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- <meta name="created" content="Sat Nov 24 08:20:38 2007" />
+ <meta name="created" content="Mon Nov 26 11:20:35 2007" />
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<body>
<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
-<ul><li><a href="#SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</a></li>
+<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li>
<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
</ul>
</li>
<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
-<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li>
-<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li>
-<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li>
-<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li>
-<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li>
-<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li>
-<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li>
-<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</a></li>
+<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</a></li>
+<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li>
+<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li>
+<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li>
+<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li>
+<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</a></li>
+<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</a></li>
+<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li>
</ul>
</li>
<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
+<li><a href="#EMBEDDING">EMBEDDING</a>
+<ul><li><a href="#FILESETS">FILESETS</a>
+<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li>
+<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li>
+<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li>
+</ul>
+</li>
+<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li>
+<li><a href="#EXAMPLES">EXAMPLES</a></li>
+</ul>
+</li>
+<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li>
<li><a href="#AUTHOR">AUTHOR</a>
</li>
</ul><hr />
</dd>
</dl>
+
+
+
+
</div>
<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
<div id="ANATOMY_OF_A_WATCHER_CONTENT">
</dl>
</div>
-<h2 id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</h2>
-<div id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS-2">
+<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2>
+<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT">
<p>In the following description, <code>TYPE</code> stands for the watcher type,
e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p>
<dl>
which rolls both calls into one.</p>
<p>You can reinitialise a watcher at any time as long as it has been stopped
(or never started) and there are no pending events outstanding.</p>
- <p>The callbakc is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
+ <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher,
int revents)</code>.</p>
</dd>
<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt>
</div>
-<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
+<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2>
<div id="code_ev_io_code_is_this_file_descrip-2">
<p>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 can stop the watcher if you don't want to
-act on the event and neither want to receive future events).</p>
+in each iteration of the event loop, or, more precisely, when reading
+would not block the process and writing would at least be able to write
+some data. This behaviour is called level-triggering because you keep
+receiving events as long as the condition persists. Remember you can stop
+the watcher if you don't want to act on the event and neither want to
+receive future events.</p>
<p>In general you can register as many read and/or write event watchers per
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
<p>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 underlying file/socket etc. description (that is, they share
+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 <code>EVBACKEND_SELECT</code> and
<code>EVBACKEND_POLL</code>).</p>
+<p>Another thing you have to watch out for is that it is quite easy to
+receive "spurious" readyness notifications, that is your callback might
+be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block
+because there is no data. Not only are some backends known to create a
+lot of those (for example solaris ports), it is very easy to get into
+this situation even with a relatively standard program structure. Thus
+it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
+<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
+<p>If you cannot run the fd in non-blocking mode (for example you should not
