Unlike ev_timer's, they are not based on real time (or relative time) but on wallclock time (absolute time). You can tell a periodic watcher 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 +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).

C++ SUPPORT

TBD.

Libev comes with some simplistic wrapper classes for C++ that mainly allow +you to use some convinience methods to start/stop watchers and also change +the callback model to a model using method callbacks on objects.

To use it,

  #include <ev++.h>
+
+

(it is not installed by default). This automatically includes ev.h +and puts all of its definitions (many of them macros) into the global +namespace. All C++ specific things are put into the ev namespace.

It should support all the same embedding options as ev.h, most notably +EV_MULTIPLICITY.

Here is a list of things available in the ev namespace:

ev::READ, ev::WRITE etc.

These are just enum values with the same values as the EV_READ etc. +macros from ev.h.

ev::tstamp, ev::now

Aliases to the same types/functions as with the ev_ prefix.

ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc.

For each ev_TYPE watcher in ev.h there is a corresponding class of +the same name in the ev namespace, with the exception of ev_signal +which is called ev::sig to avoid clashes with the signal macro +defines by many implementations.

All of those classes have these methods:

ev::TYPE::TYPE (object *, object::method *)

ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)

ev::TYPE::~TYPE

The constructor takes a pointer to an object and a method pointer to +the event handler callback to call in this class. The constructor calls +ev_init for you, which means you have to call the set method +before starting it. If you do not specify a loop then the constructor +automatically associates the default loop with this watcher.

The destructor automatically stops the watcher if it is active.

w->set (struct ev_loop *)

Associates a different struct ev_loop with this watcher. You can only +do this when the watcher is inactive (and not pending either).

w->set ([args])

Basically the same as ev_TYPE_set, with the same args. Must be +called at least once. Unlike the C counterpart, an active watcher gets +automatically stopped and restarted.

w->start ()

Starts the watcher. Note that there is no loop argument as the +constructor already takes the loop.

w->stop ()

Stops the watcher if it is active. Again, no loop argument.

w->again () ev::timer, ev::periodic only

For ev::timer and ev::periodic, this invokes the corresponding +ev_TYPE_again function.

w->sweep () ev::embed only

Invokes ev_embed_sweep.

Example: Define a class with an IO and idle watcher, start one of them in +the constructor.

  class myclass
+  {
+    ev_io   io;   void io_cb   (ev::io   &w, int revents);
+    ev_idle idle  void idle_cb (ev::idle &w, int revents);
+
+    myclass ();
+  }
+
+  myclass::myclass (int fd)
+  : io   (this, &myclass::io_cb),
+    idle (this, &myclass::idle_cb)
+  {
+    io.start (fd, ev::READ);
+  }
+
+

+ +

EMBEDDING

FILESETS

CORE EVENT LOOP

LIBEVENT COMPATIBILITY API

AUTOCONF SUPPORT

PREPROCESSOR SYMBOLS/MACROS

Libev can be configured via a variety of preprocessor symbols you have to define +before including any of its files. The default is not to build for multiplicity +and only include the select backend.

EV_STANDALONE

Must always be 1 if you do not use autoconf configuration, which +keeps libev from including config.h, and it also defines dummy +implementations for some libevent functions (such as logging, which is not +supported). It will also not define any of the structs usually found in +event.h that are not directly supported by the libev core alone.

EV_USE_MONOTONIC

If defined to be 1, libev will try to detect the availability of the +monotonic clock option at both compiletime and runtime. Otherwise no use +of the monotonic clock option will be attempted. If you enable this, you +usually have to link against librt or something similar. Enabling it when +the functionality isn't available is safe, though, althoguh you have +to make sure you link against any libraries where the clock_gettime +function is hiding in (often -lrt).

EV_USE_REALTIME

If defined to be 1, libev will try to detect the availability of the +realtime clock option at compiletime (and assume its availability at +runtime if successful). Otherwise no use of the realtime clock option will +be attempted. This effectively replaces gettimeofday by clock_get +(CLOCK_REALTIME, ...) and will not normally affect correctness. See tzhe note about libraries +in the description of EV_USE_MONOTONIC, though.

