/**
* @return evaluation of this polynomial at a given point
*/
public int evaluateAt(int a)
{
if (a == 0)
{
// Just return the x^0 coefficient
return(getCoefficient(0));
}
int size = coefficients.Length;
int result = 0;
if (a == 1)
{
// Just the sum of the coefficients
result = 0;
for (int i = 0; i < size; i++)
{
result = GF256.addOrSubtract(result, coefficients[i]);
}
return(result);
}
result = coefficients[0];
for (int i = 1; i < size; i++)
{
result = GF256.addOrSubtract(field.multiply(a, result), coefficients[i]);
}
return(result);
}
public GF256Poly multiply(GF256Poly other)
{
if (!field.Equals(other.field))
{
throw new ArgumentException("GF256Polys do not have same GF256 field");
}
if (isZero() || other.isZero())
{
return(field.getZero());
}
int[] aCoefficients = this.coefficients;
int aLength = aCoefficients.Length;
int[] bCoefficients = other.coefficients;
int bLength = bCoefficients.Length;
int[] product = new int[aLength + bLength - 1];
for (int i = 0; i < aLength; i++)
{
int aCoeff = aCoefficients[i];
for (int j = 0; j < bLength; j++)
{
product[i + j] = GF256.addOrSubtract(product[i + j],
field.multiply(aCoeff, bCoefficients[j]));
}
}
return(new GF256Poly(field, product));
}
internal GF256Poly Multiply(GF256Poly other)
{
if (!field.Equals(other.field))
{
throw new ArgumentException("GF256Polys do not have same GF256 field");
}
if (Zero || other.Zero)
{
return(field.Zero);
}
int[] aCoefficients = Coefficients;
int aLength = aCoefficients.Length;
int[] bCoefficients = other.Coefficients;
int bLength = bCoefficients.Length;
int[] product = new int[aLength + bLength - 1];
for (int i = 0; i < aLength; i++)
{
int aCoeff = aCoefficients[i];
for (int j = 0; j < bLength; j++)
{
product[i + j] = GF256.AddOrSubtract(product[i + j], field.Multiply(aCoeff, bCoefficients[j]));
}
}
return(new GF256Poly(field, product));
}
/// <summary> evaluation of this polynomial at a given point
/// </summary>
internal int EvaluateAt(int a)
{
if (a == 0)
{
// Just return the x^0 coefficient
return(GetCoefficient(0));
}
int size = Coefficients.Length;
if (a == 1)
{
// Just the sum of the coefficients
int result = 0;
for (int i = 0; i < size; i++)
{
result = GF256.AddOrSubtract(result, Coefficients[i]);
}
return(result);
}
int result2 = Coefficients[0];
for (int i = 1; i < size; i++)
{
result2 = GF256.AddOrSubtract(field.Multiply(a, result2), Coefficients[i]);
}
return(result2);
}
//UPGRADE_NOTE: Final was removed from the declaration of 'coefficients '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
/// <param name="field">the {@link GF256} instance representing the field to use
/// to perform computations
/// </param>
/// <param name="coefficients">coefficients as ints representing elements of GF(256), arranged
/// from most significant (highest-power term) coefficient to least significant
/// </param>
/// <throws> IllegalArgumentException if argument is null or empty, </throws>
/// <summary> or if leading coefficient is 0 and this is not a
/// constant polynomial (that is, it is not the monomial "0")
/// </summary>
internal GF256Poly(GF256 field, int[] coefficients)
{
if (coefficients == null || coefficients.Length == 0)
{
throw new ArgumentException();
}
this.field = field;
int coefficientsLength = coefficients.Length;
if (coefficientsLength > 1 && coefficients[0] == 0)
{
// Leading term must be non-zero for anything except the constant polynomial "0"
int firstNonZero = 1;
while (firstNonZero < coefficientsLength && coefficients[firstNonZero] == 0)
{
firstNonZero++;
}
if (firstNonZero == coefficientsLength)
{
Coefficients = field.Zero.Coefficients;
}
else
{
Coefficients = new int[coefficientsLength - firstNonZero];
Array.Copy(coefficients, firstNonZero, Coefficients, 0, Coefficients.Length);
}
}
else
{
Coefficients = coefficients;
}
}
