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
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);
27 if ($error) { die $error; }
30 *$AUTOLOAD = sub { $val };
35 bootstrap Time::HiRes;
37 # Preloaded methods go here.
40 # probably could have been done in C
42 $b = [gettimeofday()] unless defined($b);
43 (${$b}[0] - ${$a}[0]) + ((${$b}[1] - ${$a}[1]) / 1_000_000);
46 # Autoload methods go after =cut, and are processed by the autosplit program.
53 Time::HiRes - High resolution alarm, sleep, gettimeofday, interval timers
57 use Time::HiRes qw( usleep ualarm gettimeofday tv_interval );
59 usleep ($microseconds);
61 ualarm ($microseconds);
62 ualarm ($microseconds, $interval_microseconds);
65 ($seconds, $microseconds) = gettimeofday;
67 $elapsed = tv_interval ( $t0, [$seconds, $microseconds]);
68 $elapsed = tv_interval ( $t0, [gettimeofday]);
69 $elapsed = tv_interval ( $t0 );
71 use Time::HiRes qw ( time alarm sleep );
73 $now_fractions = time;
74 sleep ($floating_seconds);
75 alarm ($floating_seconds);
76 alarm ($floating_seconds, $floating_interval);
78 use Time::HiRes qw( setitimer getitimer
79 ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF ITIMER_REALPROF );
81 setitimer ($which, $floating_seconds, $floating_interval );
86 The C<Time::HiRes> module implements a Perl interface to the
87 C<usleep>, C<ualarm>, C<gettimeofday>, and C<setitimer>/C<getitimer>
88 system calls, in other words, high resolution time and timers. See the
89 L</EXAMPLES> section below and the test scripts for usage; see your
90 system documentation for the description of the underlying
91 C<nanosleep> or C<usleep>, C<ualarm>, C<gettimeofday>, and
92 C<setitimer>/C<getitimer> calls.
94 If your system lacks C<gettimeofday()> or an emulation of it you don't
95 get C<gettimeofday()> or the one-argument form of C<tv_interval()>.
96 If your system lacks all of C<nanosleep()>, C<usleep()>, and
97 C<select()>, you don't get C<Time::HiRes::usleep()> or
98 C<Time::HiRes::sleep()>. If your system lacks both C<ualarm()> and
99 C<setitimer()> you don't get C<Time::HiRes::ualarm()> or
100 C<Time::HiRes::alarm()>.
102 If you try to import an unimplemented function in the C<use> statement
103 it will fail at compile time.
105 If your subsecond sleeping is implemented with C<nanosleep()> instead
106 of C<usleep()>, you can mix subsecond sleeping with signals since
107 C<nanosleep()> does not use signals. This, however is unportable, and
108 you should first check for the truth value of
109 C<&Time::HiRes::d_nanosleep> to see whether you have nanosleep, and
110 then carefully read your C<nanosleep()> C API documentation for any
111 peculiarities. (There is no separate interface to call
112 C<nanosleep()>; just use C<Time::HiRes::sleep()> or
113 C<Time::HiRes::usleep()> with small enough values.)
115 Unless using C<nanosleep> for mixing sleeping with signals, give
116 some thought to whether Perl is the tool you should be using for
117 work requiring nanosecond accuracies.
119 The following functions can be imported from this module.
120 No functions are exported by default.
124 =item gettimeofday ()
126 In array context returns a two-element array with the seconds and
127 microseconds since the epoch. In scalar context returns floating
128 seconds like C<Time::HiRes::time()> (see below).
130 =item usleep ( $useconds )
132 Sleeps for the number of microseconds specified. Returns the number
133 of microseconds actually slept. Can sleep for more than one second,
134 unlike the C<usleep> system call. See also C<Time::HiRes::sleep()> below.
136 =item ualarm ( $useconds [, $interval_useconds ] )
138 Issues a C<ualarm> call; the C<$interval_useconds> is optional and
139 will be zero if unspecified, resulting in C<alarm>-like behaviour.
143 tv_interval ( $ref_to_gettimeofday [, $ref_to_later_gettimeofday] )
145 Returns the floating seconds between the two times, which should have
146 been returned by C<gettimeofday()>. If the second argument is omitted,
147 then the current time is used.
