1996-08-28 03:59:28 +02:00
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/*-------------------------------------------------------------------------
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*
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1999-02-14 00:22:53 +01:00
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* off.h
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1997-09-07 07:04:48 +02:00
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* POSTGRES disk "offset" definitions.
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1996-08-28 03:59:28 +02:00
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*
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*
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* Copyright (c) 1994, Regents of the University of California
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*
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1999-02-14 00:22:53 +01:00
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* $Id: off.h,v 1.6 1999/02/13 23:22:08 momjian Exp $
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1996-08-28 03:59:28 +02:00
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*
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*-------------------------------------------------------------------------
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*/
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1997-09-07 07:04:48 +02:00
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#ifndef OFF_H
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1996-08-28 03:59:28 +02:00
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#define OFF_H
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/*
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* OffsetNumber:
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*
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* this is a 1-based index into the linp (ItemIdData) array in the
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* header of each disk page.
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*/
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1997-09-08 04:41:22 +02:00
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typedef uint16 OffsetNumber;
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1996-08-28 03:59:28 +02:00
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1997-09-07 07:04:48 +02:00
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#define InvalidOffsetNumber ((OffsetNumber) 0)
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#define FirstOffsetNumber ((OffsetNumber) 1)
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#define MaxOffsetNumber ((OffsetNumber) (BLCKSZ / sizeof(ItemIdData)))
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#define OffsetNumberMask (0xffff) /* valid uint16 bits */
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1996-08-28 03:59:28 +02:00
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/* ----------------
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1997-09-07 07:04:48 +02:00
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* support macros
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1996-08-28 03:59:28 +02:00
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* ----------------
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*/
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/*
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1999-02-14 00:22:53 +01:00
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* OffsetNumberIsValid
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1997-09-07 07:04:48 +02:00
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* True iff the offset number is valid.
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1996-08-28 03:59:28 +02:00
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*/
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#define OffsetNumberIsValid(offsetNumber) \
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1997-09-07 07:04:48 +02:00
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((bool) ((offsetNumber != InvalidOffsetNumber) && \
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(offsetNumber <= MaxOffsetNumber)))
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1996-08-28 03:59:28 +02:00
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/*
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1999-02-14 00:22:53 +01:00
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* OffsetNumberNext
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* OffsetNumberPrev
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1997-09-07 07:04:48 +02:00
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* Increments/decrements the argument. These macros look pointless
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* but they help us disambiguate the different manipulations on
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* OffsetNumbers (e.g., sometimes we substract one from an
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* OffsetNumber to move back, and sometimes we do so to form a
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* real C array index).
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1996-08-28 03:59:28 +02:00
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*/
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#define OffsetNumberNext(offsetNumber) \
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1997-09-07 07:04:48 +02:00
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((OffsetNumber) (1 + (offsetNumber)))
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1996-08-28 03:59:28 +02:00
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#define OffsetNumberPrev(offsetNumber) \
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1997-09-07 07:04:48 +02:00
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((OffsetNumber) (-1 + (offsetNumber)))
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1996-08-28 03:59:28 +02:00
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1998-09-01 06:40:42 +02:00
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#endif /* OFF_H */
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