE *File;

    if (GifFile == NULL) return GIF_ERROR;

    Private = (GifFilePrivateType *) GifFile->Private;

    if (!IS_READABLE(Private)) {
      /* This file was NOT open for reading: */
      _GifError = D_GIF_ERR_NOT_READABLE;
      return GIF_ERROR;
    }

    File = Private->File;

    if (GifFile->Image.ColorMap)
      FreeMapObject(GifFile->Image.ColorMap);
    if (GifFile->SColorMap)
      FreeMapObject(GifFile->SColorMap);
    if (Private)
      free((char *) Private);
    if (GifFile->SavedImages)
      FreeSavedImages(GifFile);
    free(GifFile);

    if (fclose(File) != 0) {
      _GifError = D_GIF_ERR_CLOSE_FAILED;
      return GIF_ERROR;
    }
    return GIF_OK;
}

/******************************************************************************
*   Get 2 bytes (word) from the given file:                             *
******************************************************************************/
static int DGifGetWord(FILE *File, int *Word)
{
    unsigned char c[2];

    if (fread(c, 1, 2, File) != 2) {
      _GifError = D_GIF_ERR_READ_FAILED;
      return GIF_ERROR;
    }

    *Word = (((unsigned int) c[1]) << 8) + c[0];
    return GIF_OK;
}

/******************************************************************************
*   Get the image code in compressed form.  his routine can be called if the  *
* information needed to be piped out as is. Obviously this is much faster     *
* than decoding and encoding again. This routine should be followed by calls  *
* to DGifGetCodeNext, until NULL block is returned.                     *
*   The block should NOT be freed by the user (not dynamically allocated).    *
******************************************************************************/
int DGifGetCode(GifFileType *GifFile, int *CodeSize, GifByteType **CodeBlock)
{
    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;

    if (!IS_READABLE(Private)) {
      /* This file was NOT open for reading: */
      _GifError = D_GIF_ERR_NOT_READABLE;
      return GIF_ERROR;
    }

    *CodeSize = Private->BitsPerPixel;

    return DGifGetCodeNext(GifFile, CodeBlock);
}

/******************************************************************************
*   Continue to get the image code in compressed form. This routine should be *
* called until NULL block is returned.                                  *
*   The block should NOT be freed by the user (not dynamically allocated).    *
******************************************************************************/
int DGifGetCodeNext(GifFileType *GifFile, GifByteType **CodeBlock)
{
    GifByteType Buf;
    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;

    if (fread(&Buf, 1, 1, Private->File) != 1) {
      _GifError = D_GIF_ERR_READ_FAILED;
      return GIF_ERROR;
    }

    if (Buf > 0) {
      *CodeBlock = Private->Buf;           /* Use private unused buffer. */
      (*CodeBlock)[0] = Buf;  /* Pascal strings notation (pos. 0 is len.). */
      if (fread(&((*CodeBlock)[1]), 1, Buf, Private->File) != Buf) {
          _GifError = D_GIF_ERR_READ_FAILED;
          return GIF_ERROR;
      }
    }
    else {
      *CodeBlock = NULL;
      Private->Buf[0] = 0;             /* Make sure the buffer is empty! */
      Private->PixelCount = 0;   /* And local info. indicate image read. */
    }

    return GIF_OK;
}

/******************************************************************************
*   Setup the LZ decompression for this image:                          *
******************************************************************************/
static int DGifSetupDecompress(GifFileType *GifFile)
{
    int i, BitsPerPixel;
    GifByteType CodeSize;
    unsigned int *Prefix;
    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;

    fread(&CodeSize, 1, 1, Private->File);    /* Read Code size from file. */
    BitsPerPixel = CodeSize;

    Private->Buf[0] = 0;                        /* Input Buffer empty. */
    Private->BitsPerPixel = BitsPerPixel;
    Private->ClearCode = (1 << BitsPerPixel);
    Private->EOFCode = Private->ClearCode + 1;
    Private->RunningCode = Private->EOFCode + 1;
    Private->RunningBits = BitsPerPixel + 1;     /* Number of bits per code. */
    Private->MaxCode1 = 1 << Private->RunningBits;     /* Max. code + 1. */
    Private->StackPtr = 0;              /* No pixels on the pixel stack. */
    Private->LastCode = NO_SUCH_CODE;
    Private->CrntShiftState = 0;    /* No information in CrntShiftDWord. */
    Private->CrntShiftDWord = 0;

