. /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   40081 void push_back(T* w) noexcept 66   39053 void push_back(T* w) noexcept
67   { 67   {
HITCBC 68   40081 auto* n = static_cast<node*>(w); 68   39053 auto* n = static_cast<node*>(w);
HITCBC 69   40081 n->next_ = nullptr; 69   39053 n->next_ = nullptr;
HITCBC 70   40081 n->prev_ = tail_; 70   39053 n->prev_ = tail_;
HITCBC 71   40081 if (tail_) 71   39053 if (tail_)
HITCBC 72   23173 static_cast<node*>(tail_)->next_ = w; 72   22580 static_cast<node*>(tail_)->next_ = w;
73   else 73   else
HITCBC 74   16908 head_ = w; 74   16473 head_ = w;
HITCBC 75   40081 tail_ = w; 75   39053 tail_ = w;
HITCBC 76   40081 } 76   39053 }
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   283616 T* pop_front() noexcept 97   173712 T* pop_front() noexcept
98   { 98   {
HITCBC 99   283616 if (!head_) 99   173712 if (!head_)
HITCBC 100   267322 return nullptr; 100   157854 return nullptr;
HITCBC 101   16294 T* w = head_; 101   15858 T* w = head_;
HITCBC 102   16294 head_ = static_cast<node*>(head_)->next_; 102   15858 head_ = static_cast<node*>(head_)->next_;
HITCBC 103   16294 if (head_) 103   15858 if (head_)
HITCBC 104   42 static_cast<node*>(head_)->prev_ = nullptr; 104   41 static_cast<node*>(head_)->prev_ = nullptr;
105   else 105   else
HITCBC 106   16252 tail_ = nullptr; 106   15817 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   16294 auto* n = static_cast<node*>(w); 109   15858 auto* n = static_cast<node*>(w);
HITCBC 110   16294 n->next_ = nullptr; 110   15858 n->next_ = nullptr;
HITCBC 111   16294 n->prev_ = nullptr; 111   15858 n->prev_ = nullptr;
HITCBC 112   16294 return w; 112   15858 return w;
113   } 113   }
114   114  
HITCBC 115   23787 void remove(T* w) noexcept 115   23195 void remove(T* w) noexcept
116   { 116   {
HITCBC 117   23787 auto* n = static_cast<node*>(w); 117   23195 auto* n = static_cast<node*>(w);
118   // Already detached — nothing to do. 118   // Already detached — nothing to do.
HITCBC 119   23787 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w) 119   23195 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w)
MISUBC 120   ✗ return; 120   ✗ return;
HITCBC 121   23787 if (n->prev_) 121   23195 if (n->prev_)
HITCBC 122   7693 static_cast<node*>(n->prev_)->next_ = n->next_; 122   7497 static_cast<node*>(n->prev_)->next_ = n->next_;
123   else 123   else
HITCBC 124   16094 head_ = n->next_; 124   15698 head_ = n->next_;
HITCBC 125   23787 if (n->next_) 125   23195 if (n->next_)
HITCBC 126   15472 static_cast<node*>(n->next_)->prev_ = n->prev_; 126   15076 static_cast<node*>(n->next_)->prev_ = n->prev_;
127   else 127   else
HITCBC 128   8315 tail_ = n->prev_; 128   8119 tail_ = n->prev_;
HITCBC 129   23787 n->next_ = nullptr; 129   23195 n->next_ = nullptr;
HITCBC 130   23787 n->prev_ = nullptr; 130   23195 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   1743 intrusive_queue() = default; 177   1716 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   2471320 bool empty() const noexcept 191   1457059 bool empty() const noexcept
192   { 192   {
HITCBC 193   2471320 return head_ == nullptr; 193   1457059 return head_ == nullptr;
194   } 194   }
195   195  
HITCBC 196   769188 void push(T* w) noexcept 196   459170 void push(T* w) noexcept
197   { 197   {
HITCBC 198   769188 w->next_ = nullptr; 198   459170 w->next_ = nullptr;
HITCBC 199   769188 if (tail_) 199   459170 if (tail_)
HITCBC 200   322179 tail_->next_ = w; 200   191105 tail_->next_ = w;
201   else 201   else
HITCBC 202   447009 head_ = w; 202   268065 head_ = w;
HITCBC 203   769188 tail_ = w; 203   459170 tail_ = w;
HITCBC 204   769188 } 204   459170 }
205   205  
HITCBC 206   423829 void splice(intrusive_queue& other) noexcept 206   245751 void splice(intrusive_queue& other) noexcept
207   { 207   {
HITCBC 208   423829 if (other.empty()) 208   245751 if (other.empty())
MISUBC 209   ✗ return; 209   ✗ return;
HITCBC 210   423829 if (tail_) 210   245751 if (tail_)
HITCBC 211   208219 tail_->next_ = other.head_; 211   121938 tail_->next_ = other.head_;
212   else 212   else
HITCBC 213   215610 head_ = other.head_; 213   123813 head_ = other.head_;
HITCBC 214   423829 tail_ = other.tail_; 214   245751 tail_ = other.tail_;
HITCBC 215   423829 other.head_ = nullptr; 215   245751 other.head_ = nullptr;
HITCBC 216   423829 other.tail_ = nullptr; 216   245751 other.tail_ = nullptr;
217   } 217   }
218   218  
HITCBC 219   1038480 T* pop() noexcept 219   608027 T* pop() noexcept
220   { 220   {
HITCBC 221   1038480 if (!head_) 221   608027 if (!head_)
HITCBC 222   269292 return nullptr; 222   148857 return nullptr;
HITCBC 223   769188 T* w = head_; 223   459170 T* w = head_;
HITCBC 224   769188 head_ = head_->next_; 224   459170 head_ = head_->next_;
HITCBC 225   769188 if (!head_) 225   459170 if (!head_)
HITCBC 226   238790 tail_ = nullptr; 226   146127 tail_ = nullptr;
227   // Defensive: clear stale linkage on popped node. 227   // Defensive: clear stale linkage on popped node.
HITCBC 228   769188 w->next_ = nullptr; 228   459170 w->next_ = nullptr;
HITCBC 229   769188 return w; 229   459170 return w;
230   } 230   }
231   }; 231   };
232   232  
233   } // namespace boost::corosio::detail 233   } // namespace boost::corosio::detail
234   234  
235   #endif 235   #endif