csharp/common/reedsolomon/ReedSolomonEncoder.cs

   1 /*\r
   2 * Copyright 2008 ZXing authors\r
   3 *\r
   4 * Licensed under the Apache License, Version 2.0 (the "License");\r
   5 * you may not use this file except in compliance with the License.\r
   6 * You may obtain a copy of the License at\r
   7 *\r
   8 *      http://www.apache.org/licenses/LICENSE-2.0\r
   9 *\r
  10 * Unless required by applicable law or agreed to in writing, software\r
  11 * distributed under the License is distributed on an "AS IS" BASIS,\r
  12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\r
  13 * See the License for the specific language governing permissions and\r
  14 * limitations under the License.\r
  15 */\r
  16 using System;\r
  17 namespace com.google.zxing.common.reedsolomon\r
  18 {\r
  19         \r
  20         /// <summary> <p>Implements Reed-Solomon enbcoding, as the name implies.</p>\r
  21         /// \r
  22         /// </summary>\r
  23         /// <author>  Sean Owen\r
  24         /// </author>\r
  25         /// <author>  William Rucklidge\r
  26         /// </author>\r
  27         /// <author>www.Redivivus.in (suraj.supekar@redivivus.in) - Ported from ZXING Java Source \r
  28         /// </author>\r
  29         public sealed class ReedSolomonEncoder\r
  30         {\r
  31                 \r
  32                 //UPGRADE_NOTE: Final was removed from the declaration of 'field '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"\r
  33                 private GF256 field;\r
  34                 //UPGRADE_NOTE: Final was removed from the declaration of 'cachedGenerators '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"\r
  35                 private System.Collections.ArrayList cachedGenerators;\r
  36                 \r
  37                 public ReedSolomonEncoder(GF256 field)\r
  38                 {\r
  39                         if (!GF256.QR_CODE_FIELD.Equals(field))\r
  40                         {\r
  41                                 throw new System.ArgumentException("Only QR Code is supported at this time");\r
  42                         }\r
  43                         this.field = field;\r
  44                         this.cachedGenerators = System.Collections.ArrayList.Synchronized(new System.Collections.ArrayList(10));\r
  45                         cachedGenerators.Add(new GF256Poly(field, new int[]{1}));\r
  46                 }\r
  47                 \r
  48                 private GF256Poly buildGenerator(int degree)\r
  49                 {\r
  50                         if (degree >= cachedGenerators.Count)\r
  51                         {\r
  52                                 GF256Poly lastGenerator = (GF256Poly) cachedGenerators[cachedGenerators.Count - 1];\r
  53                                 for (int d = cachedGenerators.Count; d <= degree; d++)\r
  54                                 {\r
  55                                         GF256Poly nextGenerator = lastGenerator.multiply(new GF256Poly(field, new int[]{1, field.exp(d - 1)}));\r
  56                                         cachedGenerators.Add(nextGenerator);\r
  57                                         lastGenerator = nextGenerator;\r
  58                                 }\r
  59                         }\r
  60                         return (GF256Poly) cachedGenerators[degree];\r
  61                 }\r
  62                 \r
  63                 public void  encode(int[] toEncode, int ecBytes)\r
  64                 {\r
  65                         if (ecBytes == 0)\r
  66                         {\r
  67                                 throw new System.ArgumentException("No error correction bytes");\r
  68                         }\r
  69                         int dataBytes = toEncode.Length - ecBytes;\r
  70                         if (dataBytes <= 0)\r
  71                         {\r
  72                                 throw new System.ArgumentException("No data bytes provided");\r
  73                         }\r
  74                         GF256Poly generator = buildGenerator(ecBytes);\r
  75                         int[] infoCoefficients = new int[dataBytes];\r
  76                         Array.Copy(toEncode, 0, infoCoefficients, 0, dataBytes);\r
  77                         GF256Poly info = new GF256Poly(field, infoCoefficients);\r
  78                         info = info.multiplyByMonomial(ecBytes, 1);\r
  79                         GF256Poly remainder = info.divide(generator)[1];\r
  80                         int[] coefficients = remainder.Coefficients;\r
  81                         int numZeroCoefficients = ecBytes - coefficients.Length;\r
  82                         for (int i = 0; i < numZeroCoefficients; i++)\r
  83                         {\r
  84                                 toEncode[dataBytes + i] = 0;\r
  85                         }\r
  86                         Array.Copy(coefficients, 0, toEncode, dataBytes + numZeroCoefficients, coefficients.Length);\r
  87                 }\r
  88         }\r
  89 }