dgif_lib.c

Sigma SMP8634 Mrua v. 2.8.2.0

    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;
    int j, CrntCode, EOFCode, ClearCode, CrntPrefix, LastCode, StackPtr;
    GifByteType *Stack, *Suffix;
    GifPrefixType *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(GifFile, &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(GifPrefixType *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(GifFile, 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(GifFileType * GifFile,
                    int *Code) {
    
    GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;

    GifByteType NextByte;
    static unsigned short CodeMasks[] = {
        0x0000, 0x0001, 0x0003, 0x0007,
        0x000f, 0x001f, 0x003f, 0x007f,
        0x00ff, 0x01ff, 0x03ff, 0x07ff,
        0x0fff
    };
    /* The image can't contain more than LZ_BITS per code. */
    if (Private->RunningBits > LZ_BITS) {
        _GifError = D_GIF_ERR_IMAGE_DEFECT;
        return GIF_ERROR;
    }
    
    while (Private->CrntShiftState < Private->RunningBits) {
        /* Needs to get more bytes from input stream for next code: */
        if (DGifBufferedInput(GifFile, 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 cannot fit into RunningBits bits, must raise its size. Note
     * however that codes above 4095 are used for special signaling.
     * If we're using LZ_BITS bits already and we're at the max code, just
     * keep using the table as it is, don't increment Private->RunningCode.
     */
    if (Private->RunningCode < LZ_MAX_CODE + 2 &&
            ++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(GifFileType * GifFile,
                  GifByteType * Buf,
                  GifByteType * NextByte) {

    if (Buf[0] == 0) {
        /* Needs to read the next buffer - this one is empty: */
        if (READ(GifFile, Buf, 1) != 1) {
            _GifError = D_GIF_ERR_READ_FAILED;
            return GIF_ERROR;
        }
        /* There shouldn't be any empty data blocks here as the LZW spec
         * says the LZW termination code should come first.  Therefore we
         * shouldn't be inside this routine at that point.
         */
        if (Buf[0] == 0) {
            _GifError = D_GIF_ERR_IMAGE_DEFECT;
            return GIF_ERROR;
        }
        if (READ(GifFile, &Buf[1], Buf[0]) != 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;
}
#ifndef _GBA_NO_FILEIO

/******************************************************************************
 * 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 ImageSize;
    GifRecordType RecordType;
    SavedImage *sp;
    GifByteType *ExtData;
    SavedImage temp_save;

    temp_save.ExtensionBlocks = NULL;
    temp_save.ExtensionBlockCount = 0;

    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 = (unsigned char *)malloc(ImageSize *
                                                       sizeof(GifPixelType));
              if (sp->RasterBits == NULL) {
                  return GIF_ERROR;
              }
              if (DGifGetLine(GifFile, sp->RasterBits, ImageSize) ==
                  GIF_ERROR)
                  return (GIF_ERROR);
              if (temp_save.ExtensionBlocks) {
                  sp->ExtensionBlocks = temp_save.ExtensionBlocks;
                  sp->ExtensionBlockCount = temp_save.ExtensionBlockCount;

                  temp_save.ExtensionBlocks = NULL;
                  temp_save.ExtensionBlockCount = 0;

                  /* FIXME: The following is wrong.  It is left in only for
                   * backwards compatibility.  Someday it should go away. Use 
                   * the sp->ExtensionBlocks->Function variable instead. */
                  sp->Function = sp->ExtensionBlocks[0].Function;
              }
              break;

          case EXTENSION_RECORD_TYPE:
              if (DGifGetExtension(GifFile, &temp_save.Function, &ExtData) ==
                  GIF_ERROR)
                  return (GIF_ERROR);
              while (ExtData != NULL) {

                  /* Create an extension block with our data */
                  if (AddExtensionBlock(&temp_save, ExtData[0], &ExtData[1])
                      == GIF_ERROR)
                      return (GIF_ERROR);

                  if (DGifGetExtensionNext(GifFile, &ExtData) == GIF_ERROR)
                      return (GIF_ERROR);
                  temp_save.Function = 0;
              }
              break;

          case TERMINATE_RECORD_TYPE:
              break;

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

    /* Just in case the Gif has an extension block without an associated
     * image... (Should we save this into a savefile structure with no image
     * instead? Have to check if the present writing code can handle that as
     * well.... */
    if (temp_save.ExtensionBlocks)
        FreeExtension(&temp_save);

    return (GIF_OK);
}
#endif /* _GBA_NO_FILEIO */