Parsing IO stream for file upload

[kennym]

I am having trouble parsing the IO stream when asynchronously uploading a file, while using the code from async_upload.rb in the examples directory.

  def on_body(env, data)
    env.logger.info 'received data: ' + data
    (env['async-body'] ||= '') << data
  end

>> ::Rack::Utils::Multipart.parse_multipart(env["async-body"])
nil

My async-body looks as follows:

env["async-body"]

"------WebKitFormBoundarybZBSwB8ypRDnLb9V\r\nContent-Disposition: form-data; name=\"body\"; filename=\"hablar-con-tus-hijos-sobre-problemas-financieros-1.jpg\"\r\nContent-Type: image/jpeg\r\n\r\n\xFF\xD8\xFF\xE0\x00\x10JFIF\x00\x01\x01\x00\x00\x01\x00\x01\x00\x00\xFF\xFE\x00;CREATOR: gd-jpeg v1.0 (using IJG JPEG v62), quality = 80\n\xFF\xDB\x00C\x00\x06\x04\x05\x06\x05\x04\x06\x06\x05\x06\a\a\x06\b\n\x10\n\n\t\t\n\x14\x0E\x0F\f\x10\x17\x14\x18\x18\x17\x14\x16\x16\x1A\x1D%\x1F\x1A\e#\x1C\x16\x16 , #&')*)\x19\x1F-0-(0%()(\xFF\xDB\x00C\x01\a\a\a\n\b\n\x13\n\n\x13(\x1A\x16\x1A((((((((((((((((((((((((((((((((((((((((((((((((((\xFF\xC0\x00\x11\b\x01\xB7\x02v\x03\x01\"\x00\x02\x11\x01\x03\x11\x01\xFF\xC[ snip ]
\xD2\x8A)\x88i\"\x93#\xD2\x8A(\x10\xD2E\x03\x1E\x94Q@\bqI\x91E\x14\xC0BE!4Q@\x84\xC8\xA6\x93E\x14\x00\xC2j'aE\x14\x01\x1374QE\x00\x7F\xFF\xD9\r\n------WebKitFormBoundarybZBSwB8ypRDnLb9V--\r\n"`

Are there any strategies on this one?

I've used Postman for Chrome as a HTTP client, and curl.

Here's the full response env: http://pastebin.com/a7m7rjYd

[kennym]

So, I have been able to parse out the images by using this:

env["async-body"].split("\r\n")[-2]

Still, I am not sure how that is going to work in production, and I am still open for suggestions.

[igrigorik]

Well, that's basically right, except you can probably do something smarter by only scanning for boundary on last received chunk and then invoking the split... Also, if you're streaming a large upload, you may want to consider streaming that to a temp file on disk, or something similar.