Modify the DDL.Tx API slightly to be easier to work with.

lib/wafer/dll/tx.ex

@@ -28,23 +28,23 @@ defmodule Wafer.DLL.Tx do
   @spec tx(t) :: {byte, t} | :done
   def tx(%Tx{state: :idle} = tx), do: {@byte_start, %{tx | state: :transmitting}}
 
-  def tx(%Tx{state: :transmitting, buffer: <<@byte_start::integer-size(8), _::binary>>} = rx),
-    do: {@byte_esc, %{rx | state: :escaping}}
+  def tx(%Tx{state: :transmitting, buffer: <<@byte_start, _::binary>>} = tx),
+    do: {@byte_esc, %{tx | state: :escaping}}
 
-  def tx(%Tx{state: :transmitting, buffer: <<@byte_end::integer-size(8), _::binary>>} = rx),
-    do: {@byte_esc, %{rx | state: :escaping}}
+  def tx(%Tx{state: :transmitting, buffer: <<@byte_end, _::binary>>} = tx),
+    do: {@byte_esc, %{tx | state: :escaping}}
 
-  def tx(%Tx{state: :transmitting, buffer: <<@byte_esc::integer-size(8), _::binary>>} = rx),
-    do: {@byte_esc, %{rx | state: :escaping}}
+  def tx(%Tx{state: :transmitting, buffer: <<@byte_esc, _::binary>>} = tx),
+    do: {@byte_esc, %{tx | state: :escaping}}
 
-  def tx(%Tx{state: :transmitting, buffer: <<byte::integer-size(8), buffer::binary>>} = rx),
-    do: {byte, %{rx | state: :transmitting, buffer: buffer}}
+  def tx(%Tx{state: :transmitting, buffer: <<byte, buffer::binary>>} = tx),
+    do: {byte, %{tx | state: :transmitting, buffer: buffer}}
 
-  def tx(%Tx{state: :escaping, buffer: <<byte::integer-size(8), buffer::binary>>} = rx),
-    do: {byte, %{rx | state: :escaping, buffer: buffer}}
+  def tx(%Tx{state: :escaping, buffer: <<byte, buffer::binary>>} = tx),
+    do: {byte, %{tx | state: :escaping, buffer: buffer}}
 
-  def tx(%Tx{buffer: <<>>, state: :transmitting} = rx), do: {@byte_end, %{rx | state: :complete}}
-  def tx(%Tx{state: :complete}), do: :done
+  def tx(%Tx{buffer: <<>>, state: :transmitting} = tx), do: {@byte_end, %{tx | state: :complete}}
+  def tx(%Tx{state: :complete} = tx), do: {:done, tx}
 
   def complete?(%Tx{state: :complete}), do: true
   def complete?(%Tx{}), do: false

test/dll/tx_test.exs

@@ -27,8 +27,8 @@ defmodule WaferDllTxTest do
 
   defp collect(tx, bytes) do
     case Tx.tx(tx) do
+      {:done, _tx} -> Enum.reverse(bytes)
       {byte, tx} -> collect(tx, [byte | bytes])
-      :done -> Enum.reverse(bytes)
     end
   end
 end

test/dll_test.exs

@@ -17,12 +17,12 @@ defmodule WaferDLLTest do
 
   def transmit(%Tx{} = tx, %Rx{} = rx) do
     case Tx.tx(tx) do
+      {:done, tx} ->
+        {tx, rx}
+
       {byte, tx} ->
         rx = Rx.rx(rx, byte)
         transmit(tx, rx)
-
-      :done ->
-        {tx, rx}
     end
   end
 end