defmodule ABI.TypeEncoder do
@moduledoc """
`ABI.TypeEncoder` is responsible for encoding types to the format
expected by Solidity. We generally take a function selector and an
array of data and encode that array according to the specification.
"""
alias ABI.FunctionSelector
@doc """
Encodes the given data based on the function selector.
"""
def encode(data, selector_or_types, data_type \\ :input)
def encode(data, %FunctionSelector{function: nil, types: types}, :input) do
do_encode(data, types)
end
def encode(data, %FunctionSelector{types: types} = function_selector, :input) do
encode_method_id(function_selector) <> do_encode(data, types)
end
def encode(data, %FunctionSelector{returns: types}, :output) do
do_encode(data, types)
end
def encode(data, types, _) when is_list(types) do
do_encode(data, types)
end
def encode_raw(data, types) when is_list(types) do
do_encode(data, types)
end
defp do_encode(params, types, static_acc \\ [], dynamic_acc \\ [])
defp do_encode([], [], reversed_static_acc, reversed_dynamic_acc) do
static_acc = Enum.reverse(reversed_static_acc)
dynamic_acc = Enum.reverse(reversed_dynamic_acc)
static_part_size =
Enum.reduce(static_acc, 0, fn value, acc ->
case value do
{:dynamic, _} -> acc + 32
_ -> acc + byte_size(value)
end
end)
dynamic_indexes =
static_acc
|> Enum.with_index()
|> Enum.filter(fn {value, _index} ->
case value do
{:dynamic, _} -> true
_ -> false
end
end)
|> Enum.map(fn {{:dynamic, byte_size}, index} -> {index, byte_size} end)
{complete_static_part, _} =
Enum.reduce(dynamic_indexes, {static_acc, static_part_size}, fn {index, byte_size},
{acc, size_acc} ->
new_static_acc = List.replace_at(acc, index, encode_uint(size_acc, 256))
new_prefix_size = byte_size + size_acc
{new_static_acc, new_prefix_size}
end)
(complete_static_part ++ dynamic_acc)
|> Enum.reduce(<<>>, fn part, acc ->
acc <> part
end)
end
defp do_encode(
[current_parameter | remaining_parameters],
[current_type | remaining_types],
static_acc,
dynamic_acc
) do
{new_static_acc, new_dynamic_acc} =
do_encode_type(current_type, current_parameter, static_acc, dynamic_acc)
do_encode(remaining_parameters, remaining_types, new_static_acc, new_dynamic_acc)
end
defp do_encode_type(:bool, parameter, static_part, dynamic_part) do
value =
case parameter do
true -> encode_uint(1, 8)
false -> encode_uint(0, 8)
_ -> raise "Invalid data for bool: #{inspect(parameter)}"
end
{[value | static_part], dynamic_part}
end
defp do_encode_type({:uint, size}, parameter, static_part, dynamic_part) do
value = encode_uint(parameter, size)
{[value | static_part], dynamic_part}
end
defp do_encode_type({:int, size}, parameter, static_part, dynamic_part) do
value = encode_int(parameter, size)
{[value | static_part], dynamic_part}
end
defp do_encode_type(:string, parameter, static_part, dynamic_part) do
do_encode_type(:bytes, parameter, static_part, dynamic_part)
end
defp do_encode_type(:bytes, parameter, static_part, dynamic_part) do
binary_param = maybe_encode_unsigned(parameter)
value = encode_uint(byte_size(binary_param), 256) <> encode_bytes(binary_param)
dynamic_part_byte_size = byte_size(value)
{[{:dynamic, dynamic_part_byte_size} | static_part], [value | dynamic_part]}
end
defp do_encode_type({:bytes, size}, parameter, static_part, dynamic_part)
when is_binary(parameter) and byte_size(parameter) <= size do
value = encode_bytes(parameter)
{[value | static_part], dynamic_part}
end
defp do_encode_type({:bytes, size}, data, _, _) when is_binary(data) do
raise "size mismatch for bytes#{size}: #{inspect(data)}"
end
defp do_encode_type({:bytes, size}, data, static_part, dynamic_part) when is_integer(data) do
binary_param = maybe_encode_unsigned(data)
