// 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 }