Class RangeIterator

cpp/src/arrow/util/iterator.h:150–186

  explicit operator bool() const { return ptr_ != NULLPTR; }

  class RangeIterator {
   public:
    RangeIterator() : value_(IterationTraits<T>::End()) {}

    explicit RangeIterator(Iterator i)
        : value_(IterationTraits<T>::End()),
          iterator_(std::make_shared<Iterator>(std::move(i))) {
      Next();
    }

    bool operator!=(const RangeIterator& other) const { return value_ != other.value_; }

    RangeIterator& operator++() {
      Next();
      return *this;
    }

    Result<T> operator*() {
      ARROW_RETURN_NOT_OK(value_);

      auto value = std::move(value_);
      value_ = IterationTraits<T>::End();
      return value;
    }

   private:
    void Next() {
      if (!value_.ok()) {
        value_ = IterationTraits<T>::End();
        return;
      }
      value_ = iterator_->Next();
    }

    Result<T> value_;
    std::shared_ptr<Iterator> iterator_;
  };

  RangeIterator begin() { return RangeIterator(std::move(*this)); }