shadowsocks-windows/shadowsocks-csharp/3rd/zxing/qrcode/decoder/DataMask.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.
*/

using ZXing.Common;

namespace ZXing.QrCode.Internal
{
   /// <summary> <p>Encapsulates data masks for the data bits in a QR code, per ISO 18004:2006 6.8. Implementations
   /// of this class can un-mask a raw BitMatrix. For simplicity, they will unmask the entire BitMatrix,
   /// including areas used for finder patterns, timing patterns, etc. These areas should be unused
   /// after the point they are unmasked anyway.</p>
   /// 
   /// <p>Note that the diagram in section 6.8.1 is misleading since it indicates that i is column position
   /// and j is row position. In fact, as the text says, i is row position and j is column position.</p>
   /// 
   /// </summary>
   /// <author>  Sean Owen
   /// </author>
   /// <author>www.Redivivus.in (suraj.supekar@redivivus.in) - Ported from ZXING Java Source 
   /// </author>
   abstract class DataMask
   {
      /// <summary> See ISO 18004:2006 6.8.1</summary>
      private static readonly DataMask[] DATA_MASKS = new DataMask[]
                                                         {
                                                            new DataMask000(),
                                                            new DataMask001(), 
                                                            new DataMask010(), 
                                                            new DataMask011(), 
                                                            new DataMask100(),
                                                            new DataMask101(), 
                                                            new DataMask110(), 
                                                            new DataMask111()
                                                         };

      private DataMask()
      {
      }

      /// <summary> <p>Implementations of this method reverse the data masking process applied to a QR Code and
      /// make its bits ready to read.</p>
      /// 
      /// </summary>
      /// <param name="bits">representation of QR Code bits
      /// </param>
      /// <param name="dimension">dimension of QR Code, represented by bits, being unmasked
      /// </param>
      internal void unmaskBitMatrix(BitMatrix bits, int dimension)
      {
         for (int i = 0; i < dimension; i++)
         {
            for (int j = 0; j < dimension; j++)
            {
               if (isMasked(i, j))
               {
                  bits.flip(j, i);
               }
            }
         }
      }

      internal abstract bool isMasked(int i, int j);

      /// <param name="reference">a value between 0 and 7 indicating one of the eight possible
      /// data mask patterns a QR Code may use
      /// </param>
      /// <returns> {@link DataMask} encapsulating the data mask pattern
      /// </returns>
      internal static DataMask forReference(int reference)
      {
         if (reference < 0 || reference > 7)
         {
            throw new System.ArgumentException();
         }
         return DATA_MASKS[reference];
      }

      /// <summary> 000: mask bits for which (x + y) mod 2 == 0</summary>
      private sealed class DataMask000 : DataMask
      {
         internal override bool isMasked(int i, int j)
         {
            return ((i + j) & 0x01) == 0;
         }
      }

      /// <summary> 001: mask bits for which x mod 2 == 0</summary>
      private sealed class DataMask001 : DataMask
      {
         internal override bool isMasked(int i, int j)
         {
            return (i & 0x01) == 0;
         }
      }

      /// <summary> 010: mask bits for which y mod 3 == 0</summary>
      private sealed class DataMask010 : DataMask
      {
         internal override bool isMasked(int i, int j)
         {
            return j % 3 == 0;
         }
      }

      /// <summary> 011: mask bits for which (x + y) mod 3 == 0</summary>
      private sealed class DataMask011 : DataMask
      {
         internal override bool isMasked(int i, int j)
         {
            return (i + j) % 3 == 0;
         }
      }

      /// <summary> 100: mask bits for which (x/2 + y/3) mod 2 == 0</summary>
      private sealed class DataMask100 : DataMask
      {
         internal override bool isMasked(int i, int j)
         {
            return ((((int)((uint)i >> 1)) + (j / 3)) & 0x01) == 0;
         }
      }

      /// <summary> 101: mask bits for which xy mod 2 + xy mod 3 == 0</summary>
      private sealed class DataMask101 : DataMask
      {
         internal override bool isMasked(int i, int j)
         {
            int temp = i * j;
            return (temp & 0x01) + (temp % 3) == 0;
         }
      }

      /// <summary> 110: mask bits for which (xy mod 2 + xy mod 3) mod 2 == 0</summary>
      private sealed class DataMask110 : DataMask
      {
         internal override bool isMasked(int i, int j)
         {
            int temp = i * j;
            return (((temp & 0x01) + (temp % 3)) & 0x01) == 0;
         }
      }

      /// <summary> 111: mask bits for which ((x+y)mod 2 + xy mod 3) mod 2 == 0</summary>
      private sealed class DataMask111 : DataMask
      {
         internal override bool isMasked(int i, int j)
         {
            return ((((i + j) & 0x01) + ((i * j) % 3)) & 0x01) == 0;
         }
      }
   }
}