vendor/rails/actionpack/lib/action_controller/vendor/rack-1.0/rack/conditionalget.rb

   1 require 'rack/utils'
   2
   3 module Rack
   4
   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.
  10   #
  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.
  14   #
  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
  17   class ConditionalGet
  18     def initialize(app)
  19       @app = app
  20     end
  21
  22     def call(env)
  23       return @app.call(env) unless %w[GET HEAD].include?(env['REQUEST_METHOD'])
  24
  25       status, headers, body = @app.call(env)
  26       headers = Utils::HeaderHash.new(headers)
  27       if etag_matches?(env, headers) || modified_since?(env, headers)
  28         status = 304
  29         body = []
  30       end
  31       [status, headers, body]
  32     end
  33
  34   private
  35     def etag_matches?(env, headers)
  36       etag = headers['Etag'] and etag == env['HTTP_IF_NONE_MATCH']
  37     end
  38
  39     def modified_since?(env, headers)
  40       last_modified = headers['Last-Modified'] and
  41         last_modified == env['HTTP_IF_MODIFIED_SINCE']
  42     end
  43   end
  44
  45 end