20060303a

1 files changed, 934 insertions, 0 deletions

diff --git a/appl/lib/styx.b b/appl/lib/styx.b
new file mode 100644
index 00000000..f4534c6c
--- /dev/null
+++ b/appl/lib/styx.b
@@ -0,0 +1,934 @@
+implement Styx;
+
+include "sys.m";
+	sys: Sys;
+
+include "styx.m";
+
+STR: con BIT16SZ;	# string length
+TAG: con BIT16SZ;
+FID: con BIT32SZ;
+QID: con BIT8SZ+BIT32SZ+BIT64SZ;
+LEN: con BIT16SZ;	# stat and qid array lengths
+COUNT: con BIT32SZ;
+OFFSET: con BIT64SZ;
+
+H: con BIT32SZ+BIT8SZ+BIT16SZ;	# minimum header length: size[4] type tag[2]
+
+#
+# the following array could be shorter if it were indexed by (type-Tversion)
+#
+hdrlen := array[Tmax] of
+{
+Tversion =>	H+COUNT+STR,	# size[4] Tversion tag[2] msize[4] version[s]
+Rversion =>	H+COUNT+STR,	# size[4] Rversion tag[2] msize[4] version[s]
+
+Tauth =>	H+FID+STR+STR,		# size[4] Tauth tag[2] afid[4] uname[s] aname[s]
+Rauth =>	H+QID,			# size[4] Rauth tag[2] aqid[13]
+
+Rerror =>	H+STR,		# size[4] Rerror tag[2] ename[s]
+
+Tflush =>	H+TAG,		# size[4] Tflush tag[2] oldtag[2]
+Rflush =>	H,			# size[4] Rflush tag[2]
+
+Tattach =>	H+FID+FID+STR+STR,	# size[4] Tattach tag[2] fid[4] afid[4] uname[s] aname[s]
+Rattach =>	H+QID,		# size[4] Rattach tag[2] qid[13]
+
+Twalk =>	H+FID+FID+LEN,	# size[4] Twalk tag[2] fid[4] newfid[4] nwname[2] nwname*(wname[s])
+Rwalk =>	H+LEN,		# size[4] Rwalk tag[2] nwqid[2] nwqid*(wqid[13])
+
+Topen =>	H+FID+BIT8SZ,		# size[4] Topen tag[2] fid[4] mode[1]
+Ropen =>	H+QID+COUNT,	# size[4] Ropen tag[2] qid[13] iounit[4]
+
+Tcreate =>	H+FID+STR+BIT32SZ+BIT8SZ,	# size[4] Tcreate tag[2] fid[4] name[s] perm[4] mode[1]
+Rcreate =>	H+QID+COUNT,	# size[4] Rcreate tag[2] qid[13] iounit[4]
+
+Tread =>	H+FID+OFFSET+COUNT,	# size[4] Tread tag[2] fid[4] offset[8] count[4]
+Rread =>	H+COUNT,		# size[4] Rread tag[2] count[4] data[count]
+
+Twrite =>	H+FID+OFFSET+COUNT,	# size[4] Twrite tag[2] fid[4] offset[8] count[4] data[count]
+Rwrite =>	H+COUNT,	# size[4] Rwrite tag[2] count[4]
+
+Tclunk =>	H+FID,	# size[4] Tclunk tag[2] fid[4]
+Rclunk =>	H,		# size[4] Rclunk tag[2]
+
+Tremove =>	H+FID,	# size[4] Tremove tag[2] fid[4]
+Rremove =>	H,	# size[4] Rremove tag[2]
+
+Tstat =>	H+FID,	# size[4] Tstat tag[2] fid[4]
+Rstat =>	H+LEN,	# size[4] Rstat tag[2] stat[n]
+
+Twstat =>	H+FID+LEN,	# size[4] Twstat tag[2] fid[4] stat[n]
+Rwstat =>	H,	# size[4] Rwstat tag[2]
+};
+
+init()
+{
+	sys = load Sys Sys->PATH;
+}
+
+utflen(s: string): int
+{
+	# the domain is 16-bit unicode only, which is all that Inferno now implements
+	n := l := len s;
+	for(i:=0; i<l; i++)
+		if((c := s[i]) > 16r7F){
+			n++;
+			if(c > 16r7FF)
+				n++;
+		}
+	return n;
+}
+
+packdirsize(d: Sys->Dir): int
+{
+	return STATFIXLEN+utflen(d.name)+utflen(d.uid)+utflen(d.gid)+utflen(d.muid);
+}
+
+packdir(f: Sys->Dir): array of byte
+{
+	ds := packdirsize(f);
+	a := array[ds] of byte;
+	# size[2]