    Prefix = Private->Prefix;
    for (i = 0; i <= LZ_MAX_CODE; i++) Prefix[i] = NO_SUCH_CODE;

    return GIF_OK;
}

/******************************************************************************
*   The LZ decompression routine:                                 *
*   This version decompress the given gif file into Line of length LineLen.   *
*   This routine can be called few times (one per scan line, for example), in *
* order the complete the whole image.                                   *
******************************************************************************/
static int DGifDecompressLine(GifFileType *GifFile, GifPixelType *Line,
                                                int LineLen)
{
    int i = 0, j, CrntCode, EOFCode, ClearCode, CrntPrefix, LastCode, StackPtr;
    GifByteType *Stack, *Suffix;
    unsigned int *Prefix;
    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;

    StackPtr = Private->StackPtr;
    Prefix = Private->Prefix;
    Suffix = Private->Suffix;
    Stack = Private->Stack;
    EOFCode = Private->EOFCode;
    ClearCode = Private->ClearCode;
    LastCode = Private->LastCode;

    if (StackPtr != 0) {
      /* Let pop the stack off before continueing to read the gif file: */
      while (StackPtr != 0 && i < LineLen) Line[i++] = Stack[--StackPtr];
    }

    while (i < LineLen) {                     /* Decode LineLen items. */
      if (DGifDecompressInput(Private, &CrntCode) == GIF_ERROR)
          return GIF_ERROR;

      if (CrntCode == EOFCode) {
          /* Note however that usually we will not be here as we will stop */
          /* decoding as soon as we got all the pixel, or EOF code will    */
          /* not be read at all, and DGifGetLine/Pixel clean everything.   */
          if (i != LineLen - 1 || Private->PixelCount != 0) {
            _GifError = D_GIF_ERR_EOF_TOO_SOON;
            return GIF_ERROR;
          }
          i++;
      }
      else if (CrntCode == ClearCode) {
          /* We need to start over again: */
          for (j = 0; j <= LZ_MAX_CODE; j++) Prefix[j] = NO_SUCH_CODE;
          Private->RunningCode = Private->EOFCode + 1;
          Private->RunningBits = Private->BitsPerPixel + 1;
          Private->MaxCode1 = 1 << Private->RunningBits;
          LastCode = Private->LastCode = NO_SUCH_CODE;
      }
      else {
          /* Its regular code - if in pixel range simply add it to output  */
          /* stream, otherwise trace to codes linked list until the prefix */
          /* is in pixel range:                                  */
          if (CrntCode < ClearCode) {
            /* This is simple - its pixel scalar, so add it to output:   */
            Line[i++] = CrntCode;
          }
          else {
            /* Its a code to needed to be traced: trace the linked list  */
            /* until the prefix is a pixel, while pushing the suffix     */
            /* pixels on our stack. If we done, pop the stack in reverse */
            /* (thats what stack is good for!) order to output.        */
            if (Prefix[CrntCode] == NO_SUCH_CODE) {
                /* Only allowed if CrntCode is exactly the running code: */
                /* In that case CrntCode = XXXCode, CrntCode or the          */
                /* prefix code is last code and the suffix char is           */
                /* exactly the prefix of last code!                    */
                if (CrntCode == Private->RunningCode - 2) {
                  CrntPrefix = LastCode;
                  Suffix[Private->RunningCode - 2] =
                  Stack[StackPtr++] = DGifGetPrefixChar(Prefix,
                                          LastCode, ClearCode);
                }
                else {
                  _GifError = D_GIF_ERR_IMAGE_DEFECT;
                  return GIF_ERROR;
                }
            }
            else
                CrntPrefix = CrntCode;

            /* Now (if image is O.K.) we should not get an NO_SUCH_CODE  */
            /* During the trace. As we might loop forever, in case of    */
            /* defective image, we count the number of loops we trace    */
            /* and stop if we got LZ_MAX_CODE. obviously we can not      */
            /* loop more than that.                              */
            j = 0;
            while (j++ <= LZ_MAX_CODE &&
                   CrntPrefix > ClearCode &&
                   CrntPrefix <= LZ_MAX_CODE) {
                Stack[StackPtr++] = Suffix[CrntPrefix];
                CrntPrefix = Prefix[CrntPrefix];
            }
            if (j >= LZ_MAX_CODE || CrntPrefix > LZ_MAX_CODE) {
                _GifError = D_GIF_ERR_IMAGE_DEFECT;
                return GIF_ERROR;
            }
            /* Push the last character on stack: */
            Stack[StackPtr++] = CrntPrefix;