151 Returns a floating seconds since the epoch. This function can be
152 imported, resulting in a nice drop-in replacement for the C<time>
153 provided with core Perl; see the L</EXAMPLES> below.
155 B<NOTE 1>: This higher resolution timer can return values either less
156 or more than the core C<time()>, depending on whether your platform
157 rounds the higher resolution timer values up, down, or to the nearest second
158 to get the core C<time()>, but naturally the difference should be never
159 more than half a second.
161 B<NOTE 2>: Since Sunday, September 9th, 2001 at 01:46:40 AM GMT, when
162 the C<time()> seconds since epoch rolled over to 1_000_000_000, the
163 default floating point format of Perl and the seconds since epoch have
164 conspired to produce an apparent bug: if you print the value of
165 C<Time::HiRes::time()> you seem to be getting only five decimals, not
166 six as promised (microseconds). Not to worry, the microseconds are
167 there (assuming your platform supports such granularity in first
168 place). What is going on is that the default floating point format of
169 Perl only outputs 15 digits. In this case that means ten digits
170 before the decimal separator and five after. To see the microseconds
171 you can use either C<printf>/C<sprintf> with C<"%.6f">, or the
172 C<gettimeofday()> function in list context, which will give you the
173 seconds and microseconds as two separate values.
175 =item sleep ( $floating_seconds )
177 Sleeps for the specified amount of seconds. Returns the number of
178 seconds actually slept (a floating point value). This function can be
179 imported, resulting in a nice drop-in replacement for the C<sleep>
180 provided with perl, see the L</EXAMPLES> below.
182 =item alarm ( $floating_seconds [, $interval_floating_seconds ] )
184 The C<SIGALRM> signal is sent after the specified number of seconds.
185 Implemented using C<ualarm()>. The C<$interval_floating_seconds> argument
186 is optional and will be zero if unspecified, resulting in C<alarm()>-like
187 behaviour. This function can be imported, resulting in a nice drop-in
188 replacement for the C<alarm> provided with perl, see the L</EXAMPLES> below.
190 B<NOTE 1>: With some operating system and Perl release combinations
191 C<SIGALRM> restarts C<select()>, instead of interuping it.
192 This means that an C<alarm()> followed by a C<select()>
193 may together take the sum of the times specified for the the
194 C<alarm()> and the C<select()>, not just the time of the C<alarm()>.
196 =item setitimer ( $which, $floating_seconds [, $interval_floating_seconds ] )
198 Start up an interval timer: after a certain time, a signal arrives,
199 and more signals may keep arriving at certain intervals. To disable a
200 timer, use C<$floating_seconds> of zero. If the C<$interval_floating_seconds>
201 is set to zero (or unspecified), the timer is disabled B<after> the
202 next delivered signal.
204 Use of interval timers may interfere with C<alarm()>, C<sleep()>,
205 and C<usleep()>. In standard-speak the "interaction is unspecified",
206 which means that I<anything> may happen: it may work, it may not.
208 In scalar context, the remaining time in the timer is returned.
210 In list context, both the remaining time and the interval are returned.
212 There are usually three or four interval timers available: the
213 C<$which> can be C<ITIMER_REAL>, C<ITIMER_VIRTUAL>, C<ITIMER_PROF>, or
214 C<ITIMER_REALPROF>. Note that which ones are available depends: true
215 UNIX platforms usually have the first three, but (for example) Win32
216 and Cygwin have only C<ITIMER_REAL>, and only Solaris seems to have
217 C<ITIMER_REALPROF> (which is used to profile multithreaded programs).
219 C<ITIMER_REAL> results in C<alarm()>-like behavior. Time is counted in
220 I<real time>; that is, wallclock time. C<SIGALRM> is delivered when
223 C<ITIMER_VIRTUAL> counts time in (process) I<virtual time>; that is,
224 only when the process is running. In multiprocessor/user/CPU systems
225 this may be more or less than real or wallclock time. (This time is
226 also known as the I<user time>.) C<SIGVTALRM> is delivered when the
229 C<ITIMER_PROF> counts time when either the process virtual time or when
230 the operating system is running on behalf of the process (such as I/O).
231 (This time is also known as the I<system time>.) (The sum of user
232 time and system time is known as the I<CPU time>.) C<SIGPROF> is
233 delivered when the timer expires. C<SIGPROF> can interrupt system calls.
