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/*------------------------------------------------------------------------- * * pos.h * POSTGRES "position" definitions. * * * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * src/include/storage/pos.h * *------------------------------------------------------------------------- */ #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 */