#include <u.h>
#include <libc.h>
#include <draw.h>
#include <memdraw.h>

int
memsetchan(Memimage *i, ulong chan)
{
	int d;
	int t, j, k;
	ulong cc;
	int bytes;

	if((d = chantodepth(chan)) == 0) {
		werrstr("bad channel descriptor");
		return -1;
	}

	i->depth = d;
	i->chan = chan;
	i->flags &= ~(Fgrey|Falpha|Fcmap|Fbytes);
	bytes = 1;
	for(cc=chan, j=0, k=0; cc; j+=NBITS(cc), cc>>=8, k++){
		t=TYPE(cc);
		if(t < 0 || t >= NChan){
			werrstr("bad channel string");
			return -1;
		}
		if(t == CGrey)
			i->flags |= Fgrey;
		if(t == CAlpha)
			i->flags |= Falpha;
		if(t == CMap && i->cmap == nil){
			i->cmap = memdefcmap;
			i->flags |= Fcmap;
		}

		i->shift[t] = j;
		i->mask[t] = (1<<NBITS(cc))-1;
		i->nbits[t] = NBITS(cc);
		if(NBITS(cc) != 8)
			bytes = 0;
	}
	i->nchan = k;
	if(bytes)
		i->flags |= Fbytes;
	return 0;
}