Libev is very configurable. In this manual the default configuration will be described, which supports multiple event loops. For more info -about various configuraiton options please have a look at the file +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 *) @@ -107,7 +109,7 @@ 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.

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

@@ -115,10 +117,10 @@ not a problem.

ev_set_allocator (void *(*cb)(void *ptr, long size))

Sets the allocation function to use (the prototype is similar to the -realloc 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.

+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.

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.

@@ -129,7 +131,7 @@ or even to sleep a while and retry until some memory is available.

as failed select, poll, epoll_wait). The message is a printable string indicating the system call or subsystem causing the problem. If this callback is set, then libev will expect it to remedy the sitution, no -matter what, when it returns. That is, libev will geenrally retry the +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).

@@ -143,9 +145,10 @@ types of such loops, the default loop, which supports signals and child events, and dynamically created loops which do not.

If you use threads, a common model is to run the default event loop in your main thread (or in a separate thrad) and for each thread you -create, you also create another event loop. Libev itself does no lockign -whatsoever, so if you mix calls to different event loops, make sure you -lock (this is usually a bad idea, though, even if done right).

+create, you also create another event loop. Libev itself does no locking +whatsoever, so if you mix calls to the same event loop in different +threads, make sure you lock (this is usually a bad idea, though, even if +done correctly, because it's hideous and inefficient).

struct ev_loop *ev_default_loop (unsigned int flags)

@@ -156,29 +159,30 @@ flags).

If you don't know what event loop to use, use the one returned from this function.

The flags argument can be used to specify special behaviour or specific -backends to use, and is usually specified as 0 (or EVFLAG_AUTO)

+backends to use, and is usually specified as 0 (or EVFLAG_AUTO).

It supports the following flags:

EVFLAG_AUTO

The default flags value. Use this if you have no clue (its the right +

The default flags value. Use this if you have no clue (it's the right thing, believe me).

EVFLAG_NOENV

If this flag bit is ored into the flag value then libev will not look -at the environment variable LIBEV_FLAGS. Otherwise (the default), this -environment variable will override the flags completely. This is useful -to try out specific backends to tets their performance, or to work around -bugs.

If this flag bit is ored into the flag value (or the program runs setuid +or setgid) then libev will not look at the environment variable +LIBEV_FLAGS. Otherwise (the default), this environment variable will +override the flags completely if it is found in the environment. This is +useful to try out specific backends to test their performance, or to work +around bugs.

EVMETHOD_SELECT portable select backend

EVMETHOD_POLL poll backend (everywhere except windows)

EVMETHOD_EPOLL linux only

EVMETHOD_KQUEUE some bsds only

EVMETHOD_DEVPOLL solaris 8 only

EVMETHOD_PORT solaris 10 only

EVMETHOD_SELECT (portable select backend)

EVMETHOD_POLL (poll backend, available everywhere except on windows)

EVMETHOD_EPOLL (linux only)

EVMETHOD_KQUEUE (some bsds only)

EVMETHOD_DEVPOLL (solaris 8 only)

EVMETHOD_PORT (solaris 10 only)

If one or more of these are ored into the flags value, then only these backends will be tried (in the reverse order as given here). If one are @@ -198,7 +202,7 @@ undefined behaviour (or a failed assertion if assertions are enabled).

Destroys the default loop again (frees all memory and kernel state etc.). This stops all registered event watchers (by not touching them in -any way whatsoever, although you cnanot rely on this :).

+any way whatsoever, although you cannot rely on this :).

ev_loop_destroy (loop)

@@ -214,7 +218,7 @@ again makes little sense).

You must call this function after forking if and only if you want to use the event library in both processes. If you just fork+exec, you don't have to call it.

