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

     1  #include "libm.h"
     2  
     3  #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
     4  long double modfl(long double x, long double *iptr)
     5  {
     6  	double d;
     7  	long double r;
     8  
     9  	r = modf(x, &d);
    10  	*iptr = d;
    11  	return r;
    12  }
    13  #elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
    14  
    15  static const long double toint = 1/LDBL_EPSILON;
    16  
    17  long double modfl(long double x, long double *iptr)
    18  {
    19  	union ldshape u = {x};
    20  	int e = (u.i.se & 0x7fff) - 0x3fff;
    21  	int s = u.i.se >> 15;
    22  	long double absx;
    23  	long double y;
    24  
    25  	/* no fractional part */
    26  	if (e >= LDBL_MANT_DIG-1) {
    27  		*iptr = x;
    28  		if (isnan(x))
    29  			return x;
    30  		return s ? -0.0 : 0.0;
    31  	}
    32  
    33  	/* no integral part*/
    34  	if (e < 0) {
    35  		*iptr = s ? -0.0 : 0.0;
    36  		return x;
    37  	}
    38  
    39  	/* raises spurious inexact */
    40  	absx = s ? -x : x;
    41  	y = absx + toint - toint - absx;
    42  	if (y == 0) {
    43  		*iptr = x;
    44  		return s ? -0.0 : 0.0;
    45  	}
    46  	if (y > 0)
    47  		y -= 1;
    48  	if (s)
    49  		y = -y;
    50  	*iptr = x + y;
    51  	return -y;
    52  }
    53  #endif