fusl/src/math/rintf.c

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

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

float rintf(float x) {
  union {
    float f;
    uint32_t i;
  } u = {x};
  int e = u.i >> 23 & 0xff;
  int s = u.i >> 31;
  float_t y;

  if (e >= 0x7f + 23)
    return x;
  if (s)
    y = x - toint + toint;
  else
    y = x + toint - toint;
  if (y == 0)
    return s ? -0.0f : 0.0f;
  return y;
}