StringBuilder result = new StringBuilder(8 * getDegree()); for (int degree = getDegree(); degree >= 0; degree--) { int coefficient = getCoefficient(degree); if (coefficient != 0) { if (coefficient < 0) {
StringBuilder result = new StringBuilder(8 * getDegree()); for (int degree = getDegree(); degree >= 0; degree--) { int coefficient = getCoefficient(degree); if (coefficient != 0) { if (coefficient < 0) {
/** * @return evaluation of this polynomial at a given point */ int evaluateAt(int a) { if (a == 0) { // Just return the x^0 coefficient return getCoefficient(0); } if (a == 1) { // Just the sum of the coefficients int result = 0; for (int coefficient : coefficients) { result = GenericGF.addOrSubtract(result, coefficient); } return result; } int result = coefficients[0]; int size = coefficients.length; for (int i = 1; i < size; i++) { result = GenericGF.addOrSubtract(field.multiply(a, result), coefficients[i]); } return result; }
/** * @return evaluation of this polynomial at a given point */ int evaluateAt(int a) { if (a == 0) { // Just return the x^0 coefficient return getCoefficient(0); } if (a == 1) { // Just the sum of the coefficients int result = 0; for (int coefficient : coefficients) { result = GenericGF.addOrSubtract(result, coefficient); } return result; } int result = coefficients[0]; int size = coefficients.length; for (int i = 1; i < size; i++) { result = GenericGF.addOrSubtract(field.multiply(a, result), coefficients[i]); } return result; }
GenericGFPoly[] divide(GenericGFPoly other) { if (!field.equals(other.field)) { throw new IllegalArgumentException("GenericGFPolys do not have same GenericGF field"); } if (other.isZero()) { throw new IllegalArgumentException("Divide by 0"); } GenericGFPoly quotient = field.getZero(); GenericGFPoly remainder = this; int denominatorLeadingTerm = other.getCoefficient(other.getDegree()); int inverseDenominatorLeadingTerm = field.inverse(denominatorLeadingTerm); while (remainder.getDegree() >= other.getDegree() && !remainder.isZero()) { int degreeDifference = remainder.getDegree() - other.getDegree(); int scale = field.multiply(remainder.getCoefficient(remainder.getDegree()), inverseDenominatorLeadingTerm); GenericGFPoly term = other.multiplyByMonomial(degreeDifference, scale); GenericGFPoly iterationQuotient = field.buildMonomial(degreeDifference, scale); quotient = quotient.addOrSubtract(iterationQuotient); remainder = remainder.addOrSubtract(term); } return new GenericGFPoly[] { quotient, remainder }; }
private int[] findErrorLocations(GenericGFPoly errorLocator) throws ReedSolomonException { // This is a direct application of Chien's search int numErrors = errorLocator.getDegree(); if (numErrors == 1) { // shortcut return new int[] { errorLocator.getCoefficient(1) }; } int[] result = new int[numErrors]; int e = 0; for (int i = 1; i < field.getSize() && e < numErrors; i++) { if (errorLocator.evaluateAt(i) == 0) { result[e] = field.inverse(i); e++; } } if (e != numErrors) { throw new ReedSolomonException("Error locator degree does not match number of roots"); } return result; }
GenericGFPoly[] divide(GenericGFPoly other) { if (!field.equals(other.field)) { throw new IllegalArgumentException("GenericGFPolys do not have same GenericGF field"); } if (other.isZero()) { throw new IllegalArgumentException("Divide by 0"); } GenericGFPoly quotient = field.getZero(); GenericGFPoly remainder = this; int denominatorLeadingTerm = other.getCoefficient(other.getDegree()); int inverseDenominatorLeadingTerm = field.inverse(denominatorLeadingTerm); while (remainder.getDegree() >= other.getDegree() && !remainder.isZero()) { int degreeDifference = remainder.getDegree() - other.getDegree(); int scale = field.multiply(remainder.getCoefficient(remainder.getDegree()), inverseDenominatorLeadingTerm); GenericGFPoly term = other.multiplyByMonomial(degreeDifference, scale); GenericGFPoly iterationQuotient = field.buildMonomial(degreeDifference, scale); quotient = quotient.addOrSubtract(iterationQuotient); remainder = remainder.addOrSubtract(term); } return new GenericGFPoly[] { quotient, remainder }; }
private int[] findErrorLocations(GenericGFPoly errorLocator) throws ReedSolomonException { // This is a direct application of Chien's search int numErrors = errorLocator.getDegree(); if (numErrors == 1) { // shortcut return new int[] { errorLocator.getCoefficient(1) }; } int[] result = new int[numErrors]; int e = 0; for (int i = 1; i < field.getSize() && e < numErrors; i++) { if (errorLocator.evaluateAt(i) == 0) { result[e] = field.inverse(i); e++; } } if (e != numErrors) { throw new ReedSolomonException("Error locator degree does not match number of roots"); } return result; }
int denominatorLeadingTerm = rLast.getCoefficient(rLast.getDegree()); int dltInverse = field.inverse(denominatorLeadingTerm); while (r.getDegree() >= rLast.getDegree() && !r.isZero()) { int degreeDiff = r.getDegree() - rLast.getDegree(); int scale = field.multiply(r.getCoefficient(r.getDegree()), dltInverse); q = q.addOrSubtract(field.buildMonomial(degreeDiff, scale)); r = r.addOrSubtract(rLast.multiplyByMonomial(degreeDiff, scale)); int sigmaTildeAtZero = t.getCoefficient(0); if (sigmaTildeAtZero == 0) { throw new ReedSolomonException("sigmaTilde(0) was zero");
int denominatorLeadingTerm = rLast.getCoefficient(rLast.getDegree()); int dltInverse = field.inverse(denominatorLeadingTerm); while (r.getDegree() >= rLast.getDegree() && !r.isZero()) { int degreeDiff = r.getDegree() - rLast.getDegree(); int scale = field.multiply(r.getCoefficient(r.getDegree()), dltInverse); q = q.addOrSubtract(field.buildMonomial(degreeDiff, scale)); r = r.addOrSubtract(rLast.multiplyByMonomial(degreeDiff, scale)); int sigmaTildeAtZero = t.getCoefficient(0); if (sigmaTildeAtZero == 0) { throw new ReedSolomonException("sigmaTilde(0) was zero");