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115 lines
3.5 KiB
C
115 lines
3.5 KiB
C
/*
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* pg_crc.h
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*
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* PostgreSQL 64-bit CRC support
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*
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* Portions Copyright (c) 1996-2003, 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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* $PostgreSQL: pgsql/src/include/utils/pg_crc.h,v 1.10 2003/11/29 22:41:16 pgsql Exp $
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*/
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#ifndef PG_CRC_H
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#define PG_CRC_H
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/*
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* If we have a 64-bit integer type, then a 64-bit CRC looks just like the
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* usual sort of implementation. (See Ross Williams' excellent introduction
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* A PAINLESS GUIDE TO CRC ERROR DETECTION ALGORITHMS, available from
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* ftp://ftp.rocksoft.com/papers/crc_v3.txt or several other net sites.)
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* If we have no working 64-bit type, then fake it with two 32-bit registers.
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*
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* The present implementation is a normal (not "reflected", in Williams'
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* terms) 64-bit CRC, using initial all-ones register contents and a final
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* bit inversion. The chosen polynomial is borrowed from the DLT1 spec
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* (ECMA-182, available from http://www.ecma.ch/ecma1/STAND/ECMA-182.HTM):
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*
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* x^64 + x^62 + x^57 + x^55 + x^54 + x^53 + x^52 + x^47 + x^46 + x^45 +
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* x^40 + x^39 + x^38 + x^37 + x^35 + x^33 + x^32 + x^31 + x^29 + x^27 +
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* x^24 + x^23 + x^22 + x^21 + x^19 + x^17 + x^13 + x^12 + x^10 + x^9 +
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* x^7 + x^4 + x + 1
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*/
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#ifdef INT64_IS_BUSTED
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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 crc64
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{
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uint32 crc0;
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uint32 crc1;
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} 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 = crc_table1[__tab_index] ^ ((__crc1 << 8) | (__crc0 >> 24)); \
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__crc0 = crc_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 const uint32 crc_table0[];
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extern const uint32 crc_table1[];
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#else /* int64 works */
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typedef struct crc64
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{
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uint64 crc0;
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} 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 = crc_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 const uint64 crc_table[];
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#endif /* INT64_IS_BUSTED */
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#endif /* PG_CRC_H */
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