feat: merklelization of basic types (#514)

lib/spec/runners/ssz_generic.ex

@@ -49,32 +49,46 @@ defmodule SszGenericTestRunner do
   defp handle_case("valid", schema, real_serialized, testcase) do
     case_dir = SpecTestCase.dir(testcase)
 
-    expected =
+    expected_value =
       YamlElixir.read_from_file!(case_dir <> "/value.yaml")
       |> SpecTestUtils.sanitize_yaml()
 
-    assert_ssz("valid", schema, real_serialized, expected)
+    %{root: expected_root} =
+      YamlElixir.read_from_file!(case_dir <> "/meta.yaml")
+      |> SpecTestUtils.sanitize_yaml()
+
+    assert_ssz("valid", schema, real_serialized, expected_value, expected_root)
   end
 
   defp handle_case("invalid", schema, real_serialized, _testcase) do
     assert_ssz("invalid", schema, real_serialized)
   end
 
-  defp assert_ssz("valid", {:container, module}, real_serialized, real_deserialized) do
+  defp assert_ssz(
+         "valid",
+         {:container, module},
+         real_serialized,
+         real_deserialized,
+         _hash_tree_root
+       ) do
     real_struct = struct!(module, real_deserialized)
     {:ok, deserialized} = SszEx.decode(real_serialized, module)
     assert deserialized == real_struct
     {:ok, serialized} = SszEx.encode(real_struct, module)
     assert serialized == real_serialized
   end
 
-  defp assert_ssz("valid", schema, real_serialized, real_deserialized) do
+  defp assert_ssz("valid", schema, real_serialized, real_deserialized, expected_hash_tree_root) do
     {:ok, deserialized} = SszEx.decode(real_serialized, schema)
     assert deserialized == real_deserialized
 
     {:ok, serialized} = SszEx.encode(real_deserialized, schema)
 
     assert serialized == real_serialized
+
+    actual_hash_tree_root = SszEx.hash_tree_root!(real_deserialized, schema)
+
+    assert actual_hash_tree_root == expected_hash_tree_root
   end
 
   defp assert_ssz("invalid", schema, real_serialized) do

lib/ssz.ex

@@ -1,6 +1,6 @@
 defmodule Ssz do
   @moduledoc """
-  SimpleSerialize (SSZ) serialization and deserialization.
+  SimpleSerialize (SSZ) serialization, deserialization and merkleization.
   """
   use Rustler, otp_app: :lambda_ethereum_consensus, crate: "ssz_nif"
 

lib/ssz_ex.ex

@@ -7,6 +7,8 @@ defmodule LambdaEthereumConsensus.SszEx do
   ### Public API
   #################
 
+  @bits_per_chunk 256
+
   @spec hash(iodata()) :: binary()
   def hash(data), do: :crypto.hash(:sha256, data)
 
@@ -36,6 +38,12 @@ defmodule LambdaEthereumConsensus.SszEx do
 
   def decode(binary, module) when is_atom(module), do: decode_container(binary, module)
 
+  @spec hash_tree_root!(boolean, atom) :: SszTypes.root()
+  def hash_tree_root!(value, :bool), do: pack(value)
+
+  @spec hash_tree_root!(non_neg_integer, {:int, non_neg_integer}) :: SszTypes.root()
+  def hash_tree_root!(value, {:int, size}), do: pack(value, size)
+
   #################
   ### Private functions
   #################
@@ -398,4 +406,16 @@ defmodule LambdaEthereumConsensus.SszEx do
     |> Enum.map(fn {_, schema} -> variable_size?(schema) end)
     |> Enum.any?()
   end
+
+  defp pack(value, size) when is_integer(value) and value >= 0 do
+    pad = @bits_per_chunk - size
+    <<value::size(size)-little, 0::size(pad)>>
+  end
+
+  defp pack(value) when is_boolean(value) do
+    case value do
+      true -> <<1::@bits_per_chunk-little>>
+      false -> <<0::@bits_per_chunk>>
+    end
+  end
 end