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/*-------------------------------------------------------------------------
*
* itemptr.h--
* POSTGRES disk item pointer definitions.
*
*
* Copyright (c) 1994, Regents of the University of California
*
* $Id: itemptr.h,v 1.1.1.1 1996/07/09 06:21:53 scrappy Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef ITEMPTR_H
#define ITEMPTR_H
#include "c.h"
#include "storage/block.h"
#include "storage/off.h"
#include "storage/itemid.h"
/*
* ItemPointer:
*
* this is a pointer to an item on another disk page in the same file.
* blkid tells us which block, posid tells us which entry in the linp
* (ItemIdData) array we want.
*/
typedef struct ItemPointerData {
BlockIdData ip_blkid;
OffsetNumber ip_posid;
} ItemPointerData;
typedef ItemPointerData *ItemPointer;
/* ----------------
* support macros
* ----------------
*/
/*
* ItemPointerIsValid --
* True iff the disk item pointer is not NULL.
*/
#define ItemPointerIsValid(pointer) \
((bool) (PointerIsValid(pointer) && ((pointer)->ip_posid != 0)))
/*
* ItemPointerGetBlockNumber --
* Returns the block number of a disk item pointer.
*/
#define ItemPointerGetBlockNumber(pointer) \
(AssertMacro(ItemPointerIsValid(pointer)) ? \
BlockIdGetBlockNumber(&(pointer)->ip_blkid) : (BlockNumber) 0)
/*
* ItemPointerGetOffsetNumber --
* Returns the offset number of a disk item pointer.
*/
#define ItemPointerGetOffsetNumber(pointer) \
(AssertMacro(ItemPointerIsValid(pointer)) ? \
(pointer)->ip_posid : \
InvalidOffsetNumber)
/*
* ItemPointerSet --
* Sets a disk item pointer to the specified block and offset.
*/
#define ItemPointerSet(pointer, blockNumber, offNum) \
Assert(PointerIsValid(pointer)); \
BlockIdSet(&((pointer)->ip_blkid), blockNumber); \
(pointer)->ip_posid = offNum
/*
* ItemPointerSetBlockNumber --
* Sets a disk item pointer to the specified block.
*/
#define ItemPointerSetBlockNumber(pointer, blockNumber) \
Assert(PointerIsValid(pointer)); \
BlockIdSet(&((pointer)->ip_blkid), blockNumber)
/*
* ItemPointerSetOffsetNumber --
* Sets a disk item pointer to the specified offset.
*/
#define ItemPointerSetOffsetNumber(pointer, offsetNumber) \
AssertMacro(PointerIsValid(pointer)); \
(pointer)->ip_posid = (offsetNumber)
/*
* ItemPointerCopy --
* Copies the contents of one disk item pointer to another.
*/
#define ItemPointerCopy(fromPointer, toPointer) \
Assert(PointerIsValid(toPointer)); \
Assert(PointerIsValid(fromPointer)); \
*(toPointer) = *(fromPointer)
/*
* ItemPointerSetInvalid --
* Sets a disk item pointer to be invalid.
*/
#define ItemPointerSetInvalid(pointer) \
Assert(PointerIsValid(pointer)); \
BlockIdSet(&((pointer)->ip_blkid), InvalidBlockNumber); \
(pointer)->ip_posid = InvalidOffsetNumber
/* ----------------
* externs
* ----------------
*/
extern bool ItemPointerEquals(ItemPointer pointer1, ItemPointer pointer2);
#endif /* ITEMPTR_H */
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