How would I support uploading using pre-signed URLs?

[majortom64]

If I had a server function that could be called with data from a file item (e.g. file name, WebKit Relative Path, file length and mime type) and would return a pre-signed URL, the method (PUT or POST), any additional headers and a success callback, how would I set this to call it for each file when it is ready to upload and then use the pre-signed URL for the upload?

Thanks!