357ffb3c46
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@17369 a1c6a512-1295-4272-9138-f99709370657
61 lines
2.3 KiB
C
61 lines
2.3 KiB
C
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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* $Id$
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*
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* Copyright (C) 2003 Jörg Hohensohn [IDC]Dragon
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*
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* All files in this archive are subject to the GNU General Public License.
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* See the file COPYING in the source tree root for full license agreement.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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/* Code copied from firmware_flash plugin. */
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#include "crc32.h"
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/* Tool function to calculate a CRC32 across some buffer */
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/* third argument is either 0xFFFFFFFF to start or value from last piece */
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unsigned crc_32(const void *src, unsigned len, unsigned crc32)
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{
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const unsigned char *buf = (const unsigned char *)src;
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/* CCITT standard polynomial 0x04C11DB7 */
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static const unsigned crc32_lookup[16] =
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{ /* lookup table for 4 bits at a time is affordable */
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0x00000000, 0x04C11DB7, 0x09823B6E, 0x0D4326D9,
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0x130476DC, 0x17C56B6B, 0x1A864DB2, 0x1E475005,
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0x2608EDB8, 0x22C9F00F, 0x2F8AD6D6, 0x2B4BCB61,
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0x350C9B64, 0x31CD86D3, 0x3C8EA00A, 0x384FBDBD
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};
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unsigned char byte;
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unsigned t;
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while (len--)
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{
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byte = *buf++; /* get one byte of data */
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/* upper nibble of our data */
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t = crc32 >> 28; /* extract the 4 most significant bits */
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t ^= byte >> 4; /* XOR in 4 bits of data into the extracted bits */
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crc32 <<= 4; /* shift the CRC register left 4 bits */
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crc32 ^= crc32_lookup[t]; /* do the table lookup and XOR the result */
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/* lower nibble of our data */
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t = crc32 >> 28; /* extract the 4 most significant bits */
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t ^= byte & 0x0F; /* XOR in 4 bits of data into the extracted bits */
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crc32 <<= 4; /* shift the CRC register left 4 bits */
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crc32 ^= crc32_lookup[t]; /* do the table lookup and XOR the result */
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}
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return crc32;
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}
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