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 static uint32_t crc32c_table [256];
   7
   8 static void
   9 init_crc32c_table (void)
  10 {
  11   auto uint32_t reflect (uint32_t ref, int len);
  12   uint32_t reflect (uint32_t ref, int len)
  13     {
  14       uint32_t result = 0;
  15       int i;
  16
  17       for (i = 1; i <= len; i++)
  18         {
  19           if (ref & 1)
  20             result |= 1 << (len - i);
  21           ref >>= 1;
  22         }
  23
  24       return result;
  25     }
  26
  27   static int crc32c_table_inited;
  28   if(crc32c_table_inited)
  29           return;
  30   crc32c_table_inited = 1;
  31
  32   uint32_t polynomial = 0x1edc6f41;
  33   int i, j;
  34
  35   for(i = 0; i < 256; i++)
  36     {
  37       crc32c_table[i] = reflect(i, 8) << 24;
  38       for (j = 0; j < 8; j++)
  39         crc32c_table[i] = (crc32c_table[i] << 1) ^
  40             (crc32c_table[i] & (1 << 31) ? polynomial : 0);
  41       crc32c_table[i] = reflect(crc32c_table[i], 32);
  42     }
  43 }
  44
  45 uint32_t
  46 grub_getcrc32c (uint32_t crc, const void *buf, int size)
  47 {
  48   int i;
  49   const uint8_t *data = buf;
  50
  51   if (! crc32c_table[1])
  52     init_crc32c_table ();
  53
  54   crc^= 0xffffffff;
  55
  56   for (i = 0; i < size; i++)
  57     {
  58       crc = (crc >> 8) ^ crc32c_table[(crc & 0xFF) ^ *data];
  59       data++;
  60     }
  61
  62   return crc ^ 0xffffffff;
  63 }