62 lines
2.1 KiB
C#
62 lines
2.1 KiB
C#
//------------------------------------------------------------
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// Copyright (c) Microsoft Corporation. All rights reserved.
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//------------------------------------------------------------
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using System;
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using System.Collections;
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using System.Collections.Concurrent;
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using System.Linq;
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using System.Text;
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using System.Threading;
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namespace System.ServiceModel.Dispatcher
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{
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class NameValueCache<T>
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{
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// The NameValueCache implements a structure that uses a dictionary to map objects to
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// indices of an array of cache entries. This allows us to store the cache entries in
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// the order in which they were added to the cache, and yet still lookup any cache entry.
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// The eviction policy of the cache is to evict the least-recently-added cache entry.
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// Using a pointer to the next available cache entry in the array, we can always be sure
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// that the given entry is the oldest entry.
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Hashtable cache;
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string[] currentKeys;
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int nextAvailableCacheIndex;
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object cachelock;
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internal const int maxNumberofEntriesInCache = 16;
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public NameValueCache()
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: this(maxNumberofEntriesInCache)
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{
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}
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public NameValueCache(int maxCacheEntries)
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{
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cache = new Hashtable();
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currentKeys = new string[maxCacheEntries];
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cachelock = new object();
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}
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public T Lookup(string key)
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{
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return (T)cache[key];
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}
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public void AddOrUpdate(string key, T value)
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{
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lock (cache)
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{
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if (!cache.ContainsKey(key))
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{
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if (!String.IsNullOrEmpty(currentKeys[nextAvailableCacheIndex]))
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{
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cache.Remove(currentKeys[nextAvailableCacheIndex]);
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}
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currentKeys[nextAvailableCacheIndex] = key;
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nextAvailableCacheIndex = ++nextAvailableCacheIndex % currentKeys.Length;
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}
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cache[key] = value;
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}
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}
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}
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}
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