source: asp3_tinet_ecnl_rx/trunk/musl-1.1.18/src/math/modf.c@ 337

#include "libm.h"

double modf(double x, double *iptr)
{
        union {double f; uint64_t i;} u = {x};
        uint64_t mask;
        int e = (int)(u.i>>52 & 0x7ff) - 0x3ff;

        /* no fractional part */
        if (e >= 52) {
                *iptr = x;
                if (e == 0x400 && u.i<<12 != 0) /* nan */
                        return x;
                u.i &= 1ULL<<63;
                return u.f;
        }

        /* no integral part*/
        if (e < 0) {
                u.i &= 1ULL<<63;
                *iptr = u.f;
                return x;
        }

        mask = -1ULL>>12>>e;
        if ((u.i & mask) == 0) {
                *iptr = x;
                u.i &= 1ULL<<63;
                return u.f;
        }
        u.i &= ~mask;
        *iptr = u.f;
        return x - u.f;
}