path: root/innobase/include/rem0rec.ic

/************************************************************************
Record manager

(c) 1994-1996 Innobase Oy

Created 5/30/1994 Heikki Tuuri
*************************************************************************/

#include "mach0data.h"
#include "ut0byte.h"
#include "dict0dict.h"

/* Compact flag ORed to the extra size returned by rec_get_offsets() */
#define REC_OFFS_COMPACT	((ulint) 1 << 31)
/* SQL NULL flag in offsets returned by rec_get_offsets() */
#define REC_OFFS_SQL_NULL	((ulint) 1 << 31)
/* External flag in offsets returned by rec_get_offsets() */
#define REC_OFFS_EXTERNAL	((ulint) 1 << 30)
/* Mask for offsets returned by rec_get_offsets() */
#define REC_OFFS_MASK		(REC_OFFS_EXTERNAL - 1)

/* Offsets of the bit-fields in an old-style record. NOTE! In the table the
most significant bytes and bits are written below less significant.

	(1) byte offset		(2) bit usage within byte
	downward from
	origin ->	1	8 bits pointer to next record
			2	8 bits pointer to next record
			3  	1 bit short flag
				7 bits number of fields
			4	3 bits number of fields
				5 bits heap number
			5	8 bits heap number
			6	4 bits n_owned
				4 bits info bits
*/

/* Offsets of the bit-fields in a new-style record. NOTE! In the table the
most significant bytes and bits are written below less significant.

	(1) byte offset		(2) bit usage within byte
	downward from
	origin ->	1	8 bits relative offset of next record
			2	8 bits relative offset of next record
				  the relative offset is an unsigned 16-bit
				  integer:
				  (offset_of_next_record
				   - offset_of_this_record) mod 64Ki,
				  where mod is the modulo as a non-negative
				  number;
				  we can calculate the the offset of the next
				  record with the formula:
				  relative_offset + offset_of_this_record
				  mod UNIV_PAGE_SIZE
			3	3 bits status:
					000=conventional record
					001=node pointer record (inside B-tree)
					010=infimum record
					011=supremum record
					1xx=reserved
				5 bits heap number
			4	8 bits heap number
			5	4 bits n_owned
				4 bits info bits
*/

/* We list the byte offsets from the origin of the record, the mask,
and the shift needed to obtain each bit-field of the record. */

#define REC_NEXT		2
#define REC_NEXT_MASK		0xFFFFUL
#define REC_NEXT_SHIFT		0

#define REC_OLD_SHORT		3	/* This is single byte bit-field */
#define REC_OLD_SHORT_MASK	0x1UL
#define REC_OLD_SHORT_SHIFT	0

#define REC_OLD_N_FIELDS	4
#define REC_OLD_N_FIELDS_MASK	0x7FEUL
#define REC_OLD_N_FIELDS_SHIFT	1

#define REC_NEW_STATUS		3	/* This is single byte bit-field */
#define REC_NEW_STATUS_MASK	0x7UL
#define REC_NEW_STATUS_SHIFT	0

#define REC_OLD_HEAP_NO		5
#define REC_NEW_HEAP_NO		4
#define REC_HEAP_NO_MASK	0xFFF8UL
#define	REC_HEAP_NO_SHIFT	3

#define REC_OLD_N_OWNED		6	/* This is single byte bit-field */
#define REC_NEW_N_OWNED		5	/* This is single byte bit-field */
#define	REC_N_OWNED_MASK	0xFUL
#define REC_N_OWNED_SHIFT	0

#define REC_OLD_INFO_BITS	6	/* This is single byte bit-field */
#define REC_NEW_INFO_BITS	5	/* This is single byte bit-field */
#define	REC_INFO_BITS_MASK	0xF0UL
#define REC_INFO_BITS_SHIFT	0

/* The deleted flag in info bits */
#define REC_INFO_DELETED_FLAG 	0x20UL	/* when bit is set to 1, it means the
					record has been delete marked */
/* The following masks are used to filter the SQL null bit from
one-byte and two-byte offsets */

#define REC_1BYTE_SQL_NULL_MASK	0x80UL
#define REC_2BYTE_SQL_NULL_MASK	0x8000UL

/* In a 2-byte offset the second most significant bit denotes
a field stored to another page: */

#define REC_2BYTE_EXTERN_MASK	0x4000UL

#if REC_OLD_SHORT_MASK << (8 * (REC_OLD_SHORT - 3)) \
		^ REC_OLD_N_FIELDS_MASK << (8 * (REC_OLD_N_FIELDS - 4)) \
		^ REC_HEAP_NO_MASK << (8 * (REC_OLD_HEAP_NO - 4)) \
		^ REC_N_OWNED_MASK << (8 * (REC_OLD_N_OWNED - 3)) \
		^ REC_INFO_BITS_MASK << (8 * (REC_OLD_INFO_BITS - 3)) \
		^ 0xFFFFFFFFUL
# error "sum of old-style masks != 0xFFFFFFFFUL"
#endif
#if REC_NEW_STATUS_MASK << (8 * (REC_NEW_STATUS - 3)) \
		^ REC_HEAP_NO_MASK << (8 * (REC_NEW_HEAP_NO - 4)) \
		^ REC_N_OWNED_MASK << (8 * (REC_NEW_N_OWNED - 3)) \
		^ REC_INFO_BITS_MASK << (8 * (REC_NEW_INFO_BITS - 3)) \
		^ 0xFFFFFFUL
# error "sum of new-style masks != 0xFFFFFFUL"
#endif

/***************************************************************
Sets the value of the ith field SQL null bit of an old-style record. */

void
rec_set_nth_field_null_bit(
/*=======================*/
	rec_t*	rec,	/* in: record */
	ulint	i,	/* in: ith field */
	ibool	val);	/* in: value to set */
/*************************************************************** 
Sets an old-style record field to SQL null.
The physical size of the field is not changed. */

void
rec_set_nth_field_sql_null(
/*=======================*/
	rec_t*	rec, 	/* in: record */
	ulint	n);	/* in: index of the field */

