innobase/include/page0page.ic

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

Copyright (c) 1994, 2021, 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 include/page0page.ic
Index page routines

Created 2/2/1994 Heikki Tuuri
*******************************************************/

#include "mach0data.h"
#ifndef UNIV_INNOCHECKSUM
#ifdef UNIV_DEBUG
# include "log0recv.h"
#endif /* !UNIV_DEBUG */
#ifndef UNIV_HOTBACKUP
# include "rem0cmp.h"
#endif /* !UNIV_HOTBACKUP */
#include "mtr0log.h"
#include "page0zip.h"

#ifdef UNIV_MATERIALIZE
#undef UNIV_INLINE
#define UNIV_INLINE
#endif

/************************************************************//**
Gets the start of a page.
@return start of the page */
UNIV_INLINE
page_t*
page_align(
/*=======*/
	const void*	ptr)	/*!< in: pointer to page frame */
{
	return((page_t*) ut_align_down(ptr, UNIV_PAGE_SIZE));
}
/************************************************************//**
Gets the offset within a page.
@return offset from the start of the page */
UNIV_INLINE
ulint
page_offset(
/*========*/
	const void*	ptr)	/*!< in: pointer to page frame */
{
	return(ut_align_offset(ptr, UNIV_PAGE_SIZE));
}
/*************************************************************//**
Returns the max trx id field value. */
UNIV_INLINE
trx_id_t
page_get_max_trx_id(
/*================*/
	const page_t*	page)	/*!< in: page */
{
	ut_ad(page);

	return(mach_read_from_8(page + PAGE_HEADER + PAGE_MAX_TRX_ID));
}

/*************************************************************//**
Sets the max trx id field value if trx_id is bigger than the previous
value. */
UNIV_INLINE
void
page_update_max_trx_id(
/*===================*/
	buf_block_t*	block,	/*!< in/out: page */
	page_zip_des_t*	page_zip,/*!< in/out: compressed page whose
				uncompressed part will be updated, or NULL */
	trx_id_t	trx_id,	/*!< in: transaction id */
	mtr_t*		mtr)	/*!< in/out: mini-transaction */
{
	ut_ad(block);
	ut_ad(mtr_memo_contains(mtr, block, MTR_MEMO_PAGE_X_FIX));
	/* During crash recovery, this function may be called on
	something else than a leaf page of a secondary index or the
	insert buffer index tree (dict_index_is_sec_or_ibuf() returns
	TRUE for the dummy indexes constructed during redo log
	application).  In that case, PAGE_MAX_TRX_ID is unused,
	and trx_id is usually zero. */
	ut_ad(trx_id || recv_recovery_is_on());
	ut_ad(page_is_leaf(buf_block_get_frame(block)));

	if (page_get_max_trx_id(buf_block_get_frame(block)) < trx_id) {

		page_set_max_trx_id(block, page_zip, trx_id, mtr);
	}
}

/*************************************************************//**
Returns the RTREE SPLIT SEQUENCE NUMBER (FIL_RTREE_SPLIT_SEQ_NUM).
@return	SPLIT SEQUENCE NUMBER */
UNIV_INLINE
node_seq_t
page_get_ssn_id(
/*============*/
	const page_t*	page)	/*!< in: page */
{
	ut_ad(page);

	return(static_cast<node_seq_t>(
		mach_read_from_8(page + FIL_RTREE_SPLIT_SEQ_NUM)));
}

/*************************************************************//**
Sets the RTREE SPLIT SEQUENCE NUMBER field value */
UNIV_INLINE
void
page_set_ssn_id(
/*============*/
	buf_block_t*	block,	/*!< in/out: page */
	page_zip_des_t*	page_zip,/*!< in/out: compressed page whose
				uncompressed part will be updated, or NULL */
	node_seq_t	ssn_id,	/*!< in: transaction id */
	mtr_t*		mtr)	/*!< in/out: mini-transaction */
{
	page_t*	page = buf_block_get_frame(block);
#ifndef UNIV_HOTBACKUP
	ut_ad(!mtr || mtr_memo_contains(mtr, block, MTR_MEMO_PAGE_SX_FIX)
	      || mtr_memo_contains(mtr, block, MTR_MEMO_PAGE_X_FIX));
#endif /* !UNIV_HOTBACKUP */

	if (page_zip) {
		mach_write_to_8(page + FIL_RTREE_SPLIT_SEQ_NUM, ssn_id);
		page_zip_write_header(page_zip,
				      page + FIL_RTREE_SPLIT_SEQ_NUM,
				      8, mtr);
#ifndef UNIV_HOTBACKUP
	} else if (mtr) {
		mlog_write_ull(page + FIL_RTREE_SPLIT_SEQ_NUM, ssn_id, mtr);
#endif /* !UNIV_HOTBACKUP */
	} else {
		mach_write_to_8(page + FIL_RTREE_SPLIT_SEQ_NUM, ssn_id);
	}
}

