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 }; }
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 GenericGFPoly[] runEuclideanAlgorithm(GenericGFPoly a, GenericGFPoly b, int R) throws ReedSolomonException { if (a.getDegree() < b.getDegree()) { GenericGFPoly temp = a; a = b; while (r.getDegree() >= R / 2) { GenericGFPoly rLastLast = rLast; GenericGFPoly tLastLast = tLast; 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)); if (r.getDegree() >= rLast.getDegree()) { throw new IllegalStateException("Division algorithm failed to reduce polynomial?");
private GenericGFPoly[] runEuclideanAlgorithm(GenericGFPoly a, GenericGFPoly b, int R) throws ReedSolomonException { if (a.getDegree() < b.getDegree()) { GenericGFPoly temp = a; a = b; while (r.getDegree() >= R / 2) { GenericGFPoly rLastLast = rLast; GenericGFPoly tLastLast = tLast; 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)); if (r.getDegree() >= rLast.getDegree()) { throw new IllegalStateException("Division algorithm failed to reduce polynomial?");
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; }
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; }