4 use vars qw($VERSION $XS_VERSION @ISA @EXPORT @EXPORT_OK $AUTOLOAD);
9 @ISA = qw(Exporter DynaLoader);
12 @EXPORT_OK = qw (usleep sleep ualarm alarm gettimeofday time tv_interval
13 getitimer setitimer nanosleep
14 ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF ITIMER_REALPROF
15 d_usleep d_ualarm d_gettimeofday d_getitimer d_setitimer
19 $XS_VERSION = $VERSION;
20 $VERSION = eval $VERSION;
24 ($constname = $AUTOLOAD) =~ s/.*:://;
25 die "&Time::HiRes::constant not defined" if $constname eq 'constant';
26 my ($error, $val) = constant($constname);
28 my (undef,$file,$line) = caller;
29 die "$error at $file line $line.\n";
33 *$AUTOLOAD = sub { $val };
38 bootstrap Time::HiRes;
40 # Preloaded methods go here.
43 # probably could have been done in C
45 $b = [gettimeofday()] unless defined($b);
46 (${$b}[0] - ${$a}[0]) + ((${$b}[1] - ${$a}[1]) / 1_000_000);
49 # Autoload methods go after =cut, and are processed by the autosplit program.
56 Time::HiRes - High resolution alarm, sleep, gettimeofday, interval timers
60 use Time::HiRes qw( usleep ualarm gettimeofday tv_interval nanosleep );
62 usleep ($microseconds);
63 nanosleep ($nanoseconds);
65 ualarm ($microseconds);
66 ualarm ($microseconds, $interval_microseconds);
69 ($seconds, $microseconds) = gettimeofday;
71 $elapsed = tv_interval ( $t0, [$seconds, $microseconds]);
72 $elapsed = tv_interval ( $t0, [gettimeofday]);
73 $elapsed = tv_interval ( $t0 );
75 use Time::HiRes qw ( time alarm sleep );
77 $now_fractions = time;
78 sleep ($floating_seconds);
79 alarm ($floating_seconds);
80 alarm ($floating_seconds, $floating_interval);
82 use Time::HiRes qw( setitimer getitimer
83 ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF ITIMER_REALPROF );
85 setitimer ($which, $floating_seconds, $floating_interval );
90 The C<Time::HiRes> module implements a Perl interface to the
91 C<usleep>, C<nanosleep>, C<ualarm>, C<gettimeofday>, and
92 C<setitimer>/C<getitimer> system calls, in other words, high
93 resolution time and timers. See the L</EXAMPLES> section below and the
94 test scripts for usage; see your system documentation for the
95 description of the underlying C<nanosleep> or C<usleep>, C<ualarm>,
96 C<gettimeofday>, and C<setitimer>/C<getitimer> calls.
98 If your system lacks C<gettimeofday()> or an emulation of it you don't
99 get C<gettimeofday()> or the one-argument form of C<tv_interval()>.
100 If your system lacks all of C<nanosleep()>, C<usleep()>, and
101 C<select()>, you don't get C<Time::HiRes::usleep()>,
102 C<Time::HiRes::nanosleep()>, or C<Time::HiRes::sleep()>. If your
103 system lacks both C<ualarm()> and C<setitimer()> you don't get
104 C<Time::HiRes::ualarm()> or C<Time::HiRes::alarm()>.
106 If you try to import an unimplemented function in the C<use> statement
107 it will fail at compile time.
109 If your subsecond sleeping is implemented with C<nanosleep()> instead
110 of C<usleep()>, you can mix subsecond sleeping with signals since
111 C<nanosleep()> does not use signals. This, however, is not portable,
112 and you should first check for the truth value of
113 C<&Time::HiRes::d_nanosleep> to see whether you have nanosleep, and
114 then carefully read your C<nanosleep()> C API documentation for any
117 If you are using C<nanosleep> for something else than mixing sleeping
118 with signals, give some thought to whether Perl is the tool you should
119 be using for work requiring nanosecond accuracies.
121 The following functions can be imported from this module.
122 No functions are exported by default.
126 =item gettimeofday ()
128 In array context returns a two-element array with the seconds and
129 microseconds since the epoch. In scalar context returns floating
130 seconds like C<Time::HiRes::time()> (see below).
132 =item usleep ( $useconds )
134 Sleeps for the number of microseconds (millionths of a second)
135 specified. Returns the number of microseconds actually slept. Can
136 sleep for more than one second, unlike the C<usleep> system call. See
137 also C<Time::HiRes::usleep()> and C<Time::HiRes::sleep()>.