private int[] findErrorMagnitudes(GF256Poly errorEvaluator, int[] errorLocations, bool dataMatrix)
{
// This is directly applying Forney's Formula
int s = errorLocations.Length;
int[] result = new int[s];
for (int i = 0; i < s; i++)
{
int xiInverse = field.inverse(errorLocations[i]);
int denominator = 1;
for (int j = 0; j < s; j++)
{
if (i != j)
{
denominator = field.multiply(denominator, GF256.addOrSubtract(1, field.multiply(errorLocations[j], xiInverse)));
}
}
result[i] = field.multiply(errorEvaluator.evaluateAt(xiInverse), field.inverse(denominator));
// Thanks to sanfordsquires for this fix:
if (dataMatrix)
{
result[i] = field.multiply(result[i], xiInverse);
}
}
return(result);
}
/// <param name="field">the {@link GF256} instance representing the field to use
/// to perform computations
/// </param>
/// <param name="coefficients">coefficients as ints representing elements of GF(256), arranged
/// from most significant (highest-power term) coefficient to least significant
/// </param>
/// <throws> IllegalArgumentException if argument is null or empty, </throws>
/// <summary> or if leading coefficient is 0 and this is not a
/// constant polynomial (that is, it is not the monomial "0")
/// </summary>
internal GF256Poly(GF256 field, int[] coefficients)
{
if (coefficients == null || coefficients.Length == 0)
{
throw new System.ArgumentException();
}
this.field = field;
int coefficientsLength = coefficients.Length;
if (coefficientsLength > 1 && coefficients[0] == 0)
{
// Leading term must be non-zero for anything except the constant polynomial "0"
int firstNonZero = 1;
while (firstNonZero < coefficientsLength && coefficients[firstNonZero] == 0)
{
firstNonZero++;
}
if (firstNonZero == coefficientsLength)
{
this.coefficients = field.Zero.coefficients;
}
else
{
this.coefficients = new int[coefficientsLength - firstNonZero];
Array.Copy(coefficients, firstNonZero, this.coefficients, 0, this.coefficients.Length);
}
}
else
{
this.coefficients = coefficients;
}
}
public ReedSolomonEncoder(GF256 field) {
if (!GF256.QR_CODE_FIELD.Equals(field)) {
throw new ArgumentException("Only QR Code is supported at this time");
}
this.Field = field;
this.cachedGenerators = new ArrayList();
cachedGenerators.Add(new GF256Poly(field, new int[] { 1 }));
}
public ReedSolomonEncoder(GF256 field)
{
if (!GF256.QR_CODE_FIELD.Equals(field))
{
throw new System.ArgumentException("Only QR Code is supported at this time");
}
this.field = field;
this.cachedGenerators = new System.Collections.Generic.List <Object>(10);
cachedGenerators.Add(new GF256Poly(field, new int[] { 1 }));
}
public ReedSolomonEncoder(GF256 field)
{
if (!GF256.QR_CODE_FIELD.Equals(field))
{
throw new ArgumentException("Only QR Code is supported at this time");
}
this.Field = field;
this.cachedGenerators = new ArrayList();
cachedGenerators.Add(new GF256Poly(field, new int[] { 1 }));
}
public ReedSolomonEncoder(GF256 field)
{
if (!GF256.QR_CODE_FIELD.Equals(field))
{
throw new ArgumentException("Only QR Code is supported at this time");
}
this.field = field;
cachedGenerators = System.Collections.ArrayList.Synchronized(new System.Collections.ArrayList(10));
cachedGenerators.Add(new GF256Poly(field, new[] { 1 }));
}
internal ReedSolomonEncoder(GF256 field)
{
if (!GF256.QR_CODE_FIELD.Equals(field))
{
throw new System.ArgumentException("Only QR Code is supported at this time");
}
this.field = field;
this.cachedGenerators = System.Collections.ArrayList.Synchronized(new System.Collections.ArrayList(10));
cachedGenerators.Add(new GF256Poly(field, new int[]{1}));
}
public ReedSolomonEncoder(GF256 field)
{
if (!GF256.QR_CODE_FIELD.Equals(field))
{
throw new System.ArgumentException("Only QR Code is supported at this time");
}
this.field = field;
this.cachedGenerators = new System.Collections.Generic.List<Object>(10);
