Fix marshal incompatibility between Date/DateTime on 1.8 and 1.9

ruby19_date_marshal.rb

require 'date'

class Date
  if RUBY_VERSION < '1.9'
    ## accept 1.9 marshaled data on 1.8
    ## based on ext/date/date_core.c d_lite_marshal_dump_old
    def marshal_load(data)
      nth, jd, df, sf, of, @sg = data

      real_jd =
        if nth == 0
          jd
        else
          jd + nth * (0xfffffff / 71149239 * 71149239)
        end

      if jd == 0 && sf == 0 && of == 0
        @ajd = Rational.new!(real_jd * 2 - 1, 2)
      else
        df -= 86400 / 2
        if df != 0
          real_jd += Rational.new!(df, 86400)
        end
        if sf != 0
          real_jd += Rational.new!(sf, 86400 * 1000000000)
        end

        @ajd = real_jd
        @of = Rational.new!(of, 86400)
      end
    end
  else
    ## accept 1.8 marshaled data on 1.9
    ## based on ruby/1.8/date.rb Date._load
    class ::FakeRational
      def to_r
        Rational(@numerator, @denominator)
      end
    end
    def self._load(str)
      ajd, of, sg = Marshal.load(str.gsub("\rRational","\x11FakeRational"))
      ajd = ajd.to_r if ajd.is_a?(FakeRational)
      of  = of.to_r  if  of.is_a?(FakeRational)
      new.marshal_load([ajd, of, sg])
    end
  end
end

if __FILE__ == $0
  require 'test/unit'

  class MarshalCompatTest < Test::Unit::TestCase
    def setup
      # Marshal.dump(Date.today)
      @date_obj = Date.parse('2013-02-05')
      @date_18  = "\004\bu:\tDate=\004\b[\bo:\rRational\a:\021@denominatori\a:\017@numeratori\003\021\366Ji\000i\003\031\025#"
      @date_19  = "\x04\bU:\tDate[\vi\x00i\x03\t{%i\x00i\x00i\x00f\f2299161"

      # Marshal.dump(DateTime.now)
      @datetime_obj = DateTime.parse('2013-02-05T19:33:03.123456789-08:00')
      @datetime_18  = "\004\bu:\rDateTimeV\004\b[\bo:\rRational\a:\021@denominatorl+\b\000\000\305\2051\032:\017@numeratorl+\n\a\241\2477u\035\277\325\003\000o;\000\a;\006i\b;\ai\372i\003\031\025#"
      @datetime_19  = "\x04\bU:\rDateTime[\vi\x00i\x03\n{%i\x02\xEF1i\x04\x15\xCD[\ai\xFE\x80\x8Ff\f2299161"
    end

    def test_decode_date
      assert_equal @date_obj, Marshal.load(@date_18)
      assert_equal @date_obj, Marshal.load(@date_19)
    end

    def test_decode_date_time
      assert_equal @datetime_obj, Marshal.load(@datetime_18)
      assert_equal @datetime_obj, Marshal.load(@datetime_19)
    end
  end
end