5 # Middleware that enables conditional GET using If-None-Match and
6 # If-Modified-Since. The application should set either or both of the
7 # Last-Modified or Etag response headers according to RFC 2616. When
8 # either of the conditions is met, the response body is set to be zero
9 # length and the response status is set to 304 Not Modified.
11 # Applications that defer response body generation until the body's each
12 # message is received will avoid response body generation completely when
13 # a conditional GET matches.
15 # Adapted from Michael Klishin's Merb implementation:
16 # http://github.com/wycats/merb-core/tree/master/lib/merb-core/rack/middleware/conditional_get.rb
23 return @app.call(env) unless %w[GET HEAD].include?(env['REQUEST_METHOD'])
25 status, headers, body = @app.call(env)
26 headers = Utils::HeaderHash.new(headers)
27 if etag_matches?(env, headers) || modified_since?(env, headers)
29 headers.delete('Content-Type')
30 headers.delete('Content-Length')
33 [status, headers, body]
37 def etag_matches?(env, headers)
38 etag = headers['Etag'] and etag == env['HTTP_IF_NONE_MATCH']
41 def modified_since?(env, headers)
42 last_modified = headers['Last-Modified'] and
43 last_modified == env['HTTP_IF_MODIFIED_SINCE']