Class Iterator

cpp/src/arrow/util/ree_util.h:245–324

  /// \brief Iterator representing the current run during iteration over a
  /// run-end encoded array
  class Iterator {
   public:
    Iterator(PrivateTag, const RunEndEncodedArraySpan& span, int64_t logical_pos,
             int64_t physical_pos)
        : span(span), logical_pos_(logical_pos), physical_pos_(physical_pos) {}

    /// \brief Return the physical index of the run
    ///
    /// The values array can be addressed with this index to get the value
    /// that makes up the run.
    ///
    /// NOTE: if this Iterator is equal to RunEndEncodedArraySpan::end(),
    /// the value returned is undefined.
    int64_t index_into_array() const { return physical_pos_; }

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

    /// \brief Return the logical position immediately after the run.
    ///
    /// Pre-condition: *this != RunEndEncodedArraySpan::end()
    int64_t run_end() const { return span.run_end(physical_pos_); }

    /// \brief Returns the logical length of the run.
    ///
    /// Pre-condition: *this != RunEndEncodedArraySpan::end()
    int64_t run_length() const { return run_end() - logical_pos_; }

    /// \brief Check if the iterator is at the end of the array.
    ///
    /// This can be used to avoid paying the cost of a call to
    /// RunEndEncodedArraySpan::end().
    ///
    /// \return true if the iterator is at the end of the array
    bool is_end(const RunEndEncodedArraySpan& span) const {
      return logical_pos_ >= span.length();
    }

    Iterator& operator++() {
      logical_pos_ = span.run_end(physical_pos_);
      physical_pos_ += 1;
      return *this;
    }

    Iterator operator++(int) {
      const Iterator prev = *this;
      ++(*this);
      return prev;
    }

    Iterator& operator--() {
      physical_pos_ -= 1;
      logical_pos_ = (physical_pos_ > 0) ? span.run_end(physical_pos_ - 1) : 0;
      return *this;
    }