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DelayLine - Simple time-delay data stucture


    use DelayLine;

    my $dl = DelayLine->new(delay => $defaultdelay);


    [ ... ]

    if (my $ob = $dl->out()) {
        # do stuff with $ob


The DelayLine is a simple two-port data structure, like a FIFO, but with variable delay. Each object put into the input of the DelayLine will appear on the output only after some pre-determined amount of time has elapsed. This time can be set as a default for the DelayLine, or can be individually overridden for each object put into the DelayLine.

If the default delay time is set to zero, and is not overridden for the individual objects, the DelayLine mimics a straightforward FIFO.

The DelayLine accepts any scalar value as input, including references.

The DelayLine is a very useful component when building simple event loops.


DelayLine provides the following methods:

DelayLine->new( [ delay => DELAY [, debug => DEBUG ]] )

Returns a newly created DelayLine object.

The default delay is 0 seconds, unless an optional DELAY time in seconds is given.

Debugging is turned off by default. Setting DEBUG to true, enables debugging output to STDOUT.

The parameter naming style is very flexible: the keyword can be in lower, upper or mixed case, and can be optionally prefixed with a dash. Thus, the following are all equivalent:

  $dl = DelayLine->new( -delay => 42 );
  $dl = DelayLine->new(  delay => 42 );
  $dl = DelayLine->new( -Delay => 42 );
  $dl = DelayLine->new(  DELAY => 42 );
  $dl = DelayLine->new( -deLaY => 42 );

new() can be called as a class (static) or object method. Calling new() as an object method is only a convenience; no data from the original DelayLine is carried over into the newly created object.

$DL->in( OBJ [, DELAY ] )

This method puts object OBJ into DelayLine $DL.

The object OBJ can be any scalar value, including references.

The default delay as set in the new() method is used, unless overridden by setting DELAY.


This method fetches objects from the out from the DelayLine $DL.

Returns the first of the timed-out objects, if any.

Returns undef if the DelayLine is empty, of if no objects in the DelayLine have timed out yet.

$DL->delay( [ DELAY ] )
Returns the current default delay setting of the DelayLine. If the optional value DELAY is set, sets a new default delay value.
$DL->debug( [ DEBUG ] )

Returns the current debug setting of the DelayLine. If the optional value DEBUG is set, sets a new debug value.

If the debug value is set (true), calling any of the 'active' methods (in() or out() will yield a short debug message on STDERR.


This is a fairly simple module, so no serious bugs are expected. Patches are welcome, though.


v0.02 - 2000-jul-22
Fixed test for multiple unknown args. Removed superfluous test output. Streamlined debug output.
v0.01 - 2000-jul-13

Initial release.


Copyright (c) 2000 Lars Thegler. All rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.


Lars Thegler <>