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 C<usleep>,
87 C<ualarm>, C<gettimeofday>, and C<setitimer>/C<getitimer> system calls, in other
88 words, high resolution time and timers. See the L</EXAMPLES> section below
89 and the test scripts for usage; see your system documentation for the
90 description of the underlying C<nanosleep> or C<usleep>, C<ualarm>,
91 C<gettimeofday>, and C<setitimer>/C<getitimer> calls.
93 If your system lacks C<gettimeofday()> or an emulation of it you don't
94 get C<gettimeofday()> or the one-argument form of C<tv_interval()>. If your system lacks all of
95 C<nanosleep()>, C<usleep()>, and C<select()>, you don't get
96 C<Time::HiRes::usleep()> or C<Time::HiRes::sleep()>. If your system lacks both
97 C<ualarm()> and C<setitimer()> you don't get
98 C<Time::HiRes::ualarm()> or C<Time::HiRes::alarm()>.
100 If you try to import an unimplemented function in the C<use> statement
101 it will fail at compile time.
103 If your subsecond sleeping is implemented with C<nanosleep()> instead of
104 C<usleep()>, you can mix subsecond sleeping with signals since
105 C<nanosleep()> does not use signals. This, however is unportable, and you
106 should first check for the truth value of C<&Time::HiRes::d_nanosleep> to
107 see whether you have nanosleep, and then carefully read your
108 C<nanosleep()> C API documentation for any peculiarities. (There is no
109 separate interface to call C<nanosleep()>; just use C<Time::HiRes::sleep()>
110 or C<Time::HiRes::usleep()> with small enough values.)
112 Unless using C<nanosleep> for mixing sleeping with signals, give
113 some thought to whether Perl is the tool you should be using for work
114 requiring nanosecond accuracies.
116 The following functions can be imported from this module.
117 No functions are exported by default.
121 =item gettimeofday ()
123 In array context returns a two-element array with the seconds and
124 microseconds since the epoch. In scalar context returns floating
125 seconds like C<Time::HiRes::time()> (see below).
127 =item usleep ( $useconds )
129 Sleeps for the number of microseconds specified. Returns the number
130 of microseconds actually slept. Can sleep for more than one second,
131 unlike the C<usleep> system call. See also C<Time::HiRes::sleep()> below.
133 =item ualarm ( $useconds [, $interval_useconds ] )
135 Issues a C<ualarm> call; the C<$interval_useconds> is optional and
136 will be zero if unspecified, resulting in C<alarm>-like behaviour.
140 tv_interval ( $ref_to_gettimeofday [, $ref_to_later_gettimeofday] )
142 Returns the floating seconds between the two times, which should have
143 been returned by C<gettimeofday()>. If the second argument is omitted,
144 then the current time is used.
148 Returns a floating seconds since the epoch. This function can be
149 imported, resulting in a nice drop-in replacement for the C<time>
150 provided with core Perl; see the L</EXAMPLES> below.
152 B<NOTE 1>: This higher resolution timer can return values either less
153 or more than the core C<time()>, depending on whether your platform
154 rounds the higher resolution timer values up, down, or to the nearest second
155 to get the core C<time()>, but naturally the difference should be never
156 more than half a second.
158 B<NOTE 2>: Since Sunday, September 9th, 2001 at 01:46:40 AM GMT, when
159 the C<time()> seconds since epoch rolled over to 1_000_000_000, the
160 default floating point format of Perl and the seconds since epoch have
161 conspired to produce an apparent bug: if you print the value of
162 C<Time::HiRes::time()> you seem to be getting only five decimals, not six
163 as promised (microseconds). Not to worry, the microseconds are there
164 (assuming your platform supports such granularity in first place).
165 What is going on is that the default floating point format of Perl
166 only outputs 15 digits. In this case that means ten digits before the
167 decimal separator and five after. To see the microseconds you can use
168 either C<printf>/C<sprintf> with C<"%.6f">, or the C<gettimeofday()> function in
169 list context, which will give you the seconds and microseconds as two
172 =item sleep ( $floating_seconds )
174 Sleeps for the specified amount of seconds. Returns the number of
175 seconds actually slept (a floating point value). This function can be
176 imported, resulting in a nice drop-in replacement for the C<sleep>
177 provided with perl, see the L</EXAMPLES> below.
179 =item alarm ( $floating_seconds [, $interval_floating_seconds ] )
181 The C<SIGALRM> signal is sent after the specified number of seconds.
182 Implemented using C<ualarm()>. The C<$interval_floating_seconds> argument
183 is optional and will be zero if unspecified, resulting in C<alarm()>-like
184 behaviour. This function can be imported, resulting in a nice drop-in
185 replacement for the C<alarm> provided with perl, see the L</EXAMPLES> below.
187 B<NOTE 1>: With some operating system and Perl release combinations
188 C<SIGALRM> restarts C<select()>, instead of interuping it.
189 This means that an C<alarm()> followed by a C<select()>
190 may together take the sum of the times specified for the the
191 C<alarm()> and the C<select()>, not just the time of the C<alarm()>.
193 =item setitimer ( $which, $floating_seconds [, $interval_floating_seconds ] )
195 Start up an interval timer: after a certain time, a signal arrives,
196 and more signals may keep arriving at certain intervals. To disable a
197 timer, use C<$floating_seconds> of zero. If the C<$interval_floating_seconds>
198 is set to zero (or unspecified), the timer is disabled B<after> the
199 next delivered signal.
201 Use of interval timers may interfere with C<alarm()>, C<sleep()>,
202 and C<usleep()>. In standard-speak the "interaction is unspecified",
203 which means that I<anything> may happen: it may work, it may not.
