drand48.h

#include <math.h>

#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;

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);
}

double drand48(){
	return erand48(_rand48_seed);
}

void srand48(long seed){
	_rand48_seed[0] = RAND48_SEED_0;
	_rand48_seed[1] = (unsigned short)seed;
	_rand48_seed[2] = (unsigned short)(seed >> 16);
	_rand48_mult[0] = RAND48_MULT_0;
	_rand48_mult[1] = RAND48_MULT_1;
	_rand48_mult[2] = RAND48_MULT_2;
	_rand48_add = RAND48_ADD;
}