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