mirror of https://gitee.com/openkylin/linux.git
58 lines
1.8 KiB
C
58 lines
1.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Normal 64-bit CRC calculation.
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*
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* This is a basic crc64 implementation following ECMA-182 specification,
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* which can be found from,
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* https://www.ecma-international.org/publications/standards/Ecma-182.htm
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*
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* Dr. Ross N. Williams has a great document to introduce the idea of CRC
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* algorithm, here the CRC64 code is also inspired by the table-driven
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* algorithm and detail example from this paper. This paper can be found
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* from,
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* http://www.ross.net/crc/download/crc_v3.txt
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*
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* crc64table[256] is the lookup table of a table-driven 64-bit CRC
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* calculation, which is generated by gen_crc64table.c in kernel build
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* time. The polynomial of crc64 arithmetic is from ECMA-182 specification
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* as well, which is defined as,
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*
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* x^64 + x^62 + x^57 + x^55 + x^54 + x^53 + x^52 + x^47 + x^46 + x^45 +
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* x^40 + x^39 + x^38 + x^37 + x^35 + x^33 + x^32 + x^31 + x^29 + x^27 +
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* x^24 + x^23 + x^22 + x^21 + x^19 + x^17 + x^13 + x^12 + x^10 + x^9 +
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* x^7 + x^4 + x + 1
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*
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* Copyright 2018 SUSE Linux.
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* Author: Coly Li <colyli@suse.de>
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*/
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/crc64.h>
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#include "crc64table.h"
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MODULE_DESCRIPTION("CRC64 calculations");
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MODULE_LICENSE("GPL v2");
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/**
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* crc64_be - Calculate bitwise big-endian ECMA-182 CRC64
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* @crc: seed value for computation. 0 or (u64)~0 for a new CRC calculation,
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* or the previous crc64 value if computing incrementally.
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* @p: pointer to buffer over which CRC64 is run
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* @len: length of buffer @p
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*/
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u64 __pure crc64_be(u64 crc, const void *p, size_t len)
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{
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size_t i, t;
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const unsigned char *_p = p;
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for (i = 0; i < len; i++) {
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t = ((crc >> 56) ^ (*_p++)) & 0xFF;
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crc = crc64table[t] ^ (crc << 8);
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}
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return crc;
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}
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EXPORT_SYMBOL_GPL(crc64_be);
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