boost/intrusive/circular_slist_algorithms.hpp
///////////////////////////////////////////////////////////////////////////// // // (C) Copyright Olaf Krzikalla 2004-2006. // (C) Copyright Ion Gaztanaga 2006-2008 // // Distributed under the Boost Software License, Version 1.0. // (See accompanying file LICENSE_1_0.txt or copy at // http://www.boost.org/LICENSE_1_0.txt) // // See http://www.boost.org/libs/intrusive for documentation. // ///////////////////////////////////////////////////////////////////////////// #ifndef BOOST_INTRUSIVE_CIRCULAR_SLIST_ALGORITHMS_HPP #define BOOST_INTRUSIVE_CIRCULAR_SLIST_ALGORITHMS_HPP #include <boost/intrusive/detail/config_begin.hpp> #include <boost/intrusive/intrusive_fwd.hpp> #include <boost/intrusive/detail/common_slist_algorithms.hpp> #include <boost/intrusive/detail/assert.hpp> #include <cstddef> namespace boost { namespace intrusive { //! circular_slist_algorithms provides basic algorithms to manipulate nodes //! forming a circular singly linked list. An empty circular list is formed by a node //! whose pointer to the next node points to itself. //! //! circular_slist_algorithms is configured with a NodeTraits class, which encapsulates the //! information about the node to be manipulated. NodeTraits must support the //! following interface: //! //! <b>Typedefs</b>: //! //! <tt>node</tt>: The type of the node that forms the circular list //! //! <tt>node_ptr</tt>: A pointer to a node //! //! <tt>const_node_ptr</tt>: A pointer to a const node //! //! <b>Static functions</b>: //! //! <tt>static node_ptr get_next(const_node_ptr n);</tt> //! //! <tt>static void set_next(node_ptr n, node_ptr next);</tt> template<class NodeTraits> class circular_slist_algorithms /// @cond : public detail::common_slist_algorithms<NodeTraits> /// @endcond { /// @cond typedef detail::common_slist_algorithms<NodeTraits> base_t; /// @endcond public: typedef typename NodeTraits::node node; typedef typename NodeTraits::node_ptr node_ptr; typedef typename NodeTraits::const_node_ptr const_node_ptr; typedef NodeTraits node_traits; #if defined(BOOST_INTRUSIVE_DOXYGEN_INVOKED) //! <b>Effects</b>: Constructs an non-used list element, putting the next //! pointer to null: //! <tt>NodeTraits::get_next(this_node) == 0 //! //! <b>Complexity</b>: Constant //! //! <b>Throws</b>: Nothing. static void init(node_ptr this_node); //! <b>Requires</b>: this_node must be in a circular list or be an empty circular list. //! //! <b>Effects</b>: Returns true is "this_node" is the only node of a circular list: //! or it's a not inserted node: //! <tt>return !NodeTraits::get_next(this_node) || NodeTraits::get_next(this_node) == this_node</tt> //! //! <b>Complexity</b>: Constant //! //! <b>Throws</b>: Nothing. static bool unique(const_node_ptr this_node); //! <b>Effects</b>: Returns true is "this_node" has the same state as //! if it was inited using "init(node_ptr)" //! //! <b>Complexity</b>: Constant //! //! <b>Throws</b>: Nothing. static bool inited(const_node_ptr this_node); //! <b>Requires</b>: prev_node must be in a circular list or be an empty circular list. //! //! <b>Effects</b>: Unlinks the next node of prev_node from the circular list. //! //! <b>Complexity</b>: Constant //! //! <b>Throws</b>: Nothing. static void unlink_after(node_ptr prev_node); //! <b>Requires</b>: prev_node and last_node must be in a circular list //! or be an empty circular list. //! //! <b>Effects</b>: Unlinks the range (prev_node, last_node) from the circular list. //! //! <b>Complexity</b>: Constant //! //! <b>Throws</b>: Nothing. static void unlink_after(node_ptr prev_node, node_ptr last_node); //! <b>Requires</b>: prev_node must be a node of a circular list. //! //! <b>Effects</b>: Links this_node after prev_node in the circular list. //! //! <b>Complexity</b>: Constant //! //! <b>Throws</b>: Nothing. static void link_after(node_ptr prev_node, node_ptr this_node); //! <b>Requires</b>: b and e must be nodes of the same circular list or an empty range. //! and p must be a node of a different circular list. //! //! <b>Effects</b>: Removes the nodes from (b, e] range from their circular list and inserts //! them after p in p's circular list. //! //! <b>Complexity</b>: Constant //! //! <b>Throws</b>: Nothing. static void transfer_after(node_ptr p, node_ptr b, node_ptr e); #endif //#if defined(BOOST_INTRUSIVE_DOXYGEN_INVOKED) //! <b>Effects</b>: