From: brabuhr@...
Date: 2009-09-09T12:11:49+09:00
Subject: Re: Time based loop limiting

On Tue, Sep 8, 2009 at 6:14 PM, Bertram Scharpf<lists@bertram-scharpf.de> wrote:
> Am Mittwoch, 09. Sep 2009, 01:38:33 +0900 schrieb Michael Tomer:
>> I'm trying to write a loop that will only run a certain number of times
>> per second.
>
> The proper way to do this is to call the setitimer(2) function
> that will send SIGALRM periodically to the process. It has been
> discussed a long time ago:
>
>  http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/130989
>
> Still I cannot find a setitimer mapping in the Ruby interpreter.
> So I wrote my own:
>
>  http://bertram-scharpf.homelinux.com:8808/doc_root/itimer-1.0/rdoc/index.html

Took a shot with FFI:

require  'ffi'

module LibC
  extend FFI::Library

  class Timeval < FFI::Struct
    layout :tv_sec,  :long,
           :tv_usec, :long
  end

  class Itimerval < FFI::Struct
    layout :it_interval, Timeval,
           :it_value,    Timeval
  end

  attach_function :getitimer, [:int, :pointer], :int
  attach_function :setitimer, [:int, :pointer, :pointer], :int
end


Signal.trap("SIGALRM") do
  puts "SIGALRM: #{Time.now}"
end

tv = LibC::Timeval.new
tv[:tv_sec] = 2
tv[:tv_usec] = 0

puts Time.now
LibC::setitimer(0, tv, nil)
sleep 15
puts Time.now


#=>
# Wed Sep 09 02:57:18 +0000 2009
# SIGALRM: Wed Sep 09 02:57:20 +0000 2009
# SIGALRM: Wed Sep 09 02:57:22 +0000 2009
# SIGALRM: Wed Sep 09 02:57:24 +0000 2009
# SIGALRM: Wed Sep 09 02:57:26 +0000 2009
# SIGALRM: Wed Sep 09 02:57:28 +0000 2009
# SIGALRM: Wed Sep 09 02:57:30 +0000 2009
# SIGALRM: Wed Sep 09 02:57:32 +0000 2009
# SIGALRM: Wed Sep 09 02:57:33 +0000 2009
# Wed Sep 09 02:57:33 +0000 2009