inline bool is_valid_utf8()

in serde-generate/runtime/cpp/binary.hpp [218:246]

• 23 lines of code
• 8 McCabe index (conditional complexity)

inline bool is_valid_utf8(const std::string &input) {
    uint8_t trailing_digits = 0;
    for (uint8_t byte : input) {
        if (trailing_digits == 0) {
            // Start new codepoint.
            if (byte >> 7 == 0) {
                // ASCII character
            } else if (byte >> 5 == 0b110) {
                // Expecting a 2-byte codepoint
                trailing_digits = 1;
            } else if (byte >> 4 == 0b1110) {
                // Expecting a 3-byte codepoint
                trailing_digits = 2;
            } else if (byte >> 3 == 0b11110) {
                // Expecting a 4-byte codepoint
                trailing_digits = 3;
            } else {
                return false;
            }
        } else {
            // Process "trailing digit".
            if (byte >> 6 != 0b10) {
                return false;
            }
            trailing_digits -= 1;
        }
    }
    return trailing_digits == 0;
}