// SPDX-License-Identifier: GPL-2.0
  /*
   * Normal 64-bit CRC calculation.
   *
   * This is a basic crc64 implementation following ECMA-182 specification,
   * which can be found from,

   * https://www.ecma-international.org/publications/standards/Ecma-182.htm

   *
   * Dr. Ross N. Williams has a great document to introduce the idea of CRC
   * algorithm, here the CRC64 code is also inspired by the table-driven
   * algorithm and detail example from this paper. This paper can be found
   * from,
   * http://www.ross.net/crc/download/crc_v3.txt
   *
   * crc64table[256] is the lookup table of a table-driven 64-bit CRC
   * calculation, which is generated by gen_crc64table.c in kernel build
   * time. The polynomial of crc64 arithmetic is from ECMA-182 specification
   * as well, which is defined as,
   *
   * x^64 + x^62 + x^57 + x^55 + x^54 + x^53 + x^52 + x^47 + x^46 + x^45 +
   * x^40 + x^39 + x^38 + x^37 + x^35 + x^33 + x^32 + x^31 + x^29 + x^27 +
   * x^24 + x^23 + x^22 + x^21 + x^19 + x^17 + x^13 + x^12 + x^10 + x^9 +
   * x^7 + x^4 + x + 1
   *
   * Copyright 2018 SUSE Linux.
   *   Author: Coly Li <colyli@suse.de>
   */
  
  #include <linux/module.h>
  #include <linux/types.h>

  #include <linux/crc64.h>

  #include "crc64table.h"
  
  MODULE_DESCRIPTION("CRC64 calculations");
  MODULE_LICENSE("GPL v2");
  
  /**
   * crc64_be - Calculate bitwise big-endian ECMA-182 CRC64
   * @crc: seed value for computation. 0 or (u64)~0 for a new CRC calculation,
  	or the previous crc64 value if computing incrementally.
   * @p: pointer to buffer over which CRC64 is run
   * @len: length of buffer @p
   */
  u64 __pure crc64_be(u64 crc, const void *p, size_t len)
  {
  	size_t i, t;
  
  	const unsigned char *_p = p;
  
  	for (i = 0; i < len; i++) {
  		t = ((crc >> 56) ^ (*_p++)) & 0xFF;
  		crc = crc64table[t] ^ (crc << 8);
  	}
  
  	return crc;
  }
  EXPORT_SYMBOL_GPL(crc64_be);