crc32.c

该文件是rt_linux

/* 
 * Based on linux-2.5/lib/crc32 by Matt Domsch <[e-mail]>
 *
 * FIXME: Remove in 2.5  
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <asm/atomic.h>

#include "crc32.h"

#define CRCPOLY_BE 0x04c11db7
#define CRC_BE_BITS 8

static u32 *bnep_crc32_table;

/*
 * This code is in the public domain; copyright abandoned.
 * Liability for non-performance of this code is limited to the amount
 * you paid for it.  Since it is distributed for free, your refund will
 * be very very small.  If it breaks, you get to keep both pieces.
 */
u32 bnep_crc32(u32 crc, unsigned char const *p, size_t len)
{
	while (len--)
		crc = (crc << 8) ^ bnep_crc32_table[(crc >> 24) ^ *p++];
	
	return crc;
}

int __init bnep_crc32_init(void)
{
	unsigned i, j;
	u32 crc = 0x80000000;

	bnep_crc32_table = kmalloc((1 << CRC_BE_BITS) * sizeof(u32), GFP_KERNEL);
	if (!bnep_crc32_table)
		return -ENOMEM;

	bnep_crc32_table[0] = 0;

	for (i = 1; i < 1 << CRC_BE_BITS; i <<= 1) {
		crc = (crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE : 0);
		for (j = 0; j < i; j++)
			bnep_crc32_table[i + j] = crc ^ bnep_crc32_table[j];
	}
	return 0;
}

void __exit bnep_crc32_cleanup(void)
{
	if (bnep_crc32_table)
		kfree(bnep_crc32_table);
	bnep_crc32_table = NULL;
}