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pg_crc32c.h
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1 /*-------------------------------------------------------------------------
2  *
3  * pg_crc32c.h
4  * Routines for computing CRC-32C checksums.
5  *
6  * The speed of CRC-32C calculation has a big impact on performance, so we
7  * jump through some hoops to get the best implementation for each
8  * platform. Some CPU architectures have special instructions for speeding
9  * up CRC calculations (e.g. Intel SSE 4.2), on other platforms we use the
10  * Slicing-by-8 algorithm which uses lookup tables.
11  *
12  * The public interface consists of four macros:
13  *
14  * INIT_CRC32C(crc)
15  * Initialize a CRC accumulator
16  *
17  * COMP_CRC32C(crc, data, len)
18  * Accumulate some (more) bytes into a CRC
19  *
20  * FIN_CRC32C(crc)
21  * Finish a CRC calculation
22  *
23  * EQ_CRC32C(c1, c2)
24  * Check for equality of two CRCs.
25  *
26  * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
27  * Portions Copyright (c) 1994, Regents of the University of California
28  *
29  * src/include/port/pg_crc32c.h
30  *
31  *-------------------------------------------------------------------------
32  */
33 #ifndef PG_CRC32C_H
34 #define PG_CRC32C_H
35 
36 #include "port/pg_bswap.h"
37 
38 typedef uint32 pg_crc32c;
39 
40 /* The INIT and EQ macros are the same for all implementations. */
41 #define INIT_CRC32C(crc) ((crc) = 0xFFFFFFFF)
42 #define EQ_CRC32C(c1, c2) ((c1) == (c2))
43 
44 #if defined(USE_SSE42_CRC32C)
45 /* Use SSE4.2 instructions. */
46 #define COMP_CRC32C(crc, data, len) \
47  ((crc) = pg_comp_crc32c_sse42((crc), (data), (len)))
48 #define FIN_CRC32C(crc) ((crc) ^= 0xFFFFFFFF)
49 
50 extern pg_crc32c pg_comp_crc32c_sse42(pg_crc32c crc, const void *data, size_t len);
51 
52 #elif defined(USE_SSE42_CRC32C_WITH_RUNTIME_CHECK)
53 /*
54  * Use SSE4.2 instructions, but perform a runtime check first to check that
55  * they are available.
56  */
57 #define COMP_CRC32C(crc, data, len) \
58  ((crc) = pg_comp_crc32c((crc), (data), (len)))
59 #define FIN_CRC32C(crc) ((crc) ^= 0xFFFFFFFF)
60 
61 extern pg_crc32c pg_comp_crc32c_sse42(pg_crc32c crc, const void *data, size_t len);
62 extern pg_crc32c pg_comp_crc32c_sb8(pg_crc32c crc, const void *data, size_t len);
63 extern pg_crc32c (*pg_comp_crc32c) (pg_crc32c crc, const void *data, size_t len);
64 
65 #else
66 /*
67  * Use slicing-by-8 algorithm.
68  *
69  * On big-endian systems, the intermediate value is kept in reverse byte
70  * order, to avoid byte-swapping during the calculation. FIN_CRC32C reverses
71  * the bytes to the final order.
72  */
73 #define COMP_CRC32C(crc, data, len) \
74  ((crc) = pg_comp_crc32c_sb8((crc), (data), (len)))
75 #ifdef WORDS_BIGENDIAN
76 #define FIN_CRC32C(crc) ((crc) = BSWAP32(crc) ^ 0xFFFFFFFF)
77 #else
78 #define FIN_CRC32C(crc) ((crc) ^= 0xFFFFFFFF)
79 #endif
80 
81 extern pg_crc32c pg_comp_crc32c_sb8(pg_crc32c crc, const void *data, size_t len);
82 
83 #endif
84 
85 #endif /* PG_CRC32C_H */
uint32 pg_crc32c
Definition: pg_crc32c.h:38
pg_crc32c pg_comp_crc32c_sb8(pg_crc32c crc, const void *data, size_t len)
Definition: pg_crc32c_sb8.c:35
pg_crc32c(* pg_comp_crc32c)(pg_crc32c crc, const void *data, size_t len)
pg_crc32c pg_comp_crc32c_sse42(pg_crc32c crc, const void *data, size_t len)
unsigned int uint32
Definition: c.h:268