/* Copyright (c) 2000, 2023, Oracle and/or its affiliates.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.

   This program is also distributed with certain software (including
   but not limited to OpenSSL) that is licensed under separate terms,
   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
   separately licensed software that they have included with MySQL.

   This program 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, version 2.0, for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */


/*
things to define before including the file:

#define LS_LIST_ITEM ListItem
#define LS_COMPARE_FUNC_DECL compare_func var_name,
#define LS_COMPARE_FUNC_CALL(list_el1, list_el2) (*var_name)(list_el1, list_el2)
#define LS_NEXT(A) (A)->next
#define LS_SET_NEXT(A,val) (A)->next= val
#define LS_P_NEXT(A) &(A)->next
#define LS_NAME plistsort
#define LS_SCOPE static
#define LS_STRUCT_NAME ls_struct_name
*/

typedef struct LS_STRUCT_NAME
{
  LS_LIST_ITEM *list1;
  int list_len;
  int return_point;
} LS_STRUCT_NAME;

LS_SCOPE LS_LIST_ITEM* LS_NAME(LS_COMPARE_FUNC_DECL LS_LIST_ITEM *list, int list_len)
{
  LS_LIST_ITEM *list_end;
  LS_LIST_ITEM *sorted_list;

  struct LS_STRUCT_NAME stack[63], *sp= stack;

  if (list_len < 2)
    return list;

  sp->list_len= list_len;
  sp->return_point= 2;

recursion_point:

  if (sp->list_len < 4)
  {
    LS_LIST_ITEM *e1, *e2;
    sorted_list= list;
    e1= LS_NEXT(sorted_list);
    list_end= LS_NEXT(e1);
    if (LS_COMPARE_FUNC_CALL(sorted_list, e1))
    {
      sorted_list= e1;
      e1= list;
    }
    if (sp->list_len == 2)
    {
      LS_SET_NEXT(sorted_list, e1);
      LS_SET_NEXT(e1, NULL);
      goto exit_point;
    }
    e2= list_end;
    list_end= LS_NEXT(e2);
    if (LS_COMPARE_FUNC_CALL(e1, e2))
    {
      {
        LS_LIST_ITEM *tmp_e= e1;
        e1= e2;
        e2= tmp_e;
      }
      if (LS_COMPARE_FUNC_CALL(sorted_list, e1))
      {
        LS_LIST_ITEM *tmp_e= sorted_list;
        sorted_list= e1;
        e1= tmp_e;
      }
    }

    LS_SET_NEXT(sorted_list, e1);
    LS_SET_NEXT(e1, e2);
    LS_SET_NEXT(e2, NULL);
    goto exit_point;
  }

  {
    struct LS_STRUCT_NAME *sp0= sp++;
    sp->list_len= sp0->list_len >> 1;
    sp0->list_len-= sp->list_len;
    sp->return_point= 0;
  }
  goto recursion_point;
return_point0:
  sp->list1= sorted_list;
  {
    struct LS_STRUCT_NAME *sp0= sp++;
    list= list_end;
    sp->list_len= sp0->list_len;
    sp->return_point= 1;
  }
  goto recursion_point;
return_point1:
  {
    LS_LIST_ITEM **hook= &sorted_list;
    LS_LIST_ITEM *list1= sp->list1;
    LS_LIST_ITEM *list2= sorted_list;

    if (LS_COMPARE_FUNC_CALL(list1, list2))
    {
      LS_LIST_ITEM *tmp_e= list2;
      list2= list1;
      list1= tmp_e;
    }
    for (;;)
    {
      *hook= list1;
      do
      {
        if (!(list1= *(hook= LS_P_NEXT(list1))))
        {
          *hook= list2;
          goto exit_point;
        }
      } while (LS_COMPARE_FUNC_CALL(list2, list1));

      *hook= list2;
      do
      {
        if (!(list2= *(hook= LS_P_NEXT(list2))))
        {
          *hook= list1;
          goto exit_point;
        }
      } while (LS_COMPARE_FUNC_CALL(list1, list2));
    }
  }

exit_point:
  switch ((sp--)->return_point)
  {
    case 0: goto return_point0;
    case 1: goto return_point1;
    default:;
  }

  return sorted_list;
}


#undef LS_LIST_ITEM
#undef LS_NEXT
#undef LS_SET_NEXT
#undef LS_P_NEXT
#undef LS_NAME
#undef LS_STRUCT_NAME
#undef LS_SCOPE
#undef LS_COMPARE_FUNC_DECL
#undef LS_COMPARE_FUNC_CALL