. /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   10576 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   38 bool empty() const noexcept 61   38 bool empty() const noexcept
62   { 62   {
HITCBC 63   38 return head_ == nullptr; 63   38 return head_ == nullptr;
64   } 64   }
65   65  
HITCBC 66   41159 void push_back(T* w) noexcept 66   41762 void push_back(T* w) noexcept
67   { 67   {
HITCBC 68   41159 auto* n = static_cast<node*>(w); 68   41762 auto* n = static_cast<node*>(w);
HITCBC 69   41159 n->next_ = nullptr; 69   41762 n->next_ = nullptr;
HITCBC 70   41159 n->prev_ = tail_; 70   41762 n->prev_ = tail_;
HITCBC 71   41159 if (tail_) 71   41762 if (tail_)
HITCBC 72   23547 static_cast<node*>(tail_)->next_ = w; 72   23916 static_cast<node*>(tail_)->next_ = w;
73   else 73   else
HITCBC 74   17612 head_ = w; 74   17846 head_ = w;
HITCBC 75   41159 tail_ = w; 75   41762 tail_ = w;
HITCBC 76   41159 } 76   41762 }
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   314008 T* pop_front() noexcept 97   322974 T* pop_front() noexcept
98   { 98   {
HITCBC 99   314008 if (!head_) 99   322974 if (!head_)
HITCBC 100   297448 return nullptr; 100   306178 return nullptr;
HITCBC 101   16560 T* w = head_; 101   16796 T* w = head_;
HITCBC 102   16560 head_ = static_cast<node*>(head_)->next_; 102   16796 head_ = static_cast<node*>(head_)->next_;
HITCBC 103   16560 if (head_) 103   16796 if (head_)
HITCBC 104   40 static_cast<node*>(head_)->prev_ = nullptr; 104   42 static_cast<node*>(head_)->prev_ = nullptr;
105   else 105   else
HITCBC 106   16520 tail_ = nullptr; 106   16754 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   16560 auto* n = static_cast<node*>(w); 109   16796 auto* n = static_cast<node*>(w);
HITCBC 110   16560 n->next_ = nullptr; 110   16796 n->next_ = nullptr;
HITCBC 111   16560 n->prev_ = nullptr; 111   16796 n->prev_ = nullptr;
HITCBC 112   16560 return w; 112   16796 return w;
113   } 113   }
114   114  
HITCBC 115   24599 void remove(T* w) noexcept 115   24966 void remove(T* w) noexcept
116   { 116   {
HITCBC 117   24599 auto* n = static_cast<node*>(w); 117   24966 auto* n = static_cast<node*>(w);
118   // Already detached — nothing to do. 118   // Already detached — nothing to do.
HITCBC 119   24599 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w) 119   24966 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w)
MISUBC 120   ✗ return; 120   ✗ return;
HITCBC 121   24599 if (n->prev_) 121   24966 if (n->prev_)
HITCBC 122   7840 static_cast<node*>(n->prev_)->next_ = n->next_; 122   7960 static_cast<node*>(n->prev_)->next_ = n->next_;
123   else 123   else
HITCBC 124   16759 head_ = n->next_; 124   17006 head_ = n->next_;
HITCBC 125   24599 if (n->next_) 125   24966 if (n->next_)
HITCBC 126   15714 static_cast<node*>(n->next_)->prev_ = n->prev_; 126   15961 static_cast<node*>(n->next_)->prev_ = n->prev_;
127   else 127   else
HITCBC 128   8885 tail_ = n->prev_; 128   9005 tail_ = n->prev_;
HITCBC 129   24599 n->next_ = nullptr; 129   24966 n->next_ = nullptr;
HITCBC 130   24599 n->prev_ = nullptr; 130   24966 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   122 void for_each(F f) 135   122 void for_each(F f)
136   { 136   {
HITCBC 137   122 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   122 } 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   2724 intrusive_queue() = default; 177   2723 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   2497613 bool empty() const noexcept 191   2560309 bool empty() const noexcept
192   { 192   {
HITCBC 193   2497613 return head_ == nullptr; 193   2560309 return head_ == nullptr;
194   } 194   }
195   195  
HITCBC 196   765540 void push(T* w) noexcept 196   783904 void push(T* w) noexcept
197   { 197   {
HITCBC 198   765540 w->next_ = nullptr; 198   783904 w->next_ = nullptr;
HITCBC 199   765540 if (tail_) 199   783904 if (tail_)
HITCBC 200   335277 tail_->next_ = w; 200   344283 tail_->next_ = w;
201   else 201   else
HITCBC 202   430263 head_ = w; 202   439621 head_ = w;
HITCBC 203   765540 tail_ = w; 203   783904 tail_ = w;
HITCBC 204   765540 } 204   783904 }
205   205  
HITCBC 206   406536 void splice(intrusive_queue& other) noexcept 206   416299 void splice(intrusive_queue& other) noexcept
207   { 207   {
HITCBC 208   406536 if (other.empty()) 208   416299 if (other.empty())
MISUBC 209   ✗ return; 209   ✗ return;
HITCBC 210   406536 if (tail_) 210   416299 if (tail_)
HITCBC 211   155044 tail_->next_ = other.head_; 211   155859 tail_->next_ = other.head_;
212   else 212   else
HITCBC 213   251492 head_ = other.head_; 213   260440 head_ = other.head_;
HITCBC 214   406536 tail_ = other.tail_; 214   416299 tail_ = other.tail_;
HITCBC 215   406536 other.head_ = nullptr; 215   416299 other.head_ = nullptr;
HITCBC 216   406536 other.tail_ = nullptr; 216   416299 other.tail_ = nullptr;
217   } 217   }
218   218  
HITCBC 219   1053355 T* pop() noexcept 219   1080190 T* pop() noexcept
220   { 220   {
HITCBC 221   1053355 if (!head_) 221   1080190 if (!head_)
HITCBC 222   287815 return nullptr; 222   296286 return nullptr;
HITCBC 223   765540 T* w = head_; 223   783904 T* w = head_;
HITCBC 224   765540 head_ = head_->next_; 224   783904 head_ = head_->next_;
HITCBC 225   765540 if (!head_) 225   783904 if (!head_)
HITCBC 226   275219 tail_ = nullptr; 226   283762 tail_ = nullptr;
227   // Defensive: clear stale linkage on popped node. 227   // Defensive: clear stale linkage on popped node.
HITCBC 228   765540 w->next_ = nullptr; 228   783904 w->next_ = nullptr;
HITCBC 229   765540 return w; 229   783904 return w;
230   } 230   }
231   }; 231   };
232   232  
233   } // namespace boost::corosio::detail 233   } // namespace boost::corosio::detail
234   234  
235   #endif 235   #endif