Category : C Source Code
Archive   : IMDSRC78.ZIP
Filename : GIF_LIB.C

/******************************************************************************
* "Gif-Lib" - Yet another gif library. *
* *
* Written by: Gershon Elber Ver 1.1, Aug. 1990 *
*******************************************************************************
* The kernel of the GIF Encoding process can be found here. *
*******************************************************************************
* History: *
* 14 Jun 89 - Version 1.0 by Gershon Elber. *
* 3 Sep 90 - Version 1.1 by Gershon Elber (Support for Gif89, Unique names). *
* 10 Nov 91 - Made Microsoft C compatible - Ron Baalke *
******************************************************************************/

#include
#include
#include
#include

#include
#include
#include
#include "gif_lib.h"
#include "gif_hash.h"
#include "mshell.h"

#define PROGRAM_NAME "GIF_LIBRARY"

#define COMMENT_EXT_FUNC_CODE 0xfe /* Extension function code for comment. */
#define GIF_STAMP "GIF87a" /* First chars in file - GIF stamp. */
#define ZL_MAX_CODE 4095 /* Biggest code possible in 12 bits. */

#define FILE_STATE_WRITE 0x01/* 1 write, 0 read - DGIF_LIB compatible.*/
#define FILE_STATE_SCREEN 0x02
#define FILE_STATE_IMAGE 0x04

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

#define IS_WRITEABLE(Private) (Private -> FileState & FILE_STATE_WRITE)

/* #define DEBUG_NO_PREFIX Dump only compressed data. */

typedef struct GifFilePrivateType {
int FileState,
FileHandle, /* Where old 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. */
CrntCode, /* Current algorithm code. */
CrntShiftState; /* Number of bits in CrntShiftDWord. */
unsigned long CrntShiftDWord, /* For bytes decomposition into codes. */
PixelCount;
FILE *File; /* File as stream. */
GifByteType Buf[256]; /* Compressed output is buffered here. */
GifHashTableType *HashTable;
} GifFilePrivateType;

GifFileType *GifFileIn;
GifFileType *GifFileOut;
GifColorType *GifPalette;
int _GifError;

/* Masks given codes to BitsPerPixel, to make sure all codes are in range: */
static GifPixelType CodeMask[] = {
0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff
};

#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 */

static char *GifVersionPrefix = GIF_STAMP;

static int EGifPutWord(int Word, FILE *File);
static int EGifSetupCompress(GifFileType *GifFile);
static int EGifCompressLine(GifFileType *GifFile, GifPixelType *Line,
int LineLen);
static int EGifCompressOutput(GifFilePrivateType *Private, int Code);
static int EGifBufferedOutput(FILE *File, GifByteType *Buf, int c);

/******************************************************************************
* Open a new gif file for write, given by its name. If TestExistance then *
* if the file exists this routines fails (returns NULL). *
* Returns GifFileType pointer dynamically allocated which serves as the gif *
* info record. _GifError is cleared if succesfull. *
******************************************************************************/
GifFileType *EGifOpenFileName(char *FileName, int TestExistance)
{
int FileHandle;

if (TestExistance)
FileHandle = open(FileName,
O_WRONLY | O_CREAT | O_EXCL
| O_BINARY
,
S_IREAD | S_IWRITE);
else
FileHandle = open(FileName,
O_WRONLY | O_CREAT | O_TRUNC
| O_BINARY
,
S_IREAD | S_IWRITE);

if (FileHandle == -1) {
_GifError = E_GIF_ERR_OPEN_FAILED;
return NULL;
}

return EGifOpenFileHandle(FileHandle);
}

/******************************************************************************
* Update a new gif file, given its file handle, which must be opened for *
* write in binary mode. *
* Returns GifFileType pointer dynamically allocated which serves as the gif *
* info record. _GifError is cleared if succesfull. *
******************************************************************************/
GifFileType *EGifOpenFileHandle(int FileHandle)
{
GifFileType *GifFile;
GifFilePrivateType *Private;
FILE *f;

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

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

GifFile -> SWidth = GifFile -> SHeight =
GifFile -> SColorResolution = GifFile -> SBitsPerPixel =
GifFile -> SBackGroundColor =
GifFile -> ILeft = GifFile -> ITop = GifFile -> IWidth = GifFile -> IHeight =
GifFile -> IInterlace =
GifFile -> IBitsPerPixel = 0;

