Elixir implementation of Ethereum's RLP (Recursive Length Prefix) encoding
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ExRLP CircleCI

Elixir implementation of Ethereum's RLP (Recursive Length Prefix) encoding

The encoding's specification can be found in the yellow paper or in the ethereum wiki


The easiest way to add ExRLP to your project is by using Mix.

Add :ex_rlp as a dependency to your project's mix.exs:

defp deps do
    {:ex_rlp, "~> 0.5.1"}

And run:

$ mix deps.get

Basic Usage

Use ExRLP.encode/1 method to encode an item to RLP representation. An item can be nonnegative integer, binary or list. List can contain integers, binaries or lists.

  ## Examples

      iex(1)> "dog" |> ExRLP.encode(encoding: :hex)

      iex(2)> "dog" |> ExRLP.encode(encoding: :binary)
      <<0x83, 0x64, 0x6f, 0x67>>

      iex(3)> 1000 |> ExRLP.encode(encoding: :hex)

      # Default encoding is binary
      iex(3)> 1000 |> ExRLP.encode
      <<0x82, 0x03, 0xe8>>

      iex(4)> [ [ [], [] ], [] ] |> ExRLP.encode(encoding: :hex)

Use ExRLP.decode/1 method to decode a rlp encoded data. All items except lists are decoded as binaries so additional deserialization is needed if initially an item of another type was encoded.

  ## Examples

      iex(1)> "83646f67" |> ExRLP.decode(encoding: :hex)

      iex(2)> "8203e8" |> ExRLP.decode(encoding: :hex) |> :binary.decode_unsigned

      iex(3)> "c4c2c0c0c0" |> ExRLP.decode(encoding: :hex)
      [[[], []], []]

More examples can be found in test files.


You can define protocols for encoding/decoding custom data types.

defmodule ExRLP.LogEntry do
  defstruct address: nil, topics: [], data: nil

  @type t :: %__MODULE__{
          address: EVM.address(),
          topics: [integer()],
          data: binary()

  @spec new(binary, [integer()], binary()) :: t()
  def new(address, topics, data) do
      address: address,
      topics: topics,
      data: data

  def to_list(log) do
    [log.address, log.topics, log.data]

defimpl ExRLP.Encode, for: ExRLP.LogEntry do
  alias ExRLP.{Encode, LogEntry}

  @spec encode(LogEntry.t(), keyword()) :: binary()
  def encode(log, options \\ []) do
    |> LogEntry.to_list()
    |> Encode.encode(options)


  1. Fork it!
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request


Ayrat Badykov (@ayrat555)


ExRLP is released under the MIT License. See the LICENSE file for further details.