implement SHA1sum; include "sys.m";	sys: Sys; include "draw.m"; include "keyring.m";	kr: Keyring; SHA1sum: module{	init: fn(nil : ref Draw->Context, argv: list of string);}; stderr: ref Sys->FD; init(nil: ref Draw->Context, argv: list of string){	sys = load Sys Sys->PATH;	stderr = sys->fildes(2);	kr = load Keyring Keyring->PATH;	a := tl argv;	err := 0;	if(a != nil){		for( ; a != nil; a = tl a) {			s := hd a;			fd := sys->open(s, Sys->OREAD);			if (fd == nil) {				sys->fprint(stderr, "sha1sum: cannot open %s: %r\n", s);				err = 1;			} else				err |= sha1sum(fd, s);		}	} else		err |= sha1sum(sys->fildes(0), "");	if(err)		raise "fail:error";} sha1sum(fd: ref Sys->FD, file: string): int{	err := 0;	buf := array[Sys->ATOMICIO] of byte;	state: ref Keyring->DigestState = nil;	nbytes := big 0;	while((nr := sys->read(fd, buf, len buf)) > 0){		state = kr->sha1(buf, nr, nil, state);		nbytes += big nr;	}	if(nr < 0) {		sys->fprint(stderr, "sha1sum: error reading %s: %r\n", file);		err = 1;	}	digest := array[Keyring->SHA1dlen] of byte;	kr->sha1(buf, 0, digest, state);	sum := "";	for(i:=0; i<len digest; i++)		sum += sys->sprint("%2.2ux", int digest[i]);	if(file != nil)		sys->print("%s\t%s\n", sum, file);	else		sys->print("%s\n", sum);	return err;}