Add Source.close/1 callback to prevent hitting file descriptor limits

[1st8]

Hey evadne,

thank you very much for this great package, it works fantastically and is a pleasure to work with.

I found one issue where generating large archives from local files (1000+) would crash with reason: :emfile (i.e. too many open files).
File sources were simply never closed in the Encoder loop.

My fix is to add a new Source.close/1 callback, which is called after :eof is received from the source.
This also seemed to apply to the URL and Random source, so I implemented matching behaviours there, too.

The tests were a little hard to follow for me, so this is still a work in progress and any advice would be appreciated.
I verified that the problem is fixed regarding file sources, but did not test (other than running mix test - which is green) anything regarding URL or Random.

Let me know what you think!

Cheers,
Christoph

[evadne]

@1st8 what a good idea

[evadne]

@1st8 IMO the way to go is to ensure the read() implementation in sources will close whatever internal handle it has

e.g.

  @impl Source
  def read(source) do
    case IO.binread(source.device, get_chunk_size()) do
      :eof -> File.close(source.device); :eof
      data -> data
    end
  end

since all streams are read once only.

[evadne]

I’ve added the logic into #8 and merged

[1st8]

Cool, thanks!