flutter_flutter/tools/licenses/lib/cache.dart

// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'dart:collection';

Map<Key, dynamic> _cache = new LinkedHashMap<Key, dynamic>();
const int _maxSize = 10;

dynamic/*=T*/ cache/*<T>*/(Key key, dynamic/*=T*/ getter()) {
  dynamic/*=T*/ result = _cache[key];
  if (result != null) {
    _cache.remove(key);
  } else {
    if (_cache.length == _maxSize)
      _cache.remove(_cache.keys.first);
    result = getter();
    assert(result is! Function);
  }
  _cache[key] = result;
  return result;
}

abstract class Key {
  Key(this._value);

  final dynamic _value;

  @override
  bool operator ==(dynamic other) {
    if (identical(this, other))
      return true;
    if (runtimeType != other.runtimeType)
      return false;
    final Key typedOther = other;
    return _value == typedOther._value;
  }

  @override
  int get hashCode => runtimeType.hashCode ^ _value.hashCode;

  @override
  String toString() => '$runtimeType($_value)';
}