math: rewrite remainder functions (remainder, remquo, fmod, modf)

[musl] / src / math / rint.c

#include <math.h>
#include <stdint.h>

double rint(double x)
{
        union {double f; uint64_t i;} u = {x};
        int e = u.i>>52 & 0x7ff;
        int s = u.i>>63;
        double_t y;

        if (e >= 0x3ff+52)
                return x;
        if (s)
                y = (double)(x - 0x1p52) + 0x1p52;
        else
                y = (double)(x + 0x1p52) - 0x1p52;
        if (y == 0)
                return s ? -0.0 : 0;
        return y;
}