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Rename functions, and add NextInt.

This commit is contained in:
ekrctb 2020-11-30 18:46:28 +09:00
parent 731e689f2d
commit 51bddd4a0f
1 changed files with 36 additions and 6 deletions
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42
osu.Game/Utils/StatelessRNG.cs
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@ -1,6 +1,8 @@
// 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.Utils
{
/// <summary>
@ -22,7 +24,7 @@ private static ulong mix(ulong x)
}
/// <summary>
/// Compute an integer from given seed and series number.
/// Generate a random 64-bit unsigned integer from given seed.
/// </summary>
/// <param name="seed">
/// The seed value of this random number generator.
@ -31,11 +33,39 @@ private static ulong mix(ulong x)
/// The series number.
/// Different values are computed for the same seed in different series.
/// </param>
public static ulong Get(int seed, int series = 0) =>
unchecked(mix(((ulong)(uint)series << 32) | ((uint)seed ^ 0x12345678)));
public static ulong NextUlong(int seed, int series = 0)
{
unchecked
{
//
var combined = ((ulong)(uint)series << 32) | (uint)seed;
// The xor operation is to not map (0, 0) to 0.
return mix(combined ^ 0x12345678);
}
}
/// <summary>
/// Compute a floating point value between 0 and 1 (excluding 1) from given seed and series number.
/// Generate a random integer in range [0, maxValue) from given seed.
/// </summary>
/// <param name="maxValue">
/// The number of possible results.
/// </param>
/// <param name="seed">
/// The seed value of this random number generator.
/// </param>
/// <param name="series">
/// The series number.
/// Different values are computed for the same seed in different series.
/// </param>
public static int NextInt(int maxValue, int seed, int series = 0)
{
if (maxValue <= 0) throw new ArgumentOutOfRangeException(nameof(maxValue));
return (int)(NextUlong(seed, series) % (ulong)maxValue);
}
/// <summary>
/// Compute a random floating point value between 0 and 1 (excluding 1) from given seed and series number.
/// </summary>
/// <param name="seed">
/// The seed value of this random number generator.
@ -44,7 +74,7 @@ public static ulong Get(int seed, int series = 0) =>
/// The series number.
/// Different values are computed for the same seed in different series.
/// </param>
public static float GetSingle(int seed, int series = 0) =>
(float)(Get(seed, series) & ((1 << 24) - 1)) / (1 << 24); // float has 24-bit precision
public static float NextSingle(int seed, int series = 0) =>
(float)(NextUlong(seed, series) & ((1 << 24) - 1)) / (1 << 24); // float has 24-bit precision
}
}