#endif /* !UNIV_INNOCHECKSUM */

/*************************************************************//**
Reads the given header field. */
UNIV_INLINE
ulint
page_header_get_field(
/*==================*/
	const page_t*	page,	/*!< in: page */
	ulint		field)	/*!< in: PAGE_LEVEL, ... */
{
	ut_ad(page);
	ut_ad(field <= PAGE_INDEX_ID);

	return(mach_read_from_2(page + PAGE_HEADER + field));
}

#ifndef UNIV_INNOCHECKSUM

/*************************************************************//**
Sets the given header field. */
UNIV_INLINE
void
page_header_set_field(
/*==================*/
	page_t*		page,	/*!< in/out: page */
	page_zip_des_t*	page_zip,/*!< in/out: compressed page whose
				uncompressed part will be updated, or NULL */
	ulint		field,	/*!< in: PAGE_N_DIR_SLOTS, ... */
	ulint		val)	/*!< in: value */
{
	ut_ad(page);
	ut_ad(field <= PAGE_N_RECS);
	ut_ad(field == PAGE_N_HEAP || val < UNIV_PAGE_SIZE);
	ut_ad(field != PAGE_N_HEAP || (val & 0x7fff) < UNIV_PAGE_SIZE);

	mach_write_to_2(page + PAGE_HEADER + field, val);
	if (page_zip) {
		page_zip_write_header(page_zip,
				      page + PAGE_HEADER + field, 2, NULL);
	}
}

/*************************************************************//**
Returns the offset stored in the given header field.
@return offset from the start of the page, or 0 */
UNIV_INLINE
ulint
page_header_get_offs(
/*=================*/
	const page_t*	page,	/*!< in: page */
	ulint		field)	/*!< in: PAGE_FREE, ... */
{
	ulint	offs;

	ut_ad(page);
	ut_ad((field == PAGE_FREE)
	      || (field == PAGE_LAST_INSERT)
	      || (field == PAGE_HEAP_TOP));

	offs = page_header_get_field(page, field);

	ut_ad((field != PAGE_HEAP_TOP) || offs);

	return(offs);
}

/*************************************************************//**
Sets the pointer stored in the given header field. */
UNIV_INLINE
void
page_header_set_ptr(
/*================*/
	page_t*		page,	/*!< in: page */
	page_zip_des_t*	page_zip,/*!< in/out: compressed page whose
				uncompressed part will be updated, or NULL */
	ulint		field,	/*!< in: PAGE_FREE, ... */
	const byte*	ptr)	/*!< in: pointer or NULL*/
{
	ulint	offs;

	ut_ad(page);
	ut_ad((field == PAGE_FREE)
	      || (field == PAGE_LAST_INSERT)
	      || (field == PAGE_HEAP_TOP));

	if (ptr == NULL) {
		offs = 0;
	} else {
		offs = ptr - page;
	}

	ut_ad((field != PAGE_HEAP_TOP) || offs);

	page_header_set_field(page, page_zip, field, offs);
}

#ifndef UNIV_HOTBACKUP
/*************************************************************//**
Resets the last insert info field in the page header. Writes to mlog
about this operation. */
UNIV_INLINE
void
page_header_reset_last_insert(
/*==========================*/
	page_t*		page,	/*!< in/out: page */
	page_zip_des_t*	page_zip,/*!< in/out: compressed page whose
				uncompressed part will be updated, or NULL */
	mtr_t*		mtr)	/*!< in: mtr */
{
	ut_ad(page != NULL);
	ut_ad(mtr != NULL);

	if (page_zip) {
		mach_write_to_2(page + (PAGE_HEADER + PAGE_LAST_INSERT), 0);
		page_zip_write_header(page_zip,
				      page + (PAGE_HEADER + PAGE_LAST_INSERT),
				      2, mtr);
	} else {
		mlog_write_ulint(page + (PAGE_HEADER + PAGE_LAST_INSERT), 0,
				 MLOG_2BYTES, mtr);
	}
}
#endif /* !UNIV_HOTBACKUP */

/************************************************************//**
Determine whether the page is in new-style compact format.
@return nonzero if the page is in compact format, zero if it is in
old-style format */
UNIV_INLINE
ulint
page_is_comp(
/*=========*/
	const page_t*	page)	/*!< in: index page */
{
	return(page_header_get_field(page, PAGE_N_HEAP) & 0x8000);
}

/************************************************************//**
TRUE if the record is on a page in compact format.
@return nonzero if in compact format */
UNIV_INLINE
ulint
page_rec_is_comp(
/*=============*/
	const rec_t*	rec)	/*!< in: record */
{
	return(page_is_comp(page_align(rec)));
}

/***************************************************************//**
Returns the heap number of a record.
@return heap number */
UNIV_INLINE
ulint
page_rec_get_heap_no(
/*=================*/
	const rec_t*	rec)	/*!< in: the physical record */
{
	if (page_rec_is_comp(rec)) {
		return(rec_get_heap_no_new(rec));
	} else {
		return(rec_get_heap_no_old(rec));
	}
}

