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| 1 // Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file |
| 2 // for details. All rights reserved. Use of this source code is governed by a |
| 3 // BSD-style license that can be found in the LICENSE file. |
| 4 |
| 5 library interner; |
| 6 |
| 7 import 'dart:collection'; |
| 8 |
| 9 /** |
| 10 * The interface `Interner` defines the behavior of objects that can intern |
| 11 * strings. |
| 12 */ |
| 13 abstract class Interner { |
| 14 /** |
| 15 * Return a string that is identical to all of the other strings that have |
| 16 * been interned that are equal to the given [string]. |
| 17 */ |
| 18 String intern(String string); |
| 19 } |
| 20 |
| 21 /** |
| 22 * The class `MappedInterner` implements an interner that uses a map to manage |
| 23 * the strings that have been interned. |
| 24 */ |
| 25 class MappedInterner implements Interner { |
| 26 /** |
| 27 * A table mapping strings to themselves. |
| 28 */ |
| 29 Map<String, String> _table = new HashMap<String, String>(); |
| 30 |
| 31 @override |
| 32 String intern(String string) { |
| 33 String original = _table[string]; |
| 34 if (original == null) { |
| 35 _table[string] = string; |
| 36 return string; |
| 37 } |
| 38 return original; |
| 39 } |
| 40 } |
| 41 |
| 42 /** |
| 43 * The class `NullInterner` implements an interner that does nothing (does not |
| 44 * actually intern any strings). |
| 45 */ |
| 46 class NullInterner implements Interner { |
| 47 @override |
| 48 String intern(String string) => string; |
| 49 } |
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