4 use vars qw($VERSION $XS_VERSION @ISA @EXPORT @EXPORT_OK $AUTOLOAD);
9 @ISA = qw(Exporter DynaLoader);
13 @EXPORT_OK = qw (usleep sleep ualarm alarm gettimeofday time tv_interval
14 getitimer setitimer nanosleep
15 ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF ITIMER_REALPROF
16 d_usleep d_ualarm d_gettimeofday d_getitimer d_setitimer
20 $XS_VERSION = $VERSION;
21 $VERSION = eval $VERSION;
25 ($constname = $AUTOLOAD) =~ s/.*:://;
26 die "&Time::HiRes::constant not defined" if $constname eq 'constant';
27 my ($error, $val) = constant($constname);
28 if ($error) { die $error; }
31 *$AUTOLOAD = sub { $val };
38 XSLoader::load('Time::HiRes', $XS_VERSION);
42 local @ISA = qw(DynaLoader);
43 bootstrap Time::HiRes $XS_VERSION;
46 # Preloaded methods go here.
49 # probably could have been done in C
51 $b = [gettimeofday()] unless defined($b);
52 (${$b}[0] - ${$a}[0]) + ((${$b}[1] - ${$a}[1]) / 1_000_000);
55 # Autoload methods go after =cut, and are processed by the autosplit program.
62 Time::HiRes - High resolution alarm, sleep, gettimeofday, interval timers
66 use Time::HiRes qw( usleep ualarm gettimeofday tv_interval nanosleep );
68 usleep ($microseconds);
69 nanosleep ($nanoseconds);
71 ualarm ($microseconds);
72 ualarm ($microseconds, $interval_microseconds);
75 ($seconds, $microseconds) = gettimeofday;
77 $elapsed = tv_interval ( $t0, [$seconds, $microseconds]);
78 $elapsed = tv_interval ( $t0, [gettimeofday]);
79 $elapsed = tv_interval ( $t0 );
81 use Time::HiRes qw ( time alarm sleep );
83 $now_fractions = time;
84 sleep ($floating_seconds);
85 alarm ($floating_seconds);
86 alarm ($floating_seconds, $floating_interval);
88 use Time::HiRes qw( setitimer getitimer
89 ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF ITIMER_REALPROF );
91 setitimer ($which, $floating_seconds, $floating_interval );
96 The C<Time::HiRes> module implements a Perl interface to the
97 C<usleep>, C<nanosleep>, C<ualarm>, C<gettimeofday>, and
98 C<setitimer>/C<getitimer> system calls, in other words, high
99 resolution time and timers. See the L</EXAMPLES> section below and the
100 test scripts for usage; see your system documentation for the
101 description of the underlying C<nanosleep> or C<usleep>, C<ualarm>,
102 C<gettimeofday>, and C<setitimer>/C<getitimer> calls.
104 If your system lacks C<gettimeofday()> or an emulation of it you don't
105 get C<gettimeofday()> or the one-argument form of C<tv_interval()>.
106 If your system lacks all of C<nanosleep()>, C<usleep()>, and
107 C<select()>, you don't get C<Time::HiRes::usleep()>,
108 C<Time::HiRes::nanosleep()>, or C<Time::HiRes::sleep()>. If your
109 system lacks both C<ualarm()> and C<setitimer()> you don't get
110 C<Time::HiRes::ualarm()> or C<Time::HiRes::alarm()>.
112 If you try to import an unimplemented function in the C<use> statement
113 it will fail at compile time.
115 If your subsecond sleeping is implemented with C<nanosleep()> instead
116 of C<usleep()>, you can mix subsecond sleeping with signals since
117 C<nanosleep()> does not use signals. This, however, is not portable,
118 and you should first check for the truth value of
119 C<&Time::HiRes::d_nanosleep> to see whether you have nanosleep, and
120 then carefully read your C<nanosleep()> C API documentation for any
123 Unless using C<nanosleep> for mixing sleeping with signals, give
124 some thought to whether Perl is the tool you should be using for
125 work requiring nanosecond accuracies.
127 The following functions can be imported from this module.
128 No functions are exported by default.
132 =item gettimeofday ()
134 In array context returns a two-element array with the seconds and
135 microseconds since the epoch. In scalar context returns floating
136 seconds like C<Time::HiRes::time()> (see below).
138 =item usleep ( $useconds )
140 Sleeps for the number of microseconds (millionths of a second)
141 specified. Returns the number of microseconds actually slept. Can
142 sleep for more than one second, unlike the C<usleep> system call. See
143 also C<Time::HiRes::usleep()> and C<Time::HiRes::sleep()>.