cachedGenerators.Add(new GF256Poly(field, new int[]{1}));
}
public ReedSolomonEncoder(GF256 field)
{
if (!GF256.QR_CODE_FIELD.Equals(field))
{
throw new System.ArgumentException("Only QR Code is supported at this time");
}
this.field = field;
// this.cachedGenerators = System.Collections.ArrayList.Synchronized(new System.Collections.ArrayList(10)); // commented by .net follower (http://dotnetfollower.com)
this.cachedGenerators = new System.Collections.Generic.List<Object>(10); // added by .net follower (http://dotnetfollower.com)
cachedGenerators.Add(new GF256Poly(field, new int[]{1}));
}
private System.Collections.Generic.List <Object> cachedGenerators; // added by .net follower (http://dotnetfollower.com)
public ReedSolomonEncoder(GF256 field)
{
if (!GF256.QR_CODE_FIELD.Equals(field))
{
throw new System.ArgumentException("Only QR Code is supported at this time");
}
this.field = field;
// this.cachedGenerators = System.Collections.ArrayList.Synchronized(new System.Collections.ArrayList(10)); // commented by .net follower (http://dotnetfollower.com)
this.cachedGenerators = new System.Collections.Generic.List <Object>(10); // added by .net follower (http://dotnetfollower.com)
cachedGenerators.Add(new GF256Poly(field, new int[] { 1 }));
}
/**
* <p>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.</p>
*
* @param received data and error-correction codewords
* @param twoS number of error-correction codewords available
* @throws ReedSolomonException if decoding fails for any reason
*/
public void decode(int[] received, int twoS)
{
try{
GF256Poly poly = new GF256Poly(field, received);
int[] syndromeCoefficients = new int[twoS];
bool dataMatrix = field.Equals(GF256.DATA_MATRIX_FIELD);
bool noError = true;
for (int i = 0; i < twoS; i++)
{
// Thanks to sanfordsquires for this fix:
int eval = poly.evaluateAt(field.exp(dataMatrix ? i + 1 : i));
syndromeCoefficients[syndromeCoefficients.Length - 1 - i] = eval;
if (eval != 0)
{
noError = false;
}
}
if (noError)
{
return;
}
GF256Poly syndrome = new GF256Poly(field, syndromeCoefficients);
GF256Poly[] sigmaOmega =
runEuclideanAlgorithm(field.buildMonomial(twoS, 1), syndrome, twoS);
GF256Poly sigma = sigmaOmega[0];
GF256Poly omega = sigmaOmega[1];
int[] errorLocations = findErrorLocations(sigma);
int[] errorMagnitudes = findErrorMagnitudes(omega, errorLocations, dataMatrix);
for (int i = 0; i < errorLocations.Length; i++)
{
int position = received.Length - 1 - field.log(errorLocations[i]);
if (position < 0)
{
throw new ReedSolomonException("Bad error location");
}
received[position] = GF256.addOrSubtract(received[position], errorMagnitudes[i]);
}
}catch (ReedSolomonException e) {
throw new ReedSolomonException(e.Message);
}
}
internal GF256Poly AddOrSubtract(GF256Poly other)
{
if (!field.Equals(other.field))
{
throw new ArgumentException("GF256Polys do not have same GF256 field");
}
if (Zero)
{
return(other);
}
if (other.Zero)
{
return(this);
}
int[] smallerCoefficients = Coefficients;
int[] largerCoefficients = other.Coefficients;
if (smallerCoefficients.Length > largerCoefficients.Length)
{
int[] temp = smallerCoefficients;
smallerCoefficients = largerCoefficients;
largerCoefficients = temp;
}
int[] sumDiff = new int[largerCoefficients.Length];
int lengthDiff = largerCoefficients.Length - smallerCoefficients.Length;
// Copy high-order terms only found in higher-degree polynomial's coefficients
Array.Copy(largerCoefficients, 0, sumDiff, 0, lengthDiff);
for (int i = lengthDiff; i < largerCoefficients.Length; i++)
{
sumDiff[i] = GF256.AddOrSubtract(smallerCoefficients[i - lengthDiff], largerCoefficients[i]);
}
return(new GF256Poly(field, sumDiff));
}
public ReedSolomonDecoder(GF256 field)
{
this.field = field;
}
public ReedSolomonDecoder(GF256 field)
{
this.field = field;
}