+	a[0] = byte (ds-LEN);
+	a[1] = byte ((ds-LEN)>>8);
+	# type[2]
+	a[2] = byte f.dtype;
+	a[3] = byte (f.dtype>>8);
+	# dev[4]
+	a[4] = byte f.dev;
+	a[5] = byte (f.dev>>8);
+	a[6] = byte (f.dev>>16);
+	a[7] = byte (f.dev>>24);
+	# qid.type[1]
+	# qid.vers[4]
+	# qid.path[8]
+	pqid(a, 8, f.qid);
+	# mode[4]
+	a[21] = byte f.mode;
+	a[22] = byte (f.mode>>8);
+	a[23] = byte (f.mode>>16);
+	a[24] = byte (f.mode>>24);
+	# atime[4]
+	a[25] = byte f.atime;
+	a[26] = byte (f.atime>>8);
+	a[27] = byte (f.atime>>16);
+	a[28] = byte (f.atime>>24);
+	# mtime[4]
+	a[29] = byte f.mtime;
+	a[30] = byte (f.mtime>>8);
+	a[31] = byte (f.mtime>>16);
+	a[32] = byte (f.mtime>>24);
+	# length[8]
+	p64(a, 33, big f.length);
+	# name[s]
+	i := pstring(a, 33+BIT64SZ, f.name);
+	i = pstring(a, i, f.uid);
+	i = pstring(a, i, f.gid);
+	i = pstring(a, i, f.muid);
+	if(i != len a)
+		raise "assertion: Styx->packdir: bad count";	# can't happen unless packedsize is wrong
+	return a;
+}
+
+pqid(a: array of byte, o: int, q: Sys->Qid): int
+{
+	a[o] = byte q.qtype;
+	v := q.vers;
+	a[o+1] = byte v;
+	a[o+2] = byte (v>>8);
+	a[o+3] = byte (v>>16);
+	a[o+4] = byte (v>>24);
+	v = int q.path;
+	a[o+5] = byte v;
+	a[o+6] = byte (v>>8);
+	a[o+7] = byte (v>>16);
+	a[o+8] = byte (v>>24);
+	v = int (q.path >> 32);
+	a[o+9] = byte v;
+	a[o+10] = byte (v>>8);
+	a[o+11] = byte (v>>16);
+	a[o+12] = byte (v>>24);
+	return o+QID;
+}
+
+pstring(a: array of byte, o: int, s: string): int
+{
+	sa := array of byte s;	# could do conversion ourselves
+	n := len sa;
+	a[o] = byte n;
+	a[o+1] = byte (n>>8);
+	a[o+2:] = sa;
+	return o+LEN+n;
+}
+
+p32(a: array of byte, o: int, v: int): int
+{
+	a[o] = byte v;
+	a[o+1] = byte (v>>8);
+	a[o+2] = byte (v>>16);
+	a[o+3] = byte (v>>24);
+	return o+BIT32SZ;
+}
+
+p64(a: array of byte, o: int, b: big): int
+{
+	i := int b;
+	a[o] = byte i;
+	a[o+1] = byte (i>>8);
+	a[o+2] = byte (i>>16);
+	a[o+3] = byte (i>>24);
+	i = int (b>>32);
+	a[o+4] = byte i;
+	a[o+5] = byte (i>>8);
+	a[o+6] = byte (i>>16);
+	a[o+7] = byte (i>>24);
+	return o+BIT64SZ;
+}
+
+unpackdir(a: array of byte): (int, Sys->Dir)
+{
+	dir: Sys->Dir;
+
+	if(len a < STATFIXLEN)
+		return (0, dir);
+	# size[2]
+	sz := ((int a[1] << 8) | int a[0])+LEN;	# bytes this packed dir should occupy
+	if(len a < sz)
+		return (0, dir);
+	# type[2]
+	dir.dtype = (int a[3]<<8) | int a[2];
+	# dev[4]
+	dir.dev = (((((int a[7] << 8) | int a[6]) << 8) | int a[5]) << 8) | int a[4];
+	# qid.type[1]
+	# qid.vers[4]
+	# qid.path[8]
+	dir.qid = gqid(a, 8);
+	# mode[4]
+	dir.mode = (((((int a[24] << 8) | int a[23]) << 8) | int a[22]) << 8) | int a[21];
+	# atime[4]
+	dir.atime = (((((int a[28] << 8) | int a[27]) << 8) | int a[26]) << 8) | int a[25];
+	# mtime[4]
+	dir.mtime = (((((int a[32] << 8) | int a[31]) << 8) | int a[30]) << 8) | int a[29];
+	# length[8]
+	v0 := (((((int a[36] << 8) | int a[35]) << 8) | int a[34]) << 8) | int a[33];
