76 lines
2.7 KiB
Java
76 lines
2.7 KiB
Java
/*
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* Copyright 2008 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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package com.google.zxing.common.reedsolomon;
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import java.util.Vector;
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/**
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* <p>Implements Reed-Solomon enbcoding, as the name implies.</p>
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*
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* @author Sean Owen
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* @author William Rucklidge
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*/
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public final class ReedSolomonEncoder {
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private final GF256 field;
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private final Vector cachedGenerators;
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public ReedSolomonEncoder(GF256 field) {
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if (!GF256.QR_CODE_FIELD.equals(field)) {
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throw new IllegalArgumentException("Only QR Code is supported at this time");
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}
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this.field = field;
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this.cachedGenerators = new Vector();
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cachedGenerators.addElement(new GF256Poly(field, new int[] { 1 }));
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}
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private GF256Poly buildGenerator(int degree) {
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if (degree >= cachedGenerators.size()) {
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GF256Poly lastGenerator = (GF256Poly) cachedGenerators.elementAt(cachedGenerators.size() - 1);
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for (int d = cachedGenerators.size(); d <= degree; d++) {
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GF256Poly nextGenerator = lastGenerator.multiply(new GF256Poly(field, new int[] { 1, field.exp(d - 1) }));
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cachedGenerators.addElement(nextGenerator);
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lastGenerator = nextGenerator;
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}
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}
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return (GF256Poly) cachedGenerators.elementAt(degree);
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}
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public void encode(int[] toEncode, int ecBytes) {
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if (ecBytes == 0) {
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throw new IllegalArgumentException("No error correction bytes");
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}
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int dataBytes = toEncode.length - ecBytes;
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if (dataBytes <= 0) {
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throw new IllegalArgumentException("No data bytes provided");
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}
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GF256Poly generator = buildGenerator(ecBytes);
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int[] infoCoefficients = new int[dataBytes];
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System.arraycopy(toEncode, 0, infoCoefficients, 0, dataBytes);
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GF256Poly info = new GF256Poly(field, infoCoefficients);
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info = info.multiplyByMonomial(ecBytes, 1);
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GF256Poly remainder = info.divide(generator)[1];
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int[] coefficients = remainder.getCoefficients();
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int numZeroCoefficients = ecBytes - coefficients.length;
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for (int i = 0; i < numZeroCoefficients; i++) {
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toEncode[dataBytes + i] = 0;
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}
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System.arraycopy(coefficients, 0, toEncode, dataBytes + numZeroCoefficients, coefficients.length);
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}
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}
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