Added staging file previews support

3rd_party_apps/filetransfers/backends/default.py

@@ -0,0 +1,30 @@
+from django.http import HttpResponse
+from django.utils.encoding import smart_str
+
+def prepare_upload(request, url, **kwargs):
+    """Directly uploads to the given URL"""
+    return url, {}
+
+def serve_file(request, file, save_as, content_type, **kwargs):
+    """
+    Serves the file in chunks for efficiency reasons, but the transfer still
+    goes through Django itself, so it's much worse than using the web server,
+    but at least it works with all configurations.
+    """
+    response = HttpResponse(ChunkedFile(file), content_type=content_type)
+    if save_as:
+        response['Content-Disposition'] = smart_str(u'attachment; filename=%s' % save_as)
+    if file.size is not None:
+        response['Content-Length'] = file.size
+    return response
+
+def public_download_url(file, **kwargs):
+    """No public download URL"""
+    return None
+
+class ChunkedFile(object):
+    def __init__(self, file):
+        self.file = file
+
+    def __iter__(self):
+        return self.file.chunks()