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

Comparing libev/ev.html (file contents):
Revision 1.6 by root, Mon Nov 12 08:12:14 2007 UTC vs.
Revision 1.9 by root, Mon Nov 12 08:29:11 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="Mon Nov 12 09:12:14 2007" />
+	<meta name="created" content="Mon Nov 12 09:29:10 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 -->
 <p>Libev supports select, poll, the linux-specific epoll and the bsd-specific
 kqueue mechanisms for file descriptor events, relative timers, absolute
 timers with customised rescheduling, signal events, process status change
 events (related to SIGCHLD), and event watchers dealing with the event
 loop mechanism itself (idle, prepare and check watchers). It also is quite
-fast (see a <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it
+fast (see this <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing
-to libevent).</p>
+it to libevent for example).</p>
 </div>
 <h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
 <div id="CONVENTIONS_CONTENT">
 <p>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
 <cite>README.embed</cite> in the libev distribution. If libev was configured without
 support for multiple event loops, then all functions taking an initial
 argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>)
 will not have this argument.</p>
 		<p>You can find out the major and minor version numbers of the library
 you linked against by calling the functions <code>ev_version_major</code> and
 <code>ev_version_minor</code>. If you want, you can compare against the global
 symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
 version of the library your program was compiled against.</p>
-		<p>Usually, its a good idea to terminate if the major versions mismatch,
+		<p>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.</p>
 	</dd>
 	<dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
 	<dd>
 		<p>Sets the allocation function to use (the prototype is similar to the
-realloc function). It is used to allocate and free memory (no surprises
+realloc C function, the semantics are identical). It is used to allocate
-here). If it returns zero when memory needs to be allocated, the library
+and free memory (no surprises here). If it returns zero when memory
-might abort or take some potentially destructive action. The default is
+needs to be allocated, the library might abort or take some potentially
-your system realloc function.</p>
+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>
 	</dd>
 	<dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt>
 	<dd>
 		<p>Set the callback function to call on a retryable syscall error (such
 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).</p>
 	</dd>
 </dl>
 <p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
 types of such loops, the <i>default</i> loop, which supports signals and child
 events, and dynamically created loops which do not.</p>
 <p>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
+create, you also create another event loop. Libev itself does no locking
-whatsoever, so if you mix calls to different event loops, make sure you
+whatsoever, so if you mix calls to the same event loop in different
-lock (this is usually a bad idea, though, even if done right).</p>
+threads, make sure you lock (this is usually a bad idea, though, even if
+done correctly, because it's hideous and inefficient).</p>
 <dl>
 	<dt>struct ev_loop *ev_default_loop (unsigned int flags)</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>
 		<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 0 (or EVFLAG_AUTO).</p>
 		<p>It supports the following flags:</p>
 		<p>
 			<dl>
 				<dt>EVFLAG_AUTO</dt>
 				<dd>
-					<p>The default flags value. Use this if you have no clue (its the right
+					<p>The default flags value. Use this if you have no clue (it's the right
 thing, believe me).</p>
 				</dd>
 				<dt>EVFLAG_NOENV</dt>
 				<dd>
-					<p>If this flag bit is ored into the flag value then libev will <i>not</i> look
+					<p>If this flag bit is ored into the flag value (or the program runs setuid
-at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this
+or setgid) then libev will <i>not</i> look at the environment variable
-environment variable will override the flags completely. This is useful
+<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
+override the flags completely if it is found in the environment. This is
-to try out specific backends to tets their performance, or to work around
+useful to try out specific backends to test their performance, or to work
-bugs.</p>
+around bugs.</p>
 				</dd>
-				<dt>EVMETHOD_SELECT  portable select backend</dt>
+				<dt>EVMETHOD_SELECT  (portable select backend)</dt>
-				<dt>EVMETHOD_POLL    poll backend (everywhere except windows)</dt>
+				<dt>EVMETHOD_POLL    (poll backend, available everywhere except on windows)</dt>
-				<dt>EVMETHOD_EPOLL   linux only</dt>
+				<dt>EVMETHOD_EPOLL   (linux only)</dt>
-				<dt>EVMETHOD_KQUEUE  some bsds only</dt>
+				<dt>EVMETHOD_KQUEUE  (some bsds only)</dt>
-				<dt>EVMETHOD_DEVPOLL solaris 8 only</dt>
+				<dt>EVMETHOD_DEVPOLL (solaris 8 only)</dt>
-				<dt>EVMETHOD_PORT    solaris 10 only</dt>
+				<dt>EVMETHOD_PORT    (solaris 10 only)</dt>
 				<dd>
 					<p>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
 specified, any backend will do.</p>
 				</dd>
 	</dd>
 	<dt>ev_default_destroy ()</dt>
 	<dd>
 		<p>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 :).</p>
+any way whatsoever, although you cannot rely on this :).</p>
 	</dd>
 	<dt>ev_loop_destroy (loop)</dt>
 	<dd>
 		<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
 earlier call to <code>ev_loop_new</code>.</p>
