using System;

using System.Threading;

/// <summary>

/// A minimal threadsafe counter.

/// </summary>

class AtomicCounter

{

/// <summary>

/// The current value of the counter.

/// </summary>

int currentValue = 0;

/// <summary>

/// Increments the value of the counter.

/// </summary>

///

/// <param name="incrementBy">The amount to increment.</param>

/// <exception cref="System.OverflowException">If the counter would overflow.</exception>

/// <returns>The new value of the counter.</returns>

///

/// <remarks>This method is threadsafe.</remarks>

public int Increment(int incrementBy = 1)

{

int oldValue, newValue;

do

{

oldValue = currentValue;

newValue = oldValue + incrementBy;

if (newValue < 0) throw new OverflowException("Counter value is out of range");

}

while (oldValue != Interlocked.CompareExchange(ref currentValue, newValue, oldValue));

return newValue;

}

}