IAPDemo/Libraries/cocos2d/cocos/rparticle/Math/Random/rand.h

//
//  rand.h
//  cocos2d_libs
//
//  Created by 徐俊杰 on 2020/5/25.
//

#ifndef rand_h
#define rand_h

#include "rparticle/Macros/RParticleMacros.h"

/*
 Some random generator timings:
 MacBook Pro w/ Core 2 Duo 2.4GHz. Times are for gcc 4.0.1 (OS X 10.6.2) / VS2008 SP1 (Win XP SP3),
 in milliseconds for this loop (4915200 calls):
 
 for (int j = 0; j < 100; ++j)
 for (int i = 0; i < 128*128*3; ++i)
 data[i] = (rnd.get() & 0x3) << 6;
 
 gcc   vs2008    Size
 C's rand():       57.0  109.3 ms     1
 Mersenne Twister: 56.0   37.4 ms  2500
 Unity 2.x LCG:    11.1    9.2 ms     4
 Xorshift 128:     15.0   17.8 ms    16
 Xorshift 32:      20.6   10.7 ms     4
 WELL 512:         43.6   55.1 ms    68
 */

NS_RRP_BEGIN

// Xorshift 128 implementation
// Xorshift paper: http://www.jstatsoft.org/v08/i14/paper
// Wikipedia: http://en.wikipedia.org/wiki/Xorshift
class Rand {
public:
    
    Rand (UInt32 seed = 0)
    {
        SetSeed (seed);
    }
    
    UInt32 Get ()
    {
        UInt32 t;
        t = x ^ (x << 11);
        x = y; y = z; z = w;
        return w = (w ^ (w >> 19)) ^ (t ^ (t >> 8));
    }
    
    inline static float GetFloatFromInt (UInt32 value)
    {
        // take 23 bits of integer, and divide by 2^23-1
        return float(value & 0x007FFFFF) * (1.0f / 8388607.0f);
    }
    
    inline static UInt8 GetByteFromInt (UInt32 value)
    {
        // take the most significant byte from the 23-bit value
        return UInt8(value >> (23 - 8));
    }
    
    // random number between 0.0 and 1.0
    float GetFloat ()
    {
        return GetFloatFromInt (Get ());
    }
    
    // random number between -1.0 and 1.0
    float GetSignedFloat ()
    {
        return GetFloat() * 2.0f - 1.0f;
    }
    
    void SetSeed (UInt32 seed)
    {
        x = seed;
        y = x * 1812433253U + 1;
        z = y * 1812433253U + 1;
        w = z * 1812433253U + 1;
    }
    
    UInt32 GetSeed () const { return x; }
    
private:
    UInt32 x, y, z, w;
};

NS_RRP_END

#endif /* rand_h */