/***************************************************************
Sets the value of the ith field extern storage bit of an old-style record. */

void
rec_set_nth_field_extern_bit_old(
/*=============================*/
	rec_t*	rec,	/* in: old-style record */
	ulint	i,	/* in: ith field */
	ibool	val,	/* in: value to set */
	mtr_t*	mtr);	/* in: mtr holding an X-latch to the page where
			rec is, or NULL; in the NULL case we do not
			write to log about the change */
/***************************************************************
Sets the value of the ith field extern storage bit of a new-style record. */

void
rec_set_nth_field_extern_bit_new(
/*=============================*/
	rec_t*		rec,	/* in: record */
	dict_index_t*	index,	/* in: record descriptor */
	ulint		ith,	/* in: ith field */
	ibool		val,	/* in: value to set */
	mtr_t*		mtr);	/* in: mtr holding an X-latch to the page
				where rec is, or NULL; in the NULL case
				we do not write to log about the change */

/**********************************************************
Gets a bit field from within 1 byte. */
UNIV_INLINE
ulint
rec_get_bit_field_1(
/*================*/
	rec_t*	rec,	/* in: pointer to record origin */
	ulint	offs,	/* in: offset from the origin down */
	ulint	mask,	/* in: mask used to filter bits */
	ulint	shift)	/* in: shift right applied after masking */
{
	ut_ad(rec);

	return((mach_read_from_1(rec - offs) & mask) >> shift);
}

/**********************************************************
Sets a bit field within 1 byte. */
UNIV_INLINE
void
rec_set_bit_field_1(
/*================*/
	rec_t*	rec,	/* in: pointer to record origin */
	ulint	val,	/* in: value to set */
	ulint	offs,	/* in: offset from the origin down */
	ulint	mask,	/* in: mask used to filter bits */
	ulint	shift)	/* in: shift right applied after masking */
{
	ut_ad(rec);
	ut_ad(offs <= REC_N_OLD_EXTRA_BYTES);
	ut_ad(mask);
	ut_ad(mask <= 0xFFUL);
	ut_ad(((mask >> shift) << shift) == mask);
	ut_ad(((val << shift) & mask) == (val << shift));
	
	mach_write_to_1(rec - offs, 
			(mach_read_from_1(rec - offs) & ~mask) 
			| (val << shift));
}

/**********************************************************
Gets a bit field from within 2 bytes. */
UNIV_INLINE
ulint
rec_get_bit_field_2(
/*================*/
	rec_t*	rec,	/* in: pointer to record origin */
	ulint	offs,	/* in: offset from the origin down */
	ulint	mask,	/* in: mask used to filter bits */
	ulint	shift)	/* in: shift right applied after masking */
{
	ut_ad(rec);

	return((mach_read_from_2(rec - offs) & mask) >> shift);
}

/**********************************************************
Sets a bit field within 2 bytes. */
UNIV_INLINE
void
rec_set_bit_field_2(
/*================*/
	rec_t*	rec,	/* in: pointer to record origin */
	ulint	val,	/* in: value to set */
	ulint	offs,	/* in: offset from the origin down */
	ulint	mask,	/* in: mask used to filter bits */
	ulint	shift)	/* in: shift right applied after masking */
{
	ut_ad(rec);
	ut_ad(offs <= REC_N_OLD_EXTRA_BYTES);
	ut_ad(mask > 0xFFUL);
	ut_ad(mask <= 0xFFFFUL);
	ut_ad((mask >> shift) & 1);
	ut_ad(0 == ((mask >> shift) & ((mask >> shift) + 1)));
	ut_ad(((mask >> shift) << shift) == mask);
	ut_ad(((val << shift) & mask) == (val << shift));

	mach_write_to_2(rec - offs, 
			(mach_read_from_2(rec - offs) & ~mask) 
			| (val << shift));
}

/**********************************************************
The following function is used to get the offset of the next chained record
on the same page. */
UNIV_INLINE
ulint 
rec_get_next_offs(
/*==============*/
			/* out: the page offset of the next chained record, or
			0 if none */
	rec_t*	rec,	/* in: physical record */
	ulint	comp)	/* in: nonzero=compact page format */
{	
	ulint	field_value;
		
	ut_ad(REC_NEXT_MASK == 0xFFFFUL);
	ut_ad(REC_NEXT_SHIFT == 0);

	field_value = mach_read_from_2(rec - REC_NEXT);

	if (comp) {
#if UNIV_PAGE_SIZE <= 32768
		/* Note that for 64 KiB pages, field_value can 'wrap around'
		and the debug assertion is not valid */

		/* In the following assertion, field_value is interpreted
		as signed 16-bit integer in 2's complement arithmetics.
		If all platforms defined int16_t in the standard headers,
		the expression could be written simpler as
		(int16_t) field_value + ut_align_offset(...) < UNIV_PAGE_SIZE
		*/
		ut_ad((field_value >= 32768
			? field_value - 65536
			: field_value)
		       + ut_align_offset(rec, UNIV_PAGE_SIZE)
		      < UNIV_PAGE_SIZE);
#endif
		if (field_value == 0) {

			return(0);
		}
		
		return(ut_align_offset(rec + field_value, UNIV_PAGE_SIZE));
	} else {
		ut_ad(field_value < UNIV_PAGE_SIZE);

		return(field_value);
	}
}

/**********************************************************
The following function is used to set the next record offset field of the
record. */
UNIV_INLINE
void
rec_set_next_offs(
/*==============*/
	rec_t*	rec,	/* in: physical record */
	ulint	comp,	/* in: nonzero=compact page format */
	ulint	next)	/* in: offset of the next record, or 0 if none */
{
	ut_ad(rec);
	ut_ad(UNIV_PAGE_SIZE > next);
	ut_ad(REC_NEXT_MASK == 0xFFFFUL);
	ut_ad(REC_NEXT_SHIFT == 0);

	if (comp) {
		ulint field_value;

		if (next) {
			/* The following two statements calculate
			next - offset_of_rec mod 64Ki, where mod is the modulo
			as a non-negative number */
		
			field_value = (ulint)((lint)next 
				- (lint)ut_align_offset(rec, UNIV_PAGE_SIZE));
			field_value &= REC_NEXT_MASK;
		} else {
			field_value = 0;
		}

		mach_write_to_2(rec - REC_NEXT, field_value);
	} else {
		mach_write_to_2(rec - REC_NEXT, next);
	}
}

