using System;

using System.Threading; 

using System.Collections.Generic;

using System.Linq;

​

​

public class CircularBuffer<T>

{

    private readonly ReaderWriterLockSlim slimLock = new ReaderWriterLockSlim();

    private readonly int capacity;

    private readonly T[] buffer;

    private readonly int upperBound;

​

    private int currentIndex = -1;

    private int currentStart = 0;

​

    public CircularBuffer(int size)

    {

        if (size < 1)

        {

            throw new ArgumentException("Cannot be negative nor zero");

        }

​

        buffer = new T[size];

        capacity = size;

        upperBound = size - 1;

    }

​

    public void Add(T value)

    {

        slimLock.EnterWriteLock();

        try

        {

​

            if (IsFull || currentIndex == upperBound)

            {

                currentStart = FetchNextSlot(currentStart);

                IsFull = true;

            }

​

            currentIndex = FetchNextSlot(currentIndex);

            buffer[currentIndex] = value;

​

        }

        finally

        {

            slimLock.ExitWriteLock();

        }

​

    }

​

    public bool IsFull { get; private set; }

​

    private int FetchNextSlot(int value)

    {

        return (value + 1) % capacity;

    }

​

    public IEnumerable<T> Latest()

    {

        slimLock.EnterReadLock();

        try

        {

            return FetchItems().ToArray();

        }

        finally

        {

            slimLock.ExitReadLock();

        }

    }

​

    private IEnumerable<T> FetchItems()

    {

        IEnumerable<T> fetchedItems = Enumerable.Empty<T>();

        if (IsFull)

        {

            fetchedItems = FetchItems(currentStart, upperBound);

        }

        return fetchedItems.Concat(FetchItems(0, currentIndex));

    }

    private IEnumerable<T> FetchItems(int start, int end)

    {

        for (int i = start; i <= end; i++)

        {

            yield return buffer[i];

        }

    }

}  

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        var buffer = new CircularBuffer<float>(4);

        buffer.Add(1.0f);

        buffer.Add(1.0f);

        buffer.Add(1.0f);

        buffer.Add(1.0f);

        buffer.Add(1.0f);

        buffer.Add(1.0f);

        buffer.Add(1.0f);

        buffer.Add(1.0f);

        Console.WriteLine(string.Format("Length should be 4: {0}", buffer.Latest().ToArray().Length ));

    }

}