public void ShiftRight(FastInteger fastint)
{
if (fastint.Sign <= 0)
{
return;
}
if (fastint.CanFitInInt32())
{
this.ShiftRightInt(fastint.ToInt32());
}
else
{
EInteger bi = fastint.ToEInteger();
while (bi.Sign > 0)
{
var count = 1000000;
if (bi.CompareTo((EInteger)1000000) < 0)
{
count = (int)bi;
}
this.ShiftRightInt(count);
bi -= (EInteger)count;
if (this.isSmall ? this.shiftedSmall == 0 :
this.shiftedBigInt.IsZero)
{
break;
}
}
}
}
public static FastIntegerFixed FromFastInteger(FastInteger fi)
{
if (fi.CanFitInInt32())
{
return(FromInt32(fi.ToInt32()));
}
else
{
return(FastIntegerFixed.FromBig(fi.ToEInteger()));
}
}
public void ShiftToDigits(
FastInteger bits,
FastInteger preShift,
bool truncate)
{
if (bits.Sign < 0)
{
throw new ArgumentException("bits's sign(" + bits.Sign +
") is less than 0");
}
if (preShift != null && preShift.Sign > 0)
{
this.knownBitLength = this.knownBitLength ?? this.CalcKnownBitLength();
// DebugUtility.Log("bits=" + bits + " pre=" + preShift + " known=" +
// (//kbl) + " [" + this.shiftedBigInt + "]");
if (this.knownBitLength.CompareTo(bits) <= 0)
{
// Known digit length is already small enough
// NOTE: For BitShiftAccumulator, truncating and shifting
// are the same, unlike in DigitShiftAccumulator
this.ShiftRight(preShift);
VerifyKnownLength();
return;
}
else
{
FastInteger bitDiff = this.knownBitLength.Copy()
.Subtract(bits);
// DebugUtility.Log("bitDiff=" + bitDiff);
int cmp = bitDiff.CompareTo(preShift);
if (cmp <= 0)
{
// NOTE: For BitShiftAccumulator, truncating and shifting
// are the same, unlike in DigitShiftAccumulator
this.ShiftRight(preShift);
VerifyKnownLength();
return;
}
else
{
// NOTE: For BitShiftAccumulator, truncating and shifting
// are the same, unlike in DigitShiftAccumulator
this.ShiftRight(bitDiff);
VerifyKnownLength();
return;
}
}
}
if (bits.CanFitInInt32())
{
this.ShiftToDigitsInt(bits.ToInt32());
VerifyKnownLength();
}
else
{
this.knownBitLength = this.knownBitLength ?? this.CalcKnownBitLength();
EInteger bigintDiff = this.knownBitLength.ToEInteger();
EInteger bitsBig = bits.ToEInteger();
bigintDiff -= (EInteger)bitsBig;
if (bigintDiff.Sign > 0)
{
// current length is greater than the
// desired bit length
this.ShiftRight(FastInteger.FromBig(bigintDiff));
}
VerifyKnownLength();
}
}
private void ShiftBigToBits(int bits)
{
// Shifts a number until it reaches the given number of bits,
// gathering information on whether the last bit discarded is set and
// whether the discarded bits to the right of that bit are set. Assumes
// that the big integer being shifted is positive.
if (this.knownBitLength != null)
{
if (this.knownBitLength.CompareToInt(bits) <= 0)
{
return;
}
}
this.knownBitLength = this.knownBitLength ?? this.CalcKnownBitLength();
if (this.knownBitLength.CompareToInt(bits) <= 0)
{
return;
}
// Shift by the difference in bit length
if (this.knownBitLength.CompareToInt(bits) > 0)
{
var bs = 0;
if (this.knownBitLength.CanFitInInt32())
{
bs = this.knownBitLength.ToInt32();
bs -= bits;
}
else
{
FastInteger bitShift =
this.knownBitLength.Copy().SubtractInt(bits);
if (!bitShift.CanFitInInt32())
{
this.ShiftRight(bitShift);
return;
}
bs = bitShift.ToInt32();
}
this.knownBitLength.SetInt(bits);
this.discardedBitCount.AddInt(bs);
if (bs == 1)
{
bool odd = !this.shiftedBigInt.IsEven;
this.shiftedBigInt >>= 1;
this.bitsAfterLeftmost |= this.bitLeftmost;
this.bitLeftmost = odd ? 1 : 0;
}
else
{
this.bitsAfterLeftmost |= this.bitLeftmost;
long lowestSet = this.shiftedBigInt.GetLowBitAsInt64();
if (lowestSet == Int64.MaxValue)
{
EInteger lowestSetBit = this.shiftedBigInt.GetLowBitAsEInteger();
if (lowestSetBit.CompareTo(bs - 1) < 0)
{
// One of the discarded bits after
// the last one is set
this.bitsAfterLeftmost |= 1;
this.bitLeftmost = this.shiftedBigInt.GetSignedBit(bs - 1) ? 1 :
0;
}
else if (lowestSetBit.CompareTo(bs - 1) > 0)
{
// Means all discarded bits are zero
this.bitLeftmost = 0;
}
else
{
// Only the last discarded bit is set
this.bitLeftmost = 1;
}
}
else
{
if (lowestSet < bs - 1)
{
// One of the discarded bits after
// the last one is set
this.bitsAfterLeftmost |= 1;
this.bitLeftmost = this.shiftedBigInt.GetSignedBit(bs - 1) ? 1 :
0;
}
else if (lowestSet > bs - 1)
{
// Means all discarded bits are zero
this.bitLeftmost = 0;
}
else
{
// Only the last discarded bit is set
this.bitLeftmost = 1;
}
}
this.shiftedBigInt >>= bs;
}
if (bits < SmallBitLength)
{
// Shifting to small number of bits,
// convert to small integer
this.isSmall = true;
this.shiftedSmall = (int)this.shiftedBigInt;
}
this.bitsAfterLeftmost = (this.bitsAfterLeftmost != 0) ? 1 : 0;
}
}