+	v1 := (((((int a[40] << 8) | int a[39]) << 8) | int a[38]) << 8) | int a[37];
+	dir.length = (big v1 << 32) | (big v0 & 16rFFFFFFFF);
+	# name[s], uid[s], gid[s], muid[s]
+	i: int;
+	(dir.name, i) = gstring(a, 41);
+	(dir.uid, i) = gstring(a, i);
+	(dir.gid, i) = gstring(a, i);
+	(dir.muid, i) = gstring(a, i);
+	if(i != sz)
+		return (0, dir);
+	return (i, dir);
+}
+
+gqid(f: array of byte, i: int): Sys->Qid
+{
+	qtype := int f[i];
+	vers := (((((int f[i+4] << 8) | int f[i+3]) << 8) | int f[i+2]) << 8) | int f[i+1];
+	i += BIT8SZ+BIT32SZ;
+	path0 := (((((int f[i+3] << 8) | int f[i+2]) << 8) | int f[i+1]) << 8) | int f[i];
+	i += BIT32SZ;
+	path1 := (((((int f[i+3] << 8) | int f[i+2]) << 8) | int f[i+1]) << 8) | int f[i];
+	path := (big path1 << 32) | (big path0 & 16rFFFFFFFF);
+	return (path, vers, qtype);
+}
+
+g32(f: array of byte, i: int): int
+{
+	return (((((int f[i+3] << 8) | int f[i+2]) << 8) | int f[i+1]) << 8) | int f[i];
+}
+
+g64(f: array of byte, i: int): big
+{
+	b0 := (((((int f[i+3] << 8) | int f[i+2]) << 8) | int f[i+1]) << 8) | int f[i];
+	b1 := (((((int f[i+7] << 8) | int f[i+6]) << 8) | int f[i+5]) << 8) | int f[i+4];
+	return (big b1 << 32) | (big b0 & 16rFFFFFFFF);
+}
+
+gstring(a: array of byte, o: int): (string, int)
+{
+	if(o < 0 || o+STR > len a)
+		return (nil, -1);
+	l := (int a[o+1] << 8) | int a[o];
+	o += STR;
+	e := o+l;
+	if(e > len a)
+		return (nil, -1);
+	return (string a[o:e], e);
+}
+
+ttag2type := array[] of {
+tagof Tmsg.Readerror => 0,
+tagof Tmsg.Version => Tversion,
+tagof Tmsg.Auth => Tauth,
+tagof Tmsg.Attach => Tattach,
+tagof Tmsg.Flush => Tflush,
+tagof Tmsg.Walk => Twalk,
+tagof Tmsg.Open => Topen,
+tagof Tmsg.Create => Tcreate,
+tagof Tmsg.Read => Tread,
+tagof Tmsg.Write => Twrite,
+tagof Tmsg.Clunk => Tclunk,
+tagof Tmsg.Stat => Tstat,
+tagof Tmsg.Remove => Tremove,
+tagof Tmsg.Wstat => Twstat,
+};
+
+Tmsg.mtype(t: self ref Tmsg): int
+{
+	return ttag2type[tagof t];
+}
+
+Tmsg.packedsize(t: self ref Tmsg): int
+{
+	mtype := ttag2type[tagof t];
+	if(mtype <= 0)
+		return 0;
+	ml := hdrlen[mtype];
+	pick m := t {
+	Version =>
+		ml += utflen(m.version);
+	Auth =>
+		ml += utflen(m.uname)+utflen(m.aname);
+	Attach =>
+		ml += utflen(m.uname)+utflen(m.aname);
+	Walk =>
+		for(i:=0; i<len m.names; i++)
+			ml += STR+utflen(m.names[i]);
+	Create =>
+		ml += utflen(m.name);
+	Write =>
+		ml += len m.data;
+	Wstat =>
+		ml += packdirsize(m.stat);
+	}
+	return ml;
+}
+
+Tmsg.pack(t: self ref Tmsg): array of byte
+{
+	if(t == nil)
+		return nil;
+	ds := t.packedsize();
+	if(ds <= 0)
+		return nil;
+	d := array[ds] of byte;
+	d[0] = byte ds;
+	d[1] = byte (ds>>8);
+	d[2] = byte (ds>>16);
+	d[3] = byte (ds>>24);
+	d[4] = byte ttag2type[tagof t];
+	d[5] = byte t.tag;
+	d[6] = byte (t.tag >> 8);
+	pick m := t {
+	Version =>
+		p32(d, H, m.msize);
