code.delx.au - refind/blob - filesystems/crc32c.c

   1 /*
   2  * this file take from grub 2.0
   3  * for btrfs UEFI driver
   4  */
   5 /*
   6  *  GRUB  --  GRand Unified Bootloader
   7  *  Copyright (C) 2008  Free Software Foundation, Inc.
   8  *
   9  *  GRUB is free software: you can redistribute it and/or modify
  10  *  it under the terms of the GNU General Public License as published by
  11  *  the Free Software Foundation, either version 3 of the License, or
  12  *  (at your option) any later version.
  13  *
  14  *  GRUB is distributed in the hope that it will be useful,
  15  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  *  GNU General Public License for more details.
  18  *
  19  *  You should have received a copy of the GNU General Public License
  20  *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
  21  */
  22
  23 static uint32_t crc32c_table [256];
  24
  25 static void
  26 init_crc32c_table (void)
  27 {
  28   auto uint32_t reflect (uint32_t ref, int len);
  29   uint32_t reflect (uint32_t ref, int len)
  30     {
  31       uint32_t result = 0;
  32       int i;
  33
  34       for (i = 1; i <= len; i++)
  35         {
  36           if (ref & 1)
  37             result |= 1 << (len - i);
  38           ref >>= 1;
  39         }
  40
  41       return result;
  42     }
  43
  44   static int crc32c_table_inited;
  45   if(crc32c_table_inited)
  46           return;
  47   crc32c_table_inited = 1;
  48
  49   uint32_t polynomial = 0x1edc6f41;
  50   int i, j;
  51
  52   for(i = 0; i < 256; i++)
  53     {
  54       crc32c_table[i] = reflect(i, 8) << 24;
  55       for (j = 0; j < 8; j++)
  56         crc32c_table[i] = (crc32c_table[i] << 1) ^
  57             (crc32c_table[i] & (1 << 31) ? polynomial : 0);
  58       crc32c_table[i] = reflect(crc32c_table[i], 32);
  59     }
  60 }
  61
  62 uint32_t
  63 grub_getcrc32c (uint32_t crc, const void *buf, int size)
  64 {
  65   int i;
  66   const uint8_t *data = buf;
  67
  68   if (! crc32c_table[1])
  69     init_crc32c_table ();
  70
  71   crc^= 0xffffffff;
  72
  73   for (i = 0; i < size; i++)
  74     {
  75       crc = (crc >> 8) ^ crc32c_table[(crc & 0xFF) ^ *data];
  76       data++;
  77     }
  78
  79   return crc ^ 0xffffffff;
  80 }