github.com/afumu/libc@v0.0.6/musl/src/math/rint.c (about)

     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  }