/************************************************************//**
Determine whether the page is a B-tree leaf.
@return true if the page is a B-tree leaf (PAGE_LEVEL = 0) */
UNIV_INLINE
bool
page_is_leaf(
/*=========*/
	const page_t*	page)	/*!< in: page */
{
	if (!page) {
		return(false);
	}
	return(!*(const uint16*) (page + (PAGE_HEADER + PAGE_LEVEL)));
}

/************************************************************//**
Determine whether the page is empty.
@return true if the page is empty (PAGE_N_RECS = 0) */
UNIV_INLINE
bool
page_is_empty(
/*==========*/
	const page_t*	page)	/*!< in: page */
{
	return(!*(const uint16*) (page + (PAGE_HEADER + PAGE_N_RECS)));
}

/** Determine whether a page is an index root page.
@param[in]	page	page frame
@return true if the page is a root page of an index */
UNIV_INLINE
bool
page_is_root(
	const page_t*	page)
{
#if FIL_PAGE_PREV % 8
# error FIL_PAGE_PREV must be 64-bit aligned
#endif
#if FIL_PAGE_NEXT != FIL_PAGE_PREV + 4
# error FIL_PAGE_NEXT must be adjacent to FIL_PAGE_PREV
#endif
#if FIL_NULL != 0xffffffff
# error FIL_NULL != 0xffffffff
#endif
	/* Check that this is an index page and both the PREV and NEXT
	pointers are FIL_NULL, because the root page does not have any
	siblings. */
	return(fil_page_index_page_check(page)
	       && *reinterpret_cast<const ib_uint64_t*>(page + FIL_PAGE_PREV)
	       == IB_UINT64_MAX);
}

/************************************************************//**
Determine whether the page contains garbage.
@return true if the page contains garbage (PAGE_GARBAGE is not 0) */
UNIV_INLINE
bool
page_has_garbage(
/*=============*/
	const page_t*	page)	/*!< in: page */
{
	return(!!*(const uint16*) (page + (PAGE_HEADER + PAGE_GARBAGE)));
}

/************************************************************//**
Gets the offset of the first record on the page.
@return offset of the first record in record list, relative from page */
UNIV_INLINE
ulint
page_get_infimum_offset(
/*====================*/
	const page_t*	page)	/*!< in: page which must have record(s) */
{
	ut_ad(page);
	ut_ad(!page_offset(page));

	if (page_is_comp(page)) {
		return(PAGE_NEW_INFIMUM);
	} else {
		return(PAGE_OLD_INFIMUM);
	}
}

/************************************************************//**
Gets the offset of the last record on the page.
@return offset of the last record in record list, relative from page */
UNIV_INLINE
ulint
page_get_supremum_offset(
/*=====================*/
	const page_t*	page)	/*!< in: page which must have record(s) */
{
	ut_ad(page);
	ut_ad(!page_offset(page));

	if (page_is_comp(page)) {
		return(PAGE_NEW_SUPREMUM);
	} else {
		return(PAGE_OLD_SUPREMUM);
	}
}

/************************************************************//**
TRUE if the record is a user record on the page.
@return TRUE if a user record */
UNIV_INLINE
ibool
page_rec_is_user_rec_low(
/*=====================*/
	ulint	offset)	/*!< in: record offset on page */
{
	ut_ad(offset >= PAGE_NEW_INFIMUM);
#if PAGE_OLD_INFIMUM < PAGE_NEW_INFIMUM
# error "PAGE_OLD_INFIMUM < PAGE_NEW_INFIMUM"
#endif
#if PAGE_OLD_SUPREMUM < PAGE_NEW_SUPREMUM
# error "PAGE_OLD_SUPREMUM < PAGE_NEW_SUPREMUM"
#endif
#if PAGE_NEW_INFIMUM > PAGE_OLD_SUPREMUM
# error "PAGE_NEW_INFIMUM > PAGE_OLD_SUPREMUM"
#endif
#if PAGE_OLD_INFIMUM > PAGE_NEW_SUPREMUM
# error "PAGE_OLD_INFIMUM > PAGE_NEW_SUPREMUM"
#endif
#if PAGE_NEW_SUPREMUM > PAGE_OLD_SUPREMUM_END
# error "PAGE_NEW_SUPREMUM > PAGE_OLD_SUPREMUM_END"
#endif
#if PAGE_OLD_SUPREMUM > PAGE_NEW_SUPREMUM_END
# error "PAGE_OLD_SUPREMUM > PAGE_NEW_SUPREMUM_END"
#endif
	ut_ad(offset <= UNIV_PAGE_SIZE - PAGE_EMPTY_DIR_START);

	return(offset != PAGE_NEW_SUPREMUM
	       && offset != PAGE_NEW_INFIMUM
	       && offset != PAGE_OLD_INFIMUM
	       && offset != PAGE_OLD_SUPREMUM);
}

