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Edit File: pg_crc.h

/* * 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) 1996-2012, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * src/include/utils/pg_crc.h */ #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 { \ const unsigned char *__data = (const 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 use a 64-bit integer type, then a 64-bit CRC looks just like the * usual sort of implementation. However, we can also fake it with two * 32-bit registers. 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. We use SIZEOF_VOID_P to check the native word width. */ #if SIZEOF_VOID_P < 8 /* * 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 /* use int64 implementation */ 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 /* SIZEOF_VOID_P < 8 */ #endif /* PROVIDE_64BIT_CRC */ #endif /* PG_CRC_H */