/**********************************************************
The following function is used to get the number of fields
in an old-style record. */
UNIV_INLINE
ulint
rec_get_n_fields_old(
/*=================*/
			/* out: number of data fields */
	rec_t*	rec)	/* in: physical record */
{
	ulint	ret;

	ut_ad(rec);

	ret = rec_get_bit_field_2(rec, REC_OLD_N_FIELDS,
				REC_OLD_N_FIELDS_MASK, REC_OLD_N_FIELDS_SHIFT);
	ut_ad(ret <= REC_MAX_N_FIELDS);
	ut_ad(ret > 0);

	return(ret);
}	

/**********************************************************
The following function is used to set the number of fields
in an old-style record. */
UNIV_INLINE
void
rec_set_n_fields_old(
/*=================*/
	rec_t*	rec,		/* in: physical record */
	ulint	n_fields)	/* in: the number of fields */
{
	ut_ad(rec);
	ut_ad(n_fields <= REC_MAX_N_FIELDS);
	ut_ad(n_fields > 0);

	rec_set_bit_field_2(rec, n_fields, REC_OLD_N_FIELDS,
		REC_OLD_N_FIELDS_MASK, REC_OLD_N_FIELDS_SHIFT);
}

/**********************************************************
The following function retrieves the status bits of a new-style record. */
UNIV_INLINE
ulint
rec_get_status(
/*===========*/
			/* out: status bits */
	rec_t*	rec)	/* in: physical record */
{
	ulint	ret;

	ut_ad(rec);

	ret = rec_get_bit_field_1(rec, REC_NEW_STATUS,
				REC_NEW_STATUS_MASK, REC_NEW_STATUS_SHIFT);
	ut_ad((ret & ~REC_NEW_STATUS_MASK) == 0);

	return(ret);
}

/**********************************************************
The following function is used to get the number of fields
in a record. */
UNIV_INLINE
ulint
rec_get_n_fields(
/*=============*/
				/* out: number of data fields */
	rec_t*		rec,	/* in: physical record */
	dict_index_t*	index)	/* in: record descriptor */
{
	ut_ad(rec);
	ut_ad(index);
	if (UNIV_UNLIKELY(!index->table->comp)) {
		return(rec_get_n_fields_old(rec));
	}
	switch (rec_get_status(rec)) {
	case REC_STATUS_ORDINARY:
		return(dict_index_get_n_fields(index));
	case REC_STATUS_NODE_PTR:
		return(dict_index_get_n_unique_in_tree(index) + 1);
	case REC_STATUS_INFIMUM:
	case REC_STATUS_SUPREMUM:
		return(1);
	default:
		ut_error;
		return(ULINT_UNDEFINED);
	}
}

/**********************************************************
The following function is used to get the number of records owned by the
previous directory record. */
UNIV_INLINE
ulint
rec_get_n_owned(
/*============*/
			/* out: number of owned records */
	rec_t*	rec,	/* in: physical record */
	ulint	comp)	/* in: nonzero=compact page format */
{
	ulint	ret;

	ut_ad(rec);

	ret = rec_get_bit_field_1(rec,
				comp ? REC_NEW_N_OWNED : REC_OLD_N_OWNED,
				REC_N_OWNED_MASK, REC_N_OWNED_SHIFT);
	ut_ad(ret <= REC_MAX_N_OWNED); 

	return(ret);
}	

/**********************************************************
The following function is used to set the number of owned records. */
UNIV_INLINE
void
rec_set_n_owned(
/*============*/
	rec_t*	rec,		/* in: physical record */
	ulint	comp,		/* in: nonzero=compact page format */
	ulint	n_owned)	/* in: the number of owned */
{
	ut_ad(rec);
	ut_ad(n_owned <= REC_MAX_N_OWNED);

	rec_set_bit_field_1(rec, n_owned,
				comp ? REC_NEW_N_OWNED : REC_OLD_N_OWNED,
				REC_N_OWNED_MASK, REC_N_OWNED_SHIFT);
}

/**********************************************************
The following function is used to retrieve the info bits of a record. */
UNIV_INLINE
ulint
rec_get_info_bits(
/*==============*/
			/* out: info bits */
	rec_t*	rec,	/* in: physical record */
	ulint	comp)	/* in: nonzero=compact page format */
{
	ulint	ret;

	ut_ad(rec);

	ret = rec_get_bit_field_1(rec,
				comp ? REC_NEW_INFO_BITS : REC_OLD_INFO_BITS,
				REC_INFO_BITS_MASK, REC_INFO_BITS_SHIFT);
	ut_ad((ret & ~REC_INFO_BITS_MASK) == 0);

	return(ret);
}	

/**********************************************************
The following function is used to set the info bits of a record. */
UNIV_INLINE
void
rec_set_info_bits(
/*==============*/
	rec_t*	rec,	/* in: physical record */
	ulint	comp,	/* in: nonzero=compact page format */
	ulint	bits)	/* in: info bits */
{
	ut_ad(rec);
	ut_ad((bits & ~REC_INFO_BITS_MASK) == 0);

	rec_set_bit_field_1(rec, bits,
				comp ? REC_NEW_INFO_BITS : REC_OLD_INFO_BITS,
				REC_INFO_BITS_MASK, REC_INFO_BITS_SHIFT);
}

/**********************************************************
The following function is used to set the status bits of a new-style record. */
UNIV_INLINE
void
rec_set_status(
/*===========*/
	rec_t*	rec,	/* in: physical record */
	ulint	bits)	/* in: info bits */
{
	ut_ad(rec);
	ut_ad((bits & ~REC_NEW_STATUS_MASK) == 0);

	rec_set_bit_field_1(rec, bits, REC_NEW_STATUS,
				REC_NEW_STATUS_MASK, REC_NEW_STATUS_SHIFT);
}

