TLV

Provides functions to decode, encode and work with ASN.1 BER-TLV structures. It supports tags encoded on multiple bytes, length encoded on multiple bytes, indefinite length and both primitive and constructed TLVs.

Installation

Add tlv to your list of dependencies in mix.exs:

def deps do
  [{:tlv, "~> 0.0.1"}]
end

Examples

Decoding TLVs

# Primitive TLV + data after its end
iex> TLV.decode(<<0x80, 0x02, 0xCA, 0xFE, 0xAA, 0xBB>>)
{%TLV{indefinite_length: false, tag: 0x80, value: <<0xCA, 0xFE>>}, <<0xAA, 0xBB>>}

# Constructed TLV
iex> TLV.decode(<<0xE0, 0x03, 0x80, 0x01, 0xAA>>)
  {%TLV{indefinite_length: false, tag: 0xE0, value:
    [%TLV{indefinite_length: false, tag: 0x80, value: <<0xAA>>}]
  }, ""}

# Malformed TLV
iex> TLV.decode(<<0x80, 0x02, 0x00>>)
:no_tlv

Encoding TLVs

# Primitive TLV
iex> TLV.encode(%TLV{tag: 0x80, value: <<0xAA, 0xBB>>})
<<0x80, 0x02, 0xAA, 0xBB>>

# Constructed TLV
iex> TLV.encode(%TLV{tag: 0xE0, value: [%TLV{tag: 0x80, value: <<0xAA>>}]})
<<0xE0, 0x03, 0x80, 0x01, 0xAA>>