lib/tzinfo/ruby_core_support.rb


#--

# Copyright (c) 2008-2013 Philip Ross

# 

# Permission is hereby granted, free of charge, to any person obtaining a copy

# of this software and associated documentation files (the "Software"), to deal

# in the Software without restriction, including without limitation the rights

# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

# copies of the Software, and to permit persons to whom the Software 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 Software.

#

# THE SOFTWARE 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

# AUTHORS OR COPYRIGHT HOLDERS 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 SOFTWARE OR THE USE OR OTHER DEALINGS IN

# THE SOFTWARE.

#++


require 'date'
require 'rational' unless defined?(Rational)

module TZInfo
  
  # Methods to support different versions of Ruby.

  #

  # @private

  module RubyCoreSupport #:nodoc:

  
    # Use Rational.new! for performance reasons in Ruby 1.8.

    # This has been removed from 1.9, but Rational performs better.        

    if Rational.respond_to? :new!
      def self.rational_new!(numerator, denominator = 1)
        Rational.new!(numerator, denominator)
      end
    else
      def self.rational_new!(numerator, denominator = 1)
        Rational(numerator, denominator)
      end
    end
    
    # Ruby 1.8.6 introduced new! and deprecated new0.

    # Ruby 1.9.0 removed new0.

    # Ruby trunk revision 31668 removed the new! method.

    # Still support new0 for better performance on older versions of Ruby (new0 indicates

    # that the rational has already been reduced to its lowest terms).

    # Fallback to jd with conversion from ajd if new! and new0 are unavailable.

    if DateTime.respond_to? :new!
      def self.datetime_new!(ajd = 0, of = 0, sg = Date::ITALY)
        DateTime.new!(ajd, of, sg)
      end
    elsif DateTime.respond_to? :new0
      def self.datetime_new!(ajd = 0, of = 0, sg = Date::ITALY)
        DateTime.new0(ajd, of, sg)
      end
    else
      HALF_DAYS_IN_DAY = rational_new!(1, 2)

      def self.datetime_new!(ajd = 0, of = 0, sg = Date::ITALY)
        # Convert from an Astronomical Julian Day number to a civil Julian Day number.

        jd = ajd + of + HALF_DAYS_IN_DAY
        
        # Ruby trunk revision 31862 changed the behaviour of DateTime.jd so that it will no

        # longer accept a fractional civil Julian Day number if further arguments are specified.

        # Calculate the hours, minutes and seconds to pass to jd.

        
        jd_i = jd.to_i
        jd_i -= 1 if jd < 0
        hours = (jd - jd_i) * 24
        hours_i = hours.to_i
        minutes = (hours - hours_i) * 60
        minutes_i = minutes.to_i
        seconds = (minutes - minutes_i) * 60
        
        DateTime.jd(jd_i, hours_i, minutes_i, seconds, of, sg)
      end
    end
  end
end