+		pstring(d, H+COUNT, m.version);
+	Auth =>
+		p32(d, H, m.afid);
+		o := pstring(d, H+FID, m.uname);
+		pstring(d, o, m.aname);
+	Flush =>
+		v := m.oldtag;
+		d[H] = byte v;
+		d[H+1] = byte (v>>8);
+	Attach =>
+		p32(d, H, m.fid);
+		p32(d, H+FID, m.afid);
+		o := pstring(d, H+2*FID, m.uname);
+		pstring(d, o, m.aname);
+	Walk =>
+		d[H] = byte m.fid;
+		d[H+1] = byte (m.fid>>8);
+		d[H+2] = byte (m.fid>>16);
+		d[H+3] = byte (m.fid>>24);
+		d[H+FID] = byte m.newfid;
+		d[H+FID+1] = byte (m.newfid>>8);
+		d[H+FID+2] = byte (m.newfid>>16);
+		d[H+FID+3] = byte (m.newfid>>24);
+		n := len m.names;
+		d[H+2*FID] = byte n;
+		d[H+2*FID+1] = byte (n>>8);
+		o := H+2*FID+LEN;
+		for(i := 0; i < n; i++)
+			o = pstring(d, o, m.names[i]);
+	Open =>
+		p32(d, H, m.fid);
+		d[H+FID] = byte m.mode;
+	Create =>
+		p32(d, H, m.fid);
+		o := pstring(d, H+FID, m.name);
+		p32(d, o, m.perm);
+		d[o+BIT32SZ] = byte m.mode;
+	Read =>
+		p32(d, H, m.fid);
+		p64(d, H+FID, m.offset);
+		p32(d, H+FID+OFFSET, m.count);
+	Write =>
+		p32(d, H, m.fid);
+		p64(d, H+FID, m.offset);
+		n := len m.data;
+		p32(d, H+FID+OFFSET, n);
+		d[H+FID+OFFSET+COUNT:] = m.data;
+	Clunk or Remove or Stat =>
+		p32(d, H, m.fid);
+	Wstat =>
+		p32(d, H, m.fid);
+		stat := packdir(m.stat);
+		n := len stat;
+		d[H+FID] = byte n;
+		d[H+FID+1] = byte (n>>8);
+		d[H+FID+LEN:] = stat;
+	* =>
+		raise sys->sprint("assertion: Styx->Tmsg.pack: bad tag: %d", tagof t);
+	}
+	return d;
+}
+
+Tmsg.unpack(f: array of byte): (int, ref Tmsg)
+{
+	if(len f < H)
+		return (0, nil);
+	size := (int f[1] << 8) | int f[0];
+	size |= ((int f[3] << 8) | int f[2]) << 16;
+	if(len f != size){
+		if(len f < size)
+			return (0, nil);	# need more data
+		f = f[0:size];	# trim to exact length
+	}
+	mtype := int f[4];
+	if(mtype >= len hdrlen || (mtype&1) != 0 || size < hdrlen[mtype])
+		return (-1, nil);
+
+	tag := (int f[6] << 8) | int f[5];
+	fid := 0;
+	if(hdrlen[mtype] >= H+FID)
+		fid = g32(f, H);	# fid is always in same place: extract it once for all if there
+
+	# return out of each case body for a legal message;
+	# break out of the case for an illegal one
+
+Decode:
+	case mtype {
+	* =>
+		sys->print("styx: Tmsg.unpack: bad type %d\n", mtype);
+	Tversion =>
+		msize := fid;
+		(version, o) := gstring(f, H+COUNT);
+		if(o <= 0)
+			break;
+		return (o, ref Tmsg.Version(tag, msize, version));
+	Tauth =>
+		(uname, o1) := gstring(f, H+FID);
+		(aname, o2) := gstring(f, o1);
+		if(o2 <= 0)
+			break;
+		return (o2, ref Tmsg.Auth(tag, fid, uname, aname));
+	Tflush =>
+		oldtag := (int f[H+1] << 8) | int f[H];
+		return (H+TAG, ref Tmsg.Flush(tag, oldtag));
+	Tattach =>
+		afid := g32(f, H+FID);
+		(uname, o1) := gstring(f, H+2*FID);
+		(aname, o2) := gstring(f, o1);
+		if(o2 <= 0)
+			break;
+		return (o2, ref Tmsg.Attach(tag, fid, afid, uname, aname));
+	Twalk =>
+		newfid := g32(f, H+FID);
