/// <summary>
/// Returns the number of bits in the binary representation of this which differ from the sign bit.
/// <para>Use BitLength(0) if you want to know the length of the binary value in bits.
/// If this is positive the result is equivalent to the number of bits set in the binary representation of this.
/// If this is negative the result is equivalent to the number of bits set in the binary representation of -this - 1.</para>
/// </summary>
internal static int BitCount(BigInteger Value)
{
int bCount = 0;
if (Value._sign == 0)
{
return(0);
}
int i = Value.FirstNonzeroDigit;;
if (Value._sign > 0)
{
for (; i < Value._numberLength; i++)
{
bCount += IntUtils.BitCount(Value._digits[i]);
}
}
else
{
// this digit absorbs the carry
bCount += IntUtils.BitCount(-Value._digits[i]);
for (i++; i < Value._numberLength; i++)
{
bCount += IntUtils.BitCount(~Value._digits[i]);
}
// We take the complement sum:
bCount = (Value._numberLength << 5) - bCount;
}
return(bCount);
}