public IBigInteger Remainder(
IBigInteger n)
{
if (n.SignValue == 0)
throw new ArithmeticException("Division by zero error");
if (this.SignValue == 0)
return Zero;
// For small values, use fast remainder method
if (n.Magnitude.Length == 1)
{
int val = n.Magnitude[0];
if (val > 0)
{
if (val == 1)
return Zero;
// TODO Make this func work on uint, and handle val == 1?
int rem = Remainder(val);
return rem == 0
? Zero
: new BigInteger(SignValue, new int[] {rem}, false);
}
}
if (CompareNoLeadingZeroes(0, Magnitude, 0, n.Magnitude) < 0)
return this;
int[] result;
if (n.QuickPow2Check()) // n is power of two
{
// TODO Move before small values branch above?
result = LastNBits(n.Abs().BitLength - 1);
}
else
{
result = (int[]) this.Magnitude.Clone();
result = Remainder(result, n.Magnitude);
}
return new BigInteger(SignValue, result, true);
}
public IBigInteger[] DivideAndRemainder(
IBigInteger val)
{
if (val.SignValue == 0)
throw new ArithmeticException("Division by zero error");
var biggies = new IBigInteger[2];
if (SignValue == 0)
{
biggies[0] = Zero;
biggies[1] = Zero;
}
else if (val.QuickPow2Check()) // val is power of two
{
int e = val.Abs().BitLength - 1;
IBigInteger quotient = this.Abs().ShiftRight(e);
int[] remainder = this.LastNBits(e);
biggies[0] = val.SignValue == this.SignValue ? quotient : quotient.Negate();
biggies[1] = new BigInteger(this.SignValue, remainder, true);
}
else
{
var remainder = (int[]) this.Magnitude.Clone();
int[] quotient = Divide(remainder, val.Magnitude);
biggies[0] = new BigInteger(this.SignValue*val.SignValue, quotient, true);
biggies[1] = new BigInteger(this.SignValue, remainder, true);
}
return biggies;
}
public IBigInteger Multiply(
IBigInteger val)
{
if (SignValue == 0 || val.SignValue == 0)
return Zero;
if (val.QuickPow2Check()) // val is power of two
{
IBigInteger result = this.ShiftLeft(val.Abs().BitLength - 1);
return val.SignValue > 0 ? result : result.Negate();
}
if (this.QuickPow2Check()) // this is power of two
{
IBigInteger result = val.ShiftLeft(this.Abs().BitLength - 1);
return this.SignValue > 0 ? result : result.Negate();
}
int resLength = (this.BitLength + val.BitLength)/BitsPerInt + 1;
var res = new int[resLength];
if (val == this)
{
Square(res, this.Magnitude);
}
else
{
Multiply(res, this.Magnitude, val.Magnitude);
}
return new BigInteger(SignValue*val.SignValue, res, true);
}
public IBigInteger Divide(
IBigInteger val)
{
if (val.SignValue == 0)
throw new ArithmeticException("Division by zero error");
if (SignValue == 0)
return Zero;
if (val.QuickPow2Check()) // val is power of two
{
IBigInteger result = this.Abs().ShiftRight(val.Abs().BitLength - 1);
return val.SignValue == this.SignValue ? result : result.Negate();
}
var mag = (int[]) this.Magnitude.Clone();
return new BigInteger(this.SignValue*val.SignValue, Divide(mag, val.Magnitude), true);
}