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 /////////////////////////////////////////////////////////////////////////////
 //
 // (C) Copyright Olaf Krzikalla 2004-2006.
 // (C) Copyright Ion Gaztanaga  2006-2014
 //
 // 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 <cstddef>
 #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/uncast.hpp>
 #include <boost/intrusive/detail/algo_type.hpp>
 
 #if defined(BOOST_HAS_PRAGMA_ONCE)
 #  pragma once
 #endif
 
 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) == node_ptr()</tt>
    //!
    //! <b>Complexity</b>: Constant
    //!
    //! <b>Throws</b>: Nothing.
    static void init(node_ptr this_node) BOOST_NOEXCEPT;
 
    //! <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 node_ptr() == 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) BOOST_NOEXCEPT;
 
    //! <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) BOOST_NOEXCEPT;
 
    //! <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) BOOST_NOEXCEPT;
 
    //! <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) BOOST_NOEXCEPT;
 
    //! <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) BOOST_NOEXCEPT;
 
    //! <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) BOOST_NOEXCEPT;
    
    #else
 
    using base_t::transfer_after;
 
    #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.
    BOOST_INTRUSIVE_FORCEINLINE static void init_header(node_ptr this_node) BOOST_NOEXCEPT
    {  NodeTraits::set_next(this_node, this_node);  }
 
    //! <b>Requires</b>: 'p' is the first node of a list.
    //!
    //! <b>Effects</b>: Returns a pointer to a node that represents the "end" (one past end) node
    //!
    //! <b>Complexity</b>: Constant time.
    //!
    //! <b>Throws</b>: Nothing.
    BOOST_INTRUSIVE_FORCEINLINE static node_ptr end_node(const_node_ptr p) BOOST_NOEXCEPT
    {  return detail::uncast(p);   }
 
    //! <b>Effects</b>: Returns true if this_node_points to an empty list.
    //! 
    //! <b>Complexity</b>: Constant
    //!
    //! <b>Throws</b>: Nothing.
    BOOST_INTRUSIVE_FORCEINLINE static bool is_empty(const_node_ptr this_node) BOOST_NOEXCEPT
    {  return NodeTraits::get_next(this_node) == this_node;  }
 
    //! <b>Effects</b>: Returns true if this_node points to a sentinel node.
    //! 
    //! <b>Complexity</b>: Constant
    //!
    //! <b>Throws</b>: Nothing.
    BOOST_INTRUSIVE_FORCEINLINE static bool is_sentinel(const_node_ptr this_node) BOOST_NOEXCEPT
    {  return NodeTraits::get_next(this_node) == node_ptr();  }
 
    //! <b>Effects</b>: Marks this node as a "sentinel" node, a special state that is different from "empty",
    //!                 that can be used to mark a special state of the list
    //!
    //! <b>Complexity</b>: Constant
    //!
    //! <b>Throws</b>: Nothing.
    BOOST_INTRUSIVE_FORCEINLINE static void set_sentinel(node_ptr this_node) BOOST_NOEXCEPT
    {  NodeTraits::set_next(this_node, node_ptr());   }
 
    //! <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.
    BOOST_INTRUSIVE_FORCEINLINE static node_ptr get_previous_node(node_ptr prev_init_node, node_ptr this_node) BOOST_NOEXCEPT
    {  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.
    BOOST_INTRUSIVE_FORCEINLINE static node_ptr get_previous_node(node_ptr this_node) BOOST_NOEXCEPT
    {  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.
    BOOST_INTRUSIVE_FORCEINLINE static node_ptr get_previous_previous_node(node_ptr this_node) BOOST_NOEXCEPT
    {  return get_previous_previous_node(this_node, this_node); }
 
    //! <b>Requires</b>: this_node and p 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 p. The first node checked
    //!   for equality is NodeTraits::get_next((NodeTraits::get_next(p)).
    //!
    //! <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 p, node_ptr this_node) BOOST_NOEXCEPT
    {
       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>: Linear
    //!
    //! <b>Throws</b>: Nothing.
    static std::size_t count(const_node_ptr this_node) BOOST_NOEXCEPT
    {
       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) BOOST_NOEXCEPT
    {
       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.
    BOOST_INTRUSIVE_FORCEINLINE static void link_before (node_ptr nxt_node, node_ptr this_node) BOOST_NOEXCEPT
    {  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) BOOST_NOEXCEPT
    {
       if (other_node == this_node)
          return;
       const node_ptr this_next = NodeTraits::get_next(this_node);
       const node_ptr other_next = NodeTraits::get_next(other_node);
       const bool this_null   = !this_next;
       const bool other_null  = !other_next;
       const bool this_empty  = this_next == this_node;
       const bool other_empty = other_next == other_node;
 
       if(!(other_null || other_empty)){
          NodeTraits::set_next(this_next == other_node ? other_node : get_previous_node(other_node), this_node );
       }
       if(!(this_null | this_empty)){
          NodeTraits::set_next(other_next == this_node ? this_node  : get_previous_node(this_node), other_node );
       }
       NodeTraits::set_next(this_node,  other_empty ? this_node  : (other_next == this_node ? other_node : other_next) );
       NodeTraits::set_next(other_node, this_empty  ? other_node : (this_next == other_node ? this_node :  this_next ) );
    }
 
    //! <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) BOOST_NOEXCEPT
    {
       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) BOOST_NOEXCEPT
    {
       //Null shift, nothing to do
       if(!n) return node_ptr();
       node_ptr first  = NodeTraits::get_next(p);
 
       //count() == 1 or 2, nothing to do
       if(NodeTraits::get_next(first) == p)
          return node_ptr();
 
       bool end_found = false;
       node_ptr new_last = node_ptr();
 
       //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();
             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) BOOST_NOEXCEPT
    {
       //Null shift, nothing to do
       if(!n) return node_ptr();
       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();
 
       //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();
 
          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;
    }
 
    //! <b>Requires</b>: other must be a list and p must be a node of a different list.
    //!
    //! <b>Effects</b>: Transfers all nodes from other after p in p's list.
    //!
    //! <b>Complexity</b>: Linear
    //!
    //! <b>Throws</b>: Nothing.
    static void transfer_after(node_ptr p, node_ptr other) BOOST_NOEXCEPT
    {
       node_ptr other_last((get_previous_node)(other));
       base_t::transfer_after(p, other, other_last);
    }
 
    //! <b>Requires</b>: "disposer" must be an object function
    //!   taking a node_ptr parameter and shouldn't throw.
    //!
    //! <b>Effects</b>: Unlinks all nodes reachable from p (but not p) and calls
    //!   <tt>void disposer::operator()(node_ptr)</tt> for every node of the list
    //!    where p is linked.
    //!
    //! <b>Returns</b>: The number of disposed nodes
    //!
    //! <b>Complexity</b>: Linear to the number of element of the list.
    //!
    //! <b>Throws</b>: Nothing.
    template<class Disposer>
    BOOST_INTRUSIVE_FORCEINLINE static std::size_t detach_and_dispose(node_ptr p, Disposer disposer) BOOST_NOEXCEPT
    {  return base_t::unlink_after_and_dispose(p, p, disposer);   }
 };
 
 /// @cond
 
 template<class NodeTraits>
 struct get_algo<CircularSListAlgorithms, NodeTraits>
 {
    typedef circular_slist_algorithms<NodeTraits> type;
 };
 
 /// @endcond
 
 } //namespace intrusive
 } //namespace boost
 
 #include <boost/intrusive/detail/config_end.hpp>
 
 #endif //BOOST_INTRUSIVE_CIRCULAR_SLIST_ALGORITHMS_HPP

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