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

Copyright (c) 1997, 2009, Innobase Oy. All Rights Reserved.

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; version 2 of the License.

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 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., 59 Temple
Place, Suite 330, Boston, MA 02111-1307 USA

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

/**************************************************//**
@file include/read0read.ic
Cursor read

Created 2/16/1997 Heikki Tuuri
*******************************************************/

/*********************************************************************//**
Gets the nth trx id in a read view.
@return	trx id */
UNIV_INLINE
trx_id_t
read_view_get_nth_trx_id(
/*=====================*/
	const read_view_t*	view,	/*!< in: read view */
	ulint			n)	/*!< in: position */
{
	ut_ad(n < view->n_trx_ids);

	return(*(view->trx_ids + n));
}

/*********************************************************************//**
Sets the nth trx id in a read view. */
UNIV_INLINE
void
read_view_set_nth_trx_id(
/*=====================*/
	read_view_t*	view,	/*!< in: read view */
	ulint		n,	/*!< in: position */
	trx_id_t	trx_id)	/*!< in: trx id to set */
{
	ut_ad(n < view->n_trx_ids);

	*(view->trx_ids + n) = trx_id;
}

/*********************************************************************//**
Checks if a read view sees the specified transaction.
@return	TRUE if sees */
UNIV_INLINE
ibool
read_view_sees_trx_id(
/*==================*/
	const read_view_t*	view,	/*!< in: read view */
	trx_id_t		trx_id)	/*!< in: trx id */
{
	ulint	n_ids;
	ulint	i;

	if (trx_id < view->up_limit_id) {

		return(TRUE);
	}

	if (trx_id >= view->low_limit_id) {

		return(FALSE);
	}

	/* We go through the trx ids in the array smallest first: this order
	may save CPU time, because if there was a very long running
	transaction in the trx id array, its trx id is looked at first, and
	the first two comparisons may well decide the visibility of trx_id. */

	n_ids = view->n_trx_ids;

	for (i = 0; i < n_ids; i++) {
		trx_id_t	view_trx_id
			= read_view_get_nth_trx_id(view, n_ids - i - 1);

		if (trx_id <= view_trx_id) {
			return(trx_id != view_trx_id);
		}
	}

	return(TRUE);
}