root/lang/ruby/misc/shystd/lib/memo.rb @ 30719

#!/bin/ruby -Ku
# Copyright(c) 2007 URABE, Shyouhei.
#
# Permission is hereby granted, free of  charge, to any person obtaining a copy
# of  this code, to  deal in  the code  without restriction,  including without
# limitation  the rights  to  use, copy,  modify,  merge, publish,  distribute,
# sublicense, and/or sell copies of the code, and to permit persons to whom the
# code is furnished to do so, subject to the following conditions:
#
#        The above copyright notice and this permission notice shall be
#        included in all copies or substantial portions of the code.
#
# THE  CODE IS  PROVIDED "AS  IS",  WITHOUT WARRANTY  OF ANY  KIND, EXPRESS  OR
# IMPLIED,  INCLUDING BUT  NOT LIMITED  TO THE  WARRANTIES  OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE  AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
# AUTHOR  OR  COPYRIGHT  HOLDER BE  LIABLE  FOR  ANY  CLAIM, DAMAGES  OR  OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF  OR IN CONNECTION WITH  THE CODE OR THE  USE OR OTHER  DEALINGS IN THE
# CODE.

class Memoize
        def initialize
                @forward = Hash.new
                @reverse = Hash.new do |h, k| h.store k, Array.new end
                @key_finalizer   = lambda do |i| @forward.delete i end
                @value_finalizer = lambda do |i|
                        @reverse.delete(i).each do |j|
                                @forward.delete j
                        end
                end
        end

        def fetch k
                e = GC.disable
                j = @forward.fetch k.object_id do
                        return yield k
                end
                return ObjectSpace._id2ref j
        ensure
                GC.enable unless e
        end

        def store k, v
                i = k.object_id
                j = v.object_id
                ObjectSpace.define_finalizer k, @key_finalizer
                ObjectSpace.define_finalizer v, @value_finalizer
                @reverse[j].push i
                @forward.store i, j
        end
end


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