. /include/boost/corosio /detail /intrusive.hpp
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1   // 1   //
2   // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com) 2   // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
3   // 3   //
4   // Distributed under the Boost Software License, Version 1.0. (See accompanying 4   // Distributed under the Boost Software License, Version 1.0. (See accompanying
5   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 5   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6   // 6   //
7   // Official repository: https://github.com/cppalliance/corosio 7   // Official repository: https://github.com/cppalliance/corosio
8   // 8   //
9   9  
10   #ifndef BOOST_COROSIO_DETAIL_INTRUSIVE_HPP 10   #ifndef BOOST_COROSIO_DETAIL_INTRUSIVE_HPP
11   #define BOOST_COROSIO_DETAIL_INTRUSIVE_HPP 11   #define BOOST_COROSIO_DETAIL_INTRUSIVE_HPP
12   12  
13   namespace boost::corosio::detail { 13   namespace boost::corosio::detail {
14   14  
15   /** An intrusive doubly linked list. 15   /** An intrusive doubly linked list.
16   16  
17   This container provides O(1) push and pop operations for 17   This container provides O(1) push and pop operations for
18   elements that derive from @ref node. Elements are not 18   elements that derive from @ref node. Elements are not
19   copied or moved; they are linked directly into the list. 19   copied or moved; they are linked directly into the list.
20   20  
21   @tparam T The element type. Must derive from `intrusive_list<T>::node`. 21   @tparam T The element type. Must derive from `intrusive_list<T>::node`.
22   */ 22   */
23   template<class T> 23   template<class T>
24   class intrusive_list 24   class intrusive_list
25   { 25   {
26   public: 26   public:
27   /** Base class for list elements. 27   /** Base class for list elements.
28   28  
29   Derive from this class to make a type usable with 29   Derive from this class to make a type usable with
30   @ref intrusive_list. The `next_` and `prev_` pointers 30   @ref intrusive_list. The `next_` and `prev_` pointers
31   are private and accessible only to the list. 31   are private and accessible only to the list.
32   */ 32   */
33   class node 33   class node
34   { 34   {
35   friend class intrusive_list; 35   friend class intrusive_list;
36   36  
37   private: 37   private:
38   T* next_; 38   T* next_;
39   T* prev_; 39   T* prev_;
40   }; 40   };
41   41  
42   private: 42   private:
43   T* head_ = nullptr; 43   T* head_ = nullptr;
44   T* tail_ = nullptr; 44   T* tail_ = nullptr;
45   45  
46   public: 46   public:
HITCBC 47   6467 intrusive_list() = default; 47   10576 intrusive_list() = default;
48   48  
49   intrusive_list(intrusive_list&& other) noexcept 49   intrusive_list(intrusive_list&& other) noexcept
50   : head_(other.head_) 50   : head_(other.head_)
51   , tail_(other.tail_) 51   , tail_(other.tail_)
52   { 52   {
53   other.head_ = nullptr; 53   other.head_ = nullptr;
54   other.tail_ = nullptr; 54   other.tail_ = nullptr;
55   } 55   }
56   56  
57   intrusive_list(intrusive_list const&) = delete; 57   intrusive_list(intrusive_list const&) = delete;
58   intrusive_list& operator=(intrusive_list const&) = delete; 58   intrusive_list& operator=(intrusive_list const&) = delete;
59   intrusive_list& operator=(intrusive_list&&) = delete; 59   intrusive_list& operator=(intrusive_list&&) = delete;
60   60  
HITCBC 61   32 bool empty() const noexcept 61   38 bool empty() const noexcept
62   { 62   {
HITCBC 63   32 return head_ == nullptr; 63   38 return head_ == nullptr;
64   } 64   }
65   65  
HITCBC 66   41910 void push_back(T* w) noexcept 66   43704 void push_back(T* w) noexcept
67   { 67   {
HITCBC 68   41910 auto* n = static_cast<node*>(w); 68   43704 auto* n = static_cast<node*>(w);
HITCBC 69   41910 n->next_ = nullptr; 69   43704 n->next_ = nullptr;
HITCBC 70   41910 n->prev_ = tail_; 70   43704 n->prev_ = tail_;
HITCBC 71   41910 if (tail_) 71   43704 if (tail_)
HITCBC 72   24281 static_cast<node*>(tail_)->next_ = w; 72   25086 static_cast<node*>(tail_)->next_ = w;
73   else 73   else
HITCBC 74   17629 head_ = w; 74   18618 head_ = w;
HITCBC 75   41910 tail_ = w; 75   43704 tail_ = w;
HITCBC 76   41910 } 76   43704 }
77   77  
78   void splice_back(intrusive_list& other) noexcept 78   void splice_back(intrusive_list& other) noexcept
79   { 79   {
80   if (other.empty()) 80   if (other.empty())
81   return; 81   return;
