Source file prefix.ml

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(**
 * Copyright (c) 2015, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
*)


(*****************************************************************************)
(* The prefix is used to guarantee that we are not mixing different kind of
 * keys in the heap.
 * It just creates a new prefix every time its called.
 * The $ at the end of the prefix ensures that we don't have ambiguities if a key
 * happens to start with a digit.
*)
(*****************************************************************************)

type t = string

let make =
  let prefix_count = ref 0 in
  fun () ->
    incr prefix_count;
    string_of_int !prefix_count ^ "$"

let make_key prefix k =
  prefix ^ k

let remove prefix k =
  let prefix_size = String.length prefix in
  assert (String.sub k 0 prefix_size = prefix);
  String.sub k prefix_size (String.length k - prefix_size)