GifFile -> SColorMap = GifFile -> IColorMap = NULL;

#ifndef DEBUG_NO_PREFIX
if (fwrite(GifVersionPrefix, 1, strlen(GifVersionPrefix), f) !=
strlen(GifVersionPrefix)) {
_GifError = E_GIF_ERR_WRITE_FAILED;
free(GifFile);
return NULL;
}
#endif /* DEBUG_NO_PREFIX */

if ((Private = (GifFilePrivateType *) malloc(sizeof(GifFilePrivateType)))
== NULL) {
_GifError = E_GIF_ERR_NOT_ENOUGH_MEM;
return NULL;
}

GifFile -> Private = (VoidPtr) Private;
Private -> FileHandle = FileHandle;
Private -> File = f;
Private -> FileState = FILE_STATE_WRITE;
if ((Private -> HashTable = _InitHashTable()) == NULL) {
_GifError = E_GIF_ERR_NOT_ENOUGH_MEM;
return NULL;
}

_GifError = 0;

return GifFile;
}

/******************************************************************************
* Routine to set current GIF version. All files open for write will be *
* using this version until next call to this routine. Version consists of *
* 3 characters as "87a" or "89a". No test is made to validate the version. *
******************************************************************************/
void EGifSetGifVersion(char *Version)
{
strncpy(&GifVersionPrefix[3], Version, 3);
}

/******************************************************************************
* This routine should be called before any other EGif calls, immediately *
* follows the GIF file openning. *
******************************************************************************/
int EGifPutScreenDesc(GifFileType *GifFile,
int Width, int Height, int ColorRes, int BackGround,
int BitsPerPixel, GifColorType *ColorMap)
{
int i, Size;
GifByteType Buf[3];
GifFilePrivateType *Private = (GifFilePrivateType *) GifFile -> Private;

if (Private -> FileState & FILE_STATE_SCREEN) {
/* If already has screen descriptor - something is wrong! */
_GifError = E_GIF_ERR_HAS_SCRN_DSCR;
return GIF_ERROR;
}
if (!IS_WRITEABLE(Private)) {
/* This file was NOT open for writing: */
_GifError = E_GIF_ERR_NOT_WRITEABLE;
return GIF_ERROR;
}

GifFile -> SWidth = Width;
GifFile -> SHeight = Height;
GifFile -> SColorResolution = ColorRes;
GifFile -> SBitsPerPixel = BitsPerPixel;
GifFile -> SBackGroundColor = BackGround;
if (ColorMap) {
Size = sizeof(GifColorType) * (1 << BitsPerPixel);
GifFile -> SColorMap = (GifColorType *) malloc(Size);
memcpy(GifFile -> SColorMap, ColorMap, Size);
}

/* Put the screen descriptor into the file: */
EGifPutWord(Width, Private -> File);
EGifPutWord(Height, Private -> File);
Buf[0] = (ColorMap ? 0x80 : 0x00) |
((ColorRes - 1) << 4) |
(BitsPerPixel - 1);
Buf[1] = BackGround;
Buf[2] = 0;
#ifndef DEBUG_NO_PREFIX
fwrite(Buf, 1, 3, Private -> File);
#endif /* DEBUG_NO_PREFIX */

/* If we have Global color map - dump it also: */
#ifndef DEBUG_NO_PREFIX
if (ColorMap != NULL)
for (i = 0; i < (1 << BitsPerPixel); i++) {
/* Put the ColorMap out also: */
Buf[0] = ColorMap[i].Red;
Buf[1] = ColorMap[i].Green;
Buf[2] = ColorMap[i].Blue;
if (fwrite(Buf, 1, 3, Private -> File) != 3) {
_GifError = E_GIF_ERR_WRITE_FAILED;
return GIF_ERROR;
}
}
#endif /* DEBUG_NO_PREFIX */

