From: Dion Mendel <dion@...>
Date: 2010-10-04T15:51:24+09:00
Subject: Re: any good tools for reading networking data with optional TLV

Ramana Gollamudi wrote:

> I tried to see if bindata works but the documentation is unclear 
> on whether it can handle multiple TLVS that may exist in different
> combination in each packet?

I am the author of BinData.  Yes BinData handles optional TLVs
(type-length-value).  You didn't specify if your TLVs are nested or
flat.  An example of flat TLVs is given below.  Nested TLVs are
slightly more complicated and require more code so I haven't provided
an example.  Contact me offlist if you need more details.

Here is an example of a data format (MyFormat) supporting multiple,
optional, unordered TLVs.

class CustomType1 < BinData::Record
  int8   :a
  int8   :b
  ...
end

...

class Tlv < BinData::Record
  endian :big
  uint8  :t
  uint32 :l
  choice :v, :selection => :chooser do
    string "unknown", :read_length => :l
    custom_type_1 "v1"
    custom_type_2 "v2"
    ...
  end

  def chooser
    if t == xx and l == yy
      "v1"
    elsif t == ww and l == zz
      ...
    else
      "unknown"
    end
  end
end

class MyFormat < BinData::Record
  ...
  array :options, :type => :tlv,
        :read_until => lambda { my_terminating_condition }
end
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