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blue-lemon0104
152
pg_include/utils/pg_crc.h
Executable file
152
pg_include/utils/pg_crc.h
Executable file
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/*
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* pg_crc.h
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*
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* PostgreSQL CRC support
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*
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* See Ross Williams' excellent introduction
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* A PAINLESS GUIDE TO CRC ERROR DETECTION ALGORITHMS, available from
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* http://www.ross.net/crc/ or several other net sites.
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*
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* We use a normal (not "reflected", in Williams' terms) CRC, using initial
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* all-ones register contents and a final bit inversion.
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*
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* The 64-bit variant is not used as of PostgreSQL 8.1, but we retain the
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* code for possible future use.
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*
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*
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* Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/utils/pg_crc.h
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*/
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#ifndef PG_CRC_H
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#define PG_CRC_H
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/* ugly hack to let this be used in frontend and backend code on Cygwin */
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#ifdef FRONTEND
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#define CRCDLLIMPORT
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#else
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#define CRCDLLIMPORT PGDLLIMPORT
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#endif
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typedef uint32 pg_crc32;
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/* Initialize a CRC accumulator */
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#define INIT_CRC32(crc) ((crc) = 0xFFFFFFFF)
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/* Finish a CRC calculation */
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#define FIN_CRC32(crc) ((crc) ^= 0xFFFFFFFF)
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/* Accumulate some (more) bytes into a CRC */
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#define COMP_CRC32(crc, data, len) \
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do { \
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const unsigned char *__data = (const unsigned char *) (data); \
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uint32 __len = (len); \
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\
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while (__len-- > 0) \
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{ \
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int __tab_index = ((int) ((crc) >> 24) ^ *__data++) & 0xFF; \
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(crc) = pg_crc32_table[__tab_index] ^ ((crc) << 8); \
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} \
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} while (0)
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/* Check for equality of two CRCs */
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#define EQ_CRC32(c1,c2) ((c1) == (c2))
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/* Constant table for CRC calculation */
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extern CRCDLLIMPORT const uint32 pg_crc32_table[];
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#ifdef PROVIDE_64BIT_CRC
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/*
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* If we use a 64-bit integer type, then a 64-bit CRC looks just like the
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* usual sort of implementation. However, we can also fake it with two
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* 32-bit registers. Experience has shown that the two-32-bit-registers code
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* is as fast as, or even much faster than, the 64-bit code on all but true
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* 64-bit machines. We use SIZEOF_VOID_P to check the native word width.
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*/
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#if SIZEOF_VOID_P < 8
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/*
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* crc0 represents the LSBs of the 64-bit value, crc1 the MSBs. Note that
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* with crc0 placed first, the output of 32-bit and 64-bit implementations
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* will be bit-compatible only on little-endian architectures. If it were
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* important to make the two possible implementations bit-compatible on
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* all machines, we could do a configure test to decide how to order the
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* two fields, but it seems not worth the trouble.
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*/
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typedef struct pg_crc64
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{
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uint32 crc0;
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uint32 crc1;
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} pg_crc64;
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/* Initialize a CRC accumulator */
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#define INIT_CRC64(crc) ((crc).crc0 = 0xffffffff, (crc).crc1 = 0xffffffff)
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/* Finish a CRC calculation */
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#define FIN_CRC64(crc) ((crc).crc0 ^= 0xffffffff, (crc).crc1 ^= 0xffffffff)
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/* Accumulate some (more) bytes into a CRC */
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#define COMP_CRC64(crc, data, len) \
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do { \
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uint32 __crc0 = (crc).crc0; \
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uint32 __crc1 = (crc).crc1; \
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unsigned char *__data = (unsigned char *) (data); \
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uint32 __len = (len); \
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\
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while (__len-- > 0) \
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{ \
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int __tab_index = ((int) (__crc1 >> 24) ^ *__data++) & 0xFF; \
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__crc1 = pg_crc64_table1[__tab_index] ^ ((__crc1 << 8) | (__crc0 >> 24)); \
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__crc0 = pg_crc64_table0[__tab_index] ^ (__crc0 << 8); \
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} \
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(crc).crc0 = __crc0; \
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(crc).crc1 = __crc1; \
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} while (0)
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/* Check for equality of two CRCs */
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#define EQ_CRC64(c1,c2) ((c1).crc0 == (c2).crc0 && (c1).crc1 == (c2).crc1)
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/* Constant table for CRC calculation */
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extern CRCDLLIMPORT const uint32 pg_crc64_table0[];
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extern CRCDLLIMPORT const uint32 pg_crc64_table1[];
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#else /* use int64 implementation */
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typedef struct pg_crc64
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{
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uint64 crc0;
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} pg_crc64;
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/* Initialize a CRC accumulator */
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#define INIT_CRC64(crc) ((crc).crc0 = UINT64CONST(0xffffffffffffffff))
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/* Finish a CRC calculation */
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#define FIN_CRC64(crc) ((crc).crc0 ^= UINT64CONST(0xffffffffffffffff))
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/* Accumulate some (more) bytes into a CRC */
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#define COMP_CRC64(crc, data, len) \
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do { \
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uint64 __crc0 = (crc).crc0; \
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unsigned char *__data = (unsigned char *) (data); \
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uint32 __len = (len); \
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\
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while (__len-- > 0) \
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{ \
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int __tab_index = ((int) (__crc0 >> 56) ^ *__data++) & 0xFF; \
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__crc0 = pg_crc64_table[__tab_index] ^ (__crc0 << 8); \
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} \
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(crc).crc0 = __crc0; \
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} while (0)
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/* Check for equality of two CRCs */
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#define EQ_CRC64(c1,c2) ((c1).crc0 == (c2).crc0)
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/* Constant table for CRC calculation */
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extern CRCDLLIMPORT const uint64 pg_crc64_table[];
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#endif /* SIZEOF_VOID_P < 8 */
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#endif /* PROVIDE_64BIT_CRC */
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#endif /* PG_CRC_H */
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