Function masked_bytes 

fn masked_bytes<'a, T: ByteArrayType>(
    array: &'a GenericByteArray<T>,
    mask: &BooleanBuffer,
) -> Vec<(usize, Option<&'a [u8]>)>

Compute get_masked_values for a [GenericByteArray]

Note: this does not check the null mask and will return values contained in null slots