chunked_read.rb

#!/usr/bin/env ruby

class Main
  require 'net/http'
  require 'fileutils'
  require 'thwait'

  def initialize
    @dir = './chunked_data'

    FileUtils.rm_rf   @dir
    FileUtils.mkdir_p @dir

    @size_limit = 2 * 1000 ** 2
  end

  def run
    http = Net::HTTP.new('ftp.yz.yamagata-u.ac.jp')
    http.read_timeout = 5

    pos = 1
    chunk = ''

    threads = []
    http.request_get('/pub/network/apache/httpd/httpd-2.4.34.tar.bz2') do |response|
      response.read_body do |data|
        chunk += data

        # split & save content (async)
        if chunk.size > @size_limit
          threads << Thread.new(pos, chunk) do |p, c|
            save_content p, c
          end

          chunk = ''
          pos += 1
        end
      end
    end

    # save the remnant (sync)
    if chunk.size.positive?
      save_content pos, chunk
    end

    # wait all threads done
    ThreadsWait.new(*threads)

    puts 'done'
  end

  def save_content(pos, chunk)
    sleep 2

    File.open file(pos), 'wb' do |io|
      io.write chunk
    end

    puts pos
  end

  def file(pos)
    File.join(@dir, '%02d.bin' % pos)
  end
end

Main.new.run