shadowsocks-windows/shadowsocks-csharp/3rd/zxing/qrcode/decoder/DataBlock.cs

/*
* Copyright 2007 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.
*/

namespace ZXing.QrCode.Internal
{
   /// <summary> <p>Encapsulates a block of data within a QR Code. QR 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>
   /// 
   /// </summary>
   /// <author>  Sean Owen
   /// </author>
   /// <author>www.Redivivus.in (suraj.supekar@redivivus.in) - Ported from ZXING Java Source 
   /// </author>
   internal sealed class DataBlock
   {
      private readonly int numDataCodewords;
      private readonly byte[] codewords;

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

      /// <summary> <p>When QR Codes use multiple data blocks, they are actually interleaved.
      /// 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>
      /// 
      /// </summary>
      /// <param name="rawCodewords">bytes as read directly from the QR Code
      /// </param>
      /// <param name="version">version of the QR Code
      /// </param>
      /// <param name="ecLevel">error-correction level of the QR Code
      /// </param>
      /// <returns> {@link DataBlock}s containing original bytes, "de-interleaved" from representation in the
      /// QR Code
      /// </returns>
      internal static DataBlock[] getDataBlocks(byte[] rawCodewords, Version version, ErrorCorrectionLevel ecLevel)
      {

         if (rawCodewords.Length != version.TotalCodewords)
         {
            throw new System.ArgumentException();
         }

         // Figure out the number and size of data blocks used by this version and
         // error correction level
         Version.ECBlocks ecBlocks = version.getECBlocksForLevel(ecLevel);

         // First count the total number of data blocks
         int totalBlocks = 0;
         Version.ECB[] ecBlockArray = ecBlocks.getECBlocks();
         foreach (var ecBlock in ecBlockArray)
         {
            totalBlocks += ecBlock.Count;
         }

         // Now establish DataBlocks of the appropriate size and number of data codewords
         DataBlock[] result = new DataBlock[totalBlocks];
         int numResultBlocks = 0;
         foreach (var ecBlock in ecBlockArray)
         {
            for (int i = 0; i < ecBlock.Count; i++)
            {
               int numDataCodewords = ecBlock.DataCodewords;
               int numBlockCodewords = ecBlocks.ECCodewordsPerBlock + numDataCodewords;
               result[numResultBlocks++] = new DataBlock(numDataCodewords, new byte[numBlockCodewords]);
            }
         }

         // All blocks have the same amount of data, except that the last n
         // (where n may be 0) have 1 more byte. Figure out where these start.
         int shorterBlocksTotalCodewords = result[0].codewords.Length;
         int longerBlocksStartAt = result.Length - 1;
         while (longerBlocksStartAt >= 0)
         {
            int numCodewords = result[longerBlocksStartAt].codewords.Length;
            if (numCodewords == shorterBlocksTotalCodewords)
            {
               break;
            }
            longerBlocksStartAt--;
         }
         longerBlocksStartAt++;

         int shorterBlocksNumDataCodewords = shorterBlocksTotalCodewords - ecBlocks.ECCodewordsPerBlock;
         // The last elements of result may be 1 element longer;
         // first fill out as many elements as all of them have
         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
         for (int j = longerBlocksStartAt; j < numResultBlocks; j++)
         {
            result[j].codewords[shorterBlocksNumDataCodewords] = rawCodewords[rawCodewordsOffset++];
         }
         // Now add in error correction blocks
         int max = result[0].codewords.Length;
         for (int i = shorterBlocksNumDataCodewords; i < max; i++)
         {
            for (int j = 0; j < numResultBlocks; j++)
            {
               int iOffset = j < longerBlocksStartAt ? i : i + 1;
               result[j].codewords[iOffset] = rawCodewords[rawCodewordsOffset++];
            }
         }
         return result;
      }

      internal int NumDataCodewords
      {
         get
         {
            return numDataCodewords;
         }
      }

      internal byte[] Codewords
      {
         get
         {
            return codewords;
         }
      }
   }
}