I was wondering if it is possible to

I was wondering if it is possible to pipe an (image) stream into FormData? I currently have this setup:

const { readable, writable } = new TransformStream();
req.body.pipeTo(writable);

const formData = new FormData();
formData.append(
  "file",
  readable,
  "test.jpg"
);

const response = await fetch(
  "...",
  {
    method: "POST",
    body: formData
  }
);

const { readable, writable } = new TransformStream();
req.body.pipeTo(writable);

const formData = new FormData();
formData.append(
  "file",
  readable,
  "test.jpg"
);

const response = await fetch(
  "...",
  {
    method: "POST",
    body: formData
  }
);

Which does not work - at least when uploading the image to Cloudflare Images, it says that the image has an incorrect mime type. If I read the whole body and append it into the form data, it does work as expected - but since that obviously isn't recommended because of the memory limit, I don't like that approach. I couldn't find anything on the interwebz

2 Replies

Manzoor Wani•7mo ago

Hey, did you manage to solve this problem? I am trying to solve as similar problem https://discord.com/channels/595317990191398933/1230170578674253886

Fabian•7mo ago

I think I was told that it's not possible but it should be no issue reading the whole body in my case since the files are <10MB. But yeah the streaming thing is generally an issue, I recently got stuck wanting to calculate a checksum of a stream and came to the conclusion with all of the current browser APIs and no additional APIs from Workers it's impossible if you don't read the whole body. I understand that everything should be streamed, since it makes sense, but if Cloudflare wants us to force using streams, then they should provide support for such stuff. I don't think this and my new cryptography problem are uncommon use-cases and they sadly will break if the incoming data is too big because of the memory limits. Granted: Upload limit is generally 100MB if you don't have Cloudflare Enterprise, but you can obviously donwload files from an external API that are bigger than 100MB.

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I was wondering if it is possible to