Constructs an empty list, making this_node the only //! node of the circular list: //! <tt>NodeTraits::get_next(this_node) == this_node</tt>. //! //! <b>Complexity</b>: Constant //! //! <b>Throws</b>: Nothing. static void init_header(node_ptr this_node) { NodeTraits::set_next(this_node, this_node); } //! <b>Requires</b>: this_node and prev_init_node must be in the same circular list. //! //! <b>Effects</b>: Returns the previous node of this_node in the circular list starting. //! the search from prev_init_node. The first node checked for equality //! is NodeTraits::get_next(prev_init_node). //! //! <b>Complexity</b>: Linear to the number of elements between prev_init_node and this_node. //! //! <b>Throws</b>: Nothing. static node_ptr get_previous_node(node_ptr prev_init_node, node_ptr this_node) { return base_t::get_previous_node(prev_init_node, this_node); } //! <b>Requires</b>: this_node must be in a circular list or be an empty circular list. //! //! <b>Effects</b>: Returns the previous node of this_node in the circular list. //! //! <b>Complexity</b>: Linear to the number of elements in the circular list. //! //! <b>Throws</b>: Nothing. static node_ptr get_previous_node(node_ptr this_node) { return base_t::get_previous_node(this_node, this_node); } //! <b>Requires</b>: this_node must be in a circular list or be an empty circular list. //! //! <b>Effects</b>: Returns the previous node of the previous node of this_node in the circular list. //! //! <b>Complexity</b>: Linear to the number of elements in the circular list. //! //! <b>Throws</b>: Nothing. static node_ptr get_previous_previous_node(node_ptr this_node) { return get_previous_previous_node(this_node, this_node); } //! <b>Requires</b>: this_node and prev_prev_init_node must be in the same circular list. //! //! <b>Effects</b>: Returns the previous node of the previous node of this_node in the //! circular list starting. the search from prev_init_node. The first node checked //! for equality is NodeTraits::get_next((NodeTraits::get_next(prev_prev_init_node)). //! //! <b>Complexity</b>: Linear to the number of elements in the circular list. //! //! <b>Throws</b>: Nothing. static node_ptr get_previous_previous_node(node_ptr prev_prev_init_node, node_ptr this_node) { node_ptr p = prev_prev_init_node; node_ptr p_next = NodeTraits::get_next(p); node_ptr p_next_next = NodeTraits::get_next(p_next); while (this_node != p_next_next){ p = p_next; p_next = p_next_next; p_next_next = NodeTraits::get_next(p_next); } return p; } //! <b>Requires</b>: this_node must be in a circular list or be an empty circular list. //! //! <b>Effects</b>: Returns the number of nodes in a circular list. If the circular list //! is empty, returns 1. //! //! <b>Complexity</b>: Constant //! //! <b>Throws</b>: Nothing. static std::size_t count(const_node_ptr this_node) { std::size_t result = 0; const_node_ptr p = this_node; do{ p = NodeTraits::get_next(p); ++result; } while (p != this_node); return result; } //! <b>Requires</b>: this_node must be in a circular list, be an empty circular list or be inited. //! //! <b>Effects</b>: Unlinks the node from the circular list. //! //! <b>Complexity</b>: Linear to the number of elements in the circular list //! //! <b>Throws</b>: Nothing. static void unlink(node_ptr this_node) { if(NodeTraits::get_next(this_node)) base_t::unlink_after(get_previous_node(this_node)); } //! <b>Requires</b>: nxt_node must be a node of a circular list. //! //! <b>Effects</b>: Links this_node before nxt_node in the circular list. //! //! <b>Complexity</b>: Linear to the number of elements in the circular list. //! //! <b>Throws</b>: Nothing. static void link_before (node_ptr nxt_node, node_ptr this_node) { base_t::link_after(get_previous_node(nxt_node), this_node); } //! <b>Requires</b>: this_node and other_node must be nodes inserted //! in circular lists or be empty circular lists. //! //! <b>Effects</b>: Swaps the position of the nodes: this_node is inserted in //! other_nodes position in the second circular list and the other_node is inserted //! in this_node's position in the first circular list. //! //! <b>Complexity</b>: Linear to number of elements of both lists //! //! <b>Throws</b>: Nothing. static void swap_nodes(node_ptr this_node, node_ptr other_node) { if (other_node == this_node) return; bool this_inited = base_t::inited(this_node); bool