[ViewVC] Diff of: cvs/libev/ev.html

Comparing libev/ev.html (file contents):
Revision 1.57 by root, Wed Nov 28 11:27:29 2007 UTC vs.
Revision 1.65 by root, Fri Dec 7 18:09:40 2007 UTC

 <head>
 	<title>libev</title>
 	<meta name="description" content="Pod documentation for libev" />
 	<meta name="inputfile" content="&lt;standard input&gt;" />
 	<meta name="outputfile" content="&lt;standard output&gt;" />
-	<meta name="created" content="Wed Nov 28 12:27:27 2007" />
+	<meta name="created" content="Fri Dec  7 19:03:06 2007" />
 	<meta name="generator" content="Pod::Xhtml 1.57" />
 <link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
 <body>
 <div class="pod">
 <!-- INDEX START -->
 watcher.</p>
 </div>
 <h1 id="FEATURES">FEATURES</h1>
 <div id="FEATURES_CONTENT">
-<p>Libev supports <code>select</code>, <code>poll</code>, the linux-specific <code>epoll</code>, the
+<p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the
-bsd-specific <code>kqueue</code> and the solaris-specific event port mechanisms
+BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
-for file descriptor events (<code>ev_io</code>), relative timers (<code>ev_timer</code>),
+for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
+(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
-absolute timers with customised rescheduling (<code>ev_periodic</code>), synchronous
+with customised rescheduling (<code>ev_periodic</code>), synchronous signals
-signals (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and
+(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
-event watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
+watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
 <code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
 file watchers (<code>ev_stat</code>) and even limited support for fork events
 (<code>ev_fork</code>).</p>
 <p>It also is quite fast (see this
 <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
 might be supported on the current system, you would need to look at
 <code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
 recommended ones.</p>
 		<p>See the description of <code>ev_embed</code> watchers for more info.</p>
 	</dd>
-	<dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt>
+	<dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
 	<dd>
-		<p>Sets the allocation function to use (the prototype and semantics are
+		<p>Sets the allocation function to use (the prototype is similar - the
-identical to the realloc C function). It is used to allocate and free
+semantics is identical - to the realloc C function). It is used to
-memory (no surprises here). If it returns zero when memory needs to be
+allocate and free memory (no surprises here). If it returns zero when
-allocated, the library might abort or take some potentially destructive
+memory needs to be allocated, the library might abort or take some
-action. The default is your system realloc function.</p>
+potentially destructive action. The default is your system realloc
+function.</p>
 		<p>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.</p>
 		<p>Example: Replace the libev allocator with one that waits a bit and then
 retries).</p>
 or setgid) then libev will <i>not</i> look at the environment variable
 <code>LIBEV_FLAGS</code>. 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.</p>
+				</dd>
+				<dt><code>EVFLAG_FORKCHECK</code></dt>
+				<dd>
+					<p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
+a fork, you can also make libev check for a fork in each iteration by
+enabling this flag.</p>
+					<p>This works by calling <code>getpid ()</code> on every iteration of the loop,
+and thus this might slow down your event loop if you do a lot of loop
+iterations and little real work, but is usually not noticeable (on my
+Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
+without a syscall and thus <i>very</i> fast, but my Linux system also has
+<code>pthread_atfork</code> which is even faster).</p>
+					<p>The big advantage of this flag is that you can forget about fork (and
+forget about forgetting to tell libev about forking) when you use this
+flag.</p>
+					<p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
+environment variable.</p>
 				</dd>
 				<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,
 	<dd>
 		<p>Like <code>ev_default_fork</code>, but acts on an event loop created by
 <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_loop_count (loop)</dt>
+	<dd>
+		<p>Returns the count of loop iterations for the loop, which is identical to
+the number of times libev did poll for new events. It starts at <code>0</code> and
+happily wraps around with enough iterations.</p>
+		<p>This value can sometimes be useful as a generation counter of sorts (it
+&quot;ticks&quot; the number of loop iterations), as it roughly corresponds with
