random.cpp

// Header files
#include "random.h"

// Initialize the constants for 64 bit random values
// Xn+1 = A * Xn + B (mod 2^64)
const uint64 CRandomGenerator::A_CONSTANT_64 = (uint64)(0x27BB2EE6)*(0x010000)*(0x010000) + (uint64)(0x87B0B0F);
const uint64 CRandomGenerator::B_CONSTANT_64 = 0xB504F32D;

// Initialize the constants for 32 bit random values
// Xn+1 = A * Xn + B (mod 2^32)
const uint32 CRandomGenerator::A_CONSTANT_32 = 0x0019660D;
const uint32 CRandomGenerator::B_CONSTANT_32 = 0x3C6EF35F;

// Initialize maximum integer values
const uint64 CRandomGenerator::MAX_INT_64 = (uint64)(0xFFFFFFFF)*(0x010000)*(0x010000) + (uint64)(0xFFFFFFFF);
const uint32 CRandomGenerator::MAX_INT_32 = (uint32)(0xFFFFFFFF);

// Initialize scaling values for random float generations
const float64 CRandomGenerator::FLOAT_SCALE_64 = (float64)1.0 / (float64)MAX_INT_64;
const float32 CRandomGenerator::FLOAT_SCALE_32 = (float32)1.0 / (float32)MAX_INT_32;

/*******************************************************
* Function: CRandomGenerator::CRandomGenerator()
* Purpose : Constructor for random number generator
* Initial : Max Payne on July 19, 2005
********************************************************
Revisions and bug fixes:
*/
CRandomGenerator::CRandomGenerator()
{
	// Initialize the random seed to an arbitrary value
	m_Seed.Int64 = 0;
	m_Seed.Int32 = 1337;
}

/*******************************************************
* Function: CRandomGenerator::~CRandomGenerator()
* Purpose : Destructor for random number generator
* Initial : Max Payne on July 19, 2005
********************************************************
Revisions and bug fixes:
*/
CRandomGenerator::~CRandomGenerator()
{
}

/*******************************************************
* Function: CRandomGenerator::CRandomGenerator()
* Purpose : Constructor for random number generator
* Initial : Max Payne on July 19, 2005
********************************************************
Revisions and bug fixes:
*/
void CRandomGenerator::SetSeed(uint32 Seed)
{
	// Set the new random seed
    m_Seed.Int64 = 0;
    m_Seed.Int32 = Seed;
}

/*******************************************************
* Function: CRandomGenerator::RandomInt64()
* Purpose : Generate a random 64 bit integer
* Initial : Max Payne on July 19, 2005
********************************************************
Revisions and bug fixes:
*/
uint64 CRandomGenerator::RandomInt64()
{
	// Generate a new random integer
    m_Seed.Int64 = m_Seed.Int64 * A_CONSTANT_64 + B_CONSTANT_64;

	// Return the new random integer
    return m_Seed.Int64;
}

/*******************************************************
* Function: CRandomGenerator::RandomInt32()
* Purpose : Generate a random 32 bit integer
* Initial : Max Payne on July 19, 2005
********************************************************
Revisions and bug fixes:
*/
uint32 CRandomGenerator::RandomInt32()
{
	// Generate a new random integer
    m_Seed.Int32 = m_Seed.Int32 * A_CONSTANT_32 + B_CONSTANT_32;

	// Return the new random integer
    return m_Seed.Int32;
}

/*******************************************************
* Function: CRandomGenerator::RandomFloat64()
* Purpose : Generate a random 64 bit float
* Initial : Max Payne on July 19, 2005
********************************************************
Revisions and bug fixes:
*/
float64 CRandomGenerator::RandomFloat64()
{
	// Return a random floating-point value in the [0,1] range
    return (float64)RandomInt64() * FLOAT_SCALE_64;
}

/*******************************************************
* Function: CRandomGenerator::RandomFloat32()
* Purpose : Generate a random 32 bit float
* Initial : Max Payne on July 19, 2005
********************************************************
Revisions and bug fixes:
*/
float32 CRandomGenerator::RandomFloat32()
{
	// Return a random floating-point value in the [0,1] range
    return (float32)RandomInt32() * FLOAT_SCALE_32;
}

random.h

/*******************************************************
* Class   : CRandomGenerator
* Purpose : Seeded pseudo-random number generator
* Initial : Max Payne on July 19, 2005
********************************************************
Revisions and bug fixes:
*/
class CRandomGenerator
{
public:

    // Constructor and destructor
    CRandomGenerator();
   ~CRandomGenerator();

    // Method to set a 32bit random seed
    void SetSeed(uint32 Seed);

    // Method to compute a 64bit random integer (random bit string)
    uint64 RandomInt64();

    // Method to compute a 32bit random integer (random bit string)
    uint32 RandomInt32();

    // Method to compute a 64bit random float in the [0, 1] range
    float64 RandomFloat64();

    // Method to compute a 32bit random float in the [0, 1] range
    float32 RandomFloat32();

private:

    // Constants for 64 bit random values
    // Xn+1 = A * Xn + B (mod 2^64)
    static const uint64 A_CONSTANT_64;
    static const uint64 B_CONSTANT_64;

    // Constants for 32 bit random values
    // Xn+1 = A * Xn + B (mod 2^32)
    static const uint32 A_CONSTANT_32;
    static const uint32 B_CONSTANT_32;

    // Maximum integer values
    static const uint64 MAX_INT_64;
    static const uint32 MAX_INT_32;

    // Scaling values for random float generations
    static const float64 FLOAT_SCALE_64;
    static const float32 FLOAT_SCALE_32;

    // Random seed union
    union URandomSeed
    {
		    // 64 bit random seed
        uint64 Int64;

    		// 32 bit random seed
        uint32 Int32;
    };

	// Random seed object
	URandomSeed m_Seed;
};