ExRLP

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.

Installation

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, "~> 0.6.0"}
  ]
end

And run:

$ mix deps.get

Basic Usage

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

iex> "dog" |> ExRLP.encode(encoding: :hex)
"83646f67"

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

iex> 1000 |> ExRLP.encode(encoding: :hex)
"8203e8"

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

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

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.

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

iex> "8203e8" |> ExRLP.decode(encoding: :hex) |> :binary.decode_unsigned
1000

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

More examples can be found in test files.

Protocols

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
    %__MODULE__{
      address: address,
      topics: topics,
      data: data
    }
  end

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

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

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

Contributing

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

Author

Ayrat Badykov (@ayrat555)

Copyright and License

Copyright (c) 2017 Geoffrey Hayes, Ayrat Badykov, Mason Forest

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