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Diffstat (limited to 'crc32c.c')
| -rw-r--r-- | crc32c.c | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/crc32c.c b/crc32c.c new file mode 100644 index 0000000..156cba1 --- /dev/null +++ b/crc32c.c @@ -0,0 +1,104 @@ +/* + * Oct 28, 2015 Song Liu simplified the code and port it to mdadm + * + * Aug 8, 2011 Bob Pearson with help from Joakim Tjernlund and George Spelvin + * cleaned up code to current version of sparse and added the slicing-by-8 + * algorithm to the closely similar existing slicing-by-4 algorithm. + * + * Oct 15, 2000 Matt Domsch <Matt_Domsch@dell.com> + * Nicer crc32 functions/docs submitted by linux@horizon.com. Thanks! + * Code was from the public domain, copyright abandoned. Code was + * subsequently included in the kernel, thus was re-licensed under the + * GNU GPL v2. + * + * Oct 12, 2000 Matt Domsch <Matt_Domsch@dell.com> + * Same crc32 function was used in 5 other places in the kernel. + * I made one version, and deleted the others. + * There are various incantations of crc32(). Some use a seed of 0 or ~0. + * Some xor at the end with ~0. The generic crc32() function takes + * seed as an argument, and doesn't xor at the end. Then individual + * users can do whatever they need. + * drivers/net/smc9194.c uses seed ~0, doesn't xor with ~0. + * fs/jffs2 uses seed 0, doesn't xor with ~0. + * fs/partitions/efi.c uses seed ~0, xor's with ~0. + * + * This source code is licensed under the GNU General Public License, + * Version 2. See the file COPYING for more details. + */ + +#include <sys/types.h> +#include <asm/types.h> +#include <stdlib.h> + +/* + * There are multiple 16-bit CRC polynomials in common use, but this is + * *the* standard CRC-32 polynomial, first popularized by Ethernet. + * x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x^1+x^0 + */ +#define CRCPOLY_LE 0xedb88320 +#define CRCPOLY_BE 0x04c11db7 + +/* + * This is the CRC32c polynomial, as outlined by Castagnoli. + * x^32+x^28+x^27+x^26+x^25+x^23+x^22+x^20+x^19+x^18+x^14+x^13+x^11+x^10+x^9+ + * x^8+x^6+x^0 + */ +#define CRC32C_POLY_LE 0x82F63B78 + +/** + * crc32_le_generic() - Calculate bitwise little-endian Ethernet AUTODIN II + * CRC32/CRC32C + * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for other + * uses, or the previous crc32/crc32c value if computing incrementally. + * @p: pointer to buffer over which CRC32/CRC32C is run + * @len: length of buffer @p + * @polynomial: CRC32/CRC32c LE polynomial + */ +static inline __u32 crc32_le_generic(__u32 crc, unsigned char const *p, + size_t len, __u32 polynomial) +{ + int i; + while (len--) { + crc ^= *p++; + for (i = 0; i < 8; i++) + crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0); + } + return crc; +} + +__u32 crc32_le(__u32 crc, unsigned char const *p, size_t len) +{ + return crc32_le_generic(crc, p, len, CRCPOLY_LE); +} + +__u32 crc32c_le(__u32 crc, unsigned char const *p, size_t len) +{ + return crc32_le_generic(crc, p, len, CRC32C_POLY_LE); +} + +/** + * crc32_be_generic() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32 + * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for + * other uses, or the previous crc32 value if computing incrementally. + * @p: pointer to buffer over which CRC32 is run + * @len: length of buffer @p + * @polynomial: CRC32 BE polynomial + */ +static inline __u32 crc32_be_generic(__u32 crc, unsigned char const *p, + size_t len, __u32 polynomial) +{ + int i; + while (len--) { + crc ^= *p++ << 24; + for (i = 0; i < 8; i++) + crc = + (crc << 1) ^ ((crc & 0x80000000) ? polynomial : + 0); + } + return crc; +} + +__u32 crc32_be(__u32 crc, unsigned char const *p, size_t len) +{ + return crc32_be_generic(crc, p, len, CRCPOLY_BE); +} |