xdigit_value

Determines the numeric value of a character as a hexadecimal digit.

If the character is not a hex digit according to [func@GLib.ascii_isxdigit], `-1` is returned.

Differs from [func@GLib.unichar_xdigit_value] because it takes a char, so there's no worry about sign extension if characters are signed.

Differs from [func@GLib.unichar_xdigit_value] because it takes a char, so there's no worry about sign extension if characters are signed.

Parameters:

c	an ASCII character

Returns:

the numerical value of c if it is a hex digit, `-1` otherwise