The function itself is quite fast and its usually not a problem to call +

The function itself is quite fast and it's usually not a problem to call it just in case after a fork. To make this easy, the function will fit in quite nicely into a call to pthread_atfork:

    pthread_atfork (0, 0, ev_default_fork);
@@ -232,7 +236,7 @@ after fork, and how you do this is entirely your own problem.
 		Returns one of the EVMETHOD_* flags indicating the event backend in
 use.

ev_tstamp = ev_now (loop)

ev_tstamp ev_now (loop)

Returns the current "event loop time", which is the time the event loop got events and started processing them. This timestamp does not change @@ -249,33 +253,35 @@ events.

no event watchers are active anymore or ev_unloop was called.

A flags value of EVLOOP_NONBLOCK will look for new events, will handle those events and any outstanding ones, but will not block your process in -case there are no events.

+case there are no events and will return after one iteration of the loop.

A flags value of EVLOOP_ONESHOT will look for new events (waiting if neccessary) and will handle those and any outstanding ones. It will block -your process until at least one new event arrives.

+your process until at least one new event arrives, and will return after +one iteration of the loop.

This flags value could be used to implement alternative looping constructs, but the prepare and check watchers provide a better and more generic mechanism.

ev_unloop (loop, how)

Can be used to make a call to ev_loop return early. The how argument -must be either EVUNLOOP_ONCE, which will make the innermost ev_loop -call return, or EVUNLOOP_ALL, which will make all nested ev_loop -calls return.

Can be used to make a call to ev_loop return early (but only after it +has processed all outstanding events). The how argument must be either +EVUNLOOP_ONCE, which will make the innermost ev_loop call return, or +EVUNLOOP_ALL, which will make all nested ev_loop calls return.

ev_ref (loop)

ev_unref (loop)

Ref/unref can be used to add or remove a refcount on the event loop: Every -watcher keeps one reference. If you have a long-runing watcher you never -unregister that should not keep ev_loop from running, ev_unref() after -starting, and ev_ref() before stopping it. Libev itself uses this for -example for its internal signal pipe: It is not visible to you as a user -and should not keep ev_loop from exiting if the work is done. 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.

Ref/unref can be used to add or remove a reference count on the event +loop: Every watcher keeps one reference, and as long as the reference +count is nonzero, ev_loop will not return on its own. If you have +a watcher you never unregister that should not keep ev_loop from +returning, ev_unref() after starting, and ev_ref() before stopping it. For +example, libev itself uses this for its internal signal pipe: It is not +visible to the libev user and should not keep ev_loop from exiting if +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.

@@ -318,8 +324,8 @@ corresponding stop function (ev_<type>_stop (loop, watcher *)

As long as your watcher is active (has been started but not stopped) you must not touch the values stored in it. Most specifically you must never reinitialise it or call its set method.

You cna check wether an event is active by calling the ev_is_active -(watcher *) macro. To see wether an event is outstanding (but the +

You cna check whether an event is active by calling the ev_is_active +(watcher *) macro. To see whether an event is outstanding (but the callback for it has not been called yet) you cna use the ev_is_pending (watcher *) macro.

Each and every callback receives the event loop pointer as first, the @@ -424,11 +430,22 @@ information given in the last section.

I/O watchers check wether a file descriptor is readable or writable +

I/O watchers check whether a file descriptor is readable or writable in each iteration of the event loop (This behaviour is called level-triggering because you keep receiving events as long as the condition persists. Remember you cna stop the watcher if you don't want to act on the event and neither want to receive future events).

In general you can register as many read and/or write event watchers oer +fd as you want (as long as you don't confuse yourself). Setting all file +descriptors to non-blocking mode is also usually a good idea (but not +required if you know what you are doing).

You have to be careful with dup'ed file descriptors, though. Some backends +(the linux epoll backend is a notable example) cannot handle dup'ed file +descriptors correctly if you register interest in two or more fds pointing +to the same file/socket etc. description.

If you must do this, then force the use of a known-to-be-good backend +(at the time of this writing, this includes only EVMETHOD_SELECT and +EVMETHOD_POLL).

ev_io_init (ev_io *, callback, int fd, int events)
ev_io_set (ev_io *, int fd, int events)

CONVENTIONS

struct ev_io - is my file descriptor readable or writable