1  #--
   2  # Copyright (c) 2006 Philip Ross
   3  # 
   4  # Permission is hereby granted, free of charge, to any person obtaining a copy
   5  # of this software and associated documentation files (the "Software"), to deal
   6  # in the Software without restriction, including without limitation the rights
   7  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   8  # copies of the Software, and to permit persons to whom the Software is
   9  # furnished to do so, subject to the following conditions:
  10  # 
  11  # The above copyright notice and this permission notice shall be included in all
  12  # copies or substantial portions of the Software.
  13  #
  14  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  15  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  16  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  17  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  18  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  19  # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  20  # THE SOFTWARE.
  21  #++
  22 
  23  module TZInfo
  24    # Represents an offset defined in a Timezone data file.
  25    class TimezoneOffsetInfo #:nodoc:
  26      # The base offset of the timezone from UTC in seconds.
  27      attr_reader :utc_offset
  28      
  29      # The offset from standard time for the zone in seconds (i.e. non-zero if 
  30      # daylight savings is being observed).
  31      attr_reader :std_offset
  32      
  33      # The total offset of this observance from UTC in seconds 
  34      # (utc_offset + std_offset).
  35      attr_reader :utc_total_offset
  36      
  37      # The abbreviation that identifies this observance, e.g. "GMT" 
  38      # (Greenwich Mean Time) or "BST" (British Summer Time) for "Europe/London". The returned identifier is a 
  39      # symbol.
  40      attr_reader :abbreviation
  41      
  42      # Constructs a new TimezoneOffsetInfo. utc_offset and std_offset are
  43      # specified in seconds.
  44      def initialize(utc_offset, std_offset, abbreviation)
  45        @utc_offset = utc_offset
  46        @std_offset = std_offset      
  47        @abbreviation = abbreviation
  48        
  49        @utc_total_offset = @utc_offset + @std_offset
  50      end
  51      
  52      # True if std_offset is non-zero.
  53      def dst?
  54        @std_offset != 0
  55      end
  56      
  57      # Converts a UTC DateTime to local time based on the offset of this period.
  58      def to_local(utc)
  59        TimeOrDateTime.wrap(utc) {|wrapped|
  60          wrapped + @utc_total_offset
  61        }
  62      end
  63      
  64      # Converts a local DateTime to UTC based on the offset of this period.
  65      def to_utc(local)
  66        TimeOrDateTime.wrap(local) {|wrapped|
  67          wrapped - @utc_total_offset
  68        }
  69      end
  70      
  71      # Returns true if and only if toi has the same utc_offset, std_offset
  72      # and abbreviation as this TimezoneOffsetInfo.
  73      def ==(toi)
  74        toi.respond_to?(:utc_offset) && toi.respond_to?(:std_offset) && toi.respond_to?(:abbreviation) &&
  75          utc_offset == toi.utc_offset && std_offset == toi.std_offset && abbreviation == toi.abbreviation
  76      end
  77      
  78      # Returns true if and only if toi has the same utc_offset, std_offset
  79      # and abbreviation as this TimezoneOffsetInfo.
  80      def eql?(toi)
  81        self == toi
  82      end
  83      
  84      # Returns a hash of this TimezoneOffsetInfo.
  85      def hash
  86        utc_offset.hash ^ std_offset.hash ^ abbreviation.hash
  87      end
  88      
  89      # Returns internal object state as a programmer-readable string.
  90      def inspect
  91        "#<#{self.class}: #@utc_offset,#@std_offset,#@abbreviation>"
  92      end
  93    end
  94  end