CODEWITHSUNDEEP
haskell-snap-framework
r.sendecky
r.sendecky

Reputation: 10363

Snap binary files upload

I need to understand the file uploading process with Snap.

Given this form:

<form id="form" action="/files/upload" method="POST" enctype="multipart/form-data">
  <input type="file" id="files" name="files[]" multiple />
  <button type="submit"  onclick="handleFiles(e)">Upload</button>
</form>

Do I use the same functions like getPostParams to process binary files or do I use functions from Snap.Util.FileUploads?

I need to upload and save binary files like PDF in the database. The database driver will accept a ByteString to store a binary file.

I went through the Snap.Util.FileUploads but it does not look like it is what I need. So I am not sure how to process this in the handler?

Thanks.

EDIT

With some help from IRC I managed to come up with the below construct. I think it should be close to correct?? Well, it compiles and dumps the file to mongodb. I can also read it back. Although I don't quite understand the enumerators and Iteratee stuff ...

handleFiles :: AppHandler ()
handleFiles = do
  [file] <- handleMultipart defaultUploadPolicy $ \part -> do
    content <-  liftM BS.concat EL.consume
    return content
  let b = ["file" =: Binary file]
  r <- eitherWithDB $ insert "tests" b
  either (error . show) (const $ return () ) r

Upvotes: 2

Views: 490

Answers (1)

mightybyte
mightybyte

Reputation: 7272

Use Snap.Util.FileUploads. It's quite tricky to get file uploading right without leaving yourself open to security vulnerabilities. That FileUploads module has been carefully designed with this in mind.

The docs describe handleFileUploads pretty well. It "reads uploaded files into a temporary directory and calls a user handler to process them." You supply it with a handler with the type:

[(PartInfo, Either PolicyViolationException FilePath)] -> m a

handleFileUploads stores all the incoming files on disk subject to the policy you specify. Then it calls your handler and passes it the list of files handled.

Upvotes: 4

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