fmt_xlonglong - write a hexadecimal ASCII representation of an unsigned long long integer

       fmt_xlonglong  writes  an ASCII representation ('0' to '9' and 'a' to 'f', base 16) of source to dest and
       returns the number of bytes written.

       fmt_xlonglong does not append \0.

       If dest equals FMT_LEN (i.e. is zero), fmt_xlonglong returns the number of bytes it would have written.

       For convenience, fmt.h defines the  integer  FMT_XLONG  to  be  big  enough  to  contain  every  possible
       fmt_xlonglong output plus \0.

       fmt_xlonglong - write a hexadecimal ASCII representation of an unsigned long long integer

scan_xlonglong(3)

                                                                                                fmt_xlonglong(3)

#include<libowfat/fmt.h>

       size_t fmt_xlonglong(char *dest,unsigned long long source);