Question

I’m writing an obj-c app and would like to upload a binary file a few megs in size to my appengine server (python). I’m guessing I need to use the blob entity for this, but am unsure how to go about doing this. I’ve been using http requests and responses to send and receive data up to now, but they’ve been encoded in strings. Can someone advise how I’d go about doing the same with blobs from an obj-c app? I see some examples that involve http requests but they seem geared toward web page and I’m not terribly familiar with it. Are there any decent tutorials or walkthroughs perhaps?

I’m basically not completely sure, if I’m supposed to encode it into the http request and send it back through the response, how to get the binary data into the http string from the client and how to send it back properly from the server when downloading my binary data. I’m thinking perhaps the approach has to be totally different from what I’m used to with encoding values into my request in the param1=val&param2=val2 style format but uncertain.

Should I be using the blobstore service for this? One important note is that I’ve heard there is a 1 meg limit on blobs, but I have audio files 2-3 megs in size that I need to store (at the very least 1.8 megs).

Answer 1

I recently had to do something similar, though it was binary data over a socket connection. To the client using XML, to the server as a data stream. I ended up base64 encoding the binary data when sending it back and forth. It’s a bit wordy but especially on the client side it made things easier to deal with, no special characters to worry about in my XML. I then translated it with NSData into a real binary format. I used this code to do the encoding and decoding, search for “cyrus” to find the snippet I used, there are a few that would work here.

In your case I would change your http request to a post data call rather than putting it all in the URL. If you’re not sure what the difference is, have a look here.

I’m not as familiar with python, but you could try here for help on that end.

Hope that helps.

Edit – it looks like blobs are the way to go. Have a look at this link for the string/blob type as well as this link for more info on working with the blob.