/Users/deen/code/yugabyte-db/src/postgres/src/include/utils/pg_crc.h
Line | Count | Source (jump to first uncovered line) |
1 | | /* |
2 | | * pg_crc.h |
3 | | * |
4 | | * PostgreSQL CRC support |
5 | | * |
6 | | * See Ross Williams' excellent introduction |
7 | | * A PAINLESS GUIDE TO CRC ERROR DETECTION ALGORITHMS, available from |
8 | | * http://www.ross.net/crc/ or several other net sites. |
9 | | * |
10 | | * We have three slightly different variants of a 32-bit CRC calculation: |
11 | | * CRC-32C (Castagnoli polynomial), CRC-32 (Ethernet polynomial), and a legacy |
12 | | * CRC-32 version that uses the lookup table in a funny way. They all consist |
13 | | * of four macros: |
14 | | * |
15 | | * INIT_<variant>(crc) |
16 | | * Initialize a CRC accumulator |
17 | | * |
18 | | * COMP_<variant>(crc, data, len) |
19 | | * Accumulate some (more) bytes into a CRC |
20 | | * |
21 | | * FIN_<variant>(crc) |
22 | | * Finish a CRC calculation |
23 | | * |
24 | | * EQ_<variant>(c1, c2) |
25 | | * Check for equality of two CRCs. |
26 | | * |
27 | | * The CRC-32C variant is in port/pg_crc32c.h. |
28 | | * |
29 | | * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group |
30 | | * Portions Copyright (c) 1994, Regents of the University of California |
31 | | * |
32 | | * src/include/utils/pg_crc.h |
33 | | */ |
34 | | #ifndef PG_CRC_H |
35 | | #define PG_CRC_H |
36 | | |
37 | | typedef uint32 pg_crc32; |
38 | | |
39 | | /* |
40 | | * CRC-32, the same used e.g. in Ethernet. |
41 | | * |
42 | | * This is currently only used in ltree and hstore contrib modules. It uses |
43 | | * the same lookup table as the legacy algorithm below. New code should |
44 | | * use the Castagnoli version instead. |
45 | | */ |
46 | | #define INIT_TRADITIONAL_CRC32(crc) ((crc) = 0xFFFFFFFF) |
47 | | #define FIN_TRADITIONAL_CRC32(crc) ((crc) ^= 0xFFFFFFFF) |
48 | | #define COMP_TRADITIONAL_CRC32(crc, data, len) \ |
49 | | COMP_CRC32_NORMAL_TABLE(crc, data, len, pg_crc32_table) |
50 | | #define EQ_TRADITIONAL_CRC32(c1, c2) ((c1) == (c2)) |
51 | | |
52 | | /* Sarwate's algorithm, for use with a "normal" lookup table */ |
53 | | #define COMP_CRC32_NORMAL_TABLE(crc, data, len, table) \ |
54 | | do { \ |
55 | | const unsigned char *__data = (const unsigned char *) (data); \ |
56 | | uint32 __len = (len); \ |
57 | | \ |
58 | | while (__len-- > 0) \ |
59 | | { \ |
60 | | int __tab_index = ((int) (crc) ^ *__data++) & 0xFF; \ |
61 | | (crc) = table[__tab_index] ^ ((crc) >> 8); \ |
62 | | } \ |
63 | | } while (0) |
64 | | |
65 | | /* |
66 | | * The CRC algorithm used for WAL et al in pre-9.5 versions. |
67 | | * |
68 | | * This closely resembles the normal CRC-32 algorithm, but is subtly |
69 | | * different. Using Williams' terms, we use the "normal" table, but with |
70 | | * "reflected" code. That's bogus, but it was like that for years before |
71 | | * anyone noticed. It does not correspond to any polynomial in a normal CRC |
72 | | * algorithm, so it's not clear what the error-detection properties of this |
73 | | * algorithm actually are. |
74 | | * |
75 | | * We still need to carry this around because it is used in a few on-disk |
76 | | * structures that need to be pg_upgradeable. It should not be used in new |
77 | | * code. |
78 | | */ |
79 | 0 | #define INIT_LEGACY_CRC32(crc) ((crc) = 0xFFFFFFFF) |
80 | 0 | #define FIN_LEGACY_CRC32(crc) ((crc) ^= 0xFFFFFFFF) |
81 | | #define COMP_LEGACY_CRC32(crc, data, len) \ |
82 | 0 | COMP_CRC32_REFLECTED_TABLE(crc, data, len, pg_crc32_table) |
83 | | #define EQ_LEGACY_CRC32(c1, c2) ((c1) == (c2)) |
84 | | |
85 | | /* |
86 | | * Sarwate's algorithm, for use with a "reflected" lookup table (but in the |
87 | | * legacy algorithm, we actually use it on a "normal" table, see above) |
88 | | */ |
89 | 0 | #define COMP_CRC32_REFLECTED_TABLE(crc, data, len, table) \ |
90 | 0 | do { \ |
91 | 0 | const unsigned char *__data = (const unsigned char *) (data); \ |
92 | 0 | uint32 __len = (len); \ |
93 | 0 | \ |
94 | 0 | while (__len-- > 0) \ |
95 | 0 | { \ |
96 | 0 | int __tab_index = ((int) ((crc) >> 24) ^ *__data++) & 0xFF; \ |
97 | 0 | (crc) = table[__tab_index] ^ ((crc) << 8); \ |
98 | 0 | } \ |
99 | 0 | } while (0) |
100 | | |
101 | | /* |
102 | | * Constant table for the CRC-32 polynomials. The same table is used by both |
103 | | * the normal and traditional variants. |
104 | | */ |
105 | | extern PGDLLIMPORT const uint32 pg_crc32_table[256]; |
106 | | |
107 | | #endif /* PG_CRC_H */ |