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# encoding: utf-8
module IceNine
# Protect against infinite recursion
#
# @private
class RecursionGuard
# Protects against infinite recursion by never yielding with the same
# object more than once.
class ObjectSet < self
# Initialize a recursion guard
#
# @return [undefined]
def initialize
@object_ids = {}
end
# Guard against recursively calling a block with the same object
#
# @example
# recursion_guard = IceNine::RecursionGuard::ObjectSet.new
# recursion_guard.guard(object) do
# logic_which_may_be_recursively_called_with_object(recursion_guard)
# end
#
# @param [Object] object
#
# @return [Object]
def guard(object)
caller_object_id = object.__id__
return object if @object_ids.key?(caller_object_id)
@object_ids[caller_object_id] = nil
yield
end
end # ObjectSet
# Protects against infinite recursion by not yielding with frozen objects
class Frozen < self
# Guard against recursively calling a block with the same frozen object
#
# @param [Object] object
#
# @return [Object]
def guard(object)
return object if object.frozen?
yield
end
end # Frozen
end # RecursionGuard
end # IceNine
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