mirror of
https://github.com/modernuo/ModernUO
synced 2026-08-11 22:23:06 -04:00
81 lines
2.9 KiB
C#
81 lines
2.9 KiB
C#
/*************************************************************************
|
|
* ModernUO *
|
|
* Copyright 2019-2026 - ModernUO Development Team *
|
|
* Email: hi@modernuo.com *
|
|
* File: StableRandom.cs *
|
|
* *
|
|
* This program is free software: you can redistribute it and/or modify *
|
|
* it under the terms of the GNU General Public License as published by *
|
|
* the Free Software Foundation, either version 3 of the License, or *
|
|
* (at your option) any later version. *
|
|
* *
|
|
* You should have received a copy of the GNU General Public License *
|
|
* along with this program. If not, see <http://www.gnu.org/licenses/>. *
|
|
*************************************************************************/
|
|
|
|
using System;
|
|
using System.Numerics;
|
|
using System.Runtime.CompilerServices;
|
|
|
|
namespace Server.Random;
|
|
|
|
public static class StableRandom
|
|
{
|
|
// Returns the first long of a new Rng. Used for stable values given a specific set of inputs.
|
|
public static long First(ulong seed, long maxValue)
|
|
{
|
|
Span<ulong> state = stackalloc ulong[4];
|
|
|
|
var x = seed;
|
|
state[0] = NextSplitMix(ref x);
|
|
state[1] = NextSplitMix(ref x);
|
|
state[2] = NextSplitMix(ref x);
|
|
state[3] = NextSplitMix(ref x);
|
|
|
|
return (long)NextUInt64(state, (ulong)maxValue);
|
|
}
|
|
|
|
[MethodImpl(MethodImplOptions.AggressiveInlining)]
|
|
private static ulong NextUInt64(Span<ulong> state, ulong maxValue)
|
|
{
|
|
var randomProduct = Math.BigMul(maxValue, NextUInt64(ref state), out var lowPart);
|
|
|
|
if (lowPart < maxValue)
|
|
{
|
|
var remainder = (0ul - maxValue) % maxValue;
|
|
|
|
while (lowPart < remainder)
|
|
{
|
|
randomProduct = Math.BigMul(maxValue, NextUInt64(ref state), out lowPart);
|
|
}
|
|
}
|
|
|
|
return randomProduct;
|
|
}
|
|
|
|
[MethodImpl(MethodImplOptions.AggressiveInlining)]
|
|
private static ulong NextUInt64(ref Span<ulong> state)
|
|
{
|
|
var result = BitOperations.RotateLeft(state[1] * 5, 7) * 9;
|
|
var t = state[1] << 17;
|
|
|
|
state[2] ^= state[0];
|
|
state[3] ^= state[1];
|
|
state[1] ^= state[2];
|
|
state[0] ^= state[3];
|
|
|
|
state[2] ^= t;
|
|
state[3] = BitOperations.RotateLeft(state[3], 45);
|
|
|
|
return result;
|
|
}
|
|
|
|
[MethodImpl(MethodImplOptions.AggressiveInlining)]
|
|
private static ulong NextSplitMix(ref ulong x)
|
|
{
|
|
var z = x += 0x9e3779b97f4a7c15;
|
|
z = (z ^ (z >> 30)) * 0xbf58476d1ce4e5b9;
|
|
z = (z ^ (z >> 27)) * 0x94d049bb133111eb;
|
|
return z ^ (z >> 31);
|
|
}
|
|
}
|