/// <summary>
/// Returns all bits in range as ulong.
/// </summary>
/// <param name="pos">Position in bit array.</param>
/// <param name="numBits">Number of bits to get (must be 1-64).</param>
/// <returns>Returns requested range of bits.</returns>
public ulong GetBits(int pos, int numBits = 1)
{
CheckArgs(pos, numBits);
var idxB = pos >> 6;
var shiftB = pos & 0x3f;
if (shiftB + numBits < 64)
{
var mask = 0xfffffffffffffffful >> (64 - numBits);
return(Bitwise.ExtractBits(Ptr[idxB], shiftB, mask));
}
var end = math.min(pos + numBits, Length);
var idxE = end >> 6;
var shiftE = end & 0x3f;
var maskB = 0xfffffffffffffffful >> shiftB;
ulong valueB = Bitwise.ExtractBits(Ptr[idxB], shiftB, maskB);
var maskE = 0xfffffffffffffffful >> (64 - shiftE);
ulong valueE = Bitwise.ExtractBits(Ptr[idxE], 0, maskE);
return((valueE << (64 - shiftB)) | valueB);
}