Clippy's suggestion failed me, as `slice::take` only yields _at most_
the given number of elements, but `Vec::with_capacity` doesn't resize
in a way that it would yield `capacity` elements.
There is no benefit from making all operations on binary data read
in small, async steps directly from the file.
Since we know file sizes beforehand, it's less complex to read
the entire data blob into memory once, then operate on that
synchronously.