145 Do not expect usleep() to be exact down to one microsecond.
147 =item nanosleep ( $nanoseconds )
149 Sleeps for the number of nanoseconds (1e9ths of a second) specified.
150 Returns the number of nanoseconds actually slept (accurate only to
151 microseconds, the nearest thousand of them). Can sleep for more than
152 one second. See also C<Time::HiRes::sleep()> and
153 C<Time::HiRes::usleep()>.
155 Do not expect nanosleep() to be exact down to one nanosecond.
156 Getting even accuracy of one thousand nanoseconds is good.
158 =item ualarm ( $useconds [, $interval_useconds ] )
160 Issues a C<ualarm> call; the C<$interval_useconds> is optional and
161 will be zero if unspecified, resulting in C<alarm>-like behaviour.
163 Note that the interaction between alarms and sleeps is unspecified.
167 tv_interval ( $ref_to_gettimeofday [, $ref_to_later_gettimeofday] )
169 Returns the floating seconds between the two times, which should have
170 been returned by C<gettimeofday()>. If the second argument is omitted,
171 then the current time is used.
175 Returns a floating seconds since the epoch. This function can be
176 imported, resulting in a nice drop-in replacement for the C<time>
177 provided with core Perl; see the L</EXAMPLES> below.
179 B<NOTE 1>: This higher resolution timer can return values either less
180 or more than the core C<time()>, depending on whether your platform
181 rounds the higher resolution timer values up, down, or to the nearest second
182 to get the core C<time()>, but naturally the difference should be never
183 more than half a second.
185 B<NOTE 2>: Since Sunday, September 9th, 2001 at 01:46:40 AM GMT, when
186 the C<time()> seconds since epoch rolled over to 1_000_000_000, the
187 default floating point format of Perl and the seconds since epoch have
188 conspired to produce an apparent bug: if you print the value of
189 C<Time::HiRes::time()> you seem to be getting only five decimals, not
190 six as promised (microseconds). Not to worry, the microseconds are
191 there (assuming your platform supports such granularity in the first
192 place). What is going on is that the default floating point format of
193 Perl only outputs 15 digits. In this case that means ten digits
194 before the decimal separator and five after. To see the microseconds
195 you can use either C<printf>/C<sprintf> with C<"%.6f">, or the
196 C<gettimeofday()> function in list context, which will give you the
197 seconds and microseconds as two separate values.
199 =item sleep ( $floating_seconds )
201 Sleeps for the specified amount of seconds. Returns the number of
202 seconds actually slept (a floating point value). This function can
203 be imported, resulting in a nice drop-in replacement for the C<sleep>
204 provided with perl, see the L</EXAMPLES> below.
206 Note that the interaction between alarms and sleeps is unspecified.
208 =item alarm ( $floating_seconds [, $interval_floating_seconds ] )
210 The C<SIGALRM> signal is sent after the specified number of seconds.
211 Implemented using C<ualarm()>. The C<$interval_floating_seconds> argument
212 is optional and will be zero if unspecified, resulting in C<alarm()>-like
213 behaviour. This function can be imported, resulting in a nice drop-in
214 replacement for the C<alarm> provided with perl, see the L</EXAMPLES> below.
216 B<NOTE 1>: With some combinations of operating systems and Perl
217 releases C<SIGALRM> restarts C<select()>, instead of interrupting it.
218 This means that an C<alarm()> followed by a C<select()> may together
219 take the sum of the times specified for the the C<alarm()> and the
220 C<select()>, not just the time of the C<alarm()>.
222 Note that the interaction between alarms and sleeps is unspecified.
224 =item setitimer ( $which, $floating_seconds [, $interval_floating_seconds ] )
226 Start up an interval timer: after a certain time, a signal arrives,
227 and more signals may keep arriving at certain intervals. To disable
228 an "itimer", use C<$floating_seconds> of zero. If the
229 C<$interval_floating_seconds> is set to zero (or unspecified), the
230 timer is disabled B<after> the next delivered signal.
232 Use of interval timers may interfere with C<alarm()>, C<sleep()>,
233 and C<usleep()>. In standard-speak the "interaction is unspecified",
234 which means that I<anything> may happen: it may work, it may not.
236 In scalar context, the remaining time in the timer is returned.
238 In list context, both the remaining time and the interval are returned.
240 There are usually three or four interval timers available: the
241 C<$which> can be C<ITIMER_REAL>, C<ITIMER_VIRTUAL>, C<ITIMER_PROF>, or
242 C<ITIMER_REALPROF>. Note that which ones are available depends: true
243 UNIX platforms usually have the first three, but (for example) Win32
244 and Cygwin have only C<ITIMER_REAL>, and only Solaris seems to have
245 C<ITIMER_REALPROF> (which is used to profile multithreaded programs).
247 C<ITIMER_REAL> results in C<alarm()>-like behaviour. Time is counted in
248 I<real time>; that is, wallclock time. C<SIGALRM> is delivered when
251 C<ITIMER_VIRTUAL> counts time in (process) I<virtual time>; that is,
252 only when the process is running. In multiprocessor/user/CPU systems
253 this may be more or less than real or wallclock time. (This time is
254 also known as the I<user time>.) C<SIGVTALRM> is delivered when the
257 C<ITIMER_PROF> counts time when either the process virtual time or when
258 the operating system is running on behalf of the process (such as I/O).