/************************************************************//**
TRUE if the record is the supremum record on a page.
@return TRUE if the supremum record */
UNIV_INLINE
ibool
page_rec_is_supremum_low(
/*=====================*/
	ulint	offset)	/*!< in: record offset on page */
{
	ut_ad(offset >= PAGE_NEW_INFIMUM);
	ut_ad(offset <= UNIV_PAGE_SIZE - PAGE_EMPTY_DIR_START);

	return(offset == PAGE_NEW_SUPREMUM
	       || offset == PAGE_OLD_SUPREMUM);
}

/************************************************************//**
TRUE if the record is the infimum record on a page.
@return TRUE if the infimum record */
UNIV_INLINE
ibool
page_rec_is_infimum_low(
/*====================*/
	ulint	offset)	/*!< in: record offset on page */
{
	ut_ad(offset >= PAGE_NEW_INFIMUM);
	ut_ad(offset <= UNIV_PAGE_SIZE - PAGE_EMPTY_DIR_START);

	return(offset == PAGE_NEW_INFIMUM || offset == PAGE_OLD_INFIMUM);
}

/************************************************************//**
TRUE if the record is a user record on the page.
@return TRUE if a user record */
UNIV_INLINE
ibool
page_rec_is_user_rec(
/*=================*/
	const rec_t*	rec)	/*!< in: record */
{
	ut_ad(page_rec_check(rec));

	return(page_rec_is_user_rec_low(page_offset(rec)));
}

/************************************************************//**
TRUE if the record is the supremum record on a page.
@return TRUE if the supremum record */
UNIV_INLINE
ibool
page_rec_is_supremum(
/*=================*/
	const rec_t*	rec)	/*!< in: record */
{
	ut_ad(page_rec_check(rec));

	return(page_rec_is_supremum_low(page_offset(rec)));
}

/************************************************************//**
TRUE if the record is the infimum record on a page.
@return TRUE if the infimum record */
UNIV_INLINE
ibool
page_rec_is_infimum(
/*================*/
	const rec_t*	rec)	/*!< in: record */
{
	ut_ad(page_rec_check(rec));

	return(page_rec_is_infimum_low(page_offset(rec)));
}

/************************************************************//**
true if the record is the first user record on a page.
@return true if the first user record */
UNIV_INLINE
bool
page_rec_is_first(
/*==============*/
	const rec_t*	rec,	/*!< in: record */
	const page_t*	page)	/*!< in: page */
{
	ut_ad(page_get_n_recs(page) > 0);

	return(page_rec_get_next_const(page_get_infimum_rec(page)) == rec);
}

/************************************************************//**
true if the record is the second user record on a page.
@return true if the second user record */
UNIV_INLINE
bool
page_rec_is_second(
/*===============*/
	const rec_t*	rec,	/*!< in: record */
	const page_t*	page)	/*!< in: page */
{
	ut_ad(page_get_n_recs(page) > 1);

	return(page_rec_get_next_const(
		page_rec_get_next_const(page_get_infimum_rec(page))) == rec);
}

/************************************************************//**
true if the record is the last user record on a page.
@return true if the last user record */
UNIV_INLINE
bool
page_rec_is_last(
/*=============*/
	const rec_t*	rec,	/*!< in: record */
	const page_t*	page)	/*!< in: page */
{
	ut_ad(page_get_n_recs(page) > 0);

	return(page_rec_get_next_const(rec) == page_get_supremum_rec(page));
}

/************************************************************//**
true if distance between the records (measured in number of times we have to
move to the next record) is at most the specified value */
UNIV_INLINE
bool
page_rec_distance_is_at_most(
/*=========================*/
	const rec_t*	left_rec,
	const rec_t*	right_rec,
	ulint		val)
{
	for (ulint i = 0; i <= val; i++) {
		if (left_rec == right_rec) {
			return (true);
		}
		left_rec = page_rec_get_next_const(left_rec);
	}
	return (false);
}

/************************************************************//**
true if the record is the second last user record on a page.
@return true if the second last user record */
UNIV_INLINE
bool
page_rec_is_second_last(
/*====================*/
	const rec_t*	rec,	/*!< in: record */
	const page_t*	page)	/*!< in: page */
{
	ut_ad(page_get_n_recs(page) > 1);
	ut_ad(!page_rec_is_last(rec, page));

	return(page_rec_get_next_const(
		page_rec_get_next_const(rec)) == page_get_supremum_rec(page));
}

/************************************************************//**
Returns the nth record of the record list.
This is the inverse function of page_rec_get_n_recs_before().
@return nth record */
UNIV_INLINE
rec_t*
page_rec_get_nth(
/*=============*/
	page_t*	page,	/*!< in: page */
	ulint	nth)	/*!< in: nth record */
{
	return((rec_t*) page_rec_get_nth_const(page, nth));
}

