1 files changed, 99 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/http/headers.rb b/actionpack/lib/action_dispatch/http/headers.rb
new file mode 100644
index 0000000000..bc5410dc38
--- /dev/null
+++ b/actionpack/lib/action_dispatch/http/headers.rb
@@ -0,0 +1,99 @@
+module ActionDispatch
+  module Http
+    # Provides access to the request's HTTP headers from the environment.
+    #
+    #   env     = { "CONTENT_TYPE" => "text/plain" }
+    #   headers = ActionDispatch::Http::Headers.new(env)
+    #   headers["Content-Type"] # => "text/plain"
+    class Headers
+      CGI_VARIABLES = Set.new(%W[
+        AUTH_TYPE
+        CONTENT_LENGTH
+        CONTENT_TYPE
+        GATEWAY_INTERFACE
+        HTTPS
+        PATH_INFO
+        PATH_TRANSLATED
+        QUERY_STRING
+        REMOTE_ADDR
+        REMOTE_HOST
+        REMOTE_IDENT
+        REMOTE_USER
+        REQUEST_METHOD
+        SCRIPT_NAME
+        SERVER_NAME
+        SERVER_PORT
+        SERVER_PROTOCOL
+        SERVER_SOFTWARE
+      ]).freeze
+
+      HTTP_HEADER = /\A[A-Za-z0-9-]+\z/
+
+      include Enumerable
+      attr_reader :env
+
+      def initialize(env = {}) # :nodoc:
+        @env = env
+      end
+
+      # Returns the value for the given key mapped to @env.
+      def [](key)
+        @env[env_name(key)]
+      end
+
+      # Sets the given value for the key mapped to @env.
+      def []=(key, value)
+        @env[env_name(key)] = value
+      end
+
+      def key?(key)
+        @env.key? env_name(key)
+      end
+      alias :include? :key?
+
+      # Returns the value for the given key mapped to @env.
+      #
+      # If the key is not found and an optional code block is not provided,
+      # raises a <tt>KeyError</tt> exception.
+      #
+      # If the code block is provided, then it will be run and
+      # its result returned.
+      def fetch(key, *args, &block)
+        @env.fetch env_name(key), *args, &block
+      end
+
+      def each(&block)
+        @env.each(&block)
+      end
+
+      # Returns a new Http::Headers instance containing the contents of
+      # <tt>headers_or_env</tt> and the original instance.
+      def merge(headers_or_env)
+        headers = Http::Headers.new(env.dup)
+        headers.merge!(headers_or_env)
+        headers
+      end
+
+      # Adds the contents of <tt>headers_or_env</tt> to original instance
+      # entries; duplicate keys are overwritten with the values from
+      # <tt>headers_or_env</tt>.
+      def merge!(headers_or_env)
+        headers_or_env.each do |key, value|
+          self[env_name(key)] = value
+        end
+      end
+
+      private
+      # Converts a HTTP header name to an environment variable name if it is
+      # not contained within the headers hash.
+      def env_name(key)
+        key = key.to_s
+        if key =~ HTTP_HEADER
+          key = key.upcase.tr('-', '_')
+          key = "HTTP_" + key unless CGI_VARIABLES.include?(key)
+        end
+        key
+      end
+    end
+  end
+end