inline bool safe_parse_sign_and_base()

in absl/strings/numbers.cc [633:700]

• 55 lines of code
• 26 McCabe index (conditional complexity)

inline bool safe_parse_sign_and_base(absl::string_view* text /*inout*/,
                                     int* base_ptr /*inout*/,
                                     bool* negative_ptr /*output*/) {
  if (text->data() == nullptr) {
    return false;
  }

  const char* start = text->data();
  const char* end = start + text->size();
  int base = *base_ptr;

  // Consume whitespace.
  while (start < end && absl::ascii_isspace(start[0])) {
    ++start;
  }
  while (start < end && absl::ascii_isspace(end[-1])) {
    --end;
  }
  if (start >= end) {
    return false;
  }

  // Consume sign.
  *negative_ptr = (start[0] == '-');
  if (*negative_ptr || start[0] == '+') {
    ++start;
    if (start >= end) {
      return false;
    }
  }

  // Consume base-dependent prefix.
  //  base 0: "0x" -> base 16, "0" -> base 8, default -> base 10
  //  base 16: "0x" -> base 16
  // Also validate the base.
  if (base == 0) {
    if (end - start >= 2 && start[0] == '0' &&
        (start[1] == 'x' || start[1] == 'X')) {
      base = 16;
      start += 2;
      if (start >= end) {
        // "0x" with no digits after is invalid.
        return false;
      }
    } else if (end - start >= 1 && start[0] == '0') {
      base = 8;
      start += 1;
    } else {
      base = 10;
    }
  } else if (base == 16) {
    if (end - start >= 2 && start[0] == '0' &&
        (start[1] == 'x' || start[1] == 'X')) {
      start += 2;
      if (start >= end) {
        // "0x" with no digits after is invalid.
        return false;
      }
    }
  } else if (base >= 2 && base <= 36) {
    // okay
  } else {
    return false;
  }
  *text = absl::string_view(start, end - start);
  *base_ptr = base;
  return true;
}