+<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
+	</dd>
 	<dt>unsigned int ev_backend (loop)</dt>
 	<dd>
 		<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
 use.</p>
 	</dd>
 	<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
 	<dd>
 		<p>Change the callback. You can change the callback at virtually any time
 (modulo threads).</p>
 	</dd>
+	<dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
+	<dt>int ev_priority (ev_TYPE *watcher)</dt>
+	<dd>
+		<p>Set and query the priority of the watcher. The priority is a small
+integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
+(default: <code>-2</code>). Pending watchers with higher priority will be invoked
+before watchers with lower priority, but priority will not keep watchers
+from being executed (except for <code>ev_idle</code> watchers).</p>
+		<p>This means that priorities are <i>only</i> used for ordering callback
+invocation after new events have been received. This is useful, for
+example, to reduce latency after idling, or more often, to bind two
+watchers on the same event and make sure one is called first.</p>
+		<p>If you need to suppress invocation when higher priority events are pending
+you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
+		<p>The default priority used by watchers when no priority has been set is
+always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
+		<p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
+fine, as long as you do not mind that the priority value you query might
+or might not have been adjusted to be within valid range.</p>
+	</dd>
 </dl>
 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
+whether 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>
 	<dt>ev_timer_again (loop)</dt>
 	<dd>
 		<p>This will act as if the timer timed out and restart it again if it is
 repeating. The exact semantics are:</p>
+		<p>If the timer is pending, its pending status is cleared.</p>
-		<p>If the timer is started but nonrepeating, stop it.</p>
+		<p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
-		<p>If the timer is repeating, either start it if necessary (with the repeat
+		<p>If the timer is repeating, either start it if necessary (with the
-value), or reset the running timer to the repeat value.</p>
+<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
 		<p>This sounds a bit complicated, but here is a useful and typical
-example: Imagine you have a tcp connection and you want a so-called
+example: Imagine you have a tcp connection and you want a so-called idle
-idle timeout, that is, you want to be called when there have been,
+timeout, that is, you want to be called when there have been, say, 60
-say, 60 seconds of inactivity on the socket. The easiest way to do
+seconds of inactivity on the socket. The easiest way to do this is to
-this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling
+configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
 <code>ev_timer_again</code> each time you successfully read or write some data. If
 you go into an idle state where you do not expect data to travel on the
-socket, you can stop the timer, and again will automatically restart it if
+socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
-need be.</p>
+automatically restart it if need be.</p>
-		<p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether
+		<p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
-and only ever use the <code>repeat</code> value:</p>
+altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
 <pre>   ev_timer_init (timer, callback, 0., 5.);
    ev_timer_again (loop, timer);
    ...
    timer-&gt;again = 17.;
    ev_timer_again (loop, timer);
    ...
    timer-&gt;again = 10.;
    ev_timer_again (loop, timer);
 </pre>
-		<p>This is more efficient then stopping/starting the timer eahc time you want
+		<p>This is more slightly efficient then stopping/starting the timer each time
-to modify its timeout value.</p>
+you want to modify its timeout value.</p>
 	</dd>
 	<dt>ev_tstamp repeat [read-write]</dt>
 	<dd>
 		<p>The current <code>repeat</code> value. Will be used each time the watcher times out
 or <code>ev_timer_again</code> is called and determines the next timeout (if any),
 <p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
 not exist&quot; is a status change like any other. The condition &quot;path does
 not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
 otherwise always forced to be at least one) and all the other fields of
 the stat buffer having unspecified contents.</p>
+<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
+relative and your working directory changes, the behaviour is undefined.</p>
 <p>Since there is no standard to do this, the portable implementation simply
 calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
