FastRandom.cs

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using System;
 
namespace Terraria.Utilities;
 
public struct FastRandom
{
    private const ulong RANDOM_MULTIPLIER = 25214903917uL;
 
    private const ulong RANDOM_ADD = 11uL;
 
    private const ulong RANDOM_MASK = 281474976710655uL;
 
    public ulong Seed { get; private set; }
 
    public FastRandom(ulong seed)
    {
        this = default(FastRandom);
        Seed = seed;
    }
 
    public FastRandom(int seed)
    {
        this = default(FastRandom);
        Seed = (ulong)seed;
    }
 
    public FastRandom WithModifier(ulong modifier)
    {
        return new FastRandom(NextSeed(modifier) ^ Seed);
    }
 
    public FastRandom WithModifier(int x, int y)
    {
        return WithModifier((ulong)(x + 2654435769u + ((long)y << 6)) + ((ulong)y >> 2));
    }
 
    public static FastRandom CreateWithRandomSeed()
    {
        return new FastRandom((ulong)Guid.NewGuid().GetHashCode());
    }
 
    public void NextSeed()
    {
        Seed = NextSeed(Seed);
    }
 
    private int NextBits(int bits)
    {
        Seed = NextSeed(Seed);
        return (int)(Seed >> 48 - bits);
    }
 
    public float NextFloat()
    {
        return (float)NextBits(24) * 5.9604645E-08f;
    }
 
    public double NextDouble()
    {
        return (float)NextBits(32) * 4.656613E-10f;
    }
 
    public int Next(int max)
    {
        if ((max & -max) == max)
        {
            return (int)((long)max * (long)NextBits(31) >> 31);
        }
        int num;
        int num2;
        do
        {
            num = NextBits(31);
            num2 = num % max;
        }
        while (num - num2 + (max - 1) < 0);
        return num2;
    }
 
    public int Next(int min, int max)
    {
        return Next(max - min) + min;
    }
 
    private static ulong NextSeed(ulong seed)
    {
        return (seed * 25214903917L + 11) & 0xFFFFFFFFFFFFuL;
    }
}