+play around with an Xlib connection), then you have to seperately re-test
+wether a file descriptor is really ready with a known-to-be good interface
+such as poll (fortunately in our Xlib example, Xlib already does this on
+its own, so its quite safe to use).</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>
<dd>
- <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>
+ <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> 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>
</dd>
</dl>
<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
</pre>
</div>
-<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
+<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2>
<div id="code_ev_timer_code_relative_and_opti-2">
<p>Timer watchers are simple relative timers that generate an event after a
given time, and optionally repeating in regular intervals after that.</p>
</pre>
</div>
-<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
+<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2>
<div id="code_ev_periodic_code_to_cron_or_not-2">
<p>Periodic watchers are also timers of a kind, but they are very versatile
(and unfortunately a bit complex).</p>
<p>Unlike <code>ev_timer</code>'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. <code>ev_now ()
++ 10.</code>) and then reset your system clock to the last year, then it will
take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
roughly 10 seconds later and of course not if you reset your system time
again).</p>
</pre>
</div>
-<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
+<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2>
<div id="code_ev_signal_code_signal_me_when_a-2">
<p>Signal watchers will trigger an event when the process receives a specific
signal one or more times. Even though signals are very asynchronous, libev
</div>
-<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
-<div id="code_ev_child_code_wait_for_pid_stat-2">
+<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2>
+<div id="code_ev_child_code_watch_out_for_pro-2">
<p>Child watchers trigger when your process receives a SIGCHLD in response to
some child status changes (most typically when a child of yours dies).</p>
<dl>
</pre>
</div>
-<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
+<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
<div id="code_ev_idle_code_when_you_ve_got_no-2">
<p>Idle watchers trigger events when there are no other events are pending
(prepare, check and other idle watchers do not count). That is, as long
</pre>
</div>
-<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
+<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2>
<div id="code_ev_prepare_code_and_code_ev_che-2">
<p>Prepare and check watchers are usually (but not always) used in tandem:
prepare watchers get invoked before the process blocks and check watchers
afterwards.</p>
+<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter
+the current event loop from either <code>ev_prepare</code> or <code>ev_check</code>
+watchers. Other loops than the current one are fine, however. The
+rationale behind this is that you do not need to check for recursion in
+those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking,
+<code>ev_check</code> so if you have one watcher of each kind they will always be
+called in pairs bracketing the blocking call.</p>
<p>Their main purpose is to integrate other event mechanisms into libev and
their use is somewhat advanced. This could be used, for example, to track
variable changes, implement your own watchers, integrate net-snmp or a
-coroutine library and lots more.</p>
+coroutine library and lots more. They are also occasionally useful if
+you cache some data and want to flush it before blocking (for example,
+in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code>
+watcher).</p>
<p>This is done by examining in each prepare call which file descriptors need
to be watched by the other library, registering <code>ev_io</code> watchers for
them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
macros, but using them is utterly, utterly and completely pointless.</p>
</dd>
</dl>
-<p>Example: *TODO*.</p>
+<p>Example: To include a library such as adns, you would add IO watchers
+and a timeout watcher in a prepare handler, as required by libadns, and
+in a check watcher, destroy them and call into libadns. What follows is
+pseudo-code only of course:</p>
+<pre> static ev_io iow [nfd];
+ static ev_timer tw;
+
+ static void
+ io_cb (ev_loop *loop, ev_io *w, int revents)
+ {
+ // set the relevant poll flags
+ // could also call adns_processreadable etc. here
+ struct pollfd *fd = (struct pollfd *)w->data;
+ if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
