. /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   6327 intrusive_list() = default; 47   6327 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   40794 void push_back(T* w) noexcept 66   38180 void push_back(T* w) noexcept
67   { 67   {
HITCBC 68   40794 auto* n = static_cast<node*>(w); 68   38180 auto* n = static_cast<node*>(w);
HITCBC 69   40794 n->next_ = nullptr; 69   38180 n->next_ = nullptr;
HITCBC 70   40794 n->prev_ = tail_; 70   38180 n->prev_ = tail_;
HITCBC 71   40794 if (tail_) 71   38180 if (tail_)
HITCBC 72   23616 static_cast<node*>(tail_)->next_ = w; 72   22037 static_cast<node*>(tail_)->next_ = w;
73   else 73   else
HITCBC 74   17178 head_ = w; 74   16143 head_ = w;
HITCBC 75   40794 tail_ = w; 75   38180 tail_ = w;
HITCBC 76   40794 } 76   38180 }
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   181041 T* pop_front() noexcept 97   267702 T* pop_front() noexcept
98   { 98   {
HITCBC 99   181041 if (!head_) 99   267702 if (!head_)
HITCBC 100   164479 return nullptr; 100   252174 return nullptr;
HITCBC 101   16562 T* w = head_; 101   15528 T* w = head_;
HITCBC 102   16562 head_ = static_cast<node*>(head_)->next_; 102   15528 head_ = static_cast<node*>(head_)->next_;
HITCBC 103   16562 if (head_) 103   15528 if (head_)
HITCBC 104   40 static_cast<node*>(head_)->prev_ = nullptr; 104   41 static_cast<node*>(head_)->prev_ = nullptr;
105   else 105   else
HITCBC 106   16522 tail_ = nullptr; 106   15487 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   16562 auto* n = static_cast<node*>(w); 109   15528 auto* n = static_cast<node*>(w);
HITCBC 110   16562 n->next_ = nullptr; 110   15528 n->next_ = nullptr;
HITCBC 111   16562 n->prev_ = nullptr; 111   15528 n->prev_ = nullptr;
HITCBC 112   16562 return w; 112   15528 return w;
113   } 113   }
114   114  
HITCBC 115   24232 void remove(T* w) noexcept 115   22652 void remove(T* w) noexcept
116   { 116   {
HITCBC 117   24232 auto* n = static_cast<node*>(w); 117   22652 auto* n = static_cast<node*>(w);
118   // Already detached — nothing to do. 118   // Already detached — nothing to do.
HITCBC 119   24232 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w) 119   22652 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w)
MISUBC 120   ✗ return; 120   ✗ return;
HITCBC 121   24232 if (n->prev_) 121   22652 if (n->prev_)
HITCBC 122   7844 static_cast<node*>(n->prev_)->next_ = n->next_; 122   7316 static_cast<node*>(n->prev_)->next_ = n->next_;
123   else 123   else
HITCBC 124   16388 head_ = n->next_; 124   15336 head_ = n->next_;
HITCBC 125   24232 if (n->next_) 125   22652 if (n->next_)
HITCBC 126   15766 static_cast<node*>(n->next_)->prev_ = n->prev_; 126   14714 static_cast<node*>(n->next_)->prev_ = n->prev_;
127   else 127   else
HITCBC 128   8466 tail_ = n->prev_; 128   7938 tail_ = n->prev_;
HITCBC 129   24232 n->next_ = nullptr; 129   22652 n->next_ = nullptr;
HITCBC 130   24232 n->prev_ = nullptr; 130   22652 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   1714 intrusive_queue() = default; 177   1741 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   1508749 bool empty() const noexcept 191   2345366 bool empty() const noexcept
192   { 192   {
HITCBC 193   1508749 return head_ == nullptr; 193   2345366 return head_ == nullptr;
194   } 194   }
195   195  
HITCBC 196   475948 void push(T* w) noexcept 196   730259 void push(T* w) noexcept
197   { 197   {
HITCBC 198   475948 w->next_ = nullptr; 198   730259 w->next_ = nullptr;
HITCBC 199   475948 if (tail_) 199   730259 if (tail_)
HITCBC 200   198752 tail_->next_ = w; 200   305525 tail_->next_ = w;
201   else 201   else
HITCBC 202   277196 head_ = w; 202   424734 head_ = w;
HITCBC 203   475948 tail_ = w; 203   730259 tail_ = w;
HITCBC 204   475948 } 204   730259 }
205   205  
HITCBC 206   253751 void splice(intrusive_queue& other) noexcept 206   402731 void splice(intrusive_queue& other) noexcept
207   { 207   {
HITCBC 208   253751 if (other.empty()) 208   402731 if (other.empty())
MISUBC 209   ✗ return; 209   ✗ return;
HITCBC 210   253751 if (tail_) 210   402731 if (tail_)
HITCBC 211   125575 tail_->next_ = other.head_; 211   198434 tail_->next_ = other.head_;
212   else 212   else
HITCBC 213   128176 head_ = other.head_; 213   204297 head_ = other.head_;
HITCBC 214   253751 tail_ = other.tail_; 214   402731 tail_ = other.tail_;
HITCBC 215   253751 other.head_ = nullptr; 215   402731 other.head_ = nullptr;
HITCBC 216   253751 other.tail_ = nullptr; 216   402731 other.tail_ = nullptr;
217   } 217   }
218   218  
HITCBC 219   630100 T* pop() noexcept 219   985248 T* pop() noexcept
220   { 220   {
HITCBC 221   630100 if (!head_) 221   985248 if (!head_)
HITCBC 222   154152 return nullptr; 222   254989 return nullptr;
HITCBC 223   475948 T* w = head_; 223   730259 T* w = head_;
HITCBC 224   475948 head_ = head_->next_; 224   730259 head_ = head_->next_;
HITCBC 225   475948 if (!head_) 225   730259 if (!head_)
HITCBC 226   151621 tail_ = nullptr; 226   226300 tail_ = nullptr;
227   // Defensive: clear stale linkage on popped node. 227   // Defensive: clear stale linkage on popped node.
HITCBC 228   475948 w->next_ = nullptr; 228   730259 w->next_ = nullptr;
HITCBC 229   475948 return w; 229   730259 return w;
230   } 230   }
231   }; 231   };
232   232  
233   } // namespace boost::corosio::detail 233   } // namespace boost::corosio::detail
234   234  
235   #endif 235   #endif