/**********************************************************
The following function is used to retrieve the info and status
bits of a record.  (Only compact records have status bits.) */
UNIV_INLINE
ulint
rec_get_info_and_status_bits(
/*=========================*/
			/* out: info bits */
	rec_t*	rec,	/* in: physical record */
	ulint	comp)	/* in: nonzero=compact page format */
{
	ulint	bits;
#if (REC_NEW_STATUS_MASK >> REC_NEW_STATUS_SHIFT) \
& (REC_INFO_BITS_MASK >> REC_INFO_BITS_SHIFT)
# error "REC_NEW_STATUS_MASK and REC_INFO_BITS_MASK overlap"
#endif
	if (UNIV_EXPECT(comp, REC_OFFS_COMPACT)) {
		bits = rec_get_info_bits(rec, TRUE) | rec_get_status(rec);
	} else {
		bits = rec_get_info_bits(rec, FALSE);
		ut_ad(!(bits & ~(REC_INFO_BITS_MASK >> REC_INFO_BITS_SHIFT)));
	}
	return(bits);
}
/**********************************************************
The following function is used to set the info and status
bits of a record.  (Only compact records have status bits.) */
UNIV_INLINE
void
rec_set_info_and_status_bits(
/*=========================*/
	rec_t*	rec,	/* in: physical record */
	ulint	comp,	/* in: nonzero=compact page format */
	ulint	bits)	/* in: info bits */
{
#if (REC_NEW_STATUS_MASK >> REC_NEW_STATUS_SHIFT) \
& (REC_INFO_BITS_MASK >> REC_INFO_BITS_SHIFT)
# error "REC_NEW_STATUS_MASK and REC_INFO_BITS_MASK overlap"
#endif
	if (comp) {
		rec_set_status(rec, bits & REC_NEW_STATUS_MASK);
	} else {
		ut_ad(!(bits & ~(REC_INFO_BITS_MASK >> REC_INFO_BITS_SHIFT)));
	}
	rec_set_info_bits(rec, comp, bits & ~REC_NEW_STATUS_MASK);
}

/**********************************************************
The following function tells if record is delete marked. */
UNIV_INLINE
ulint
rec_get_deleted_flag(
/*=================*/
			/* out: nonzero if delete marked */
	rec_t*	rec,	/* in: physical record */
	ulint	comp)	/* in: nonzero=compact page format */
{
	if (UNIV_EXPECT(comp, REC_OFFS_COMPACT)) {
		return(UNIV_UNLIKELY(rec_get_bit_field_1(rec,
				REC_NEW_INFO_BITS, REC_INFO_DELETED_FLAG,
				REC_INFO_BITS_SHIFT)));
	} else {
		return(UNIV_UNLIKELY(rec_get_bit_field_1(rec,
				REC_OLD_INFO_BITS, REC_INFO_DELETED_FLAG,
				REC_INFO_BITS_SHIFT)));
	}
}

/**********************************************************
The following function is used to set the deleted bit. */
UNIV_INLINE
void
rec_set_deleted_flag(
/*=================*/
	rec_t*	rec,	/* in: physical record */
	ulint	comp,	/* in: nonzero=compact page format */
	ulint	flag)	/* in: nonzero if delete marked */
{
	ulint	val;

	val = rec_get_info_bits(rec, comp);
	
	if (flag) {
		val |= REC_INFO_DELETED_FLAG;
	} else {
		val &= ~REC_INFO_DELETED_FLAG;
	}

	rec_set_info_bits(rec, comp, val);
}

/**********************************************************
The following function tells if a new-style record is a node pointer. */
UNIV_INLINE
ibool
rec_get_node_ptr_flag(
/*=================*/
			/* out: TRUE if node pointer */
	rec_t*	rec)	/* in: physical record */
{
	return(REC_STATUS_NODE_PTR == rec_get_status(rec));
}

/**********************************************************
The following function is used to get the order number of the record in the
heap of the index page. */
UNIV_INLINE
ulint
rec_get_heap_no(
/*=============*/
			/* out: heap order number */
	rec_t*	rec,	/* in: physical record */
	ulint	comp)	/* in: nonzero=compact page format */
{
	ulint	ret;

	ut_ad(rec);

	ret = rec_get_bit_field_2(rec,
				comp ? REC_NEW_HEAP_NO : REC_OLD_HEAP_NO,
				REC_HEAP_NO_MASK, REC_HEAP_NO_SHIFT);
	ut_ad(ret <= REC_MAX_HEAP_NO);

	return(ret);
}	

/**********************************************************
The following function is used to set the heap number field in the record. */
UNIV_INLINE
void
rec_set_heap_no(
/*=============*/
	rec_t*	rec,	/* in: physical record */
	ulint	comp,	/* in: nonzero=compact page format */
	ulint	heap_no)/* in: the heap number */
{
	ut_ad(heap_no <= REC_MAX_HEAP_NO);

	rec_set_bit_field_2(rec, heap_no,
				comp ? REC_NEW_HEAP_NO : REC_OLD_HEAP_NO,
				REC_HEAP_NO_MASK, REC_HEAP_NO_SHIFT);
}

/**********************************************************
The following function is used to test whether the data offsets in the record
are stored in one-byte or two-byte format. */
UNIV_INLINE
ibool
rec_get_1byte_offs_flag(
/*====================*/
			/* out: TRUE if 1-byte form */
	rec_t*	rec)	/* in: physical record */
{
#if TRUE != 1
#error "TRUE != 1"
#endif

	return(rec_get_bit_field_1(rec, REC_OLD_SHORT, REC_OLD_SHORT_MASK,
							REC_OLD_SHORT_SHIFT));
}

/**********************************************************
The following function is used to set the 1-byte offsets flag. */
UNIV_INLINE
void
rec_set_1byte_offs_flag(
/*====================*/
	rec_t*	rec,	/* in: physical record */
	ibool	flag)	/* in: TRUE if 1byte form */
{
#if TRUE != 1
#error "TRUE != 1"
#endif
	ut_ad(flag <= TRUE);

	rec_set_bit_field_1(rec, flag, REC_OLD_SHORT, REC_OLD_SHORT_MASK,
							REC_OLD_SHORT_SHIFT);
}

