ref: c116550e6a41572796e4db65e4f6acbcb3d9d6f8
dir: /appl/lib/nametree.b/
implement Nametree;
include "sys.m";
sys: Sys;
include "styx.m";
include "styxservers.m";
Navop: import Styxservers;
Enotfound, Eexists: import Styxservers;
Fholder: adt {
parentqid: big;
d: Sys->Dir;
child: cyclic ref Fholder;
sibling: cyclic ref Fholder;
hash: cyclic ref Fholder;
};
init()
{
sys = load Sys Sys->PATH;
}
start(): (ref Tree, chan of ref Styxservers->Navop)
{
fs := ref Tree(chan of ref Treeop, chan of string);
c := chan of ref Styxservers->Navop;
spawn fsproc(c, fs.c);
return (fs, c);
}
Tree.quit(t: self ref Tree)
{
t.c <-= nil;
}
Tree.create(t: self ref Tree, parentq: big, d: Sys->Dir): string
{
t.c <-= ref Treeop.Create(t.reply, parentq, d);
return <-t.reply;
}
Tree.remove(t: self ref Tree, q: big): string
{
t.c <-= ref Treeop.Remove(t.reply, q);
return <-t.reply;
}
Tree.wstat(t: self ref Tree, q: big, d: Sys->Dir): string
{
t.c <-= ref Treeop.Wstat(t.reply, q, d);
return <-t.reply;
}
Tree.getpath(t: self ref Tree, q: big): string
{
t. c <-= ref Treeop.Getpath(t.reply, q);
return <-t.reply;
}
fsproc(c: chan of ref Styxservers->Navop, fsc: chan of ref Treeop)
{
tab := array[23] of ref Fholder;
for (;;) alt {
grq := <-c =>
if (grq == nil)
exit;
(q, reply) := (grq.path, grq.reply);
fh := findfile(tab, q);
if (fh == nil) {
reply <-= (nil, Enotfound);
continue;
}
pick rq := grq {
Stat =>
reply <-= (ref fh.d, nil);
Walk =>
d := fswalk(tab, fh, rq.name);
if (d == nil)
reply <-= (nil, Enotfound);
else
reply <-= (d, nil);
Readdir =>
(start, end) := (rq.offset, rq.offset + rq.count);
fh = fh.child;
for (i := 0; i < end && fh != nil; i++) {
if (i >= start)
reply <-= (ref fh.d, nil);
fh = fh.sibling;
}
reply <-= (nil, nil);
* =>
panic(sys->sprint("unknown op %d\n", tagof(grq)));
}
grq := <-fsc =>
if (grq == nil)
exit;
(q, reply) := (grq.q, grq.reply);
pick rq := grq {
Create =>
reply <-= fscreate(tab, q, rq.d);
Remove =>
reply <-= fsremove(tab, q);
Wstat =>
reply <-= fswstat(tab, q, rq.d);
Getpath =>
reply <-= fsgetpath(tab, q);
* =>
panic(sys->sprint("unknown fs op %d\n", tagof(grq)));
}
}
}
hashfn(q: big, n: int): int
{
h := int (q % big n);
if (h < 0)
h += n;
return h;
}
findfile(tab: array of ref Fholder, q: big): ref Fholder
{
for (fh := tab[hashfn(q, len tab)]; fh != nil; fh = fh.hash)
if (fh.d.qid.path == q)
return fh;
return nil;
}
fsgetpath(tab: array of ref Fholder, q: big): string
{
fh := findfile(tab, q);
if (fh == nil)
return nil;
s := fh.d.name;
while (fh.parentqid != fh.d.qid.path) {
fh = findfile(tab, fh.parentqid);
if (fh == nil)
return nil;
s = fh.d.name + "/" + s;
}
return s;
}
fswalk(tab: array of ref Fholder, fh: ref Fholder, name: string): ref Sys->Dir
{
if (name == "..")
return ref findfile(tab, fh.parentqid).d;
for (fh = fh.child; fh != nil; fh = fh.sibling)
if (fh.d.name == name)
return ref fh.d;
return nil;
}
fsremove(tab: array of ref Fholder, q: big): string
{
prev: ref Fholder;
# remove from hash table
slot := hashfn(q, len tab);
for (fh := tab[slot]; fh != nil; fh = fh.hash) {
if (fh.d.qid.path == q)
break;
prev = fh;
}
if (fh == nil)
return Enotfound;
if (prev == nil)
tab[slot] = fh.hash;
else
prev.hash = fh.hash;
fh.hash = nil;
# remove from parent's children
parent := findfile(tab, fh.parentqid);
if (parent != nil) {
prev = nil;
for (sfh := parent.child; sfh != nil; sfh = sfh.sibling) {
if (sfh == fh)
break;
prev = sfh;
}
if (sfh == nil)
panic("child not found in parent");
if (prev == nil)
parent.child = fh.sibling;
else
prev.sibling = fh.sibling;
}
fh.sibling = nil;
# now remove any descendents
sibling: ref Fholder;
for (sfh := fh.child; sfh != nil; sfh = sibling) {
sibling = sfh.sibling;
sfh.parentqid = sfh.d.qid.path; # make sure it doesn't disrupt things.
fsremove(tab, sfh.d.qid.path);
}
return nil;
}
fscreate(tab: array of ref Fholder, q: big, d: Sys->Dir): string
{
parent := findfile(tab, q);
if (findfile(tab, d.qid.path) != nil)
return Eexists;
# allow creation of a root directory only if its parent is itself
if (parent == nil && d.qid.path != q)
return Enotfound;
fh: ref Fholder;
if (parent == nil)
fh = ref Fholder(q, d, nil, nil, nil);
else {
if (fswalk(tab, parent, d.name) != nil)
return Eexists;
fh = ref Fholder(parent.d.qid.path, d, nil, nil, nil);
fh.sibling = parent.child;
parent.child = fh;
}
slot := hashfn(d.qid.path, len tab);
fh.hash = tab[slot];
tab[slot] = fh;
return nil;
}
fswstat(tab: array of ref Fholder, q: big, d: Sys->Dir): string
{
fh := findfile(tab, q);
if (fh == nil)
return Enotfound;
d = applydir(d, fh.d);
# if renaming a file, check for duplicates
if (d.name != fh.d.name) {
parent := findfile(tab, fh.parentqid);
if (parent != nil && parent != fh && fswalk(tab, parent, d.name) != nil)
return Eexists;
}
fh.d = d;
fh.d.qid.path = q; # ensure the qid can't be changed
return nil;
}
applydir(d: Sys->Dir, onto: Sys->Dir): Sys->Dir
{
if (d.name != nil)
onto.name = d.name;
if (d.uid != nil)
onto.uid = d.uid;
if (d.gid != nil)
onto.gid = d.gid;
if (d.muid != nil)
onto.muid = d.muid;
if (d.qid.vers != ~0)
onto.qid.vers = d.qid.vers;
if (d.qid.qtype != ~0)
onto.qid.qtype = d.qid.qtype;
if (d.mode != ~0)
onto.mode = d.mode;
if (d.atime != ~0)
onto.atime = d.atime;
if (d.mtime != ~0)
onto.mtime = d.mtime;
if (d.length != ~big 0)
onto.length = d.length;
if (d.dtype != ~0)
onto.dtype = d.dtype;
if (d.dev != ~0)
onto.dev = d.dev;
return onto;
}
panic(s: string)
{
sys->fprint(sys->fildes(2), "panic: %s\n", s);
raise "panic";
}