            /* Now lets pop all the stack into output: */
            while (StackPtr != 0 && i < LineLen)
                Line[i++] = Stack[--StackPtr];
          }
          if (LastCode != NO_SUCH_CODE) {
            Prefix[Private->RunningCode - 2] = LastCode;

            if (CrntCode == Private->RunningCode - 2) {
                /* Only allowed if CrntCode is exactly the running code: */
                /* In that case CrntCode = XXXCode, CrntCode or the          */
                /* prefix code is last code and the suffix char is           */
                /* exactly the prefix of last code!                    */
                Suffix[Private->RunningCode - 2] =
                  DGifGetPrefixChar(Prefix, LastCode, ClearCode);
            }
            else {
                Suffix[Private->RunningCode - 2] =
                  DGifGetPrefixChar(Prefix, CrntCode, ClearCode);
            }
          }
          LastCode = CrntCode;
      }
    }

    Private->LastCode = LastCode;
    Private->StackPtr = StackPtr;

    return GIF_OK;
}

/******************************************************************************
* Routine to trace the Prefixes linked list until we get a prefix which is    *
* not code, but a pixel value (less than ClearCode). Returns that pixel value.*
* If image is defective, we might loop here forever, so we limit the loops to *
* the maximum possible if image O.k. - LZ_MAX_CODE times.               *
******************************************************************************/
static int DGifGetPrefixChar(unsigned int *Prefix, int Code, int ClearCode)
{
    int i = 0;

    while (Code > ClearCode && i++ <= LZ_MAX_CODE) Code = Prefix[Code];
    return Code;
}

/******************************************************************************
*   Interface for accessing the LZ codes directly. Set Code to the real code  *
* (12bits), or to -1 if EOF code is returned.                           *
******************************************************************************/
int DGifGetLZCodes(GifFileType *GifFile, int *Code)
{
    GifByteType *CodeBlock;
    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;

    if (!IS_READABLE(Private)) {
      /* This file was NOT open for reading: */
      _GifError = D_GIF_ERR_NOT_READABLE;
      return GIF_ERROR;
    }

    if (DGifDecompressInput(Private, Code) == GIF_ERROR)
      return GIF_ERROR;

    if (*Code == Private->EOFCode) {
      /* Skip rest of codes (hopefully only NULL terminating block): */
      do if (DGifGetCodeNext(GifFile, &CodeBlock) == GIF_ERROR)
          return GIF_ERROR;
      while (CodeBlock != NULL);

      *Code = -1;
    }
    else if (*Code == Private->ClearCode) {
      /* We need to start over again: */
      Private->RunningCode = Private->EOFCode + 1;
      Private->RunningBits = Private->BitsPerPixel + 1;
      Private->MaxCode1 = 1 << Private->RunningBits;
    }

    return GIF_OK;
}

/******************************************************************************
*   The LZ decompression input routine:                                 *
*   This routine is responsable for the decompression of the bit stream from  *
* 8 bits (bytes) packets, into the real codes.                          *
*   Returns GIF_OK if read succesfully.                                 *
******************************************************************************/
static int DGifDecompressInput(GifFilePrivateType *Private, int *Code)
{
    GifByteType NextByte;
    static unsigned int CodeMasks[] = {
      0x0000, 0x0001, 0x0003, 0x0007,
      0x000f, 0x001f, 0x003f, 0x007f,
      0x00ff, 0x01ff, 0x03ff, 0x07ff,
      0x0fff
    };

    while (Private->CrntShiftState < Private->RunningBits) {
      /* Needs to get more bytes from input stream for next code: */
      if (DGifBufferedInput(Private->File, Private->Buf, &NextByte)
          == GIF_ERROR) {
          return GIF_ERROR;
      }
      Private->CrntShiftDWord |=
            ((unsigned long) NextByte) << Private->CrntShiftState;
      Private->CrntShiftState += 8;
    }
    *Code = Private->CrntShiftDWord & CodeMasks[Private->RunningBits];

