module Itimer

# File lib/itimer.rb, line 7
def self.timeout(seconds, klass=Timeout)
  ret = nil

  prev_timeout = @active_timeout
  start = Time.now
  absolute_timeout = start + seconds

  if prev_timeout && absolute_timeout > prev_timeout
    # this timer is nested in another one that will timeout before it,
    # it will never fire
    ret = yield
  else
    @counter ||= 0
    @counter += 1

    catch_name = "itimer_#{@counter}"

    timed_out = true
    @active_timeout = absolute_timeout

    exception = catch(catch_name) do
      prev_handler = Signal.trap 'ALRM' do
        begin
          raise klass
        rescue klass
          throw(catch_name, $!)
        end
      end

      set(:real, seconds)
      begin
        ret = yield
        timed_out = false
      ensure
        @active_timeout = prev_timeout
        Signal.trap('ALRM', prev_handler)

        now = Time.now
        if prev_timeout && prev_timeout - now > 0
          set(:real, prev_timeout - now)
        else
          set(:real, 0)
        end
      end
    end

    if timed_out
      raise exception
    end
  end

  return ret
end