181 lines
6.8 KiB
Ruby
181 lines
6.8 KiB
Ruby
# A value object representing a time zone. A time zone is simply a named
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# offset (in seconds) from GMT. Note that two time zone objects are only
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# equivalent if they have both the same offset, and the same name.
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#
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# A TimeZone instance may be used to convert a Time value to the corresponding
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# time zone.
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#
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# The class also includes #all, which returns a list of all TimeZone objects.
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class TimeZone
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include Comparable
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attr_reader :name, :utc_offset
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# Create a new TimeZone object with the given name and offset. The offset is
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# the number of seconds that this time zone is offset from UTC (GMT). Seconds
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# were chosen as the offset unit because that is the unit that Ruby uses
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# to represent time zone offsets (see Time#utc_offset).
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def initialize(name, utc_offset)
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@name = name
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@utc_offset = utc_offset
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end
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# Returns the offset of this time zone as a formatted string, of the
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# format "+HH:MM". If the offset is zero, this returns the empty
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# string. If +colon+ is false, a colon will not be inserted into the
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# result.
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def formatted_offset( colon=true )
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return "" if utc_offset == 0
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sign = (utc_offset < 0 ? -1 : 1)
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hours = utc_offset.abs / 3600
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minutes = (utc_offset.abs % 3600) / 60
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"%+03d%s%02d" % [ hours * sign, colon ? ":" : "", minutes ]
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end
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# Compute and return the current time, in the time zone represented by
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# +self+.
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def now
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adjust(Time.now)
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end
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# Return the current date in this time zone.
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def today
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now.to_date
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end
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# Adjust the given time to the time zone represented by +self+.
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def adjust(time)
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time = time.to_time
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time + utc_offset - time.utc_offset
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end
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# Reinterprets the given time value as a time in the current time
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# zone, and then adjusts it to return the corresponding time in the
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# local time zone.
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def unadjust(time)
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time = Time.local(*time.to_time.to_a)
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time - utc_offset + time.utc_offset
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end
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# Compare this time zone to the parameter. The two are comapred first on
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# their offsets, and then by name.
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def <=>(zone)
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result = (utc_offset <=> zone.utc_offset)
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result = (name <=> zone.name) if result == 0
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result
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end
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# Returns a textual representation of this time zone.
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def to_s
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"(GMT#{formatted_offset}) #{name}"
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end
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@@zones = nil
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class << self
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# Create a new TimeZone instance with the given name and offset.
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def create(name, offset)
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zone = allocate
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zone.send :initialize, name, offset
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zone
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end
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# Return a TimeZone instance with the given name, or +nil+ if no
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# such TimeZone instance exists. (This exists to support the use of
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# this class with the #composed_of macro.)
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def new(name)
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self[name]
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end
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# Return an array of all TimeZone objects. There are multiple TimeZone
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# objects per time zone, in many cases, to make it easier for users to
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# find their own time zone.
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def all
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unless @@zones
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@@zones = []
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[[-43_200, "International Date Line West" ],
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[-39_600, "Midway Island", "Samoa" ],
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[-36_000, "Hawaii" ],
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[-32_400, "Alaska" ],
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[-28_800, "Pacific Time (US & Canada)", "Tijuana" ],
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[-25_200, "Mountain Time (US & Canada)", "Chihuahua", "La Paz",
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"Mazatlan", "Arizona" ],
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[-21_600, "Central Time (US & Canada)", "Saskatchewan", "Guadalajara",
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"Mexico City", "Monterrey", "Central America" ],
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[-18_000, "Eastern Time (US & Canada)", "Indiana (East)", "Bogota",
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"Lima", "Quito" ],
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[-14_400, "Atlantic Time (Canada)", "Caracas", "La Paz", "Santiago" ],
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[-12_600, "Newfoundland" ],
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[-10_800, "Brasilia", "Buenos Aires", "Georgetown", "Greenland" ],
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[ -7_200, "Mid-Atlantic" ],
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[ -3_600, "Azores", "Cape Verde Is." ],
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[ 0, "Dublin", "Edinburgh", "Lisbon", "London", "Casablanca",
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"Monrovia" ],
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[ 3_600, "Belgrade", "Bratislava", "Budapest", "Ljubljana", "Prague",
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"Sarajevo", "Skopje", "Warsaw", "Zagreb", "Brussels",
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"Copenhagen", "Madrid", "Paris", "Amsterdam", "Berlin",
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"Bern", "Rome", "Stockholm", "Vienna",
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"West Central Africa" ],
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[ 7_200, "Bucharest", "Cairo", "Helsinki", "Kyev", "Riga", "Sofia",
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"Tallinn", "Vilnius", "Athens", "Istanbul", "Minsk",
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"Jerusalem", "Harare", "Pretoria" ],
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[ 10_800, "Moscow", "St. Petersburg", "Volgograd", "Kuwait", "Riyadh",
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"Nairobi", "Baghdad" ],
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[ 12_600, "Tehran" ],
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[ 14_400, "Abu Dhabi", "Muscat", "Baku", "Tbilisi", "Yerevan" ],
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[ 16_200, "Kabul" ],
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[ 18_000, "Ekaterinburg", "Islamabad", "Karachi", "Tashkent" ],
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[ 19_800, "Chennai", "Kolkata", "Mumbai", "New Delhi" ],
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[ 20_700, "Kathmandu" ],
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[ 21_600, "Astana", "Dhaka", "Sri Jayawardenepura", "Almaty",
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"Novosibirsk" ],
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[ 23_400, "Rangoon" ],
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[ 25_200, "Bangkok", "Hanoi", "Jakarta", "Krasnoyarsk" ],
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[ 28_800, "Beijing", "Chongqing", "Hong Kong", "Urumqi",
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"Kuala Lumpur", "Singapore", "Taipei", "Perth", "Irkutsk",
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"Ulaan Bataar" ],
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[ 32_400, "Seoul", "Osaka", "Sapporo", "Tokyo", "Yakutsk" ],
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[ 34_200, "Darwin", "Adelaide" ],
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[ 36_000, "Canberra", "Melbourne", "Sydney", "Brisbane", "Hobart",
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"Vladivostok", "Guam", "Port Moresby" ],
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[ 39_600, "Magadan", "Solomon Is.", "New Caledonia" ],
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[ 43_200, "Fiji", "Kamchatka", "Marshall Is.", "Auckland",
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"Wellington" ],
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[ 46_800, "Nuku'alofa" ]].
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each do |offset, *places|
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places.each { |place| @@zones << create(place, offset).freeze }
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end
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@@zones.sort!
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end
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@@zones
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end
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# Locate a specific time zone object. If the argument is a string, it
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# is interpreted to mean the name of the timezone to locate. If it is a
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# numeric value it is either the hour offset, or the second offset, of the
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# timezone to find. (The first one with that offset will be returned.)
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# Returns +nil+ if no such time zone is known to the system.
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def [](arg)
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case arg
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when String
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all.find { |z| z.name == arg }
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when Numeric
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arg *= 3600 if arg.abs <= 13
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all.find { |z| z.utc_offset == arg.to_i }
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else
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raise ArgumentError, "invalid argument to TimeZone[]: #{arg.inspect}"
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end
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end
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# A regular expression that matches the names of all time zones in
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# the USA.
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US_ZONES = /US|Arizona|Indiana|Hawaii|Alaska/ unless defined?(US_ZONES)
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# A convenience method for returning a collection of TimeZone objects
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# for time zones in the USA.
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def us_zones
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all.find_all { |z| z.name =~ US_ZONES }
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end
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end
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end
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