//
// MemoryCacheLRU.cs
//
// Authors:
// Marek Habersack <mhabersack@novell.com>
//
// Copyright (C) 2010 Novell, Inc. (http://novell.com/)
//
// 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.Runtime.Caching{
// NOTE: all the public methods in this assume that the owner's write lock is held
sealed class MemoryCacheLRU
{
int trimLowerBound;
Dictionary <int, LinkedListNode <MemoryCacheEntry>> index;
LinkedList <MemoryCacheEntry> lru;
MemoryCacheContainer owner;
public MemoryCacheLRU (MemoryCacheContainer owner, int trimLowerBound)
{
this.trimLowerBound = trimLowerBound;
index = new Dictionary <int, LinkedListNode <MemoryCacheEntry>> ();
lru = new LinkedList <MemoryCacheEntry> ();
this.owner = owner;
}
public void Update (MemoryCacheEntry entry)
{
if (entry == null)
return;
int hash = entry.GetHashCode ();
LinkedListNode <MemoryCacheEntry> node;
if (!index.TryGetValue (hash, out node)) {
node = new LinkedListNode <MemoryCacheEntry> (entry);
index.Add (hash, node);
} else {
lru.Remove (node);
node.Value = entry;
}
lru.AddLast (node);
}
public void Remove (MemoryCacheEntry entry)
{
if (entry == null)
return;
int hash = entry.GetHashCode ();
LinkedListNode <MemoryCacheEntry> node;
if (index.TryGetValue (hash, out node)) {
lru.Remove (node);
index.Remove (hash);
}
}
public long Trim (long upTo)
{
int count = index.Count;
if (count <= 10)
return 0;
// The list is used below to reproduce .NET's behavior which selects the
// entries using the LRU order, but it removes them from the cache in the
// MRU order
var toremove = new List <MemoryCacheEntry> ((int)upTo);
long removed = 0;
MemoryCacheEntry entry;
while (upTo > removed && count > 10) {
entry = lru.First.Value;
toremove.Insert (0, entry);
Remove (entry);
removed++;
count--;
}
foreach (MemoryCacheEntry e in toremove)
owner.Remove (e.Key, false);
return removed;
}
}
}
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