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/*-------------------------------------------------------------------------
*
* sdir.h
* POSTGRES scan direction definitions.
*
*
* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/access/sdir.h
*
*-------------------------------------------------------------------------
*/
#ifndef SDIR_H
#define SDIR_H
/*
* Defines the direction for scanning a table or an index. Scans are never
* invoked using NoMovementScanDirectionScans. For convenience, we use the
* values -1 and 1 for backward and forward scans. This allows us to perform
* a few mathematical tricks such as what is done in ScanDirectionCombine.
*/
typedef enum ScanDirection
{
BackwardScanDirection = -1,
NoMovementScanDirection = 0,
ForwardScanDirection = 1
} ScanDirection;
/*
* Determine the net effect of two direction specifications.
* This relies on having ForwardScanDirection = +1, BackwardScanDirection = -1,
* and will probably not do what you want if applied to any other values.
*/
#define ScanDirectionCombine(a, b) ((a) * (b))
/*
* ScanDirectionIsValid
* True iff scan direction is valid.
*/
#define ScanDirectionIsValid(direction) \
((bool) (BackwardScanDirection <= (direction) && \
(direction) <= ForwardScanDirection))
/*
* ScanDirectionIsBackward
* True iff scan direction is backward.
*/
#define ScanDirectionIsBackward(direction) \
((bool) ((direction) == BackwardScanDirection))
/*
* ScanDirectionIsNoMovement
* True iff scan direction indicates no movement.
*/
#define ScanDirectionIsNoMovement(direction) \
((bool) ((direction) == NoMovementScanDirection))
/*
* ScanDirectionIsForward
* True iff scan direction is forward.
*/
#define ScanDirectionIsForward(direction) \
((bool) ((direction) == ForwardScanDirection))
#endif /* SDIR_H */
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