love2d.love/src/modules/math/RandomGenerator.h

/**
 * Copyright (c) 2006-2021 LOVE Development Team
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 **/

#ifndef LOVE_MATH_RANDOM_GENERATOR_H
#define LOVE_MATH_RANDOM_GENERATOR_H

// LOVE
#include "common/config.h"
#include "common/Exception.h"
#include "common/math.h"
#include "common/int.h"
#include "common/Object.h"

// C++
#include <limits>
#include <string>

namespace love
{
namespace math
{

class RandomGenerator : public Object
{
public:

	static love::Type type;

	union Seed
	{
		uint64 b64;
		struct
		{
#ifdef LOVE_BIG_ENDIAN
			uint32 high;
			uint32 low;
#else
			uint32 low;
			uint32 high;
#endif
		} b32;
	};

	RandomGenerator();
	virtual ~RandomGenerator() {}

	/**
	 * Return uniformly distributed pseudo random integer.
	 *
	 * @return Pseudo random integer in [0,2^64).
	 **/
	uint64 rand();

	/**
	 * Get uniformly distributed pseudo random number in [0,1).
	 *
	 * @return Pseudo random number in [0,1).
	 **/
	inline double random()
	{
		uint64 r = rand();

		// From http://xoroshiro.di.unimi.it
		union { uint64 i; double d; } u;
		u.i = ((0x3FFULL) << 52) | (r >> 12);

		return u.d - 1.0;
	}

	/**
	 * Get uniformly distributed pseudo random number in [0,max).
	 *
	 * @return Pseudo random number in [0,max).
	 **/
	inline double random(double max)
	{
		return random() * max;
	}

	/**
	 * Get uniformly distributed pseudo random number in [min, max).
	 *
	 * @return Pseudo random number in [min, max).
	 **/
	inline double random(double min, double max)
	{
		return random() * (max - min) + min;
	}

	/**
	 * Get normally distributed pseudo random number.
	 *
	 * @param stddev Standard deviation of the distribution.
	 * @return Normally distributed random number with mean 0 and variance (stddev)².
	 **/
	double randomNormal(double stddev);

	/**
	 * Set pseudo-random seed.
	 * It's up to the implementation how to use this.
	 **/
	void setSeed(Seed seed);

	/**
	 * Get the previously set pseudo-random seed.
	 **/
	Seed getSeed() const;

	/**
	 * Set the internal implementation-dependent state value based on a string.
	 **/
	void setState(const std::string &statestr);

	/**
	 * Get a string representation of the implementation-dependent internal
	 * state value.
	 **/
	std::string getState() const;

private:

	Seed seed;
	Seed rng_state;
	double last_randomnormal;

}; // RandomGenerator

} // math
} // love

#endif // LOVE_MATH_RANDOM_GENERATOR_H