[C#]簡易的Backoff window實現類別

namespace ConsoleApplication12 { public class BackOff { #region Var private int _level; private Random _random; #endregion

	#region Private Property
	private ReadOnlyCollection<int> m_BackOffWindows { get; set; }

	private Random m_Random
	{
		get
		{
			if (_random == null)
				_random = new Random(Guid.NewGuid().GetHashCode());
			return _random;
		}
	}
	#endregion

	#region Public Property
	/// <summary>
	/// Gets or sets the level.
	/// </summary>
	/// <value>The level.</value>
	public int Level 
	{
		get
		{
			return _level;
		}
		set
		{
			if (value <= 0)
				throw new Exception("Level value must be bigger than zero!");

			if (value > m_BackOffWindows.Count)
				throw new Exception("Level value incorrect!");

			_level = value;
		}
	}
	#endregion
	
	#region Constructor
	/// <summary>
	/// Initializes a new instance of the <see cref="BackOff"/> class.
	/// </summary>
	/// <param name="backOffWindows">The back off windows.</param>
	public BackOff(params int[] backOffWindows)
	{
		CheckBackOffWindows(backOffWindows);		

		this.m_BackOffWindows = new ReadOnlyCollection<int>(backOffWindows.ToList());
		ResetLevel();
	}
	#endregion


	#region Private Method
	/// <summary>
	/// Checks the back off windows.
	/// </summary>
	/// <param name="backOffWindows">The back off windows.</param>
	private void CheckBackOffWindows(params int[] backOffWindows)
	{
		if (backOffWindows == null)
			throw new ArgumentNullException("backOffWindows");

		if (backOffWindows.Length == 0)
			throw new ArgumentException("backOffWindows must contains elements!");

		if (backOffWindows.First() <= 0)
			throw new ArgumentOutOfRangeException("First backOffWindow must bigger than zero!");

		var minValue = -1;
		foreach (var backOffWindow in backOffWindows)
		{
			if (backOffWindow < 0)
				throw new ArgumentOutOfRangeException("backOffWindows must bigger than zero!");

			if (minValue > backOffWindow)
				throw new ArgumentOutOfRangeException("backOffWindows must order by increase!");

			if (minValue == backOffWindow)
				throw new ArgumentOutOfRangeException("Can't contains duplicated elements!");

			minValue = backOffWindow;
		}
	}
	#endregion


	#region Public Method
	/// <summary>
	/// Increases the level.
	/// </summary>
	/// <returns></returns>
	public Boolean IncreaseLevel()
	{
		if (Level >= m_BackOffWindows.Count)
			return false;
		
		Level += 1;
		return true;
	}


	/// <summary>
	/// Decreases the level.
	/// </summary>
	/// <returns></returns>
	public Boolean DecreaseLevel()
	{
		if (Level <= 1)
			return false;
		
		Level -= 1;
		return true;
	}

	public void ResetLevel()
	{
		Level = 1;
	}

	/// <summary>
	/// Gets the next value.
	/// </summary>
	/// <returns></returns>
	public int NextValue()
	{
		var minValue = (Level == 1) ? 0 : m_BackOffWindows[Level - 2];
		var maxValue = m_BackOffWindows[Level - 1];

		return m_Random.Next(minValue, maxValue);
	}
	#endregion
}

}

namespace ConsoleApplication12 { class Program { static void Main(string[] args) { BackOff backoff = new BackOff(16,32,64);

		Console.WriteLine("Level1...");
		Console.WriteLine(backoff.NextValue().ToString());
		Console.WriteLine(backoff.NextValue().ToString());
		Console.WriteLine(backoff.NextValue().ToString());
		Console.WriteLine(new string('=', 50));

		backoff.IncreaseLevel();
		Console.WriteLine("Level2...");
		Console.WriteLine(backoff.NextValue().ToString());
		Console.WriteLine(backoff.NextValue().ToString());
		Console.WriteLine(backoff.NextValue().ToString());
		Console.WriteLine(new string('=', 50));

		backoff.IncreaseLevel();
		Console.WriteLine("Level3...");
		Console.WriteLine(backoff.NextValue().ToString());
		Console.WriteLine(backoff.NextValue().ToString());
		Console.WriteLine(backoff.NextValue().ToString());
		Console.WriteLine(new string('=', 50));
	}
}

}

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