. /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   37481 void push_back(T* w) noexcept 66   24467 void push_back(T* w) noexcept
67   { 67   {
HITCBC 68   37481 auto* n = static_cast<node*>(w); 68   24467 auto* n = static_cast<node*>(w);
HITCBC 69   37481 n->next_ = nullptr; 69   24467 n->next_ = nullptr;
HITCBC 70   37481 n->prev_ = tail_; 70   24467 n->prev_ = tail_;
HITCBC 71   37481 if (tail_) 71   24467 if (tail_)
HITCBC 72   21362 static_cast<node*>(tail_)->next_ = w; 72   13550 static_cast<node*>(tail_)->next_ = w;
73   else 73   else
HITCBC 74   16119 head_ = w; 74   10917 head_ = w;
HITCBC 75   37481 tail_ = w; 75   24467 tail_ = w;
HITCBC 76   37481 } 76   24467 }
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   254466 T* pop_front() noexcept 97   268896 T* pop_front() noexcept
98   { 98   {
HITCBC 99   254466 if (!head_) 99   268896 if (!head_)
HITCBC 100   239398 return nullptr; 100   259030 return nullptr;
HITCBC 101   15068 T* w = head_; 101   9866 T* w = head_;
HITCBC 102   15068 head_ = static_cast<node*>(head_)->next_; 102   9866 head_ = static_cast<node*>(head_)->next_;
HITCBC 103   15068 if (head_) 103   9866 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   15027 tail_ = nullptr; 106   9825 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   15068 auto* n = static_cast<node*>(w); 109   9866 auto* n = static_cast<node*>(w);
HITCBC 110   15068 n->next_ = nullptr; 110   9866 n->next_ = nullptr;
HITCBC 111   15068 n->prev_ = nullptr; 111   9866 n->prev_ = nullptr;
HITCBC 112   15068 return w; 112   9866 return w;
113   } 113   }
114   114  
HITCBC 115   22413 void remove(T* w) noexcept 115   14601 void remove(T* w) noexcept
116   { 116   {
HITCBC 117   22413 auto* n = static_cast<node*>(w); 117   14601 auto* n = static_cast<node*>(w);
118   // Already detached — nothing to do. 118   // Already detached — nothing to do.
HITCBC 119   22413 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w) 119   14601 if (!n->next_ && !n->prev_ && head_ != w && tail_ != w)
MISUBC 120   ✗ return; 120   ✗ return;
HITCBC 121   22413 if (n->prev_) 121   14601 if (n->prev_)
HITCBC 122   7110 static_cast<node*>(n->prev_)->next_ = n->next_; 122   4506 static_cast<node*>(n->prev_)->next_ = n->next_;
123   else 123   else
HITCBC 124   15303 head_ = n->next_; 124   10095 head_ = n->next_;
HITCBC 125   22413 if (n->next_) 125   14601 if (n->next_)
HITCBC 126   14258 static_cast<node*>(n->next_)->prev_ = n->prev_; 126   9050 static_cast<node*>(n->next_)->prev_ = n->prev_;
127   else 127   else
HITCBC 128   8155 tail_ = n->prev_; 128   5551 tail_ = n->prev_;
HITCBC 129   22413 n->next_ = nullptr; 129   14601 n->next_ = nullptr;
HITCBC 130   22413 n->prev_ = nullptr; 130   14601 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   2725 intrusive_queue() = default; 177   2728 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   1993621 bool empty() const noexcept 191   2121225 bool empty() const noexcept
192   { 192   {
HITCBC 193   1993621 return head_ == nullptr; 193   2121225 return head_ == nullptr;
194   } 194   }
195   195  
HITCBC 196   612787 void push(T* w) noexcept 196   644615 void push(T* w) noexcept
197   { 197   {
HITCBC 198   612787 w->next_ = nullptr; 198   644615 w->next_ = nullptr;
HITCBC 199   612787 if (tail_) 199   644615 if (tail_)
HITCBC 200   268086 tail_->next_ = w; 200   286246 tail_->next_ = w;
201   else 201   else
HITCBC 202   344701 head_ = w; 202   358369 head_ = w;
HITCBC 203   612787 tail_ = w; 203   644615 tail_ = w;
HITCBC 204   612787 } 204   644615 }
205   205  
HITCBC 206   323225 void splice(intrusive_queue& other) noexcept 206   344385 void splice(intrusive_queue& other) noexcept
207   { 207   {
HITCBC 208   323225 if (other.empty()) 208   344385 if (other.empty())
MISUBC 209   ✗ return; 209   ✗ return;
HITCBC 210   323225 if (tail_) 210   344385 if (tail_)
HITCBC 211   123312 tail_->next_ = other.head_; 211   123138 tail_->next_ = other.head_;
212   else 212   else
HITCBC 213   199913 head_ = other.head_; 213   221247 head_ = other.head_;
HITCBC 214   323225 tail_ = other.tail_; 214   344385 tail_ = other.tail_;
HITCBC 215   323225 other.head_ = nullptr; 215   344385 other.head_ = nullptr;
HITCBC 216   323225 other.tail_ = nullptr; 216   344385 other.tail_ = nullptr;
217   } 217   }
218   218  
HITCBC 219   839547 T* pop() noexcept 219   899339 T* pop() noexcept
220   { 220   {
HITCBC 221   839547 if (!head_) 221   899339 if (!head_)
HITCBC 222   226760 return nullptr; 222   254724 return nullptr;
HITCBC 223   612787 T* w = head_; 223   644615 T* w = head_;
HITCBC 224   612787 head_ = head_->next_; 224   644615 head_ = head_->next_;
HITCBC 225   612787 if (!head_) 225   644615 if (!head_)
HITCBC 226   221389 tail_ = nullptr; 226   235231 tail_ = nullptr;
227   // Defensive: clear stale linkage on popped node. 227   // Defensive: clear stale linkage on popped node.
HITCBC 228   612787 w->next_ = nullptr; 228   644615 w->next_ = nullptr;
HITCBC 229   612787 return w; 229   644615 return w;
230   } 230   }
231   }; 231   };
232   232  
233   } // namespace boost::corosio::detail 233   } // namespace boost::corosio::detail
234   234  
235   #endif 235   #endif