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

     1  #include <math.h>
     2  #include <stdint.h>
     3  
     4  double frexp(double x, int *e)
     5  {
     6  	union { double d; uint64_t i; } y = { x };
     7  	int ee = y.i>>52 & 0x7ff;
     8  
     9  	if (!ee) {
    10  		if (x) {
    11  			x = frexp(x*0x1p64, e);
    12  			*e -= 64;
    13  		} else *e = 0;
    14  		return x;
    15  	} else if (ee == 0x7ff) {
    16  		return x;
    17  	}
    18  
    19  	*e = ee - 0x3fe;
    20  	y.i &= 0x800fffffffffffffull;
    21  	y.i |= 0x3fe0000000000000ull;
    22  	return y.d;
    23  }