/**********************************************************
Returns the offset of nth field end if the record is stored in the 1-byte
offsets form. If the field is SQL null, the flag is ORed in the returned
value. */
UNIV_INLINE
ulint
rec_1_get_field_end_info(
/*=====================*/
 			/* out: offset of the start of the field, SQL null
 			flag ORed */
 	rec_t*	rec, 	/* in: record */
 	ulint	n)	/* in: field index */
{
	ut_ad(rec_get_1byte_offs_flag(rec));
	ut_ad(n < rec_get_n_fields_old(rec));

	return(mach_read_from_1(rec - (REC_N_OLD_EXTRA_BYTES + n + 1)));
}
						
/**********************************************************
Returns the offset of nth field end if the record is stored in the 2-byte
offsets form. If the field is SQL null, the flag is ORed in the returned
value. */
UNIV_INLINE
ulint
rec_2_get_field_end_info(
/*=====================*/
 			/* out: offset of the start of the field, SQL null
 			flag and extern storage flag ORed */
 	rec_t*	rec, 	/* in: record */
 	ulint	n)	/* in: field index */
{
	ut_ad(!rec_get_1byte_offs_flag(rec));
	ut_ad(n < rec_get_n_fields_old(rec));

	return(mach_read_from_2(rec - (REC_N_OLD_EXTRA_BYTES + 2 * n + 2)));
}

#ifdef UNIV_DEBUG
/* Length of the rec_get_offsets() header */
# define REC_OFFS_HEADER_SIZE	4
#else /* UNIV_DEBUG */
/* Length of the rec_get_offsets() header */
# define REC_OFFS_HEADER_SIZE	2
#endif /* UNIV_DEBUG */

/* Get the base address of offsets.  The extra_size is stored at
this position, and following positions hold the end offsets of
the fields. */
#define rec_offs_base(offsets) (offsets + REC_OFFS_HEADER_SIZE)

/************************************************************** 
The following function returns the number of allocated elements
for an array of offsets. */
UNIV_INLINE
ulint
rec_offs_get_n_alloc(
/*=================*/
				/* out: number of elements */
	const ulint*	offsets)/* in: array for rec_get_offsets() */
{
	ulint	n_alloc;
	ut_ad(offsets);
	n_alloc = offsets[0];
	ut_ad(n_alloc > 0);
	return(n_alloc);
}

/************************************************************** 
The following function sets the number of allocated elements
for an array of offsets. */
UNIV_INLINE
void
rec_offs_set_n_alloc(
/*=================*/
	ulint*	offsets,	/* in: array for rec_get_offsets() */
	ulint	n_alloc)	/* in: number of elements */
{
	ut_ad(offsets);
	ut_ad(n_alloc > 0);
	offsets[0] = n_alloc;
}

/************************************************************** 
The following function returns the number of fields in a record. */
UNIV_INLINE
ulint
rec_offs_n_fields(
/*===============*/
				/* out: number of fields */
	const ulint*	offsets)/* in: array returned by rec_get_offsets() */
{
	ulint	n_fields;
	ut_ad(offsets);
	n_fields = offsets[1];
	ut_ad(n_fields > 0);
	ut_ad(n_fields <= REC_MAX_N_FIELDS);
	ut_ad(n_fields + REC_OFFS_HEADER_SIZE
		<= rec_offs_get_n_alloc(offsets));
	return(n_fields);
}

/****************************************************************
Validates offsets returned by rec_get_offsets(). */
UNIV_INLINE
ibool
rec_offs_validate(
/*==============*/
				/* out: TRUE if valid */
	rec_t*		rec,	/* in: record or NULL */
	dict_index_t*	index,	/* in: record descriptor or NULL */
	const ulint*	offsets)/* in: array returned by rec_get_offsets() */
{
	ulint	i	= rec_offs_n_fields(offsets);
	ulint	last	= ULINT_MAX;
	ulint	comp	= *rec_offs_base(offsets) & REC_OFFS_COMPACT;

	if (rec) {
		ut_ad((ulint) rec == offsets[2]);
		if (!comp) {
			ut_a(rec_get_n_fields_old(rec) >= i);
		}
	}
	if (index) {
		ulint max_n_fields;
		ut_ad((ulint) index == offsets[3]);
		max_n_fields = ut_max(
				dict_index_get_n_fields(index),
				dict_index_get_n_unique_in_tree(index) + 1);
		if (comp && rec) {
			switch (rec_get_status(rec)) {
			case REC_STATUS_ORDINARY:
				break;
			case REC_STATUS_NODE_PTR:
				max_n_fields =
				dict_index_get_n_unique_in_tree(index) + 1;
				break;
			case REC_STATUS_INFIMUM:
			case REC_STATUS_SUPREMUM:
				max_n_fields = 1;
				break;
			default:
				ut_error;
			}
		}
		/* index->n_def == 0 for dummy indexes if !comp */
		ut_a(!comp || index->n_def);
		ut_a(!index->n_def || i <= max_n_fields);
	}
	while (i--) {
		ulint	curr = rec_offs_base(offsets)[1 + i] & REC_OFFS_MASK;
		ut_a(curr <= last);
		last = curr;
	}
	return(TRUE);
}
/****************************************************************
Updates debug data in offsets, in order to avoid bogus
rec_offs_validate() failures. */
UNIV_INLINE
void
rec_offs_make_valid(
/*================*/
	rec_t*		rec __attribute__((unused)),
				/* in: record */
	dict_index_t*	index __attribute__((unused)),
				/* in: record descriptor */
	ulint*		offsets __attribute__((unused)))
				/* in: array returned by rec_get_offsets() */
{
#ifdef UNIV_DEBUG
	ut_ad(rec_get_n_fields(rec, index) >= rec_offs_n_fields(offsets));
	offsets[2] = (ulint) rec;
	offsets[3] = (ulint) index;
#endif /* UNIV_DEBUG */
}

