qq.rb

def chunk
  chunks = []
  break_points.each_cons(2) do |start_byte, end_byte|
    chunk = @file.read(end_byte - start_byte)
    if block_given?
      # more memory efficient, process the chunks one by one
      yield chunk
    else
      chunks << chunk
    end
  end
end

def chunk2
  # returns Enumerable lazy so we can process one chunk at a time.
  break_points.each_cons(2).lazy.map do |start_byte, end_byte|
    @file.read(end_byte - start_byte)
  end
end

IMO rewrite this as:

def chunk
  return enum_for(__method__) unless block_given?
  break_points.each_cons(2) do |start_byte, end_byte|
    yield(@file.read(end_byte - start_byte))
  end
end