+		n := (int f[H+2*FID+1] << 8) | int f[H+2*FID];
+		if(n > MAXWELEM)
+			break;
+		o := H+2*FID+LEN;
+		names: array of string = nil;
+		if(n > 0){
+			names = array[n] of string;
+			for(i:=0; i<n; i++){
+				(names[i], o) = gstring(f, o);
+				if(o <= 0)
+					break Decode;
+			}
+		}
+		return (o, ref Tmsg.Walk(tag, fid, newfid, names));
+	Topen =>
+		return (H+FID+BIT8SZ, ref Tmsg.Open(tag, fid, int f[H+FID]));
+	Tcreate =>
+		(name, o) := gstring(f, H+FID);
+		if(o <= 0 || o+BIT32SZ+BIT8SZ > len f)
+			break;
+		perm := g32(f, o);
+		o += BIT32SZ;
+		mode := int f[o++];
+		return (o, ref Tmsg.Create(tag, fid, name, perm, mode));
+	Tread =>
+		offset := g64(f, H+FID);
+		count := g32(f, H+FID+OFFSET);
+		return (H+FID+OFFSET+COUNT, ref Tmsg.Read(tag, fid, offset, count));
+	Twrite =>
+		offset := g64(f, H+FID);
+		count := g32(f, H+FID+OFFSET);
+		O: con H+FID+OFFSET+COUNT;
+		if(count > len f-O)
+			break;
+		data := f[O:O+count];
+		return (O+count, ref Tmsg.Write(tag, fid, offset, data));
+	Tclunk =>
+		return (H+FID, ref Tmsg.Clunk(tag, fid));
+	Tremove =>
+		return (H+FID, ref Tmsg.Remove(tag, fid));
+	Tstat =>
+		return (H+FID, ref Tmsg.Stat(tag, fid));
+	Twstat =>
+		n := int (f[H+FID+1]<<8) | int f[H+FID];
+		if(len f < H+FID+LEN+n)
+			break;
+		(ds, stat) := unpackdir(f[H+FID+LEN:]);
+		if(ds != n){
+			sys->print("Styx->Tmsg.unpack: wstat count: %d/%d\n", ds, n);	# temporary
+			break;
+		}
+		return (H+FID+LEN+n, ref Tmsg.Wstat(tag, fid, stat));
+	}
+	return (-1, nil);		# illegal
+}
+
+tmsgname := array[] of {
+tagof Tmsg.Readerror => "Readerror",
+tagof Tmsg.Version => "Version",
+tagof Tmsg.Auth => "Auth",
+tagof Tmsg.Attach => "Attach",
+tagof Tmsg.Flush => "Flush",
+tagof Tmsg.Walk => "Walk",
+tagof Tmsg.Open => "Open",
+tagof Tmsg.Create => "Create",
+tagof Tmsg.Read => "Read",
+tagof Tmsg.Write => "Write",
+tagof Tmsg.Clunk => "Clunk",
+tagof Tmsg.Stat => "Stat",
+tagof Tmsg.Remove => "Remove",
+tagof Tmsg.Wstat => "Wstat",
+};
+
+Tmsg.text(t: self ref Tmsg): string
+{
+	if(t == nil)
+		return "nil";
+	s := sys->sprint("Tmsg.%s(%ud", tmsgname[tagof t], t.tag);
+	pick m:= t {
+	* =>
+		return s + ",ILLEGAL)";
+	Readerror =>
+		return s + sys->sprint(",\"%s\")", m.error);
+	Version =>
+		return s + sys->sprint(",%d,\"%s\")", m.msize, m.version);
+	Auth =>
+		return s + sys->sprint(",%ud,\"%s\",\"%s\")", m.afid, m.uname, m.aname);
+	Flush =>
+		return s + sys->sprint(",%ud)", m.oldtag);
+	Attach =>
+		return s + sys->sprint(",%ud,%ud,\"%s\",\"%s\")", m.fid, m.afid, m.uname, m.aname);
+	Walk =>
+		s += sys->sprint(",%ud,%ud", m.fid, m.newfid);
+		if(len m.names != 0){
+			s += ",array[] of {";
+			for(i := 0; i < len m.names; i++){
+				c := ",";
+				if(i == 0)
+					c = "";
+				s += sys->sprint("%s\"%s\"", c, m.names[i]);
+			}
+			s += "}";
+		}else
+			s += ",nil";
+		return s + ")";
+	Open =>