#ifndef UNIV_HOTBACKUP
/************************************************************//**
Returns the middle record of the records on the page. If there is an
even number of records in the list, returns the first record of the
upper half-list.
@return middle record */
UNIV_INLINE
rec_t*
page_get_middle_rec(
/*================*/
	page_t*	page)	/*!< in: page */
{
	ulint	middle = (page_get_n_recs(page) + PAGE_HEAP_NO_USER_LOW) / 2;

	return(page_rec_get_nth(page, middle));
}
#endif /* !UNIV_HOTBACKUP */

/*************************************************************//**
Gets the page number.
@return page number */
UNIV_INLINE
ulint
page_get_page_no(
/*=============*/
	const page_t*	page)	/*!< in: page */
{
	ut_ad(page == page_align((page_t*) page));
	return(mach_read_from_4(page + FIL_PAGE_OFFSET));
}

/*************************************************************//**
Gets the tablespace identifier.
@return space id */
UNIV_INLINE
ulint
page_get_space_id(
/*==============*/
	const page_t*	page)	/*!< in: page */
{
	ut_ad(page == page_align((page_t*) page));
	return(mach_read_from_4(page + FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID));
}

/*************************************************************//**
Gets the number of user records on page (infimum and supremum records
are not user records).
@return number of user records */
UNIV_INLINE
ulint
page_get_n_recs(
/*============*/
	const page_t*	page)	/*!< in: index page */
{
	return(page_header_get_field(page, PAGE_N_RECS));
}

/*************************************************************//**
Gets the number of dir slots in directory.
@return number of slots */
UNIV_INLINE
ulint
page_dir_get_n_slots(
/*=================*/
	const page_t*	page)	/*!< in: index page */
{
	return(page_header_get_field(page, PAGE_N_DIR_SLOTS));
}
/*************************************************************//**
Sets the number of dir slots in directory. */
UNIV_INLINE
void
page_dir_set_n_slots(
/*=================*/
	page_t*		page,	/*!< in/out: page */
	page_zip_des_t*	page_zip,/*!< in/out: compressed page whose
				uncompressed part will be updated, or NULL */
	ulint		n_slots)/*!< in: number of slots */
{
	page_header_set_field(page, page_zip, PAGE_N_DIR_SLOTS, n_slots);
}

/*************************************************************//**
Gets the number of records in the heap.
@return number of user records */
UNIV_INLINE
ulint
page_dir_get_n_heap(
/*================*/
	const page_t*	page)	/*!< in: index page */
{
	return(page_header_get_field(page, PAGE_N_HEAP) & 0x7fff);
}

/*************************************************************//**
Sets the number of records in the heap. */
UNIV_INLINE
void
page_dir_set_n_heap(
/*================*/
	page_t*		page,	/*!< in/out: index page */
	page_zip_des_t*	page_zip,/*!< in/out: compressed page whose
				uncompressed part will be updated, or NULL.
				Note that the size of the dense page directory
				in the compressed page trailer is
				n_heap * PAGE_ZIP_DIR_SLOT_SIZE. */
	ulint		n_heap)	/*!< in: number of records */
{
	ut_ad(n_heap < 0x8000);
	ut_ad(!page_zip || n_heap
	      == (page_header_get_field(page, PAGE_N_HEAP) & 0x7fff) + 1);

	page_header_set_field(page, page_zip, PAGE_N_HEAP, n_heap
			      | (0x8000
				 & page_header_get_field(page, PAGE_N_HEAP)));
}

#ifdef UNIV_DEBUG
/*************************************************************//**
Gets pointer to nth directory slot.
@return pointer to dir slot */
UNIV_INLINE
page_dir_slot_t*
page_dir_get_nth_slot(
/*==================*/
	const page_t*	page,	/*!< in: index page */
	ulint		n)	/*!< in: position */
{
	ut_ad(page_dir_get_n_slots(page) > n);

	return((page_dir_slot_t*)
	       page + UNIV_PAGE_SIZE - PAGE_DIR
	       - (n + 1) * PAGE_DIR_SLOT_SIZE);
}
#endif /* UNIV_DEBUG */

/**************************************************************//**
Used to check the consistency of a record on a page.
@return TRUE if succeed */
UNIV_INLINE
ibool
page_rec_check(
/*===========*/
	const rec_t*	rec)	/*!< in: record */
{
	const page_t*	page = page_align(rec);

	ut_a(rec);

	ut_a(page_offset(rec) <= page_header_get_field(page, PAGE_HEAP_TOP));
	ut_a(page_offset(rec) >= PAGE_DATA);

	return(TRUE);
}

/***************************************************************//**
Gets the record pointed to by a directory slot.
@return pointer to record */
UNIV_INLINE
const rec_t*
page_dir_slot_get_rec(
/*==================*/
	const page_dir_slot_t*	slot)	/*!< in: directory slot */
{
	return(page_align(slot) + mach_read_from_2(slot));
}

