. /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   37727 void push_back(T* w) noexcept 66   31626 void push_back(T* w) noexcept
67   { 67   {
HITCBC 68   37727 auto* n = static_cast<node*>(w); 68   31626 auto* n = static_cast<node*>(w);
HITCBC 69   37727 n->next_ = nullptr; 69   31626 n->next_ = nullptr;
HITCBC 70   37727 n->prev_ = tail_; 70   31626 n->prev_ = tail_;
HITCBC 71   37727 if (tail_) 71   31626 if (tail_)
HITCBC 72   21764 static_cast<node*>(tail_)->next_ = w; 72   18132 static_cast<node*>(tail_)->next_ = w;
73   else 73   else
HITCBC 74   15963 head_ = w; 74   13494 head_ = w;
HITCBC 75   37727 tail_ = w; 75   31626 tail_ = w;
HITCBC 76   37727 } 76   31626 }
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   270283 T* pop_front() noexcept 97   153602 T* pop_front() noexcept
98   { 98   {
HITCBC 99   270283 if (!head_) 99   153602 if (!head_)
HITCBC 100   254935 return nullptr; 100   140722 return nullptr;
HITCBC 101   15348 T* w = head_; 101   12880 T* w = head_;
HITCBC 102   15348 head_ = static_cast<node*>(head_)->next_; 102   12880 head_ = static_cast<node*>(head_)->next_;
HITCBC 103   15348 if (head_) 103   12880 if (head_)
HITCBC 104   41 static_cast<node*>(head_)->prev_ = nullptr; 104   42 static_cast<node*>(head_)->prev_ = nullptr;
105   else 105   else
HITCBC 106   15307 tail_ = nullptr; 106   12838 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   15348 auto* n = static_cast<node*>(w); 109   12880 auto* n = static_cast<node*>(w);
HITCBC 110   15348 n->next_ = nullptr; 110   12880 n->next_ = nullptr;
HITCBC 111   15348 n->prev_ = nullptr; 111   12880 n->prev_ = nullptr;
HITCBC 112   15348 return w; 112   12880 return w;
113   } 113   }
114   114  
HITCBC 115   22379 void remove(T* w) noexcept 115   18746 void remove(T* w) noexcept
116   { 116   {
HITCBC 117   22379 auto* n = static_cast<node*>(w); 117   18746 auto* n = static_cast<node*>(w);
118   // Already detached — nothing to do. 118   // Already detached — nothing to do.
HITCBC 119   22379 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w) 119   18746 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w)
MISUBC 120   ✗ return; 120   ✗ return;
HITCBC 121   22379 if (n->prev_) 121   18746 if (n->prev_)
HITCBC 122   7225 static_cast<node*>(n->prev_)->next_ = n->next_; 122   6014 static_cast<node*>(n->prev_)->next_ = n->next_;
123   else 123   else
HITCBC 124   15154 head_ = n->next_; 124   12732 head_ = n->next_;
HITCBC 125   22379 if (n->next_) 125   18746 if (n->next_)
HITCBC 126   14532 static_cast<node*>(n->next_)->prev_ = n->prev_; 126   12110 static_cast<node*>(n->next_)->prev_ = n->prev_;
127   else 127   else
HITCBC 128   7847 tail_ = n->prev_; 128   6636 tail_ = n->prev_;
HITCBC 129   22379 n->next_ = nullptr; 129   18746 n->next_ = nullptr;
HITCBC 130   22379 n->prev_ = nullptr; 130   18746 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   1742 intrusive_queue() = default; 177   1714 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   2347951 bool empty() const noexcept 191   1263135 bool empty() const noexcept
192   { 192   {
HITCBC 193   2347951 return head_ == nullptr; 193   1263135 return head_ == nullptr;
194   } 194   }
195   195  
HITCBC 196   730294 void push(T* w) noexcept 196   399038 void push(T* w) noexcept
197   { 197   {
HITCBC 198   730294 w->next_ = nullptr; 198   399038 w->next_ = nullptr;
HITCBC 199   730294 if (tail_) 199   399038 if (tail_)
HITCBC 200   306354 tail_->next_ = w; 200   165788 tail_->next_ = w;
201   else 201   else
HITCBC 202   423940 head_ = w; 202   233250 head_ = w;
HITCBC 203   730294 tail_ = w; 203   399038 tail_ = w;
HITCBC 204   730294 } 204   399038 }
205   205  
HITCBC 206   402393 void splice(intrusive_queue& other) noexcept 206   215489 void splice(intrusive_queue& other) noexcept
207   { 207   {
HITCBC 208   402393 if (other.empty()) 208   215489 if (other.empty())
MISUBC 209   ✗ return; 209   ✗ return;
HITCBC 210   402393 if (tail_) 210   215489 if (tail_)
HITCBC 211   196196 tail_->next_ = other.head_; 211   111217 tail_->next_ = other.head_;
212   else 212   else
HITCBC 213   206197 head_ = other.head_; 213   104272 head_ = other.head_;
HITCBC 214   402393 tail_ = other.tail_; 214   215489 tail_ = other.tail_;
HITCBC 215   402393 other.head_ = nullptr; 215   215489 other.head_ = nullptr;
HITCBC 216   402393 other.tail_ = nullptr; 216   215489 other.tail_ = nullptr;
217   } 217   }
218   218  
HITCBC 219   986570 T* pop() noexcept 219   527295 T* pop() noexcept
220   { 220   {
HITCBC 221   986570 if (!head_) 221   527295 if (!head_)
HITCBC 222   256276 return nullptr; 222   128257 return nullptr;
HITCBC 223   730294 T* w = head_; 223   399038 T* w = head_;
HITCBC 224   730294 head_ = head_->next_; 224   399038 head_ = head_->next_;
HITCBC 225   730294 if (!head_) 225   399038 if (!head_)
HITCBC 226   227744 tail_ = nullptr; 226   122033 tail_ = nullptr;
227   // Defensive: clear stale linkage on popped node. 227   // Defensive: clear stale linkage on popped node.
HITCBC 228   730294 w->next_ = nullptr; 228   399038 w->next_ = nullptr;
HITCBC 229   730294 return w; 229   399038 return w;
230   } 230   }
231   }; 231   };
232   232  
233   } // namespace boost::corosio::detail 233   } // namespace boost::corosio::detail
234   234  
235   #endif 235   #endif