/****************************************************************
The following function is used to get a pointer to the nth
data field in a record. */
UNIV_INLINE
byte*
rec_get_nth_field(
/*==============*/
	 			/* out: pointer to the field */
	rec_t*		rec, 	/* in: record */
	const ulint*	offsets,/* in: array returned by rec_get_offsets() */
	ulint		n,	/* in: index of the field */
	ulint*		len)	/* out: length of the field; UNIV_SQL_NULL
				if SQL null */
{
	byte*	field;
	ulint	length;
	ut_ad(rec);
	ut_ad(rec_offs_validate(rec, NULL, offsets));
	ut_ad(n < rec_offs_n_fields(offsets));
	ut_ad(len);

	if (UNIV_UNLIKELY(n == 0)) {
		field = rec;
	} else {
		field = rec + (rec_offs_base(offsets)[n] & REC_OFFS_MASK);
	}

	length = rec_offs_base(offsets)[1 + n];

	if (length & REC_OFFS_SQL_NULL) {
		length = UNIV_SQL_NULL;
	} else {
		length &= REC_OFFS_MASK;
		length -= field - rec;
	}

	*len = length;
	return(field);
}

/**********************************************************
Determine if the offsets are for a record in the new
compact format. */
UNIV_INLINE
ulint
rec_offs_comp(
/*==========*/
				/* out: nonzero if compact format */
	const ulint*	offsets)/* in: array returned by rec_get_offsets() */
{
	ut_ad(rec_offs_validate(NULL, NULL, offsets));
	return(*rec_offs_base(offsets) & REC_OFFS_COMPACT);
}

/**********************************************************
Returns nonzero if the extern bit is set in nth field of rec. */
UNIV_INLINE
ulint
rec_offs_nth_extern(
/*================*/
				/* out: nonzero if externally stored */
	const ulint*	offsets,/* in: array returned by rec_get_offsets() */
	ulint		n)	/* in: nth field */
{
	ut_ad(rec_offs_validate(NULL, NULL, offsets));
	ut_ad(n < rec_offs_n_fields(offsets));
	return(UNIV_UNLIKELY(rec_offs_base(offsets)[1 + n]
				& REC_OFFS_EXTERNAL));
}

/**********************************************************
Gets the physical size of a field. */
UNIV_INLINE
ulint
rec_offs_nth_size(
/*==============*/
				/* out: length of field */
	const ulint*	offsets,/* in: array returned by rec_get_offsets() */
	ulint		n)	/* in: nth field */
{
	ut_ad(rec_offs_validate(NULL, NULL, offsets));
	ut_ad(n < rec_offs_n_fields(offsets));
	return((rec_offs_base(offsets)[1 + n] - rec_offs_base(offsets)[n])
			& REC_OFFS_MASK);
}

/**********************************************************
Returns TRUE if the extern bit is set in any of the fields
of an old-style record. */
UNIV_INLINE
ibool
rec_offs_any_extern(
/*================*/
				/* out: TRUE if a field is stored externally */
	const ulint*	offsets)/* in: array returned by rec_get_offsets() */
{
	ulint	i;
	for (i = rec_offs_n_fields(offsets); i--; ) {
		if (rec_offs_nth_extern(offsets, i)) {
			return(TRUE);
		}
	}
	return(FALSE);
}

/***************************************************************
Sets the value of the ith field extern storage bit. */
UNIV_INLINE
void
rec_set_nth_field_extern_bit(
/*=========================*/
	rec_t*		rec,	/* in: record */
	dict_index_t*	index,	/* in: record descriptor */
	ulint		i,	/* in: ith field */
	ibool		val,	/* in: value to set */
	mtr_t*		mtr)	/* in: mtr holding an X-latch to the page
				where rec is, or NULL; in the NULL case
				we do not write to log about the change */
{
	if (UNIV_LIKELY(index->table->comp)) {
		rec_set_nth_field_extern_bit_new(rec, index, i, val, mtr);
	} else {
		rec_set_nth_field_extern_bit_old(rec, i, val, mtr);
	}
}

/**********************************************************
Returns the offset of n - 1th field end if the record is stored in the 1-byte
offsets form. If the field is SQL null, the flag is ORed in the returned
value. This function and the 2-byte counterpart are defined here because the
C-compiler was not able to sum negative and positive constant offsets, and
warned of constant arithmetic overflow within the compiler. */
UNIV_INLINE
ulint
rec_1_get_prev_field_end_info(
/*==========================*/
 			/* out: offset of the start of the PREVIOUS field, SQL
			null flag ORed */
 	rec_t*	rec, 	/* in: record */
 	ulint	n)	/* in: field index */
{
	ut_ad(rec_get_1byte_offs_flag(rec));
	ut_ad(n <= rec_get_n_fields_old(rec));

	return(mach_read_from_1(rec - (REC_N_OLD_EXTRA_BYTES + n)));
}
						
/**********************************************************
Returns the offset of n - 1th field end if the record is stored in the 2-byte
offsets form. If the field is SQL null, the flag is ORed in the returned
value. */
UNIV_INLINE
ulint
rec_2_get_prev_field_end_info(
/*==========================*/
 			/* out: offset of the start of the PREVIOUS field, SQL
			null flag ORed */
 	rec_t*	rec, 	/* in: record */
 	ulint	n)	/* in: field index */
{
	ut_ad(!rec_get_1byte_offs_flag(rec));
	ut_ad(n <= rec_get_n_fields_old(rec));

	return(mach_read_from_2(rec - (REC_N_OLD_EXTRA_BYTES + 2 * n)));
}

/**********************************************************
Sets the field end info for the nth field if the record is stored in the
1-byte format. */
UNIV_INLINE
void
rec_1_set_field_end_info(
/*=====================*/
 	rec_t*	rec, 	/* in: record */
 	ulint	n,	/* in: field index */
 	ulint	info)	/* in: value to set */
{
	ut_ad(rec_get_1byte_offs_flag(rec));
	ut_ad(n < rec_get_n_fields_old(rec));

	mach_write_to_1(rec - (REC_N_OLD_EXTRA_BYTES + n + 1), info);
}

/**********************************************************
Sets the field end info for the nth field if the record is stored in the
2-byte format. */
UNIV_INLINE
void
rec_2_set_field_end_info(
/*=====================*/
 	rec_t*	rec, 	/* in: record */
 	ulint	n,	/* in: field index */
 	ulint	info)	/* in: value to set */
{
	ut_ad(!rec_get_1byte_offs_flag(rec));
	ut_ad(n < rec_get_n_fields_old(rec));

	mach_write_to_2(rec - (REC_N_OLD_EXTRA_BYTES + 2 * n + 2), info);
}

/**********************************************************
Returns the offset of nth field start if the record is stored in the 1-byte
offsets form. */
UNIV_INLINE
ulint
rec_1_get_field_start_offs(
/*=======================*/
 			/* out: offset of the start of the field */
 	rec_t*	rec, 	/* in: record */
 	ulint	n)	/* in: field index */
{
	ut_ad(rec_get_1byte_offs_flag(rec));
	ut_ad(n <= rec_get_n_fields_old(rec));

	if (n == 0) {

		return(0);
	}

	return(rec_1_get_prev_field_end_info(rec, n)
						& ~REC_1BYTE_SQL_NULL_MASK);
}
						
