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using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Threading;
namespace ChocolArm64
{
class TranslatorCache
{
//Maximum size of the cache, in bytes, measured in ARM code size.
private const int MaxTotalSize = 4 * 1024 * 256;
//Minimum time required in milliseconds for a method to be eligible for deletion.
private const int MinTimeDelta = 2 * 60000;
//Minimum number of calls required to update the timestamp.
private const int MinCallCountForUpdate = 250;
private class CacheBucket
{
public TranslatedSub Subroutine { get; private set; }
public LinkedListNode<long> Node { get; private set; }
public int CallCount { get; set; }
public int Size { get; private set; }
public long Timestamp { get; private set; }
public CacheBucket(TranslatedSub subroutine, LinkedListNode<long> node, int size)
{
Subroutine = subroutine;
Size = size;
UpdateNode(node);
}
public void UpdateNode(LinkedListNode<long> node)
{
Node = node;
Timestamp = GetTimestamp();
}
}
private ConcurrentDictionary<long, CacheBucket> _cache;
private LinkedList<long> _sortedCache;
private int _totalSize;
public TranslatorCache()
{
_cache = new ConcurrentDictionary<long, CacheBucket>();
_sortedCache = new LinkedList<long>();
}
public void AddOrUpdate(long position, TranslatedSub subroutine, int size)
{
ClearCacheIfNeeded();
_totalSize += size;
lock (_sortedCache)
{
LinkedListNode<long> node = _sortedCache.AddLast(position);
CacheBucket newBucket = new CacheBucket(subroutine, node, size);
_cache.AddOrUpdate(position, newBucket, (key, bucket) =>
{
_totalSize -= bucket.Size;
_sortedCache.Remove(bucket.Node);
return newBucket;
});
}
}
public bool HasSubroutine(long position)
{
return _cache.ContainsKey(position);
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public bool TryGetSubroutine(long position, out TranslatedSub subroutine)
{
if (_cache.TryGetValue(position, out CacheBucket bucket))
{
if (bucket.CallCount++ > MinCallCountForUpdate)
{
if (Monitor.TryEnter(_sortedCache))
{
try
{
bucket.CallCount = 0;
_sortedCache.Remove(bucket.Node);
bucket.UpdateNode(_sortedCache.AddLast(position));
}
finally
{
Monitor.Exit(_sortedCache);
}
}
}
subroutine = bucket.Subroutine;
return true;
}
subroutine = default(TranslatedSub);
return false;
}
private void ClearCacheIfNeeded()
{
long timestamp = GetTimestamp();
while (_totalSize > MaxTotalSize)
{
lock (_sortedCache)
{
LinkedListNode<long> node = _sortedCache.First;
if (node == null)
{
break;
}
CacheBucket bucket = _cache[node.Value];
long timeDelta = timestamp - bucket.Timestamp;
if (timeDelta <= MinTimeDelta)
{
break;
}
if (_cache.TryRemove(node.Value, out bucket))
{
_totalSize -= bucket.Size;
_sortedCache.Remove(bucket.Node);
}
}
}
}
private static long GetTimestamp()
{
long timestamp = Stopwatch.GetTimestamp();
return timestamp / (Stopwatch.Frequency / 1000);
}
}
}
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