139 Do not expect usleep() to be exact down to one microsecond.
141 =item nanosleep ( $nanoseconds )
143 Sleeps for the number of nanoseconds (1e9ths of a second) specified.
144 Returns the number of nanoseconds actually slept (accurate only to
145 microseconds, the nearest thousand of them). Can sleep for more than
146 one second. See also C<Time::HiRes::sleep()> and
147 C<Time::HiRes::usleep()>.
149 Do not expect nanosleep() to be exact down to one nanosecond.
150 Getting even accuracy of one thousand nanoseconds is good.
152 =item ualarm ( $useconds [, $interval_useconds ] )
154 Issues a C<ualarm> call; the C<$interval_useconds> is optional and
155 will be zero if unspecified, resulting in C<alarm>-like behaviour.
157 Note that the interaction between alarms and sleeps is unspecified.
161 tv_interval ( $ref_to_gettimeofday [, $ref_to_later_gettimeofday] )
163 Returns the floating seconds between the two times, which should have
164 been returned by C<gettimeofday()>. If the second argument is omitted,
165 then the current time is used.
169 Returns a floating seconds since the epoch. This function can be
170 imported, resulting in a nice drop-in replacement for the C<time>
171 provided with core Perl; see the L</EXAMPLES> below.
173 B<NOTE 1>: This higher resolution timer can return values either less
174 or more than the core C<time()>, depending on whether your platform
175 rounds the higher resolution timer values up, down, or to the nearest second
176 to get the core C<time()>, but naturally the difference should be never
177 more than half a second.
179 B<NOTE 2>: Since Sunday, September 9th, 2001 at 01:46:40 AM GMT, when
180 the C<time()> seconds since epoch rolled over to 1_000_000_000, the
181 default floating point format of Perl and the seconds since epoch have
182 conspired to produce an apparent bug: if you print the value of
183 C<Time::HiRes::time()> you seem to be getting only five decimals, not
184 six as promised (microseconds). Not to worry, the microseconds are
185 there (assuming your platform supports such granularity in the first
186 place). What is going on is that the default floating point format of
187 Perl only outputs 15 digits. In this case that means ten digits
188 before the decimal separator and five after. To see the microseconds
189 you can use either C<printf>/C<sprintf> with C<"%.6f">, or the
190 C<gettimeofday()> function in list context, which will give you the
191 seconds and microseconds as two separate values.
193 =item sleep ( $floating_seconds )
195 Sleeps for the specified amount of seconds. Returns the number of
196 seconds actually slept (a floating point value). This function can
197 be imported, resulting in a nice drop-in replacement for the C<sleep>
198 provided with perl, see the L</EXAMPLES> below.
200 Note that the interaction between alarms and sleeps is unspecified.
202 =item alarm ( $floating_seconds [, $interval_floating_seconds ] )
204 The C<SIGALRM> signal is sent after the specified number of seconds.
205 Implemented using C<ualarm()>. The C<$interval_floating_seconds> argument
206 is optional and will be zero if unspecified, resulting in C<alarm()>-like
207 behaviour. This function can be imported, resulting in a nice drop-in
208 replacement for the C<alarm> provided with perl, see the L</EXAMPLES> below.
210 B<NOTE 1>: With some combinations of operating systems and Perl
211 releases C<SIGALRM> restarts C<select()>, instead of interrupting it.
212 This means that an C<alarm()> followed by a C<select()> may together
213 take the sum of the times specified for the the C<alarm()> and the
214 C<select()>, not just the time of the C<alarm()>.
216 Note that the interaction between alarms and sleeps is unspecified.
218 =item setitimer ( $which, $floating_seconds [, $interval_floating_seconds ] )
220 Start up an interval timer: after a certain time, a signal arrives,
221 and more signals may keep arriving at certain intervals. To disable
222 an "itimer", use C<$floating_seconds> of zero. If the
223 C<$interval_floating_seconds> is set to zero (or unspecified), the
224 timer is disabled B<after> the next delivered signal.
226 Use of interval timers may interfere with C<alarm()>, C<sleep()>,
227 and C<usleep()>. In standard-speak the "interaction is unspecified",
228 which means that I<anything> may happen: it may work, it may not.
230 In scalar context, the remaining time in the timer is returned.
232 In list context, both the remaining time and the interval are returned.
234 There are usually three or four interval timers available: the
235 C<$which> can be C<ITIMER_REAL>, C<ITIMER_VIRTUAL>, C<ITIMER_PROF>, or
236 C<ITIMER_REALPROF>. Note that which ones are available depends: true
237 UNIX platforms usually have the first three, but (for example) Win32
238 and Cygwin have only C<ITIMER_REAL>, and only Solaris seems to have
239 C<ITIMER_REALPROF> (which is used to profile multithreaded programs).
241 C<ITIMER_REAL> results in C<alarm()>-like behaviour. Time is counted in
242 I<real time>; that is, wallclock time. C<SIGALRM> is delivered when
245 C<ITIMER_VIRTUAL> counts time in (process) I<virtual time>; that is,
246 only when the process is running. In multiprocessor/user/CPU systems
247 this may be more or less than real or wallclock time. (This time is
248 also known as the I<user time>.) C<SIGVTALRM> is delivered when the
251 C<ITIMER_PROF> counts time when either the process virtual time or when
252 the operating system is running on behalf of the process (such as I/O).
