. /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   6471 intrusive_list() = default; 47   6471 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   32 bool empty() const noexcept
62   { 62   {
HITCBC 63   32 return head_ == nullptr; 63   32 return head_ == nullptr;
64   } 64   }
65   65  
HITCBC 66   45926 void push_back(T* w) noexcept 66   43793 void push_back(T* w) noexcept
67   { 67   {
HITCBC 68   45926 auto* n = static_cast<node*>(w); 68   43793 auto* n = static_cast<node*>(w);
HITCBC 69   45926 n->next_ = nullptr; 69   43793 n->next_ = nullptr;
HITCBC 70   45926 n->prev_ = tail_; 70   43793 n->prev_ = tail_;
HITCBC 71   45926 if (tail_) 71   43793 if (tail_)
HITCBC 72   26686 static_cast<node*>(tail_)->next_ = w; 72   25405 static_cast<node*>(tail_)->next_ = w;
73   else 73   else
HITCBC 74   19240 head_ = w; 74   18388 head_ = w;
HITCBC 75   45926 tail_ = w; 75   43793 tail_ = w;
HITCBC 76   45926 } 76   43793 }
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   180128 T* pop_front() noexcept 97   192259 T* pop_front() noexcept
98   { 98   {
HITCBC 99   180128 if (!head_) 99   192259 if (!head_)
HITCBC 100   161528 return nullptr; 100   174511 return nullptr;
HITCBC 101   18600 T* w = head_; 101   17748 T* w = head_;
HITCBC 102   18600 head_ = static_cast<node*>(head_)->next_; 102   17748 head_ = static_cast<node*>(head_)->next_;
HITCBC 103   18600 if (head_) 103   17748 if (head_)
HITCBC 104   40 static_cast<node*>(head_)->prev_ = nullptr; 104   40 static_cast<node*>(head_)->prev_ = nullptr;
105   else 105   else
HITCBC 106   18560 tail_ = nullptr; 106   17708 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   18600 auto* n = static_cast<node*>(w); 109   17748 auto* n = static_cast<node*>(w);
HITCBC 110   18600 n->next_ = nullptr; 110   17748 n->next_ = nullptr;
HITCBC 111   18600 n->prev_ = nullptr; 111   17748 n->prev_ = nullptr;
HITCBC 112   18600 return w; 112   17748 return w;
113   } 113   }
114   114  
HITCBC 115   27326 void remove(T* w) noexcept 115   26045 void remove(T* w) noexcept
116   { 116   {
HITCBC 117   27326 auto* n = static_cast<node*>(w); 117   26045 auto* n = static_cast<node*>(w);
118   // Already detached — nothing to do. 118   // Already detached — nothing to do.
HITCBC 119   27326 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w) 119   26045 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w)
MISUBC 120   ✗ return; 120   ✗ return;
HITCBC 121   27326 if (n->prev_) 121   26045 if (n->prev_)
HITCBC 122   8862 static_cast<node*>(n->prev_)->next_ = n->next_; 122   8435 static_cast<node*>(n->prev_)->next_ = n->next_;
123   else 123   else
HITCBC 124   18464 head_ = n->next_; 124   17610 head_ = n->next_;
HITCBC 125   27326 if (n->next_) 125   26045 if (n->next_)
HITCBC 126   17818 static_cast<node*>(n->next_)->prev_ = n->prev_; 126   16964 static_cast<node*>(n->next_)->prev_ = n->prev_;
127   else 127   else
HITCBC 128   9508 tail_ = n->prev_; 128   9081 tail_ = n->prev_;
HITCBC 129   27326 n->next_ = nullptr; 129   26045 n->next_ = nullptr;
HITCBC 130   27326 n->prev_ = nullptr; 130   26045 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   67 void for_each(F f)
136   { 136   {
HITCBC 137   67 for (T* p = head_; p; p = static_cast<node*>(p)->next_) 137   67 for (T* p = head_; p; p = static_cast<node*>(p)->next_)
MISUBC 138   ✗ f(p); 138   ✗ f(p);
HITCBC 139   67 } 139   67 }
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   1763 intrusive_queue() = default; 177   1768 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   1487994 bool empty() const noexcept 191   1593378 bool empty() const noexcept
192   { 192   {
HITCBC 193   1487994 return head_ == nullptr; 193   1593378 return head_ == nullptr;
194   } 194   }
195   195  
HITCBC 196   471690 void push(T* w) noexcept 196   502665 void push(T* w) noexcept
197   { 197   {
HITCBC 198   471690 w->next_ = nullptr; 198   502665 w->next_ = nullptr;
HITCBC 199   471690 if (tail_) 199   502665 if (tail_)
HITCBC 200   196526 tail_->next_ = w; 200   209125 tail_->next_ = w;
201   else 201   else
HITCBC 202   275164 head_ = w; 202   293540 head_ = w;
HITCBC 203   471690 tail_ = w; 203   502665 tail_ = w;
HITCBC 204   471690 } 204   502665 }
205   205  
HITCBC 206   250213 void splice(intrusive_queue& other) noexcept 206   268566 void splice(intrusive_queue& other) noexcept
207   { 207   {
HITCBC 208   250213 if (other.empty()) 208   268566 if (other.empty())
MISUBC 209   ✗ return; 209   ✗ return;
HITCBC 210   250213 if (tail_) 210   268566 if (tail_)
HITCBC 211   125319 tail_->next_ = other.head_; 211   134541 tail_->next_ = other.head_;
212   else 212   else
HITCBC 213   124894 head_ = other.head_; 213   134025 head_ = other.head_;
HITCBC 214   250213 tail_ = other.tail_; 214   268566 tail_ = other.tail_;
HITCBC 215   250213 other.head_ = nullptr; 215   268566 other.head_ = nullptr;
HITCBC 216   250213 other.tail_ = nullptr; 216   268566 other.tail_ = nullptr;
217   } 217   }
218   218  
HITCBC 219   619978 T* pop() noexcept 219   662636 T* pop() noexcept
220   { 220   {
HITCBC 221   619978 if (!head_) 221   662636 if (!head_)
HITCBC 222   148288 return nullptr; 222   159971 return nullptr;
HITCBC 223   471690 T* w = head_; 223   502665 T* w = head_;
HITCBC 224   471690 head_ = head_->next_; 224   502665 head_ = head_->next_;
HITCBC 225   471690 if (!head_) 225   502665 if (!head_)
HITCBC 226   149845 tail_ = nullptr; 226   158999 tail_ = nullptr;
227   // Defensive: clear stale linkage on popped node. 227   // Defensive: clear stale linkage on popped node.
HITCBC 228   471690 w->next_ = nullptr; 228   502665 w->next_ = nullptr;
HITCBC 229   471690 return w; 229   502665 return w;
230   } 230   }
231   }; 231   };
232   232  
233   } // namespace boost::corosio::detail 233   } // namespace boost::corosio::detail
234   234  
235   #endif 235   #endif