*** empty log message ***

[software/libev.git] / ev.pod

diff --git a/ev.pod b/ev.pod
index 538b9f82ddd6c235cd8716d8e7ae556cbfa1b2b9..ba1eec4766f7789e80b55f1ebd667a5ee542f9e2 100644 (file)
--- a/ev.pod
+++ b/ev.pod
@@ -100,7 +100,9 @@ Libev represents time as a single floating point number, representing the
 the beginning of 1970, details are complicated, don't ask). This type is
 called C<ev_tstamp>, which is what you should use too. It usually aliases
 to the C<double> type in C, and when you need to do any calculations on
 the beginning of 1970, details are complicated, don't ask). This type is
 called C<ev_tstamp>, which is what you should use too. It usually aliases
 to the C<double> type in C, and when you need to do any calculations on

-it, you should treat it as such.
+it, you should treat it as some floatingpoint value. Unlike the name
+component C<stamp> might indicate, it is also used for time differences
+throughout libev.

 
 =head1 GLOBAL FUNCTIONS
 
 
 =head1 GLOBAL FUNCTIONS
 


@@ -119,14 +121,17 @@ you actually want to know.
 
 =item int ev_version_minor ()
 
 
 =item int ev_version_minor ()
 

-You can find out the major and minor version numbers of the library
+You can find out the major and minor ABI version numbers of the library

 you linked against by calling the functions C<ev_version_major> and
 C<ev_version_minor>. If you want, you can compare against the global
 symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
 version of the library your program was compiled against.
 
 you linked against by calling the functions C<ev_version_major> and
 C<ev_version_minor>. If you want, you can compare against the global
 symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
 version of the library your program was compiled against.
 

+These version numbers refer to the ABI version of the library, not the
+release version.
+

 Usually, it's a good idea to terminate if the major versions mismatch,
 Usually, it's a good idea to terminate if the major versions mismatch,

-as this indicates an incompatible change.  Minor versions are usually
+as this indicates an incompatible change. Minor versions are usually

 compatible to older versions, so a larger minor version alone is usually
 not a problem.
 
 compatible to older versions, so a larger minor version alone is usually
 not a problem.
 


@@ -401,9 +406,18 @@ etc.). None of the active event watchers will be stopped in the normal
 sense, so e.g. C<ev_is_active> might still return true. It is your
 responsibility to either stop all watchers cleanly yoursef I<before>
 calling this function, or cope with the fact afterwards (which is usually
 sense, so e.g. C<ev_is_active> might still return true. It is your
 responsibility to either stop all watchers cleanly yoursef I<before>
 calling this function, or cope with the fact afterwards (which is usually

-the easiest thing, youc na just ignore the watchers and/or C<free ()> them
+the easiest thing, you can just ignore the watchers and/or C<free ()> them

 for example).
 
 for example).
 

+Not that certain global state, such as signal state, will not be freed by
+this function, and related watchers (such as signal and child watchers)
+would need to be stopped manually.
+
+In general it is not advisable to call this function except in the
+rare occasion where you really need to free e.g. the signal handling
+pipe fds. If you need dynamically allocated loops it is better to use
+C<ev_loop_new> and C<ev_loop_destroy>).
+

 =item ev_loop_destroy (loop)
 
 Like C<ev_default_destroy>, but destroys an event loop created by an
 =item ev_loop_destroy (loop)
 
 Like C<ev_default_destroy>, but destroys an event loop created by an


@@ -488,8 +502,9 @@ usually a better approach for this kind of thing.
 
 Here are the gory details of what C<ev_loop> does:
 
 
 Here are the gory details of what C<ev_loop> does:
 

+   - Before the first iteration, call any pending watchers.

    * If there are no active watchers (reference count is zero), return.
    * If there are no active watchers (reference count is zero), return.

-   - Queue prepare watchers and then call all outstanding watchers.
+   - Queue all prepare watchers and then call all outstanding watchers.

