example.c

无线通讯中使用的一种揪错算法,rs 1.0 揪错能力可配置 能纠正 (冗余长度)/2-1 个错误

/* Example use of Reed-Solomon library 
 *
 * (C) Universal Access Inc. 1996
 *
 * This same code demonstrates the use of the encodier and 
 * decoder/error-correction routines. 
 *
 * We are assuming we have at least four bytes of parity (NPAR >= 4).
 * 
 * This gives us the ability to correct up to two errors, or 
 * four erasures. 
 *
 * In general, with E errors, and K erasures, you will need
 * 2E + K bytes of parity to be able to correct the codeword
 * back to recover the original message data.
 *
 * You could say that each error 'consumes' two bytes of the parity,
 * whereas each erasure 'consumes' one byte.
 *
 * Thus, as demonstrated below, we can inject one error (location unknown)
 * and two erasures (with their locations specified) and the 
 * error-correction routine will be able to correct the codeword
 * back to the original message.
 * */
 
#include <stdio.h>
#include <stdlib.h>
#include "ecc.h"
 
unsigned char msg[20] ;
unsigned char codeword[256];
 
int main ( )
{
	int erasures[16];
	int nerasures = 0;
	/* Initialization the ECC library */

	initialize_ecc ();

	/* ************** */

	/* Encode data into codeword, adding NPAR parity bytes */
	memcpy(msg,"\01\02\03x123 hj\10\xfa\0??",16);
	encode_data(msg, 15, codeword);
	printf("Encoded data is: \"%s\"\n", codeword);

#define ML (sizeof (msg) + NPAR)

	codeword[0]=0;
	codeword[1]=0;
	codeword[7]=0;
	codeword[8]=0;
	codeword[9]=0;
	codeword[13]=0;

	printf("with some errors: \"%s\"\n", codeword);

	/* We need to indicate the position of the erasures.	Eraseure
		 positions are indexed (1 based) from the end of the message... */

	erasures[nerasures++] = ML-17;
	erasures[nerasures++] = ML-19;

	/* Now decode -- encoded codeword size must be passed */
	decode_data(codeword, ML);

	/* check if syndrome is all zeros */
	if (check_syndrome () != 0) {
		correct_errors_erasures (codeword, ML, nerasures, erasures);
		printf("Corrected codeword: \"%s\"\n", codeword);
	}
	exit(0);
}