fiber_schedule.rb

require 'nio'
require 'fiber'
require 'timers'
require 'io/nonblock'

class Scheduler
  def initialize
    @selector = NIO::Selector.new
    @fibers = {}
    @timers = Timers::Group.new
  end

  def io_wait(io, _events, timeout)
    @selector.register io, :rw
    @fibers[io] = Fiber.current
    if timeout
      @timers.after(timeout) do
        fibers[:io].resume
      end
    end
    Fiber.yield
  end

  def run
    until @fibers.empty?
      @selector.select(interval) do |m|
        fiber = @fibers.delete(m.io)
        @selector.deregister m.io
        fiber.resume
      end
    end
  end

  def interval
    @timers.wait_interval
  end

  def close
    run
  end

  def fiber(&block)
    fiber = Fiber.new(blocking: false, &block)
    fiber.resume
    fiber
  end
end

Thread.current.scheduler = Scheduler.new
i, o = UNIXSocket.pair

Fiber.schedule do
  message = i.read(20)
  i.close
  puts message
end

Fiber.schedule do
  o.write('Hello World')
  o.close
end