SingleEntryGate

using System;
using System.Threading;

namespace Core.Threading {

    /// <summary>
    /// Used to synchronize access to a single-use consumable resource
    /// </summary>
    public sealed class SingleEntryGate {

        private const int NOT_ENTERED = 0;
        private const int ENTERED = 1;

        private int _status;

        /// <summary>
        /// Returns true if this is the first call to TryEnter(), false otherwise
        /// </summary>
        public bool TryEnter() {

            int oldStatus = Interlocked.Exchange(ref _status, ENTERED);

            return (oldStatus == NOT_ENTERED);
        }

    }
}