source: trunk/sys/dietlibc/rand48.c @ 303

#include <stdlib.h>

static randbuf rand48buf;
#define A_0  0xE66D
#define A_1  0xDEEC
#define A_2  0x5
#define C 0xB
static randbuf a = { A_0, A_1, A_2 };
static unsigned short c = C;

static void calc_next(randbuf buf) {
        randbuf tmp;
        long t;
        t = buf[0] * a[0] + c;
        tmp[0] = t & 0xffff;
        tmp[1] = (t >> 16) & 0xffff;
        t = buf[1] * a[0] + buf[0] * a[1] + tmp[1];
        tmp[1] = t & 0xffff;
        tmp[2] = (t >> 16) & 0xffff;
        t = buf[2] * a[0] + buf[1] * a[1] + buf[0] * a[2] + tmp[2];
        tmp[2] = t & 0xffff;
        buf[0] = tmp[0];
        buf[1] = tmp[1];
        buf[2] = tmp[2];
}


long lrand48(void) {
        return nrand48(rand48buf);
}

long mrand48(void) {
        return jrand48(rand48buf);
}

double drand48(void) {
        return frand48(rand48buf);
}

void srand48(long seed) {
        rand48buf[1] = (seed >> 16) & 0xffff;
        rand48buf[2] = seed & 0xffff;
        rand48buf[0] = 0x330e;
        a[0] = A_0;
        a[1] = A_1;
        a[2] = A_2;
        c = C;
}


double frand48(randbuf buf) {
        double ret;
        static double two16m = 1.0 / (1L << 16);
        ret = (two16m * (two16m * (two16m * buf[0] + buf[1]) + buf[2]));
        calc_next(buf);
        return ret;
}



unsigned short *seed48(randbuf buf) {
        static randbuf oldx;
        int i;
        for (i = 0; i < 3; i++) {
                oldx[i] = rand48buf[i];
                rand48buf[i] = buf[i];
        }
        a[0] = A_0;
        a[1] = A_1;
        a[2] = A_2;
        c = C;
        return (unsigned short *)&oldx;
}

void lcong48(unsigned short param[7]) {
        int i;
        for (i = 0; i < 3; i++) {
                rand48buf[i] = param[i];
                a[i] = param[i + 3];
        }
        c = param[6];
}

long jrand48(randbuf buf) {
        long ret;
        ret = buf[2] << 16 | buf[1];
        calc_next(buf);
        return ret;
}

long nrand48(randbuf buf) {
        return jrand48(buf) & 0x7FFFFFFFL;
}