235 The semantics of interval timers for multithreaded programs are
236 system-specific, and some systems may support additional interval
237 timers. See your C<setitimer()> documentation.
239 =item getitimer ( $which )
241 Return the remaining time in the interval timer specified by C<$which>.
243 In scalar context, the remaining time is returned.
245 In list context, both the remaining time and the interval are returned.
246 The interval is always what you put in using C<setitimer()>.
252 use Time::HiRes qw(usleep ualarm gettimeofday tv_interval);
254 $microseconds = 750_000;
255 usleep $microseconds;
257 # signal alarm in 2.5s & every .1s thereafter
258 ualarm 2_500_000, 100_000;
260 # get seconds and microseconds since the epoch
261 ($s, $usec) = gettimeofday;
263 # measure elapsed time
264 # (could also do by subtracting 2 gettimeofday return values)
265 $t0 = [gettimeofday];
266 # do bunch of stuff here
267 $t1 = [gettimeofday];
269 $t0_t1 = tv_interval $t0, $t1;
271 $elapsed = tv_interval ($t0, [gettimeofday]);
272 $elapsed = tv_interval ($t0); # equivalent code
275 # replacements for time, alarm and sleep that know about
279 $now_fractions = Time::HiRes::time;
280 Time::HiRes::sleep (2.5);
281 Time::HiRes::alarm (10.6666666);
283 use Time::HiRes qw ( time alarm sleep );
284 $now_fractions = time;
288 # Arm an interval timer to go off first at 10 seconds and
289 # after that every 2.5 seconds, in process virtual time
291 use Time::HiRes qw ( setitimer ITIMER_VIRTUAL time );
293 $SIG{VTALRM} = sub { print time, "\n" };
294 setitimer(ITIMER_VIRTUAL, 10, 2.5);
298 In addition to the perl API described above, a C API is available for
299 extension writers. The following C functions are available in the
303 --------------- ----------------------
304 Time::NVtime double (*)()
305 Time::U2time void (*)(UV ret[2])
307 Both functions return equivalent information (like C<gettimeofday>)
308 but with different representations. The names C<NVtime> and C<U2time>
309 were selected mainly because they are operating system independent.
310 (C<gettimeofday> is Unix-centric, though some platforms like VMS have
313 Here is an example of using C<NVtime> from C:
315 double (*myNVtime)();
316 SV **svp = hv_fetch(PL_modglobal, "Time::NVtime", 12, 0);
317 if (!svp) croak("Time::HiRes is required");
318 if (!SvIOK(*svp)) croak("Time::NVtime isn't a function pointer");
319 myNVtime = INT2PTR(double(*)(), SvIV(*svp));
320 printf("The current time is: %f\n", (*myNVtime)());
324 =head2 negative time not invented yet
326 You tried to use a negative time argument.
328 =head2 internal error: useconds < 0 (unsigned ... signed ...)
330 Something went horribly wrong-- the number of microseconds that cannot
331 become negative just became negative. Maybe your compiler is broken?
335 Notice that the core C<time()> maybe rounding rather than truncating.
336 What this means is that the core C<time()> may be reporting the time
337 as one second later than C<gettimeofday()> and C<Time::HiRes::time()>.
339 Adjusting the system clock (either manually or by services like ntp)
340 may cause problems, especially for long running programs that assume
341 a monotonously increasing time (note that all platforms do not adjust
342 time as gracefully as UNIX ntp does). For example in Win32 (and derived
343 platforms like Cygwin and MinGW) the Time::HiRes::time() may temporarily
344 drift off from the system clock (and the original time()) by up to 0.5
345 seconds. Time::HiRes will notice this eventually and recalibrate.
349 D. Wegscheid <wegscd@whirlpool.com>
350 R. Schertler <roderick@argon.org>
351 J. Hietaniemi <jhi@iki.fi>
352 G. Aas <gisle@aas.no>
354 =head1 COPYRIGHT AND LICENSE
356 Copyright (c) 1996-2002 Douglas E. Wegscheid. All rights reserved.
358 Copyright (c) 2002,2003,2004 Jarkko Hietaniemi. All rights reserved.
360 This program is free software; you can redistribute it and/or modify
361 it under the same terms as Perl itself.