oldpakerz/crc32.d

   1 /***********************************************************************
   2  * Coded by Ketmar // Invisible Vector
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  ***********************************************************************/
  18 module iv.oldpakerz.crc32 /*is aliced*/;
  19 import iv.alice;
  20
  21
  22 public uint wdx_crc32 (const(void)[] buf, uint crc=0) pure nothrow @trusted @nogc {
  23   /*
  24   static immutable uint[16] crctab = [
  25     0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
  26     0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
  27     0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
  28     0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c,
  29   ];
  30   */
  31   static immutable uint[16] crctab = {
  32     uint[16] res = void;
  33     // make exclusive-or pattern from polynomial (0xedb88320u)
  34     // terms of polynomial defining this crc (except x^32)
  35     //uint poly = 0; // polynomial exclusive-or pattern
  36     //foreach (immutable n; [0,1,2,4,5,7,8,10,11,12,16,22,23,26]) poly |= 1u<<(31-n);
  37     enum poly = 0xedb88320u;
  38     foreach (immutable n; 0..16) {
  39       uint c = cast(uint)n*16;
  40       foreach (immutable k; 0..8) c = (c&1 ? poly^(c>>1) : c>>1);
  41       res[n] = c;
  42     }
  43     return res;
  44   }();
  45
  46   if (buf.length) {
  47     crc ^= 0xffff_ffffu;
  48     foreach (ubyte b; cast(const(ubyte)[])buf) {
  49       crc ^= b;
  50       crc = crctab.ptr[crc&0x0f]^(crc>>4);
  51       crc = crctab.ptr[crc&0x0f]^(crc>>4);
  52     }
  53     crc ^= 0xffff_ffffu;
  54   }
  55   return crc;
  56 }