Implement Xgit.Core.ObjectId.to_binary_iodata/1. (#150)

lib/xgit/core/object_id.ex

@@ -53,6 +53,16 @@ defmodule Xgit.Core.ObjectId do
     end
   end
 
+  @doc ~S"""
+  Convert an object ID to raw binary representation.
+
+  ## Return Value
+
+  A 20-byte binary encoding the object ID.
+  """
+  @spec to_binary_iodata(id :: t) :: binary
+  def to_binary_iodata(id), do: Base.decode16!(id, case: :lower)
+
   @doc ~S"""
   Assign an object ID for a given data blob.
 

lib/xgit/repository/working_tree/write_index_file.ex

@@ -10,6 +10,7 @@ defmodule Xgit.Repository.WorkingTree.WriteIndexFile do
 
   alias Xgit.Core.DirCache
   alias Xgit.Core.DirCache.Entry, as: DirCacheEntry
+  alias Xgit.Core.ObjectId
   alias Xgit.Util.NB
   alias Xgit.Util.TrailingHashDevice
 
@@ -108,15 +109,13 @@ defmodule Xgit.Repository.WorkingTree.WriteIndexFile do
       NB.encode_uint32(uid),
       NB.encode_uint32(gid),
       NB.encode_uint32(size),
-      encode_object_id(object_id),
+      ObjectId.to_binary_iodata(object_id),
       encode_v2_flags(stage, assume_valid?, extended?, name_length),
       name,
       padding(name_length)
     ])
   end
 
-  defp encode_object_id(object_id), do: Base.decode16!(object_id, case: :lower)
-
   defp encode_v2_flags(stage, assume_valid?, extended?, name_length) do
     value =
       value_if_boolean(assume_valid?, 0x8000) +

test/xgit/core/object_id_test.exs

@@ -36,6 +36,12 @@ defmodule Xgit.Core.ObjectIdTest do
     assert ObjectId.from_hex_charlist('1234567890abXdef12341234567890abcdef1234') == false
   end
 
+  test "to_binary_iodata/1" do
+    assert ObjectId.to_binary_iodata("1234567890abcdef12341234567890abcdef1234") ==
+             <<18, 52, 86, 120, 144, 171, 205, 239, 18, 52, 18, 52, 86, 120, 144, 171, 205, 239,
+               18, 52>>
+  end
+
   describe "calculate_id/3" do
     test "happy path: SHA hash with string content" do
       assert ObjectId.calculate_id("test content\n", :blob) ==