/***************************************************************//**
This is used to set the record offset in a directory slot. */
UNIV_INLINE
void
page_dir_slot_set_rec(
/*==================*/
	page_dir_slot_t* slot,	/*!< in: directory slot */
	rec_t*		 rec)	/*!< in: record on the page */
{
	ut_ad(page_rec_check(rec));

	mach_write_to_2(slot, page_offset(rec));
}

/***************************************************************//**
Gets the number of records owned by a directory slot.
@return number of records */
UNIV_INLINE
ulint
page_dir_slot_get_n_owned(
/*======================*/
	const page_dir_slot_t*	slot)	/*!< in: page directory slot */
{
	const rec_t*	rec	= page_dir_slot_get_rec(slot);
	if (page_rec_is_comp(slot)) {
		return(rec_get_n_owned_new(rec));
	} else {
		return(rec_get_n_owned_old(rec));
	}
}

/***************************************************************//**
This is used to set the owned records field of a directory slot. */
UNIV_INLINE
void
page_dir_slot_set_n_owned(
/*======================*/
	page_dir_slot_t*slot,	/*!< in/out: directory slot */
	page_zip_des_t*	page_zip,/*!< in/out: compressed page, or NULL */
	ulint		n)	/*!< in: number of records owned by the slot */
{
	rec_t*	rec	= (rec_t*) page_dir_slot_get_rec(slot);
	if (page_rec_is_comp(slot)) {
		rec_set_n_owned_new(rec, page_zip, n);
	} else {
		ut_ad(!page_zip);
		rec_set_n_owned_old(rec, n);
	}
}

/************************************************************//**
Calculates the space reserved for directory slots of a given number of
records. The exact value is a fraction number n * PAGE_DIR_SLOT_SIZE /
PAGE_DIR_SLOT_MIN_N_OWNED, and it is rounded upwards to an integer. */
UNIV_INLINE
ulint
page_dir_calc_reserved_space(
/*=========================*/
	ulint	n_recs)		/*!< in: number of records */
{
	return((PAGE_DIR_SLOT_SIZE * n_recs + PAGE_DIR_SLOT_MIN_N_OWNED - 1)
	       / PAGE_DIR_SLOT_MIN_N_OWNED);
}

/************************************************************//**
Gets the pointer to the next record on the page.
@return pointer to next record */
UNIV_INLINE
const rec_t*
page_rec_get_next_low(
/*==================*/
	const rec_t*	rec,	/*!< in: pointer to record */
	ulint		comp)	/*!< in: nonzero=compact page layout */
{
	ulint		offs;
	const page_t*	page;

	ut_ad(page_rec_check(rec));

	page = page_align(rec);

	offs = rec_get_next_offs(rec, comp);

	if (offs >= UNIV_PAGE_SIZE) {
		fprintf(stderr,
			"InnoDB: Next record offset is nonsensical %lu"
			" in record at offset %lu\n"
			"InnoDB: rec address %p, space id %lu, page %lu\n",
			(ulong) offs, (ulong) page_offset(rec),
			(void*) rec,
			(ulong) page_get_space_id(page),
			(ulong) page_get_page_no(page));
		ut_error;
	} else if (offs == 0) {

		return(NULL);
	}

	return(page + offs);
}

/************************************************************//**
Gets the pointer to the next record on the page.
@return pointer to next record */
UNIV_INLINE
rec_t*
page_rec_get_next(
/*==============*/
	rec_t*	rec)	/*!< in: pointer to record */
{
	return((rec_t*) page_rec_get_next_low(rec, page_rec_is_comp(rec)));
}

/************************************************************//**
Gets the pointer to the next record on the page.
@return pointer to next record */
UNIV_INLINE
const rec_t*
page_rec_get_next_const(
/*====================*/
	const rec_t*	rec)	/*!< in: pointer to record */
{
	return(page_rec_get_next_low(rec, page_rec_is_comp(rec)));
}

/************************************************************//**
Gets the pointer to the next non delete-marked record on the page.
If all subsequent records are delete-marked, then this function
will return the supremum record.
@return pointer to next non delete-marked record or pointer to supremum */
UNIV_INLINE
const rec_t*
page_rec_get_next_non_del_marked(
/*=============================*/
	const rec_t*	rec)	/*!< in: pointer to record */
{
	const rec_t*	r;
	ulint		page_is_compact = page_rec_is_comp(rec);

	for (r = page_rec_get_next_const(rec);
	     !page_rec_is_supremum(r)
	     && rec_get_deleted_flag(r, page_is_compact);
	     r = page_rec_get_next_const(r)) {
		/* noop */
	}

	return(r);
}

/************************************************************//**
Sets the pointer to the next record on the page. */
UNIV_INLINE
void
page_rec_set_next(
/*==============*/
	rec_t*		rec,	/*!< in: pointer to record,
				must not be page supremum */
	const rec_t*	next)	/*!< in: pointer to next record,
				must not be page infimum */
{
	ulint	offs;

	ut_ad(page_rec_check(rec));
	ut_ad(!page_rec_is_supremum(rec));
	ut_ad(rec != next);

	ut_ad(!next || !page_rec_is_infimum(next));
	ut_ad(!next || page_align(rec) == page_align(next));

	offs = next != NULL ? page_offset(next) : 0;

	if (page_rec_is_comp(rec)) {
		rec_set_next_offs_new(rec, offs);
	} else {
		rec_set_next_offs_old(rec, offs);
	}
}