/* Mark this file as has screen descriptor, and no pixel written yet: */
Private -> FileState |= FILE_STATE_SCREEN;

return GIF_OK;
}

/******************************************************************************
* This routine should be called before any attemp to dump an image - any *
* call to any of the pixel dump routines. *
******************************************************************************/
int EGifPutImageDesc(GifFileType *GifFile,
int Left, int Top, int Width, int Height, int Interlace,
int BitsPerPixel, GifColorType *ColorMap)
{
int i, Size;
GifByteType Buf[3];
GifFilePrivateType *Private = (GifFilePrivateType *) GifFile -> Private;

if (Private -> FileState & FILE_STATE_IMAGE &&
#ifdef __MSDOS__
Private -> PixelCount > 0xffff0000UL) {
#else
Private -> PixelCount > 0xffff0000) {
#endif /* __MSDOS__ */
/* If already has active image descriptor - something is wrong! */
_GifError = E_GIF_ERR_HAS_IMAG_DSCR;
return GIF_ERROR;
}
if (!IS_WRITEABLE(Private)) {
/* This file was NOT open for writing: */
_GifError = E_GIF_ERR_NOT_WRITEABLE;
return GIF_ERROR;
}
GifFile -> ILeft = Left;
GifFile -> ITop = Top;
GifFile -> IWidth = Width;
GifFile -> IHeight = Height;
GifFile -> IBitsPerPixel = BitsPerPixel;
GifFile -> IInterlace = Interlace;
if (ColorMap) {
Size = sizeof(GifColorType) * (1 << BitsPerPixel);
if (GifFile -> IColorMap) free(GifFile -> IColorMap);
GifFile -> IColorMap = (GifColorType *) malloc(Size);
memcpy(GifFile -> IColorMap, ColorMap, Size);
}

/* Put the image descriptor into the file: */
Buf[0] = ','; /* Image seperator character. */
#ifndef DEBUG_NO_PREFIX
fwrite(Buf, 1, 1, Private -> File);
#endif /* DEBUG_NO_PREFIX */
EGifPutWord(Left, Private -> File);
EGifPutWord(Top, Private -> File);
EGifPutWord(Width, Private -> File);
EGifPutWord(Height, Private -> File);
Buf[0] = (ColorMap ? 0x80 : 0x00) |
(Interlace ? 0x40 : 0x00) |
(BitsPerPixel - 1);
#ifndef DEBUG_NO_PREFIX
fwrite(Buf, 1, 1, Private -> File);
#endif /* DEBUG_NO_PREFIX */

/* If we have Global color map - dump it also: */
#ifndef DEBUG_NO_PREFIX
if (ColorMap != NULL)
for (i = 0; i < (1 << BitsPerPixel); i++) {
/* Put the ColorMap out also: */
Buf[0] = ColorMap[i].Red;
Buf[1] = ColorMap[i].Green;
Buf[2] = ColorMap[i].Blue;
if (fwrite(Buf, 1, 3, Private -> File) != 3) {
_GifError = E_GIF_ERR_WRITE_FAILED;
return GIF_ERROR;
}
}
#endif /* DEBUG_NO_PREFIX */
if (GifFile -> SColorMap == NULL && GifFile -> IColorMap == NULL)
{
_GifError = E_GIF_ERR_NO_COLOR_MAP;
return GIF_ERROR;
}

/* Mark this file as has screen descriptor: */
Private -> FileState |= FILE_STATE_IMAGE;
Private -> PixelCount = (long) Width * (long) Height;

EGifSetupCompress(GifFile); /* Reset compress algorithm parameters. */

return GIF_OK;
}

/******************************************************************************
* Put one full scanned line (Line) of length LineLen into GIF file. *
******************************************************************************/
int EGifPutLine(GifFileType *GifFile, GifPixelType *Line, int LineLen)
{
int i;
GifPixelType Mask;
GifFilePrivateType *Private = (GifFilePrivateType *) GifFile -> Private;

if (!IS_WRITEABLE(Private)) {
/* This file was NOT open for writing: */
_GifError = E_GIF_ERR_NOT_WRITEABLE;
return GIF_ERROR;
}

if (!LineLen) LineLen = GifFile -> IWidth;
if ((Private -> PixelCount -= LineLen) < 0) {
_GifError = E_GIF_ERR_DATA_TOO_BIG;
return GIF_ERROR;
}

