1 /*------------------------------------------------------------------------- 2 * 3 * pg_crc32c.h 4 * Routines for computing CRC-32C checksums. 5 * 6 * The speed of CRC-32C calculation has a big impact on performance, so we 7 * jump through some hoops to get the best implementation for each 8 * platform. Some CPU architectures have special instructions for speeding 9 * up CRC calculations (e.g. Intel SSE 4.2), on other platforms we use the 10 * Slicing-by-8 algorithm which uses lookup tables. 11 * 12 * The public interface consists of four macros: 13 * 14 * INIT_CRC32C(crc) 15 * Initialize a CRC accumulator 16 * 17 * COMP_CRC32C(crc, data, len) 18 * Accumulate some (more) bytes into a CRC 19 * 20 * FIN_CRC32C(crc) 21 * Finish a CRC calculation 22 * 23 * EQ_CRC32C(c1, c2) 24 * Check for equality of two CRCs. 25 * 26 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group 27 * Portions Copyright (c) 1994, Regents of the University of California 28 * 29 * src/include/port/pg_crc32c.h 30 * 31 *------------------------------------------------------------------------- 32 */ 33 #ifndef PG_CRC32C_H 34 #define PG_CRC32C_H 35 36 #include "port/pg_bswap.h" 37 38 typedef uint32 pg_crc32c; 39 40 /* The INIT and EQ macros are the same for all implementations. */ 41 #define INIT_CRC32C(crc) ((crc) = 0xFFFFFFFF) 42 #define EQ_CRC32C(c1, c2) ((c1) == (c2)) 43 44 #if defined(USE_SSE42_CRC32C) 45 /* Use SSE4.2 instructions. */ 46 #define COMP_CRC32C(crc, data, len) \ 47 ((crc) = pg_comp_crc32c_sse42((crc), (data), (len))) 48 #define FIN_CRC32C(crc) ((crc) ^= 0xFFFFFFFF) 49 50 extern pg_crc32c pg_comp_crc32c_sse42(pg_crc32c crc, const void *data, size_t len); 51 52 #elif defined(USE_SSE42_CRC32C_WITH_RUNTIME_CHECK) 53 /* 54 * Use SSE4.2 instructions, but perform a runtime check first to check that 55 * they are available. 56 */ 57 #define COMP_CRC32C(crc, data, len) \ 58 ((crc) = pg_comp_crc32c((crc), (data), (len))) 59 #define FIN_CRC32C(crc) ((crc) ^= 0xFFFFFFFF) 60 61 extern pg_crc32c pg_comp_crc32c_sse42(pg_crc32c crc, const void *data, size_t len); 62 extern pg_crc32c pg_comp_crc32c_sb8(pg_crc32c crc, const void *data, size_t len); 63 extern pg_crc32c (*pg_comp_crc32c) (pg_crc32c crc, const void *data, size_t len); 64 65 #else 66 /* 67 * Use slicing-by-8 algorithm. 68 * 69 * On big-endian systems, the intermediate value is kept in reverse byte 70 * order, to avoid byte-swapping during the calculation. FIN_CRC32C reverses 71 * the bytes to the final order. 72 */ 73 #define COMP_CRC32C(crc, data, len) \ 74 ((crc) = pg_comp_crc32c_sb8((crc), (data), (len))) 75 #ifdef WORDS_BIGENDIAN 76 #define FIN_CRC32C(crc) ((crc) = BSWAP32(crc) ^ 0xFFFFFFFF) 77 #else 78 #define FIN_CRC32C(crc) ((crc) ^= 0xFFFFFFFF) 79 #endif 80 81 extern pg_crc32c pg_comp_crc32c_sb8(pg_crc32c crc, const void *data, size_t len); 82 83 #endif 84 85 #endif /* PG_CRC32C_H */ 86