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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 System.Windows.Forms;
internal abstract partial class RefCountedCache<TObject, TCacheEntryData, TKey>
{
/// <summary>
/// Cache entry that maintains the reference count, entry data, and basic cleanup logic.
/// </summary>
[DebuggerDisplay("{DebuggerDisplay}")]
public abstract class CacheEntry : IDisposable
{
private readonly bool _cached;
private int _refCount;
public TCacheEntryData Data { get; private set; }
public CacheEntry(TCacheEntryData data, bool cached)
{
Data = data;
_cached = cached;
}
/// <summary>
/// Add a reference to this entry.
/// </summary>
public void AddRef() => Interlocked.Increment(ref _refCount);
/// <summary>
/// Current reference count for this entry.
/// </summary>
public int RefCount => _refCount;
/// <summary>
/// Removes a reference to this entry.
/// </summary>
/// <remarks>
/// <para>
/// This will dispose of the entry when the ref count reaches zero- if the entry isn't actually
/// cached <see cref="_cached"/>.
/// </para>
/// </remarks>
public virtual void RemoveRef()
{
int refCount = Interlocked.Decrement(ref _refCount);
// Did we over dispose??
Debug.Assert(refCount >= 0);
if (!_cached && refCount == 0)
{
// If this entry wasn't actually cached, we need to clean ourselves up when we're unreferenced.
// (This happens when there isn't enough room in the cache.)
Dispose(disposing: true);
}
}
/// <summary>
/// Implement this to provide the target object for users.
/// </summary>
public abstract TObject Object { get; }
public Scope CreateScope() => new(this);
private string DebuggerDisplay => $"Object: {Object} RefCount: {RefCount}";
/// <summary>
/// By default we dispose of <see cref="Data"/> and <see cref="Object"/> if they implement
/// <see cref="IDisposable" />. Override to provide custom cleanup logic.
/// </summary>
/// <param name="disposing"></param>
protected virtual void Dispose(bool disposing)
{
if (disposing)
{
var disposable = Object as IDisposable;
disposable?.Dispose();
disposable = Data as IDisposable;
disposable?.Dispose();
}
}
public void Dispose()
{
Dispose(disposing: true);
GC.SuppressFinalize(this);
}
}
}
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