/* Copyright (c) 2000, 2002, 2005-2007 MySQL AB
   Use is subject to license terms

   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 Street, Fifth Floor, Boston, MA 02110-1301, USA */

#include "heapdef.h"

/* Read next record with the same key */

int heap_rnext(HP_INFO *info, uchar *record)
{
  uchar *pos;
  HP_SHARE *share=info->s;
  HP_KEYDEF *keyinfo;
  DBUG_ENTER("heap_rnext");
  
  if (info->lastinx < 0)
    DBUG_RETURN(my_errno=HA_ERR_WRONG_INDEX);

  keyinfo = share->keydef + info->lastinx;
  if (keyinfo->algorithm == HA_KEY_ALG_BTREE)
  {
    heap_rb_param custom_arg;

    if (info->last_pos)
    {
      /*
        We enter this branch for non-DELETE queries after heap_rkey()
        or heap_rfirst(). As last key position (info->last_pos) is available,
        we only need to climb the tree using tree_search_next().
      */
      pos = tree_search_next(&keyinfo->rb_tree, &info->last_pos,
                             offsetof(TREE_ELEMENT, left),
                             offsetof(TREE_ELEMENT, right));
    }
    else if (!info->lastkey_len)
    {
      /*
        We enter this branch only for DELETE queries after heap_rfirst(). E.g.
        DELETE FROM t1 WHERE a<10. As last key position is not available
        (last key is removed by heap_delete()), we must restart search as it
        is done in heap_rfirst().

        It should be safe to handle this situation without this branch. That is
        branch below should find smallest element in a tree as lastkey_len is
        zero. tree_search_edge() is a kind of optimisation here as it should be
        faster than tree_search_key().
      */
      pos= tree_search_edge(&keyinfo->rb_tree, info->parents,
                            &info->last_pos, offsetof(TREE_ELEMENT, left));
    }
    else
    {
      /*
        We enter this branch only for DELETE queries after heap_rkey(). E.g.
        DELETE FROM t1 WHERE a=10. As last key position is not available
        (last key is removed by heap_delete()), we must restart search as it
        is done in heap_rkey().
      */
      custom_arg.keyseg = keyinfo->seg;
      custom_arg.key_length = info->lastkey_len;
      custom_arg.search_flag = SEARCH_SAME | SEARCH_FIND;
      pos = tree_search_key(&keyinfo->rb_tree, info->lastkey, info->parents, 
                           &info->last_pos, info->last_find_flag, &custom_arg);
    }
    if (pos)
    {
      memcpy(&pos, pos + (*keyinfo->get_key_length)(keyinfo, pos), 
	     sizeof(uchar*));
      info->current_ptr = pos;
    }
    else
    {
      my_errno = HA_ERR_KEY_NOT_FOUND;
    }
  }
  else
  {
    if (info->current_hash_ptr)
      pos= hp_search_next(info, keyinfo, info->lastkey,
			   info->current_hash_ptr);
    else
    {
      if (!info->current_ptr && (info->update & HA_STATE_NEXT_FOUND))
      {
	pos=0;					/* Read next after last */
	my_errno=HA_ERR_KEY_NOT_FOUND;
      }
      else if (!info->current_ptr)		/* Deleted or first call */
	pos= hp_search(info, keyinfo, info->lastkey, 0);
      else
	pos= hp_search(info, keyinfo, info->lastkey, 1);
    }
  }
  if (!pos)
  {
    info->update=HA_STATE_NEXT_FOUND;		/* For heap_rprev */
    if (my_errno == HA_ERR_KEY_NOT_FOUND)
      my_errno=HA_ERR_END_OF_FILE;
    DBUG_RETURN(my_errno);
  }
  memcpy(record,pos,(size_t) share->reclength);
  info->update=HA_STATE_AKTIV | HA_STATE_NEXT_FOUND;
  DBUG_RETURN(0);
}
