fusl/src/math/modff.c

#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;
}