char-charsetchar-charset is a built-in function in `
C source code'. (char-charset CH &optional RESTRICTION) Return the charset of highest priority that contains CH. ASCII characters are an exception: for them, this function always returns `ascii'. If optional 2nd arg RESTRICTION is non-nil, it is a list of charsets from which to find the charset. It may also be a coding system. In that case, find the charset from what supported by that coding system.