static inline bool InlinedNullLookup()

in cpp/src/arrow/util/trie_benchmark.cc [89:189]

• 90 lines of code
• 59 McCabe index (conditional complexity)

static inline bool InlinedNullLookup(std::string_view s) {
  // An inlined version of trie lookup for a specific set of strings
  // (see AllNulls())
  auto size = s.length();
  auto data = s.data();
  if (size == 0) {
    return false;
  }
  if (size == 1) {
    return false;
  }

  auto chars = reinterpret_cast<const char*>(data);
  auto first = chars[0];
  auto second = chars[1];
  switch (first) {
    case 'N': {
      // "NA", "N/A", "NaN", "NULL"
      if (size == 2) {
        return second == 'A';
      }
      auto third = chars[2];
      if (size == 3) {
        return (second == '/' && third == 'A') || (second == 'a' && third == 'N');
      }
      if (size == 4) {
        return (second == 'U' && third == 'L' && chars[3] == 'L');
      }
      return false;
    }
    case 'n': {
      // "n/a", "nan", "null"
      if (size == 2) {
        return false;
      }
      auto third = chars[2];
      if (size == 3) {
        return (second == '/' && third == 'a') || (second == 'a' && third == 'n');
      }
      if (size == 4) {
        return (second == 'u' && third == 'l' && chars[3] == 'l');
      }
      return false;
    }
    case '1': {
      // '1.#IND', '1.#QNAN'
      if (size == 6) {
        // '#' is the most unlikely char here, check it first
        return (chars[2] == '#' && chars[1] == '.' && chars[3] == 'I' &&
                chars[4] == 'N' && chars[5] == 'D');
      }
      if (size == 7) {
        return (chars[2] == '#' && chars[1] == '.' && chars[3] == 'Q' &&
                chars[4] == 'N' && chars[5] == 'A' && chars[6] == 'N');
      }
      return false;
    }
    case '-': {
      switch (second) {
        case 'N':
          // "-NaN"
          return (size == 4 && chars[2] == 'a' && chars[3] == 'N');
        case 'n':
          // "-nan"
          return (size == 4 && chars[2] == 'a' && chars[3] == 'n');
        case '1':
          // "-1.#IND", "-1.#QNAN"
          if (size == 7) {
            return (chars[3] == '#' && chars[2] == '.' && chars[4] == 'I' &&
                    chars[5] == 'N' && chars[6] == 'D');
          }
          if (size == 8) {
            return (chars[3] == '#' && chars[2] == '.' && chars[4] == 'Q' &&
                    chars[5] == 'N' && chars[6] == 'A' && chars[7] == 'N');
          }
          return false;
        default:
          return false;
      }
    }
    case '#': {
      // "#N/A", "#N/A N/A", "#NA"
      if (size < 3 || chars[1] != 'N') {
        return false;
      }
      auto third = chars[2];
      if (size == 3) {
        return third == 'A';
      }
      if (size == 4) {
        return third == '/' && chars[3] == 'A';
      }
      if (size == 8) {
        return std::memcmp(data + 2, "/A N/A", 5) == 0;
      }
      return false;
    }
    default:
      return false;
  }
}