Age Owner TLA Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * block.h
4 : * POSTGRES disk block definitions.
5 : *
6 : *
7 : * Portions Copyright (c) 1996-2023, 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
276 peter 71 GNC 168154934 : BlockNumberIsValid(BlockNumber blockNumber)
72 : {
73 168154934 : return blockNumber != InvalidBlockNumber;
74 : }
75 :
76 : /*
8720 bruce 77 ECB : * BlockIdSet
78 : * Sets a block identifier to the specified value.
9720 scrappy 79 : */
80 : static inline void
276 peter 81 GNC 690697407 : BlockIdSet(BlockIdData *blockId, BlockNumber blockNumber)
82 : {
83 690697407 : blockId->bi_hi = blockNumber >> 16;
84 690697407 : blockId->bi_lo = blockNumber & 0xffff;
85 690697407 : }
86 :
87 : /*
88 : * BlockIdEquals
89 : * Check for block number equality.
9720 scrappy 90 ECB : */
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
276 peter 103 GNC 420768848 : BlockIdGetBlockNumber(const BlockIdData *blockId)
104 : {
105 420768848 : return (((BlockNumber) blockId->bi_hi) << 16) | ((BlockNumber) blockId->bi_lo);
106 : }
107 :
108 : #endif /* BLOCK_H */
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