Nikita Tsukanov
9 years ago
15 changed files with 241 additions and 59 deletions
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using System; |
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using System.Runtime.ConstrainedExecution; |
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using System.Threading; |
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namespace Avalonia.Utilities |
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{ |
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public interface IRef<out T> : IDisposable where T : class |
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{ |
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T Item { get; } |
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IRef<T> Clone(); |
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IRef<TResult> CloneAs<TResult>() where TResult : class; |
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} |
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public static class RefCountable |
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{ |
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public static IRef<T> Create<T>(T item) where T : class, IDisposable |
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{ |
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return new Ref<T>(item, new RefCounter(item)); |
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} |
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public static IRef<T> CreateUnownedNotClonable<T>(T item) where T : class |
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=> new TempRef<T>(item); |
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class TempRef<T> : IRef<T> where T : class |
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{ |
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public void Dispose() |
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{ |
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} |
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public TempRef(T item) |
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{ |
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Item = item; |
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} |
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public T Item { get; } |
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public IRef<T> Clone() => throw new NotSupportedException(); |
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public IRef<TResult> CloneAs<TResult>() where TResult : class |
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=> throw new NotSupportedException(); |
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} |
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class RefCounter |
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{ |
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private IDisposable _item; |
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private volatile int _refs; |
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private object _lock = new object(); |
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public RefCounter(IDisposable item) |
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{ |
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_item = item; |
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} |
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public void AddRef() |
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{ |
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Interlocked.Increment(ref _refs); |
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} |
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public void Release() |
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{ |
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if (Interlocked.Decrement(ref _refs) == 0) |
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{ |
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lock (_lock) |
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{ |
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_item?.Dispose(); |
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_item = null; |
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} |
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} |
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} |
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} |
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class Ref<T> : CriticalFinalizerObject, IRef<T> where T : class |
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{ |
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private T _item; |
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private RefCounter _counter; |
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private object _lock = new object(); |
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public Ref(T item, RefCounter counter) |
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{ |
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_item = item; |
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_counter = counter; |
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Thread.MemoryBarrier(); |
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_counter.AddRef(); |
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} |
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public void Dispose() |
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{ |
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lock (_lock) |
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{ |
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if (_item != null) |
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{ |
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_counter.Release(); |
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_item = null; |
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} |
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GC.SuppressFinalize(this); |
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} |
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} |
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~Ref() |
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{ |
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_counter?.Release(); |
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} |
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public T Item |
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{ |
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get |
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{ |
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lock (_lock) |
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{ |
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return _item; |
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} |
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} |
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} |
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public IRef<T> Clone() |
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{ |
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lock (_lock) |
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{ |
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if (_item != null) |
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return new Ref<T>(_item, _counter); |
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throw new ObjectDisposedException("Ref<" + typeof(T) + ">"); |
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} |
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} |
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public IRef<TResult> CloneAs<TResult>() where TResult : class |
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{ |
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lock (_lock) |
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{ |
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lock (_lock) |
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{ |
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if (_item != null) |
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return new Ref<TResult>((TResult) (object) _item, _counter); |
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throw new ObjectDisposedException("Ref<" + typeof(T) + ">"); |
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} |
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} |
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} |
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} |
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} |
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} |
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