blob: e5f5cbf5482dba56ea43c780cdbccd501051cc3e (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
|
/*-------------------------------------------------------------------------
*
* off.h--
* POSTGRES disk "offset" definitions.
*
*
* Copyright (c) 1994, Regents of the University of California
*
* $Id: off.h,v 1.1.1.1 1996/07/09 06:21:53 scrappy Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef OFF_H
#define OFF_H
#include "c.h"
#include "machine.h" /* for BLCKSZ */
#include "storage/itemid.h"
/*
* OffsetNumber:
*
* this is a 1-based index into the linp (ItemIdData) array in the
* header of each disk page.
*/
typedef uint16 OffsetNumber;
#define InvalidOffsetNumber ((OffsetNumber) 0)
#define FirstOffsetNumber ((OffsetNumber) 1)
#define MaxOffsetNumber ((OffsetNumber) (BLCKSZ / sizeof(ItemIdData)))
#define OffsetNumberMask (0xffff) /* valid uint16 bits */
/* ----------------
* support macros
* ----------------
*/
/*
* OffsetNumberIsValid --
* True iff the offset number is valid.
*/
#define OffsetNumberIsValid(offsetNumber) \
((bool) ((offsetNumber != InvalidOffsetNumber) && \
(offsetNumber <= MaxOffsetNumber)))
/*
* OffsetNumberNext --
* OffsetNumberPrev --
* Increments/decrements the argument. These macros look pointless
* but they help us disambiguate the different manipulations on
* OffsetNumbers (e.g., sometimes we substract one from an
* OffsetNumber to move back, and sometimes we do so to form a
* real C array index).
*/
#define OffsetNumberNext(offsetNumber) \
((OffsetNumber) (1 + (offsetNumber)))
#define OffsetNumberPrev(offsetNumber) \
((OffsetNumber) (-1 + (offsetNumber)))
#endif /* OFF_H */
|
