www.pudn.com > giflib12.zip > 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
#include
#include
#include
#else
#include
#include
#endif /* __MSDOS__ */
#include
#include
#include
#include "gif_lib.h"
#include "gif_hash.h"
#define PROGRAM_NAME "GIF_LIBRARY"
#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. */
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(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;
}
if ((Private = (GifFilePrivateType *) malloc(sizeof(GifFilePrivateType)))
== NULL) {
_GifError = D_GIF_ERR_NOT_ENOUGH_MEM;
free((char *) GifFile);
return NULL;
}
GifFile -> Private = (VoidPtr) Private;
GifFile -> SColorMap = GifFile -> IColorMap = NULL;
Private -> FileHandle = FileHandle;
Private -> File = f;
Private -> FileState = 0; /* Make sure bit 0 = 0 (File open for read). */
/* Lets see if this is 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 Size, i;
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;
GifFile -> SBitsPerPixel = (Buf[0] & 0x07) + 1;
GifFile -> SBackGroundColor = Buf[1];
if (Buf[0] & 0x80) { /* Do we have global color map? */
Size = (1 << GifFile -> SBitsPerPixel);
GifFile -> SColorMap =
(GifColorType *) malloc(sizeof(GifColorType) * Size);
for (i = 0; i < Size; i++) { /* Get the global color map: */
if (fread(Buf, 1, 3, Private -> File) != 3) {
_GifError = D_GIF_ERR_READ_FAILED;
return GIF_ERROR;
}
GifFile -> SColorMap[i].Red = Buf[0];
GifFile -> SColorMap[i].Green = Buf[1];
GifFile -> SColorMap[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 Size, i;
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 -> ILeft) == GIF_ERROR ||
DGifGetWord(Private -> File, &GifFile -> ITop) == GIF_ERROR ||
DGifGetWord(Private -> File, &GifFile -> IWidth) == GIF_ERROR ||
DGifGetWord(Private -> File, &GifFile -> IHeight) == GIF_ERROR)
return GIF_ERROR;
if (fread(Buf, 1, 1, Private -> File) != 1) {
_GifError = D_GIF_ERR_READ_FAILED;
return GIF_ERROR;
}
GifFile -> IBitsPerPixel = (Buf[0] & 0x07) + 1;
GifFile -> IInterlace = (Buf[0] & 0x40);
if (Buf[0] & 0x80) { /* Does this image have local color map? */
Size = (1 << GifFile -> IBitsPerPixel);
if (GifFile -> IColorMap) free((char *) GifFile -> IColorMap);
GifFile -> IColorMap =
(GifColorType *) malloc(sizeof(GifColorType) * Size);
for (i = 0; i < Size; i++) { /* Get the image local color map: */
if (fread(Buf, 1, 3, Private -> File) != 3) {
_GifError = D_GIF_ERR_READ_FAILED;
return GIF_ERROR;
}
GifFile -> IColorMap[i].Red = Buf[0];
GifFile -> IColorMap[i].Green = Buf[1];
GifFile -> IColorMap[i].Blue = Buf[2];
}
}
Private -> PixelCount = (long) GifFile -> IWidth *
(long) GifFile -> IHeight;
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 -> IWidth;
#ifdef __MSDOS__
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;
}
#ifdef __MSDOS__
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 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 -> IColorMap) free((char *) GifFile -> IColorMap);
if (GifFile -> SColorMap) free((char *) GifFile -> SColorMap);
if (Private) free((char *) Private);
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;
}