mirror of
https://github.com/ppy/osu.git
synced 2024-09-22 03:27:24 +08:00
96 lines
3.2 KiB
C#
96 lines
3.2 KiB
C#
// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
|
|
// See the LICENCE file in the repository root for full licence text.
|
|
|
|
using System;
|
|
|
|
namespace osu.Game.Rulesets.Mania.MathUtils
|
|
{
|
|
/// <summary>
|
|
/// A PRNG specified in http://heliosphan.org/fastrandom.html.
|
|
/// </summary>
|
|
internal class FastRandom
|
|
{
|
|
private const double int_to_real = 1.0 / (int.MaxValue + 1.0);
|
|
private const uint int_mask = 0x7FFFFFFF;
|
|
private const uint y = 842502087;
|
|
private const uint z = 3579807591;
|
|
private const uint w = 273326509;
|
|
|
|
internal uint X { get; private set; }
|
|
internal uint Y { get; private set; } = y;
|
|
internal uint Z { get; private set; } = z;
|
|
internal uint W { get; private set; } = w;
|
|
|
|
public FastRandom(int seed)
|
|
{
|
|
X = (uint)seed;
|
|
}
|
|
|
|
public FastRandom()
|
|
: this(Environment.TickCount)
|
|
{
|
|
}
|
|
|
|
/// <summary>
|
|
/// Generates a random unsigned integer within the range [<see cref="uint.MinValue"/>, <see cref="uint.MaxValue"/>).
|
|
/// </summary>
|
|
/// <returns>The random value.</returns>
|
|
public uint NextUInt()
|
|
{
|
|
uint t = X ^ (X << 11);
|
|
X = Y;
|
|
Y = Z;
|
|
Z = W;
|
|
return W = W ^ (W >> 19) ^ t ^ (t >> 8);
|
|
}
|
|
|
|
/// <summary>
|
|
/// Generates a random integer value within the range [0, <see cref="int.MaxValue"/>).
|
|
/// </summary>
|
|
/// <returns>The random value.</returns>
|
|
public int Next() => (int)(int_mask & NextUInt());
|
|
|
|
/// <summary>
|
|
/// Generates a random integer value within the range [0, <paramref name="upperBound"/>).
|
|
/// </summary>
|
|
/// <param name="upperBound">The upper bound.</param>
|
|
/// <returns>The random value.</returns>
|
|
public int Next(int upperBound) => (int)(NextDouble() * upperBound);
|
|
|
|
/// <summary>
|
|
/// Generates a random integer value within the range [<paramref name="lowerBound"/>, <paramref name="upperBound"/>).
|
|
/// </summary>
|
|
/// <param name="lowerBound">The lower bound of the range.</param>
|
|
/// <param name="upperBound">The upper bound of the range.</param>
|
|
/// <returns>The random value.</returns>
|
|
public int Next(int lowerBound, int upperBound) => (int)(lowerBound + NextDouble() * (upperBound - lowerBound));
|
|
|
|
/// <summary>
|
|
/// Generates a random double value within the range [0, 1).
|
|
/// </summary>
|
|
/// <returns>The random value.</returns>
|
|
public double NextDouble() => int_to_real * Next();
|
|
|
|
private uint bitBuffer;
|
|
private int bitIndex = 32;
|
|
|
|
/// <summary>
|
|
/// Generates a reandom boolean value. Cached such that a random value is only generated once in every 32 calls.
|
|
/// </summary>
|
|
/// <returns>The random value.</returns>
|
|
public bool NextBool()
|
|
{
|
|
if (bitIndex == 32)
|
|
{
|
|
bitBuffer = NextUInt();
|
|
bitIndex = 1;
|
|
|
|
return (bitBuffer & 1) == 1;
|
|
}
|
|
|
|
bitIndex++;
|
|
return ((bitBuffer >>= 1) & 1) == 1;
|
|
}
|
|
}
|
|
}
|