implement Sum; include "sys.m";include "draw.m";include "crc.m"; Sum : module{	init : fn(nil : ref Draw->Context, argv : list of string);}; init(nil : ref Draw->Context, argv : list of string){	sys := load Sys Sys->PATH;	stderr := sys->fildes(2);	crcm := load Crc Crc->PATH;	crcs := crcm->init(0, 0);	a := tl argv;	buf := array[Sys->ATOMICIO] of byte;	err := 0;	for ( ; a != nil; a = tl a) {		s := hd a;		(ok, d) := sys->stat(s);		if (ok < 0) {			sys->fprint(stderr, "sum: cannot get status of %s: %r\n", s);			err = 1;			continue;		}		if (d.mode & Sys->DMDIR)			continue;		fd := sys->open(s, Sys->OREAD);		if (fd == nil) {			sys->fprint(stderr, "sum: cannot open %s: %r\n", s);			err = 1;			continue;		}		crc := 0;		nbytes := big 0;		while((nr := sys->read(fd, buf, len buf)) > 0){			crc = crcm->crc(crcs, buf, nr);			nbytes += big nr;		}		if(nr < 0) {			sys->fprint(stderr, "sum: error reading %s: %r\n", s);			err = 1;		}		# encode the length but make n==0 not 0		l := int (nbytes & big 16rFFFFFFFF);		buf[0] = byte((l>>24)^16rCC);		buf[1] = byte((l>>16)^16r55);		buf[2] = byte((l>>8)^16rCC);		buf[3] = byte(l^16r55);		crc = crcm->crc(crcs, buf, 4);		sys->print("%.8ux %6bd %s\n", crc, nbytes, s);		crcm->reset(crcs);	}	if(err)		raise "fail:error";}