/* Make sure the codes are not out of bit range, as we might generate */
/* wrong code (because of overflow when we combine them) in this case: */
Mask = CodeMask[Private -> BitsPerPixel];
for (i = 0; i < LineLen; i++) Line[i] &= Mask;

return EGifCompressLine(GifFile, Line, LineLen);
}

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

if (!IS_WRITEABLE(Private)) {
/* This file was NOT open for writing: */
_GifError = E_GIF_ERR_NOT_WRITEABLE;
return GIF_ERROR;
}

if (--Private -> PixelCount < 0)
{
_GifError = E_GIF_ERR_DATA_TOO_BIG;
return GIF_ERROR;
}

/* Make sure the code is not out of bit range, as we might generate */
/* wrong code (because of overflow when we combine them) in this case: */
Pixel &= CodeMask[Private -> BitsPerPixel];

return EGifCompressLine(GifFile, &Pixel, 1);
}

/******************************************************************************
* Put a comment into GIF file using extension block. *
******************************************************************************/
int EGifPutComment(GifFileType *GifFile, char *Comment)
{
return EGifPutExtension(GifFile, COMMENT_EXT_FUNC_CODE, strlen(Comment),
Comment);
}

/******************************************************************************
* Put an extension block (see GIF manual) into gif file. *
******************************************************************************/
int EGifPutExtension(GifFileType *GifFile, int ExtCode, int ExtLen,
VoidPtr Extension)
{
GifByteType Buf[3];
GifFilePrivateType *Private = (GifFilePrivateType *) GifFile -> Private;

if (!IS_WRITEABLE(Private)) {
/* This file was NOT open for writing: */
_GifError = E_GIF_ERR_NOT_WRITEABLE;
return GIF_ERROR;
}

Buf[0] = '!';
Buf[1] = ExtCode;
Buf[2] = ExtLen;
fwrite(Buf, 1, 3, Private -> File);
fwrite(Extension, 1, ExtLen, Private -> File);
Buf[0] = 0;
fwrite(Buf, 1, 1, Private -> File);

return GIF_OK;
}

/******************************************************************************
* Put the image code in compressed form. This 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 EGifPutCodeNext, until NULL block is given. *
* The block should NOT be freed by the user (not dynamically allocated). *
******************************************************************************/
int EGifPutCode(GifFileType *GifFile, int CodeSize, GifByteType *CodeBlock)
{
GifFilePrivateType *Private = (GifFilePrivateType *) GifFile -> Private;

if (!IS_WRITEABLE(Private)) {
/* This file was NOT open for writing: */
_GifError = E_GIF_ERR_NOT_WRITEABLE;
return GIF_ERROR;
}

/* No need to dump code size as Compression set up does any for us: */
/*
Buf = CodeSize;
if (fwrite(&Buf, 1, 1, Private -> File) != 1) {
_GifError = E_GIF_ERR_WRITE_FAILED;
return GIF_ERROR;
}
*/

return EGifPutCodeNext(GifFile, CodeBlock);
}

/******************************************************************************
* Continue to put the image code in compressed form. This routine should be *
* called with blocks of code as read via DGifGetCode/DGifGetCodeNext. If *
* given buffer pointer is NULL, empty block is written to mark end of code. *
******************************************************************************/
int EGifPutCodeNext(GifFileType *GifFile, GifByteType *CodeBlock)
{
GifByteType Buf;
GifFilePrivateType *Private = (GifFilePrivateType *) GifFile -> Private;

if (CodeBlock != NULL) {
if (fwrite(CodeBlock, 1, CodeBlock[0] + 1, Private -> File)
!= CodeBlock[0] + 1) {
_GifError = E_GIF_ERR_WRITE_FAILED;
return GIF_ERROR;
}
}
else {
Buf = 0;

if (fwrite(&Buf, 1, 1, Private -> File) != 1) {
_GifError = E_GIF_ERR_WRITE_FAILED;
return GIF_ERROR;
}
Private -> PixelCount = 0; /* And local info. indicate image read. */
}

return GIF_OK;
}

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

if (GifFile == NULL) return GIF_ERROR;

Private = (GifFilePrivateType *) GifFile -> Private;
if (!IS_WRITEABLE(Private)) {
/* This file was NOT open for writing: */
_GifError = E_GIF_ERR_NOT_WRITEABLE;
return GIF_ERROR;
}