+		return s + sys->sprint(",%ud,%d)", m.fid, m.mode);
+	Create =>
+		return s + sys->sprint(",%ud,\"%s\",8r%uo,%d)", m.fid, m.name, m.perm, m.mode);
+	Read =>
+		return s + sys->sprint(",%ud,%bd,%ud)", m.fid, m.offset, m.count);
+	Write =>
+		return s + sys->sprint(",%ud,%bd,array[%d] of byte)", m.fid, m.offset, len m.data);
+	Clunk or
+	Remove or
+	Stat =>
+		return s + sys->sprint(",%ud)", m.fid);
+	Wstat =>
+		return s + sys->sprint(",%ud,%s)", m.fid, dir2text(m.stat));
+	}
+}
+
+Tmsg.read(fd: ref Sys->FD, msglim: int): ref Tmsg
+{
+	(msg, err) := readmsg(fd, msglim);
+	if(err != nil)
+		return ref Tmsg.Readerror(0, err);
+	if(msg == nil)
+		return nil;
+	(nil, m) := Tmsg.unpack(msg);
+	if(m == nil)
+		return ref Tmsg.Readerror(0, "bad Styx T-message format");
+	return m;
+}
+
+rtag2type := array[] of {
+tagof Rmsg.Version	=> Rversion,
+tagof Rmsg.Auth	=> Rauth,
+tagof Rmsg.Error	=> Rerror,
+tagof Rmsg.Flush	=> Rflush,
+tagof Rmsg.Attach	=> Rattach,
+tagof Rmsg.Walk	=> Rwalk,
+tagof Rmsg.Open	=> Ropen,
+tagof Rmsg.Create	=> Rcreate,
+tagof Rmsg.Read	=> Rread,
+tagof Rmsg.Write	=> Rwrite,
+tagof Rmsg.Clunk	=> Rclunk,
+tagof Rmsg.Remove	=> Rremove,
+tagof Rmsg.Stat	=> Rstat,
+tagof Rmsg.Wstat	=> Rwstat,
+};
+
+Rmsg.mtype(r: self ref Rmsg): int
+{
+	return rtag2type[tagof r];
+}
+
+Rmsg.packedsize(r: self ref Rmsg): int
+{
+	mtype := rtag2type[tagof r];
+	if(mtype <= 0)
+		return 0;
+	ml := hdrlen[mtype];
+	pick m := r {
+	Version =>
+		ml += utflen(m.version);
+	Error =>
+		ml += utflen(m.ename);
+	Walk =>
+		ml += QID*len m.qids;
+	Read =>
+		ml += len m.data;
+	Stat =>
+		ml += packdirsize(m.stat);
+	}
+	return ml;
+}
+
+Rmsg.pack(r: self ref Rmsg): array of byte
+{
+	if(r == nil)
+		return nil;
+	ps := r.packedsize();
+	if(ps <= 0)
+		return nil;
+	d := array[ps] of byte;
+	d[0] = byte ps;
+	d[1] = byte (ps>>8);
+	d[2] = byte (ps>>16);
+	d[3] = byte (ps>>24);
+	d[4] = byte rtag2type[tagof r];
+	d[5] = byte r.tag;
+	d[6] = byte (r.tag >> 8);
+	pick m := r {
+	Version =>
+		p32(d, H, m.msize);
+		pstring(d, H+BIT32SZ, m.version);
+	Auth =>
+		pqid(d, H, m.aqid);
+	Flush or
+	Clunk or
+	Remove or
+	Wstat =>
+		;	# nothing more required
+	Error	=>
+		pstring(d, H, m.ename);
+	Attach =>
+		pqid(d, H, m.qid);
+	Walk =>
+		n := len m.qids;
+		d[H] = byte n;
+		d[H+1] = byte (n>>8);
+		o := H+LEN;
+		for(i:=0; i<n; i++){
+			pqid(d, o, m.qids[i]);
+			o += QID;
+		}
+	Create or
+	Open =>
+		pqid(d, H, m.qid);
+		p32(d, H+QID, m.iounit);
+	Read =>
+		v := len m.data;
+		d[H] = byte v;
+		d[H+1] = byte (v>>8);
+		d[H+2] = byte (v>>16);
+		d[H+3] = byte (v>>24);
+		d[H+4:] = m.data;
+	Write =>
+		v := m.count;
+		d[H] = byte v;
+		d[H+1] = byte (v>>8);
+		d[H+2] = byte (v>>16);
+		d[H+3] = byte (v>>24);
+	Stat =>
+		stat := packdir(m.stat);
+		v := len stat;
+		d[H] = byte v;
+		d[H+1] = byte (v>>8);
+		d[H+2:] = stat;		# should avoid copy?
