Determines whether a character is a hexadecimal-digit character.
Unlike the standard C library isxdigit() function,
this takes a char, not an int, so
don't call it on EOF but no need to cast to guchar before passing a
possibly non-ASCII character in.
Determines whether a character is a hexadecimal-digit character. Unlike the standard C library isxdigit() function, this takes a char, not an int, so don't call it on EOF but no need to cast to guchar before passing a possibly non-ASCII character in.