ref: c639a4ea5793878eb8589ec4d422e4c9952a42fc
dir: /sys/src/libdraw/computil.c/
#include <u.h>
#include <libc.h>
#include <draw.h>
/*
* compressed data are seuences of byte codes.
* if the first byte b has the 0x80 bit set, the next (b^0x80)+1 bytes
* are data. otherwise, it's two bytes specifying a previous string to repeat.
*/
void
_twiddlecompressed(uchar *buf, int n)
{
uchar *ebuf;
int j, k, c;
ebuf = buf+n;
while(buf < ebuf){
c = *buf++;
if(c >= 128){
k = c-128+1;
for(j=0; j<k; j++, buf++)
*buf ^= 0xFF;
}else
buf++;
}
}
int
_compblocksize(Rectangle r, int depth)
{
int bpl;
bpl = bytesperline(r, depth);
bpl = 2*bpl; /* add plenty extra for blocking, etc. */
if(bpl < NCBLOCK)
return NCBLOCK;
return bpl;
}