# ExRLP [](https://circleci.com/gh/mana-ethereum/ex_rlp)
Elixir implementation of Ethereum's RLP (Recursive Length Prefix) encoding
The encoding's specification can be found in [the yellow paper](http://yellowpaper.io/) or in the [ethereum wiki](https://github.com/ethereum/wiki/wiki/RLP)
## Installation
The easiest way to add ExRLP to your project is by [using Mix](http://elixir-lang.org/getting-started/mix-otp/introduction-to-mix.html).
Add `:ex_rlp` as a dependency to your project's `mix.exs`:
```elixir
defp deps do
[
{:ex_rlp, "~> 0.5.3"}
]
end
```
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.
```elixir
## Examples
iex(1)> "dog" |> ExRLP.encode(encoding: :hex)
"83646f67"
iex(2)> "dog" |> ExRLP.encode(encoding: :binary)
<<0x83, 0x64, 0x6f, 0x67>>
iex(3)> 1000 |> ExRLP.encode(encoding: :hex)
"8203e8"
# Default encoding is binary
iex(3)> 1000 |> ExRLP.encode
<<0x82, 0x03, 0xe8>>
iex(4)> [ [ [], [] ], [] ] |> 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.
```elixir
## Examples
iex(1)> "83646f67" |> ExRLP.decode(encoding: :hex)
"dog"
iex(2)> "8203e8" |> ExRLP.decode(encoding: :hex) |> :binary.decode_unsigned
1000
iex(3)> "c4c2c0c0c0" |> ExRLP.decode(encoding: :hex)
[[[], []], []]
```
More examples can be found in test files.
## Protocols
You can define protocols for encoding/decoding custom data types.
```elixir
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!](https://github.com/exthereum/ex_rlp/fork)
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)
## License
ExRLP is released under the MIT License. See the LICENSE file for further details.
