From 389058cdf612594161d382de4d23416b938f1a23 Mon Sep 17 00:00:00 2001
From: Aleksei Magusev <lexmag@me.com>
Date: Tue, 23 Jul 2019 00:17:22 +0200
Subject: [PATCH] Optimize list and map packing

At least 10% and 20% respectively.
---
 lib/msgpax/packer.ex | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/lib/msgpax/packer.ex b/lib/msgpax/packer.ex
index 84b243e..6c11456 100644
--- a/lib/msgpax/packer.ex
+++ b/lib/msgpax/packer.ex
@@ -145,12 +145,15 @@ defimpl Msgpax.Packer, for: Map do
   end
 
   def pack(map) do
-    [format(map)] ++
-      for {key, value} <- map do
-        [@protocol.pack(key) | @protocol.pack(value)]
-      end
+    [format(map) | map |> Map.to_list() |> pack([])]
+  end
+
+  defp pack([{key, value} | rest], result) do
+    pack(rest, [@protocol.pack(key), @protocol.pack(value) | result])
   end
 
+  defp pack([], result), do: result
+
   defp format(map) do
     length = map_size(map)
 
@@ -165,12 +168,15 @@ end
 
 defimpl Msgpax.Packer, for: List do
   def pack(list) do
-    [format(list)] ++
-      for item <- list do
-        @protocol.pack(item)
-      end
+    [format(list) | list |> Enum.reverse() |> pack([])]
+  end
+
+  defp pack([item | rest], result) do
+    pack(rest, [@protocol.pack(item) | result])
   end
 
+  defp pack([], result), do: result
+
   defp format(list) do
     length = length(list)