ALPHALINUX5/util/ALPHALINUX5/lib/ruby/1.6/weakref.rb

   1 # Weak Reference class that does not bother GCing.
   2 #
   3 # Usage:
   4 #   foo = Object.new
   5 #   foo = Object.new
   6 #   p foo.to_s                  # original's class
   7 #   foo = WeakRef.new(foo)
   8 #   p foo.to_s                  # should be same class
   9 #   ObjectSpace.garbage_collect
  10 #   p foo.to_s                  # should raise exception (recycled)
  11
  12 require "delegate"
  13
  14 class WeakRef<Delegator
  15
  16   class RefError<StandardError
  17   end
  18
  19   ID_MAP =  {}              # obj -> [ref,...]
  20   ID_REV_MAP =  {}          # ref -> obj
  21   @@final = lambda{|id|
  22     __old_status = Thread.critical
  23     Thread.critical = true
  24     begin
  25       rids = ID_MAP[id]
  26       if rids
  27         for rid in rids
  28           ID_REV_MAP[rid] = nil
  29         end
  30         ID_MAP[id] = nil
  31       end
  32       rid = ID_REV_MAP[id]
  33       if rid
  34         ID_REV_MAP[id] = nil
  35         ID_MAP[rid].delete(id)
  36         ID_MAP[rid] = nil if ID_MAP[rid].empty?
  37       end
  38     ensure
  39       Thread.critical = __old_status
  40     end
  41   }
  42
  43   def initialize(orig)
  44     super
  45     @__id = orig.__id__
  46     ObjectSpace.define_finalizer orig, @@final
  47     ObjectSpace.define_finalizer self, @@final
  48     __old_status = Thread.critical
  49     begin
  50       Thread.critical = true
  51       ID_MAP[@__id] = [] unless ID_MAP[@__id]
  52     ensure
  53       Thread.critical = __old_status
  54     end
  55     ID_MAP[@__id].push self.__id__
  56     ID_REV_MAP[self.id] = @__id
  57   end
  58
  59   def __getobj__
  60     unless ID_MAP[@__id]
  61       raise RefError, "Illegal Reference - probably recycled", caller(2)
  62     end
  63     ObjectSpace._id2ref(@__id)
  64   end
  65
  66   def weakref_alive?
  67     if ID_MAP[@__id]
  68       true
  69     else
  70       false
  71     end
  72   end
  73 end
  74
  75 if __FILE__ == $0
  76   require 'thread'
  77   foo = Object.new
  78   p foo.to_s                    # original's class
  79   foo = WeakRef.new(foo)
  80   p foo.to_s                    # should be same class
  81   ObjectSpace.garbage_collect
  82   p foo.to_s                    # should raise exception (recycled)
  83 end