Why return a ReadCloser for reading, but not a WriteCloser for writing?

[leijurv]

Is there some reason why I shouldn't treat the compression step as a WriteCloser? Why does that return a public struct instead of an interface, like how decompression does?

Thanks!

[Viq111]

Hi @leijurv!

Yes we could return an io.WriteCloser, though it would mean the public attribute CompressionLevel would not be exposed anymore

If you want to use a io.WriteCloser, you can just do a:

var zstdWriter io.WriteCloser = NewWriter(w)

If you are talking about consistency, it's just to provide the attribute above ^ (for now, for future, we could also provide additional methods / attributes)

Hope this helps

[leijurv]

I'm not sure I understand. Why is the CompressionLevel public? Am I permitted to change it in the middle of writing?? (if so, that's awesome). If it's unchangeable then why public?

[Viq111]

It is indeed only public for read (get the value) but not for write (editing it won't change anything as the zstd_ctx is already created with the initial value: https://github.com/DataDog/zstd/blob/1.x/zstd_stream.go#L68)

That would definitely make sense to convert it to a method though to make the read-only explicit.
Since this is technically an API change though, we'll need to wait to switch to a major (2.x)