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//
// A simple LRU cache
//
// Authors:
// Miguel de Icaza (miguel@gnome.org)
// Andres G. Aragoneses (andres@7digital.com)
//
// Copyright 2010 Miguel de Icaza
// Copyright 2013 7digital Media Ltd.
//
// 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.
//
using System;
using System.Collections.Generic;
namespace System.Web.Configuration {
class LruCache<TKey, TValue> {
Dictionary<TKey, LinkedListNode <TValue>> dict;
Dictionary<LinkedListNode<TValue>, TKey> revdict;
LinkedList<TValue> list;
int entry_limit;
bool eviction_warning_shown;
int evictions;
internal string EvictionWarning { set; private get; }
public LruCache (int entryLimit)
{
entry_limit = entryLimit;
dict = new Dictionary<TKey, LinkedListNode<TValue>> ();
revdict = new Dictionary<LinkedListNode<TValue>, TKey> ();
list = new LinkedList<TValue> ();
}
//for debugging: public int Count { get { return dict.Count; } }
void Evict ()
{
var last = list.Last;
if (last == null)
return;
var key = revdict [last];
dict.Remove (key);
revdict.Remove (last);
list.RemoveLast ();
DisposeValue (last.Value);
evictions++;
if (!String.IsNullOrEmpty (EvictionWarning) && !eviction_warning_shown && (evictions >= entry_limit)) {
Console.Error.WriteLine ("WARNING: " + EvictionWarning);
eviction_warning_shown = true;
}
}
public void Clear ()
{
foreach (var element in list) {
DisposeValue (element);
}
dict.Clear ();
revdict.Clear ();
list.Clear ();
eviction_warning_shown = false;
evictions = 0;
}
void DisposeValue (TValue value)
{
if (value is IDisposable) {
((IDisposable)value).Dispose ();
}
}
public bool TryGetValue (TKey key, out TValue value)
{
LinkedListNode<TValue> node;
if (dict.TryGetValue (key, out node)){
list.Remove (node);
list.AddFirst (node);
value = node.Value;
return true;
}
value = default (TValue);
return false;
}
public void Add (TKey key, TValue value)
{
LinkedListNode<TValue> node;
if (dict.TryGetValue (key, out node)){
// If we already have a key, move it to the front
list.Remove (node);
list.AddFirst (node);
// Remove the old value
DisposeValue (node.Value);
node.Value = value;
return;
}
if (dict.Count >= entry_limit)
Evict ();
// Adding new node
node = new LinkedListNode<TValue> (value);
list.AddFirst (node);
dict [key] = node;
revdict [node] = key;
}
public override string ToString ()
{
return "LRUCache dict={0} revdict={1} list={2}";
}
}
}
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