cached_pstore.rb

# = CachedPStore -- PStore extension w/ cache mechanism
#
# Copyright (C) 2010, MATSUOKA Kohei
# You can redistribute it and/or modify it under GPL2.
#
# == Usage examle:
#  
#  require 'cached_pstore'
#
#  db = CachedPStore.new('test.dat', :expire => 3600) {|db, key|
#    # update_proc
#    db[key] = 'update value'
#  }
#  db.transaction {|db|
#    db[:key1] = 'value1'
#    puts db[:key1]  # => 'value1'
#  }
#
#  ### Some time later... ###
#
#  db.transaction {|db|
#    # value is expired, it calls update_proc
#    puts db[:key]   # => 'update value'
#  }
#
require 'pstore'

class CachedPStore < PStore
	def initialize(filename, options = {}, &update_proc)
		@timeout = options[:timeout] || 60 * 60
		@version = options[:version] || 1
		@update_proc = update_proc
		super(filename)
	end

	def [](name)
		value = super(name) || {}
		expired = (value[:updated_at] == nil ||
					  value[:updated_at] + @timeout < Time.now ||
					  value[:version] < @version)
		if expired && @update_proc
			self[name] = @update_proc.call(name)
		else
			value[:entity]
		end
	end

	def []=(name, value)
		super(name, {
			:version => @version,
			:updated_at => Time.now,
			:entity => value
		})
	end
end

cached_pstore_spec.rb

# -*- coding: utf-8 -*-
#
require 'cached_pstore'
require 'fileutils'

describe CachedPStore do
	before(:each) do
		File.unlink('test.dat') if File.exist?('test.dat')
	end

	it "初期化されていないキーを読み込むと、更新ブロックで初期化されること" do
		CachedPStore.new('test.dat') {|db, key|
			'default'
		}.transaction {|db|
			db[:uninitialized].should == 'default'
		}
	end

	it "有効期限が切れると更新ブロックで更新されること" do
		db = CachedPStore.new('test.dat', :timeout => 1) {|db, key|
			'default'
		}
		db.transaction {|db|
			db[:initialized] = 'initialized'
			db[:initialized].should == 'initialized'
		}
		sleep 1
		db.transaction {|db|
			db[:initialized].should == 'default'
		}
	end

	it "初期化ブロックが渡されない場合は有効期限が切れても更新されない" do
		db = CachedPStore.new('test.dat', :timeout => 1)
		db.transaction {|db|
			db[:initialized] = 'initialized'
			db[:initialized].should == 'initialized'
		}
		sleep 1
		db.transaction {|db|
			db[:initialized].should == 'initialized'
		}
	end
end