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Viewing changes to src/include/storage/off.h

  • Committer: Bazaar Package Importer
  • Author(s): Martin Pitt
  • Date: 2011-05-11 10:41:53 UTC
  • Revision ID: james.westby@ubuntu.com-20110511104153-psbh2o58553fv1m0
Tags: upstream-9.1~beta1
Import upstream version 9.1~beta1

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src/include/storage/off.h
 
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/*-------------------------------------------------------------------------
 
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 *
 
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 * off.h
 
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 *        POSTGRES disk "offset" definitions.
 
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 *
 
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 *
 
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 * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
 
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 * Portions Copyright (c) 1994, Regents of the University of California
 
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 *
 
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 * src/include/storage/off.h
 
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 *
 
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 *-------------------------------------------------------------------------
 
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 */
 
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#ifndef OFF_H
 
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#define OFF_H
 
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#include "storage/itemid.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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typedef uint16 OffsetNumber;
 
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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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/* ----------------
 
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 *              support macros
 
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 * ----------------
 
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 */
 
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/*
 
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 * OffsetNumberIsValid
 
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 *              True iff the offset number is valid.
 
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 */
 
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#define OffsetNumberIsValid(offsetNumber) \
 
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        ((bool) ((offsetNumber != InvalidOffsetNumber) && \
 
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                         (offsetNumber <= MaxOffsetNumber)))
 
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/*
 
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 * OffsetNumberNext
 
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 * OffsetNumberPrev
 
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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 subtract 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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 */
 
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#define OffsetNumberNext(offsetNumber) \
 
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        ((OffsetNumber) (1 + (offsetNumber)))
 
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#define OffsetNumberPrev(offsetNumber) \
 
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        ((OffsetNumber) (-1 + (offsetNumber)))
 
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#endif   /* OFF_H */