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The core package for the Elixium blockchain, containing all the modules needed to run the chain
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lib/encoding/block_encoder.ex
defmodule Elixium.BlockEncoder do
alias Elixium.Block
@moduledoc """
Provides functionality for encoding and decoding blocks
"""
@encoding_order [
:index, :hash, :previous_hash,
:merkle_root, :timestamp, :nonce,
:difficulty, :version, :transactions
]
@doc """
Encode a block to a binary representation based on the encoding order:
@encoding_order
"""
@spec encode(Block) :: binary
def encode(block) do
block = Map.delete(block, :__struct__)
Enum.reduce(@encoding_order, <<>>, fn attr, bin -> encode(attr, bin, block[attr]) end)
end
defp encode(:difficulty, bin, value) do
# Convert to binary and strip out ETF bytes (we dont need them for storage,
# we can add them back in when we need to read)
<<131, 70, difficulty::binary>> = :erlang.term_to_binary(value)
bin <> difficulty
end
defp encode(:transactions, bin, value) do
# Add transactions in as raw ETF encoding for easy decoding later
bin <> :erlang.term_to_binary(value)
end
defp encode(:hash, bin, value), do: b16encode(bin, value)
defp encode(:previous_hash, bin, value), do: b16encode(bin, value)
defp encode(:merkle_root, bin, value), do: b16encode(bin, value)
defp encode(_attr, bin, value) when is_binary(value) do
bin <> value
end
defp encode(_attr, bin, value) when is_number(value) do
bin <> :binary.encode_unsigned(value)
end
defp b16encode(bin, value), do: bin <> Base.decode16!(value)
@doc """
Decode a block from binary that was previously encoded by encode/1
"""
@spec decode(binary) :: Block
def decode(block_binary) do
<<index::bytes-size(4),
hash::bytes-size(32),
previous_hash::bytes-size(32),
merkle_root::bytes-size(32),
timestamp::bytes-size(4),
nonce::bytes-size(8),
difficulty::bytes-size(8),
version::bytes-size(2),
transactions::binary
>> = block_binary
%Block{
index: index,
hash: Base.encode16(hash),
previous_hash: Base.encode16(previous_hash),
merkle_root: Base.encode16(merkle_root),
timestamp: :binary.decode_unsigned(timestamp),
nonce: nonce,
difficulty: :erlang.binary_to_term(<<131, 70>> <> difficulty),
version: version,
transactions: :erlang.binary_to_term(transactions)
}
end
end