Mapping bits to int

Question

I'm trying to map a uint64 array bit positions to an int array (see below). BitSet is a []uint64. Below is my code as currently setup. But I am wondering if there could be a std function in golang that can reduce this code. Other language has BitArray or other objects that makes life much easier.

So, in golang, do we have to code this? is there a better to do this?

// Indexes the index positions of '1' bits as an int array
func (b BitSet) Indexes() []int {
    // set up masks for bit ANDing
    masks := make([]uint64, _BitsPerUint64)
    for i := 0; i < _BitsPerUint64; i++ {
        masks[i] = (1 << uint(i))
    }
    // iterate bitset
    indexes := make([]int, 0, len(b)*4)
    for i := 0; i < len(b); i++ {
        for m := 0; m < _BitsPerUint64; m++ {
            if masks[m]&b[i] > 0 {
                indexes = append(indexes, i*_BitsPerUint64+m)
            }
        }
    }
    return indexes
}

Answer 1

func (b BitSet) Indexes() []int {
    retval := make([]int, 0, len(b)*64)
    for idx, value := range b {
        for i := 0; i < 64; i++ {
            if value & (1<<uint(i)) != 0 {
                retval = append(retval, idx*64 + i)
            }
        }
    }
    return retval
}