randStuff.h

#pragma once

#define	RAND48_SEED_0	(0x330e)
#define	RAND48_SEED_1	(0xabcd)
#define	RAND48_SEED_2	(0x1234)
#define	RAND48_MULT_0	(0xe66d)
#define	RAND48_MULT_1	(0xdeec)
#define	RAND48_MULT_2	(0x0005)
#define	RAND48_ADD	(0x000b)

unsigned short __rand48_Seed[3] = {
	RAND48_SEED_0,
	RAND48_SEED_1,
	RAND48_SEED_2
};

unsigned short __rand48_Mult[3] = {
	RAND48_MULT_0,
	RAND48_MULT_1,
	RAND48_MULT_2
};

unsigned short __rand48_Add = RAND48_ADD;

static void _dorand48(unsigned short xseed[3])
{
	unsigned long accu;
	unsigned short temp[2];

	accu = (unsigned long) __rand48_Mult[0] * (unsigned long) xseed[0] + (unsigned long) __rand48_Add;
	temp[0] = (unsigned short) accu;	/* lower 16 bits */
	accu >>= sizeof(unsigned short) * 8;
	accu += (unsigned long) __rand48_Mult[0] * (unsigned long) xseed[1] + (unsigned long) __rand48_Mult[1] * (unsigned long) xseed[0];
	temp[1] = (unsigned short) accu;	/* middle 16 bits */
	accu >>= sizeof(unsigned short) * 8;
	accu += __rand48_Mult[0] * xseed[2] + __rand48_Mult[1] * xseed[1] +	__rand48_Mult[2] * xseed[0];
	xseed[0] = temp[0];
	xseed[1] = temp[1];
	xseed[2] = (unsigned short) accu;
}

double	erand48(unsigned short xseed[3])
{
	_dorand48(xseed);
	return ldexp((double) xseed[0], -48) + ldexp((double) xseed[1], -32) + ldexp((double) xseed[2], -16);
}