from django.http import HttpResponse
from django.utils.encoding import smart_str

def serve_file(request, file, save_as, content_type, **kwargs):
    """Lets the web server serve the file using the X-Sendfile extension"""
    response = HttpResponse(content_type=content_type)
    response['X-Sendfile'] = file.path
    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