[ViewVC] Diff of: cvs/libev/ev.3

Comparing libev/ev.3 (file contents):
Revision 1.100 by root, Tue Oct 29 12:13:37 2013 UTC vs.
Revision 1.109 by root, Fri Dec 21 07:03:02 2018 UTC

-.\" Automatically generated by Pod::Man 2.27 (Pod::Simple 3.28)
+.\" Automatically generated by Pod::Man 2.28 (Pod::Simple 3.29)
 .\"
 .\" Standard preamble:
 .\" ========================================================================
 .de Sp \" Vertical space (when we can't use .PP)
 .if t .sp .5v
 .\}
 .rm #[ #] #H #V #F C
 .\" ========================================================================
 .\"
 .IX Title "LIBEV 3"
-.TH LIBEV 3 "2013-10-29" "libev-4.15" "libev - high performance full featured event loop"
+.TH LIBEV 3 "2018-12-21" "libev-4.25" "libev - high performance full featured event loop"
 .\" For nroff, turn off justification.  Always turn off hyphenation; it makes
 .\" way too many mistakes in technical documents.
 .if n .ad l
 .nh
 .SH "NAME"
 make libev check for a fork in each iteration by enabling this flag.
 .Sp
 This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
 and thus this might slow down your event loop if you do a lot of loop
 iterations and little real work, but is usually not noticeable (on my
-GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
+GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn
-without a system call and thus \fIvery\fR fast, but my GNU/Linux system also has
+sequence without a system call and thus \fIvery\fR fast, but my GNU/Linux
-\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
+system also has \f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). (Update: glibc
+versions 2.25 apparently removed the \f(CW\*(C`getpid\*(C'\fR optimisation again).
 .Sp
 The big advantage of this flag is that you can forget about fork (and
-forget about forgetting to tell libev about forking) when you use this
+forget about forgetting to tell libev about forking, although you still
-flag.
+have to ignore \f(CW\*(C`SIGPIPE\*(C'\fR) when you use this flag.
 .Sp
 This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
 environment variable.
 .ie n .IP """EVFLAG_NOINOTIFY""" 4
 .el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4
 except in the rare occasion where you really need to free its resources.
 If you need dynamically allocated loops it is better to use \f(CW\*(C`ev_loop_new\*(C'\fR
 and \f(CW\*(C`ev_loop_destroy\*(C'\fR.
 .IP "ev_loop_fork (loop)" 4
 .IX Item "ev_loop_fork (loop)"
-This function sets a flag that causes subsequent \f(CW\*(C`ev_run\*(C'\fR iterations to
+This function sets a flag that causes subsequent \f(CW\*(C`ev_run\*(C'\fR iterations
-reinitialise the kernel state for backends that have one. Despite the
+to reinitialise the kernel state for backends that have one. Despite
-name, you can call it anytime, but it makes most sense after forking, in
+the name, you can call it anytime you are allowed to start or stop
-the child process. You \fImust\fR call it (or use \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR) in the
+watchers (except inside an \f(CW\*(C`ev_prepare\*(C'\fR callback), but it makes most
-child before resuming or calling \f(CW\*(C`ev_run\*(C'\fR.
+sense after forking, in the child process. You \fImust\fR call it (or use
+\&\f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR) in the child before resuming or calling \f(CW\*(C`ev_run\*(C'\fR.
+.Sp
+In addition, if you want to reuse a loop (via this function or
+\&\f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR), you \fIalso\fR have to ignore \f(CW\*(C`SIGPIPE\*(C'\fR.
 .Sp
 Again, you \fIhave\fR to call it on \fIany\fR loop that you want to re-use after
 a fork, \fIeven if you do not plan to use the loop in the parent\fR. This is
 because some kernel interfaces *cough* \fIkqueue\fR *cough* do funny things
 during fork.
 .PP
 The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR
 time. This is usually the right thing as this timestamp refers to the time
 of the event triggering whatever timeout you are modifying/starting. If
 you suspect event processing to be delayed and you \fIneed\fR to base the
-timeout on the current time, use something like this to adjust for this:
+timeout on the current time, use something like the following to adjust
+for it:
 .PP
 .Vb 1
-\&   ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.);
+\&   ev_timer_set (&timer, after + (ev_time () \- ev_now ()), 0.);
 .Ve
 .PP
 If the event loop is suspended for a long time, you can also force an
 update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update
-()\*(C'\fR.
