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