Double decimal number convert to HEX string

Question

I want to convert a decimal number(17592186044416) to hex string in MFC. AndI have tried to use

code 1:
double ftw = 0;
CString str;
str.Format(_T("%X"), ftw); //this will always be 0 in HEX

code 2:
char t1[100];
_itoa_s(ftw, t1, 16);// this will give me 80000000 in HEX

It seems like the str.Format(_T("%X"), ftw); and _itoa_s(ftw, t1, 16); function has the limit. Is there any other command that I can use to get the 17592186044416 to hex string? Thank you.

Answer 1

You can cast it to a 64-bit integer and then format using the I64 qualifier in your format string:

double ftw = 17592186044416.0;

CString str;
str.Format(_T("%I64X"), (__int64)ftw);

For the example above, str will have the string "100000000000"