Voile/DaggerFramework/Source/External/LehmerRandom.cs

/// <summary>
/// https://github.com/YourRobotOverlord/LehmerRandom/blob/master/Lehmer/Random.cs
/// Alternative to System.Random based on the Lehmer algorithm.
/// </summary>
public class LehmerRandom
{
    // Stores the seed for the Next methods.
    private uint _seed;

    /// <summary>
    /// Initializes a new instance of the Random class, using a time-dependent default seed value.
    /// </summary>
    public LehmerRandom()
    {
        _seed = (uint)System.Environment.TickCount;
    }

    /// <summary>
    /// Initializes a new instance of the Random class, using the specified seed value.
    /// </summary>
    /// <param name="seed"></param>
    public LehmerRandom(int seed)
    {
        _seed = (uint)seed;
    }

    /// <summary>
    /// Initializes a new instance of the Random class, using the specified seed value.
    /// </summary>
    /// <param name="seed"></param>
    public LehmerRandom(uint seed)
    {
        _seed = seed;
    }

    /// <summary>
    /// Returns a non-negative random integer.
    /// </summary>
    /// <returns>Int32</returns>
    public int Next()
    {
        return GetNextInt(0, int.MaxValue);
    }

    /// <summary>
    /// Returns a non-negative random integer that is less than the specified maximum.
    /// </summary>
    /// <param name="maxValue">Int32</param>
    /// <returns>Int32</returns>
    public int Next(int maxValue)
    {
        return GetNextInt(0, maxValue);
    }

    /// <summary>
    /// Returns a random integer that is within a specified range.
    /// </summary>
    /// <param name="minValue">Int32</param>
    /// <param name="maxValue">Int32</param>
    /// <returns>Int32</returns>
    public int Next(int minValue, int maxValue)
    {
        return GetNextInt(minValue, maxValue);
    }

    /// <summary>
    /// Returns a random floating-point number that is greater than or equal to 0.0, and less than 1.0
    /// </summary>
    /// <returns></returns>
    public double NextDouble()
    {
        return GetNextDouble(0.0, 1.0);
    }

    /// <summary>
    /// Returns a non-negative random floating-point number that is less than the specified maximum.
    /// </summary>
    /// <param name="maxValue"></param>
    /// <returns></returns>
    public double NextDouble(double maxValue)
    {
        return GetNextDouble(0.0, maxValue);
    }

    /// <summary>
    /// Returns a random floating-point number that is within a specified range.
    /// </summary>
    /// <param name="minValue"></param>
    /// <param name="maxValue"></param>
    /// <returns></returns>
    public double NextDouble(double minValue, double maxValue)
    {
        return GetNextDouble(minValue, maxValue);
    }

    /// <summary>
    /// Fills the elements of a specified array of bytes with random numbers.
    /// </summary>
    /// <param name="buffer">The array to be filled with random numbers.</param>
    public void NextBytes(byte[] buffer)
    {
        for (int i = 0; i < buffer.Length; i++)
        {
            buffer[i] = (byte)Next();
        }
    }

    // Returns a random int and sets the seed for the next pass.
    internal int GetNextInt(int minValue, int maxValue)
    {
        _seed = Rnd(_seed);
        return ConvertToIntRange(_seed, minValue, maxValue);
    }

    // Returns a random double and sets the seed for the next pass.
    internal double GetNextDouble(double minValue, double maxValue)
    {
        _seed = Rnd(_seed);
        return ConvertToDoubleRange(_seed, minValue, maxValue);
    }

    /// <summary>
    /// Returns a random integer that is within a specified range, using the specified seed value.
    /// </summary>
    /// <param name="seed"></param>
    /// <param name="minValue"></param>
    /// <param name="maxValue"></param>
    /// <returns></returns>
    public static int RndInt(uint seed, int minValue, int maxValue)
    {
        return GetInt(seed, minValue, maxValue);
    }

    /// <summary>
    /// Returns a random integer that is within a specified range, using a time-dependent default seed value.
    /// </summary>
    /// <param name="minValue"></param>
    /// <param name="maxValue"></param>
    /// <returns></returns>
    public static int RndInt(int minValue, int maxValue)
    {
        return GetInt((uint)System.Environment.TickCount, minValue, maxValue);
    }

    /// <summary>
    /// Returns a random double that is within a specified range, using the specified seed value.
    /// </summary>
    /// <param name="seed"></param>
    /// <param name="minValue"></param>
    /// <param name="maxValue"></param>
    /// <returns></returns>
    public static double RndDouble(uint seed, double minValue, double maxValue)
    {
        return GetDouble(seed, minValue, maxValue);
    }

    /// <summary>
    /// Returns a random double that is within a specified range, using a time-dependent default seed value.
    /// </summary>
    /// <param name="minValue"></param>
    /// <param name="maxValue"></param>
    /// <returns></returns>
    public static double RndDouble(double minValue, double maxValue)
    {
        return GetDouble((uint)System.Environment.TickCount, minValue, maxValue);
    }

    internal static int GetInt(uint seed, int minValue, int maxValue)
    {
        return ConvertToIntRange(Rnd(seed), minValue, maxValue);
    }

    internal static double GetDouble(uint seed, double minValue, double maxValue)
    {
        return ConvertToDoubleRange(Rnd(seed), minValue, maxValue);
    }

    // Converts uint to integer within the given range.
    internal static int ConvertToIntRange(uint val, int minValue, int maxValue)
    {
        return (int)(val % (maxValue - minValue) + minValue);
    }

    // Converts uint to double within the given range.
    internal static double ConvertToDoubleRange(uint val, double minValue, double maxValue)
    {
        return (double)val / uint.MaxValue * (maxValue - minValue) + minValue;
    }

    // Pseudo-random number generator based on the Lehmer Algorithm
    // and javidx9's implementation:
    // https://github.com/OneLoneCoder/olcPixelGameEngine/blob/master/Videos/OneLoneCoder_PGE_ProcGen_Universe.cpp
    internal static uint Rnd(uint seed)
    {
        seed += 0xe120fc15;
        ulong tmp = (ulong)seed * 0x4a39b70d;
        uint m1 = (uint)((tmp >> 32) ^ tmp);
        tmp = (ulong)m1 * 0x12fad5c9;
        return (uint)((tmp >> 32) ^ tmp);
    }
}