+()\*(C'\fR, although that will push the event time of all outstanding events
+further into the future.
 .PP
 \fIThe special problem of unsynchronised clocks\fR
 .IX Subsection "The special problem of unsynchronised clocks"
 .PP
 Modern systems have a variety of clocks \- libev itself uses the normal
 .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
 .PD 0
 .IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
 .IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
 .PD
-Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR
+Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds (fractional and
-is \f(CW0.\fR, then it will automatically be stopped once the timeout is
+negative values are supported). If \f(CW\*(C`repeat\*(C'\fR is \f(CW0.\fR, then it will
-reached. If it is positive, then the timer will automatically be
+automatically be stopped once the timeout is reached. If it is positive,
-configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds later, again, and again,
+then the timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR
-until stopped manually.
+seconds later, again, and again, until stopped manually.
 .Sp
 The timer itself will do a best-effort at avoiding drift, that is, if
 you configure a timer to trigger every 10 seconds, then it will normally
 trigger at exactly 10 second intervals. If, however, your program cannot
 keep up with the timer (because it takes longer than those 10 seconds to
 Periodic watchers are also timers of a kind, but they are very versatile
 (and unfortunately a bit complex).
 .PP
 Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or
 relative time, the physical time that passes) but on wall clock time
-(absolute time, the thing you can read on your calender or clock). The
+(absolute time, the thing you can read on your calendar or clock). The
 difference is that wall clock time can run faster or slower than real
 time, and time jumps are not uncommon (e.g. when you adjust your
 wrist-watch).
 .PP
 You can tell a periodic watcher to trigger after some specific point
 \&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting
 it, as it uses a relative timeout).
 .PP
 \&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex
 timers, such as triggering an event on each \*(L"midnight, local time\*(R", or
-other complicated rules. This cannot be done with \f(CW\*(C`ev_timer\*(C'\fR watchers, as
+other complicated rules. This cannot easily be done with \f(CW\*(C`ev_timer\*(C'\fR
-those cannot react to time jumps.
+watchers, as those cannot react to time jumps.
 .PP
 As with timers, the callback is guaranteed to be invoked only when the
 point in time where it is supposed to trigger has passed. If multiple
 timers become ready during the same loop iteration then the ones with
 earlier time-out values are invoked before ones with later time-out values
 .Sp
 \&\s-1NOTE: \s0\fIThis callback must always return a time that is higher than or
 equal to the passed \f(CI\*(C`now\*(C'\fI value\fR.
 .Sp
 This can be used to create very complex timers, such as a timer that
-triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate the
+triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate
-next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How
+the next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for
-you do this is, again, up to you (but it is not trivial, which is the main
+this. Here is a (completely untested, no error checking) example on how to
-reason I omitted it as an example).
+do this:
+.Sp
+.Vb 1
+\&   #include <time.h>
+\&
+\&   static ev_tstamp
+\&   my_rescheduler (ev_periodic *w, ev_tstamp now)
+\&   {
+\&     time_t tnow = (time_t)now;
+\&     struct tm tm;
+\&     localtime_r (&tnow, &tm);
+\&
+\&     tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
+\&     ++tm.tm_mday; // midnight next day
+\&
+\&     return mktime (&tm);
+\&   }
+.Ve
+.Sp
+Note: this code might run into trouble on days that have more then two
+midnights (beginning and end).
 .RE
 .RS 4
 .RE
 .IP "ev_periodic_again (loop, ev_periodic *)" 4
 .IX Item "ev_periodic_again (loop, ev_periodic *)"
 only within the same loop, i.e. you can watch for \f(CW\*(C`SIGINT\*(C'\fR in your
 default loop and for \f(CW\*(C`SIGIO\*(C'\fR in another loop, but you cannot watch for
 \&\f(CW\*(C`SIGINT\*(C'\fR in both the default loop and another loop at the same time. At
 the moment, \f(CW\*(C`SIGCHLD\*(C'\fR is permanently tied to the default loop.