205 In scalar context, the remaining time in the timer is returned.
207 In list context, both the remaining time and the interval are returned.
209 There are usually three or four interval timers available: the C<$which>
210 can be C<ITIMER_REAL>, C<ITIMER_VIRTUAL>, C<ITIMER_PROF>, or C<ITIMER_REALPROF>.
211 Note that which ones are available depends: true UNIX platforms usually
212 have the first three, but (for example) Win32 and Cygwin have only
213 C<ITIMER_REAL>, and only Solaris seems to have C<ITIMER_REALPROF> (which is
214 used to profile multithreaded programs).
216 C<ITIMER_REAL> results in C<alarm()>-like behavior. Time is counted in
217 I<real time>; that is, wallclock time. C<SIGALRM> is delivered when
220 C<ITIMER_VIRTUAL> counts time in (process) I<virtual time>; that is, only
221 when the process is running. In multiprocessor/user/CPU systems this
222 may be more or less than real or wallclock time. (This time is also
223 known as the I<user time>.) C<SIGVTALRM> is delivered when the timer expires.
225 C<ITIMER_PROF> counts time when either the process virtual time or when
226 the operating system is running on behalf of the process (such as I/O).
227 (This time is also known as the I<system time>.) (The sum of user
228 time and system time is known as the I<CPU time>.) C<SIGPROF> is
229 delivered when the timer expires. C<SIGPROF> can interrupt system calls.
231 The semantics of interval timers for multithreaded programs are
232 system-specific, and some systems may support additional interval
233 timers. See your C<setitimer()> documentation.
235 =item getitimer ( $which )
237 Return the remaining time in the interval timer specified by C<$which>.
239 In scalar context, the remaining time is returned.
241 In list context, both the remaining time and the interval are returned.
242 The interval is always what you put in using C<setitimer()>.
248 use Time::HiRes qw(usleep ualarm gettimeofday tv_interval);
250 $microseconds = 750_000;
251 usleep $microseconds;
253 # signal alarm in 2.5s & every .1s thereafter
254 ualarm 2_500_000, 100_000;
256 # get seconds and microseconds since the epoch
257 ($s, $usec) = gettimeofday;
259 # measure elapsed time
260 # (could also do by subtracting 2 gettimeofday return values)
261 $t0 = [gettimeofday];
262 # do bunch of stuff here
263 $t1 = [gettimeofday];
265 $t0_t1 = tv_interval $t0, $t1;
267 $elapsed = tv_interval ($t0, [gettimeofday]);
268 $elapsed = tv_interval ($t0); # equivalent code
271 # replacements for time, alarm and sleep that know about
275 $now_fractions = Time::HiRes::time;
276 Time::HiRes::sleep (2.5);
277 Time::HiRes::alarm (10.6666666);
279 use Time::HiRes qw ( time alarm sleep );
280 $now_fractions = time;
284 # Arm an interval timer to go off first at 10 seconds and
285 # after that every 2.5 seconds, in process virtual time
287 use Time::HiRes qw ( setitimer ITIMER_VIRTUAL time );
289 $SIG{VTALRM} = sub { print time, "\n" };
290 setitimer(ITIMER_VIRTUAL, 10, 2.5);
294 In addition to the perl API described above, a C API is available for
295 extension writers. The following C functions are available in the
299 --------------- ----------------------
300 Time::NVtime double (*)()
301 Time::U2time void (*)(UV ret[2])
303 Both functions return equivalent information (like C<gettimeofday>)
304 but with different representations. The names C<NVtime> and C<U2time>
305 were selected mainly because they are operating system independent.
306 (C<gettimeofday> is Unix-centric, though some platforms like VMS have
309 Here is an example of using C<NVtime> from C:
311 double (*myNVtime)();
312 SV **svp = hv_fetch(PL_modglobal, "Time::NVtime", 12, 0);
313 if (!svp) croak("Time::HiRes is required");
314 if (!SvIOK(*svp)) croak("Time::NVtime isn't a function pointer");
315 myNVtime = INT2PTR(double(*)(), SvIV(*svp));
316 printf("The current time is: %f\n", (*myNVtime)());
320 =head2 negative time not invented yet
322 You tried to use a negative time argument.
324 =head2 internal error: useconds < 0 (unsigned ... signed ...)
326 Something went horribly wrong-- the number of microseconds that cannot
327 become negative just became negative. Maybe your compiler is broken?
331 Notice that the core C<time()> maybe rounding rather than truncating.
332 What this means is that the core C<time()> may be reporting the time
333 as one second later than C<gettimeofday()> and C<Time::HiRes::time()>.
335 Adjusting the system clock (either manually or by services like ntp)
336 may cause problems, especially for long running programs that assume
337 a monotonously increasing time (note that all platforms do not adjust
338 time as gracefully as UNIX ntp does). For example in Win32 (and derived
339 platforms like Cygwin and MinGW) the Time::HiRes::time() may temporarily
340 drift off from the system clock (and the original time()) by up to 0.5
341 seconds. Time::HiRes will notice this eventually and recalibrate.
345 D. Wegscheid <wegscd@whirlpool.com>
346 R. Schertler <roderick@argon.org>
347 J. Hietaniemi <jhi@iki.fi>
348 G. Aas <gisle@aas.no>
350 =head1 COPYRIGHT AND LICENSE
352 Copyright (c) 1996-2002 Douglas E. Wegscheid. All rights reserved.
354 Copyright (c) 2002,2003,2004 Jarkko Hietaniemi. All rights reserved.
356 This program is free software; you can redistribute it and/or modify
357 it under the same terms as Perl itself.