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

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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,
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as designated in a particular file or component or in included license
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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 "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);
}
