# File lib/rack/etag.rb, line 10
10:     def call(env)
11:       status, headers, body = @app.call(env)
12: 
13:       if !headers.has_key?('ETag')
14:         digest, body = digest_body(body)
15:         headers['ETag'] = %("#{digest}")
16:       end
17: 
18:       [status, headers, body]
19:     end