src/math/ceil.c

   1 #include "libm.h"
   2
   3 #if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1
   4 #define EPS DBL_EPSILON
   5 #elif FLT_EVAL_METHOD==2
   6 #define EPS LDBL_EPSILON
   7 #endif
   8 static const double_t toint = 1/EPS;
   9
  10 double ceil(double x)
  11 {
  12         union {double f; uint64_t i;} u = {x};
  13         int e = u.i >> 52 & 0x7ff;
  14         double_t y;
  15
  16         if (e >= 0x3ff+52 || x == 0)
  17                 return x;
  18         /* y = int(x) - x, where int(x) is an integer neighbor of x */
  19         if (u.i >> 63)
  20                 y = x - toint + toint - x;
  21         else
  22                 y = x + toint - toint - x;
  23         /* special case because of non-nearest rounding modes */
  24         if (e <= 0x3ff-1) {
  25                 FORCE_EVAL(y);
  26                 return u.i >> 63 ? -0.0 : 1;
  27         }
  28         if (y < 0)
  29                 return x + y + 1;
  30         return x + y;
  31 }