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  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  18  * KIND, either express or implied.
  19  *
  20  ****************************************************************************/
  21
  22 /* Code copied from firmware_flash plugin. */
  23
  24 #include "crc32.h"
  25
  26 /* Tool function to calculate a CRC32 across some buffer */
  27 /* third argument is either 0xFFFFFFFF to start or value from last piece */
  28 unsigned crc_32(const void *src, unsigned len, unsigned crc32)
  29 {
  30     const unsigned char *buf = (const unsigned char *)src;
  31
  32     /* CCITT standard polynomial 0x04C11DB7 */
  33     static const unsigned crc32_lookup[16] =
  34     {   /* lookup table for 4 bits at a time is affordable */
  35         0x00000000, 0x04C11DB7, 0x09823B6E, 0x0D4326D9,
  36         0x130476DC, 0x17C56B6B, 0x1A864DB2, 0x1E475005,
  37         0x2608EDB8, 0x22C9F00F, 0x2F8AD6D6, 0x2B4BCB61,
  38         0x350C9B64, 0x31CD86D3, 0x3C8EA00A, 0x384FBDBD
  39     };
  40
  41     unsigned char byte;
  42     unsigned t;
  43
  44     while (len--)
  45     {
  46         byte = *buf++; /* get one byte of data */
  47
  48         /* upper nibble of our data */
  49         t = crc32 >> 28; /* extract the 4 most significant bits */
  50         t ^= byte >> 4; /* XOR in 4 bits of data into the extracted bits */
  51         crc32 <<= 4; /* shift the CRC register left 4 bits */
  52         crc32 ^= crc32_lookup[t]; /* do the table lookup and XOR the result */
  53
  54         /* lower nibble of our data */
  55         t = crc32 >> 28; /* extract the 4 most significant bits */
  56         t ^= byte & 0x0F; /* XOR in 4 bits of data into the extracted bits */
  57         crc32 <<= 4; /* shift the CRC register left 4 bits */
  58         crc32 ^= crc32_lookup[t]; /* do the table lookup and XOR the result */
  59     }
  60
  61     return crc32;
  62 }
  63