class Rack::ETag

def call(env)
  status, headers, body = response = @app.call(env)
  if etag_status?(status) && body.respond_to?(:to_ary) && !skip_caching?(headers)
    body = body.to_ary
    digest = digest_body(body)
    headers[ETAG_STRING] = %(W/"#{digest}") if digest
    # Body was modified, so we need to re-assign it:
    response[2] = body
  end
  unless headers[CACHE_CONTROL]
    if digest
      headers[CACHE_CONTROL] = @cache_control if @cache_control
    else
      headers[CACHE_CONTROL] = @no_cache_control if @no_cache_control
    end
  end
  response
end