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using System;

namespace CRC
{
 /// <summary>
 /// CRC8 的摘要说明。
 /// </summary>
 public class CRC8:ICRC
 {
  #region CRC 8 位校验表

  /// <summary>
  /// CRC 8 位校验表
  /// </summary>
  public  byte[] CRC8_Table = new byte[]
  {
   0,94,188,226,97,63,221,131,194,156,126,32,163,253,31,65,
   157,195,33,127,252,162,64,30, 95,1,227,189,62,96,130,220,
   35,125,159,193,66,28,254,160,225,191,93,3,128,222,60,98,
   190,224,2,92,223,129,99,61,124,34,192,158,29,67,161,255,
   70,24,250,164,39,121,155,197,132,218,56,102,229,187,89,7,            
   219,133,103,57,186,228,6,88,25,71,165,251,120,38,196,154,
   101,59,217,135,4,90,184,230,167,249,27,69,198,152,122,36,                        
   248,166,68,26,153,199,37,123,58,100,134,216,91,5,231,185,            
   140,210,48,110,237,179,81,15,78,16,242,172,47,113,147,205,
   17,79,173,243,112,46,204,146,211,141,111,49,178,236,14,80,
   175,241,19,77,206,144,114,44,109,51,209,143,12,82,176,238,
   50,108,142,208,83,13,239,177,240,174,76,18,145,207,45,115,
   202,148,118,40,171,245,23,73,8,86,180,234,105,55,213,139,
   87,9,235,181,54,104,138,212,149,203, 41,119,244,170,72,22,
   233,183,85,11,136,214,52,106,43,117,151,201,74,20,246,168,
   116,42,200,150,21,75,169,247,182,232,10,84,215,137,107,53
  };
  #endregion

  uint crc = 0;
  
  /// <summary>
  ///返回 CRC8校验结果;
  /// </summary>
  public long Value
  {
   get
   {
    return crc;
   }
   set
   {
    crc = (uint)value;
   }
  }

  /// <summary>
  /// CRC校验前设置校验值
  /// </summary>
  public void Reset()
  {
   crc = 0;
  }

  /// <summary>
  /// 8 位 CRC 校验 产生校验码 需要被校验码和校验码
  /// </summary>
  /// <param name="CRC"></param>
  /// <param name="OldCRC"> 初始为 0 ,以后为 返回值 ret </param>
  /// <returns> 产生校验码时 ret　为校验码</returns>
  
  public void Crc(byte CRC,byte OldCRC)
  {
   crc = CRC8_Table[OldCRC ^ CRC];
  }

  /// <summary>
  /// 8 位 CRC 校验 产生校验码 只要被校验码
  /// </summary>
  /// <param name="bval"></param>
  public void Crc(int bval)
  {
   crc = CRC8_Table[crc ^ bval];
  }

  /// <summary>
  /// 8 位 CRC 校验 产生校验码 只要被校验的字节数组
  /// </summary>
  /// <param name="buffer"></param>
  public void Crc(byte[] buffer)
  {

   Crc(buffer,0,buffer.Length);
  }

  /// <summary>
  /// 8 位 CRC 校验 产生校验码 要被校验的字节数组、起始结果位置和字节长度
  /// </summary>
  /// <param name="buf"></param>
  /// <param name="off"></param>
  /// <param name="len"></param>
  public void Crc(byte[] buf,int off ,int len)
  {
   if (buf == null)
   {
    throw new ArgumentNullException("buf");
   }
   
   if (off < 0 || len < 0 || off + len > buf.Length)
   {
    throw new ArgumentOutOfRangeException();
   }
   for (int i = off; i < len ; i ++)
   {
    Crc(buf[i]);
   }
  }
 }
}