// <forward_list.tcc> -*- C++ -*-

// Copyright (C) 2008
// Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this library; see the file COPYING.  If not, write to
// the Free Software Foundation, 51 Franklin Street, Fifth Floor,
// Boston, MA 02110-1301, USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

/** @file forward_list.tcc
 *  This is a Standard C++ Library header.
 */

#ifndef _FORWARD_LIST_TCC
#define _FORWARD_LIST_TCC 1

namespace std
{

 /**
  *  @brief  Sort the singly linked list starting after this node.
  *          This node is assumed to be an empty head node (of type
  *          _Fwd_list_node_base).
  */
  template<typename _Tp>
  template<typename _Comp>
  void
  _Fwd_list_node<_Tp>::_M_sort_after(_Comp __comp)
  {
    // If `next' is 0, return immediately.
    _Fwd_list_node* __list = static_cast<_Fwd_list_node*>(this->_M_next);
    if (!__list)
      return;

    unsigned int __insize = 1;

    while (1)
      {
        _Fwd_list_node* __p = __list;
        __list = 0;
        _Fwd_list_node* __tail = 0;

        // Count number of merges we do in this pass.
        unsigned int __nmerges = 0;

        while (__p)
          {
            ++__nmerges;
            // There exists a merge to be done.
            // Step `insize' places along from p.
            _Fwd_list_node* __q = __p;
            unsigned int __psize = 0;
            for (int __i = 0; __i < __insize; ++__i)
              {
                ++__psize;
                __q = static_cast<_Fwd_list_node*>(__q->_M_next);
                if (!__q)
                  break;
              }

            // If q hasn't fallen off end, we have two lists to merge.
            unsigned int __qsize = __insize;

            // Now we have two lists; merge them.
            while (__psize > 0 || (__qsize > 0 && __q))
              {
                // Decide whether next node of merge comes from p or q.
                _Fwd_list_node<_Tp>* __e;
                if (__psize == 0)
                  {
                    // p is empty; e must come from q.
                    __e = __q;
                    __q = static_cast<_Fwd_list_node*>(__q->_M_next);
                    --__qsize;
                  }
                else if (__qsize == 0 || !__q)
                  {
                    // q is empty; e must come from p.
                    __e = __p;
                    __p = static_cast<_Fwd_list_node*>(__p->_M_next);
                    --__psize;
                  }
                else if (__comp(__p->_M_value, __q->_M_value))
                  {
                    // First node of p is lower; e must come from p.
                    __e = __p;
                    __p = static_cast<_Fwd_list_node*>(__p->_M_next);
                    --__psize;
                  }
                else
                  {
                    // First node of q is lower; e must come from q.
                    __e = __q;
                    __q = static_cast<_Fwd_list_node*>(__q->_M_next);
                    --__qsize;
                  }

                // Add the next node to the merged list.
                if (__tail)
                  __tail->_M_next = __e;
                else
                  __list = __e;
                __tail = __e;
            }

            // Now p has stepped `insize' places along, and q has too.
            __p = __q;
        }
        __tail->_M_next = 0;

        // If we have done only one merge, we're finished.
        // Allow for nmerges == 0, the empty list case.
        if (__nmerges <= 1)
          {
            this->_M_next = __list;
            return;
          }

        // Otherwise repeat, merging lists twice the size.
        __insize *= 2;
      }
  }

} // namespace std

#endif /* _FORWARD_LIST_TCC */