82   if (tail_) 82   if (tail_)
83   { 83   {
84   static_cast<node*>(tail_)->next_ = other.head_; 84   static_cast<node*>(tail_)->next_ = other.head_;
85   static_cast<node*>(other.head_)->prev_ = tail_; 85   static_cast<node*>(other.head_)->prev_ = tail_;
86   tail_ = other.tail_; 86   tail_ = other.tail_;
87   } 87   }
88   else 88   else
89   { 89   {
90   head_ = other.head_; 90   head_ = other.head_;
91   tail_ = other.tail_; 91   tail_ = other.tail_;
92   } 92   }
93   other.head_ = nullptr; 93   other.head_ = nullptr;
94   other.tail_ = nullptr; 94   other.tail_ = nullptr;
95   } 95   }
96   96  
HITCBC 97   185216 T* pop_front() noexcept 97   285019 T* pop_front() noexcept
98   { 98   {
HITCBC 99   185216 if (!head_) 99   285019 if (!head_)
HITCBC 100   168226 return nullptr; 100   267453 return nullptr;
HITCBC 101   16990 T* w = head_; 101   17566 T* w = head_;
HITCBC 102   16990 head_ = static_cast<node*>(head_)->next_; 102   17566 head_ = static_cast<node*>(head_)->next_;
HITCBC 103   16990 if (head_) 103   17566 if (head_)
HITCBC 104   41 static_cast<node*>(head_)->prev_ = nullptr; 104   40 static_cast<node*>(head_)->prev_ = nullptr;
105   else 105   else
HITCBC 106   16949 tail_ = nullptr; 106   17526 tail_ = nullptr;
107   // Defensive: clear stale linkage so remove() on a 107   // Defensive: clear stale linkage so remove() on a
108   // popped node cannot corrupt the list. 108   // popped node cannot corrupt the list.
HITCBC 109   16990 auto* n = static_cast<node*>(w); 109   17566 auto* n = static_cast<node*>(w);
HITCBC 110   16990 n->next_ = nullptr; 110   17566 n->next_ = nullptr;
HITCBC 111   16990 n->prev_ = nullptr; 111   17566 n->prev_ = nullptr;
HITCBC 112   16990 return w; 112   17566 return w;
113   } 113   }
114   114  
HITCBC 115   24920 void remove(T* w) noexcept 115   26138 void remove(T* w) noexcept
116   { 116   {
HITCBC 117   24920 auto* n = static_cast<node*>(w); 117   26138 auto* n = static_cast<node*>(w);
118   // Already detached — nothing to do. 118   // Already detached — nothing to do.
HITCBC 119   24920 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w) 119   26138 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w)
MISUBC 120   ✗ return; 120   ✗ return;
HITCBC 121   24920 if (n->prev_) 121   26138 if (n->prev_)
HITCBC 122   8060 static_cast<node*>(n->prev_)->next_ = n->next_; 122   8353 static_cast<node*>(n->prev_)->next_ = n->next_;
123   else 123   else
HITCBC 124   16860 head_ = n->next_; 124   17785 head_ = n->next_;
HITCBC 125   24920 if (n->next_) 125   26138 if (n->next_)
HITCBC 126   16214 static_cast<node*>(n->next_)->prev_ = n->prev_; 126   16740 static_cast<node*>(n->next_)->prev_ = n->prev_;
127   else 127   else
HITCBC 128   8706 tail_ = n->prev_; 128   9398 tail_ = n->prev_;
HITCBC 129   24920 n->next_ = nullptr; 129   26138 n->next_ = nullptr;
HITCBC 130   24920 n->prev_ = nullptr; 130   26138 n->prev_ = nullptr;
131   } 131   }
132   132  
133   /// Invoke @p f for each element in the list. 133   /// Invoke @p f for each element in the list.
134   template<class F> 134   template<class F>
HITCBC 135   67 void for_each(F f) 135   122 void for_each(F f)
136   { 136   {
HITCBC 137   67 for (T* p = head_; p; p = static_cast<node*>(p)->next_) 137   122 for (T* p = head_; p; p = static_cast<node*>(p)->next_)
MISUBC 138   ✗ f(p); 138   ✗ f(p);
HITCBC 139   67 } 139   122 }
140   }; 140   };
141   141  
142   /** An intrusive singly linked FIFO queue. 142   /** An intrusive singly linked FIFO queue.
143   143  
144   This container provides O(1) push and pop operations for 144   This container provides O(1) push and pop operations for
145   elements that derive from @ref node. Elements are not 145   elements that derive from @ref node. Elements are not
146   copied or moved; they are linked directly into the queue. 146   copied or moved; they are linked directly into the queue.
147   147  
148   Unlike @ref intrusive_list, this uses only a single `next_` 148   Unlike @ref intrusive_list, this uses only a single `next_`
149   pointer per node, saving memory at the cost of not supporting 149   pointer per node, saving memory at the cost of not supporting
150   O(1) removal of arbitrary elements. 150   O(1) removal of arbitrary elements.
151   151  
152   @tparam T The element type. Must derive from `intrusive_queue<T>::node`. 152   @tparam T The element type. Must derive from `intrusive_queue<T>::node`.