/**********************************************************
Returns the offset of nth field start if the record is stored in the 2-byte
offsets form. */
UNIV_INLINE
ulint
rec_2_get_field_start_offs(
/*=======================*/
 			/* out: offset of the start of the field */
 	rec_t*	rec, 	/* in: record */
 	ulint	n)	/* in: field index */
{
	ut_ad(!rec_get_1byte_offs_flag(rec));
	ut_ad(n <= rec_get_n_fields_old(rec));

	if (n == 0) {

		return(0);
	}

	return(rec_2_get_prev_field_end_info(rec, n)
		& ~(REC_2BYTE_SQL_NULL_MASK | REC_2BYTE_EXTERN_MASK));
}
						
/**********************************************************
The following function is used to read the offset of the start of a data field
in the record. The start of an SQL null field is the end offset of the
previous non-null field, or 0, if none exists. If n is the number of the last
field + 1, then the end offset of the last field is returned. */
UNIV_INLINE
ulint
rec_get_field_start_offs(
/*=====================*/
 			/* out: offset of the start of the field */
 	rec_t*	rec, 	/* in: record */
 	ulint	n)	/* in: field index */
{
	ut_ad(rec);
	ut_ad(n <= rec_get_n_fields_old(rec));

	if (n == 0) {

		return(0);
	}

	if (rec_get_1byte_offs_flag(rec)) {

		return(rec_1_get_field_start_offs(rec, n));
	}

	return(rec_2_get_field_start_offs(rec, n));
}

/****************************************************************
Gets the physical size of an old-style field.
Also an SQL null may have a field of size > 0,
if the data type is of a fixed size. */
UNIV_INLINE
ulint
rec_get_nth_field_size(
/*===================*/
			/* out: field size in bytes */
 	rec_t*	rec, 	/* in: record */
 	ulint	n)	/* in: index of the field */
{
	ulint	os;
	ulint	next_os;

	os = rec_get_field_start_offs(rec, n);
	next_os = rec_get_field_start_offs(rec, n + 1);

	ut_ad(next_os - os < UNIV_PAGE_SIZE);

	return(next_os - os);
}

/*************************************************************** 
This is used to modify the value of an already existing field in a record.
The previous value must have exactly the same size as the new value. If len
is UNIV_SQL_NULL then the field is treated as an SQL null for old-style
records. For new-style records, len must not be UNIV_SQL_NULL. */
UNIV_INLINE
void
rec_set_nth_field(
/*==============*/
	rec_t*		rec,	/* in: record */
	const ulint*	offsets,/* in: array returned by rec_get_offsets() */
	ulint		n,	/* in: index number of the field */
	const void*	data,	/* in: pointer to the data
				if not SQL null */
	ulint		len)	/* in: length of the data or UNIV_SQL_NULL.
				If not SQL null, must have the same
				length as the previous value.
				If SQL null, previous value must be
				SQL null. */
{
	byte*	data2;
	ulint	len2;

	ut_ad(rec);
	ut_ad(rec_offs_validate(rec, NULL, offsets));

	if (len == UNIV_SQL_NULL) {
		ut_ad(!rec_offs_comp(offsets));
		rec_set_nth_field_sql_null(rec, n);

		return;
	}

	data2 = rec_get_nth_field(rec, offsets, n, &len2);
	if (len2 == UNIV_SQL_NULL) {
		ut_ad(!rec_offs_comp(offsets));
		rec_set_nth_field_null_bit(rec, n, FALSE);
		ut_ad(len == rec_get_nth_field_size(rec, n));
	} else {
		ut_ad(len2 == len);
	}

	ut_memcpy(data2, data, len);
}

/************************************************************** 
The following function returns the data size of an old-style physical
record, that is the sum of field lengths. SQL null fields
are counted as length 0 fields. The value returned by the function
is the distance from record origin to record end in bytes. */
UNIV_INLINE
ulint
rec_get_data_size_old(
/*==================*/
				/* out: size */
	rec_t*	rec)	/* in: physical record */
{
	ut_ad(rec);

	return(rec_get_field_start_offs(rec, rec_get_n_fields_old(rec)));
}

/************************************************************** 
The following function sets the number of fields in offsets. */
UNIV_INLINE
void
rec_offs_set_n_fields(
/*==================*/
	ulint*	offsets,	/* in: array returned by rec_get_offsets() */
	ulint	n_fields)	/* in: number of fields */
{
	ut_ad(offsets);
	ut_ad(n_fields > 0);
	ut_ad(n_fields <= REC_MAX_N_FIELDS);
	ut_ad(n_fields + REC_OFFS_HEADER_SIZE
		<= rec_offs_get_n_alloc(offsets));
	offsets[1] = n_fields;
}

/**************************************************************
The following function returns the data size of a physical
record, that is the sum of field lengths. SQL null fields
are counted as length 0 fields. The value returned by the function
is the distance from record origin to record end in bytes. */
UNIV_INLINE
ulint
rec_offs_data_size(
/*===============*/
				/* out: size */
	const ulint*	offsets)/* in: array returned by rec_get_offsets() */
{
	ulint	size;

	ut_ad(rec_offs_validate(NULL, NULL, offsets));
	size = rec_offs_base(offsets)[rec_offs_n_fields(offsets)]
			& REC_OFFS_MASK;
	ut_ad(size < UNIV_PAGE_SIZE);
	return(size);
}

