source: azure_iot_hub/trunk/musl-1.1.18/src/math/modff.c@ 389

#include "libm.h"

float modff(float x, float *iptr)
{
        union {float f; uint32_t i;} u = {x};
        uint32_t mask;
        int e = (int)(u.i>>23 & 0xff) - 0x7f;

        /* no fractional part */
        if (e >= 23) {
                *iptr = x;
                if (e == 0x80 && u.i<<9 != 0) { /* nan */
                        return x;
                }
                u.i &= 0x80000000;
                return u.f;
        }
        /* no integral part */
        if (e < 0) {
                u.i &= 0x80000000;
                *iptr = u.f;
                return x;
        }

        mask = 0x007fffff>>e;
        if ((u.i & mask) == 0) {
                *iptr = x;
                u.i &= 0x80000000;
                return u.f;
        }
        u.i &= ~mask;
        *iptr = u.f;
        return x - u.f;
}