internal int SetFromCRTNumber( CRTBase ToSet, ChineseRemainder SetFrom )
{
try
{
if( NumbersArray == null )
throw( new Exception( "Bug: The NumbersArray should have been set up already." ));
// ToSet.SetToZero();
// CRTBaseArray[0] is 1.
if( SetFrom.GetDigitAt( 0 ) == 1 )
{
ToSet.SetToOne(); // 1 times 1 for this base.
CRTAccumulateForBaseMultiples.SetToOne();
}
else
{
ToSet.SetToZero();
CRTAccumulateForBaseMultiples.SetToZero();
}
int HighestNonZeroDigit = 1;
// Count starts at 1, so it's at the prime 3.
for( int Count = 1; Count < ChineseRemainder.DigitsArraySize; Count++ )
{
int Prime = (int)IntMath.GetPrimeAt( Count );
int AccumulateDigit = CRTAccumulateForBaseMultiples.GetDigitAt( Count );
int CRTInputTestDigit = SetFrom.GetDigitAt( Count );
int BaseDigit = CRTBaseArray[Count].GetDigitAt( Count );
if( BaseDigit == 0 )
throw( new Exception( "This never happens. BaseDigit == 0." ));
int BaseMult = CRTInputTestDigit;
if( BaseMult < AccumulateDigit )
BaseMult += Prime;
BaseMult -= AccumulateDigit;
int Inverse = MultInverseArray[Count, BaseDigit];
BaseMult = (BaseMult * Inverse) % Prime;
ToSet.SetDigitAt( BaseMult, Count );
if( BaseMult != 0 )
HighestNonZeroDigit = Count;
// Notice that this is using CRTBaseArray and not
// CRTBaseModArray.
// This would be very fast in parallel hardware,
// but not in software that has to do each digit
// one at a time.
CRTAccumulatePart.Copy( CRTBaseArray[Count] );
CRTAccumulatePart.Multiply( NumbersArray[BaseMult] );
CRTAccumulateForBaseMultiples.Add( CRTAccumulatePart );
}
return HighestNonZeroDigit;
}
catch( Exception Except )
{
throw( new Exception( "Exception in SetFromCRTNumber(): " + Except.Message ));
}
}
