implement Plumbmsg; include "sys.m";	sys: Sys; include "plumbmsg.m"; input: ref Sys->FD;port: ref Sys->FD;portname: string;maxdatasize: int; init(doinput: int, rcvport: string, maxdata: int): int{	sys = load Sys Sys->PATH; 	if(!doinput && rcvport == nil)	# server, not client		return 1;	input = sys->open("/chan/plumb.input", Sys->OWRITE);	if(input == nil)		return -1;	if(rcvport == nil)	# sending messages but never receiving them		return 1;	port = sys->open("/chan/plumb."+rcvport, Sys->OREAD);	if(port == nil){		input = nil;		return -1;	}	maxdatasize = maxdata;	portname = rcvport;	msg := ref Msg;	msg.src = portname;	msg.dst = "plumb";	msg.kind = "text";	msg.data = array of byte "start";	if(msg.send() < 0){		port = nil;		input = nil;		return -1;	}	return 1;} shutdown(){	msg := ref Msg;	msg.src = portname;	msg.dst = "plumb";	msg.kind = "text";	msg.data = array of byte "stop";	msg.send();} Msg.send(msg: self ref Msg): int{	hdr :=		msg.src+"\n"+		msg.dst+"\n"+		msg.dir+"\n"+		msg.kind+"\n"+		msg.attr+"\n"+		string len msg.data+"\n";	ahdr := array of byte hdr;	b := array[len ahdr+len msg.data] of byte;	b[0:] = ahdr;	b[len ahdr:] = msg.data;	return sys->write(input, b, len b);} Msg.recv(): ref Msg{	b := array[maxdatasize+1000] of byte;	n := sys->read(port, b, len b);	if(n <= 0)		return nil;	return Msg.unpack(b[0:n]);} Msg.unpack(b: array of byte): ref Msg{	(hdr, data) := unpack(b, 6);	if(hdr == nil)		return nil; 	msg := ref Msg;	msg.src = hdr[0];	msg.dst = hdr[1];	msg.dir = hdr[2];	msg.kind = hdr[3];	msg.attr = hdr[4];	msg.data = data; 	return msg;} Msg.pack(msg: self ref Msg): array of byte{	hdr :=		msg.src+"\n"+		msg.dst+"\n"+		msg.dir+"\n"+		msg.kind+"\n"+		msg.attr+"\n"+		string len msg.data+"\n";	ahdr := array of byte hdr;	b := array[len ahdr+len msg.data] of byte;	b[0:] = ahdr;	b[len ahdr:] = msg.data;	return b;} # unpack message from array of bytes.  last string in message# is number of bytes in data portion of messageunpack(b: array of byte, ns: int): (array of string, array of byte){	i := 0;	a := array[ns] of string;	for(n:=0; n<ns; n++){		(i, a[n]) = unpackstring(b, i);		if(i < 0)			return (nil, nil);	}	nb := int a[ns-1];	if((len b)-i != nb){		sys->print("unpack: bad message format: wrong nbytes\n");		return (nil, nil);	}	# copy data so b can be reused or freed	data := array[nb] of byte;	data[0:] = b[i:];	return (a, data);} unpackstring(b: array of byte, i: int): (int, string){	starti := i;	while(i < len b){		if(b[i] == byte '\n')			return (i+1, string b[starti:i]);		i++;	}	return (-1, nil);} string2attrs(s: string): list of ref Attr{	(nil, pairs) := sys->tokenize(s, "\t");	if(pairs == nil)		return nil;	attrs: list of ref Attr;	while(pairs != nil){		pair := hd pairs;		pairs = tl pairs;		a := ref Attr;		for(i:=0; i<len pair; i++)			if(pair[i] == '='){				a.name = pair[0:i];				if(++i < len pair)					a.val = pair[i:];				break;			}		attrs = a :: attrs;	}	return attrs;} attrs2string(l: list of ref Attr): string{	s := "";	while(l != nil){		a := hd l;		l = tl l;		if(s == "")			s = a.name + "=" + a.val;		else			s += "\t" + a.name + "=" + a.val;	}	return s;} lookup(attrs: list of ref Attr, name: string): (int, string){	while(attrs != nil){		a := hd attrs;		attrs = tl attrs;		if(a.name == name)			return (1, a.val);	}	return (0, nil);}