    - If we have been forked, recreate the kernel state.
    - Update the kernel state with all outstanding changes.
    - Update the "event loop time".
    - If we have been forked, recreate the kernel state.
    - Update the kernel state with all outstanding changes.
    - Update the "event loop time".


@@ -909,6 +924,30 @@ whether a file descriptor is really ready with a known-to-be good interface
 such as poll (fortunately in our Xlib example, Xlib already does this on
 its own, so its quite safe to use).
 
 such as poll (fortunately in our Xlib example, Xlib already does this on
 its own, so its quite safe to use).
 

+=head3 The special problem of disappearing file descriptors
+
+Some backends (e.g kqueue, epoll) need to be told about closing a file
+descriptor (either by calling C<close> explicitly or by any other means,
+such as C<dup>). The reason is that you register interest in some file
+descriptor, but when it goes away, the operating system will silently drop
+this interest. If another file descriptor with the same number then is
+registered with libev, there is no efficient way to see that this is, in
+fact, a different file descriptor.
+
+To avoid having to explicitly tell libev about such cases, libev follows
+the following policy:  Each time C<ev_io_set> is being called, libev
+will assume that this is potentially a new file descriptor, otherwise
+it is assumed that the file descriptor stays the same. That means that
+you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
+descriptor even if the file descriptor number itself did not change.
+
+This is how one would do it normally anyway, the important point is that
+the libev application should not optimise around libev but should leave
+optimisations to libev.
+
+
+=head3 Watcher-Specific Functions
+

 =over 4
 
 =item ev_io_init (ev_io *, callback, int fd, int events)
 =over 4
 
 =item ev_io_init (ev_io *, callback, int fd, int events)


@@ -971,6 +1010,8 @@ The callback is guarenteed to be invoked only when its timeout has passed,
 but if multiple timers become ready during the same loop iteration then
 order of execution is undefined.
 
 but if multiple timers become ready during the same loop iteration then
 order of execution is undefined.
 

+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
 =over 4
 
 =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)


@@ -1075,16 +1116,18 @@ to trigger "at" some specific point in time. For example, if you tell a
 periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
 + 10.>) and then reset your system clock to the last year, then it will
 take a year to trigger the event (unlike an C<ev_timer>, which would trigger
 periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
 + 10.>) and then reset your system clock to the last year, then it will
 take a year to trigger the event (unlike an C<ev_timer>, which would trigger

-roughly 10 seconds later and of course not if you reset your system time
-again).
+roughly 10 seconds later).

 
 They can also be used to implement vastly more complex timers, such as
 
 They can also be used to implement vastly more complex timers, such as

-triggering an event on eahc midnight, local time.
+triggering an event on each midnight, local time or other, complicated,
+rules.

 
 As with timers, the callback is guarenteed to be invoked only when the
 time (C<at>) has been passed, but if multiple periodic timers become ready
 during the same loop iteration then order of execution is undefined.
 
 
 As with timers, the callback is guarenteed to be invoked only when the
 time (C<at>) has been passed, but if multiple periodic timers become ready
 during the same loop iteration then order of execution is undefined.
 

+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
 =over 4
 
 =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)


@@ -1096,18 +1139,18 @@ operation, and we will explain them from simplest to complex:
 
 =over 4
 
 
 =over 4
 

-=item * absolute timer (interval = reschedule_cb = 0)
+=item * absolute timer (at = time, interval = reschedule_cb = 0)

 
 In this configuration the watcher triggers an event at the wallclock time
 C<at> and doesn't repeat. It will not adjust when a time jump occurs,
 that is, if it is to be run at January 1st 2011 then it will run when the
 system time reaches or surpasses this time.
 
 
 In this configuration the watcher triggers an event at the wallclock time
 C<at> and doesn't repeat. It will not adjust when a time jump occurs,
 that is, if it is to be run at January 1st 2011 then it will run when the
 system time reaches or surpasses this time.
 

