JezK
Edit File: weakref.rb
require "delegate" require 'thread' # Weak Reference class that allows a referenced object to be # garbage-collected. A WeakRef may be used exactly like the object it # references. # # Usage: # # foo = Object.new # foo = Object.new # p foo.to_s # original's class # foo = WeakRef.new(foo) # p foo.to_s # should be same class # ObjectSpace.garbage_collect # p foo.to_s # should raise exception (recycled) class WeakRef < Delegator ## # RefError is raised when a referenced object has been recycled by the # garbage collector class RefError < StandardError end @@id_map = {} # obj -> [ref,...] @@id_rev_map = {} # ref -> obj @@mutex = Mutex.new @@final = lambda {|id| @@mutex.synchronize { rids = @@id_map[id] if rids for rid in rids @@id_rev_map.delete(rid) end @@id_map.delete(id) end rid = @@id_rev_map[id] if rid @@id_rev_map.delete(id) @@id_map[rid].delete(id) @@id_map.delete(rid) if @@id_map[rid].empty? end } } ## # Creates a weak reference to +orig+ def initialize(orig) @__id = orig.object_id ObjectSpace.define_finalizer orig, @@final ObjectSpace.define_finalizer self, @@final @@mutex.synchronize { @@id_map[@__id] = [] unless @@id_map[@__id] } @@id_map[@__id].push self.object_id @@id_rev_map[self.object_id] = @__id super end def __getobj__ # :nodoc: unless @@id_rev_map[self.object_id] == @__id Kernel::raise RefError, "Invalid Reference - probably recycled", Kernel::caller(2) end begin ObjectSpace._id2ref(@__id) rescue RangeError Kernel::raise RefError, "Invalid Reference - probably recycled", Kernel::caller(2) end end def __setobj__(obj) # :nodoc: end ## # Returns true if the referenced object is still alive. def weakref_alive? @@id_rev_map[self.object_id] == @__id end end if __FILE__ == $0 # require 'thread' foo = Object.new p foo.to_s # original's class foo = WeakRef.new(foo) p foo.to_s # should be same class ObjectSpace.garbage_collect ObjectSpace.garbage_collect p foo.to_s # should raise exception (recycled) end