    Private->CrntShiftDWord >>= Private->RunningBits;
    Private->CrntShiftState -= Private->RunningBits;

    /* If code cannt fit into RunningBits bits, must raise its size. Note */
    /* however that codes above 4095 are used for special signaling.      */
    if (++Private->RunningCode > Private->MaxCode1 &&
      Private->RunningBits < LZ_BITS) {
      Private->MaxCode1 <<= 1;
      Private->RunningBits++;
    }
    return GIF_OK;
}

/******************************************************************************
*   This routines read one gif data block at a time and buffers it internally *
* so that the decompression routine could access it.                    *
*   The routine returns the next byte from its internal buffer (or read next  *
* block in if buffer empty) and returns GIF_OK if succesful.                  *
******************************************************************************/
static int DGifBufferedInput(FILE *File, GifByteType *Buf,
                                          GifByteType *NextByte)
{
    if (Buf[0] == 0) {
      /* Needs to read the next buffer - this one is empty: */
      if (fread(Buf, 1, 1, File) != 1)
      {
          _GifError = D_GIF_ERR_READ_FAILED;
          return GIF_ERROR;
      }
      if (fread(&Buf[1], 1, Buf[0], File) != Buf[0])
      {
          _GifError = D_GIF_ERR_READ_FAILED;
          return GIF_ERROR;
      }
      *NextByte = Buf[1];
      Buf[1] = 2;    /* We use now the second place as last char read! */
      Buf[0]--;
    }
    else {
      *NextByte = Buf[Buf[1]++];
      Buf[0]--;
    }

    return GIF_OK;
}

/******************************************************************************
* This routine reads an entire GIF into core, hanging all its state info off  *
* the GifFileType pointer.  Call DGifOpenFileName() or DGifOpenFileHandle()   *
* first to initialize I/O.  Its inverse is EGifSpew().                        *
******************************************************************************/
int DGifSlurp(GifFileType *GifFile)
{
    int i, j, Error, ImageSize;
    GifRecordType RecordType;
    SavedImage *sp;
    ExtensionBlock *ep;
    GifByteType *ExtData;

    /* Some versions of malloc dislike 0-length requests */
    GifFile->SavedImages = (SavedImage *)malloc(sizeof(SavedImage));

    do {
      if (DGifGetRecordType(GifFile, &RecordType) == GIF_ERROR)
          return(GIF_ERROR);

      switch (RecordType) {
          case IMAGE_DESC_RECORD_TYPE:
            if (DGifGetImageDesc(GifFile) == GIF_ERROR)
                return(GIF_ERROR);

            sp = &GifFile->SavedImages[GifFile->ImageCount-1];
            ImageSize = sp->ImageDesc.Width * sp->ImageDesc.Height;

            sp->RasterBits
                = (GifPixelType*) malloc(ImageSize * sizeof(GifPixelType));

            if (DGifGetLine(GifFile, sp->RasterBits, ImageSize)
                == GIF_ERROR)
                return(GIF_ERROR);

            break;

          case EXTENSION_RECORD_TYPE:

            if (DGifGetExtension(GifFile,&sp->Function,&ExtData)==GIF_ERROR)
                return(GIF_ERROR);
            else
            {
                ep = &sp->ExtensionBlocks[sp->ExtensionBlockCount++];

                ep->ByteCount = ExtData[0];
                ep->Bytes = (GifByteType *)malloc(ep->ByteCount * sizeof(GifByteType));
                memcpy(ep->Bytes, ExtData, ep->ByteCount * sizeof(char));
            }

            while (ExtData != NULL) {
                if (DGifGetExtensionNext(GifFile, &ExtData) == GIF_ERROR)
                  return(GIF_ERROR);
                else
                {
                  ep = &sp->ExtensionBlocks[sp->ExtensionBlockCount++];

                  ep->ByteCount = ExtData[0];
                  ep->Bytes = (GifByteType *)malloc(ep->ByteCount * sizeof(GifByteType));
                  memcpy(ep->Bytes,ExtData,ep->ByteCount * sizeof(char));
                }
            }
            break;

          case TERMINATE_RECORD_TYPE:
            break;

          default:      /* Should be trapped by DGifGetRecordType */
            break;
      }
    }
    while
      (RecordType != TERMINATE_RECORD_TYPE);

    return(GIF_OK);
}


Generated by  Doxygen 1.6.0   Back to index