codekingpro/portable-devtools

1/*2 * pg_crc.h3 *4 * PostgreSQL CRC support5 *6 * See Ross Williams' excellent introduction7 * A PAINLESS GUIDE TO CRC ERROR DETECTION ALGORITHMS, available from8 * http://ross.net/crc/ or several other net sites.9 *10 * We have three slightly different variants of a 32-bit CRC calculation:11 * CRC-32C (Castagnoli polynomial), CRC-32 (Ethernet polynomial), and a legacy12 * CRC-32 version that uses the lookup table in a funny way. They all consist13 * of four macros:14 *15 * INIT_<variant>(crc)16 *		Initialize a CRC accumulator17 *18 * COMP_<variant>(crc, data, len)19 *		Accumulate some (more) bytes into a CRC20 *21 * FIN_<variant>(crc)22 *		Finish a CRC calculation23 *24 * EQ_<variant>(c1, c2)25 *		Check for equality of two CRCs.26 *27 * The CRC-32C variant is in port/pg_crc32c.h.28 *29 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group30 * Portions Copyright (c) 1994, Regents of the University of California31 *32 * src/include/utils/pg_crc.h33 */34#ifndef PG_CRC_H35#define PG_CRC_H36 37typedef uint32 pg_crc32;38 39/*40 * CRC-32, the same used e.g. in Ethernet.41 *42 * This is currently only used in ltree and hstore contrib modules. It uses43 * the same lookup table as the legacy algorithm below. New code should44 * use the Castagnoli version instead.45 */46#define INIT_TRADITIONAL_CRC32(crc) ((crc) = 0xFFFFFFFF)47#define FIN_TRADITIONAL_CRC32(crc)	((crc) ^= 0xFFFFFFFF)48#define COMP_TRADITIONAL_CRC32(crc, data, len)	\49	COMP_CRC32_NORMAL_TABLE(crc, data, len, pg_crc32_table)50#define EQ_TRADITIONAL_CRC32(c1, c2) ((c1) == (c2))51 52/* Sarwate's algorithm, for use with a "normal" lookup table */53#define COMP_CRC32_NORMAL_TABLE(crc, data, len, table)			  \54do {															  \55	const unsigned char *__data = (const unsigned char *) (data); \56	uint32		__len = (len); \57\58	while (__len-- > 0) \59	{ \60		int		__tab_index = ((int) (crc) ^ *__data++) & 0xFF; \61		(crc) = table[__tab_index] ^ ((crc) >> 8); \62	} \63} while (0)64 65/*66 * The CRC algorithm used for WAL et al in pre-9.5 versions.67 *68 * This closely resembles the normal CRC-32 algorithm, but is subtly69 * different. Using Williams' terms, we use the "normal" table, but with70 * "reflected" code. That's bogus, but it was like that for years before71 * anyone noticed. It does not correspond to any polynomial in a normal CRC72 * algorithm, so it's not clear what the error-detection properties of this73 * algorithm actually are.74 *75 * We still need to carry this around because it is used in a few on-disk76 * structures that need to be pg_upgradeable. It should not be used in new77 * code.78 */79#define INIT_LEGACY_CRC32(crc) ((crc) = 0xFFFFFFFF)80#define FIN_LEGACY_CRC32(crc)	((crc) ^= 0xFFFFFFFF)81#define COMP_LEGACY_CRC32(crc, data, len)	\82	COMP_CRC32_REFLECTED_TABLE(crc, data, len, pg_crc32_table)83#define EQ_LEGACY_CRC32(c1, c2) ((c1) == (c2))84 85/*86 * Sarwate's algorithm, for use with a "reflected" lookup table (but in the87 * legacy algorithm, we actually use it on a "normal" table, see above)88 */89#define COMP_CRC32_REFLECTED_TABLE(crc, data, len, table) \90do {															  \91	const unsigned char *__data = (const unsigned char *) (data); \92	uint32		__len = (len); \93\94	while (__len-- > 0) \95	{ \96		int		__tab_index = ((int) ((crc) >> 24) ^ *__data++) & 0xFF; \97		(crc) = table[__tab_index] ^ ((crc) << 8); \98	} \99} while (0)100 101/*102 * Constant table for the CRC-32 polynomials. The same table is used by both103 * the normal and traditional variants.104 */105extern PGDLLIMPORT const uint32 pg_crc32_table[256];106 107#endif							/* PG_CRC_H */108