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- <meta name="created" content="Thu Nov 22 13:26:17 2007" />
+ <meta name="created" content="Fri Nov 23 09:26:40 2007" />
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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.</p>
+ </dd>
+ <dt>unsigned int ev_supported_backends ()</dt>
+ <dd>
+ <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
+value) compiled into this binary of libev (independent of their
+availability on the system you are running on). See <code>ev_default_loop</code> for
+a description of the set values.</p>
+ </dd>
+ <dt>unsigned int ev_recommended_backends ()</dt>
+ <dd>
+ <p>Return the set of all backends compiled into this binary of libev and also
+recommended for this platform. This set is often smaller than the one
+returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
+most BSDs and will not be autodetected unless you explicitly request it
+(assuming you know what you are doing). This is the set of backends that
+<code>EVFLAG_AUTO</code> will probe for.</p>
</dd>
<dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
<dd>
<p>This will initialise the default event loop if it hasn't been initialised
yet and return it. If the default loop could not be initialised, returns
false. If it already was initialised it simply returns it (and ignores the
-flags).</p>
+flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
<p>If you don't know what event loop to use, use the one returned from this
function.</p>
<p>The flags argument can be used to specify special behaviour or specific
-backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p>
+backends to use, and is usually specified as <code>0</code> (or EVFLAG_AUTO).</p>
<p>It supports the following flags:</p>
<p>
<dl>
useful to try out specific backends to test their performance, or to work
around bugs.</p>
</dd>
- <dt><code>EVMETHOD_SELECT</code> (value 1, portable select backend)</dt>
+ <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
<dd>
<p>This is your standard select(2) backend. Not <i>completely</i> standard, as
libev tries to roll its own fd_set with no limits on the number of fds,
using this backend. It doesn't scale too well (O(highest_fd)), but its usually
the fastest backend for a low number of fds.</p>
</dd>
- <dt><code>EVMETHOD_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
+ <dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
<dd>
<p>And this is your standard poll(2) backend. It's more complicated than
select, but handles sparse fds better and has no artificial limit on the
number of fds you can use (except it will slow down considerably with a
lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
</dd>
- <dt><code>EVMETHOD_EPOLL</code> (value 4, Linux)</dt>
+ <dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
<dd>
<p>For few fds, this backend is a bit little slower than poll and select,
but it scales phenomenally better. While poll and select usually scale like
(because the fd could point to a different file description now), so its
best to avoid that. Also, dup()ed file descriptors might not work very
well if you register events for both fds.</p>
+ <p>Please note that epoll sometimes generates spurious notifications, so you
+need to use non-blocking I/O or other means to avoid blocking when no data
+(or space) is available.</p>
</dd>
- <dt><code>EVMETHOD_KQUEUE</code> (value 8, most BSD clones)</dt>
+ <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
<dd>
<p>Kqueue deserves special mention, as at the time of this writing, it
was broken on all BSDs except NetBSD (usually it doesn't work with
extra syscall as with epoll, it still adds up to four event changes per
incident, so its best to avoid that.</p>
</dd>
- <dt><code>EVMETHOD_DEVPOLL</code> (value 16, Solaris 8)</dt>
+ <dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
<dd>
<p>This is not implemented yet (and might never be).</p>
</dd>
- <dt><code>EVMETHOD_PORT</code> (value 32, Solaris 10)</dt>
+ <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
<dd>
<p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
it's really slow, but it still scales very well (O(active_fds)).</p>
+ <p>Please note that solaris ports can result in a lot of spurious
+notifications, so you need to use non-blocking I/O or other means to avoid
+blocking when no data (or space) is available.</p>
</dd>
- <dt><code>EVMETHOD_ALL</code></dt>
+ <dt><code>EVBACKEND_ALL</code></dt>
<dd>
- <p>Try all backends (even potentially broken ones). Since this is a mask, you
-can do stuff like <code>EVMETHOD_ALL & ~EVMETHOD_KQUEUE</code>.</p>
+ <p>Try all backends (even potentially broken ones that wouldn't be tried
+with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
+<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p>
</dd>
</dl>
</p>
one. Despite the name, you can call it anytime, but it makes most sense
after forking, in either the parent or child process (or both, but that
again makes little sense).</p>
- <p>You <i>must</i> 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.</p>
+ <p>You <i>must</i> call this function in the child process 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.</p>
<p>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 <code>pthread_atfork</code>:</p>
<pre> pthread_atfork (0, 0, ev_default_fork);
</pre>
+ <p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
+without calling this function, so if you force one of those backends you
+do not need to care.</p>
</dd>
<dt>ev_loop_fork (loop)</dt>
<dd>
<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
after fork, and how you do this is entirely your own problem.</p>
</dd>
- <dt>unsigned int ev_method (loop)</dt>
+ <dt>unsigned int ev_backend (loop)</dt>
<dd>
- <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in
+ <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
use.</p>
</dd>
<dt>ev_tstamp ev_now (loop)</dt>
corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p>
<p>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.</p>
+reinitialise it or call its set macro.</p>
<p>You can check whether an event is active by calling the <code>ev_is_active
(watcher *)</code> macro. To see whether an event is outstanding (but the
callback for it has not been called yet) you can use the <code>ev_is_pending
to the same underlying file/socket etc. description (that is, they share
the same underlying "file open").</p>
<p>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).</p>
+(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
+<code>EVBACKEND_POLL</code>).</p>
<dl>
<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
<dt>ev_io_set (ev_io *, int fd, int events)</dt>
<p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ |
EV_WRITE</code> to receive the given events.</p>
+ <p>Please note that most of the more scalable backend mechanisms (for example
+epoll and solaris ports) can result in spurious readyness notifications
+for file descriptors, so you practically need to use non-blocking I/O (and
+treat callback invocation as hint only), or retest separately with a safe
+interface before doing I/O (XLib can do this), or force the use of either
+<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this
+problem. Also note that it is quite easy to have your callback invoked
+when the readyness condition is no longer valid even when employing
+typical ways of handling events, so its a good idea to use non-blocking
+I/O unconditionally.</p>
</dd>
</dl>
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