/******************************************************
Rollback segment

(c) 1996 Innobase Oy

Created 3/26/1996 Heikki Tuuri
*******************************************************/

#include "srv0srv.h"

/**********************************************************************
Gets a rollback segment header. */
UNIV_INLINE
trx_rsegf_t*
trx_rsegf_get(
/*==========*/
				/* out: rollback segment header, page
				x-latched */
	ulint	space,		/* in: space where placed */
	ulint	page_no,	/* in: page number of the header */
	mtr_t*	mtr)		/* in: mtr */
{
	trx_rsegf_t*	header;

	header = TRX_RSEG + buf_page_get(space, page_no, RW_X_LATCH, mtr);

#ifdef UNIV_SYNC_DEBUG
	buf_page_dbg_add_level(header, SYNC_RSEG_HEADER);
#endif /* UNIV_SYNC_DEBUG */

	return(header);
}

/**********************************************************************
Gets a newly created rollback segment header. */
UNIV_INLINE
trx_rsegf_t*
trx_rsegf_get_new(
/*==============*/
				/* out: rollback segment header, page
				x-latched */
	ulint	space,		/* in: space where placed */
	ulint	page_no,	/* in: page number of the header */
	mtr_t*	mtr)		/* in: mtr */
{
	trx_rsegf_t*	header;

	header = TRX_RSEG + buf_page_get(space, page_no, RW_X_LATCH, mtr);

#ifdef UNIV_SYNC_DEBUG
	buf_page_dbg_add_level(header, SYNC_RSEG_HEADER_NEW);
#endif /* UNIV_SYNC_DEBUG */

	return(header);
}

/*******************************************************************
Gets the file page number of the nth undo log slot. */
UNIV_INLINE
ulint
trx_rsegf_get_nth_undo(
/*===================*/
				/* out: page number of the undo log segment */
	trx_rsegf_t*	rsegf,	/* in: rollback segment header */
	ulint		n,	/* in: index of slot */
	mtr_t*		mtr)	/* in: mtr */
{
	if (n >= TRX_RSEG_N_SLOTS) {
		fprintf(stderr,
		"InnoDB: Error: trying to get slot %lu of rseg\n", (unsigned long) n);
		ut_error;
	}

	return(mtr_read_ulint(rsegf + TRX_RSEG_UNDO_SLOTS +
				n * TRX_RSEG_SLOT_SIZE, MLOG_4BYTES, mtr));
}

/*******************************************************************
Sets the file page number of the nth undo log slot. */
UNIV_INLINE
void
trx_rsegf_set_nth_undo(
/*===================*/
	trx_rsegf_t*	rsegf,	/* in: rollback segment header */
	ulint		n,	/* in: index of slot */
	ulint		page_no,/* in: page number of the undo log segment */
	mtr_t*		mtr)	/* in: mtr */
{
	if (n >= TRX_RSEG_N_SLOTS) {
		fprintf(stderr,
		"InnoDB: Error: trying to set slot %lu of rseg\n", (unsigned long) n);
		ut_error;
	}

	mlog_write_ulint(rsegf + TRX_RSEG_UNDO_SLOTS + n * TRX_RSEG_SLOT_SIZE,
						page_no, MLOG_4BYTES, mtr);
}

/********************************************************************
Looks for a free slot for an undo log segment. */
UNIV_INLINE
ulint
trx_rsegf_undo_find_free(
/*=====================*/
				/* out: slot index or ULINT_UNDEFINED if not
				found */
	trx_rsegf_t*	rsegf,	/* in: rollback segment header */
	mtr_t*		mtr)	/* in: mtr */
{
	ulint		i;
	ulint		page_no;
	
	for (i = 0; i < TRX_RSEG_N_SLOTS; i++) {

		page_no = trx_rsegf_get_nth_undo(rsegf, i, mtr);

		if (page_no == FIL_NULL) {

			return(i);
		}
	}

	return(ULINT_UNDEFINED);
}