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# -*- coding: binary -*-
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#---
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# $Id: Question.rb,v 1.8 2006/07/28 19:00:03 bluemonk Exp $     
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#+++
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require 'net/dns/dns'
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require 'net/dns/names/names'
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require 'net/dns/rr/types'
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require 'net/dns/rr/classes'
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module Net # :nodoc:
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  module DNS 
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    #
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    # =Name
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    #
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    # Net::DNS::Question - DNS packet question class
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    #
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    # =Synopsis
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    # 
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    #   require 'net/dns/question'
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    #
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    # =Description
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    #
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    # This class represent the Question portion of a DNS packet. The number
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    # of question entries is stored in the +qdCount+ variable of an Header
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    # object. 
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    #
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    # A new object can be created passing the name of the query and the type
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    # of answer desired, plus an optional argument containing the class:
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    #
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    #   question = Net::DNS::Question.new("google.com.", Net::DNS::A)
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    #      #=> "google.com.                   A       IN"
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    #
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    # Alternatevly, a new object is created when processing a binary
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    # packet, as when an answer is received.
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    # To obtain the binary data from a question object you can use
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    # the method Question#data:
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    # 
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    #   question.data
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    #      #=> "\006google\003com\000\000\001\000\001"
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    #
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    # A lot of methods were written to keep a compatibility layer with
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    # the Perl version of the library, as long as methods name which are
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    # more or less the same. 
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    #
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    # =Error classes
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    #
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    # Some error classes has been defined for the Net::DNS::Header class,
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    # which are listed here to keep a light and browsable main documentation.
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    # We have:
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    #
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    # * QuestionArgumentError: generic argument error
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    # * QuestionNameError:     an error in the +name+ part of a Question entry
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    #
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    # =Copyright
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    # 
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    # Copyright (c) 2006 Marco Ceresa
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    #
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    # All rights reserved. This program is free software; you may redistribute 
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    # it and/or modify it under the same terms as Ruby itself.
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    #
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    class Question
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      include Net::DNS::Names
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      # +name+ part of a Question entry
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      attr_reader :qName 
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      # +type+ part of a Question entry
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      attr_reader :qType 
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      # +class+ part of a Question entry
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      attr_reader :qClass 
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      # Creates a new Net::DNS::Question object:
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      #
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      #   question = Net::DNS::Question.new("example.com")
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      #      #=> "example.com                   A       IN"
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      #   question = Net::DNS::Question.new("example.com", Net::DNS::MX)
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      #      #=> "example.com                   MX      IN"
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      #   question = Net::DNS::Question.new("example.com", Net::DNS::TXT, Net::DNS::HS)
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      #      #=> "example.com                   TXT     HS"
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      # If not specified, +type+ and +cls+ arguments defaults 
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      # to Net::DNS::A and Net::DNS::IN respectively.
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      #
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      def initialize(name,type=Net::DNS::A,cls=Net::DNS::IN)
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        @qName = check_name name
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        @qType = Net::DNS::RR::Types.new type
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        @qClass = Net::DNS::RR::Classes.new cls
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      end
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      # Return a new Net::DNS::Question object created by
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      # parsing binary data, such as an answer from the
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      # nameserver.
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      #
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      #   question = Net::DNS::Question.parse(data)
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      #   puts "Queried for #{question.qName} type #{question.qType.to_s}"
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      #     #=> Queried for example.com type A
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      #
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      def self.parse(arg)
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        if arg.kind_of? String
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          o = allocate
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          o.send(:new_from_binary,arg)
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          o
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        else
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          raise QuestionArgumentError, "Wrong argument format, must be a String"
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        end
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      end
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      # Known inspect method with nice formatting
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      def inspect
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        if @qName.size > 29 then 
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          len = @qName.size + 1 
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        else
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          len = 29
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        end
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        [@qName,@qClass.to_s,@qType.to_s].pack("A#{len} A8 A8")
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      end
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      # Outputs binary data from a Question object
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      #
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      #   question.data
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      #      #=> "\006google\003com\000\000\001\000\001"
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      #
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      def data
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        [pack_name(@qName),@qType.to_i,@qClass.to_i].pack("a*nn")
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      end
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      # Return the binary data of the objects, plus an offset
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      # and an Hash with references to compressed names. For use in 
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      # Net::DNS::Packet compressed packet creation.
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      #
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      def comp_data
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        arr = @qName.split(".")
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        str = pack_name(@qName)
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        string = ""
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        names = {}
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        offset = Net::DNS::HFIXEDSZ
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        arr.size.times do |i|
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          x = i+1
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          elem = arr[-x]
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          len = elem.size
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          string = ((string.reverse)+([len,elem].pack("Ca*")).reverse).reverse
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          names[string] = offset
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          offset += len
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        end
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        offset += 2 * Net::DNS::INT16SZ
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        str += "\000"
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        [[str,@qType.to_i,@qClass.to_i].pack("a*nn"),offset,names]
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      end
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      private
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      def build_qName(str)
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        result = ""
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        offset = 0
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        loop do
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          len = str.unpack("@#{offset} C")[0]
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          break if len == 0
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          offset += 1
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          result += str[offset..offset+len-1]
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          result += "."
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          offset += len
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        end
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        result
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      end
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      def check_name(name)
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        name.strip!
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        if name =~ /[^\w\.\-_]/
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          raise QuestionNameError, "Question name #{name.inspect} not valid"          
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        else
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          name
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        end
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      rescue
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        raise QuestionNameError, "Question name #{name.inspect} not valid"                  
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      end
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      def new_from_binary(data)
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        str,type,cls = data.unpack("a#{data.size-4}nn")
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        @qName = build_qName(str)
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        @qType = Net::DNS::RR::Types.new type
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        @qClass = Net::DNS::RR::Classes.new cls
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      rescue StandardError => e
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        raise QuestionArgumentError, "Invalid data: #{data.inspect}\n{e.backtrace}"
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      end
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    end # class Question
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  end # class DNS
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end # module Net
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class QuestionArgumentError < ArgumentError # :nodoc:
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end
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class QuestionNameError < StandardError # :nodoc:
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end
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