C#集合之位数组的用法

　　　　static void BitArrayDemo()
        {
          var bits1 = new BitArray(8);
          bits1.SetAll(true);
          bits1.Set(1, false);
          bits1[5] = false;
          bits1[7] = false;
          Console.Write("initialized: ");
          DisplayBits(bits1);
          Console.WriteLine();
           //int i =      Convert.ToInt32(bits1);


          DisplayBits(bits1);
          bits1.Not();
          Console.Write(" not ");
          DisplayBits(bits1);
          Console.WriteLine();

          var bits2 = new BitArray(bits1);
          bits2[0] = true;
          bits2[1] = false;
          bits2[4] = true;
          DisplayBits(bits1);
          Console.Write(" or ");
          DisplayBits(bits2);
          Console.Write(" : ");
          bits1.Or(bits2);
          DisplayBits(bits1);
          Console.WriteLine();


          DisplayBits(bits2);
          Console.Write(" and ");
          DisplayBits(bits1);
          Console.Write(" : ");
          bits2.And(bits1);
          DisplayBits(bits2);
          Console.WriteLine();

          DisplayBits(bits1);
          Console.Write(" xor ");
          DisplayBits(bits2);
          bits1.Xor(bits2);
          Console.Write(" : ");
          DisplayBits(bits1);
          Console.WriteLine();
        }
        
        static void DisplayBits(BitArray bits)
        {
          foreach (bool bit in bits)
          {
            Console.Write(bit ? 1 : 0);
          }
        }

　　　　//对CreateMask方法的第一个调用来访问第一位的一个掩码
      //调用CreateMask后，bit1被设置为1。再次调用CreateMask方法，把第一个掩码作为参数传递给CreateMask方法，返回来第二位的一个掩码（是2）
      
      var bits1 = new BitVector32();
      int bit1 = BitVector32.CreateMask();     //1
      int bit2 = BitVector32.CreateMask(bit1); //2
      int bit3 = BitVector32.CreateMask(bit2); //4
      int bit4 = BitVector32.CreateMask(bit3); //8
      int bit5 = BitVector32.CreateMask(bit4); //16

      bits1[bit1] = true;
      bits1[bit2] = false;
      bits1[bit3] = true;
      bits1[bit4] = true;
      Console.WriteLine(bits1);

    //除了用CreateMask方法创建掩码之外，还可以自己定义掩码，也可以一次设置多位。
    //十六进制abcdef与二进制1010 1011 1100 1101 1110 1111相同
    bits1[0xabcdef] = true;
    Console.WriteLine(bits1);

　　　　//也可以把32位分别放在不同的片段中
      bits1[0xabcdef] = true;
      Console.WriteLine(bits1);


      int received = 0x79abcdef;

      var bits2 = new BitVector32(received);
      Console.WriteLine(bits2);
      //创建6个片段。第一个片段需要12位，有16进制0xfff定义。
      //第一次调用CreateSection方法直接受0xfff，为最前面的12位分配内存。
      //第二次调用CreateSection方法，将第一个片段和偏移量传递
      BitVector32.Section sectionA = BitVector32.CreateSection(0xfff);
      BitVector32.Section sectionB = BitVector32.CreateSection(0xff, sectionA);
      BitVector32.Section sectionC = BitVector32.CreateSection(0xf, sectionB);
      BitVector32.Section sectionD = BitVector32.CreateSection(0x7, sectionC);
      BitVector32.Section sectionE = BitVector32.CreateSection(0x7, sectionD);
      BitVector32.Section sectionF = BitVector32.CreateSection(0x3, sectionE);
    //bits2[sectionA]，把一个BitVector32.Section类型的值传递给BitVector32结构的索引器，会返回一个int。IntToBinaryString方法将这个int表示
      Console.WriteLine("Section A: " + IntToBinaryString(bits2[sectionA], true));
      Console.WriteLine("Section B: " + IntToBinaryString(bits2[sectionB], true));
      Console.WriteLine("Section C: " + IntToBinaryString(bits2[sectionC], true));
      Console.WriteLine("Section D: " + IntToBinaryString(bits2[sectionD], true));
      Console.WriteLine("Section E: " + IntToBinaryString(bits2[sectionE], true));
      Console.WriteLine("Section F: " + IntToBinaryString(bits2[sectionF], true));

      
    static string IntToBinaryString(int bits, bool removeTrailingZero)
    {
      var sb = new StringBuilder(32);

      for (int i = 0; i < 32; i++)
      {
        if ((bits & 0x80000000) != 0)
        {
          sb.Append("1");
        }
        else
        {
          sb.Append("0");
        }
        bits = bits << 1;
      }
      string s = sb.ToString();
      if (removeTrailingZero)
        return s.TrimStart('0');
      else
        return s;
    }