-=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)
+=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)

 
 In this mode the watcher will always be scheduled to time out at the next
 
 In this mode the watcher will always be scheduled to time out at the next

-C<at + N * interval> time (for some integer N) and then repeat, regardless
-of any time jumps.
+C<at + N * interval> time (for some integer N, which can also be negative)
+and then repeat, regardless of any time jumps.

 
 This can be used to create timers that do not drift with respect to system
 time:
 
 This can be used to create timers that do not drift with respect to system
 time:


@@ -1123,7 +1166,11 @@ Another way to think about it (for the mathematically inclined) is that
 C<ev_periodic> will try to run the callback in this mode at the next possible
 time where C<time = at (mod interval)>, regardless of any time jumps.
 
 C<ev_periodic> will try to run the callback in this mode at the next possible
 time where C<time = at (mod interval)>, regardless of any time jumps.
 

-=item * manual reschedule mode (reschedule_cb = callback)
+For numerical stability it is preferable that the C<at> value is near
+C<ev_now ()> (the current time), but there is no range requirement for
+this value.
+
+=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)

 
 In this mode the values for C<interval> and C<at> are both being
 ignored. Instead, each time the periodic watcher gets scheduled, the
 
 In this mode the values for C<interval> and C<at> are both being
 ignored. Instead, each time the periodic watcher gets scheduled, the


@@ -1133,7 +1180,7 @@ current time as second argument.
 NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
 ever, or make any event loop modifications>. If you need to stop it,
 return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
 NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
 ever, or make any event loop modifications>. If you need to stop it,
 return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by

-starting a prepare watcher).
+starting an C<ev_prepare> watcher, which is legal).

 
 Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
 ev_tstamp now)>, e.g.:
 
 Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
 ev_tstamp now)>, e.g.:


@@ -1166,6 +1213,14 @@ when you changed some parameters or the reschedule callback would return
 a different time than the last time it was called (e.g. in a crond like
 program when the crontabs have changed).
 
 a different time than the last time it was called (e.g. in a crond like
 program when the crontabs have changed).
 

+=item ev_tstamp offset [read-write]
+
+When repeating, this contains the offset value, otherwise this is the
+absolute point in time (the C<at> value passed to C<ev_periodic_set>).
+
+Can be modified any time, but changes only take effect when the periodic
+timer fires or C<ev_periodic_again> is being called.
+

 =item ev_tstamp interval [read-write]
 
 The current interval value. Can be modified any time, but changes only
 =item ev_tstamp interval [read-write]
 
 The current interval value. Can be modified any time, but changes only


@@ -1178,6 +1233,11 @@ The current reschedule callback, or C<0>, if this functionality is
 switched off. Can be changed any time, but changes only take effect when
 the periodic timer fires or C<ev_periodic_again> is being called.
 
 switched off. Can be changed any time, but changes only take effect when
 the periodic timer fires or C<ev_periodic_again> is being called.
 

+=item ev_tstamp at [read-only]
+
+When active, contains the absolute time that the watcher is supposed to
+trigger next.
+

 =back
 
 Example: Call a callback every hour, or, more precisely, whenever the
 =back
 
 Example: Call a callback every hour, or, more precisely, whenever the


@@ -1228,6 +1288,8 @@ as you don't register any with libev). Similarly, when the last signal
 watcher for a signal is stopped libev will reset the signal handler to
 SIG_DFL (regardless of what it was set to before).
 
 watcher for a signal is stopped libev will reset the signal handler to
 SIG_DFL (regardless of what it was set to before).
 

+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_signal_init (ev_signal *, callback, int signum)
 =over 4
 
 =item ev_signal_init (ev_signal *, callback, int signum)


@@ -1249,6 +1311,8 @@ The signal the watcher watches out for.
 Child watchers trigger when your process receives a SIGCHLD in response to
 some child status changes (most typically when a child of yours dies).
 
 Child watchers trigger when your process receives a SIGCHLD in response to
 some child status changes (most typically when a child of yours dies).
 

