Class: Codec::Tlv

Inherits:
Prefixedlength show all
Defined in:
lib/codec/tlv.rb

Instance Method Summary collapse

Methods inherited from Prefixedlength

#get_length

Methods inherited from Base

#add_sub_codec, #get_sub_codecs

Constructor Details

#initialize(length, header, content) ⇒ Tlv

Returns a new instance of Tlv.



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# File 'lib/codec/tlv.rb', line 3

def initialize(length,header,content)
  super(length,content)
  @tag_codec = header
  @subCodecs = {}
end

Instance Method Details

#check_length(buf, length) ⇒ Object 



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# File 'lib/codec/tlv.rb', line 9

def check_length(buf,length)
 raise "Length is nil" if length.nil?
  if(length != 0)
   if buf.length < length
     raise BufferUnderflow, "Not enough data for decoding (#{length}/#{buf.length})"
   end
    return length
  else
    return buf.length
  end    
end

#decode(buffer, msg, length = nil) ⇒ Object 



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# File 'lib/codec/tlv.rb', line 39

def decode(buffer, msg, length = nil)
  unless length.nil?
    l = check_length(buffer,length)
    buffer = buffer.slice!(0...l)
  end
  
  tag = Field.new
  begin
    until buffer.empty?
      begin
        @tag_codec.decode(buffer,tag)
      rescue
        raise ParsingException, "Tlv Codec still remaining data but failed to decode tag when decoding field #{msg.get_id}"
      end
      Logger.debug { "Decoding tag #{tag.get_value.to_s}"}
      sf = Field.new(tag.get_value.to_s)
      subcodec = @subCodecs[tag.get_value.to_s]
      if subcodec.nil?
        Logger.debug { "using default codec for tag #{tag.get_value.to_s}"}
        super(buffer,sf)
      else
        Logger.debug { "using predefined codec for tag #{tag.get_value.to_s}"}
        len_field = Field.new("len")
        @length_codec.decode(buffer,len_field)
        subcodec.decode(buffer,sf,len_field.get_value.to_i)
      end
      Logger.debug { "Add field #{sf} to tlv"}
      msg.add_sub_field(sf)
    end
  rescue BufferUnderflow => e
    raise ParsingException, "Tlv Codec failed to decode field #{msg.get_id}"
    val = Field.new
    val.set_value("Buffer underflow when parsing tlv #{msg.get_id} [#{buffer.unpack("H*").first}]")
    buffer.clear
  end
  unless buffer.empty? || length.nil?
    Logger.warn("Remain data in a tlv buffer :[#{buffer.unpack("H*").first}]") 
  end
end

#encode(buf, field) ⇒ Object 



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# File 'lib/codec/tlv.rb', line 21

def encode(buf, field)
  out = ""
  fields = field.get_value
  fields.each do |sf|
    @tag_codec.encode(out, Field.new('*',sf.get_id))
    if @subCodecs[sf.get_id]
      content = ""
      len = @subCodecs[sf.get_id].encode(content, sf)
      @length_codec.encode(out, Field.new('*',len))
      out << content
    else
      super(out, sf)
    end
  end
  buf << out
  return out.length
end