Do not use private APIs in StringIO

Author: josevalim

lib/elixir/lib/string_io.ex

@@ -366,6 +366,7 @@ defmodule StringIO do
  defp get_until(encoding, prompt, mod, fun, args, %{input: input} = state) do
  case get_until(input, encoding, mod, fun, args, [], 0) do
  {result, input, count} ->
+ # Convert :eof to "" as they are both treated the same
  input =
  case input do
  :eof -> ""
@@ -392,7 +393,7 @@ defmodule StringIO do
  defp get_until(chars, encoding, mod, fun, args, continuation, count) do
  case bytes_until_eol(chars, encoding, 0) do
  {kind, size} when kind in [:split, :replace_split] ->
- {line, rest} = :erlang.split_binary(chars, size)
+ <<line::binary-size(size), rest::binary>> = chars
 
  case apply(mod, fun, [continuation, binary_to_list(line, encoding) | args]) do
  {:done, result, :eof} ->