X-Git-Url: https://git.llucax.com/software/libev.git/blobdiff_plain/09c28a9820828432b5ced0a8f2b05c56213690fc..ecc32f357000f3122b62992d755b4ce8156ab168:/ev.html diff --git a/ev.html b/ev.html index 1dcdd21..f63538f 100644 --- a/ev.html +++ b/ev.html @@ -6,7 +6,7 @@ - + @@ -187,13 +187,15 @@ you actually want to know.

int ev_version_major ()
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 ev_version_major and ev_version_minor. If you want, you can compare against the global symbols EV_VERSION_MAJOR and 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, -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.

Example: Make sure we haven't accidentally been linked against the wrong @@ -531,8 +533,9 @@ external event in conjunction with something not expressible using other libev watchers. However, a pair of ev_prepare/ev_check watchers is usually a better approach for this kind of thing.

Here are the gory details of what ev_loop does:

-
   * If there are no active watchers (reference count is zero), return.
-   - Queue prepare watchers and then call all outstanding watchers.
+
   - Before the first iteration, call any pending watchers.
+   * If there are no active watchers (reference count is zero), return.
+   - 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".
@@ -1098,10 +1101,10 @@ to trigger "at" some specific point in time. For example, if you tell
 periodic watcher to trigger in 10 seconds (by specifiying e.g. 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 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
-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 (at) has been passed, but if multiple periodic timers become ready
 during the same loop iteration then order of execution is undefined.

@@ -1113,18 +1116,18 @@ during the same loop iteration then order of execution is undefined.

 operation, and we will explain them from simplest to complex:

 		

 			

-				
* absolute timer (interval = reschedule_cb = 0)

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

 				

 					
In this configuration the watcher triggers an event at the wallclock time
 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.

 				

-				
* non-repeating interval timer (interval > 0, reschedule_cb = 0)

+				
* 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
-at + N * interval time (for some integer N) and then repeat, regardless
-of any time jumps.

+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:

 
   ev_periodic_set (&periodic, 0., 3600., 0);
@@ -1137,8 +1140,11 @@ by 3600.

 					
Another way to think about it (for the mathematically inclined) is that
 ev_periodic will try to run the callback in this mode at the next possible
 time where time = at (mod interval), regardless of any time jumps.

+					
For numerical stability it is preferable that the at value is near
+ev_now () (the current time), but there is no range requirement for
+this value.

 				

-				
* manual reschedule mode (reschedule_cb = callback)

+				
* manual reschedule mode (at and interval ignored, reschedule_cb = callback)

 				

 					
In this mode the values for interval and at are both being
 ignored. Instead, each time the periodic watcher gets scheduled, the
@@ -1147,7 +1153,7 @@ current time as second argument.

 					
NOTE: This callback MUST NOT stop or destroy any periodic watcher,
 ever, or make any event loop modifications. If you need to stop it,
 return now + 1e30 (or so, fudge fudge) and stop it afterwards (e.g. by
-starting a prepare watcher).

+starting an ev_prepare watcher, which is legal).

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

 
   static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
@@ -1177,6 +1183,13 @@ reason I omitted it as an example).

 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).

+	

+	
ev_tstamp offset [read-write]

+	

+		
When repeating, this contains the offset value, otherwise this is the
+absolute point in time (the at value passed to ev_periodic_set).

+		
Can be modified any time, but changes only take effect when the periodic
+timer fires or ev_periodic_again is being called.

 	

 	
ev_tstamp interval [read-write]

 	

@@ -1485,6 +1498,15 @@ with priority higher than or equal to the event loop and one coroutine
 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).

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

 

 	
ev_prepare_init (ev_prepare *, callback)

 	
ev_check_init (ev_check *, callback)