Efficiently reading files in Ruby. From https://blog.appsignal.com/2018/07/10/ruby-magic-slurping-and-streaming-files.html

my_io.rb

class MyIO
  def initialize(filename)
    fd = IO.sysopen(filename)
    @io = IO.new(fd)
    @buffer = ""
  end

  def each(&block)
    @buffer << @io.sysread(512) until @buffer.include?($/)

    line, @buffer = @buffer.split($/, 2)

    block.call(line)
    each(&block)
  rescue EOFError
    @io.close
  end
end