+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_child_init (ev_child *, callback, int pid)
 =over 4
 
 =item ev_child_init (ev_child *, callback, int pid)


@@ -1326,6 +1390,8 @@ to fall back to regular polling again even with inotify, but changes are
 usually detected immediately, and if the file exists there will be no
 polling.
 
 usually detected immediately, and if the file exists there will be no
 polling.
 

+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
 =over 4
 
 =item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)


@@ -1417,6 +1483,8 @@ effect on its own sometimes), idle watchers are a good place to do
 "pseudo-background processing", or delay processing stuff to after the
 event loop has handled all outstanding events.
 
 "pseudo-background processing", or delay processing stuff to after the
 event loop has handled all outstanding events.
 

+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_idle_init (ev_signal *, callback)
 =over 4
 
 =item ev_idle_init (ev_signal *, callback)


@@ -1483,6 +1551,18 @@ of lower priority, but only once, using idle watchers to keep the event
 loop from blocking if lower-priority coroutines are active, thus mapping
 low-priority coroutines to idle/background tasks).
 
 loop from blocking if lower-priority coroutines are active, thus mapping
 low-priority coroutines to idle/background tasks).
 

+It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
+priority, to ensure that they are being run before any other watchers
+after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
+too) should not activate ("feed") events into libev. While libev fully
+supports this, they will be called before other C<ev_check> watchers did
+their job. As C<ev_check> watchers are often used to embed other event
+loops those other event loops might be in an unusable state until their
+C<ev_check> watcher ran (always remind yourself to coexist peacefully with
+others).
+
+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_prepare_init (ev_prepare *, callback)
 =over 4
 
 =item ev_prepare_init (ev_prepare *, callback)


@@ -1693,6 +1773,8 @@ create it, and if that fails, use the normal loop for everything:
   else
     loop_lo = loop_hi;
 
   else
     loop_lo = loop_hi;
 

+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
 =over 4
 
 =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)


@@ -1728,6 +1810,8 @@ and only in the child after the fork. If whoever good citizen calling
 C<ev_default_fork> cheats and calls it in the wrong process, the fork
 handlers will be invoked, too, of course.
 
 C<ev_default_fork> cheats and calls it in the wrong process, the fork
 handlers will be invoked, too, of course.
 

+=head3 Watcher-Specific Functions and Data Members
+

 =over 4
 
 =item ev_fork_init (ev_signal *, callback)
 =over 4
 
 =item ev_fork_init (ev_signal *, callback)


@@ -1953,16 +2037,16 @@ constructor already stores the event loop.
 
 Stops the watcher if it is active. Again, no C<loop> argument.
 
 
 Stops the watcher if it is active. Again, no C<loop> argument.
 

-=item w->again ()       C<ev::timer>, C<ev::periodic> only
+=item w->again () (C<ev::timer>, C<ev::periodic> only)

 
 For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
 C<ev_TYPE_again> function.
 
 
 For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
 C<ev_TYPE_again> function.
 

-=item w->sweep ()       C<ev::embed> only
+=item w->sweep () (C<ev::embed> only)

 
 Invokes C<ev_embed_sweep>.
 
 
 Invokes C<ev_embed_sweep>.
 

-=item w->update ()      C<ev::stat> only
+=item w->update () (C<ev::stat> only)

 
 Invokes C<ev_stat_stat>.
 
 
 Invokes C<ev_stat_stat>.
 


@@ -1992,9 +2076,9 @@ the constructor.
 
 =head1 MACRO MAGIC
 
 
 =head1 MACRO MAGIC
 

-Libev can be compiled with a variety of options, the most fundemantal is
-C<EV_MULTIPLICITY>. This option determines whether (most) functions and
-callbacks have an initial C<struct ev_loop *> argument.
+Libev can be compiled with a variety of options, the most fundamantal
+of which is C<EV_MULTIPLICITY>. This option determines whether (most)
+functions and callbacks have an initial C<struct ev_loop *> argument.

 
 To make it easier to write programs that cope with either variant, the
 following macros are defined:
 
 To make it easier to write programs that cope with either variant, the
 following macros are defined: