91 lines
2.6 KiB
C#
91 lines
2.6 KiB
C#
using System.Diagnostics.CodeAnalysis;
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using System.Runtime.CompilerServices;
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namespace PerfectNumbers.Core;
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public sealed class ConcurrentFixedCapacityStack<T>
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{
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[ThreadStatic]
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private static FixedCapacityArrayPool<T>? _arrayPool;
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private readonly T[] _items;
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private readonly int _capacity;
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private int _count = 0;
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public ConcurrentFixedCapacityStack(int capacity)
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{
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_arrayPool ??= FixedCapacityPools<T>.ExclusiveArray;
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_items = _arrayPool.Value.Rent(capacity);
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_capacity = capacity;
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}
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public int Count
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{
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[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
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get => Volatile.Read(ref _count);
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}
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public int Capacity
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{
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[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
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get => _capacity;
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
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public void Clear() => Interlocked.Exchange(ref _count, 0);
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[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
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public T? Pop() => TryPop(out T? item) ? item : default;
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[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
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/// <summary>
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/// Tries popping the first element from the stack. It doesn't clear the internal memory buffer from unused references.
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/// </summary>
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/// <returns>Returns false when the stack is empty. Returns true otherwise. If the stack was not empty, item contains the first element from the stack.
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public bool TryPop([NotNullWhen(true)] out T? item)
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{
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while (true)
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{
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int observed = Volatile.Read(ref _count);
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if (observed == 0)
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{
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item = default;
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return false;
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}
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int next = observed - 1;
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if (Interlocked.CompareExchange(ref _count, next, observed) == observed)
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{
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item = _items[next]!;
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return true;
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}
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}
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
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public void Push(T item)
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{
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int next = Interlocked.Increment(ref _count);
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if (next <= _capacity)
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{
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_items[next - 1] = item;
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return;
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}
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ArgumentOutOfRangeException.ThrowIfGreaterThan(next, _capacity);
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
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public static void Return(in T[] items) => _arrayPool!.Value.Return(items);
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[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
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public T[] ToArray()
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{
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int count = Volatile.Read(ref _count);
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T[] result = _arrayPool!.Value.Rent(count);
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Array.Copy(_items, result, count);
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return result;
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}
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}
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