Determines the numeric value of a character as a hexadecimal digit. Differs from g_unichar_xdigit_value() because it takes a char, so there's no worry about sign extension if characters are signed.
an ASCII character.
If @c is a hex digit (according to g_ascii_isxdigit()), its numeric value. Otherwise, -1.
See Implementation
Determines the numeric value of a character as a hexadecimal digit. Differs from g_unichar_xdigit_value() because it takes a char, so there's no worry about sign extension if characters are signed.