#region License
//=============================================================================
// Vici Core - Productivity Library for .NET 3.5
//
// Copyright (c) 2008-2010 Philippe Leybaert
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.
//=============================================================================
#endregion
using System;
using System.Collections.Generic;
namespace Vici.Core.Cache{
public class SmartCache<T>
{
public static DateTime Min(DateTime t1, DateTime t2)
{
return t1 < t2 ? t1 : t2;
}
private class CachedItem
{
public readonly string Key;
public readonly T Value;
public DateTime ExpirationTime;
private readonly DateTime _absoluteExpiration;
private readonly TimeSpan _slidingExpiration;
public CachedItem(string key, T value, TimeSpan slidingExpiration, DateTime absoluteExpiration, ITimeProvider time)
{
Key = key;
Value = value;
_slidingExpiration = slidingExpiration;
_absoluteExpiration = absoluteExpiration;
ExpirationTime = Min(absoluteExpiration, time.Now.Add(slidingExpiration));
}
public void SetAccessed(ITimeProvider time)
{
ExpirationTime = Min(_absoluteExpiration, time.Now.Add(_slidingExpiration));
}
}
private readonly Dictionary<string, LinkedListNode<CachedItem>> _dic = new Dictionary<string, LinkedListNode<CachedItem>>();
private readonly LinkedList<CachedItem> _keys = new LinkedList<CachedItem>();
private readonly object _lock = new object();
private readonly ITimeProvider _time = new RealTimeProvider();
private static readonly TimeSpan _noSlidingExpiration = TimeSpan.FromDays(1000);
private static readonly DateTime _noAbsoluteExpiration = DateTime.MaxValue;
private TimeSpan _defaultSlidingExpiration = _noSlidingExpiration;
private DateTime _defaultAbsoluteExpiration = _noAbsoluteExpiration;
private int _cacheSize;
private TimeSpan _cleanupInterval = TimeSpan.FromSeconds(60);
private DateTime _nextCleanup;
public SmartCache(int cacheSize) : this(cacheSize, new RealTimeProvider())
{
}
internal SmartCache(int cacheSize, ITimeProvider timeProvider)
{
_cacheSize = cacheSize;
_time = timeProvider;
_nextCleanup = _time.Now.Add(CleanupInterval);
}
public int ItemCount
{
get
{
lock (_lock)
return _dic.Count;
}
}
public int CacheSize
{
get
{
lock (_lock)
return _cacheSize;
}
set
{
lock (_lock)
{
if (value < _cacheSize)
{
while (_dic.Count > value)
RemoveOldest();
}
_cacheSize = value;
}
}
}
public TimeSpan CleanupInterval
{
get
{
lock (_lock)
return _cleanupInterval;
}
set
{
lock (_lock)
{
_cleanupInterval = value;
_nextCleanup = _time.Now.Add(CleanupInterval);
}
}
}
public TimeSpan DefaultSlidingExpiration
{
get { return _defaultSlidingExpiration; }
set { _defaultSlidingExpiration = value; }
}
public DateTime DefaultAbsoluteExpiration
{
get { return _defaultAbsoluteExpiration; }
set { _defaultAbsoluteExpiration = value; }
}
public void ClearCache()
{
lock (_lock)
{
_dic.Clear();
_keys.Clear();
}
}
public bool TryGetValue(string key, out T item, Func<T> addFunc)
{
return TryGetValue(key, out item, DefaultSlidingExpiration, DefaultAbsoluteExpiration, addFunc);
}
public bool TryGetValue(string key, out T item, TimeSpan slidingExpiration, DateTime absoluteExpiration, Func<T> addFunc)
{
lock (_lock)
{
if (TryGetValue(key, out item))
return true;
Add(key, addFunc(), slidingExpiration, absoluteExpiration);
return true;
}
}
public bool TryGetValue(string key, out T item)
{
if (key == null)
throw new ArgumentNullException("key");
lock (_lock)
{
CheckCleanup();
LinkedListNode<CachedItem> node;
if (_dic.TryGetValue(key, out node))
{
if (node.Value.ExpirationTime < _time.Now)
{
Remove(node);
item = default(T);
return false;
}
else
Promote(key);
item = node.Value.Value;
return true;
}
}
item = default(T);
return false;
}
public void Remove(string key)
{
if (key == null)
throw new ArgumentNullException("key");
lock (_lock)
{
LinkedListNode<CachedItem> node;
if (_dic.TryGetValue(key, out node))
{
Remove(node);
}
}
}
// make sure we have a lock when calling this
// also make sure the item is in the cache
private void Promote(string key)
{
LinkedListNode<CachedItem> node = _dic[key];
_keys.Remove(node);
_keys.AddFirst(node);
node.Value.SetAccessed(_time);
}
// make sure we have a lock when calling this
private void RemoveOldest()
{
Remove(_keys.Last);
}
// make sure we have a lock when calling this
private void Remove(LinkedListNode<CachedItem> node)
{
_keys.Remove(node);
_dic.Remove(node.Value.Key);
}
// make sure we have a writer lock when calling this
private void CheckCleanup()
{
if (_time.Now < _nextCleanup)
return;
LinkedListNode<CachedItem> node = _keys.First;
while (node != null)
{
LinkedListNode<CachedItem> next = node.Next;
if (node.Value.ExpirationTime < _time.Now)
Remove(node);
node = next;
}
_nextCleanup = _time.Now.Add(CleanupInterval);
}
public void Add(string key, T item)
{
Add(key, item, DefaultSlidingExpiration, DefaultAbsoluteExpiration);
}
public void Add(string key, T item, TimeSpan slidingExpiration)
{
Add(key, item, slidingExpiration, DefaultAbsoluteExpiration);
}
public void Add(string key, T item, DateTime absoluteExpiration)
{
Add(key, item, DefaultSlidingExpiration, absoluteExpiration);
}
public void Add(string key, T item, TimeSpan slidingExpiration, DateTime absoluteExpiration)
{
lock (_lock)
{
LinkedListNode<CachedItem> node;
CachedItem cachedItem = new CachedItem(key, item, slidingExpiration, absoluteExpiration, _time);
if (_dic.TryGetValue(key, out node))
{
node.Value = cachedItem;
Promote(key);
return;
}
node = new LinkedListNode<CachedItem>(cachedItem);
if (_dic.Count >= _cacheSize)
RemoveOldest();
_keys.AddFirst(node);
_dic[key] = node;
}
}
}
}
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