 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>The function itself is quite fast and its usually not a problem to call
+		<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>
 	<dt>unsigned int ev_method (loop)</dt>
 	<dd>
 		<p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in
 use.</p>
 	</dd>
-	<dt>ev_tstamp = ev_now (loop)</dt>
+	<dt>ev_tstamp ev_now (loop)</dt>
 	<dd>
 		<p>Returns the current &quot;event loop time&quot;, which is the time the event loop
 got events and started processing them. This timestamp does not change
 as long as callbacks are being processed, and this is also the base time
 used for relative timers. You can treat it as the timestamp of the event
 events.</p>
 		<p>If the flags argument is specified as 0, it will not return until either
 no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
 		<p>A flags value of <code>EVLOOP_NONBLOCK</code> 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.</p>
+case there are no events and will return after one iteration of the loop.</p>
 		<p>A flags value of <code>EVLOOP_ONESHOT</code> 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.</p>
+your process until at least one new event arrives, and will return after
+one iteration of the loop.</p>
 		<p>This flags value could be used to implement alternative looping
 constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and
 more generic mechanism.</p>
 	</dd>
 	<dt>ev_unloop (loop, how)</dt>
 	<dd>
-		<p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument
+		<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
+has processed all outstanding events). The <code>how</code> argument must be either
-must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code>
+<code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or
-call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code>
+<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
-calls return.</p>
 	</dd>
 	<dt>ev_ref (loop)</dt>
 	<dt>ev_unref (loop)</dt>
 	<dd>
-		<p>Ref/unref can be used to add or remove a refcount on the event loop: Every
+		<p>Ref/unref can be used to add or remove a reference count on the event
-watcher keeps one reference. If you have a long-runing watcher you never
+loop: Every watcher keeps one reference, and as long as the reference
-unregister that should not keep ev_loop from running, ev_unref() after
+count is nonzero, <code>ev_loop</code> will not return on its own. If you have
-starting, and ev_ref() before stopping it. Libev itself uses this for
+a watcher you never unregister that should not keep <code>ev_loop</code> from
-example for its internal signal pipe: It is not visible to you as a user
+returning, ev_unref() after starting, and ev_ref() before stopping it. For
-and should not keep <code>ev_loop</code> from exiting if the work is done. It is
+example, libev itself uses this for its internal signal pipe: It is not
-also an excellent way to do this for generic recurring timers or from
+visible to the libev user and should not keep <code>ev_loop</code> from exiting if
-within third-party libraries. Just remember to unref after start and ref
+no event watchers registered by it are active. It is also an excellent
-before stop.</p>
+way to do this for generic recurring timers or from within third-party
+libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
 	</dd>
 </dl>
 </div>
 <h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
 <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 cna 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 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).</p>
+<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 file/socket etc. description.</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>
 <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 ev_io watcher. The fd is the file descriptor to rceeive
 <p>The timers are based on real time, that is, if you register an event that
 times out after an hour and youreset your system clock to last years
 time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
 detecting time jumps is hard, and soem inaccuracies are unavoidable (the
 monotonic clock option helps a lot here).</p>
+<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
+time. This is usually the right thing as this timestamp refers to the time
+of the event triggering whatever timeout you are modifying/starting.  If
+you suspect event processing to be delayed and you *need* to base the timeout
+ion the current time, use something like this to adjust for this:</p>
+<pre>   ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
+</pre>
 <dl>
 	<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
 	<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
 	<dd>
 		<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
 </div>
 <h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2>
 <div id="ev_signal_signal_me_when_a_signal_ge-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
-will try its best to deliver signals synchronously, i.e. as part of the
+will try it's best to deliver signals synchronously, i.e. as part of the
 normal event processing, like any other event.</p>
 <p>You cna configure as many watchers as you like per signal. Only when the
 first watcher gets started will libev actually register a signal watcher
 with the kernel (thus it coexists with your own signal handlers as long
 as you don't register any with libev). Similarly, when the last signal

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Comparing libev/ev.html (file contents): Revision 1.6 by root, Mon Nov 12 08:12:14 2007 UTC vs. Revision 1.9 by root, Mon Nov 12 08:29:11 2007 UTC

Diff Legend

Comparing libev/ev.html (file contents):
Revision 1.6 by root, Mon Nov 12 08:12:14 2007 UTC vs.
Revision 1.9 by root, Mon Nov 12 08:29:11 2007 UTC