Functions used to compute the Reed-Solomon parity and check of byte arrays. More...

#include <stdio.h>
#include <stdlib.h>
#include "rs.h"

Macros
#define	B0 0
#define	A0 (NN)
#define	CLEAR(a, n)
#define	COPY(a, b, n)
#define	COPYDOWN(a, b, n)

Typedefs
typedef int	gf
	Reed-Solomon coding and decoding Phil Karn (karn@.nosp@m.ka9q.nosp@m..ampr.nosp@m..org) September 1996.

Functions
static gf	modnn (int x)
void	init_rs (int k)
	Initialization function.
void	generate_gf (void)
	These two functions must be called in this order (e.g., by init_rs()) before any encoding/decoding.
void	gen_poly (void)
int	encode_rs (dtype data, dtype bb)
int	eras_dec_rs (dtype data, int eras_pos, int no_eras)

Variables
static int	KK
int	Pp [MM+1] = { 1, 0, 1, 1, 1, 0, 0, 0, 1 }
gf	Alpha_to [NN+1]
gf	Index_of [NN+1]
gf	Gg [NN - 1]

Detailed Description

Functions used to compute the Reed-Solomon parity and check of byte arrays.

Macro Definition Documentation

◆ A0

#define A0 (NN)

Referenced by encode_rs(), eras_dec_rs(), and generate_gf().

◆ B0

#define B0 0

Referenced by eras_dec_rs(), and gen_poly().

◆ CLEAR

#define CLEAR	(		a,
			n )

Value:

{\
int ci;\
for(ci=(n)-1;ci >=0;ci--)\
        (a)[ci] = 0;\
}

Referenced by encode_rs(), and eras_dec_rs().

◆ COPY

#define COPY	(	a,
		b,
		n )

Value:

{\
int ci;\
for(ci=(n)-1;ci >=0;ci--)\
        (a)[ci] = (b)[ci];\
}

Referenced by eras_dec_rs().

◆ COPYDOWN

#define COPYDOWN	(	a,
		b,
		n )

Value:

{\
int ci;\
for(ci=(n)-1;ci >=0;ci--)\
        (a)[ci] = (b)[ci];\
}

Referenced by eras_dec_rs().

Typedef Documentation

◆ gf

typedef int gf

Reed-Solomon coding and decoding Phil Karn (karn@.nosp@m.ka9q.nosp@m..ampr.nosp@m..org) September 1996.

This file is derived from the program "new_rs_erasures.c" by Robert Morelos-Zaragoza (rober.nosp@m.t@sp.nosp@m.ectra.nosp@m..eng.nosp@m..hawa.nosp@m.ii.e.nosp@m.du) and Hari Thirumoorthy (harit.nosp@m.@spe.nosp@m.ctra..nosp@m.eng..nosp@m.hawai.nosp@m.i.ed.nosp@m.u), Aug 1995

I've made changes to improve performance, clean up the code and make it easier to follow. Data is now passed to the encoding and decoding functions through arguments rather than in global arrays. The decode function returns the number of corrected symbols, or -1 if the word is uncorrectable.

This code supports a symbol size from 2 bits up to 16 bits, implying a block size of 3 2-bit symbols (6 bits) up to 65535 16-bit symbols (1,048,560 bits). The code parameters are set in rs.h.

Note that if symbols larger than 8 bits are used, the type of each data array element switches from unsigned char to unsigned int. The caller must ensure that elements larger than the symbol range are not passed to the encoder or decoder.