/*
* pg_crc.h
*
* PostgreSQL CRC support
*
* See Ross Williams' excellent introduction
* A PAINLESS GUIDE TO CRC ERROR DETECTION ALGORITHMS, available from
* http://www.ross.net/crc/ or several other net sites.
*
* We use a normal (not "reflected", in Williams' terms) CRC, using initial
* all-ones register contents and a final bit inversion.
*
* The 64-bit variant is not used as of PostgreSQL 8.1, but we retain the
* code for possible future use.
*
*
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/utils/pg_crc.h,v 1.21 2009/01/01 17:24:02 momjian Exp $
*/
#ifndef PG_CRC_H
#define PG_CRC_H
/* ugly hack to let this be used in frontend and backend code on Cygwin */
#ifdef FRONTEND
#define CRCDLLIMPORT
#else
#define CRCDLLIMPORT PGDLLIMPORT
#endif
typedef uint32 pg_crc32;
/* Initialize a CRC accumulator */
#define INIT_CRC32(crc) ((crc) = 0xFFFFFFFF)
/* Finish a CRC calculation */
#define FIN_CRC32(crc) ((crc) ^= 0xFFFFFFFF)
/* Accumulate some (more) bytes into a CRC */
#define COMP_CRC32(crc, data, len) \
do { \
unsigned char *__data = (unsigned char *) (data); \
uint32 __len = (len); \
\
while (__len-- > 0) \
{ \
int __tab_index = ((int) ((crc) >> 24) ^ *__data++) & 0xFF; \
(crc) = pg_crc32_table[__tab_index] ^ ((crc) << 8); \
} \
} while (0)
/* Check for equality of two CRCs */
#define EQ_CRC32(c1,c2) ((c1) == (c2))
/* Constant table for CRC calculation */
extern CRCDLLIMPORT const uint32 pg_crc32_table[];
#ifdef PROVIDE_64BIT_CRC
/*
* If we have a 64-bit integer type, then a 64-bit CRC looks just like the
* usual sort of implementation. If we have no working 64-bit type, then
* fake it with two 32-bit registers. (Note: experience has shown that the
* two-32-bit-registers code is as fast as, or even much faster than, the
* 64-bit code on all but true 64-bit machines. INT64_IS_BUSTED is therefore
* probably the wrong control symbol to use to select the implementation.)
*/
#ifdef INT64_IS_BUSTED
/*
* crc0 represents the LSBs of the 64-bit value, crc1 the MSBs. Note that
* with crc0 placed first, the output of 32-bit and 64-bit implementations
* will be bit-compatible only on little-endian architectures. If it were
* important to make the two possible implementations bit-compatible on
* all machines, we could do a configure test to decide how to order the
* two fields, but it seems not worth the trouble.
*/
typedef struct pg_crc64
{
uint32 crc0;
uint32 crc1;
} pg_crc64;
/* Initialize a CRC accumulator */
#define INIT_CRC64(crc) ((crc).crc0 = 0xffffffff, (crc).crc1 = 0xffffffff)
/* Finish a CRC calculation */
#define FIN_CRC64(crc) ((crc).crc0 ^= 0xffffffff, (crc).crc1 ^= 0xffffffff)
/* Accumulate some (more) bytes into a CRC */
#define COMP_CRC64(crc, data, len) \
do { \
uint32 __crc0 = (crc).crc0; \
uint32 __crc1 = (crc).crc1; \
unsigned char *__data = (unsigned char *) (data); \
uint32 __len = (len); \
\
while (__len-- > 0) \
{ \
int __tab_index = ((int) (__crc1 >> 24) ^ *__data++) & 0xFF; \
__crc1 = pg_crc64_table1[__tab_index] ^ ((__crc1 << 8) | (__crc0 >> 24)); \
__crc0 = pg_crc64_table0[__tab_index] ^ (__crc0 << 8); \
} \
(crc).crc0 = __crc0; \
(crc).crc1 = __crc1; \
} while (0)
/* Check for equality of two CRCs */
#define EQ_CRC64(c1,c2) ((c1).crc0 == (c2).crc0 && (c1).crc1 == (c2).crc1)
/* Constant table for CRC calculation */
extern CRCDLLIMPORT const uint32 pg_crc64_table0[];
extern CRCDLLIMPORT const uint32 pg_crc64_table1[];
#else /* int64 works */
typedef struct pg_crc64
{
uint64 crc0;
} pg_crc64;
/* Initialize a CRC accumulator */
#define INIT_CRC64(crc) ((crc).crc0 = UINT64CONST(0xffffffffffffffff))
/* Finish a CRC calculation */
#define FIN_CRC64(crc) ((crc).crc0 ^= UINT64CONST(0xffffffffffffffff))
/* Accumulate some (more) bytes into a CRC */
#define COMP_CRC64(crc, data, len) \
do { \
uint64 __crc0 = (crc).crc0; \
unsigned char *__data = (unsigned char *) (data); \
uint32 __len = (len); \
\
while (__len-- > 0) \
{ \
int __tab_index = ((int) (__crc0 >> 56) ^ *__data++) & 0xFF; \
__crc0 = pg_crc64_table[__tab_index] ^ (__crc0 << 8); \
} \
(crc).crc0 = __crc0; \
} while (0)
/* Check for equality of two CRCs */
#define EQ_CRC64(c1,c2) ((c1).crc0 == (c2).crc0)
/* Constant table for CRC calculation */
extern CRCDLLIMPORT const uint64 pg_crc64_table[];
#endif /* INT64_IS_BUSTED */
#endif /* PROVIDE_64BIT_CRC */
#endif /* PG_CRC_H */
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