+	* =>
+		raise sys->sprint("assertion: Styx->Rmsg.pack: missed case: tag %d", tagof r);
+	}
+	return d;
+}
+
+Rmsg.unpack(f: array of byte): (int, ref Rmsg)
+{
+	if(len f < H)
+		return (0, nil);
+	size := (int f[1] << 8) | int f[0];
+	size |= ((int f[3] << 8) | int f[2]) << 16;	# size includes itself
+	if(len f != size){
+		if(len f < size)
+			return (0, nil);	# need more data
+		f = f[0:size];	# trim to exact length
+	}
+	mtype := int f[4];
+	if(mtype >= len hdrlen || (mtype&1) == 0 || size < hdrlen[mtype])
+		return (-1, nil);
+
+	tag := (int f[6] << 8) | int f[5];
+
+	# return out of each case body for a legal message;
+	# break out of the case for an illegal one
+
+	case mtype {
+	* =>
+		sys->print("Styx->Rmsg.unpack: bad type %d\n", mtype);	# temporary
+	Rversion =>
+		msize := g32(f, H);
+		(version, o) := gstring(f, H+BIT32SZ);
+		if(o <= 0)
+			break;
+		return (o, ref Rmsg.Version(tag, msize, version));
+	Rauth =>
+		return (H+QID, ref Rmsg.Auth(tag, gqid(f, H)));
+	Rflush =>
+		return (H, ref Rmsg.Flush(tag));
+	Rerror =>
+		(ename, o) := gstring(f, H);
+		if(o <= 0)
+			break;
+		return (o, ref Rmsg.Error(tag, ename));
+	Rclunk =>
+		return (H, ref Rmsg.Clunk(tag));
+	Rremove =>
+		return (H, ref Rmsg.Remove(tag));
+	Rwstat=>
+		return (H, ref Rmsg.Wstat(tag));
+	Rattach =>
+		return (H+QID, ref Rmsg.Attach(tag, gqid(f, H)));
+	Rwalk =>
+		nqid := (int f[H+1] << 8) | int f[H];
+		if(len f < H+LEN+nqid*QID)
+			break;
+		o := H+LEN;
+		qids := array[nqid] of Sys->Qid;
+		for(i:=0; i<nqid; i++){
+			qids[i] = gqid(f, o);
+			o += QID;
+		}
+		return (o, ref Rmsg.Walk(tag, qids));
+	Ropen =>
+		return (H+QID+COUNT, ref Rmsg.Open(tag, gqid(f, H), g32(f, H+QID)));
+	Rcreate=>
+		return (H+QID+COUNT, ref Rmsg.Create(tag, gqid(f, H), g32(f, H+QID)));
+	Rread =>
+		count := g32(f, H);
+		if(len f < H+COUNT+count)
+			break;
+		data := f[H+COUNT:H+COUNT+count];
+		return (H+COUNT+count, ref Rmsg.Read(tag, data));
+	Rwrite =>
+		return (H+COUNT, ref Rmsg.Write(tag, g32(f, H)));
+	Rstat =>
+		n := (int f[H+1] << 8) | int f[H];
+		if(len f < H+LEN+n)
+			break;
+		(ds, d) := unpackdir(f[H+LEN:]);
+		if(ds <= 0)
+			break;
+		if(ds != n){
+			sys->print("Styx->Rmsg.unpack: stat count: %d/%d\n", ds, n);		# temporary
+			break;
+		}
+		return (H+LEN+n, ref Rmsg.Stat(tag, d));
+	}
+	return (-1, nil);		# illegal
+}
+
+rmsgname := array[] of {
+tagof Rmsg.Version => "Version",
+tagof Rmsg.Auth => "Auth",
+tagof Rmsg.Attach => "Attach",
+tagof Rmsg.Error => "Error",
+tagof Rmsg.Flush => "Flush",
+tagof Rmsg.Walk => "Walk",
+tagof Rmsg.Create => "Create",
+tagof Rmsg.Open => "Open",
+tagof Rmsg.Read => "Read",
+tagof Rmsg.Write => "Write",
+tagof Rmsg.Clunk => "Clunk",
+tagof Rmsg.Remove => "Remove",
+tagof Rmsg.Stat => "Stat",
+tagof Rmsg.Wstat => "Wstat",
+};
+
+Rmsg.text(r: self ref Rmsg): string
+{
+	if(sys == nil)
+		sys = load Sys Sys->PATH;
+	if(r == nil)
+		return "nil";
+	s := sys->sprint("Rmsg.%s(%ud", rmsgname[tagof r], r.tag);
+	pick m := r {
+	* =>
+		return s + "ERROR)";
+	Readerror =>
+		return s + sys->sprint(",\"%s\")", m.error);
+	Version =>
+		return s + sys->sprint(",%d,\"%s\")", m.msize, m.version);
