Method Call

cpp/src/arrow/compute/kernels/scalar_string_utf8.cc:255–288

struct IsTitleUnicode {
  static bool Call(KernelContext*, const uint8_t* input, size_t input_string_ncodeunits,
                   Status* st) {
    // rules:
    //   1. lower case follows cased
    //   2. upper case follows uncased
    //   3. at least 1 cased character (which logically should be upper/title)
    bool rules_1_and_2;
    bool previous_cased = false;  // in LL, LU or LT
    bool rule_3 = false;
    bool status =
        arrow::util::UTF8AllOf(input, input + input_string_ncodeunits, &rules_1_and_2,
                               [&previous_cased, &rule_3](uint32_t codepoint) {
                                 if (IsLowerCaseCharacterUnicode(codepoint)) {
                                   if (!previous_cased) return false;  // rule 1 broken
                                   // next should be more lower case or uncased
                                   previous_cased = true;
                                 } else if (IsCasedCharacterUnicode(codepoint)) {
                                   if (previous_cased) return false;  // rule 2 broken
                                   // next should be a lower case or uncased
                                   previous_cased = true;
                                   rule_3 = true;  // rule 3 obeyed
                                 } else {
                                   // an uncased char, like _ or 1
                                   // next should be upper case or more uncased
                                   previous_cased = false;
                                 }
                                 return true;
                               });
    if (!ARROW_PREDICT_TRUE(status)) {
      *st = Status::Invalid("Invalid UTF8 sequence in input");
      return false;
    }
    return rules_1_and_2 & rule_3;
  }
};

struct IsUpperUnicode : CharacterPredicateUnicode<IsUpperUnicode> {