1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
|
/*
* Copyright 2008 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.zxing.common.reedsolomon;
import java.util.Vector;
/**
* <p>Implements Reed-Solomon enbcoding, as the name implies.</p>
*
* @author Sean Owen
* @author William Rucklidge
*/
public final class ReedSolomonEncoder {
private final GenericGF field;
private final Vector cachedGenerators;
public ReedSolomonEncoder(GenericGF field) {
if (!GenericGF.QR_CODE_FIELD_256.equals(field)) {
throw new IllegalArgumentException("Only QR Code is supported at this time");
}
this.field = field;
this.cachedGenerators = new Vector();
cachedGenerators.addElement(new GenericGFPoly(field, new int[] { 1 }));
}
private GenericGFPoly buildGenerator(int degree) {
if (degree >= cachedGenerators.size()) {
GenericGFPoly lastGenerator = (GenericGFPoly) cachedGenerators.elementAt(cachedGenerators.size() - 1);
for (int d = cachedGenerators.size(); d <= degree; d++) {
GenericGFPoly nextGenerator = lastGenerator.multiply(new GenericGFPoly(field, new int[] { 1, field.exp(d - 1) }));
cachedGenerators.addElement(nextGenerator);
lastGenerator = nextGenerator;
}
}
return (GenericGFPoly) cachedGenerators.elementAt(degree);
}
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");
}
GenericGFPoly generator = buildGenerator(ecBytes);
int[] infoCoefficients = new int[dataBytes];
System.arraycopy(toEncode, 0, infoCoefficients, 0, dataBytes);
GenericGFPoly info = new GenericGFPoly(field, infoCoefficients);
info = info.multiplyByMonomial(ecBytes, 1);
GenericGFPoly 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);
}
}
|
