| 18 | */ |
| 19 | template <typename C> |
| 20 | class flat_iterator |
| 21 | { |
| 22 | public: |
| 23 | using value_type = typename C::const_iterator::value_type; |
| 24 | using reference = typename C::const_iterator::reference; |
| 25 | using pointer = value_type*; |
| 26 | using difference_type = int64_t; |
| 27 | using iterator_category = std::random_access_iterator_tag; |
| 28 | |
| 29 | static flat_iterator begin(const std::vector<C>& containers, const std::vector<value_type>& offsets) |
| 30 | { |
| 31 | if (containers.empty()) { |
| 32 | return flat_iterator(); |
| 33 | } |
| 34 | return flat_iterator(containers, offsets, containers.begin(), containers.begin()->begin()); |
| 35 | } |
| 36 | |
| 37 | static flat_iterator end(const std::vector<C>& containers, const std::vector<value_type>& offsets) |
| 38 | { |
| 39 | if (containers.empty()) { |
| 40 | return flat_iterator(); |
| 41 | } |
| 42 | return flat_iterator(containers, offsets, containers.end() - 1, containers.back().end()); |
| 43 | } |
| 44 | |
| 45 | reference operator*() const |
| 46 | { |
| 47 | return *child_iterator_; |
| 48 | } |
| 49 | |
| 50 | flat_iterator& operator++() |
| 51 | { |
| 52 | ++child_iterator_; |
| 53 | skip_empty_containers(); |
| 54 | return *this; |
| 55 | } |
| 56 | |
| 57 | flat_iterator operator++(int) |
| 58 | { |
| 59 | flat_iterator tmp = *this; |
| 60 | ++*this; |
| 61 | return tmp; |
| 62 | } |
| 63 | |
| 64 | flat_iterator& operator--() |
| 65 | { |
| 66 | while (child_iterator_ == parent_iterator_->begin() && parent_iterator_ != containers_->begin()) { |
| 67 | --parent_iterator_; |
| 68 | child_iterator_ = parent_iterator_->end(); |
| 69 | } |
| 70 | --child_iterator_; |
| 71 | return *this; |
| 72 | } |
| 73 | |
| 74 | flat_iterator operator--(int) |
| 75 | { |
| 76 | flat_iterator tmp = *this; |
| 77 | --*this; |