259 (This time is also known as the I<system time>.) (The sum of user
260 time and system time is known as the I<CPU time>.) C<SIGPROF> is
261 delivered when the timer expires. C<SIGPROF> can interrupt system calls.
263 The semantics of interval timers for multithreaded programs are
264 system-specific, and some systems may support additional interval
265 timers. See your C<setitimer()> documentation.
267 =item getitimer ( $which )
269 Return the remaining time in the interval timer specified by C<$which>.
271 In scalar context, the remaining time is returned.
273 In list context, both the remaining time and the interval are returned.
274 The interval is always what you put in using C<setitimer()>.
280 use Time::HiRes qw(usleep ualarm gettimeofday tv_interval);
282 $microseconds = 750_000;
283 usleep $microseconds;
285 # signal alarm in 2.5s & every .1s thereafter
286 ualarm 2_500_000, 100_000;
288 # get seconds and microseconds since the epoch
289 ($s, $usec) = gettimeofday;
291 # measure elapsed time
292 # (could also do by subtracting 2 gettimeofday return values)
293 $t0 = [gettimeofday];
294 # do bunch of stuff here
295 $t1 = [gettimeofday];
297 $t0_t1 = tv_interval $t0, $t1;
299 $elapsed = tv_interval ($t0, [gettimeofday]);
300 $elapsed = tv_interval ($t0); # equivalent code
303 # replacements for time, alarm and sleep that know about
307 $now_fractions = Time::HiRes::time;
308 Time::HiRes::sleep (2.5);
309 Time::HiRes::alarm (10.6666666);
311 use Time::HiRes qw ( time alarm sleep );
312 $now_fractions = time;
316 # Arm an interval timer to go off first at 10 seconds and
317 # after that every 2.5 seconds, in process virtual time
319 use Time::HiRes qw ( setitimer ITIMER_VIRTUAL time );
321 $SIG{VTALRM} = sub { print time, "\n" };
322 setitimer(ITIMER_VIRTUAL, 10, 2.5);
326 In addition to the perl API described above, a C API is available for
327 extension writers. The following C functions are available in the
331 --------------- ----------------------
332 Time::NVtime double (*)()
333 Time::U2time void (*)(UV ret[2])
335 Both functions return equivalent information (like C<gettimeofday>)
336 but with different representations. The names C<NVtime> and C<U2time>
337 were selected mainly because they are operating system independent.
338 (C<gettimeofday> is Unix-centric, though some platforms like VMS have
341 Here is an example of using C<NVtime> from C:
343 double (*myNVtime)(); /* Returns -1 on failure. */
344 SV **svp = hv_fetch(PL_modglobal, "Time::NVtime", 12, 0);
345 if (!svp) croak("Time::HiRes is required");
346 if (!SvIOK(*svp)) croak("Time::NVtime isn't a function pointer");
347 myNVtime = INT2PTR(double(*)(), SvIV(*svp));
348 printf("The current time is: %f\n", (*myNVtime)());
352 =head2 negative time not invented yet
354 You tried to use a negative time argument.
356 =head2 internal error: useconds < 0 (unsigned ... signed ...)
358 Something went horribly wrong-- the number of microseconds that cannot
359 become negative just became negative. Maybe your compiler is broken?
363 Notice that the core C<time()> maybe rounding rather than truncating.
364 What this means is that the core C<time()> may be reporting the time
365 as one second later than C<gettimeofday()> and C<Time::HiRes::time()>.
367 Adjusting the system clock (either manually or by services like ntp)
368 may cause problems, especially for long running programs that assume
369 a monotonously increasing time (note that all platforms do not adjust
370 time as gracefully as UNIX ntp does). For example in Win32 (and derived
371 platforms like Cygwin and MinGW) the Time::HiRes::time() may temporarily
372 drift off from the system clock (and the original time()) by up to 0.5
373 seconds. Time::HiRes will notice this eventually and recalibrate.
377 L<BSD::Resource>, L<Time::TAI64>.
381 D. Wegscheid <wegscd@whirlpool.com>
382 R. Schertler <roderick@argon.org>
383 J. Hietaniemi <jhi@iki.fi>
384 G. Aas <gisle@aas.no>
386 =head1 COPYRIGHT AND LICENSE
388 Copyright (c) 1996-2002 Douglas E. Wegscheid. All rights reserved.
390 Copyright (c) 2002,2003,2004 Jarkko Hietaniemi. All rights reserved.
392 This program is free software; you can redistribute it and/or modify
393 it under the same terms as Perl itself.