if "Trident/" in request.META['HTTP_USER_AGENT']:
    content_disposition = 'attachment; filename="%s"' % iri_to_uri(smart_bytes(filename))
elif "Safari/" in request.META['HTTP_USER_AGENT'] and not
     "Chrome/" in request.META['HTTP_USER_AGENT']:
    content_disposition = b'attachment; filename="%s"' % filename.encode("utf-8")
else:
    filename_encoded = ""
    str_chunk_size = 30
    for i in range(int(math.ceil(len(filename)/float(str_chunk_size)))):
        if i != 0:
            filename_encoded += " =?UTF-8?B?"
        else:
            filename_encoded += "=?UTF-8?B?"
        filename_encoded += base64.b64encode(smart_bytes(filename[i*str_chunk_size: (i+1)*str_chunk_size])) + "?="
    content_disposition = 'attachment; filename="%s"' % filename_encoded

response = HttpResponse(content_type='application/force-download; charset=utf-8')
response['Content-Disposition'] = content_disposition
response['X-Sendfile'] = smart_bytes(os.path.join(STORAGE_ROOT, f.storage_name))
response["Content-Length"] = f.size
return response