ObjectPool.cs

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using System.Threading;
 
namespace System.Reflection.Internal;
 
internal sealed class ObjectPool<T> where T : class
{
    private struct Element
    {
        internal T Value;
    }
 
    private readonly Element[] _items;
 
    private readonly Func<T> _factory;
 
    internal ObjectPool(Func<T> factory)
        : this(factory, Environment.ProcessorCount * 2)
    {
    }
 
    internal ObjectPool(Func<T> factory, int size)
    {
        _factory = factory;
        _items = new Element[size];
    }
 
    private T CreateInstance()
    {
        return _factory();
    }
 
    internal T Allocate()
    {
        Element[] items = _items;
        int num = 0;
        T val;
        while (true)
        {
            if (num < items.Length)
            {
                val = items[num].Value;
                if (val != null && val == Interlocked.CompareExchange(ref items[num].Value, null, val))
                {
                    break;
                }
                num++;
                continue;
            }
            val = CreateInstance();
            break;
        }
        return val;
    }
 
    internal void Free(T obj)
    {
        Element[] items = _items;
        for (int i = 0; i < items.Length; i++)
        {
            if (items[i].Value == null)
            {
                items[i].Value = obj;
                break;
            }
        }
    }
}