Function window_samples 

fn window_samples<'a>(
    values: &'a Float64Array,
    has_nulls: bool,
    offset: usize,
    len: usize,
    samples: &'a mut Vec<f64>,
) -> &'a [f64]

Returns the samples of the window [offset, offset + len), collecting the non-null ones into samples when the backing array has nulls and borrowing the slice otherwise.