 .PP
-When the first watcher gets started will libev actually register something
+Only after the first watcher for a signal is started will libev actually
-with the kernel (thus it coexists with your own signal handlers as long as
+register something with the kernel. It thus coexists with your own signal
-you don't register any with libev for the same signal).
+handlers as long as you don't register any with libev for the same signal.
 .PP
 If possible and supported, libev will install its handlers with
 \&\f(CW\*(C`SA_RESTART\*(C'\fR (or equivalent) behaviour enabled, so system calls should
 not be unduly interrupted. If you have a problem with system calls getting
 interrupted by signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher
 .IX Subsection "ev_prepare and ev_check - customise your event loop!"
 Prepare and check watchers are often (but not always) used in pairs:
 prepare watchers get invoked before the process blocks and check watchers
 afterwards.
 .PP
-You \fImust not\fR call \f(CW\*(C`ev_run\*(C'\fR or similar functions that enter
+You \fImust not\fR call \f(CW\*(C`ev_run\*(C'\fR (or similar functions that enter the
-the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
+current event loop) or \f(CW\*(C`ev_loop_fork\*(C'\fR from either \f(CW\*(C`ev_prepare\*(C'\fR or
-watchers. Other loops than the current one are fine, however. The
+\&\f(CW\*(C`ev_check\*(C'\fR watchers. Other loops than the current one are fine,
-rationale behind this is that you do not need to check for recursion in
+however. The rationale behind this is that you do not need to check
-those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
+for recursion in those watchers, i.e. the sequence will always be
-\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
+\&\f(CW\*(C`ev_prepare\*(C'\fR, blocking, \f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each
-called in pairs bracketing the blocking call.
+kind they will always be called in pairs bracketing the blocking call.
 .PP
 Their main purpose is to integrate other event mechanisms into libev and
 their use is somewhat advanced. They could be used, for example, to track
 variable changes, implement your own watchers, integrate net-snmp or a
 coroutine library and lots more. They are also occasionally useful if
 .PP
 .Vb 3
 \&   struct ev_loop *loop_hi = ev_default_init (0);
 \&   struct ev_loop *loop_lo = 0;
 \&   ev_embed embed;
 \&
 \&   // see if there is a chance of getting one that works
 \&   // (remember that a flags value of 0 means autodetection)
 \&   loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
 \&     ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
 \&     : 0;
 .PP
 .Vb 3
 \&   struct ev_loop *loop = ev_default_init (0);
 \&   struct ev_loop *loop_socket = 0;
 \&   ev_embed embed;
 \&
 \&   if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
 \&     if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
 \&       {
 \&         ev_embed_init (&embed, 0, loop_socket);
 \&         ev_embed_start (loop, &embed);
 of course.
 .PP
 \fIThe special problem of life after fork \- how is it possible?\fR
 .IX Subsection "The special problem of life after fork - how is it possible?"
 .PP
-Most uses of \f(CW\*(C`fork()\*(C'\fR consist of forking, then some simple calls to set
+Most uses of \f(CW\*(C`fork ()\*(C'\fR consist of forking, then some simple calls to set
 up/change the process environment, followed by a call to \f(CW\*(C`exec()\*(C'\fR. This
 sequence should be handled by libev without any problems.
 .PP
 This changes when the application actually wants to do event handling
 in the child, or both parent in child, in effect \*(L"continuing\*(R" after the
 is a time window between the event loop checking and resetting the async
 notification, and the callback being invoked.
 .SH "OTHER FUNCTIONS"
 .IX Header "OTHER FUNCTIONS"
 There are some other functions of possible interest. Described. Here. Now.
