FIFOQueue.cs

    /// <summary>
    /// A first in last out queue
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class RollingQueue<T> : IEnumerable<T>
    {
        private T[] _stack;
        private int _stackReadIdx = 0;
        private int _stackWriteIdx = 0;

        public int Length;

        public RollingQueue(int stackSize = 5)
        {
            _stack = new T[stackSize];
            Length = stackSize;
        }

        /// <summary>
        /// Return the next element, looping back to the beginning if at the end
        /// </summary>
        /// <returns></returns>
        public T Next()
        {
            if (_stackReadIdx > _stack.Length-1)
                _stackReadIdx = 0;

            return _stack[_stackReadIdx++];
        }

        /// <summary>
        /// Query the next item in the stack without moving the index
        /// </summary>
        /// <returns></returns>
        public T Peek()
        {
            return _stack[Math.Min(_stackReadIdx, _stack.Length - 1)];
        }

        /// <summary>
        /// Add an element to the stack, looping back to the beginning if the stack is full
        /// </summary>
        /// <returns></returns>
        public void Add(T item)
        {
            if (_stackWriteIdx > _stack.Length-1)
                _stackWriteIdx = 0;

            _stack[_stackWriteIdx++] = item;
        }
        

        public IEnumerator<T> GetEnumerator()
        {
            return _stack.AsEnumerable().GetEnumerator();
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return _stack.GetEnumerator();
        }
    }