+ if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
+ }
+ // create io watchers for each fd and a timer before blocking
+ static void
+ adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
+ {
+ int timeout = 3600000;truct pollfd fds [nfd];
+ // actual code will need to loop here and realloc etc.
+ adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
+
+ /* the callback is illegal, but won't be called as we stop during check */
+ ev_timer_init (&tw, 0, timeout * 1e-3);
+ ev_timer_start (loop, &tw);
+
+ // create on ev_io per pollfd
+ for (int i = 0; i < nfd; ++i)
+ {
+ ev_io_init (iow + i, io_cb, fds [i].fd,
+ ((fds [i].events & POLLIN ? EV_READ : 0)
+ | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
+
+ fds [i].revents = 0;
+ iow [i].data = fds + i;
+ ev_io_start (loop, iow + i);
+ }
+ }
+ // stop all watchers after blocking
+ static void
+ adns_check_cb (ev_loop *loop, ev_check *w, int revents)
+ {
+ ev_timer_stop (loop, &tw);
+ for (int i = 0; i < nfd; ++i)
+ ev_io_stop (loop, iow + i);
+ adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
+ }
+
+
+
+
+</pre>
</div>
-<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2>
+<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2>
<div id="code_ev_embed_code_when_one_backend_-2">
<p>This is a rather advanced watcher type that lets you embed one event loop
into another (currently only <code>ev_io</code> events are supported in the embedded
</div>
<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
<div id="C_SUPPORT_CONTENT">
-<p>TBD.</p>
+<p>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.</p>
+<p>To use it,</p>
+<pre> #include <ev++.h>
+
+</pre>
+<p>(it is not installed by default). This automatically includes <cite>ev.h</cite>
+and puts all of its definitions (many of them macros) into the global
+namespace. All C++ specific things are put into the <code>ev</code> namespace.</p>
+<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably
+<code>EV_MULTIPLICITY</code>.</p>
+<p>Here is a list of things available in the <code>ev</code> namespace:</p>
+<dl>
+ <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
+ <dd>
+ <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
+macros from <cite>ev.h</cite>.</p>
+ </dd>
+ <dt><code>ev::tstamp</code>, <code>ev::now</code></dt>
+ <dd>
+ <p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p>
+ </dd>
+ <dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt>
+ <dd>
+ <p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of
+the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code>
+which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
+defines by many implementations.</p>
+ <p>All of those classes have these methods:</p>
+ <p>
+ <dl>
+ <dt>ev::TYPE::TYPE (object *, object::method *)</dt>
+ <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt>
+ <dt>ev::TYPE::~TYPE</dt>
+ <dd>
+ <p>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
+<code>ev_init</code> for you, which means you have to call the <code>set</code> method
+before starting it. If you do not specify a loop then the constructor
+automatically associates the default loop with this watcher.</p>
+ <p>The destructor automatically stops the watcher if it is active.</p>
+ </dd>
+ <dt>w->set (struct ev_loop *)</dt>
+ <dd>
+ <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
+do this when the watcher is inactive (and not pending either).</p>
+ </dd>
+ <dt>w->set ([args])</dt>
+ <dd>
+ <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
+called at least once. Unlike the C counterpart, an active watcher gets
+automatically stopped and restarted.</p>
+ </dd>
+ <dt>w->start ()</dt>
+ <dd>
+ <p>Starts the watcher. Note that there is no <code>loop</code> argument as the
+constructor already takes the loop.</p>
+ </dd>
+ <dt>w->stop ()</dt>
+ <dd>
+ <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
+ </dd>
+ <dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt>
+ <dd>
+ <p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding
+<code>ev_TYPE_again</code> function.</p>
+ </dd>
+ <dt>w->sweep () <code>ev::embed</code> only</dt>
+ <dd>
+ <p>Invokes <code>ev_embed_sweep</code>.</p>
+ </dd>
+ </dl>
+ </p>
+ </dd>
+</dl>
+<p>Example: Define a class with an IO and idle watcher, start one of them in
+the constructor.</p>
+<pre> 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);
+ }
+
+</pre>
+
+</div>
+<h1 id="EMBEDDING">EMBEDDING</h1><p><a href="#TOP" class="toplink">Top</a></p>
+<div id="EMBEDDING_CONTENT">
+<p>Libev can (and often is) directly embedded into host
+applications. Examples of applications that embed it include the Deliantra
+Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
+and rxvt-unicode.</p>
