Get an array of the bit positions within a 64-bit integer

Question

OK, it may sound a bit complicated, but this is what I\'m trying to do :

• Take e.g. 10101010101
• And return { 0, 2, 4, 6, 8, 10 }

Answer 1

Here is another suggestion that can be profiled (can be combined with other suggestions for further optimization). Note, the loop here is O(number of set bits).

vector bits_set (UINT64 data) 
{
    UINT n;
    vector res;
    res.reserve(64);
    for (n = 0; data != 0; n++, data &= (data - 1))
    {
        res.push_back(log2(data & ~(data-1)));
    }
    return res;
}