src/math/rint.c

   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 }