code: 9ferno

ref: 0977f294bab0345ba43fbf674449fd8e996c5719
dir: /man/2/styxservers-nametree/

.TH STYXSERVERS-NAMETREE 2
.SH NAME
Styxservers: nametree \-
hierarchical name storage for use with Styxservers.
.SH SYNOPSIS
.EX
include "sys.m";
include "styx.m";
include "styxservers.m";
nametree := load Nametree Nametree->PATH;
	Tree: import nametree;

Tree: adt {
    create: fn(t: self ref Tree, parentpath: big, d: Sys->Dir): string;
    remove: fn(t: self ref Tree, path: big): string;
    wstat:   fn(t: self ref Tree, path: big, d: Sys->Dir);
    quit:   fn(t: self ref Tree);
};
init:       fn();
start:      fn(): (ref Tree, chan of ref Styxservers->Navop);
.EE
.SH DESCRIPTION
.B Nametree
provides the storage for a hierarchical namespace
to be used by
.IR styxservers (2).
After the module is loaded, the
.B init
function should be called to
initialise the module's internal variables.
.B Start
spawns a new
.B nametree
process; it returns a tuple, say
.RI ( tree ,\  c ),
where c is a channel that can be used to create
an instance of
.BR Styxservers->Navigator ,
to access files inside
.BR nametree ,
and
.I tree
is an adt that allows creation and removal of those files.
On failure, these functions return a string describing
the error.
.PP
Note that the full set of operations on
.B Nametree
(i.e. stat, walk, readdir, wstate, create and remove),
is only available in conjunction with
.BR Styxserver 's
.B Navigator
interface.
Files in the name space are ultimately identified by a 64-bit
.I path
value, which forms the path component of the file's Qid.
(See
.IR intro (5)
for a description of the system's interpretation of Qids.)
.PP
The
.B Tree
operations
are:
.TP 10
.IB t .create(\fIparentpath\fP,\ \fId\fP)
Create a new file or directory.
.I D
gives the directory information that will be stored
for the file, including its own path value,
given by
.IB d .qid.path .
If the file referenced by
.I parentpath
does not exist, creation will not be allowed,
other than in the special case when
.IB d .qid.path
is equal to
.IR parentpath ,
in which case it is assumed to be a root directory
and may be created. This potentially allows a single
.B Nametree
instance to hold many distinct directory hierarchies.
Note that no attempt is made to ensure that
.I parentpath
refers to a directory; the check is assumed to have
been made previously.
When a hierarchy is traversed,
.B Nametree
interprets the name
.RB ` .. '
itself as `parent directory', and that name should not be created explicitly.
.TP
.IB t .remove(\fIpath\fP)
Remove the file referred to by
.IR path ,
and all its descendants.
.TP
.IB t .wstat(\fIpath\fP,\ \fId\fP)
Change the directory information held on file
.IR path .
The Qid path itself cannot be changed by
.IR d .
.TP
.IB t .quit()
Shut down the
.B nametree
process.
.SH EXAMPLE
Here is a complete example that uses
.B Nametree
in conjunction with
.B Styxservers
in order to serve two files
.B data
and
.BR ctl " ..."
and do nothing with them:
.EX
implement Tst;
include "sys.m";
	sys: Sys;
include "draw.m";
include "styx.m";
include "styxservers.m";
	styxservers: Styxservers;
	Styxserver, Navigator: import styxservers;
	nametree: Nametree;
	Tree: import nametree;

Tst: module
{
	init: fn(nil: ref Draw->Context, argv: list of string);
};

Qroot, Qctl, Qdata: con big iota;	# paths
init(nil: ref Draw->Context, args: list of string)
{
	sys = load Sys Sys->PATH;
	styx := load Styx Styx->PATH;
	styx->init();
	styxservers = load Styxservers Styxservers->PATH;
	styxservers->init(styx);
	nametree = load Nametree Nametree->PATH;
	nametree->init();
	sys->pctl(Sys->FORKNS, nil);
	(tree, treeop) := nametree->start();
	tree.create(Qroot, dir(".", 8r555|Sys->DMDIR, Qroot));
	tree.create(Qroot, dir("ctl", 8r666, Qctl));
	tree.create(Qroot, dir("data", 8r444, Qdata));
	(tchan, srv) := Styxserver.new(sys->fildes(0),
						Navigator.new(treeop), Qroot);
	while((gm := <-tchan) != nil) {
		# normally a pick on gm would act on
		# Tmsg.Read and Tmsg.Write at least
		srv.default(gm);
	}
	tree.quit();
}

dir(name: string, perm: int, qid: big): Sys->Dir
{
	d := sys->zerodir;
	d.name = name;
	d.uid = "me";
	d.gid = "me";
	d.qid.path = qid;
	if (perm & Sys->DMDIR)
		d.qid.qtype = Sys->QTDIR;
	else
		d.qid.qtype = Sys->QTFILE;
	d.mode = perm;
	return d;
}
.EE
.SH SOURCE
.B /appl/lib/nametree.b
.SH SEE ALSO
.IR styxservers (2),
.IR intro (5)