EV_USE_SELECT

If undefined or defined to be 1, libev will compile in support for the +select(2) backend. No attempt at autodetection will be done: if no +other method takes over, select will be it. Otherwise the select backend +will not be compiled in.

EV_SELECT_USE_FD_SET

If defined to 1, then the select backend will use the system fd_set +structure. This is useful if libev doesn't compile due to a missing +NFDBITS or fd_mask definition or it misguesses the bitset layout on +exotic systems. This usually limits the range of file descriptors to some +low limit such as 1024 or might have other limitations (winsocket only +allows 64 sockets). The FD_SETSIZE macro, set before compilation, might +influence the size of the fd_set used.

EV_SELECT_IS_WINSOCKET

When defined to 1, the select backend will assume that +select/socket/connect etc. don't understand file descriptors but +wants osf handles on win32 (this is the case when the select to +be used is the winsock select). This means that it will call +_get_osfhandle on the fd to convert it to an OS handle. Otherwise, +it is assumed that all these functions actually work on fds, even +on win32. Should not be defined on non-win32 platforms.

EV_USE_POLL

If defined to be 1, libev will compile in support for the poll(2) +backend. Otherwise it will be enabled on non-win32 platforms. It +takes precedence over select.

EV_USE_EPOLL

If defined to be 1, libev will compile in support for the Linux +epoll(7) backend. Its availability will be detected at runtime, +otherwise another method will be used as fallback. This is the +preferred backend for GNU/Linux systems.

EV_USE_KQUEUE

If defined to be 1, libev will compile in support for the BSD style +kqueue(2) backend. Its actual availability will be detected at runtime, +otherwise another method will be used as fallback. This is the preferred +backend for BSD and BSD-like systems, although on most BSDs kqueue only +supports some types of fds correctly (the only platform we found that +supports ptys for example was NetBSD), so kqueue might be compiled in, but +not be used unless explicitly requested. The best way to use it is to find +out wether kqueue supports your type of fd properly and use an embedded +kqueue loop.

EV_USE_PORT

If defined to be 1, libev will compile in support for the Solaris +10 port style backend. Its availability will be detected at runtime, +otherwise another method will be used as fallback. This is the preferred +backend for Solaris 10 systems.

EV_USE_DEVPOLL

reserved for future expansion, works like the USE symbols above.

EV_H

The name of the ev.h header file used to include it. The default if +undefined is <ev.h> in event.h and "ev.h" in ev.c. This +can be used to virtually rename the ev.h header file in case of conflicts.

EV_CONFIG_H

If EV_STANDALONE isn't 1, this variable can be used to override +ev.c's idea of where to find the config.h file, similarly to +EV_H, above.

EV_EVENT_H

Similarly to EV_H, this macro can be used to override event.c's idea +of how the event.h header can be found.

EV_PROTOTYPES

If defined to be 0, then ev.h will not define any function +prototypes, but still define all the structs and other symbols. This is +occasionally useful if you want to provide your own wrapper functions +around libev functions.

EV_MULTIPLICITY

If undefined or defined to 1, then all event-loop-specific functions +will have the struct ev_loop * as first argument, and you can create +additional independent event loops. Otherwise there will be no support +for multiple event loops and there is no first event loop pointer +argument. Instead, all functions act on the single default loop.

EV_PERIODICS

If undefined or defined to be 1, then periodic timers are supported, +otherwise not. This saves a few kb of code.

EV_COMMON

By default, all watchers have a void *data member. By redefining +this macro to a something else you can include more and other types of +members. You have to define it each time you include one of the files, +though, and it must be identical each time.

For example, the perl EV module uses something like this:

  #define EV_COMMON                       \
+    SV *self; /* contains this struct */  \
+    SV *cb_sv, *fh /* note no trailing ";" */
+
+

EV_CB_DECLARE(type)

EV_CB_INVOKE(watcher,revents)

ev_set_cb(ev,cb)

Can be used to change the callback member declaration in each watcher, +and the way callbacks are invoked and set. Must expand to a struct member +definition and a statement, respectively. See the ev.v header file for +their default definitions. One possible use for overriding these is to +avoid the ev_loop pointer as first argument in all cases, or to use method +calls instead of plain function calls in C++.

+ +