Bit flag array check if all bits in a range are set.cs

bool AreAllBitsInRangeSet(int from, int end) //check range from (inclusive) to end (exclusive)
{
    int f64 = (from&~63), e64 = (end&~63);
    for (int i = f64 + 64; i < e64; i += 64) { if ((ULongBitArray[i>>6]) != ~0UL) return false; }
    ulong fMask = (~0UL<<(from-f64)), eMask = ((1UL<<(end-e64))-1);
    if (f64 == e64) { fMask = (fMask&eMask); eMask = 0; }
    return ((ULongBitArray[f64>>6] & fMask) == fMask && (eMask == 0 || (ULongBitArray[e64>>6] & eMask) != eMask));
}