STYXSERVERS-NAMETREE(2) STYXSERVERS-NAMETREE(2)
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 describ-
ing 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 interpreta-
tion 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
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STYXSERVERS-NAMETREE(2) STYXSERVERS-NAMETREE(2)
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();
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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)
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