private @Nullable DirectoryEntry lookUpLast(
      @Nullable File dir, Name name, Set<? super LinkOption> options, int linkDepth)
      throws IOException {
    Directory directory = toDirectory(dir);
    if (directory == null) {
      return null;
    }

    DirectoryEntry entry = directory.get(name);
    if (entry == null) {
      return new DirectoryEntry(directory, name, null);
    }

    File file = entry.file();
    if (!options.contains(LinkOption.NOFOLLOW_LINKS) && file.isSymbolicLink()) {
      return followSymbolicLink(dir, (SymbolicLink) file, linkDepth);
    }

    return getRealEntry(entry);
  }
Looks up the last element of a path.
jimfs/src/main/java/com/google/common/jimfs/FileTree.java