/// <summary>
/// Adds n1 and n2 and puts result in dest, without intermediate memory allocation
/// (unsafe if n1 and n2 disagree in precision, safe even if dest is n1 or n2)
/// </summary>
/// <param name="dest"></param>
/// <param name="n1"></param>
/// <param name="n2"></param>
public static void SubFast(BigInt dest, BigInt n1, BigInt n2)
{
//We cast to the highest input precision...
if (n1.digitArray.Length != n2.digitArray.Length) MakeSafe(ref n1, ref n2);
//Then we up the output precision if less than the input precision.
if (dest.digitArray.Length < n1.digitArray.Length) n1.MakeSafe(ref dest);
int Length = n1.digitArray.Length;
if (n1.sign != n2.sign)
{
//Copies sources into digit array and working set for all cases, to avoid
//problems when dest is n1 or n2
for (int i = 0; i < Length; i++)
{
dest.workingSet[i] = n2.digitArray[i];
dest.digitArray[i] = n1.digitArray[i];
}
dest.AddInternalBits(dest.workingSet);
dest.sign = n1.sign;
}
else
{
bool lessThan = LtInt(n1, n2);
if (lessThan)
{
for (int i = 0; i < Length; i++)
{
dest.workingSet[i] = n1.digitArray[i];
dest.digitArray[i] = n2.digitArray[i];
}
dest.SubInternalBits(dest.workingSet);
dest.sign = !n1.sign;
}
else
{
for (int i = 0; i < Length; i++)
{
dest.workingSet[i] = n2.digitArray[i];
dest.digitArray[i] = n1.digitArray[i];
}
dest.SubInternalBits(dest.workingSet);
dest.sign = n1.sign;
}
}
}