/** * @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 addOrSubtract(GenericGFPoly other) { if (!field.equals(other.field)) { throw new IllegalArgumentException("GenericGFPolys do not have same GenericGF field"); } if (isZero()) { return other; } if (other.isZero()) { return this; } int[] smallerCoefficients = this.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 System.arraycopy(largerCoefficients, 0, sumDiff, 0, lengthDiff); for (int i = lengthDiff; i < largerCoefficients.length; i++) { sumDiff[i] = GenericGF.addOrSubtract(smallerCoefficients[i - lengthDiff], largerCoefficients[i]); } return new GenericGFPoly(field, sumDiff); }
GenericGFPoly addOrSubtract(GenericGFPoly other) { if (!field.equals(other.field)) { throw new IllegalArgumentException("GenericGFPolys do not have same GenericGF field"); } if (isZero()) { return other; } if (other.isZero()) { return this; } int[] smallerCoefficients = this.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 System.arraycopy(largerCoefficients, 0, sumDiff, 0, lengthDiff); for (int i = lengthDiff; i < largerCoefficients.length; i++) { sumDiff[i] = GenericGF.addOrSubtract(smallerCoefficients[i - lengthDiff], largerCoefficients[i]); } return new GenericGFPoly(field, sumDiff); }
GenericGFPoly multiply(GenericGFPoly other) { if (!field.equals(other.field)) { throw new IllegalArgumentException("GenericGFPolys do not have same GenericGF 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] = GenericGF.addOrSubtract(product[i + j], field.multiply(aCoeff, bCoefficients[j])); } } return new GenericGFPoly(field, product); }
GenericGFPoly multiply(GenericGFPoly other) { if (!field.equals(other.field)) { throw new IllegalArgumentException("GenericGFPolys do not have same GenericGF 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] = GenericGF.addOrSubtract(product[i + j], field.multiply(aCoeff, bCoefficients[j])); } } return new GenericGFPoly(field, product); }
throw new ReedSolomonException("Bad error location"); received[position] = GenericGF.addOrSubtract(received[position], errorMagnitudes[i]);
throw new ReedSolomonException("Bad error location"); received[position] = GenericGF.addOrSubtract(received[position], errorMagnitudes[i]);