zxing/csharp/datamatrix/decoder/DataBlock.cs

/*
 * 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.
 */

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace com.google.zxing.datamatrix.decoder
{

    /**
     * <p>Encapsulates a block of data within a Data Matrix Code. Data Matrix Codes may split their data into
     * multiple blocks, each of which is a unit of data and error-correction codewords. Each
     * is represented by an instance of this class.</p>
     *
     * @author bbrown@google.com (Brian Brown)
     */
    public sealed class DataBlock
    {
          private  int numDataCodewords;
          private  sbyte[] codewords;

          private DataBlock(int numDataCodewords, sbyte[] codewords) {
            this.numDataCodewords = numDataCodewords;
            this.codewords = codewords;
          }

          /**
           * <p>When Data Matrix Codes use multiple data blocks, they actually interleave the bytes of each of them.
           * That is, the first byte of data block 1 to n is written, then the second bytes, and so on. This
           * method will separate the data into original blocks.</p>
           *
           * @param rawCodewords bytes as read directly from the Data Matrix Code
           * @param version version of the Data Matrix Code
           * @return {@link DataBlock}s containing original bytes, "de-interleaved" from representation in the
           *         Data Matrix Code
           */
          public static DataBlock[] getDataBlocks(sbyte[] rawCodewords,
                                           Version version) {
            // Figure out the number and size of data blocks used by this version
            Version.ECBlocks ecBlocks = version.getECBlocks();

            // First count the total number of data blocks
            int totalBlocks = 0;
            Version.ECB[] ecBlockArray = ecBlocks.getECBlocks();
            for (int i = 0; i < ecBlockArray.Length; i++) {
              totalBlocks += ecBlockArray[i].getCount();
            }

            // Now establish DataBlocks of the appropriate size and number of data codewords
            DataBlock[] result = new DataBlock[totalBlocks];
            int numResultBlocks = 0;
            for (int j = 0; j < ecBlockArray.Length; j++) {
              Version.ECB ecBlock = ecBlockArray[j];
              for (int i = 0; i < ecBlock.getCount(); i++) {
                int numDataCodewords = ecBlock.getDataCodewords();
                int numBlockCodewords = ecBlocks.getECCodewords() + numDataCodewords;
                result[numResultBlocks++] = new DataBlock(numDataCodewords, new sbyte[numBlockCodewords]);
              }
            }

            // All blocks have the same amount of data, except that the last n
            // (where n may be 0) have 1 less byte. Figure out where these start.
            // TODO(bbrown): There is only one case where there is a difference for Data Matrix for size 144
            int longerBlocksTotalCodewords = result[0].codewords.Length;
            //int shorterBlocksTotalCodewords = longerBlocksTotalCodewords - 1;

            int longerBlocksNumDataCodewords = longerBlocksTotalCodewords - ecBlocks.getECCodewords();
            int shorterBlocksNumDataCodewords = longerBlocksNumDataCodewords - 1;
            // The last elements of result may be 1 element shorter for 144 matrix
            // first fill out as many elements as all of them have minus 1
            int rawCodewordsOffset = 0;
            for (int i = 0; i < shorterBlocksNumDataCodewords; i++) {
              for (int j = 0; j < numResultBlocks; j++) {
                result[j].codewords[i] = rawCodewords[rawCodewordsOffset++];
              }
            }
            
            // Fill out the last data block in the longer ones
            bool specialVersion = version.getVersionNumber() == 24;
            int numLongerBlocks = specialVersion ? 8 : numResultBlocks;
            for (int j = 0; j < numLongerBlocks; j++) {
              result[j].codewords[longerBlocksNumDataCodewords - 1] = rawCodewords[rawCodewordsOffset++];
            }
            
            // Now add in error correction blocks
            int max = result[0].codewords.Length;
            for (int i = longerBlocksNumDataCodewords; i < max; i++) {
              for (int j = 0; j < numResultBlocks; j++) {
                int iOffset = (specialVersion && j > 7) ? i - 1 : i;
                result[j].codewords[iOffset] = rawCodewords[rawCodewordsOffset++];
              }
            }

            if (rawCodewordsOffset != rawCodewords.Length) {
              throw new ArgumentException();
            }

            return result;
          }

          public int getNumDataCodewords() {
            return numDataCodewords;
          }

          public sbyte[] getCodewords() {
            return codewords;
          }
    }
}