93 lines
3.4 KiB
C#
93 lines
3.4 KiB
C#
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/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System;
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using System.Collections.Generic;
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namespace Mono.Utilities
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{
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public class LRUCache<TKey, TValue>
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{
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[ThreadStatic]
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static LRUCache<TKey, TValue> deflt;
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public static LRUCache<TKey, TValue> Default {
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get {
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return deflt != null ? deflt : (deflt = new LRUCache<TKey, TValue> (5));
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}
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}
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int capacity;
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LinkedList<ListValueEntry<TKey, TValue>> list;
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Dictionary<TKey, LinkedListNode<ListValueEntry<TKey, TValue>>> lookup;
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LinkedListNode<ListValueEntry<TKey, TValue>> openNode;
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public LRUCache (int capacity)
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{
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this.capacity = capacity;
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this.list = new LinkedList<ListValueEntry<TKey, TValue>>();
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this.lookup = new Dictionary<TKey, LinkedListNode<ListValueEntry<TKey, TValue>>> (capacity + 1);
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this.openNode = new LinkedListNode<ListValueEntry<TKey, TValue>>(new ListValueEntry<TKey, TValue> (default(TKey), default(TValue)));
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}
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public void Put (TKey key, TValue value)
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{
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if (Get(key) == null) {
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this.openNode.Value.ItemKey = key;
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this.openNode.Value.ItemValue = value;
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this.list.AddFirst (this.openNode);
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this.lookup.Add (key, this.openNode);
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if (this.list.Count > this.capacity) {
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// last node is to be removed and saved for the next addition to the cache
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this.openNode = this.list.Last;
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// remove from list & dictionary
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this.list.RemoveLast();
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this.lookup.Remove(this.openNode.Value.ItemKey);
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} else {
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// still filling the cache, create a new open node for the next time
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this.openNode = new LinkedListNode<ListValueEntry<TKey, TValue>>(new ListValueEntry<TKey, TValue>(default(TKey), default(TValue)));
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}
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}
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}
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public TValue Get (TKey key)
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{
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LinkedListNode<ListValueEntry<TKey, TValue>> node = null;
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if (!this.lookup.TryGetValue (key, out node))
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return default (TValue);
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this.list.Remove (node);
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this.list.AddFirst (node);
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return node.Value.ItemValue;
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}
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class ListValueEntry<K, V> where K : TKey
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where V : TValue
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{
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internal V ItemValue;
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internal K ItemKey;
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internal ListValueEntry(K key, V value)
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{
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this.ItemKey = key;
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this.ItemValue = value;
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}
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}
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}
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}
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