public void encode(int[] toEncode, int ecBytes) { if (ecBytes == 0) { throw new IllegalArgumentException("No error correction bytes"); } int dataBytes = toEncode.length - ecBytes; if (dataBytes <= 0) { throw new IllegalArgumentException("No data bytes provided"); } GF256Poly generator = buildGenerator(ecBytes); int[] infoCoefficients = new int[dataBytes]; System.arraycopy(toEncode, 0, infoCoefficients, 0, dataBytes); GF256Poly info = new GF256Poly(field, infoCoefficients); info = info.multiplyByMonomial(ecBytes, 1); GF256Poly remainder = info.divide(generator)[1]; int[] coefficients = remainder.getCoefficients(); int numZeroCoefficients = ecBytes - coefficients.length; for (int i = 0; i < numZeroCoefficients; i++) { toEncode[dataBytes + i] = 0; } System.arraycopy(coefficients, 0, toEncode, dataBytes + numZeroCoefficients, coefficients.length); }
public void encode(int[] toEncode, int ecBytes) { if (ecBytes == 0) { throw new IllegalArgumentException("No error correction bytes"); } int dataBytes = toEncode.length - ecBytes; if (dataBytes <= 0) { throw new IllegalArgumentException("No data bytes provided"); } GF256Poly generator = buildGenerator(ecBytes); int[] infoCoefficients = new int[dataBytes]; System.arraycopy(toEncode, 0, infoCoefficients, 0, dataBytes); GF256Poly info = new GF256Poly(field, infoCoefficients); info = info.multiplyByMonomial(ecBytes, 1); GF256Poly remainder = info.divide(generator)[1]; int[] coefficients = remainder.getCoefficients(); int numZeroCoefficients = ecBytes - coefficients.length; for (int i = 0; i < numZeroCoefficients; i++) { toEncode[dataBytes + i] = 0; } System.arraycopy(coefficients, 0, toEncode, dataBytes + numZeroCoefficients, coefficients.length); }
GF256Poly[] divide(GF256Poly other) { if (!field.equals(other.field)) { throw new IllegalArgumentException("GF256Polys do not have same GF256 field"); } if (other.isZero()) { throw new IllegalArgumentException("Divide by 0"); } GF256Poly quotient = field.getZero(); GF256Poly 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); GF256Poly term = other.multiplyByMonomial(degreeDifference, scale); GF256Poly iterationQuotient = field.buildMonomial(degreeDifference, scale); quotient = quotient.addOrSubtract(iterationQuotient); remainder = remainder.addOrSubtract(term); } return new GF256Poly[] { quotient, remainder }; }
GF256Poly[] divide(GF256Poly other) { if (!field.equals(other.field)) { throw new IllegalArgumentException("GF256Polys do not have same GF256 field"); } if (other.isZero()) { throw new IllegalArgumentException("Divide by 0"); } GF256Poly quotient = field.getZero(); GF256Poly 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); GF256Poly term = other.multiplyByMonomial(degreeDifference, scale); GF256Poly iterationQuotient = field.buildMonomial(degreeDifference, scale); quotient = quotient.addOrSubtract(iterationQuotient); remainder = remainder.addOrSubtract(term); } return new GF256Poly[] { quotient, remainder }; }
int scale = field.multiply(r.getCoefficient(r.getDegree()), dltInverse); q = q.addOrSubtract(field.buildMonomial(degreeDiff, scale)); r = r.addOrSubtract(rLast.multiplyByMonomial(degreeDiff, scale));