File = Private -> File;

Buf = ';';
fwrite(&Buf, 1, 1, Private -> File);

if (GifFile -> IColorMap) free(GifFile -> IColorMap);
if (GifFile -> SColorMap) free(GifFile -> SColorMap);
if (Private) {
if (Private -> HashTable) free(Private -> HashTable);
free(Private);
}
free(GifFile);

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

/******************************************************************************
* Put 2 bytes (word) into the given file: *
******************************************************************************/
static int EGifPutWord(int Word, FILE *File)
{
char c[2];

c[0] = Word & 0xff;
c[1] = (Word >> 8) & 0xff;
#ifndef DEBUG_NO_PREFIX
if (fwrite(c, 1, 2, File) == 2)
return GIF_OK;
else
return GIF_ERROR;
#else
return GIF_OK;
#endif /* DEBUG_NO_PREFIX */
}

/******************************************************************************
* Setup the LZ compression for this image: *
******************************************************************************/
static int EGifSetupCompress(GifFileType *GifFile)
{
int BitsPerPixel;
GifByteType Buf;
GifFilePrivateType *Private = (GifFilePrivateType *) GifFile -> Private;

/* Test and see what color map to use, and from it # bits per pixel: */
if (GifFile -> IColorMap)
BitsPerPixel = GifFile -> IBitsPerPixel;
else if (GifFile -> SColorMap)
BitsPerPixel = GifFile -> SBitsPerPixel;
else {
_GifError = E_GIF_ERR_NO_COLOR_MAP;
return GIF_ERROR;
}

Buf = BitsPerPixel = (BitsPerPixel < 2 ? 2 : BitsPerPixel);
fwrite(&Buf, 1, 1, Private -> File); /* Write the Code size to file. */

Private -> Buf[0] = 0; /* Nothing was output yet. */
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 -> CrntCode = FIRST_CODE; /* Signal that this is first one! */
Private -> CrntShiftState = 0; /* No information in CrntShiftDWord. */
Private -> CrntShiftDWord = 0;

/* Clear hash table and send Clear to make sure the decoder do the same. */
_ClearHashTable(Private -> HashTable);
if (EGifCompressOutput(Private, Private -> ClearCode) == GIF_ERROR) {
_GifError = E_GIF_ERR_DISK_IS_FULL;
return GIF_ERROR;
}
return GIF_OK;
}

/******************************************************************************
* The LZ compression routine: *
* This version compress the given buffer 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 EGifCompressLine(GifFileType *GifFile, GifPixelType *Line,
int LineLen)
{
int i = 0, CrntCode, NewCode;
unsigned long NewKey;
GifPixelType Pixel;
GifHashTableType *HashTable;
GifFilePrivateType *Private = (GifFilePrivateType *) GifFile -> Private;

HashTable = Private -> HashTable;

if (Private -> CrntCode == FIRST_CODE) /* Its first time! */
CrntCode = Line[i++];
else
CrntCode = Private -> CrntCode; /* Get last code in compression. */

while (i < LineLen) { /* Decode LineLen items. */
Pixel = Line[i++]; /* Get next pixel from stream. */
/* Form a new unique key to search hash table for the code combines */
/* CrntCode as Prefix string with Pixel as postfix char. */
NewKey = (((unsigned long) CrntCode) << 8) + Pixel;
if ((NewCode = _ExistsHashTable(HashTable, NewKey)) >= 0) {
/* This Key is already there, or the string is old one, so */
/* simple take new code as our CrntCode: */
CrntCode = NewCode;
}
else {
/* Put it in hash table, output the prefix code, and make our */
/* CrntCode equal to Pixel. */
if (EGifCompressOutput(Private, CrntCode)
== GIF_ERROR) {
_GifError = E_GIF_ERR_DISK_IS_FULL;
return GIF_ERROR;
}
CrntCode = Pixel;

