/*****************************************************************************

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Copyright (c) 2020, 2021, MariaDB Corporation.

This program is free software; you can redistribute it and/or modify it under
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

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*****************************************************************************/

/**************************************************//**
@file lock/lock0iter.cc
Lock queue iterator. Can iterate over table and record
lock queues.

Created July 16, 2007 Vasil Dimov
*******************************************************/

#define LOCK_MODULE_IMPLEMENTATION

#include "dict0mem.h"
#include "lock0iter.h"
#include "lock0lock.h"
#include "lock0priv.h"

/*******************************************************************//**
Initialize lock queue iterator so that it starts to iterate from
"lock". bit_no specifies the record number within the heap where the
record is stored. It can be undefined (ULINT_UNDEFINED) in two cases:
1. If the lock is a table lock, thus we have a table lock queue;
2. If the lock is a record lock and it is a wait lock. In this case
   bit_no is calculated in this function by using
   lock_rec_find_set_bit(). There is exactly one bit set in the bitmap
   of a wait lock. */
void
lock_queue_iterator_reset(
/*======================*/
	lock_queue_iterator_t*	iter,	/*!< out: iterator */
	const lock_t*		lock,	/*!< in: lock to start from */
	ulint			bit_no)	/*!< in: record number in the
					heap */
{
  lock_sys.assert_locked(*lock);

  iter->current_lock = lock;

  if (bit_no != ULINT_UNDEFINED);
  else if (lock->is_table())
    bit_no= ULINT_UNDEFINED;
  else
  {
    bit_no= lock_rec_find_set_bit(lock);
    ut_ad(bit_no != ULINT_UNDEFINED);
  }

  iter->bit_no= bit_no;
}

/*******************************************************************//**
Gets the previous lock in the lock queue, returns NULL if there are no
more locks (i.e. the current lock is the first one). The iterator is
receded (if not-NULL is returned).
@return previous lock or NULL */
const lock_t*
lock_queue_iterator_get_prev(
/*=========================*/
	lock_queue_iterator_t*	iter)	/*!< in/out: iterator */
{
  lock_sys.assert_locked(*iter->current_lock);

  const lock_t *prev_lock= !iter->current_lock->is_table()
    ? lock_rec_get_prev(iter->current_lock, iter->bit_no)
    : UT_LIST_GET_PREV(un_member.tab_lock.locks, iter->current_lock);

  if (prev_lock)
    iter->current_lock= prev_lock;

  return prev_lock;
}