module NIO

def self.engine

* java: using Java NIO
* libev: as a C extension using libev
* select: in pure Ruby using Kernel.select
NIO implementation, one of the following (as a string): 
def self.engine
  ENGINE
end

def self.pure?(env = ENV) 

def self.pure?(env = ENV)
  # The user has explicitly opted in to non-native implementation:
  if env["NIO4R_PURE"] == "true"
    return true
  end
  # Native Ruby on Windows is not supported:
  if (Gem.win_platform? && !defined?(JRUBY_VERSION))
    return true
  end
  # M1 native extension is crashing on M1 (arm64):
  # if RUBY_PLATFORM =~ /darwin/ && RUBY_PLATFORM =~ /arm64/
  #   return true
  # end
  return false
end