src/math/trunc.c

   1 #include "libm.h"
   2
   3 double trunc(double x)
   4 {
   5         union {double f; uint64_t i;} u = {x};
   6         int e = (int)(u.i >> 52 & 0x7ff) - 0x3ff + 12;
   7         uint64_t m;
   8
   9         if (e >= 52 + 12)
  10                 return x;
  11         if (e < 12)
  12                 e = 1;
  13         m = -1ULL >> e;
  14         if ((u.i & m) == 0)
  15                 return x;
  16         FORCE_EVAL(x + 0x1p120f);
  17         u.i &= ~m;
  18         return u.f;
  19 }