Class: Dnsruby::MessageDecoder

Inherits:
Object
  • Object
show all
Defined in:
lib/Dnsruby/message.rb

Overview

:nodoc: all

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(data) {|_self| ... } ⇒ MessageDecoder

Returns a new instance of MessageDecoder.

Yields:

  • (_self)

Yield Parameters:



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# File 'lib/Dnsruby/message.rb', line 875

def initialize(data)
  @data = data
  @index = 0
  @limit = data.length
  yield self
end

Instance Attribute Details

#index ⇒ Object (readonly)

Returns the value of attribute index.



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# File 'lib/Dnsruby/message.rb', line 874

def index
  @index
end

Instance Method Details

#get_bytes(len = @limit - @index) ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 900

def get_bytes(len = @limit - @index)
  d = @data[@index, len]
  @index += len
  return d
end

#get_label ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 999

def get_label
  begin
    #        label = Name::Label.new(Name::decode(self.get_string))
    label = Name::Label.new(self.get_string)
    return label
    #         return Name::Label::Str.new(self.get_string)
  rescue ResolvError => e
    raise DecodeError.new(e) # Turn it into something more suitable
  end
end

#get_labels(limit = nil) ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 970

def get_labels(limit=nil)
  limit = @index if !limit || @index < limit
  d = []
  while true
    temp = @data[@index]
    if (temp.class == String)
      temp = (temp.getbyte(0))
    end
    case temp # @data[@index]
    when 0
      @index += 1
      return d
    when 192..255
      idx = self.get_unpack('n')[0] & 0x3fff
      if limit <= idx
        raise DecodeError.new("non-backward name pointer")
      end
      save_index = @index
      @index = idx
      d += self.get_labels(limit)
      @index = save_index
      return d
    else
      d << self.get_label
    end
  end
  return d
end

#get_length16 ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 886

def get_length16
  len, = self.get_unpack('n')
  save_limit = @limit
  @limit = @index + len
  d = yield(len)
  if @index < @limit
    raise DecodeError.new("junk exists")
  elsif @limit < @index
    raise DecodeError.new("limit exceeded")
  end
  @limit = save_limit
  return d
end

#get_name ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 966

def get_name
  return Name.new(self.get_labels)
end

#get_question ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 1010

def get_question
  name = self.get_name
  type, klass = self.get_unpack("nn")
  q = Question.new(name, type, klass)
  return q
end

#get_rr ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 1017

def get_rr
  name = self.get_name
  type, klass, ttl = self.get_unpack('nnN')
  klass = Classes.new(klass)
  typeclass = RR.get_class(type, klass)
  # @TODO@ Trap decode errors here, and somehow mark the record as bad.
  # Need some way to represent raw data only
  rec = self.get_length16 {typeclass.decode_rdata(self)}
  rec.name=name
  rec.ttl=ttl
  rec.type = type
  rec.klass = klass
  return rec
end

#get_string ⇒ Object

Raises:



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# File 'lib/Dnsruby/message.rb', line 947

def get_string
  len = @data[@index]
  if (len.class == String)
    len = len.getbyte(0)
  end
  raise DecodeError.new("limit exceeded\nlimit = #{@limit}, index = #{@index}, len = #{len}\n") if @limit < @index + 1 + (len ? len : 0)
  d = @data[@index + 1, len]
  @index += 1 + len
  return d
end

#get_string_list ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 958

def get_string_list
  strings = []
  while @index < @limit
    strings << self.get_string
  end
  strings
end

#get_unpack(template) ⇒ Object

Raises:



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# File 'lib/Dnsruby/message.rb', line 906

def get_unpack(template)
  len = 0
  littlec = ?c
  bigc = ?C
  littleh = ?h
  bigh = ?H
  littlen = ?n
  bign = ?N
  star = ?*
  if (littlec.class != Fixnum)
    # We're using Ruby 1.9 - convert the codes
    littlec = littlec.getbyte(0)
    bigc = bigc.getbyte(0)
    littleh = littleh.getbyte(0)
    bigh = bigh.getbyte(0)
    littlen = littlen.getbyte(0)
    bign = bign.getbyte(0)
    star = star.getbyte(0)
  end
  template.each_byte {|byte|
    case byte
    when littlec, bigc
      len += 1
    when littleh, bigh
      len += 1
    when littlen
      len += 2
    when bign
      len += 4
    when star
      len = @limit-@index
    else
      raise StandardError.new("unsupported template: '#{byte.chr}' in '#{template}'")
    end
  }
  raise DecodeError.new("limit exceeded") if @limit < @index + len
  arr = @data.unpack("@#{@index}#{template}")
  @index += len
  return arr
end

#has_remaining ⇒ Object 



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# File 'lib/Dnsruby/message.rb', line 882

def has_remaining
  return @limit-@index > 0
end