// walkTo handles the walking logic. Walk returns a fidState, len(names) qids
// and a nil error if the walk succeeded. If the walk was partially successful,
// it returns a nil fidState, less than len(names) qids and a nil error. If the
// walk was completely unsuccessful, a nil fidState, nil qid slice and a non-nil
// error is returned.
func walkTo(oldState *fidState, names []string) (*fidState, []qp.Qid, error) {
var (
handle trees.ReadWriteAtCloser
isdir, addToLoc bool
root, temproot trees.File
username, name string
newloc FilePath
qids []qp.Qid
d trees.Dir
err error
q qp.Qid
)
// Walk and Arrived can block, so we don't want to be holding locks. Copy
// what we need.
oldState.RLock()
handle = oldState.handle
newloc = oldState.location.Clone()
username = oldState.username
oldState.RUnlock()
root = newloc.Current()
if root == nil {
return nil, nil, errors.New(InvalidOpOnFid)
}
if handle != nil {
// Can't walk on an open fid.
return nil, nil, errors.New(FidOpen)
}
for i := range names {
addToLoc = false
name = names[i]
switch name {
case ".":
// This always succeeds, but we don't want to add it to our location
// list.
case "..":
// This also always succeeds, and it either does nothing or shortens
// our location list. We don't want anything added to the list
// regardless.
root = newloc.Parent()
if len(newloc) > 1 {
newloc = newloc[:len(newloc)-1]
}
default:
// A regular file name. In this case, walking to the name is only
// legal if the current file is a directory.
addToLoc = true
isdir, err = root.IsDir()
if err != nil {
return nil, nil, err
}
if !isdir {
// Root isn't a dir, so we can't walk.
err = errors.New(FidNotDirectory)
goto done
}
d = root.(trees.Dir)
if root, err = d.Walk(username, name); err != nil {
// The walk failed for some arbitrary reason.
goto done
} else if root == nil {
// The file did not exist
err = errors.New(NoSuchFile)
goto done
}
if temproot, err = root.Arrived(username); err != nil {
// The Arrived callback failed for some arbitrary reason.
goto done
}
if temproot != nil {
root = temproot
}
}
if addToLoc {
newloc = append(newloc, root)
}
q, err = root.Qid()
if err != nil {
return nil, nil, err
}
qids = append(qids, q)
}
done:
if err != nil && len(qids) == 0 {
return nil, nil, err
}
if len(qids) < len(names) {
return nil, qids, nil
}
s := &fidState{
username: username,
location: newloc,
}
return s, qids, nil
}
