LXR linux/lib/gen_crc64table.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Generate lookup table for the table-driven CRC64 calculation.
   4 *
   5 * gen_crc64table is executed in kernel build time and generates
   6 * lib/crc64table.h. This header is included by lib/crc64.c for
   7 * the table-driven CRC64 calculation.
   8 *
   9 * See lib/crc64.c for more information about which specification
  10 * and polynomial arithmetic that gen_crc64table.c follows to
  11 * generate the lookup table.
  12 *
  13 * Copyright 2018 SUSE Linux.
  14 *   Author: Coly Li <colyli@suse.de>
  15 */
  16#include <inttypes.h>
  17#include <stdio.h>
  18
  19#define CRC64_ECMA182_POLY 0x42F0E1EBA9EA3693ULL
  20
  21static uint64_t crc64_table[256] = {0};
  22
  23static void generate_crc64_table(void)
  24{
  25        uint64_t i, j, c, crc;
  26
  27        for (i = 0; i < 256; i++) {
  28                crc = 0;
  29                c = i << 56;
  30
  31                for (j = 0; j < 8; j++) {
  32                        if ((crc ^ c) & 0x8000000000000000ULL)
  33                                crc = (crc << 1) ^ CRC64_ECMA182_POLY;
  34                        else
  35                                crc <<= 1;
  36                        c <<= 1;
  37                }
  38
  39                crc64_table[i] = crc;
  40        }
  41}
  42
  43static void print_crc64_table(void)
  44{
  45        int i;
  46
  47        printf("/* this file is generated - do not edit */\n\n");
  48        printf("#include <linux/types.h>\n");
  49        printf("#include <linux/cache.h>\n\n");
  50        printf("static const u64 ____cacheline_aligned crc64table[256] = {\n");
  51        for (i = 0; i < 256; i++) {
  52                printf("\t0x%016" PRIx64 "ULL", crc64_table[i]);
  53                if (i & 0x1)
  54                        printf(",\n");
  55                else
  56                        printf(", ");
  57        }
  58        printf("};\n");
  59}
  60
  61int main(int argc, char *argv[])
  62{
  63        generate_crc64_table();
  64        print_crc64_table();
  65        return 0;
  66}
  67