 can specify a recommended polling interval for this case. If you specify
 a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
 unspecified default</i> value will be used (which you can expect to be around
 </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>
 <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
+<p>Idle watchers trigger events when no other events of the same or higher
-(prepare, check and other idle watchers do not count). That is, as long
+priority are pending (prepare, check and other idle watchers do not
-as your process is busy handling sockets or timeouts (or even signals,
+count).</p>
-imagine) it will not be triggered. But when your process is idle all idle
+<p>That is, as long as your process is busy handling sockets or timeouts
-watchers are being called again and again, once per event loop iteration -
+(or even signals, imagine) of the same or higher priority it will not be
+triggered. But when your process is idle (or only lower-priority watchers
+are pending), the idle watchers are being called once per event loop
-until stopped, that is, or your process receives more events and becomes
+iteration - until stopped, that is, or your process receives more events
-busy.</p>
+and becomes busy again with higher priority stuff.</p>
 <p>The most noteworthy effect is that as long as any idle watchers are
 active, the process will not block when waiting for new events.</p>
 <p>Apart from keeping your process non-blocking (which is a useful
 effect on its own sometimes), idle watchers are a good place to do
 &quot;pseudo-background processing&quot;, or delay processing stuff to after the
   // 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];
+    int timeout = 3600000;
+    struct pollfd fds [nfd];
     // actual code will need to loop here and realloc etc.
     adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
     /* the callback is illegal, but won't be called as we stop during check */
     ev_timer_init (&amp;tw, 0, timeout * 1e-3);
 </div>
 <h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
 <div id="MACRO_MAGIC_CONTENT">
 <p>Libev can be compiled with a variety of options, the most fundemantal is
-<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and
+<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
 callbacks have an initial <code>struct ev_loop *</code> argument.</p>
 <p>To make it easier to write programs that cope with either variant, the
 following macros are defined:</p>
 <dl>
 	<dt><code>EV_A</code>, <code>EV_A_</code></dt>
 	<dd>
 		<p>Similar to the other two macros, this gives you the value of the default
 loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
 	</dd>
 </dl>
-<p>Example: Declare and initialise a check watcher, working regardless of
+<p>Example: Declare and initialise a check watcher, utilising the above
-wether multiple loops are supported or not.</p>
+macros so it will work regardless of whether multiple loops are supported
+or not.</p>
 <pre>  static void
   check_cb (EV_P_ ev_timer *w, int revents)
   {
     ev_check_stop (EV_A_ w);
   }
   ev_check check;
   ev_check_init (&amp;check, check_cb);
   ev_check_start (EV_DEFAULT_ &amp;check);
   ev_loop (EV_DEFAULT_ 0);
 </pre>
 </div>
 <h1 id="EMBEDDING">EMBEDDING</h1>
   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_select.c     only when select backend is enabled (which is enabled 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)
 argument. Instead, all functions act on the single default loop.</p>
 	</dd>
 	<dt>EV_PERIODIC_ENABLE</dt>
 	<dd>
 		<p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
+defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
+code.</p>
+	</dd>
+	<dt>EV_IDLE_ENABLE</dt>
+	<dd>
+		<p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
 defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
 code.</p>
 	</dd>
 	<dt>EV_EMBED_ENABLE</dt>
 	<dd>
 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>
+that everybody includes and which overrides some configure choices:</p>
+<pre>  #define EV_MINIMAL 1
-<pre>  #define EV_USE_POLL 0
+  #define EV_USE_POLL 0
   #define EV_MULTIPLICITY 0
-  #define EV_PERIODICS 0
+  #define EV_PERIODIC_ENABLE 0
+  #define EV_STAT_ENABLE 0
+  #define EV_FORK_ENABLE 0
   #define EV_CONFIG_H &lt;config.h&gt;
+  #define EV_MINPRI 0
+  #define EV_MAXPRI 0
   #include &quot;ev++.h&quot;
 </pre>
 		<p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>

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Comparing libev/ev.html (file contents): Revision 1.57 by root, Wed Nov 28 11:27:29 2007 UTC vs. Revision 1.65 by root, Fri Dec 7 18:09:40 2007 UTC

Diff Legend

Comparing libev/ev.html (file contents):
Revision 1.57 by root, Wed Nov 28 11:27:29 2007 UTC vs.
Revision 1.65 by root, Fri Dec 7 18:09:40 2007 UTC