third_party/ulib/musl/src/math/rint.c

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

#if FLT_EVAL_METHOD == 0 || FLT_EVAL_METHOD == 1
#define EPS DBL_EPSILON
#elif FLT_EVAL_METHOD == 2
#define EPS LDBL_EPSILON
#endif
static const double_t toint = 1 / EPS;

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 = x - toint + toint;
    else
        y = x + toint - toint;
    if (y == 0)
        return s ? -0.0 : 0;
    return y;
}