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

     1  #include "libm.h"
     2  
     3  #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
     4  long double roundl(long double x)
     5  {
     6  	return round(x);
     7  }
     8  #elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
     9  
    10  static const long double toint = 1/LDBL_EPSILON;
    11  
    12  long double roundl(long double x)
    13  {
    14  	union ldshape u = {x};
    15  	int e = u.i.se & 0x7fff;
    16  	long double y;
    17  
    18  	if (e >= 0x3fff+LDBL_MANT_DIG-1)
    19  		return x;
    20  	if (u.i.se >> 15)
    21  		x = -x;
    22  	if (e < 0x3fff-1) {
    23  		FORCE_EVAL(x + toint);
    24  		return 0*u.f;
    25  	}
    26  	y = x + toint - toint - x;
    27  	if (y > 0.5)
    28  		y = y + x - 1;
    29  	else if (y <= -0.5)
    30  		y = y + x + 1;
    31  	else
    32  		y = y + x;
    33  	if (u.i.se >> 15)
    34  		y = -y;
    35  	return y;
    36  }
    37  #endif