From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2004-02-25T14:54:48+09:00
Subject: io/nonblock - blocks w/threads?


this program does not work as expected w/o inserting the 'Thread.critical'
bits - i must say i do not understand why, can someone help me understand?

  require 'tk'
  require 'open3'
  require 'io/nonblock'
  $VERBOSE=nil

  r=TkRoot.new
  l=TkLabel.new r, :text=>`ruby -e "p Time.now"`
  l.pack

  command='ruby -e "loop{p Time.now; sleep 1}"'
  i,o,e = Open3::popen3 command
  i.close
  text = nil

  Thread.new do
    loop do
      rios, = select [o,e], nil, nil
      rios.map do |rio|
        next if rio.eof?
        Thread.critical = true             # blocks w/o this
        rio.nonblock{ text = rio.read }
        Thread.critical = false            # blocks w/o this
        l.configure :text=>text
      end
    end
  end

  Tk.mainloop


is this an o.k. technique to prevent a non-blocking read not to hand a
multi-threaded ap?  i'm think of adding an asychronous processing option to my
session library using this feature... actually i suppose it'd always be o.k.
for this to be there...

-a
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