bool isUtf8()

in prod/native/libcommon/code/CommonUtils.cpp [295:339]

• 35 lines of code
• 22 McCabe index (conditional complexity)

bool isUtf8(std::string_view input) {
    const uint8_t *p = reinterpret_cast<const uint8_t *>(input.data());
    size_t length = input.size();

    static constexpr uint8_t utf8_table[] = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3};

    while (length > 0) {
        uint32_t d;
        uint8_t c = *p++;
        length--;

        if (c < 0x80)
            continue;

        if (c < 0xC0 || c >= 0xF5)
            return false;

        uint8_t ab = utf8_table[c & 0x3F];
        if (length < ab)
            return false;
        length -= ab;

        if (((d = *p++) & 0xC0) != 0x80)
            return false;

        switch (ab) {
            case 1:
                if ((c & 0x3E) == 0)
                    return false;
                break;

            case 2:
                if ((*p++ & 0xC0) != 0x80 || (c == 0xE0 && (d & 0x20) == 0) || (c == 0xED && d >= 0xA0))
                    return false;
                break;

            case 3:
                if ((*p++ & 0xC0) != 0x80 || (*p++ & 0xC0) != 0x80 || (c == 0xF0 && (d & 0x30) == 0) || (c > 0xF4 || (c == 0xF4 && d > 0x8F)))
                    return false;
                break;
        }
    }

    return true;
}