Category : Printer + Display Graphics
Archive   : GFB101.ZIP
Filename : GIFCODE.C

 
Output of file : GIFCODE.C contained in archive : GFB101.ZIP
/* gifcode.c - GIF encoder/decoder routines. */

#include
#include

#include "uffile.h"
#include "gifcode.h"

static void
init_coder(gc,ff,datasize)
GIF_CODER *gc; FFILE *ff; int datasize;
{
int c;

gc->ff = ff;
gc->curblocksize = gc->curblockpos = 0;
gc->nbits = 0;
gc->bits = 0L;
gc->datasize = datasize;
gc->clear = (1< gc->eoi = gc->clear+1;
for (c=0; cclear; c++) {
gc->prefix[c] = -1;
gc->suffix[c] = c;
}
}



static void
reset_codesize(gc)
GIF_CODER *gc;
{
gc->codesize = gc->datasize+1;
gc->codemask = (1<codesize)-1;
gc->avail = gc->eoi+1;
}

static void
inc_codesize(gc)
GIF_CODER *gc;
{
gc->codesize++;
gc->codemask = (1<codesize)-1;
}

static void
clear_encoder(gc)
GIF_CODER *gc;
{
reset_codesize(gc);
memset(gc->u.e.sl_ptr,0,GIF_MAXCODES*sizeof(int));
gc->u.e.sl_index = 1;
}

static void
clear_decoder(gc)
GIF_CODER *gc;
{
reset_codesize(gc);
gc->u.d.prevc = -1;
}

void
gif_start_encoding(gc,ff,datasize)
GIF_CODER *gc; FFILE *ff; int datasize;
{
init_coder(gc,ff,datasize);
clear_encoder(gc);
gc->u.e.curprefix = -1;
}

static int
putcurblock(gc)
GIF_CODER *gc;
{
if (ff_putc(gc->curblocksize,gc->ff)==EOF
|| ff_write(gc->curblock,gc->curblocksize,gc->ff)!=gc->curblocksize)
return -1;
gc->curblocksize = 0;
return 0;
}

static int
putcode(c,gc)
int c; GIF_CODER *gc;
{
gc->bits |= (((long)(c&gc->codemask))<nbits);
gc->nbits += gc->codesize;
while (gc->nbits >= 8) {
gc->curblock[gc->curblocksize++] = (gc->bits&0xFF);
gc->bits >>= 8;
gc->nbits -= 8;
if (gc->curblocksize==254 && putcurblock(gc)<0)
return -1;
}
return 0;
}

static int
end_putcode(gc)
GIF_CODER *gc;
{
if (putcode(gc->eoi,gc) < 0)
return -1;
if (gc->nbits > 0)
gc->curblock[gc->curblocksize++] = (gc->bits&0xFF);
if (gc->curblocksize>0 && putcurblock(gc)<0)
return -1;
if (ff_putc(0,gc->ff) == EOF)
return -1;
return 0;
}

static int
getcode(gc)
GIF_CODER *gc;
{
int size,c;

while (gc->nbits < gc->codesize) {
if (gc->curblockpos < gc->curblocksize) {
gc->bits |= (((long)gc->curblock[gc->curblockpos++])<nbits);
gc->nbits += 8;
} else if ((size=ff_getc(gc->ff))==EOF || size==0
|| ff_read(gc->curblock,size,gc->ff)!=size)
return -1;
else {
gc->curblocksize = size;
gc->curblockpos = 0;
}
}
c = (int)(gc->bits&gc->codemask);
gc->bits >>= gc->codesize;
gc->nbits -= gc->codesize;
return c;
}

static int
end_getcode(gc)
GIF_CODER *gc;
{
int size;

if (gc->curblockpos == gc->curblocksize) {
if ((size=ff_getc(gc->ff)) == 0)
return 0;
else if (size==EOF || ff_read(gc->curblock,size,gc->ff)!=size)
return -1;
else {
gc->curblocksize = size;
gc->curblockpos = 0;
}
}
if (getcode(gc) != gc->eoi)
return -1;
if (ff_getc(gc->ff) == 0)
return 0;
else
return -1;
}

static int
check_codetable(gc,c)
GIF_CODER *gc; int c;
{
int ind;

ind = gc->u.e.sl_ptr[gc->u.e.curprefix];
while (ind != 0)
if (c == gc->u.e.sl_suffix[ind])
return gc->u.e.sl_newprefix[ind];
else
ind = gc->u.e.sl_next[ind];
return -1;
}

static void
add_to_codetable(gc,newc)
GIF_CODER *gc; int newc;
{
int ind;

ind = gc->u.e.sl_index++;
gc->u.e.sl_next[ind] = gc->u.e.sl_ptr[gc->prefix[newc]];
gc->u.e.sl_ptr[gc->prefix[newc]] = ind;
gc->u.e.sl_suffix[ind] = gc->suffix[newc];
gc->u.e.sl_newprefix[ind] = newc;
}

int
gif_encode_c(c,gc)
int c; GIF_CODER *gc;
{
int newpref,newc;

if (gc->u.e.curprefix < 0) {
gc->u.e.curprefix = c;
return putcode(gc->clear,gc);
} else if ((newpref=check_codetable(gc,c)) >= 0) {
gc->u.e.curprefix = newpref;
return 0;
}
newc = gc->avail++;
gc->prefix[newc] = gc->u.e.curprefix;
gc->suffix[newc] = c;
add_to_codetable(gc,newc);
if (putcode(gc->u.e.curprefix,gc) < 0)
return -1;
gc->u.e.curprefix = c;
if (gc->avail == GIF_MAXCODES) {
if (putcode(gc->clear,gc) < 0)
return -1;
clear_encoder(gc);
} else if (gc->codemask < newc)
inc_codesize(gc);
return 0;
}

int
gif_end_encoding(gc)
GIF_CODER *gc;
{
if ((gc->u.e.curprefix>=0 && putcode(gc->u.e.curprefix,gc)<0)
|| end_putcode(gc)<0)
return -1;
else
return 0;
}

void
gif_start_decoding(gc,ff,datasize)
GIF_CODER *gc; FFILE *ff; int datasize;
{
int c;

init_coder(gc,ff,datasize);
clear_decoder(gc);
for (c=0; cclear; c++)
gc->u.d.first[c] = c;
gc->u.d.csttop = 0;
}

int
gif___f_decode_c(gc)
GIF_CODER *gc;
{
int c,newc;

for (;;) {
if (gc->u.d.csttop > 0)
return gc->u.d.cstack[--gc->u.d.csttop];
else if ((c=getcode(gc))<0 || c==gc->eoi || gc->avail return -1;
else if (c == gc->clear)
clear_decoder(gc);
else {
if (gc->u.d.prevc>=0 && gc->avail newc = gc->avail++;
gc->prefix[newc] = gc->u.d.prevc;
gc->u.d.first[newc] = gc->u.d.first[gc->u.d.prevc];
gc->suffix[newc] = gc->u.d.first[c];
if (gc->codemaskavail && gc->avail inc_codesize(gc);
}
if (c == gc->avail)
return -1;
gc->u.d.prevc = c;
do {
gc->u.d.cstack[gc->u.d.csttop++] = gc->suffix[c];
c = gc->prefix[c];
} while (c >= 0);
}
}
}

int
gif_end_decoding(gc)
GIF_CODER *gc;
{
if (end_getcode(gc) < 0)
return -1;
else
return 0;
}



  3 Responses to “Category : Printer + Display Graphics
Archive   : GFB101.ZIP
Filename : GIFCODE.C

  1. Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!

  2. This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.

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