other_inited = base_t::inited(other_node); if(this_inited){ base_t::init_header(this_node); } if(other_inited){ base_t::init_header(other_node); } bool empty1 = base_t::unique(this_node); bool empty2 = base_t::unique(other_node); node_ptr prev_this (get_previous_node(this_node)); node_ptr prev_other(get_previous_node(other_node)); node_ptr this_next (NodeTraits::get_next(this_node)); node_ptr other_next(NodeTraits::get_next(other_node)); NodeTraits::set_next(this_node, other_next); NodeTraits::set_next(other_node, this_next); NodeTraits::set_next(empty1 ? other_node : prev_this, other_node); NodeTraits::set_next(empty2 ? this_node : prev_other, this_node); if(this_inited){ base_t::init(other_node); } if(other_inited){ base_t::init(this_node); } } //! <b>Effects</b>: Reverses the order of elements in the list. //! //! <b>Throws</b>: Nothing. //! //! <b>Complexity</b>: This function is linear to the contained elements. static void reverse(node_ptr p) { node_ptr i = NodeTraits::get_next(p), e(p); for (;;) { node_ptr nxt(NodeTraits::get_next(i)); if (nxt == e) break; base_t::transfer_after(e, i, nxt); } } //! <b>Effects</b>: Moves the node p n positions towards the end of the list. //! //! <b>Returns</b>: The previous node of p after the function if there has been any movement, //! Null if n leads to no movement. //! //! <b>Throws</b>: Nothing. //! //! <b>Complexity</b>: Linear to the number of elements plus the number moved positions. static node_ptr move_backwards(node_ptr p, std::size_t n) { //Null shift, nothing to do if(!n) return node_ptr(0); node_ptr first = NodeTraits::get_next(p); //count() == 1 or 2, nothing to do if(NodeTraits::get_next(first) == p) return node_ptr(0); bool end_found = false; node_ptr new_last(0); //Now find the new last node according to the shift count. //If we find p before finding the new last node //unlink p, shortcut the search now that we know the size of the list //and continue. for(std::size_t i = 1; i <= n; ++i){ new_last = first; first = NodeTraits::get_next(first); if(first == p){ //Shortcut the shift with the modulo of the size of the list n %= i; if(!n) return node_ptr(0); i = 0; //Unlink p and continue the new first node search first = NodeTraits::get_next(p); base_t::unlink_after(new_last); end_found = true; } } //If the p has not been found in the previous loop, find it //starting in the new first node and unlink it if(!end_found){ base_t::unlink_after(base_t::get_previous_node(first, p)); } //Now link p after the new last node base_t::link_after(new_last, p); return new_last; } //! <b>Effects</b>: Moves the node p n positions towards the beginning of the list. //! //! <b>Returns</b>: The previous node of p after the function if there has been any movement, //! Null if n leads equals to no movement. //! //! <b>Throws</b>: Nothing. //! //! <b>Complexity</b>: Linear to the number of elements plus the number moved positions. static node_ptr move_forward(node_ptr p, std::size_t n) { //Null shift, nothing to do if(!n) return node_ptr(0); node_ptr first = node_traits::get_next(p); //count() == 1 or 2, nothing to do if(node_traits::get_next(first) == p) return node_ptr(0); //Iterate until p is found to know where the current last node is. //If the shift count is less than the size of the list, we can also obtain //the position of the new last node after the shift. node_ptr old_last(first), next_to_it, new_last(p); std::size_t distance = 1; while(p != (next_to_it = node_traits::get_next(old_last))){ if(++distance > n) new_last = node_traits::get_next(new_last); old_last = next_to_it; } //If the shift was bigger or equal than the size, obtain the equivalent //forward shifts and find the new last node. if(distance <= n){ //Now find the equivalent forward shifts. //Shortcut the shift with the modulo of the size of the list std::size_t new_before_last_pos = (distance - (n % distance))% distance; //If the shift is a multiple of the size there is nothing to do if(!new_before_last_pos) return node_ptr(0); for( new_last = p ; new_before_last_pos-- ; new_last = node_traits::get_next(new_last)){ //empty } } //Now unlink p and link it after the new last node base_t::unlink_after(old_last); base_t::link_after(new_last, p); return new_last; } }; } //namespace intrusive } //namespace boost #include <boost/intrusive/detail/config_end.hpp> #endif //BOOST_INTRUSIVE_CIRCULAR_SLIST_ALGORITHMS_HPP