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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
namespace Aspire.Hosting.Analyzers.Infrastructure;
// This type is copied from https://github.com/dotnet/roslyn-analyzers/blob/9b58ec3ad33353d1a523cda8c4be38eaefc80ad8/src/Utilities/Compiler/BoundedCacheWithFactory.cs
/// <summary>
/// Provides bounded cache for analyzers.
/// Acts as a good alternative to <see cref="System.Runtime.CompilerServices.ConditionalWeakTable{TKey, TValue}"/>
/// when the cached value has a cyclic reference to the key preventing early garbage collection of entries.
/// </summary>
internal class BoundedCacheWithFactory<TKey, TValue>
where TKey : class
{
// Bounded weak reference cache.
// Size 5 is an arbitrarily chosen bound, which can be tuned in future as required.
private readonly List<WeakReference<Entry?>> _weakReferencedEntries = new()
{
new WeakReference<Entry?>(null),
new WeakReference<Entry?>(null),
new WeakReference<Entry?>(null),
new WeakReference<Entry?>(null),
new WeakReference<Entry?>(null),
};
public TValue GetOrCreateValue(TKey key, Func<TKey, TValue> valueFactory)
{
lock (_weakReferencedEntries)
{
var indexToSetTarget = -1;
for (var i = 0; i < _weakReferencedEntries.Count; i++)
{
var weakReferencedEntry = _weakReferencedEntries[i];
if (!weakReferencedEntry.TryGetTarget(out var cachedEntry) ||
cachedEntry == null)
{
if (indexToSetTarget == -1)
{
indexToSetTarget = i;
}
continue;
}
if (Equals(cachedEntry.Key, key))
{
// Move the cache hit item to the end of the list
// so it would be least likely to be evicted on next cache miss.
_weakReferencedEntries.RemoveAt(i);
_weakReferencedEntries.Add(weakReferencedEntry);
return cachedEntry.Value;
}
}
if (indexToSetTarget == -1)
{
indexToSetTarget = 0;
}
var newEntry = new Entry(key, valueFactory(key));
_weakReferencedEntries[indexToSetTarget].SetTarget(newEntry);
return newEntry.Value;
}
}
private sealed class Entry
{
public Entry(TKey key, TValue value)
{
Key = key;
Value = value;
}
public TKey Key { get; }
public TValue Value { get; }
}
}
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