firmware/common/crc32.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2003 Jörg Hohensohn [IDC]Dragon
  11  *
  12  * All files in this archive are subject to the GNU General Public License.
  13  * See the file COPYING in the source tree root for full license agreement.
  14  *
  15  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  16  * KIND, either express or implied.
  17  *
  18  ****************************************************************************/
  19
  20 /* Code copied from firmware_flash plugin. */
  21
  22 /* Tool function to calculate a CRC32 across some buffer */
  23 /* third argument is either 0xFFFFFFFF to start or value from last piece */
  24 unsigned crc_32(const void *src, unsigned len, unsigned crc32)
  25 {
  26     const unsigned char *buf = (const unsigned char *)src;
  27
  28     /* CCITT standard polynomial 0x04C11DB7 */
  29     static const unsigned crc32_lookup[16] =
  30     {   /* lookup table for 4 bits at a time is affordable */
  31         0x00000000, 0x04C11DB7, 0x09823B6E, 0x0D4326D9,
  32         0x130476DC, 0x17C56B6B, 0x1A864DB2, 0x1E475005,
  33         0x2608EDB8, 0x22C9F00F, 0x2F8AD6D6, 0x2B4BCB61,
  34         0x350C9B64, 0x31CD86D3, 0x3C8EA00A, 0x384FBDBD
  35     };
  36
  37     unsigned char byte;
  38     unsigned t;
  39
  40     while (len--)
  41     {
  42         byte = *buf++; /* get one byte of data */
  43
  44         /* upper nibble of our data */
  45         t = crc32 >> 28; /* extract the 4 most significant bits */
  46         t ^= byte >> 4; /* XOR in 4 bits of data into the extracted bits */
  47         crc32 <<= 4; /* shift the CRC register left 4 bits */
  48         crc32 ^= crc32_lookup[t]; /* do the table lookup and XOR the result */
  49
  50         /* lower nibble of our data */
  51         t = crc32 >> 28; /* extract the 4 most significant bits */
  52         t ^= byte & 0x0F; /* XOR in 4 bits of data into the extracted bits */
  53         crc32 <<= 4; /* shift the CRC register left 4 bits */
  54         crc32 ^= crc32_lookup[t]; /* do the table lookup and XOR the result */
  55     }
  56
  57     return crc32;
  58 }
  59