/* If however the HashTable if full, we send a clear first and */
/* Clear the hash table. */
if (Private -> RunningCode >= ZL_MAX_CODE) {
/* Time to do some clearance: */
if (EGifCompressOutput(Private, Private -> ClearCode)
== GIF_ERROR) {
_GifError = E_GIF_ERR_DISK_IS_FULL;
return GIF_ERROR;
}
Private -> RunningCode = Private -> EOFCode + 1;
Private -> RunningBits = Private -> BitsPerPixel + 1;
Private -> MaxCode1 = 1 << Private -> RunningBits;
_ClearHashTable(HashTable);
}
else {
/* Put this unique key with its relative Code in hash table: */
_InsertHashTable(HashTable, NewKey, Private -> RunningCode++);
}
}
}

/* Preserve the current state of the compression algorithm: */
Private -> CrntCode = CrntCode;

if (Private -> PixelCount == 0)
{
/* We are done - output last Code and flush output buffers: */
if (EGifCompressOutput(Private, CrntCode)
== GIF_ERROR) {
_GifError = E_GIF_ERR_DISK_IS_FULL;
return GIF_ERROR;
}
if (EGifCompressOutput(Private, Private -> EOFCode)
== GIF_ERROR) {
_GifError = E_GIF_ERR_DISK_IS_FULL;
return GIF_ERROR;
}
if (EGifCompressOutput(Private, FLUSH_OUTPUT) == GIF_ERROR) {
_GifError = E_GIF_ERR_DISK_IS_FULL;
return GIF_ERROR;
}
}

return GIF_OK;
}

/******************************************************************************
* The LZ compression output routine: *
* This routine is responsable for the compression of the bit stream into *
* 8 bits (bytes) packets. *
* Returns GIF_OK if written succesfully. *
******************************************************************************/
static int EGifCompressOutput(GifFilePrivateType *Private, int Code)
{
int retval = GIF_OK;

if (Code == FLUSH_OUTPUT) {
while (Private -> CrntShiftState > 0) {
/* Get Rid of what is left in DWord, and flush it. */
if (EGifBufferedOutput(Private -> File, Private -> Buf,
Private -> CrntShiftDWord & 0xff) == GIF_ERROR)
retval = GIF_ERROR;
Private -> CrntShiftDWord >>= 8;
Private -> CrntShiftState -= 8;
}
Private -> CrntShiftState = 0; /* For next time. */
if (EGifBufferedOutput(Private -> File, Private -> Buf,
FLUSH_OUTPUT) == GIF_ERROR)
retval = GIF_ERROR;
}
else {
Private -> CrntShiftDWord |= ((long) Code) << Private -> CrntShiftState;
Private -> CrntShiftState += Private -> RunningBits;
while (Private -> CrntShiftState >= 8) {
/* Dump out full bytes: */
if (EGifBufferedOutput(Private -> File, Private -> Buf,
Private -> CrntShiftDWord & 0xff) == GIF_ERROR)
retval = GIF_ERROR;
Private -> CrntShiftDWord >>= 8;
Private -> CrntShiftState -= 8;
}
}

/* 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 && Code <= 4095) {
Private -> MaxCode1 = 1 << ++Private -> RunningBits;
}

return retval;
}

/******************************************************************************
* This routines buffers the given characters until 255 characters are ready *
* to be output. If Code is equal to -1 the buffer is flushed (EOF). *
* The buffer is Dumped with first byte as its size, as GIF format requires. *
* Returns GIF_OK if written succesfully. *
******************************************************************************/
static int EGifBufferedOutput(FILE *File, GifByteType *Buf, int c)
{
if (c == FLUSH_OUTPUT) {
/* Flush everything out. */
if (Buf[0] != 0 && fwrite(Buf, 1, Buf[0]+1, File) != Buf[0] + 1)
{
_GifError = E_GIF_ERR_WRITE_FAILED;
return GIF_ERROR;
}
/* Mark end of compressed data, by an empty block (see GIF doc): */
Buf[0] = 0;
if (fwrite(Buf, 1, 1, File) != 1)
{
_GifError = E_GIF_ERR_WRITE_FAILED;
return GIF_ERROR;
}
}
else {
if (Buf[0] == 255) {
/* Dump out this buffer - it is full: */
if (fwrite(Buf, 1, Buf[0] + 1, File) != Buf[0] + 1)
{
_GifError = E_GIF_ERR_WRITE_FAILED;
return GIF_ERROR;
}
Buf[0] = 0;
}
Buf[++Buf[0]] = c;
}

return GIF_OK;
}