Class ReedSolomonDecoder

java.lang.Object

com.google.zxing.common.reedsolomon.ReedSolomonDecoder

public final class ReedSolomonDecoder
extends Object

Implements Reed-Solomon decoding, as the name implies.

The algorithm will not be explained here, but the following references were helpful in creating this implementation:

• Bruce Maggs. "Decoding Reed-Solomon Codes" (see discussion of Forney's Formula)
• J.I. Hall. "Chapter 5. Generalized Reed-Solomon Codes" (see discussion of Euclidean algorithm)

Much credit is due to William Rucklidge since portions of this code are an indirect port of his C++ Reed-Solomon implementation.

Field Summary

Fields

Modifier and Type	Field	Description
private final GenericGF	field

Constructor Summary

Constructors

Constructor	Description
ReedSolomonDecoder(GenericGF field)

Method Summary

Modifier and Type	Method	Description
void	decode(int[] received, int twoS)	Decodes given set of received codewords, which include both data and error-correction codewords.
int	decodeWithECCount(int[] received, int twoS)	Decodes given set of received codewords, which include both data and error-correction codewords.
private int[]	findErrorLocations(GenericGFPoly errorLocator)
private int[]	findErrorMagnitudes(GenericGFPoly errorEvaluator, int[] errorLocations)
private GenericGFPoly[]	runEuclideanAlgorithm(GenericGFPoly a, GenericGFPoly b, int R)

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

field

private final GenericGF field

Constructor Details

ReedSolomonDecoder

public ReedSolomonDecoder(GenericGF field)

Method Details

decode

public void decode(int[] received,
 int twoS)
            throws ReedSolomonException

Decodes given set of received codewords, which include both data and error-correction codewords. Really, this means it uses Reed-Solomon to detect and correct errors, in-place, in the input.

Parameters:

received - data and error-correction codewords

twoS - number of error-correction codewords available

Throws:

ReedSolomonException - if decoding fails for any reason

decodeWithECCount

public int decodeWithECCount(int[] received,
 int twoS)
                      throws ReedSolomonException

Decodes given set of received codewords, which include both data and error-correction codewords. Really, this means it uses Reed-Solomon to detect and correct errors, in-place, in the input.

Parameters:

received - data and error-correction codewords

twoS - number of error-correction codewords available

Returns:

the number of errors corrected

Throws:

ReedSolomonException - if decoding fails for any reason

runEuclideanAlgorithm

private GenericGFPoly[] runEuclideanAlgorithm(GenericGFPoly a,
 GenericGFPoly b,
 int R)
                                       throws ReedSolomonException

Throws:

ReedSolomonException

findErrorLocations

private int[] findErrorLocations(GenericGFPoly errorLocator)
                          throws ReedSolomonException

Throws:

ReedSolomonException

findErrorMagnitudes

private int[] findErrorMagnitudes(GenericGFPoly errorEvaluator,
 int[] errorLocations)