4 * PostgreSQL CRC support
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.
10 * We use a normal (not "reflected", in Williams' terms) CRC, using initial
11 * all-ones register contents and a final bit inversion.
13 * The 64-bit variant is not used as of PostgreSQL 8.1, but we retain the
14 * code for possible future use.
17 * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
18 * Portions Copyright (c) 1994, Regents of the University of California
20 * src/include/utils/pg_crc.h
25 /* ugly hack to let this be used in frontend and backend code on Cygwin */
29 #define CRCDLLIMPORT PGDLLIMPORT
32 typedef uint32 pg_crc32;
34 /* Initialize a CRC accumulator */
35 #define INIT_CRC32(crc) ((crc) = 0xFFFFFFFF)
37 /* Finish a CRC calculation */
38 #define FIN_CRC32(crc) ((crc) ^= 0xFFFFFFFF)
40 /* Accumulate some (more) bytes into a CRC */
41 #define COMP_CRC32(crc, data, len) \
43 unsigned char *__data = (unsigned char *) (data); \
44 uint32 __len = (len); \
48 int __tab_index = ((int) ((crc) >> 24) ^ *__data++) & 0xFF; \
49 (crc) = pg_crc32_table[__tab_index] ^ ((crc) << 8); \
53 /* Check for equality of two CRCs */
54 #define EQ_CRC32(c1,c2) ((c1) == (c2))
56 /* Constant table for CRC calculation */
57 extern CRCDLLIMPORT const uint32 pg_crc32_table[];
60 #ifdef PROVIDE_64BIT_CRC
63 * If we use a 64-bit integer type, then a 64-bit CRC looks just like the
64 * usual sort of implementation. However, we can also fake it with two
65 * 32-bit registers. Experience has shown that the two-32-bit-registers code
66 * is as fast as, or even much faster than, the 64-bit code on all but true
67 * 64-bit machines. We use SIZEOF_VOID_P to check the native word width.
73 * crc0 represents the LSBs of the 64-bit value, crc1 the MSBs. Note that
74 * with crc0 placed first, the output of 32-bit and 64-bit implementations
75 * will be bit-compatible only on little-endian architectures. If it were
76 * important to make the two possible implementations bit-compatible on
77 * all machines, we could do a configure test to decide how to order the
78 * two fields, but it seems not worth the trouble.
80 typedef struct pg_crc64
86 /* Initialize a CRC accumulator */
87 #define INIT_CRC64(crc) ((crc).crc0 = 0xffffffff, (crc).crc1 = 0xffffffff)
89 /* Finish a CRC calculation */
90 #define FIN_CRC64(crc) ((crc).crc0 ^= 0xffffffff, (crc).crc1 ^= 0xffffffff)
92 /* Accumulate some (more) bytes into a CRC */
93 #define COMP_CRC64(crc, data, len) \
95 uint32 __crc0 = (crc).crc0; \
96 uint32 __crc1 = (crc).crc1; \
97 unsigned char *__data = (unsigned char *) (data); \
98 uint32 __len = (len); \
100 while (__len-- > 0) \
102 int __tab_index = ((int) (__crc1 >> 24) ^ *__data++) & 0xFF; \
103 __crc1 = pg_crc64_table1[__tab_index] ^ ((__crc1 << 8) | (__crc0 >> 24)); \
104 __crc0 = pg_crc64_table0[__tab_index] ^ (__crc0 << 8); \
106 (crc).crc0 = __crc0; \
107 (crc).crc1 = __crc1; \
110 /* Check for equality of two CRCs */
111 #define EQ_CRC64(c1,c2) ((c1).crc0 == (c2).crc0 && (c1).crc1 == (c2).crc1)
113 /* Constant table for CRC calculation */
114 extern CRCDLLIMPORT const uint32 pg_crc64_table0[];
115 extern CRCDLLIMPORT const uint32 pg_crc64_table1[];
116 #else /* use int64 implementation */
118 typedef struct pg_crc64
123 /* Initialize a CRC accumulator */
124 #define INIT_CRC64(crc) ((crc).crc0 = UINT64CONST(0xffffffffffffffff))
126 /* Finish a CRC calculation */
127 #define FIN_CRC64(crc) ((crc).crc0 ^= UINT64CONST(0xffffffffffffffff))
129 /* Accumulate some (more) bytes into a CRC */
130 #define COMP_CRC64(crc, data, len) \
132 uint64 __crc0 = (crc).crc0; \
133 unsigned char *__data = (unsigned char *) (data); \
134 uint32 __len = (len); \
136 while (__len-- > 0) \
138 int __tab_index = ((int) (__crc0 >> 56) ^ *__data++) & 0xFF; \
139 __crc0 = pg_crc64_table[__tab_index] ^ (__crc0 << 8); \
141 (crc).crc0 = __crc0; \
144 /* Check for equality of two CRCs */
145 #define EQ_CRC64(c1,c2) ((c1).crc0 == (c2).crc0)
147 /* Constant table for CRC calculation */
148 extern CRCDLLIMPORT const uint64 pg_crc64_table[];
149 #endif /* SIZEOF_VOID_P < 8 */
150 #endif /* PROVIDE_64BIT_CRC */
152 #endif /* PG_CRC_H */