Factor out unique id generator. Expose cgi to session store.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@6174 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/lib/action_controller/cgi_ext/session_performance_fix.rb

@@ -3,28 +3,40 @@
 # when serving requests from a long-lived process.
 #
 # http://railsexpress.de/blog/articles/2005/11/22/speeding-up-the-creation-of-new-sessions
+#
+# Also expose the CGI instance to session stores.
 require 'cgi/session'
 require 'digest/md5'
 
 class CGI
   class Session #:nodoc:
+    # Generate an MD5 hash including the time, a random number, the process id,
+    # and a constant string. This is used to generate session ids but may be
+    # reused elsewhere.
+    def self.generate_unique_id(constant = 'foobar')
+      md5 = Digest::MD5.new
+      now = Time.now
+      md5 << now.to_s
+      md5 << String(now.usec)
+      md5 << String(rand(0))
+      md5 << String($$)
+      md5 << constant
+      md5.hexdigest
+    end
+
+    # Make the CGI instance available to session stores.
+    attr_reader :cgi
+    alias_method :initialize_without_cgi_reader, :initialize
+    def initialize(cgi, options = {})
+      @cgi = cgi
+      initialize_without_cgi_reader(cgi, options)
+    end
+
     private
       # Create a new session id.
-      #
-      # The session id is an MD5 hash based upon the time,
-      # a random number, and a constant string.  This routine
-      # is used internally for automatically generated
-      # session ids.
       def create_new_id
-        md5 = Digest::MD5::new
-        now = Time::now
-        md5.update(now.to_s)
-        md5.update(String(now.usec))
-        md5.update(String(rand(0)))
-        md5.update(String($$))
-        md5.update('foobar')
         @new_session = true
-        md5.hexdigest
+        self.class.generate_unique_id
       end
   end
 end