253 (This time is also known as the I<system time>.) (The sum of user
254 time and system time is known as the I<CPU time>.) C<SIGPROF> is
255 delivered when the timer expires. C<SIGPROF> can interrupt system calls.
257 The semantics of interval timers for multithreaded programs are
258 system-specific, and some systems may support additional interval
259 timers. See your C<setitimer()> documentation.
261 =item getitimer ( $which )
263 Return the remaining time in the interval timer specified by C<$which>.
265 In scalar context, the remaining time is returned.
267 In list context, both the remaining time and the interval are returned.
268 The interval is always what you put in using C<setitimer()>.
274 use Time::HiRes qw(usleep ualarm gettimeofday tv_interval);
276 $microseconds = 750_000;
277 usleep $microseconds;
279 # signal alarm in 2.5s & every .1s thereafter
280 ualarm 2_500_000, 100_000;
282 # get seconds and microseconds since the epoch
283 ($s, $usec) = gettimeofday;
285 # measure elapsed time
286 # (could also do by subtracting 2 gettimeofday return values)
287 $t0 = [gettimeofday];
288 # do bunch of stuff here
289 $t1 = [gettimeofday];
291 $t0_t1 = tv_interval $t0, $t1;
293 $elapsed = tv_interval ($t0, [gettimeofday]);
294 $elapsed = tv_interval ($t0); # equivalent code
297 # replacements for time, alarm and sleep that know about
301 $now_fractions = Time::HiRes::time;
302 Time::HiRes::sleep (2.5);
303 Time::HiRes::alarm (10.6666666);
305 use Time::HiRes qw ( time alarm sleep );
306 $now_fractions = time;
310 # Arm an interval timer to go off first at 10 seconds and
311 # after that every 2.5 seconds, in process virtual time
313 use Time::HiRes qw ( setitimer ITIMER_VIRTUAL time );
315 $SIG{VTALRM} = sub { print time, "\n" };
316 setitimer(ITIMER_VIRTUAL, 10, 2.5);
320 In addition to the perl API described above, a C API is available for
321 extension writers. The following C functions are available in the
325 --------------- ----------------------
326 Time::NVtime double (*)()
327 Time::U2time void (*)(pTHX_ UV ret[2])
329 Both functions return equivalent information (like C<gettimeofday>)
330 but with different representations. The names C<NVtime> and C<U2time>
331 were selected mainly because they are operating system independent.
332 (C<gettimeofday> is Unix-centric, though some platforms like Win32 and
333 VMS have emulations for it.)
335 Here is an example of using C<NVtime> from C:
337 double (*myNVtime)(); /* Returns -1 on failure. */
338 SV **svp = hv_fetch(PL_modglobal, "Time::NVtime", 12, 0);
339 if (!svp) croak("Time::HiRes is required");
340 if (!SvIOK(*svp)) croak("Time::NVtime isn't a function pointer");
341 myNVtime = INT2PTR(double(*)(), SvIV(*svp));
342 printf("The current time is: %f\n", (*myNVtime)());
346 =head2 negative time not invented yet
348 You tried to use a negative time argument.
350 =head2 internal error: useconds < 0 (unsigned ... signed ...)
352 Something went horribly wrong-- the number of microseconds that cannot
353 become negative just became negative. Maybe your compiler is broken?
357 Notice that the core C<time()> maybe rounding rather than truncating.
358 What this means is that the core C<time()> may be reporting the time
359 as one second later than C<gettimeofday()> and C<Time::HiRes::time()>.
361 Adjusting the system clock (either manually or by services like ntp)
362 may cause problems, especially for long running programs that assume
363 a monotonously increasing time (note that all platforms do not adjust
364 time as gracefully as UNIX ntp does). For example in Win32 (and derived
365 platforms like Cygwin and MinGW) the Time::HiRes::time() may temporarily
366 drift off from the system clock (and the original time()) by up to 0.5
367 seconds. Time::HiRes will notice this eventually and recalibrate.
371 L<BSD::Resource>, L<Time::TAI64>.
375 D. Wegscheid <wegscd@whirlpool.com>
376 R. Schertler <roderick@argon.org>
377 J. Hietaniemi <jhi@iki.fi>
378 G. Aas <gisle@aas.no>
380 =head1 COPYRIGHT AND LICENSE
382 Copyright (c) 1996-2002 Douglas E. Wegscheid. All rights reserved.
384 Copyright (c) 2002, 2003, 2004, 2005 Jarkko Hietaniemi. All rights reserved.
386 This program is free software; you can redistribute it and/or modify
387 it under the same terms as Perl itself.