KianaBH3/KcpSharp/Base/KcpSendReceiveQueueItemCache.cs

#if NEED_LINKEDLIST_SHIM
using LinkedListOfQueueItem = KcpSharp.NetstandardShim.LinkedList<(KcpSharp.KcpBuffer Data, byte Fragment)>;
using LinkedListNodeOfQueueItem = KcpSharp.NetstandardShim.LinkedListNode<(KcpSharp.KcpBuffer Data, byte Fragment)>;
#else
using LinkedListNodeOfQueueItem =
    System.Collections.Generic.LinkedListNode<(KianaBH.KcpSharp.Base.KcpBuffer Data, byte Fragment
        )>;
using LinkedListOfQueueItem =
    System.Collections.Generic.LinkedList<(KianaBH.KcpSharp.Base.KcpBuffer Data, byte Fragment)>;
#endif

namespace KianaBH.KcpSharp.Base;

internal sealed class KcpSendReceiveQueueItemCache
{
    private readonly LinkedListOfQueueItem _list = new();
    private SpinLock _lock;

    public LinkedListNodeOfQueueItem Rent(in KcpBuffer buffer, byte fragment)
    {
        var lockTaken = false;
        try
        {
            _lock.Enter(ref lockTaken);

            var node = _list.First;
            if (node is null)
            {
                node = new LinkedListNodeOfQueueItem((buffer, fragment));
            }
            else
            {
                node.ValueRef = (buffer, fragment);
                _list.RemoveFirst();
            }

            return node;
        }
        finally
        {
            if (lockTaken) _lock.Exit();
        }
    }

    public void Return(LinkedListNodeOfQueueItem node)
    {
        node.ValueRef = default;

        var lockTaken = false;
        try
        {
            _lock.Enter(ref lockTaken);

            _list.AddLast(node);
        }
        finally
        {
            if (lockTaken) _lock.Exit();
        }
    }

    public void Clear()
    {
        var lockTaken = false;
        try
        {
            _lock.Enter(ref lockTaken);

            _list.Clear();
        }
        finally
        {
            if (lockTaken) _lock.Exit();
        }
    }
}