/************************************************************//**
Gets the pointer to the previous record.
@return pointer to previous record */
UNIV_INLINE
const rec_t*
page_rec_get_prev_const(
/*====================*/
	const rec_t*	rec)	/*!< in: pointer to record, must not be page
				infimum */
{
	const page_dir_slot_t*	slot;
	ulint			slot_no;
	const rec_t*		rec2;
	const rec_t*		prev_rec = NULL;
	const page_t*		page;

	ut_ad(page_rec_check(rec));

	page = page_align(rec);

	ut_ad(!page_rec_is_infimum(rec));

	slot_no = page_dir_find_owner_slot(rec);

	ut_a(slot_no != 0);

	slot = page_dir_get_nth_slot(page, slot_no - 1);

	rec2 = page_dir_slot_get_rec(slot);

	if (page_is_comp(page)) {
		while (rec != rec2) {
			prev_rec = rec2;
			rec2 = page_rec_get_next_low(rec2, TRUE);
		}
	} else {
		while (rec != rec2) {
			prev_rec = rec2;
			rec2 = page_rec_get_next_low(rec2, FALSE);
		}
	}

	ut_a(prev_rec);

	return(prev_rec);
}

/************************************************************//**
Gets the pointer to the previous record.
@return pointer to previous record */
UNIV_INLINE
rec_t*
page_rec_get_prev(
/*==============*/
	rec_t*	rec)	/*!< in: pointer to record, must not be page
			infimum */
{
	return((rec_t*) page_rec_get_prev_const(rec));
}

/***************************************************************//**
Looks for the record which owns the given record.
@return the owner record */
UNIV_INLINE
rec_t*
page_rec_find_owner_rec(
/*====================*/
	rec_t*	rec)	/*!< in: the physical record */
{
	ut_ad(page_rec_check(rec));

	if (page_rec_is_comp(rec)) {
		while (rec_get_n_owned_new(rec) == 0) {
			rec = page_rec_get_next(rec);
		}
	} else {
		while (rec_get_n_owned_old(rec) == 0) {
			rec = page_rec_get_next(rec);
		}
	}

	return(rec);
}

/**********************************************************//**
Returns the base extra size of a physical record.  This is the
size of the fixed header, independent of the record size.
@return REC_N_NEW_EXTRA_BYTES or REC_N_OLD_EXTRA_BYTES */
UNIV_INLINE
ulint
page_rec_get_base_extra_size(
/*=========================*/
	const rec_t*	rec)	/*!< in: physical record */
{
#if REC_N_NEW_EXTRA_BYTES + 1 != REC_N_OLD_EXTRA_BYTES
# error "REC_N_NEW_EXTRA_BYTES + 1 != REC_N_OLD_EXTRA_BYTES"
#endif
	return(REC_N_NEW_EXTRA_BYTES + (ulint) !page_rec_is_comp(rec));
}

/************************************************************//**
Returns the sum of the sizes of the records in the record list, excluding
the infimum and supremum records.
@return data in bytes */
UNIV_INLINE
ulint
page_get_data_size(
/*===============*/
	const page_t*	page)	/*!< in: index page */
{
	ulint	ret;

	ret = (ulint)(page_header_get_field(page, PAGE_HEAP_TOP)
		      - (page_is_comp(page)
			 ? PAGE_NEW_SUPREMUM_END
			 : PAGE_OLD_SUPREMUM_END)
		      - page_header_get_field(page, PAGE_GARBAGE));

	ut_ad(ret < UNIV_PAGE_SIZE);

	return(ret);
}


/************************************************************//**
Allocates a block of memory from the free list of an index page. */
UNIV_INLINE
void
page_mem_alloc_free(
/*================*/
	page_t*		page,	/*!< in/out: index page */
	page_zip_des_t*	page_zip,/*!< in/out: compressed page with enough
				space available for inserting the record,
				or NULL */
	rec_t*		next_rec,/*!< in: pointer to the new head of the
				free record list */
	ulint		need)	/*!< in: number of bytes allocated */
{
	ulint		garbage;

#ifdef UNIV_DEBUG
	const rec_t*	old_rec	= page_header_get_ptr(page, PAGE_FREE);
	ulint		next_offs;

	ut_ad(old_rec);
	next_offs = rec_get_next_offs(old_rec, page_is_comp(page));
	ut_ad(next_rec == (next_offs ? page + next_offs : NULL));
#endif

	page_header_set_ptr(page, page_zip, PAGE_FREE, next_rec);

	garbage = page_header_get_field(page, PAGE_GARBAGE);
	ut_ad(garbage >= need);

	page_header_set_field(page, page_zip, PAGE_GARBAGE, garbage - need);
}

/*************************************************************//**
Calculates free space if a page is emptied.
@return free space */
UNIV_INLINE
ulint
page_get_free_space_of_empty(
/*=========================*/
	ulint	comp)		/*!< in: nonzero=compact page layout */
{
	if (comp) {
		return((ulint)(UNIV_PAGE_SIZE
			       - PAGE_NEW_SUPREMUM_END
			       - PAGE_DIR
			       - 2 * PAGE_DIR_SLOT_SIZE));
	}

	return((ulint)(UNIV_PAGE_SIZE
		       - PAGE_OLD_SUPREMUM_END
		       - PAGE_DIR
		       - 2 * PAGE_DIR_SLOT_SIZE));
}

