Using HTTP range to download a file separately

download.rb

require "net/http"
require 'uri'

def download(uri_str)
  uri = URI uri_str
  Net::HTTP.new(uri.host, uri.port).start do |http|
    head = http.request_head uri.path
    length = head.content_length
    puts length

    return puts('Invalid URL') unless head.is_a? Net::HTTPSuccess

    req1 = Net::HTTP::Get.new uri.request_uri
    req2 = Net::HTTP::Get.new uri.request_uri
    req1['Range'] = "bytes=0-#{length/2-1}"
    req2['Range'] = "bytes=-#{length/2}"

    parts = {}
    threads = []
    threads << Thread.new(http) { |h| parts[1] = h.request req1 }
    threads << Thread.new(http) { |h| parts[2] = h.request req2 }

    File.open('song.mp3', 'w') do |f|
      threads.each { |th| th.join }
      f.write parts[1].body
      f.write parts[2].body
      f.close
    end
  end
end

uri = 'http://file16.top100.cn/201205262345/517316BC2FC86C1BEBF2BA1C71133352/Special_329225/%E4%BD%A0%E4%B8%8D%E7%9F%A5%E9%81%93%E7%9A%84%E4%BA%8B.mp3'
download uri

# The code above may cause exception "`rescue in rbuf_fill': Timeout::Error (Timeout::Error)", I tried to set # the `read_timeout`, but couldn't solve this problem.

# If I join the thread immediately, `Thread.new(http) { |h| parts[1] = h.request req1 }.join`, it worked. But # it make no sense, because it become sequential.

Yay Ruby!!