153   */ 153   */
154   template<class T> 154   template<class T>
155   class intrusive_queue 155   class intrusive_queue
156   { 156   {
157   public: 157   public:
158   /** Base class for queue elements. 158   /** Base class for queue elements.
159   159  
160   Derive from this class to make a type usable with 160   Derive from this class to make a type usable with
161   @ref intrusive_queue. The `next_` pointer is private 161   @ref intrusive_queue. The `next_` pointer is private
162   and accessible only to the queue. 162   and accessible only to the queue.
163   */ 163   */
164   class node 164   class node
165   { 165   {
166   friend class intrusive_queue; 166   friend class intrusive_queue;
167   167  
168   private: 168   private:
169   T* next_; 169   T* next_;
170   }; 170   };
171   171  
172   private: 172   private:
173   T* head_ = nullptr; 173   T* head_ = nullptr;
174   T* tail_ = nullptr; 174   T* tail_ = nullptr;
175   175  
176   public: 176   public:
HITCBC 177   1715 intrusive_queue() = default; 177   2728 intrusive_queue() = default;
178   178  
179   intrusive_queue(intrusive_queue&& other) noexcept 179   intrusive_queue(intrusive_queue&& other) noexcept
180   : head_(other.head_) 180   : head_(other.head_)
181   , tail_(other.tail_) 181   , tail_(other.tail_)
182   { 182   {
183   other.head_ = nullptr; 183   other.head_ = nullptr;
184   other.tail_ = nullptr; 184   other.tail_ = nullptr;
185   } 185   }
186   186  
187   intrusive_queue(intrusive_queue const&) = delete; 187   intrusive_queue(intrusive_queue const&) = delete;
188   intrusive_queue& operator=(intrusive_queue const&) = delete; 188   intrusive_queue& operator=(intrusive_queue const&) = delete;
189   intrusive_queue& operator=(intrusive_queue&&) = delete; 189   intrusive_queue& operator=(intrusive_queue&&) = delete;
190   190  
HITCBC 191   1505211 bool empty() const noexcept 191   2206503 bool empty() const noexcept
192   { 192   {
HITCBC 193   1505211 return head_ == nullptr; 193   2206503 return head_ == nullptr;
194   } 194   }
195   195  
HITCBC 196   472544 void push(T* w) noexcept 196   676756 void push(T* w) noexcept
197   { 197   {
HITCBC 198   472544 w->next_ = nullptr; 198   676756 w->next_ = nullptr;
HITCBC 199   472544 if (tail_) 199   676756 if (tail_)
HITCBC 200   200041 tail_->next_ = w; 200   298404 tail_->next_ = w;
201   else 201   else
HITCBC 202   272503 head_ = w; 202   378352 head_ = w;
HITCBC 203   472544 tail_ = w; 203   676756 tail_ = w;
HITCBC 204   472544 } 204   676756 }
205   205  
HITCBC 206   248891 void splice(intrusive_queue& other) noexcept 206   353008 void splice(intrusive_queue& other) noexcept
207   { 207   {
HITCBC 208   248891 if (other.empty()) 208   353008 if (other.empty())
MISUBC 209   ✗ return; 209   ✗ return;
HITCBC 210   248891 if (tail_) 210   353008 if (tail_)
HITCBC 211   115682 tail_->next_ = other.head_; 211   126762 tail_->next_ = other.head_;
212   else 212   else
HITCBC 213   133209 head_ = other.head_; 213   226246 head_ = other.head_;
HITCBC 214   248891 tail_ = other.tail_; 214   353008 tail_ = other.tail_;
HITCBC 215   248891 other.head_ = nullptr; 215   353008 other.head_ = nullptr;
HITCBC 216   248891 other.tail_ = nullptr; 216   353008 other.tail_ = nullptr;
217   } 217   }
218   218  
HITCBC 219   628004 T* pop() noexcept 219   928451 T* pop() noexcept
220   { 220   {
HITCBC 221   628004 if (!head_) 221   928451 if (!head_)
HITCBC 222   155460 return nullptr; 222   251695 return nullptr;
HITCBC 223   472544 T* w = head_; 223   676756 T* w = head_;
HITCBC 224   472544 head_ = head_->next_; 224   676756 head_ = head_->next_;
HITCBC 225   472544 if (!head_) 225   676756 if (!head_)
HITCBC 226   156821 tail_ = nullptr; 226   251590 tail_ = nullptr;
227   // Defensive: clear stale linkage on popped node. 227   // Defensive: clear stale linkage on popped node.
HITCBC 228   472544 w->next_ = nullptr; 228   676756 w->next_ = nullptr;
HITCBC 229   472544 return w; 229   676756 return w;
230   } 230   }
231   }; 231   };
232   232  
233   } // namespace boost::corosio::detail 233   } // namespace boost::corosio::detail
234   234  
235   #endif 235   #endif