/**************************************************************
Returns the total size of record minus data size of record. The value
returned by the function is the distance from record start to record origin
in bytes. */
UNIV_INLINE
ulint
rec_offs_extra_size(
/*================*/
				/* out: size */
	const ulint*	offsets)/* in: array returned by rec_get_offsets() */
{
	ulint	size;
	ut_ad(rec_offs_validate(NULL, NULL, offsets));
	size = *rec_offs_base(offsets) & ~REC_OFFS_COMPACT;
	ut_ad(size < UNIV_PAGE_SIZE);
	return(size);
}

/**************************************************************
Returns the total size of a physical record.  */
UNIV_INLINE
ulint
rec_offs_size(
/*==========*/
				/* out: size */
	const ulint*	offsets)/* in: array returned by rec_get_offsets() */
{
	return(rec_offs_data_size(offsets) + rec_offs_extra_size(offsets));
}
	
/**************************************************************
Returns a pointer to the end of the record. */
UNIV_INLINE
byte*
rec_get_end(
/*========*/
				/* out: pointer to end */
	rec_t*		rec,	/* in: pointer to record */
	const ulint*	offsets)/* in: array returned by rec_get_offsets() */
{
	return(rec + rec_offs_data_size(offsets));
}

/**************************************************************
Returns a pointer to the start of the record. */
UNIV_INLINE
byte*
rec_get_start(
/*==========*/
				/* out: pointer to start */
	rec_t*		rec,	/* in: pointer to record */
	const ulint*	offsets)/* in: array returned by rec_get_offsets() */
{
	return(rec - rec_offs_extra_size(offsets));
}

/*******************************************************************
Copies a physical record to a buffer. */
UNIV_INLINE
rec_t*
rec_copy(
/*=====*/
				/* out: pointer to the origin of the copy */
	void*		buf,	/* in: buffer */
	const rec_t*	rec,	/* in: physical record */
	const ulint*	offsets)/* in: array returned by rec_get_offsets() */
{
	ulint	extra_len;
	ulint	data_len;
	
	ut_ad(rec && buf);
	ut_ad(rec_offs_validate((rec_t*) rec, NULL, offsets));
	ut_ad(rec_validate((rec_t*) rec, offsets));

	extra_len = rec_offs_extra_size(offsets);
	data_len = rec_offs_data_size(offsets);

	ut_memcpy(buf, rec - extra_len, extra_len + data_len);

	return((byte*)buf + extra_len);
}

/**************************************************************
Returns the extra size of an old-style physical record if we know its
data size and number of fields. */
UNIV_INLINE
ulint
rec_get_converted_extra_size(
/*=========================*/
				/* out: extra size */
	ulint	data_size,	/* in: data size */
	ulint	n_fields)	/* in: number of fields */
{
	if (data_size <= REC_1BYTE_OFFS_LIMIT) {

		return(REC_N_OLD_EXTRA_BYTES + n_fields);
	}

	return(REC_N_OLD_EXTRA_BYTES + 2 * n_fields);
}

/**************************************************************
The following function returns the size of a data tuple when converted to
a new-style physical record. */

ulint
rec_get_converted_size_new(
/*=======================*/
				/* out: size */
	dict_index_t*	index,	/* in: record descriptor */
	dtuple_t*	dtuple);/* in: data tuple */
/**************************************************************
The following function returns the size of a data tuple when converted to
a physical record. */
UNIV_INLINE
ulint
rec_get_converted_size(
/*===================*/
				/* out: size */
	dict_index_t*	index,	/* in: record descriptor */
	dtuple_t*	dtuple)	/* in: data tuple */
{
	ulint	data_size;
	ulint	extra_size;

	ut_ad(index);
	ut_ad(dtuple);
	ut_ad(dtuple_check_typed(dtuple));

	ut_ad(index->type & DICT_UNIVERSAL
		|| dtuple_get_n_fields(dtuple) ==
		(((dtuple_get_info_bits(dtuple) & REC_NEW_STATUS_MASK)
			== REC_STATUS_NODE_PTR)
				? dict_index_get_n_unique_in_tree(index) + 1
				: dict_index_get_n_fields(index)));

	if (UNIV_LIKELY(index->table->comp)) {
		return(rec_get_converted_size_new(index, dtuple));
	}

	data_size = dtuple_get_data_size(dtuple);

	extra_size = rec_get_converted_extra_size(
				data_size, dtuple_get_n_fields(dtuple));

	return(data_size + extra_size);
}

/****************************************************************
Folds a prefix of a physical record to a ulint. Folds only existing fields,
that is, checks that we do not run out of the record. */
UNIV_INLINE
ulint
rec_fold(
/*=====*/
					/* out: the folded value */
	rec_t*		rec,		/* in: the physical record */
	const ulint*	offsets,	/* in: array returned by
					rec_get_offsets() */
	ulint		n_fields,	/* in: number of complete
					fields to fold */
	ulint		n_bytes,	/* in: number of bytes to fold
					in an incomplete last field */
	dulint		tree_id)	/* in: index tree id */
{
	ulint	i;
	byte*	data;
	ulint	len;
	ulint	fold;
	ulint	n_fields_rec;

	ut_ad(rec_offs_validate(rec, NULL, offsets));
	ut_ad(rec_validate((rec_t*) rec, offsets));
	ut_ad(n_fields + n_bytes > 0);

	n_fields_rec = rec_offs_n_fields(offsets);
	ut_ad(n_fields <= n_fields_rec);
	ut_ad(n_fields < n_fields_rec || n_bytes == 0);

	if (n_fields > n_fields_rec) {
	        n_fields = n_fields_rec;
	}

	if (n_fields == n_fields_rec) {
	        n_bytes = 0;
	}

	fold = ut_fold_dulint(tree_id);
	
	for (i = 0; i < n_fields; i++) {
		data = rec_get_nth_field(rec, offsets, i, &len);

		if (len != UNIV_SQL_NULL) {
			fold = ut_fold_ulint_pair(fold,
						  ut_fold_binary(data, len));
		}
	}

	if (n_bytes > 0) {
		data = rec_get_nth_field(rec, offsets, i, &len);

		if (len != UNIV_SQL_NULL) {
			if (len > n_bytes) {
				len = n_bytes;
			}
		
			fold = ut_fold_ulint_pair(fold,
						  ut_fold_binary(data, len));
		}
	}

	return(fold);
}