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# Weak Reference class that does not bother GCing.
#
# 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)
require "delegate"
require 'thread'
class WeakRef < Delegator
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
}
}
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__
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)
end
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
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