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.\" ========================================================================
.\"
.IX Title "Util::TimeTracker 3"
.TH Util::TimeTracker 3 "2010-10-27" "perl v5.8.8" "User Contributed Perl Documentation"
.SH "NAME"
Log::Log4perl::Util::TimeTracker \- Track time elapsed
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  use Log::Log4perl::Util::TimeTracker;
.Ve
.PP
.Vb 1
\&  my $timer = Log::Log4perl::Util::TimeTracker->new();
.Ve
.PP
.Vb 3
\&    # equivalent to Time::HiRes::gettimeofday(), regardless
\&    # if Time::HiRes is present or not. 
\&  my($seconds, $microseconds) = $timer->gettimeofday();
.Ve
.PP
.Vb 2
\&    # reset internal timer
\&  $timer->reset();
.Ve
.PP
.Vb 2
\&    # return milliseconds since last reset
\&  $msecs = $timer->milliseconds();
.Ve
.PP
.Vb 2
\&    # return milliseconds since last call
\&  $msecs = $timer->delta_milliseconds();
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This utility module helps tracking time elapsed for PatternLayout's
date and time placeholders. Its accuracy depends on the availability
of the Time::HiRes module. If it's available, its granularity is
milliseconds, if not, seconds.
.PP
The most common use of this module is calling the \fIgettimeofday()\fR 
method:
.PP
.Vb 1
\&  my($seconds, $microseconds) = $timer->gettimeofday();
.Ve
.PP
It returns seconds and microseconds of the current epoch time. If 
Time::HiRes is installed, it will simply defer to its \fIgettimeofday()\fR
function, if it's missing, \fItime()\fR will be called instead and \f(CW$microseconds\fR
will always be 0.
.PP
To measure time elapsed in milliseconds, use the \fIreset()\fR method to 
reset the timer to the current time, followed by one or more calls to
the \fImilliseconds()\fR method:
.PP
.Vb 2
\&    # reset internal timer
\&  $timer->reset();
.Ve
.PP
.Vb 2
\&    # return milliseconds since last reset
\&  $msecs = $timer->milliseconds();
.Ve
.PP
On top of the time span between the last reset and the current time, 
the module keeps track of the time between calls to \fIdelta_milliseconds()\fR:
.PP
.Vb 1
\&  $msecs = $timer->delta_milliseconds();
.Ve
.PP
On the first call, this will return the number of milliseconds since the
last \fIreset()\fR, on subsequent calls, it will return the time elapsed in
milliseconds since the last call to \fIdelta_milliseconds()\fR instead. Note
that \fIreset()\fR also resets the time of the last call.
.PP
The internal timer of this module gets its time input from the \s-1POSIX\s0 \fItime()\fR 
function, or, if the Time::HiRes module is available, from its 
\&\fIgettimeofday()\fR function. To figure out which one it is, use
.PP
.Vb 5
\&    if( $timer->hires_available() ) {
\&        print "Hooray, we get real milliseconds!\en";
\&    } else {
\&        print "Milliseconds are just bogus\en";
\&    }
.Ve
.PP
For testing purposes, a different time source can be provided, so test
suites can simulate time passing by without actually having to wait:
.PP
.Vb 1
\&  my $start_time = time();
.Ve
.PP
.Vb 5
\&  my $timer = Log::Log4perl::Util::TimeTracker->new(
\&          time_function => sub {
\&              return $start_time++;
\&          },
\&  );
.Ve
.PP
Every call to \f(CW$timer\fR\->\fIepoch()\fR will then return a time value that is one
second ahead of the the value returned on the previous call. This also means
that every call to \fIdelta_milliseconds()\fR will return a value that exceeds
the value returned on the previous call by 1000.
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright 2002\-2009 by Mike Schilli <m@perlmeister.com> 
and Kevin Goess <cpan@goess.org>.
.PP
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.