| // Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| library interner; |
| |
| import 'dart:collection'; |
| |
| /** |
| * The interface `Interner` defines the behavior of objects that can intern |
| * strings. |
| */ |
| abstract class Interner { |
| /** |
| * Return a string that is identical to all of the other strings that have |
| * been interned that are equal to the given [string]. |
| */ |
| String intern(String string); |
| } |
| |
| /** |
| * The class `MappedInterner` implements an interner that uses a map to manage |
| * the strings that have been interned. |
| */ |
| class MappedInterner implements Interner { |
| /** |
| * A table mapping strings to themselves. |
| */ |
| Map<String, String> _table = new HashMap<String, String>(); |
| |
| @override |
| String intern(String string) { |
| String original = _table[string]; |
| if (original == null) { |
| _table[string] = string; |
| return string; |
| } |
| return original; |
| } |
| } |
| |
| /** |
| * The class `NullInterner` implements an interner that does nothing (does not |
| * actually intern any strings). |
| */ |
| class NullInterner implements Interner { |
| @override |
| String intern(String string) => string; |
| } |