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98 lines
2.0 KiB
C
98 lines
2.0 KiB
C
/*-------------------------------------------------------------------------
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*
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* itemid.h
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* Standard POSTGRES buffer page item identifier definitions.
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*
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*
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* Portions Copyright (c) 1996-2001, 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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* $Id: itemid.h,v 1.19 2001/11/05 17:46:35 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef ITEMID_H
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#define ITEMID_H
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/*
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* An item pointer (also called line pointer) on a buffer page
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*/
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typedef struct ItemIdData
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{ /* line pointers */
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unsigned lp_off:15, /* offset to start of tuple */
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lp_flags:2, /* flags for tuple */
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lp_len:15; /* length of tuple */
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} ItemIdData;
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typedef ItemIdData *ItemId;
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/*
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* lp_flags contains these flags:
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*/
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#define LP_USED 0x01 /* this line pointer is being used */
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#define LP_DELETE 0x02 /* item is to be deleted */
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#define ItemIdDeleted(itemId) \
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(((itemId)->lp_flags & LP_DELETE) != 0)
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/*
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* This bit may be passed to PageAddItem together with
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* LP_USED & LP_DELETED bits to specify overwrite mode
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*/
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#define OverwritePageMode 0x10
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/*
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* Item offsets, lengths, and flags are represented by these types when
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* they're not actually stored in an ItemIdData.
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*/
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typedef uint16 ItemOffset;
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typedef uint16 ItemLength;
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typedef bits16 ItemIdFlags;
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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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* ItemIdGetLength
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*/
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#define ItemIdGetLength(itemId) \
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((itemId)->lp_len)
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/*
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* ItemIdGetOffset
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*/
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#define ItemIdGetOffset(itemId) \
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((itemId)->lp_off)
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/*
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* ItemIdGetFlags
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*/
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#define ItemIdGetFlags(itemId) \
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((itemId)->lp_flags)
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/*
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* ItemIdIsValid
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* True iff disk item identifier is valid.
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*/
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#define ItemIdIsValid(itemId) PointerIsValid(itemId)
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/*
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* ItemIdIsUsed
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* True iff disk item identifier is in use.
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*
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* Note:
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* Assumes disk item identifier is valid.
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*/
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#define ItemIdIsUsed(itemId) \
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( \
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AssertMacro(ItemIdIsValid(itemId)), \
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(bool) (((itemId)->lp_flags & LP_USED) != 0) \
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)
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#endif /* ITEMID_H */
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