/* Copyright (c) 2005, 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,
   51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA */

#ifndef TABLE_MAPPING_H
#define TABLE_MAPPING_H

#include "my_global.h"
#include "hash.h"        // HASH

/* Forward declarations */
#ifndef MYSQL_CLIENT
struct TABLE;
#else
class Table_map_log_event;
typedef Table_map_log_event TABLE;
void free_table_map_log_event(TABLE *table);
#endif


/*
  CLASS table_mapping

  RESPONSIBILITIES
    The table mapping is used to map table id's to table pointers

  COLLABORATION
    RELAY_LOG    For mapping table id:s to tables when receiving events.
 */

/*
  Guilhem to Mats:
  in the table_mapping class, the memory is allocated and never freed (until
  destruction). So this is a good candidate for allocating inside a MEM_ROOT:
  it gives the efficient allocation in chunks (like in expand()). So I have
  introduced a MEM_ROOT.

  Note that inheriting from Sql_alloc had no effect: it has effects only when
  "ptr= new table_mapping" is called, and this is never called. And it would
  then allocate from thd->mem_root which is a highly volatile object (reset
  from example after executing each query, see dispatch_command(), it has a
  free_root() at end); as the table_mapping object is supposed to live longer
  than a query, it was dangerous.
  A dedicated MEM_ROOT needs to be used, see below.
*/

class table_mapping {

private:
  MEM_ROOT m_mem_root;

public:

  enum enum_error {
      ERR_NO_ERROR = 0,
      ERR_LIMIT_EXCEEDED,
      ERR_MEMORY_ALLOCATION
  };

  table_mapping();
  ~table_mapping();

  TABLE* get_table(ulonglong table_id);

  int       set_table(ulonglong table_id, TABLE* table);
  int       remove_table(ulonglong table_id);
  void      clear_tables();
  ulong     count() const { return m_table_ids.records; }

private:
  /*
    This is a POD (Plain Old Data).  Keep it that way (we apply offsetof() to
    it, which only works for PODs)
  */
  struct entry { 
    ulonglong table_id;
    union {
      TABLE *table;
      entry *next;
    };
  };

  entry *find_entry(ulonglong table_id)
  {
    return (entry *) my_hash_search(&m_table_ids,
                                    (uchar*)&table_id,
                                    sizeof(table_id));
  }
  int expand();

  /*
    Head of the list of free entries; "free" in the sense that it's an
    allocated entry free for use, NOT in the sense that it's freed
    memory.
  */
  entry *m_free;

  /* Correspondance between an id (a number) and a TABLE object */
  HASH m_table_ids;
};

#endif