crc.c

来自「关于ＡＣ３的解码程序」· C语言 代码 · 共 83 行

/*
* This source code is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*       
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*
* File Name: crc.c							
*
* Reference:
*
* Author:                                               
*
* Description:
*
* 	
* 
* History:
* 02/23/2005  
*  
*
*CodeReview Log:
* 
*/
#include <stdlib.h>
#include <stdio.h>
#include "ac3.h"
#include "crc.h"

uint_16 state;

static void crc_process_bit(uint_32 bit);

void
crc_init(void)
{
	state = 0;
}

static void
crc_process_bit(uint_32 bit)
{
	uint_32 xor_val;

	xor_val = (state >> 15) ^ bit;

	state <<= 1;
	
	if(xor_val)
		state = (state ^ 0x8005);
}


void
crc_process(uint_32 data, uint_32 num_bits)
{
	data <<= 32 - num_bits;

	while(num_bits)
	{
		crc_process_bit(data >> 31);

		data <<= 1;
		num_bits--;
	}
}

int
crc_validate(void)
{
	return(state == 0);
}