do_encode_type({:bytes, size}, binary_param, static_part, dynamic_part)
end
defp do_encode_type({:bytes, size}, data, _, _) do
raise "wrong datatype for bytes#{size}: #{inspect(data)}"
end
defp do_encode_type({:array, type}, data, static_acc, dynamic_acc) do
param_count = Enum.count(data)
encoded_size = encode_uint(param_count, 256)
types = List.duplicate(type, param_count)
result = do_encode(data, types)
dynamic_acc_with_size = [encoded_size | dynamic_acc]
# number of elements count + data size
data_bytes_size = byte_size(result) + 32
{[{:dynamic, data_bytes_size} | static_acc], [result | dynamic_acc_with_size]}
end
defp do_encode_type({:array, type, size}, data, static_acc, dynamic_acc) do
types = List.duplicate(type, size)
result = do_encode(data, types)
if FunctionSelector.is_dynamic?(type) do
data_bytes_size = byte_size(result)
{[{:dynamic, data_bytes_size} | static_acc], [result | dynamic_acc]}
else
{[result | static_acc], dynamic_acc}
end
end
defp do_encode_type(:address, data, static_acc, dynamic_acc) do
do_encode_type({:uint, 160}, data, static_acc, dynamic_acc)
end
defp do_encode_type(type = {:tuple, types}, tuple_parameters, static_acc, dynamic_acc)
when is_tuple(tuple_parameters) do
list_parameters = Tuple.to_list(tuple_parameters)
result = do_encode(list_parameters, types)
if FunctionSelector.is_dynamic?(type) do
data_bytes_size = byte_size(result)
{[{:dynamic, data_bytes_size} | static_acc], [result | dynamic_acc]}
else
{[result | static_acc], dynamic_acc}
end
end
defp encode_bytes(bytes) do
pad(bytes, byte_size(bytes), :right)
end
@spec encode_method_id(%FunctionSelector{}) :: binary()
defp encode_method_id(%FunctionSelector{function: nil}), do: ""
defp encode_method_id(function_selector) do
# Encode selector e.g. "baz(uint32,bool)" and take keccak
kec =
function_selector
|> FunctionSelector.encode()
|> ExKeccak.hash_256()
# Take first four bytes
<<init::binary-size(4), _rest::binary>> = kec
# That's our method id
init
end
# Note, we'll accept a binary or an integer here, so long as the
# binary is not longer than our allowed data size
defp encode_uint(data, size_in_bits) when rem(size_in_bits, 8) == 0 do
size_in_bytes = (size_in_bits / 8) |> round
bin = maybe_encode_unsigned(data)
if byte_size(bin) > size_in_bytes,
do:
raise(
"Data overflow encoding uint, data `#{data}` cannot fit in #{size_in_bytes * 8} bits"
)
bin |> pad(size_in_bytes, :left)
end
defp encode_int(data, size_in_bits) when rem(size_in_bits, 8) == 0 do
if signed_overflow?(data, size_in_bits) do
raise("Data overflow encoding int, data `#{data}` cannot fit in #{size_in_bits} bits")
end
encode_int(data)
end
# encoding with integer-signed-256 we already get the right padding
defp encode_int(data), do: <<data::signed-256>>
defp signed_overflow?(n, max_bits) do
n < :math.pow(2, max_bits - 1) * -1 + 1 || n > :math.pow(2, max_bits - 1) - 1
end
# TODO change to ExthCrypto.Math.mod when it's fixed ( mod(-75,32) == 21 )
def mod(x, n) do
remainder = rem(x, n)
if (remainder < 0 and n > 0) or (remainder > 0 and n < 0),
do: n + remainder,
else: remainder
end
defp pad(bin, size_in_bytes, direction) do
# TODO: Create `left_pad` repo, err, add to `ExthCrypto.Math`
total_size = size_in_bytes + mod(32 - size_in_bytes, 32)
padding_size_bits = (total_size - byte_size(bin)) * 8
padding = <<0::size(padding_size_bits)>>
case direction do
:left -> padding <> bin
:right -> bin <> padding
end
end
@spec maybe_encode_unsigned(binary() | non_neg_integer()) :: binary()
defp maybe_encode_unsigned(bin) when is_binary(bin), do: bin
defp maybe_encode_unsigned(int) when is_integer(int), do: :binary.encode_unsigned(int)
end
