rint.c raw

   1  #include <float.h>
   2  #include <math.h>
   3  #include <stdint.h>
   4  
   5  #if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1
   6  #define EPS DBL_EPSILON
   7  #elif FLT_EVAL_METHOD==2
   8  #define EPS LDBL_EPSILON
   9  #endif
  10  static const double_t toint = 1/EPS;
  11  
  12  double rint(double x)
  13  {
  14  	union {double f; uint64_t i;} u = {x};
  15  	int e = u.i>>52 & 0x7ff;
  16  	int s = u.i>>63;
  17  	double_t y;
  18  
  19  	if (e >= 0x3ff+52)
  20  		return x;
  21  	if (s)
  22  		y = x - toint + toint;
  23  	else
  24  		y = x + toint - toint;
  25  	if (y == 0)
  26  		return s ? -0.0 : 0;
  27  	return y;
  28  }
  29