/*-------------------------------------------------------------------------
*
* pos.h
* POSTGRES "position" definitions.
*
*
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/storage/pos.h,v 1.23 2009/01/01 17:24:01 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef POS_H
#define POS_H
/*
* a 'position' used to be <pagenumber, offset> in postgres. this has
* been changed to just <offset> as the notion of having multiple pages
* within a block has been removed.
*
* the 'offset' abstraction is somewhat confusing. it is NOT a byte
* offset within the page; instead, it is an offset into the line
* pointer array contained on every page that store (heap or index)
* tuples.
*/
typedef bits16 PositionIdData;
typedef PositionIdData *PositionId;
/* ----------------
* support macros
* ----------------
*/
/*
* PositionIdIsValid
* True iff the position identifier is valid.
*/
#define PositionIdIsValid(positionId) \
PointerIsValid(positionId)
/*
* PositionIdSetInvalid
* Make an invalid position.
*/
#define PositionIdSetInvalid(positionId) \
*(positionId) = (bits16) 0
/*
* PositionIdSet
* Sets a position identifier to the specified value.
*/
#define PositionIdSet(positionId, offsetNumber) \
*(positionId) = (offsetNumber)
/*
* PositionIdGetOffsetNumber
* Retrieve the offset number from a position identifier.
*/
#define PositionIdGetOffsetNumber(positionId) \
((OffsetNumber) *(positionId))
#endif /* POS_H */
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