/// <summary>
/// инициализирует таблицу для быстрого расчёта
/// </summary>
public void InitTable()
{
CRChelper <byte> charRefl = new CRChelper <byte>(Limits.CHAR_BIT, Reflect);
CRChelper <T> BitsRefl = new CRChelper <T>(Bits, Reflect);
// factor-out constants to avoid recalculation
T fast_hi_bit = masking_type.HighBitMask;
const byte byte_hi_bit = MaskUint <T> .ByteHighBitMask;
// loop over every possible dividend value
byte dividend = 0;
do
{
T remainder = new T();
// go through all the dividend's bits
for (byte mask = byte_hi_bit; mask > 0; mask >>= 1)
{
// check if divisor fits
if ((dividend & mask) != 0)
{
remainder = Operator <T> .Xor(remainder, fast_hi_bit);
}
// do polynominal division
bool bNotEqual = Operator <T> .NotEqual(Operator <T> .And(remainder, fast_hi_bit), Operator <T> .Zero);
if (bNotEqual)
{
remainder = Operator <T> .LeftShift(remainder, 1);
remainder = Operator <T> .Xor(remainder, TruncPoly);
}
else
{
remainder = Operator <T> .LeftShift(remainder, 1);
}
}
T tmp = BitsRefl.reflect(remainder);
// следующее выражение необязательно. Просто можно обнулить старшие(неиспользуемые) биты в регистре
//tmp = Operator<T>.And(tmp, masking_type.SigBits);
Table_[charRefl.reflect(dividend)] = tmp;
++dividend;
}while (dividend != 0);
}
/// <summary>
/// Конструктор ЦРЦ-вычислителя
/// </summary>
public CRCoptimal(int Bits, T TruncPoly, T InitialRemainder, T FinalXorValue, bool ReflectInput = false, bool ReflectRemainder = false)
{
this.Bits = Bits;
this.ReflectInput = ReflectInput;
this.FinalXorValue = FinalXorValue;
this.ReflectRemainder = ReflectRemainder;
this.TruncPoly = TruncPoly;
this.InitialRemainder = InitialRemainder;
masking_type = new MaskUint <T>(Bits);
helper_type = new CRChelper <T>(Bits, ReflectInput);
reflect_out_type = new CRChelper <T>(Bits, (ReflectRemainder != ReflectInput));
Remainder = helper_type.reflect(InitialRemainder);
crc_table_type = new CRCtable <T>(Bits, TruncPoly, ReflectInput);
crc_table_type.InitTable();
}
