#include <ev.h>
+
+ ev_io stdin_watcher;
+ ev_timer timeout_watcher;
+
+ /* called when data readable on stdin */
+ static void
+ stdin_cb (EV_P_ struct ev_io *w, int revents)
+ {
+ /* puts ("stdin ready"); */
+ ev_io_stop (EV_A_ w); /* just a syntax example */
+ ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
+ }
+
+ static void
+ timeout_cb (EV_P_ struct ev_timer *w, int revents)
+ {
+ /* puts ("timeout"); */
+ ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
+ }
+
+ int
+ main (void)
+ {
+ struct ev_loop *loop = ev_default_loop (0);
+
+ /* initialise an io watcher, then start it */
+ ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
+ ev_io_start (loop, &stdin_watcher);
+
+ /* simple non-repeating 5.5 second timeout */
+ ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
+ ev_timer_start (loop, &timeout_watcher);
+
+ /* loop till timeout or data ready */
+ ev_loop (loop, 0);
+
+ return 0;
+ }
+
+
+
Libev supports select, poll, the linux-specific epoll and the bsd-specific -kqueue mechanisms for file descriptor events, relative timers, absolute -timers with customised rescheduling, signal events, process status change -events (related to SIGCHLD), and event watchers dealing with the event -loop mechanism itself (idle, prepare and check watchers). It also is quite -fast (see this benchmark comparing -it to libevent for example).
+Libev supports select, poll, the linux-specific epoll, the
+bsd-specific kqueue and the solaris-specific event port mechanisms
+for file descriptor events (ev_io), relative timers (ev_timer),
+absolute timers with customised rescheduling (ev_periodic), synchronous
+signals (ev_signal), process status change events (ev_child), and
+event watchers dealing with the event loop mechanism itself (ev_idle,
+ev_embed, ev_prepare and ev_check watchers) as well as
+file watchers (ev_stat) and even limited support for fork events
+(ev_fork).
It also is quite fast (see this +benchmark comparing it to libevent +for example).
Libev is very configurable. In this manual the default configuration
-will be described, which supports multiple event loops. For more info
-about various configuration options please have a look at the file
-README.embed in the libev distribution. If libev was configured without
-support for multiple event loops, then all functions taking an initial
-argument of name loop (which is always of type struct ev_loop *)
-will not have this argument.
Libev is very configurable. In this manual the default configuration will
+be described, which supports multiple event loops. For more info about
+various configuration options please have a look at EMBED section in
+this manual. If libev was configured without support for multiple event
+loops, then all functions taking an initial argument of name loop
+(which is always of type struct ev_loop *) will not have this argument.
Example: make sure we haven't accidentally been linked against the wrong -version:
+Example: Make sure we haven't accidentally been linked against the wrong +version.
assert (("libev version mismatch",
ev_version_major () == EV_VERSION_MAJOR
&& ev_version_minor () >= EV_VERSION_MINOR));
@@ -181,20 +231,20 @@ might be supported on the current system, you would need to look at
recommended ones.
See the description of ev_embed watchers for more info.
- Sets the allocation function to use (the prototype is similar to the -realloc C function, the semantics are identical). It is used to allocate -and free memory (no surprises here). If it returns zero when memory -needs to be allocated, the library might abort or take some potentially -destructive action. The default is your system realloc function.
+Sets the allocation function to use (the prototype and semantics are +identical to the realloc C function). It is used to allocate and free +memory (no surprises here). If it returns zero when memory needs to be +allocated, the library might abort or take some potentially destructive +action. The default is your system realloc function.
You could override this function in high-availability programs to, say, free some memory if it cannot allocate memory, to use a special allocator, or even to sleep a while and retry until some memory is available.
-Example: replace the libev allocator with one that waits a bit and then -retries: better than mine).
+Example: Replace the libev allocator with one that waits a bit and then +retries).
static void *
- persistent_realloc (void *ptr, long size)
+ persistent_realloc (void *ptr, size_t size)
{
for (;;)
{
@@ -221,7 +271,7 @@ callback is set, then libev will expect it to remedy the sitution, no
matter what, when it returns. That is, libev will generally retry the
requested operation, or, if the condition doesn't go away, do bad stuff
(such as abort).
- Example: do the same thing as libev does internally:
+ Example: This is basically the same thing that libev does internally, too.
static void
fatal_error (const char *msg)
{
@@ -367,7 +417,7 @@ event loop and only if you know the OS supports your types of fds):
always distinct from the default loop. Unlike the default loop, it cannot
handle signal and child watchers, and attempts to do so will be greeted by
undefined behaviour (or a failed assertion if assertions are enabled).
- Example: try to create a event loop that uses epoll and nothing else.
