Hello. I couldn't find how to send multipart form ...

# multiplatform

[Rafał Kuźmiński]

Hello. I couldn't find how to send multipart form in Kotlin Multiplatform using Ktor and native "files". Issue is that now I'm reading javascript File to ByteArray and Android / iOS File to ByteArray which
1. Takes a lot of time
2. Might cause OOM
Is there a way do to it with streams? I saw that append method in Ktor has options like InputProvider or ChannelProvider or Source but I have no idea how to use it

[Aleksei Tirman [JB]]

Unfortunately, you have to implement an adapter that reads a file asynchronously for each platform. On iOS, the native dispatch_read method can be used for that (https://stackoverflow.com/a/78736380/13963150).

[Rafał Kuźmiński]

And which abstraction should I use for my adapter? Any of those three i mentioned is okey? One of them if preferred?

[Aleksei Tirman [JB]]

You'd better use the ChannelProvider , although you'll have to slightly change the implementation for iOS.
Unfortunately, browser environments don't support request body streaming, so the only solution with Ktor is to read the entire body into memory.

[Rafał Kuźmiński]

So when we send form in plain JS / html environment with files then all files are loaded into memory? It might be silly question but I wasn't doing frontend development before Kotlin JS

[Aleksei Tirman [JB]]

No, they are not. The browser knows how to stream files and similar objects it operates on, but does not provide a generic interface to adapt any object for streaming. The problem is that the multipart methods reside in the common module, which is unaware of the platform-specific objects.

[Rafał Kuźmiński]

I see, so if we are using Kotlin JS for forms then we have problem? 😉 I would have to rewrite sending part to plain JS?

[Aleksei Tirman [JB]]

That's correct.

[Rafał Kuźmiński]

But can I still use Kotlin and fetch API?

[Aleksei Tirman [JB]]

Yes, you can.

[Rafał Kuźmiński]

Thanks, I will try to use some expect actual magic to handle it on browser site