DataMatrixDecoder.cpp Example File

 /*
  *  Decoder.cpp
  *  zxing
  *
  *  Created by Luiz Silva on 09/02/2010.
  *  Copyright 2010 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.
  */

 #include <zxing/datamatrix/decoder/Decoder.h>
 #include <zxing/datamatrix/decoder/BitMatrixParser.h>
 #include <zxing/datamatrix/decoder/DataBlock.h>
 #include <zxing/datamatrix/decoder/DecodedBitStreamParser.h>
 #include <zxing/datamatrix/Version.h>
 #include <zxing/ReaderException.h>
 #include <zxing/ChecksumException.h>
 #include <zxing/common/reedsolomon/ReedSolomonException.h>

 using zxing::Ref;
 using zxing::DecoderResult;
 //using zxing::datamatrix::Decoder;
 //using zxing::datamatrix::DataBlock;
 //using zxing::datamatrix::DecodedBitStreamParser;

 // VC++
 using zxing::ArrayRef;
 using zxing::BitMatrix;

 namespace zxing {
 namespace datamatrix {

 Decoder::Decoder() : rsDecoder_(GenericGF::DATA_MATRIX_FIELD_256) {}

 void Decoder::correctErrors(ArrayRef<byte> codewordBytes, int numDataCodewords) {
   int numCodewords = codewordBytes->size();
   ArrayRef<int> codewordInts(numCodewords);
   for (int i = 0; i < numCodewords; i++) {
     codewordInts[i] = codewordBytes[i] & 0xff;
   }
   int numECCodewords = numCodewords - numDataCodewords;
   try {
     rsDecoder_.decode(codewordInts, numECCodewords);
   } catch (ReedSolomonException const& ignored) {
     (void)ignored;
     throw ChecksumException();
   }
   // Copy back into array of bytes -- only need to worry about the bytes that were data
   // We don't care about errors in the error-correction codewords
   for (int i = 0; i < numDataCodewords; i++) {
     codewordBytes[i] = (byte)codewordInts[i];
   }
 }

 Ref<DecoderResult> Decoder::decode(Ref<BitMatrix> bits) {
   // Construct a parser and read version, error-correction level
   BitMatrixParser parser(bits);
   Version *version = parser.readVersion(bits);

   // Read codewords
   ArrayRef<byte> codewords(parser.readCodewords());
   // Separate into data blocks
   std::vector<Ref<DataBlock> > dataBlocks = DataBlock::getDataBlocks(codewords, version);

   int dataBlocksCount = dataBlocks.size();

   // Count total number of data bytes
   int totalBytes = 0;
   for (int i = 0; i < dataBlocksCount; i++) {
     totalBytes += dataBlocks[i]->getNumDataCodewords();
   }
   ArrayRef<byte> resultBytes(totalBytes);

   // Error-correct and copy data blocks together into a stream of bytes
   for (int j = 0; j < dataBlocksCount; j++) {
     Ref<DataBlock> dataBlock(dataBlocks[j]);
     ArrayRef<byte> codewordBytes = dataBlock->getCodewords();
     int numDataCodewords = dataBlock->getNumDataCodewords();
     correctErrors(codewordBytes, numDataCodewords);
     for (int i = 0; i < numDataCodewords; i++) {
       // De-interlace data blocks.
       resultBytes[i * dataBlocksCount + j] = codewordBytes[i];
     }
   }
   // Decode the contents of that stream of bytes
   DecodedBitStreamParser decodedBSParser;
   return Ref<DecoderResult> (decodedBSParser.decode(resultBytes));
 }

 }
 }