tinymodem::RSCodec Class Reference

Reed-Solomon code over GF(256) with the polynomial 0x11d and lengths which are defined at runtime. The generator roots are alpha^fcr to alpha^(fcr+ecc-1): fcr = 0 is used by ggwave (Mike Lubinets' library) and IL2P, fcr = 1 by FX.25. The parity bytes follow the message, the first byte is the highest power (like Phil Karn's library). More...

#include <ReedSolomon.h>

Classes
struct	Tables

Static Public Member Functions
static void	encode (const uint8_t *msg, int len, int ecc, uint8_t *out, int fcr=0)
static bool	decode (uint8_t *data, int len, int ecc, int fcr=0)
static int	correct (uint8_t *data, int len, int ecc, int fcr=0)

Static Public Attributes
static constexpr int	MAX_LEN = 255
	max length of message + parity
static constexpr int	MAX_ECC = 64

Static Protected Member Functions
static const Tables &	tables ()
static uint8_t	mul (uint8_t a, uint8_t b)
static uint8_t	div (uint8_t a, uint8_t b)
static uint8_t	pow2 (int power)
	alpha^power (power 0 - 255)
static uint8_t	powOf (uint8_t x, int power)
static uint8_t	eval (const uint8_t *poly, int n, uint8_t x)
	Evaluates a polynomial with ascending powers.
static void	generator (int ecc, uint8_t *gen, int fcr)
	Generator polynomial (descending powers) with ecc + 1 coefficients.
static bool	syndromes (const uint8_t *data, int n, int ecc, uint8_t *synd, int fcr)

Detailed Description

Reed-Solomon code over GF(256) with the polynomial 0x11d and lengths which are defined at runtime. The generator roots are alpha^fcr to alpha^(fcr+ecc-1): fcr = 0 is used by ggwave (Mike Lubinets' library) and IL2P, fcr = 1 by FX.25. The parity bytes follow the message, the first byte is the highest power (like Phil Karn's library).

Copyright

GPLv3

Member Function Documentation

correct()

int tinymodem::RSCodec::correct ( uint8_t * data, int len, int ecc, int fcr = 0 )

inlinestatic

Corrects up to ecc / 2 wrong bytes of the len + ecc bytes in place: returns the number of corrected bytes or -1 if the data can't be corrected

decode()

bool tinymodem::RSCodec::decode ( uint8_t * data, int len, int ecc, int fcr = 0 )

inlinestatic

Corrects up to ecc / 2 wrong bytes of the len + ecc bytes in place: returns false if the data can't be corrected

div()

uint8_t tinymodem::RSCodec::div ( uint8_t a, uint8_t b )

inlinestaticprotected

encode()

void tinymodem::RSCodec::encode ( const uint8_t * msg, int len, int ecc, uint8_t * out, int fcr = 0 )

inlinestatic

Writes the message followed by ecc parity bytes (at most MAX_ECC, len + ecc <= MAX_LEN) to out

eval()

uint8_t tinymodem::RSCodec::eval ( const uint8_t * poly, int n, uint8_t x )

inlinestaticprotected

Evaluates a polynomial with ascending powers.

generator()

void tinymodem::RSCodec::generator ( int ecc, uint8_t * gen, int fcr )

inlinestaticprotected

Generator polynomial (descending powers) with ecc + 1 coefficients.

mul()

uint8_t tinymodem::RSCodec::mul ( uint8_t a, uint8_t b )

inlinestaticprotected

pow2()

uint8_t tinymodem::RSCodec::pow2 ( int power )

inlinestaticprotected

alpha^power (power 0 - 255)

powOf()

uint8_t tinymodem::RSCodec::powOf ( uint8_t x, int power )

inlinestaticprotected

syndromes()

bool tinymodem::RSCodec::syndromes ( const uint8_t * data, int n, int ecc, uint8_t * synd, int fcr )

inlinestaticprotected

Calculates the syndromes (data[0] is the highest power): returns true if there are errors

tables()

const Tables & tinymodem::RSCodec::tables ( )

inlinestaticprotected

Member Data Documentation

MAX_ECC

int tinymodem::RSCodec::MAX_ECC = 64

staticconstexpr

max number of parity bytes (FX.25: 64, ggwave: 56): limits the stack usage

MAX_LEN

int tinymodem::RSCodec::MAX_LEN = 255

staticconstexpr

max length of message + parity

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The documentation for this class was generated from the following file:

• src/modem/ReedSolomon.h