+	Auth =>
+		return s+sys->sprint(",%s)", qid2text(m.aqid));
+	Error =>
+		return s+sys->sprint(",\"%s\")", m.ename);
+	Flush or
+	Clunk or
+	Remove or
+	Wstat =>
+		return s+")";
+	Attach =>
+		return s+sys->sprint(",%s)", qid2text(m.qid));
+	Walk	 =>
+		s += ",array[] of {";
+		for(i := 0; i < len m.qids; i++){
+			c := "";
+			if(i != 0)
+				c = ",";
+			s += sys->sprint("%s%s", c, qid2text(m.qids[i]));
+		}
+		return s+"})";
+	Create or
+	Open =>
+		return s+sys->sprint(",%s,%d)", qid2text(m.qid), m.iounit);
+	Read =>
+		return s+sys->sprint(",array[%d] of byte)", len m.data);
+	Write =>
+		return s+sys->sprint(",%d)", m.count);
+	Stat =>
+		return s+sys->sprint(",%s)", dir2text(m.stat));
+	}
+}
+
+Rmsg.read(fd: ref Sys->FD, msglim: int): ref Rmsg
+{
+	(msg, err) := readmsg(fd, msglim);
+	if(err != nil)
+		return ref Rmsg.Readerror(0, err);
+	if(msg == nil)
+		return nil;
+	(nil, m) := Rmsg.unpack(msg);
+	if(m == nil)
+		return ref Rmsg.Readerror(0, "bad Styx R-message format");
+	return m;
+}
+
+dir2text(d: Sys->Dir): string
+{
+	return sys->sprint("Dir(\"%s\",\"%s\",\"%s\",%s,8r%uo,%d,%d,%bd,16r%ux,%d)",
+		d.name, d.uid, d.gid, qid2text(d.qid), d.mode, d.atime, d.mtime, d.length, d.dtype, d.dev);
+}
+
+qid2text(q: Sys->Qid): string
+{
+	return sys->sprint("Qid(16r%ubx,%d,16r%.2ux)", q.path, q.vers, q.qtype);
+}
+
+readmsg(fd: ref Sys->FD, msglim: int): (array of byte, string)
+{
+	if(msglim <= 0)
+		msglim = MAXRPC;
+	sbuf := array[BIT32SZ] of byte;
+	if((n := readn(fd, sbuf, BIT32SZ)) != BIT32SZ){
+		if(n == 0)
+			return (nil, nil);
+		return (nil, sys->sprint("%r"));
+	}
+	ml := (int sbuf[1] << 8) | int sbuf[0];
+	ml |= ((int sbuf[3] << 8) | int sbuf[2]) << 16;
+	if(ml <= BIT32SZ)
+		return (nil, "invalid Styx message size");
+	if(ml > msglim)
+		return (nil, "Styx message longer than agreed");
+	buf := array[ml] of byte;
+	buf[0:] = sbuf;
+	if((n = readn(fd, buf[BIT32SZ:], ml-BIT32SZ)) != ml-BIT32SZ){
+		if(n == 0)
+			return (nil, "Styx message truncated");
+		return (nil, sys->sprint("%r"));
+	}
+	return (buf, nil);
+}
+
+readn(fd: ref Sys->FD, buf: array of byte, nb: int): int
+{
+	for(nr := 0; nr < nb;){
+		n := sys->read(fd, buf[nr:], nb-nr);
+		if(n <= 0){
+			if(nr == 0)
+				return n;
+			break;
+		}
+		nr += n;
+	}
+	return nr;
+}
+
+istmsg(f: array of byte): int
+{
+	if(len f < H)
+		return -1;
+	return (int f[BIT32SZ] & 1) == 0;
+}
+
+compatible(t: ref Tmsg.Version, msize: int, version: string): (int, string)
+{
+	if(version == nil)
+		version = VERSION;
+	if(t.msize < msize)
+		msize = t.msize;
+	v := t.version;
+	if(len v < 2 || v[0:2] != "9P")
+		return (msize, "unknown");
+	for(i:=2; i<len v; i++)
+		if((c := v[i]) == '.'){
+			v = v[0:i];
+			break;
+		}else if(!(c >= '0' && c <= '9'))
+			return (msize, "unknown");	# fussier than Plan 9
+	if(v < VERSION)
+		return (msize, "unknown");
+	if(v < version)
+		version = v;
+	return (msize, version);
+}
+
+# only here to support an implementation of this module that talks the previous version of Styx
+write(fd: ref Sys->FD, buf: array of byte, nb: int): int
+{
+	return sys->write(fd, buf, nb);
+}