Move Index and IndexStore implementations into Engine.

pkg/analysis_server/lib/src/index/lru_cache.dart

-// 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 index.lru_cache;
-
-import 'dart:collection';
-
-
-/**
- * This handler is notified when an item is evicted from the cache.
- */
-typedef EvictionHandler<K, V>(K key, V value);
-
-/**
- * A hash-table based cache implementation.
- *
- * When it reaches the specified number of items, the item that has not been
- * accessed (both get and put) recently is evicted.
- */
-class LRUCache<K, V> {
-  final LinkedHashSet<K> _lastKeys = new LinkedHashSet<K>();
-  final HashMap<K, V> _map = new HashMap<K, V>();
-  final int _maxSize;
-  final EvictionHandler _handler;
-
-  LRUCache(this._maxSize, [this._handler]);
-
-  /**
-   * Returns the value for the given [key] or null if [key] is not
-   * in the cache.
-   */
-  V get(K key) {
-    V value = _map[key];
-    if (value != null) {
-      _lastKeys.remove(key);
-      _lastKeys.add(key);
-    }
-    return value;
-  }
-
-  /**
-   * Removes the association for the given [key].
-   */
-  void remove(K key) {
-    _lastKeys.remove(key);
-    _map.remove(key);
-  }
-
-  /**
-   * Associates the [key] with the given [value].
-   *
-   * If the cache is full, an item that has not been accessed recently is
-   * evicted.
-   */
-  void put(K key, V value) {
-    _lastKeys.remove(key);
-    _lastKeys.add(key);
-    if (_lastKeys.length > _maxSize) {
-      K evictedKey = _lastKeys.first;
-      V evictedValue = _map.remove(evictedKey);
-      _lastKeys.remove(evictedKey);
-      if (_handler != null) {
-        _handler(evictedKey, evictedValue);
-      }
-    }
-    _map[key] = value;
-  }
-}