Class MergedRunsIterator

cpp/src/arrow/util/ree_util.h:439–581

/// of this iterator only hold references to the RunEndEncodedArraySpan inputs.
template <typename Left, typename Right>
class MergedRunsIterator {
 private:
  using LeftIterator = typename Left::Iterator;
  using RightIterator = typename Right::Iterator;

  MergedRunsIterator(LeftIterator left_it, RightIterator right_it,
                     int64_t common_logical_length, int64_t common_logical_pos)
      : ree_iterators_{std::move(left_it), std::move(right_it)},
        logical_length_(common_logical_length),
        logical_pos_(common_logical_pos) {}

 public:
  /// \brief Construct a MergedRunsIterator positioned at logical position 0.
  ///
  /// Pre-condition: left.length() == right.length()
  MergedRunsIterator(const Left& left, const Right& right)
      : MergedRunsIterator(left.begin(), right.begin(), left.length(), 0) {
    assert(left.length() == right.length());
  }

  static Result<MergedRunsIterator> MakeBegin(const Left& left, const Right& right) {
    if (left.length() != right.length()) {
      return Status::Invalid(
          "MergedRunsIterator expects RunEndEncodedArraySpans of the same length");
    }
    return MergedRunsIterator(left, right);
  }

  static Result<MergedRunsIterator> MakeEnd(const Left& left, const Right& right) {
    if (left.length() != right.length()) {
      return Status::Invalid(
          "MergedRunsIterator expects RunEndEncodedArraySpans of the same length");
    }
    return MergedRunsIterator(left.end(), right.end(), left.length(), left.length());
  }

  /// \brief Return the left RunEndEncodedArraySpan child
  const Left& left() const { return std::get<0>(ree_iterators_).span; }

  /// \brief Return the right RunEndEncodedArraySpan child
  const Right& right() const { return std::get<1>(ree_iterators_).span; }

  /// \brief Return the initial logical position of the run
  ///
  /// If is_end(), this is the same as length().
  int64_t logical_position() const { return logical_pos_; }

  /// \brief Whether the iterator is at logical position 0.
  bool is_begin() const { return logical_pos_ == 0; }

  /// \brief Whether the iterator has reached the end of both arrays
  bool is_end() const { return logical_pos_ == logical_length_; }

  /// \brief Return the logical position immediately after the run.
  ///
  /// Pre-condition: !is_end()
  int64_t run_end() const {
    const auto& left_it = std::get<0>(ree_iterators_);