/Merlin/Main/Runtime/Microsoft.Dynamic/Utils/CacheDict.cs
https://github.com/shri/ironruby · C# · 114 lines · 63 code · 11 blank · 40 comment · 8 complexity · a096170512b887ca7a2af1e908f3ba00 MD5 · raw file
- /* ****************************************************************************
- *
- * Copyright (c) Microsoft Corporation.
- *
- * This source code is subject to terms and conditions of the Microsoft Public License. A
- * copy of the license can be found in the License.html file at the root of this distribution. If
- * you cannot locate the Microsoft Public License, please send an email to
- * dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound
- * by the terms of the Microsoft Public License.
- *
- * You must not remove this notice, or any other, from this software.
- *
- *
- * ***************************************************************************/
- using System;
- using System.Collections.Generic;
- using System.Text;
- using System.Diagnostics;
- namespace Microsoft.Scripting.Utils {
- /// <summary>
- /// Provides a dictionary-like object used for caches which holds onto a maximum
- /// number of elements specified at construction time.
- ///
- /// This class is not thread safe.
- /// </summary>
- public class CacheDict<TKey, TValue> {
- private readonly Dictionary<TKey, KeyInfo> _dict = new Dictionary<TKey, KeyInfo>();
- private readonly LinkedList<TKey> _list = new LinkedList<TKey>();
- private readonly int _maxSize;
- /// <summary>
- /// Creates a dictionary-like object used for caches.
- /// </summary>
- /// <param name="maxSize">The maximum number of elements to store.</param>
- public CacheDict(int maxSize) {
- _maxSize = maxSize;
- }
- /// <summary>
- /// Tries to get the value associated with 'key', returning true if it's found and
- /// false if it's not present.
- /// </summary>
- public bool TryGetValue(TKey key, out TValue value) {
- KeyInfo storedValue;
- if (_dict.TryGetValue(key, out storedValue)) {
- LinkedListNode<TKey> node = storedValue.List;
- if (node.Previous != null) {
- // move us to the head of the list...
- _list.Remove(node);
- _list.AddFirst(node);
- }
- value = storedValue.Value;
- return true;
- }
- value = default(TValue);
- return false;
- }
- /// <summary>
- /// Adds a new element to the cache, replacing and moving it to the front if the
- /// element is already present.
- /// </summary>
- public void Add(TKey key, TValue value) {
- KeyInfo keyInfo;
- if (_dict.TryGetValue(key, out keyInfo)) {
- // remove original entry from the linked list
- _list.Remove(keyInfo.List);
- } else if (_list.Count == _maxSize) {
- // we've reached capacity, remove the last used element...
- LinkedListNode<TKey> node = _list.Last;
- _list.RemoveLast();
- bool res = _dict.Remove(node.Value);
- Debug.Assert(res);
- }
-
- // add the new entry to the head of the list and into the dictionary
- LinkedListNode<TKey> listNode = new LinkedListNode<TKey>(key);
- _list.AddFirst(listNode);
- _dict[key] = new CacheDict<TKey, TValue>.KeyInfo(value, listNode);
- }
- /// <summary>
- /// Returns the value associated with the given key, or throws KeyNotFoundException
- /// if the key is not present.
- /// </summary>
- [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1065:DoNotRaiseExceptionsInUnexpectedLocations")]
- public TValue this[TKey key] {
- get {
- TValue res;
- if (TryGetValue(key, out res)) {
- return res;
- }
- throw new KeyNotFoundException();
- }
- set {
- Add(key, value);
- }
- }
- private struct KeyInfo {
- internal readonly TValue Value;
- internal readonly LinkedListNode<TKey> List;
- internal KeyInfo(TValue value, LinkedListNode<TKey> list) {
- Value = value;
- List = list;
- }
- }
- }
- }