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# -*- coding: binary -*-
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module Net # :nodoc:
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  module DNS
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    class RR
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      #
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      # This is an auxiliary class to hadle RR class field in a DNS packet.
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      #
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      class Classes
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        # An hash with the values of each RR class stored with the
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        # respective id number
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        Classes = {
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          'IN'        => 1,       # RFC 1035
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          'CH'        => 3,       # RFC 1035
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          'HS'        => 4,       # RFC 1035
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          'NONE'      => 254,     # RFC 2136
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          'ANY'       => 255,     # RFC 1035
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        }
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        # The default value when class is nil in Resource Records
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        @@default = Classes["IN"]
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        # Be able to control the default class to assign when
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        # cls argument is +nil+. Default to +IN+
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        def self.default=(str)
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          if Classes.has_key? str
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            @@default = Classes[str]
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          else
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            raise ClassArgumentError, "Unknown class #{str}"
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          end
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        end
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        # Checks whether +cls+ is a valid RR class.
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        def self.valid?(cls)
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          case cls
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          when String
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            return Classes.has_key?(cls)
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          when Integer
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            return Classes.invert.has_key?(cls)
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          else
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            raise ClassArgumentError, "Wrong class: #{cls.class}"
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          end
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        end
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        # Returns the class in string format, as "IN" or "CH",
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        # given the numeric value
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        def self.to_str(cls)
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          case cls
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          when Integer
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            if Classes.invert.has_key? cls
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              return Classes.invert[cls]
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            else
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              raise ClassArgumentError, "Unknown class number #{cls}"
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            end
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          else
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            raise ClassArgumentError, "Wrong class: #{cls.class}"
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          end
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        end
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        # Gives in output the keys from the +Classes+ hash
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        # in a format suited for regexps
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        def self.regexp
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          Classes.keys.join("|")
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        end
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        # Creates a new object representing an RR class. Performs some
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        # checks on the argument validity too. Il +cls+ is +nil+, the
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        # default value is +ANY+ or the one set with Classes.default=
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        def initialize(cls)
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          case cls
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          when String
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            # type in the form "A" or "NS"
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            new_from_string(cls.upcase)
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          when Integer
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            # type in numeric form
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            new_from_num(cls)
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          when nil
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            # default type, control with Classes.default=
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            @str = Classes.invert[@@default]
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            @num = @@default
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          else
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            raise ClassArgumentError, "Wrong class: #{cls.class}"
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          end
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        end
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        # Constructor for string data class,
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        # *PRIVATE* method
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        def new_from_string(cls)
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          case cls
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          when /^CLASS(\d+)$/
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            new_from_num(Regexp.last_match(1).to_i)
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          else
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            # String with name of class
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            if Classes.has_key? cls
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              @str = cls
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              @num = Classes[cls]
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            else
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              raise ClassArgumentError, "Unknown class #{cls}"
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            end
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          end
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        end
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        # Constructor for numeric data class
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        # *PRIVATE* method
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        def new_from_num(cls)
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          raise ClassArgumentError, "Invalid class #{cls}" if cls < 0 || cls > 0xFFFF
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          if Classes.invert.has_key? cls
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            @num = cls
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            @str = Classes.invert[cls]
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          else
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            @num = cls
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            @str = "CLASS#{cls}"
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          end
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        end
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        # Returns the class in number format
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        # (default for normal use)
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        def inspect
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          @num
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        end
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        # Returns the class in string format,
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        # i.d. "IN" or "CH" or such a string.
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        def to_s
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          @str
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        end
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        # Returns the class in numeric format,
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        # usable by the pack methods for data transfers
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        def to_i
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          @num.to_i
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        end
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        # Should be used only for testing purpouses
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        def to_str
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          @num.to_s
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        end
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        private :new_from_num, :new_from_string
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      end # class Classes
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    end # class RR
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  end # module DNS
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end # module Net
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class ClassArgumentError < ArgumentError # :nodoc:
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end
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