. /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   42699 void push_back(T* w) noexcept 66   40990 void push_back(T* w) noexcept
67   { 67   {
HITCBC 68   42699 auto* n = static_cast<node*>(w); 68   40990 auto* n = static_cast<node*>(w);
HITCBC 69   42699 n->next_ = nullptr; 69   40990 n->next_ = nullptr;
HITCBC 70   42699 n->prev_ = tail_; 70   40990 n->prev_ = tail_;
HITCBC 71   42699 if (tail_) 71   40990 if (tail_)
HITCBC 72   24760 static_cast<node*>(tail_)->next_ = w; 72   23735 static_cast<node*>(tail_)->next_ = w;
73   else 73   else
HITCBC 74   17939 head_ = w; 74   17255 head_ = w;
HITCBC 75   42699 tail_ = w; 75   40990 tail_ = w;
HITCBC 76   42699 } 76   40990 }
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   189395 T* pop_front() noexcept 97   179600 T* pop_front() noexcept
98   { 98   {
HITCBC 99   189395 if (!head_) 99   179600 if (!head_)
HITCBC 100   172071 return nullptr; 100   162960 return nullptr;
HITCBC 101   17324 T* w = head_; 101   16640 T* w = head_;
HITCBC 102   17324 head_ = static_cast<node*>(head_)->next_; 102   16640 head_ = static_cast<node*>(head_)->next_;
HITCBC 103   17324 if (head_) 103   16640 if (head_)
HITCBC 104   41 static_cast<node*>(head_)->prev_ = nullptr; 104   41 static_cast<node*>(head_)->prev_ = nullptr;
105   else 105   else
HITCBC 106   17283 tail_ = nullptr; 106   16599 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   17324 auto* n = static_cast<node*>(w); 109   16640 auto* n = static_cast<node*>(w);
HITCBC 110   17324 n->next_ = nullptr; 110   16640 n->next_ = nullptr;
HITCBC 111   17324 n->prev_ = nullptr; 111   16640 n->prev_ = nullptr;
HITCBC 112   17324 return w; 112   16640 return w;
113   } 113   }
114   114  
HITCBC 115   25375 void remove(T* w) noexcept 115   24350 void remove(T* w) noexcept
116   { 116   {
HITCBC 117   25375 auto* n = static_cast<node*>(w); 117   24350 auto* n = static_cast<node*>(w);
118   // Already detached — nothing to do. 118   // Already detached — nothing to do.
HITCBC 119   25375 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w) 119   24350 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w)
MISUBC 120   ✗ return; 120   ✗ return;
HITCBC 121   25375 if (n->prev_) 121   24350 if (n->prev_)
HITCBC 122   8224 static_cast<node*>(n->prev_)->next_ = n->next_; 122   7882 static_cast<node*>(n->prev_)->next_ = n->next_;
123   else 123   else
HITCBC 124   17151 head_ = n->next_; 124   16468 head_ = n->next_;
HITCBC 125   25375 if (n->next_) 125   24350 if (n->next_)
HITCBC 126   16529 static_cast<node*>(n->next_)->prev_ = n->prev_; 126   15846 static_cast<node*>(n->next_)->prev_ = n->prev_;
127   else 127   else
HITCBC 128   8846 tail_ = n->prev_; 128   8504 tail_ = n->prev_;
HITCBC 129   25375 n->next_ = nullptr; 129   24350 n->next_ = nullptr;
HITCBC 130   25375 n->prev_ = nullptr; 130   24350 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   1712 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   1533124 bool empty() const noexcept 191   1493134 bool empty() const noexcept
192   { 192   {
HITCBC 193   1533124 return head_ == nullptr; 193   1493134 return head_ == nullptr;
194   } 194   }
195   195  
HITCBC 196   481388 void push(T* w) noexcept 196   471330 void push(T* w) noexcept
197   { 197   {
HITCBC 198   481388 w->next_ = nullptr; 198   471330 w->next_ = nullptr;
HITCBC 199   481388 if (tail_) 199   471330 if (tail_)
HITCBC 200   203079 tail_->next_ = w; 200   195370 tail_->next_ = w;
201   else 201   else
HITCBC 202   278309 head_ = w; 202   275960 head_ = w;
HITCBC 203   481388 tail_ = w; 203   471330 tail_ = w;
HITCBC 204   481388 } 204   471330 }
205   205  
HITCBC 206   253673 void splice(intrusive_queue& other) noexcept 206   252265 void splice(intrusive_queue& other) noexcept
207   { 207   {
HITCBC 208   253673 if (other.empty()) 208   252265 if (other.empty())
MISUBC 209   ✗ return; 209   ✗ return;
HITCBC 210   253673 if (tail_) 210   252265 if (tail_)
HITCBC 211   119075 tail_->next_ = other.head_; 211   127182 tail_->next_ = other.head_;
212   else 212   else
HITCBC 213   134598 head_ = other.head_; 213   125083 head_ = other.head_;
HITCBC 214   253673 tail_ = other.tail_; 214   252265 tail_ = other.tail_;
HITCBC 215   253673 other.head_ = nullptr; 215   252265 other.head_ = nullptr;
HITCBC 216   253673 other.tail_ = nullptr; 216   252265 other.tail_ = nullptr;
217   } 217   }
218   218  
HITCBC 219   637858 T* pop() noexcept 219   620503 T* pop() noexcept
220   { 220   {
HITCBC 221   637858 if (!head_) 221   620503 if (!head_)
HITCBC 222   156470 return nullptr; 222   149173 return nullptr;
HITCBC 223   481388 T* w = head_; 223   471330 T* w = head_;
HITCBC 224   481388 head_ = head_->next_; 224   471330 head_ = head_->next_;
HITCBC 225   481388 if (!head_) 225   471330 if (!head_)
HITCBC 226   159234 tail_ = nullptr; 226   148778 tail_ = nullptr;
227   // Defensive: clear stale linkage on popped node. 227   // Defensive: clear stale linkage on popped node.
HITCBC 228   481388 w->next_ = nullptr; 228   471330 w->next_ = nullptr;
HITCBC 229   481388 return w; 229   471330 return w;
230   } 230   }
231   }; 231   };
232   232  
233   } // namespace boost::corosio::detail 233   } // namespace boost::corosio::detail
234   234  
235   #endif 235   #endif