+<p>The goal is to enable you to just copy the neecssary files into your
+source directory without having to change even a single line in them, so
+you can easily upgrade by simply copying (or having a checked-out copy of
+libev somewhere in your source tree).</p>
+
+</div>
+<h2 id="FILESETS">FILESETS</h2>
+<div id="FILESETS_CONTENT">
+<p>Depending on what features you need you need to include one or more sets of files
+in your app.</p>
+
+</div>
+<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3>
+<div id="CORE_EVENT_LOOP_CONTENT">
+<p>To include only the libev core (all the <code>ev_*</code> functions), with manual
+configuration (no autoconf):</p>
+<pre> #define EV_STANDALONE 1
+ #include "ev.c"
+
+</pre>
+<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a
+single C source file only to provide the function implementations. To use
+it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best
+done by writing a wrapper around <cite>ev.h</cite> that you can include instead and
+where you can put other configuration options):</p>
+<pre> #define EV_STANDALONE 1
+ #include "ev.h"
+
+</pre>
+<p>Both header files and implementation files can be compiled with a C++
+compiler (at least, thats a stated goal, and breakage will be treated
+as a bug).</p>
+<p>You need the following files in your source tree, or in a directory
+in your include path (e.g. in libev/ when using -Ilibev):</p>
+<pre> ev.h
+ ev.c
+ ev_vars.h
+ ev_wrap.h
+
+ ev_win32.c required on win32 platforms only
+
+ ev_select.c only when select backend is enabled (which is by default)
+ ev_poll.c only when poll backend is enabled (disabled by default)
+ ev_epoll.c only when the epoll backend is enabled (disabled by default)
+ ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
+ ev_port.c only when the solaris port backend is enabled (disabled by default)
+
+</pre>
+<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need
+to compile this single file.</p>
+
+</div>
+<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3>
+<div id="LIBEVENT_COMPATIBILITY_API_CONTENT">
+<p>To include the libevent compatibility API, also include:</p>
+<pre> #include "event.c"
+
+</pre>
+<p>in the file including <cite>ev.c</cite>, and:</p>
+<pre> #include "event.h"
+
+</pre>
+<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p>
+<p>You need the following additional files for this:</p>
+<pre> event.h
+ event.c
+
+</pre>
+
+</div>
+<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3>
+<div id="AUTOCONF_SUPPORT_CONTENT">
+<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in
+whatever way you want, you can also <code>m4_include([libev.m4])</code> in your
+<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then
+include <cite>config.h</cite> and configure itself accordingly.</p>
+<p>For this of course you need the m4 file:</p>
+<pre> libev.m4
+
+</pre>
+
+</div>
+<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2>
+<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT">
+<p>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.</p>
+<dl>
+ <dt>EV_STANDALONE</dt>
+ <dd>
+ <p>Must always be <code>1</code> if you do not use autoconf configuration, which
+keeps libev from including <cite>config.h</cite>, 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
+<cite>event.h</cite> that are not directly supported by the libev core alone.</p>
+ </dd>
+ <dt>EV_USE_MONOTONIC</dt>
+ <dd>
+ <p>If defined to be <code>1</code>, 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 <code>clock_gettime</code>
+function is hiding in (often <cite>-lrt</cite>).</p>
+ </dd>
+ <dt>EV_USE_REALTIME</dt>
+ <dd>
+ <p>If defined to be <code>1</code>, 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 <code>gettimeofday</code> by <code>clock_get
+(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries
+in the description of <code>EV_USE_MONOTONIC</code>, though.</p>
+ </dd>
+ <dt>EV_USE_SELECT</dt>
+ <dd>
+ <p>If undefined or defined to be <code>1</code>, libev will compile in support for the
+<code>select</code>(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.</p>
+ </dd>
+ <dt>EV_SELECT_USE_FD_SET</dt>
+ <dd>
+ <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code>
+structure. This is useful if libev doesn't compile due to a missing
+<code>NFDBITS</code> or <code>fd_mask</code> 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 <code>FD_SETSIZE</code> macro, set before compilation, might
+influence the size of the <code>fd_set</code> used.</p>
+ </dd>
+ <dt>EV_SELECT_IS_WINSOCKET</dt>
+ <dd>
+ <p>When defined to <code>1</code>, 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
+<code>_get_osfhandle</code> 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.</p>