-.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
+.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)" 4
-.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
+.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)"
 This function combines a simple timer and an I/O watcher, calls your
 callback on whichever event happens first and automatically stops both
 watchers. This is useful if you want to wait for a single event on an fd
 or timeout without having to allocate/configure/start/stop/free one or
 more watchers yourself.
 files, \fImy_ev.h\fR and \fImy_ev.c\fR that include the respective libev files:
 .PP
 .Vb 4
 \&   // my_ev.h
 \&   #define EV_CB_DECLARE(type)   struct my_coro *cb;
-\&   #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb);
+\&   #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb)
 \&   #include "../libev/ev.h"
 \&
 \&   // my_ev.c
 \&   #define EV_H "my_ev.h"
 \&   #include "../libev/ev.c"
 The normal C \s-1API\s0 should work fine when used from \*(C+: both ev.h and the
 libev sources can be compiled as \*(C+. Therefore, code that uses the C \s-1API\s0
 will work fine.
 .PP
 Proper exception specifications might have to be added to callbacks passed
-to libev: exceptions may be thrown only from watcher callbacks, all
+to libev: exceptions may be thrown only from watcher callbacks, all other
-other callbacks (allocator, syserr, loop acquire/release and periodic
+callbacks (allocator, syserr, loop acquire/release and periodic reschedule
-reschedule callbacks) must not throw exceptions, and might need a \f(CW\*(C`throw
+callbacks) must not throw exceptions, and might need a \f(CW\*(C`noexcept\*(C'\fR
-()\*(C'\fR specification. If you have code that needs to be compiled as both C
+specification. If you have code that needs to be compiled as both C and
-and \*(C+ you can use the \f(CW\*(C`EV_THROW\*(C'\fR macro for this:
+\&\*(C+ you can use the \f(CW\*(C`EV_NOEXCEPT\*(C'\fR macro for this:
 .PP
 .Vb 6
 \&   static void
-\&   fatal_error (const char *msg) EV_THROW
+\&   fatal_error (const char *msg) EV_NOEXCEPT
 \&   {
 \&     perror (msg);
 \&     abort ();
 \&   }
 \&
 \&     void operator() (ev::io &w, int revents)
 \&     {
 \&       ...
 \&     }
 \&   }
 \&
 \&   myfunctor f;
 \&
 \&   ev::io w;
 \&   w.set (&f);
 .Ve
 \&   ev_vars.h
 \&   ev_wrap.h
 \&
 \&   ev_win32.c      required on win32 platforms only
 \&
-\&   ev_select.c     only when select backend is enabled (which is enabled by default)
+\&   ev_select.c     only when select backend is enabled
-\&   ev_poll.c       only when poll backend is enabled (disabled by default)
+\&   ev_poll.c       only when poll backend is enabled
-\&   ev_epoll.c      only when the epoll backend is enabled (disabled by default)
+\&   ev_epoll.c      only when the epoll backend is enabled
-\&   ev_kqueue.c     only when the kqueue backend is enabled (disabled by default)
+\&   ev_kqueue.c     only when the kqueue backend is enabled
-\&   ev_port.c       only when the solaris port backend is enabled (disabled by default)
+\&   ev_port.c       only when the solaris port backend is enabled
 .Ve
 .PP
 \&\fIev.c\fR includes the backend files directly when enabled, so you only need
 to compile this single file.
 .PP
 Libev assumes not only that all watcher pointers have the same internal
 structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO C\s0 for example), but it also
 assumes that the same (machine) code can be used to call any watcher
 callback: The watcher callbacks have different type signatures, but libev
 calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally.
+.IP "null pointers and integer zero are represented by 0 bytes" 4
+.IX Item "null pointers and integer zero are represented by 0 bytes"
+Libev uses \f(CW\*(C`memset\*(C'\fR to initialise structs and arrays to \f(CW0\fR bytes, and
+relies on this setting pointers and integers to null.
 .IP "pointer accesses must be thread-atomic" 4
 .IX Item "pointer accesses must be thread-atomic"
 Accessing a pointer value must be atomic, it must both be readable and
 writable in one piece \- this is the case on all current architectures.
 .ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing libev/ev.3 (file contents): Revision 1.100 by root, Tue Oct 29 12:13:37 2013 UTC vs. Revision 1.109 by root, Fri Dec 21 07:03:02 2018 UTC

Diff Legend

Comparing libev/ev.3 (file contents):
Revision 1.100 by root, Tue Oct 29 12:13:37 2013 UTC vs.
Revision 1.109 by root, Fri Dec 21 07:03:02 2018 UTC