/*
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* Copyright 2007 ZXing authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/*namespace com.google.zxing.common.reedsolomon {*/
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// import GenericGF from './GenericGF';
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import AbstractGenericGF from './AbstractGenericGF';
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/**
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* <p>Represents a polynomial whose coefficients are elements of a GF.
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* Instances of this class are immutable.</p>
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*
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* <p>Much credit is due to William Rucklidge since portions of this code are an indirect
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* port of his C++ Reed-Solomon implementation.</p>
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*
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* @author Sean Owen
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*/
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export default class AbstractGenericGFPoly {
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getCoefficients() {
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return this.coefficients;
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}
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/**
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* @return degree of this polynomial
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*/
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getDegree() {
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return this.coefficients.length - 1;
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}
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/**
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* @return true iff this polynomial is the monomial "0"
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*/
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isZero() {
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return this.coefficients[0] === 0;
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}
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/**
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* @return coefficient of x^degree term in this polynomial
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*/
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getCoefficient(degree /*int*/) {
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return this.coefficients[this.coefficients.length - 1 - degree];
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}
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/**
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* @return evaluation of this polynomial at a given point
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*/
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evaluateAt(a /*int*/) {
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if (a === 0) {
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// Just return the x^0 coefficient
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return this.getCoefficient(0);
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}
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const coefficients = this.coefficients;
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let result;
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if (a === 1) {
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// Just the sum of the coefficients
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result = 0;
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for (let i = 0, length = coefficients.length; i !== length; i++) {
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const coefficient = coefficients[i];
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result = AbstractGenericGF.addOrSubtract(result, coefficient);
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}
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return result;
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}
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result = coefficients[0];
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const size = coefficients.length;
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const field = this.field;
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for (let i = 1; i < size; i++) {
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result = AbstractGenericGF.addOrSubtract(field.multiply(a, result), coefficients[i]);
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}
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return result;
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}
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/*@Override*/
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toString() {
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let result = '';
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for (let degree = this.getDegree(); degree >= 0; degree--) {
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let coefficient = this.getCoefficient(degree);
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if (coefficient !== 0) {
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if (coefficient < 0) {
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result += ' - ';
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coefficient = -coefficient;
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}
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else {
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if (result.length > 0) {
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result += ' + ';
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}
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}
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if (degree === 0 || coefficient !== 1) {
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const alphaPower = this.field.log(coefficient);
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if (alphaPower === 0) {
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result += '1';
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}
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else if (alphaPower === 1) {
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result += 'a';
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}
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else {
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result += 'a^';
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result += alphaPower;
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}
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}
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if (degree !== 0) {
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if (degree === 1) {
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result += 'x';
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}
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else {
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result += 'x^';
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result += degree;
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}
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}
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}
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}
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return result;
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}
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}
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