PDF417Decoder.cpp Example File

 // -*- mode:c++; tab-width:2; indent-tabs-mode:nil; c-basic-offset:2 -*-
 /*
  * Copyright 2010, 2012 ZXing authors All rights reserved.
  *
  * 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.
  *
  * 2012-06-27 hfn: PDF417 Reed-Solomon error correction, using following Java
  * source code:
  * http://code.google.com/p/zxing/issues/attachmentText?id=817&aid=8170033000&name=pdf417-java-reed-solomon-error-correction-2.patch&token=0819f5d7446ae2814fd91385eeec6a11
  */

 #include <zxing/pdf417/PDF417Reader.h>
 #include <zxing/pdf417/decoder/Decoder.h>
 #include <zxing/pdf417/decoder/BitMatrixParser.h>
 #include <zxing/pdf417/decoder/DecodedBitStreamParser.h>
 #include <zxing/ReaderException.h>
 #include <zxing/common/reedsolomon/ReedSolomonException.h>

 using zxing::pdf417::decoder::Decoder;
 using zxing::pdf417::decoder::ec::ErrorCorrection;
 using zxing::Ref;
 using zxing::DecoderResult;

 // VC++

 using zxing::BitMatrix;
 using zxing::DecodeHints;
 using zxing::ArrayRef;

 const int Decoder::MAX_ERRORS = 3;
 const int Decoder::MAX_EC_CODEWORDS = 512;

 Ref<DecoderResult> Decoder::decode(Ref<BitMatrix> bits, DecodeHints const& hints) {
   (void)hints;
   // Construct a parser to read the data codewords and error-correction level
   BitMatrixParser parser(bits);
   ArrayRef<int> codewords(parser.readCodewords());
   if (codewords->size() == 0) {
     throw FormatException("PDF:Decoder:decode: cannot read codewords");
   }

   int ecLevel = parser.getECLevel();
   int numECCodewords = 1 << (ecLevel + 1);
   ArrayRef<int> erasures = parser.getErasures();

   correctErrors(codewords, erasures, numECCodewords);
   verifyCodewordCount(codewords, numECCodewords);

   // Decode the codewords
   return DecodedBitStreamParser::decode(codewords);
 }

 /**
  * Verify that all is OK with the codeword array.
  *
  * @param codewords
  * @return an index to the first data codeword.
  * @throws FormatException
  */
 void Decoder::verifyCodewordCount(ArrayRef<int> codewords, int numECCodewords) {
   int cwsize = codewords->size();
   if (cwsize < 4) {
     // Codeword array size should be at least 4 allowing for
     // Count CW, At least one Data CW, Error Correction CW, Error Correction CW
     throw FormatException("PDF:Decoder:verifyCodewordCount: codeword array too small!");
   }
   // The first codeword, the Symbol Length Descriptor, shall always encode the total number of data
   // codewords in the symbol, including the Symbol Length Descriptor itself, data codewords and pad
   // codewords, but excluding the number of error correction codewords.
   int numberOfCodewords = codewords[0];
   if (numberOfCodewords > cwsize) {
     throw FormatException("PDF:Decoder:verifyCodewordCount: bad codeword number descriptor!");
   }
   if (numberOfCodewords == 0) {
     // Reset to the length of the array - 8 (Allow for at least level 3 Error Correction (8 Error Codewords)
     if (numECCodewords < cwsize) {
       codewords[0] = cwsize - numECCodewords;
     } else {
       throw FormatException("PDF:Decoder:verifyCodewordCount: bad error correction cw number!");
     }
   }
 }

 /**
  * Correct errors whenever it is possible using Reed-Solomom algorithm
  *
  * @param codewords, erasures, numECCodewords
  * @return 0.
  * @throws FormatException
  */
 void Decoder::correctErrors(ArrayRef<int> codewords,
                             ArrayRef<int> erasures, int numECCodewords) {
   if (erasures->size() > numECCodewords / 2 + MAX_ERRORS ||
       numECCodewords < 0 || numECCodewords > MAX_EC_CODEWORDS) {
     throw FormatException("PDF:Decoder:correctErrors: Too many errors or EC Codewords corrupted");
   }

   Ref<ErrorCorrection> errorCorrection(new ErrorCorrection);
   errorCorrection->decode(codewords, numECCodewords, erasures);

   // 2012-06-27 HFN if, despite of error correction, there are still codewords with invalid
   // value, throw an exception here:
   for (int i = 0; i < codewords->size(); i++) {
     if (codewords[i]<0) {
       throw FormatException("PDF:Decoder:correctErrors: Error correction did not succeed!");
     }
   }
 }