tetrees/Plugins/Wwise/ThirdParty/include/AK/Tools/Common/AkRng.h

/*******************************************************************************
The content of this file includes portions of the AUDIOKINETIC Wwise Technology
released in source code form as part of the SDK installer package.

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  Copyright (c) 2023 Audiokinetic Inc.
*******************************************************************************/

#pragma once

#include <AK/SoundEngine/Common/AkTypes.h>

/// A pseudorandom number generator appropriate for introducing randomness in DSP processing
/// LCG with Newlib/Musl characteristics: 64-bit seed, 31-bit output (see http://en.wikipedia.org/wiki/Linear_congruential_generator)
/// Warning: This RNG is not cryptographically secure! Do not use it as such!
class CAkRng
{
public:
	static constexpr AkUInt64 RANDOM_A = 6364136223846793005ULL;
	static constexpr AkUInt64 RANDOM_C = 1;
	static constexpr AkUInt32 RANDOM_MAX = 0x7FFFFFFF; // 31 bits

	/// Initialize using the specified seed
	CAkRng(AkUInt64 uSeed)
		: m_uSeed(uSeed)
	{}

	/// Returns the current seed value of the RNG
	inline AkUInt64 Seed() const
	{
		return m_uSeed;
	}

	/// Returns the next random number to be generated without advancing the RNG state
	inline AkUInt32 Peek() const
	{
		return Peek(m_uSeed);
	}

	/// Returns a random 31-bit unsigned integer
	inline AkUInt32 Random()
	{
		return Random(m_uSeed);
	}

	/// Returns a random 31-bit integer
	inline AkInt32 RandomInt()
	{
		return RandomInt(m_uSeed);
	}

	/// Returns a random float from 0.0 to 1.0
	AkReal32 RandomFloat()
	{
		return (AkReal32)Random(m_uSeed) / (AkReal32)RANDOM_MAX;
	}

	/// Returns a random 31-bit unsigned integer using provided seed
	static inline AkInt32 Random(AkUInt64 &io_uSeed)
	{
		io_uSeed = io_uSeed * RANDOM_A + RANDOM_C;
		return Peek(io_uSeed);
	}

	/// Returns a random 31-bit integer using provided seed
	static inline AkInt32 RandomInt(AkUInt64 &io_uSeed)
	{
		io_uSeed = io_uSeed * RANDOM_A + RANDOM_C;
		return (AkInt32)Peek(io_uSeed);
	}

	/// Returns the next random number to be generated without advancing the RNG state
	static inline AkUInt32 Peek(AkUInt64 in_uSeed)
	{
		return (AkUInt32)(in_uSeed >> 33);
	}

private:
	AkUInt64 m_uSeed;
};