101 lines
2.7 KiB
Ruby
101 lines
2.7 KiB
Ruby
require "delegate"
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# WeakRef is a class to represent a reference to an object that is not seen by
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# the tracing phase of the garbage collector. This allows the referenced
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# object to be garbage collected as if nothing is referring to it. Because
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# WeakRef delegates method calls to the referenced object, it may be used in
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# place of that object, i.e. it is of the same duck type.
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#
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# Usage:
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#
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# foo = Object.new
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# foo = Object.new
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# p foo.to_s # original's class
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# foo = WeakRef.new(foo)
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# p foo.to_s # should be same class
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# ObjectSpace.garbage_collect
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# p foo.to_s # should raise exception (recycled)
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class WeakRef<Delegator
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# RefError is raised if an object cannot be referenced by a WeakRef.
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class RefError<StandardError
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end
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@@id_map = {} # obj -> [ref,...]
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@@id_rev_map = {} # ref -> obj
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@@final = lambda {|id|
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printf "final: %p\n", id
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__old_status = Thread.critical
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Thread.critical = true
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begin
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rids = @@id_map[id]
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if rids
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for rid in rids
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@@id_rev_map.delete(rid)
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end
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@@id_map.delete(id)
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end
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rid = @@id_rev_map[id]
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if rid
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@@id_rev_map.delete(id)
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@@id_map[rid].delete(id)
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@@id_map.delete(rid) if @@id_map[rid].empty?
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end
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ensure
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Thread.critical = __old_status
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end
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}
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# Create a new WeakRef from +orig+.
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def initialize(orig)
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@__id = orig.object_id
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printf "orig: %p\n", @__id
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ObjectSpace.define_finalizer orig, @@final
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ObjectSpace.define_finalizer self, @@final
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__old_status = Thread.critical
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begin
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Thread.critical = true
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@@id_map[@__id] = [] unless @@id_map[@__id]
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ensure
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Thread.critical = __old_status
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end
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@@id_map[@__id].push self.object_id
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@@id_rev_map[self.object_id] = @__id
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super
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end
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# Return the object this WeakRef references. Raises RefError if the object
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# has been garbage collected. The object returned is the object to which
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# method calls are delegated (see Delegator).
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def __getobj__
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unless @@id_rev_map[self.object_id] == @__id
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Kernel::raise RefError, "Illegal Reference - probably recycled", Kernel::caller(2)
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end
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begin
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ObjectSpace._id2ref(@__id)
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rescue RangeError
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Kernel::raise RefError, "Illegal Reference - probably recycled", Kernel::caller(2)
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end
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end
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def __setobj__(obj)
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end
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# Returns true if the referenced object still exists, and false if it has
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# been garbage collected.
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def weakref_alive?
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@@id_rev_map[self.object_id] == @__id
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end
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end
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if __FILE__ == $0
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# require 'thread'
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foo = Object.new
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p foo.to_s # original's class
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foo = WeakRef.new(foo)
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p foo.to_s # should be same class
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ObjectSpace.garbage_collect
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ObjectSpace.garbage_collect
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p foo.to_s # should raise exception (recycled)
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end
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