--- /dev/null
+class Module
+ # Synchronize access around a method, delegating synchronization to a
+ # particular mutex. A mutex (either a Mutex, or any object that responds to
+ # #synchronize and yields to a block) must be provided as a final :with option.
+ # The :with option should be a symbol or string, and can represent a method,
+ # constant, or instance or class variable.
+ # Example:
+ # class SharedCache
+ # @@lock = Mutex.new
+ # def expire
+ # ...
+ # end
+ # synchronize :expire, :with => :@@lock
+ # end
+ def synchronize(*methods)
+ options = methods.extract_options!
+ unless options.is_a?(Hash) && with = options[:with]
+ raise ArgumentError, "Synchronization needs a mutex. Supply an options hash with a :with key as the last argument (e.g. synchronize :hello, :with => :@mutex)."
+ end
+
+ methods.each do |method|
+ aliased_method, punctuation = method.to_s.sub(/([?!=])$/, ''), $1
+
+ if method_defined?("#{aliased_method}_without_synchronization#{punctuation}")
+ raise ArgumentError, "#{method} is already synchronized. Double synchronization is not currently supported."
+ end
+
+ module_eval(<<-EOS, __FILE__, __LINE__)
+ def #{aliased_method}_with_synchronization#{punctuation}(*args, &block)
+ #{with}.synchronize do
+ #{aliased_method}_without_synchronization#{punctuation}(*args, &block)
+ end
+ end
+ EOS
+
+ alias_method_chain method, :synchronization
+ end
+ end
+end