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/*
* Copyright (c) International Business Machines Corp., 2006
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
* the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* Author: Thomas Gleixner
*/
/*
* CRC32 functions
*
* Can be compiled as seperate object, but is included into the ipl source
* so gcc can inline the functions. We optimize for size so the omission of
* the function frame is helpful.
*
*/
#include <stdint.h>
#include <crc32.h>
/* CRC polynomial */
#define CRC_POLY 0xEDB88320
/**
* init_crc32_table - Initialize crc table
*
* @table: pointer to the CRC table which must be initialized
*
* Create CRC32 table for given polynomial. The table is created with
* the lowest order term in the highest order bit. So the x^32 term
* has to implied in the crc calculation function.
*/
void init_crc32_table(uint32_t *table)
{
uint32_t crc;
int i, j;
for (i = 0; i < 256; i++) {
crc = i;
for (j = 8; j > 0; j--) {
if (crc & 1)
crc = (crc >> 1) ^ CRC_POLY;
else
crc >>= 1;
}
table[i] = crc;
}
}
/**
* clc_crc32 - Calculate CRC32 over a buffer
*
* @table: pointer to the CRC table
* @crc: initial crc value
* @buf: pointer to the buffer
* @len: number of bytes to calc
*
* Returns the updated crc value.
*
* The algorithm resembles a hardware shift register, but calculates 8
* bit at once.
*/
uint32_t clc_crc32(uint32_t *table, uint32_t crc, void *buf,
int len)
{
const unsigned char *p = buf;
while(--len >= 0)
crc = table[(crc ^ *p++) & 0xff] ^ (crc >> 8);
return crc;
}
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