/// <summary>
/// Initalizes a new instance of the class using the provided algorithm type.
/// </summary>
/// <param name="type">Indicates what type of CRC algorithm this instance should use.</param>
public CrcHelper(CrcAlgorithmType type)
{
this.Initialize(type);
this._type = type;
this._table = this.CreateTable();
}
private void Initialize(CrcAlgorithmType type)
{
switch (type)
{
case CrcAlgorithmType.Crc16Ccitt:
this._order = 16;
this._polynom = 0x1021;
//this.direct = true;
this._crcInitial = 0xffff;
this._crcXor = 0xffff;
this._reflectIn = true;
this._reflectOut = true;
break;
case CrcAlgorithmType.Crc32:
default:
this._order = 32;
this._polynom = 0x4c11db7;
//this.direct = true;
this._crcInitial = 0xffffffff;
this._crcXor = 0xffffffff;
this._reflectIn = true;
this._reflectOut = true;
break;
}
this._crcHighBit = (ulong)1 << (this._order - 1);
this._crcMask = ((((ulong)1 << (this._order - 1)) - 1) << 1) | 1;
this._crcInitialDirect = _crcInitial;
}
public void AlgorithmCompareWithGeneral(CrcAlgorithmType type)
{
var testData = new byte[] { 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39 };
var crc1 = CrcFactory.GetCrc(type);
var crc2 = CrcFactory.GetCrc(crc1.Argument);
var result1 = crc1.GetCrcValue(testData);
var result2 = crc2.GetCrcValue(testData);
Assert.Equal(result1, result2);
}
/// <summary>
/// 获取指定类型的CRC算法
/// </summary>
/// <param name="type">crc类型</param>
/// <exception cref="NotSupportedException">未实现的算法或内部错误</exception>
public static ICrc GetCrc(CrcAlgorithmType type)
{//对部分有具体计算方法的算法类型直接使用其实现，其他则采用通用算法
if (type != CrcAlgorithmType.None)
{
const string SpecifiedNamaspace = "Parsifal.Util.CRC.Algorithm";
var name = Enum.GetName(typeof(CrcAlgorithmType), type);
var instance = Assembly.GetExecutingAssembly().CreateInstance($"{SpecifiedNamaspace}.{name}");
if (instance != null)
{
return((ICrc)instance);
}
else
{
var field = typeof(CrcStandardParam).GetField(name, BindingFlags.Public | BindingFlags.Static);
if (field != null)
{
var argument = (CrcArgument)field.GetValue(typeof(CrcArgument));
return(new GeneralCRC(argument));
}
}
}
throw new NotSupportedException();
}
