--- /dev/null
+require 'active_support/memoizable'
+
+module ActionController
+ module Http
+ class Headers < ::Hash
+ extend ActiveSupport::Memoizable
+
+ def initialize(*args)
+ if args.size == 1 && args[0].is_a?(Hash)
+ super()
+ update(args[0])
+ else
+ super
+ end
+ end
+
+ def [](header_name)
+ if include?(header_name)
+ super
+ else
+ super(env_name(header_name))
+ end
+ end
+
+ private
+ # Converts a HTTP header name to an environment variable name.
+ def env_name(header_name)
+ "HTTP_#{header_name.upcase.gsub(/-/, '_')}"
+ end
+ memoize :env_name
+ end
+ end
+end