+ </dd>
+ <dt>EV_USE_POLL</dt>
+ <dd>
+ <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2)
+backend. Otherwise it will be enabled on non-win32 platforms. It
+takes precedence over select.</p>
+ </dd>
+ <dt>EV_USE_EPOLL</dt>
+ <dd>
+ <p>If defined to be <code>1</code>, libev will compile in support for the Linux
+<code>epoll</code>(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.</p>
+ </dd>
+ <dt>EV_USE_KQUEUE</dt>
+ <dd>
+ <p>If defined to be <code>1</code>, libev will compile in support for the BSD style
+<code>kqueue</code>(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 whether kqueue supports your type of fd properly and use an embedded
+kqueue loop.</p>
+ </dd>
+ <dt>EV_USE_PORT</dt>
+ <dd>
+ <p>If defined to be <code>1</code>, 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.</p>
+ </dd>
+ <dt>EV_USE_DEVPOLL</dt>
+ <dd>
+ <p>reserved for future expansion, works like the USE symbols above.</p>
+ </dd>
+ <dt>EV_H</dt>
+ <dd>
+ <p>The name of the <cite>ev.h</cite> header file used to include it. The default if
+undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This
+can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p>
+ </dd>
+ <dt>EV_CONFIG_H</dt>
+ <dd>
+ <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override
+<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to
+<code>EV_H</code>, above.</p>
+ </dd>
+ <dt>EV_EVENT_H</dt>
+ <dd>
+ <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea
+of how the <cite>event.h</cite> header can be found.</p>
+ </dd>
+ <dt>EV_PROTOTYPES</dt>
+ <dd>
+ <p>If defined to be <code>0</code>, then <cite>ev.h</cite> 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.</p>
+ </dd>
+ <dt>EV_MULTIPLICITY</dt>
+ <dd>
+ <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions
+will have the <code>struct ev_loop *</code> 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.</p>
+ </dd>
+ <dt>EV_PERIODICS</dt>
+ <dd>
+ <p>If undefined or defined to be <code>1</code>, then periodic timers are supported,
+otherwise not. This saves a few kb of code.</p>
+ </dd>
+ <dt>EV_COMMON</dt>
+ <dd>
+ <p>By default, all watchers have a <code>void *data</code> 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.</p>
+ <p>For example, the perl EV module uses something like this:</p>
+<pre> #define EV_COMMON \
+ SV *self; /* contains this struct */ \
+ SV *cb_sv, *fh /* note no trailing ";" */
+
+</pre>
+ </dd>
+ <dt>EV_CB_DECLARE (type)</dt>
+ <dt>EV_CB_INVOKE (watcher, revents)</dt>
+ <dt>ev_set_cb (ev, cb)</dt>
+ <dd>
+ <p>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 <cite>ev.v</cite> header file for
+their default definitions. One possible use for overriding these is to
+avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use
+method calls instead of plain function calls in C++.</p>
+
+</div>
+<h2 id="EXAMPLES">EXAMPLES</h2>
+<div id="EXAMPLES_CONTENT">
+ <p>For a real-world example of a program the includes libev
+verbatim, you can have a look at the EV perl module
+(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in
+the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
+interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
+will be compiled. It is pretty complex because it provides its own header
+file.</p>
+ <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
+that everybody includes and which overrides some autoconf choices:</p>
+<pre> #define EV_USE_POLL 0
+ #define EV_MULTIPLICITY 0
+ #define EV_PERIODICS 0
+ #define EV_CONFIG_H <config.h>
+
+ #include "ev++.h"
+
+</pre>
+ <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
+<pre> #include "ev_cpp.h"
+ #include "ev.c"
+
+
+
+
+</pre>
+
+</div>
+<h1 id="COMPLEXITIES">COMPLEXITIES</h1><p><a href="#TOP" class="toplink">Top</a></p>
+<div id="COMPLEXITIES_CONTENT">
+ <p>In this section the complexities of (many of) the algorithms used inside
+libev will be explained. For complexity discussions about backends see the
+documentation for <code>ev_default_init</code>.</p>
+ <p>
+ <dl>
+ <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
+ <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
+ <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
+ <dt>Stopping check/prepare/idle watchers: O(1)</dt>
+ <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))</dt>
+ <dt>Finding the next timer per loop iteration: O(1)</dt>
+ <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
+ <dt>Activating one watcher: O(1)</dt>
+ </dl>
+ </p>
+
+
+
+
</div>
<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
<div id="AUTHOR_CONTENT">
-<p>Marc Lehmann <libev@schmorp.de>.</p>
+
<p>Marc Lehmann <libev@schmorp.de>.</p>
</div>
</div></body>
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