defmodule Protox.Zigzag do
  @moduledoc false
  # Internal. Map integers to positive integers as LEB128 can only work on the latters.

  import Bitwise

  @spec encode(integer) :: non_neg_integer
  def encode(v) when v >= 0, do: v * 2
  def encode(v), do: v * -2 - 1

  @spec decode(non_neg_integer) :: integer
  def decode(v) when (v &&& 1) == 0, do: v >>> 1
  def decode(v), do: -((v + 1) >>> 1)
end