lock0iter.cc

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

Copyright (c) 2007, 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 Street, Suite 500, Boston, MA 02110-1335 USA

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

/**************************************************//**
@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 "univ.i"
#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 */
{
	ut_ad(lock_mutex_own());

	iter->current_lock = lock;

	if (bit_no != ULINT_UNDEFINED) {

		iter->bit_no = bit_no;
	} else {

		switch (lock_get_type_low(lock)) {
		case LOCK_TABLE:
			iter->bit_no = ULINT_UNDEFINED;
			break;
		case LOCK_REC:
			iter->bit_no = lock_rec_find_set_bit(lock);
			ut_a(iter->bit_no != ULINT_UNDEFINED);
			break;
		default:
			ut_error;
		}
	}
}

/*******************************************************************//**
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 */
{
	const lock_t*	prev_lock;

	ut_ad(lock_mutex_own());

	switch (lock_get_type_low(iter->current_lock)) {
	case LOCK_REC:
		prev_lock = lock_rec_get_prev(
			iter->current_lock, iter->bit_no);
		break;
	case LOCK_TABLE:
		prev_lock = UT_LIST_GET_PREV(
			un_member.tab_lock.locks, iter->current_lock);
		break;
	default:
		ut_error;
	}

	if (prev_lock != NULL) {

		iter->current_lock = prev_lock;
	}

	return(prev_lock);
}