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

     1  #include "libm.h"
     2  
     3  #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
     4  long double truncl(long double x)
     5  {
     6  	return trunc(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 truncl(long double x)
    13  {
    14  	union ldshape u = {x};
    15  	int e = u.i.se & 0x7fff;
    16  	int s = u.i.se >> 15;
    17  	long double y;
    18  
    19  	if (e >= 0x3fff+LDBL_MANT_DIG-1)
    20  		return x;
    21  	if (e <= 0x3fff-1) {
    22  		FORCE_EVAL(x + 0x1p120f);
    23  		return x*0;
    24  	}
    25  	/* y = int(|x|) - |x|, where int(|x|) is an integer neighbor of |x| */
    26  	if (s)
    27  		x = -x;
    28  	y = x + toint - toint - x;
    29  	if (y > 0)
    30  		y -= 1;
    31  	x += y;
    32  	return s ? -x : x;
    33  }
    34  #endif