#ifndef UNIV_HOTBACKUP
/***********************************************************************//**
Write a 32-bit field in a data dictionary record. */
UNIV_INLINE
void
page_rec_write_field(
/*=================*/
	rec_t*	rec,	/*!< in/out: record to update */
	ulint	i,	/*!< in: index of the field to update */
	ulint	val,	/*!< in: value to write */
	mtr_t*	mtr)	/*!< in/out: mini-transaction */
{
	byte*	data;
	ulint	len;

	data = rec_get_nth_field_old(rec, i, &len);

	ut_ad(len == 4);

	mlog_write_ulint(data, val, MLOG_4BYTES, mtr);
}
#endif /* !UNIV_HOTBACKUP */

/************************************************************//**
Each user record on a page, and also the deleted user records in the heap
takes its size plus the fraction of the dir cell size /
PAGE_DIR_SLOT_MIN_N_OWNED bytes for it. If the sum of these exceeds the
value of page_get_free_space_of_empty, the insert is impossible, otherwise
it is allowed. This function returns the maximum combined size of records
which can be inserted on top of the record heap.
@return maximum combined size for inserted records */
UNIV_INLINE
ulint
page_get_max_insert_size(
/*=====================*/
	const page_t*	page,	/*!< in: index page */
	ulint		n_recs)	/*!< in: number of records */
{
	ulint	occupied;
	ulint	free_space;

	if (page_is_comp(page)) {
		occupied = page_header_get_field(page, PAGE_HEAP_TOP)
			- PAGE_NEW_SUPREMUM_END
			+ page_dir_calc_reserved_space(
				n_recs + page_dir_get_n_heap(page) - 2);

		free_space = page_get_free_space_of_empty(TRUE);
	} else {
		occupied = page_header_get_field(page, PAGE_HEAP_TOP)
			- PAGE_OLD_SUPREMUM_END
			+ page_dir_calc_reserved_space(
				n_recs + page_dir_get_n_heap(page) - 2);

		free_space = page_get_free_space_of_empty(FALSE);
	}

	/* Above the 'n_recs +' part reserves directory space for the new
	inserted records; the '- 2' excludes page infimum and supremum
	records */

	if (occupied > free_space) {

		return(0);
	}

	return(free_space - occupied);
}

/************************************************************//**
Returns the maximum combined size of records which can be inserted on top
of the record heap if a page is first reorganized.
@return maximum combined size for inserted records */
UNIV_INLINE
ulint
page_get_max_insert_size_after_reorganize(
/*======================================*/
	const page_t*	page,	/*!< in: index page */
	ulint		n_recs)	/*!< in: number of records */
{
	ulint	occupied;
	ulint	free_space;

	occupied = page_get_data_size(page)
		+ page_dir_calc_reserved_space(n_recs + page_get_n_recs(page));

	free_space = page_get_free_space_of_empty(page_is_comp(page));

	if (occupied > free_space) {

		return(0);
	}

	return(free_space - occupied);
}

/************************************************************//**
Puts a record to free list. */
UNIV_INLINE
void
page_mem_free(
/*==========*/
	page_t*			page,		/*!< in/out: index page */
	page_zip_des_t*		page_zip,	/*!< in/out: compressed page,
						or NULL */
	rec_t*			rec,		/*!< in: pointer to the
						(origin of) record */
	const dict_index_t*	index,		/*!< in: index of rec */
	const ulint*		offsets)	/*!< in: array returned by
						rec_get_offsets() */
{
	rec_t*		free;
	ulint		garbage;

	ut_ad(rec_offs_validate(rec, index, offsets));
	free = page_header_get_ptr(page, PAGE_FREE);

	page_rec_set_next(rec, free);
	page_header_set_ptr(page, page_zip, PAGE_FREE, rec);

	garbage = page_header_get_field(page, PAGE_GARBAGE);

	page_header_set_field(page, page_zip, PAGE_GARBAGE,
			      garbage + rec_offs_size(offsets));

	if (page_zip) {
		page_zip_dir_delete(page_zip, rec, index, offsets, free);
	} else {
		page_header_set_field(page, page_zip, PAGE_N_RECS,
				      page_get_n_recs(page) - 1);
	}
}

#endif /* !UNIV_INNOCHECKSUM */
#ifdef UNIV_MATERIALIZE
#undef UNIV_INLINE
#define UNIV_INLINE	UNIV_INLINE_ORIGINAL
#endif