valid_b1(
b1) ->ok
Check if a byte is a valid starting byte for a multi-byte UTF-8 sequence
A valid leading byte falls in the range 0xC2–0xF4. Bytes 0xC0 and 0xC1 are excluded because they would produce overlong encodings. Bytes 0xF5 and above are outside the Unicode range. ASCII bytes (< 0x80) and continuation bytes (0x80–0xBF) also return false.