+ Example: Try to create a event loop that uses epoll and nothing else.
struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
if (!epoller)
fatal ("no epoll found here, maybe it hides under your chair");
@@ -470,7 +520,7 @@ usually a better approach for this kind of thing.
were used, return, otherwise continue with step *.
- Example: queue some jobs and then loop until no events are outsanding
+
Example: Queue some jobs and then loop until no events are outsanding
anymore.
... queue jobs here, make sure they register event watchers as long
... as they still have work to do (even an idle watcher will do..)
@@ -499,17 +549,17 @@ visible to the libev user and should not keep ev_loop from exiting
no event watchers registered by it are active. It is also an excellent
way to do this for generic recurring timers or from within third-party
libraries. Just remember to unref after start and ref before stop.
- Example: create a signal watcher, but keep it from keeping ev_loop
+
Example: Create a signal watcher, but keep it from keeping ev_loop
running when nothing else is active.
- struct dv_signal exitsig;
+ struct ev_signal exitsig;
ev_signal_init (&exitsig, sig_cb, SIGINT);
- ev_signal_start (myloop, &exitsig);
- evf_unref (myloop);
+ ev_signal_start (loop, &exitsig);
+ evf_unref (loop);
- Example: for some weird reason, unregister the above signal handler again.
- ev_ref (myloop);
- ev_signal_stop (myloop, &exitsig);
+ Example: For some weird reason, unregister the above signal handler again.
+ ev_ref (loop);
+ ev_signal_stop (loop, &exitsig);
EV_READ, EV_WRITEThe events being watched.
-Example: call stdin_readable_cb when STDIN_FILENO has become, well
+
Example: Call stdin_readable_cb when STDIN_FILENO has become, well
readable, but only once. Since it is likely line-buffered, you could
-attempt to read a whole line in the callback:
+attempt to read a whole line in the callback.
static void
stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
{
@@ -908,7 +958,7 @@ or ev_timer_again is called and determines the next timeout (if any
which is also when any modifications are taken into account.
-Example: create a timer that fires after 60 seconds.
+Example: Create a timer that fires after 60 seconds.
static void
one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
{
@@ -920,7 +970,7 @@ which is also when any modifications are taken into account.
ev_timer_start (loop, &mytimer);
-Example: create a timeout timer that times out after 10 seconds of
+
Example: Create a timeout timer that times out after 10 seconds of
inactivity.
static void
timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
@@ -1046,7 +1096,7 @@ switched off. Can be changed any time, but changes only take effect when
the periodic timer fires or ev_periodic_again is being called.
-Example: call a callback every hour, or, more precisely, whenever the
+
Example: Call a callback every hour, or, more precisely, whenever the
system clock is divisible by 3600. The callback invocation times have
potentially a lot of jittering, but good long-term stability.
static void
@@ -1060,7 +1110,7 @@ potentially a lot of jittering, but good long-term stability.
ev_periodic_start (loop, &hourly_tick);
-Example: the same as above, but use a reschedule callback to do it:
+Example: The same as above, but use a reschedule callback to do it:
#include <math.h>
static ev_tstamp
@@ -1072,7 +1122,7 @@ potentially a lot of jittering, but good long-term stability.
ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
-Example: call a callback every hour, starting now:
+Example: Call a callback every hour, starting now:
struct ev_periodic hourly_tick;
ev_periodic_init (&hourly_tick, clock_cb,
fmod (ev_now (loop), 3600.), 3600., 0);
@@ -1143,7 +1193,7 @@ process causing the status change.
waitpid and sys/wait.h documentation for details).
-Example: try to exit cleanly on SIGINT and SIGTERM.
+Example: Try to exit cleanly on SIGINT and SIGTERM.
static void
sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
{
@@ -1276,8 +1326,8 @@ kind. There is a ev_idle_set macro, but using it is utterly pointle
believe me.
-Example: dynamically allocate an ev_idle, start it, and in the
-callback, free it. Alos, use no error checking, as usual.
+Example: Dynamically allocate an ev_idle watcher, start it, and in the
+callback, free it. Also, use no error checking, as usual.
static void
idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
{
@@ -1997,6 +2047,13 @@ defined to be 0, then they are not.
If you need to shave off some kilobytes of code at the expense of some
speed, define this symbol to 1. Currently only used for gcc to override
some inlining decisions, saves roughly 30% codesize of amd64.
+
+
EV_PID_HASHSIZE
+
+ ev_child watchers use a small hash table to distribute workload by
+pid. The default size is 16 (or 1 with EV_MINIMAL), usually more
+than enough. If you need to manage thousands of children you might want to
+increase this value.
EV_COMMON