implement Devpointer; include "sys.m";	sys: Sys; include "draw.m";	Pointer: import Draw; include "devpointer.m"; init(){	sys = load Sys Sys->PATH;} reader(file: string, posn: chan of ref Pointer, pid: chan of (int, string)){	if(file == nil)		file = "/dev/pointer";	dfd := sys->open(file, sys->OREAD);	if(dfd == nil){		if(pid != nil){			pid <-= (-1, sys->sprint("cannot open %s: %r", file));			return;		}	}	if(pid != nil)		pid <-= (sys->pctl(0, nil), nil);	b:= array[Size] of byte;	while(sys->read(dfd, b, len b) == Size)		posn <-= bytes2ptr(b);} bytes2ptr(b: array of byte): ref Pointer{	if(len b < Size || int b[0] != 'm')		return nil;	x := int string b[1:13];	y := int string b[13:25];	but := int string b[25:37];	msec := int string b[37:49];	return ref Pointer (but, (x, y), msec);} ptr2bytes(p: ref Pointer): array of byte{	if(p == nil)		return nil;	return sys->aprint("m%11d %11d %11d %11ud ", p.xy.x, p.xy.y, p.buttons, p.msec);} srv(c: chan of ref Pointer, f: ref Sys->FileIO){	ptrq := ref Ptrqueue;	dummy := chan of (int, int, int, Sys->Rread);	sys = load Sys Sys->PATH; 	for(;;){		r := dummy;		if(ptrq.nonempty())			r = f.read;		alt{		p := <-c =>			if(p == nil)				exit;			ptrq.put(p);		(nil, nil, nil, rc) := <-r =>			if(rc != nil){				alt{				rc <-= (ptr2bytes(ptrq.get()), nil) =>;				* =>;				}			}		(nil, nil, nil, rc) := <-f.write =>			if(rc != nil)				rc <-= (0, "read only");		}	}} Ptrqueue.put(q: self ref Ptrqueue, s: ref Pointer){	if(q.last != nil && s.buttons == q.last.buttons)		*q.last = *s;	else{		q.t = s :: q.t;		q.last = s;	}} Ptrqueue.get(q: self ref Ptrqueue): ref Pointer{	s: ref Pointer;	h := q.h;	if(h == nil){		for(t := q.t; t != nil; t = tl t)			h = hd t :: h;		q.t = nil;	}	if(h != nil){		s = hd h;		h = tl h;		if(h == nil)			q.last = nil;	}	q.h = h;	return s;}Ptrqueue.peek(q: self ref Ptrqueue): ref Pointer{	s: ref Pointer;	if (q.h == nil && q.t == nil)		return s;	t := q.last;	s = q.get();	q.h = s :: q.h;	q.last = t;	return s;}Ptrqueue.nonempty(q: self ref Ptrqueue): int{	return q.h != nil || q.t != nil;}