| 15 | typename T |
| 16 | > |
| 17 | class weak_ptr |
| 18 | { |
| 19 | |
| 20 | /*! |
| 21 | CONVENTION |
| 22 | - if (weak_node != 0) then |
| 23 | - data == valid pointer to shared data |
| 24 | - weak_node->ref_count == the number of weak_ptrs that reference this->data |
| 25 | - else |
| 26 | - data == 0 |
| 27 | |
| 28 | - expired() == ((weak_node == 0) || (weak_node->shared_node == 0)) |
| 29 | - if (expired() == false) then |
| 30 | - use_count() == weak_node->shared_node->ref_count |
| 31 | - else |
| 32 | - use_count() == 0 |
| 33 | !*/ |
| 34 | |
| 35 | public: |
| 36 | typedef T element_type; |
| 37 | |
| 38 | weak_ptr( |
| 39 | ) : data(0), weak_node(0) |
| 40 | { |
| 41 | } |
| 42 | |
| 43 | template<typename Y> |
| 44 | weak_ptr( |
| 45 | const shared_ptr<Y>& r |
| 46 | ) |
| 47 | { |
| 48 | data = r.data; |
| 49 | if (r.shared_node) |
| 50 | { |
| 51 | if (r.shared_node->weak_node) |
| 52 | { |
| 53 | weak_node = r.shared_node->weak_node; |
| 54 | weak_node->ref_count += 1; |
| 55 | } |
| 56 | else |
| 57 | { |
| 58 | weak_node = new weak_ptr_node(r.shared_node); |
| 59 | r.shared_node->weak_node = weak_node; |
| 60 | } |
| 61 | } |
| 62 | else |
| 63 | { |
| 64 | weak_node = 0; |
| 65 | } |
| 66 | } |
| 67 | |
| 68 | weak_ptr( |
| 69 | const weak_ptr& r |
| 70 | ) |
| 71 | { |
| 72 | data = r.data; |
| 73 | weak_node = r.weak_node; |
| 74 | if (weak_node) |