NAME

Styxservers: nametree - hierarchical name storage for use with Styxservers.

SYNOPSIS

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);

DESCRIPTION

Nametree provides the storage for a hierarchical namespace to be used by styxservers(2). After the module is loaded, the init function should be called to initialise the module's internal variables. Start spawns a new nametree process; it returns a tuple, say (tree, c), where c is a channel that can be used to create an instance of Styxservers->Navigator, to access files inside nametree, and tree is an adt that allows creation and removal of those files. On failure, these functions return a string describing the error.

Note that the full set of operations on Nametree (i.e. stat, walk, readdir, wstate, create and remove), is only available in conjunction with Styxserver's Navigator interface. Files in the name space are ultimately identified by a 64-bit path value, which forms the path component of the file's Qid. (See intro(5) for a description of the system's interpretation of Qids.)

The Tree operations are:

t.create(parentpath, d)

Create a new file or directory. D gives the directory information that will be stored for the file, including its own path value, given by d.qid.path. If the file referenced by parentpath does not exist, creation will not be allowed, other than in the special case when d.qid.path is equal to parentpath, in which case it is assumed to be a root directory and may be created. This potentially allows a single Nametree instance to hold many distinct directory hierarchies. Note that no attempt is made to ensure that parentpath refers to a directory; the check is assumed to have been made previously. When a hierarchy is traversed, Nametree interprets the name `..' itself as `parent directory', and that name should not be created explicitly.

t.remove(path)

Remove the file referred to by path, and all its descendants.

t.wstat(path, d)

Change the directory information held on file path. The Qid path itself cannot be changed by d.

t.quit()

Shut down the nametree process.

EXAMPLE

Here is a complete example that uses Nametree in conjunction with Styxservers in order to serve two files data and ctl ... and do nothing with them:

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;
}

SOURCE

/appl/lib/nametree.b

SEE ALSO

styxservers(2), intro(5)

STYXSERVERS-NAMETREE(2 )

Rev:  Tue Mar 31 02:42:39 GMT 2015