Age Owner Branch data TLA Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * block.h
4 : : * POSTGRES disk block definitions.
5 : : *
6 : : *
7 : : * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
8 : : * Portions Copyright (c) 1994, Regents of the University of California
9 : : *
10 : : * src/include/storage/block.h
11 : : *
12 : : *-------------------------------------------------------------------------
13 : : */
14 : : #ifndef BLOCK_H
15 : : #define BLOCK_H
16 : :
17 : : /*
18 : : * BlockNumber:
19 : : *
20 : : * each data file (heap or index) is divided into postgres disk blocks
21 : : * (which may be thought of as the unit of i/o -- a postgres buffer
22 : : * contains exactly one disk block). the blocks are numbered
23 : : * sequentially, 0 to 0xFFFFFFFE.
24 : : *
25 : : * InvalidBlockNumber is the same thing as P_NEW in bufmgr.h.
26 : : *
27 : : * the access methods, the buffer manager and the storage manager are
28 : : * more or less the only pieces of code that should be accessing disk
29 : : * blocks directly.
30 : : */
31 : : typedef uint32 BlockNumber;
32 : :
33 : : #define InvalidBlockNumber ((BlockNumber) 0xFFFFFFFF)
34 : :
35 : : #define MaxBlockNumber ((BlockNumber) 0xFFFFFFFE)
36 : :
37 : : /*
38 : : * BlockId:
39 : : *
40 : : * this is a storage type for BlockNumber. in other words, this type
41 : : * is used for on-disk structures (e.g., in HeapTupleData) whereas
42 : : * BlockNumber is the type on which calculations are performed (e.g.,
43 : : * in access method code).
44 : : *
45 : : * there doesn't appear to be any reason to have separate types except
46 : : * for the fact that BlockIds can be SHORTALIGN'd (and therefore any
47 : : * structures that contains them, such as ItemPointerData, can also be
48 : : * SHORTALIGN'd). this is an important consideration for reducing the
49 : : * space requirements of the line pointer (ItemIdData) array on each
50 : : * page and the header of each heap or index tuple, so it doesn't seem
51 : : * wise to change this without good reason.
52 : : */
53 : : typedef struct BlockIdData
54 : : {
55 : : uint16 bi_hi;
56 : : uint16 bi_lo;
57 : : } BlockIdData;
58 : :
59 : : typedef BlockIdData *BlockId; /* block identifier */
60 : :
61 : : /* ----------------
62 : : * support functions
63 : : * ----------------
64 : : */
65 : :
66 : : /*
67 : : * BlockNumberIsValid
68 : : * True iff blockNumber is valid.
69 : : */
70 : : static inline bool
647 peter@eisentraut.org 71 :CBC 133875309 : BlockNumberIsValid(BlockNumber blockNumber)
72 : : {
73 : 133875309 : return blockNumber != InvalidBlockNumber;
74 : : }
75 : :
76 : : /*
77 : : * BlockIdSet
78 : : * Sets a block identifier to the specified value.
79 : : */
80 : : static inline void
81 : 408497863 : BlockIdSet(BlockIdData *blockId, BlockNumber blockNumber)
82 : : {
83 : 408497863 : blockId->bi_hi = blockNumber >> 16;
84 : 408497863 : blockId->bi_lo = blockNumber & 0xffff;
85 : 408497863 : }
86 : :
87 : : /*
88 : : * BlockIdEquals
89 : : * Check for block number equality.
90 : : */
91 : : static inline bool
92 : : BlockIdEquals(const BlockIdData *blockId1, const BlockIdData *blockId2)
93 : : {
94 : : return (blockId1->bi_hi == blockId2->bi_hi &&
95 : : blockId1->bi_lo == blockId2->bi_lo);
96 : : }
97 : :
98 : : /*
99 : : * BlockIdGetBlockNumber
100 : : * Retrieve the block number from a block identifier.
101 : : */
102 : : static inline BlockNumber
103 : 249768713 : BlockIdGetBlockNumber(const BlockIdData *blockId)
104 : : {
105 : 249768713 : return (((BlockNumber) blockId->bi_hi) << 16) | ((BlockNumber) blockId->bi_lo);
106 : : }
107 : :
108 : : #endif /* BLOCK_H */
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