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<title>libev</title> |
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<!-- INDEX START --> |
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<h3 id="TOP">Index</h3> |
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|
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<ul><li><a href="#NAME">NAME</a></li> |
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<li><a href="#SYNOPSIS">SYNOPSIS</a></li> |
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<li><a href="#EXAMPLE_PROGRAM">EXAMPLE PROGRAM</a></li> |
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<li><a href="#DESCRIPTION">DESCRIPTION</a></li> |
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<li><a href="#FEATURES">FEATURES</a></li> |
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<li><a href="#CONVENTIONS">CONVENTIONS</a></li> |
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<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li> |
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<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li> |
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<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li> |
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<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> |
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<ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li> |
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<li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> |
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</ul> |
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</li> |
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<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> |
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<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> |
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<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li> |
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<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li> |
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<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li> |
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<li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li> |
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<li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li> |
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<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> |
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<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> |
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<li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li> |
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<li><a href="#code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</a></li> |
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</ul> |
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</li> |
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<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> |
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<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> |
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<li><a href="#C_SUPPORT">C++ SUPPORT</a></li> |
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<li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li> |
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<li><a href="#EMBEDDING">EMBEDDING</a> |
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<ul><li><a href="#FILESETS">FILESETS</a> |
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<ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li> |
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<li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li> |
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<li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li> |
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</ul> |
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</li> |
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<li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li> |
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<li><a href="#EXAMPLES">EXAMPLES</a></li> |
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</ul> |
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</li> |
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<li><a href="#COMPLEXITIES">COMPLEXITIES</a></li> |
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<li><a href="#AUTHOR">AUTHOR</a> |
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</li> |
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</ul><hr /> |
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<!-- INDEX END --> |
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|
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<h1 id="NAME">NAME</h1> |
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<div id="NAME_CONTENT"> |
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<p>libev - a high performance full-featured event loop written in C</p> |
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|
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</div> |
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<h1 id="SYNOPSIS">SYNOPSIS</h1> |
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<div id="SYNOPSIS_CONTENT"> |
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<pre> #include <ev.h> |
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|
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</pre> |
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|
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</div> |
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<h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1> |
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<div id="EXAMPLE_PROGRAM_CONTENT"> |
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<pre> #include <ev.h> |
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|
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ev_io stdin_watcher; |
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ev_timer timeout_watcher; |
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|
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/* called when data readable on stdin */ |
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static void |
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stdin_cb (EV_P_ struct ev_io *w, int revents) |
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{ |
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/* puts ("stdin ready"); */ |
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ev_io_stop (EV_A_ w); /* just a syntax example */ |
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ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */ |
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} |
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|
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static void |
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timeout_cb (EV_P_ struct ev_timer *w, int revents) |
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{ |
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/* puts ("timeout"); */ |
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ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */ |
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} |
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|
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int |
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main (void) |
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{ |
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struct ev_loop *loop = ev_default_loop (0); |
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|
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/* initialise an io watcher, then start it */ |
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ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
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ev_io_start (loop, &stdin_watcher); |
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|
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/* simple non-repeating 5.5 second timeout */ |
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ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
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ev_timer_start (loop, &timeout_watcher); |
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|
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/* loop till timeout or data ready */ |
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ev_loop (loop, 0); |
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|
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return 0; |
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} |
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|
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</pre> |
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|
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</div> |
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<h1 id="DESCRIPTION">DESCRIPTION</h1> |
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<div id="DESCRIPTION_CONTENT"> |
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<p>Libev is an event loop: you register interest in certain events (such as a |
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file descriptor being readable or a timeout occuring), and it will manage |
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these event sources and provide your program with events.</p> |
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<p>To do this, it must take more or less complete control over your process |
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(or thread) by executing the <i>event loop</i> handler, and will then |
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communicate events via a callback mechanism.</p> |
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<p>You register interest in certain events by registering so-called <i>event |
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watchers</i>, which are relatively small C structures you initialise with the |
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details of the event, and then hand it over to libev by <i>starting</i> the |
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watcher.</p> |
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|
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</div> |
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<h1 id="FEATURES">FEATURES</h1> |
137 |
<div id="FEATURES_CONTENT"> |
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<p>Libev supports <code>select</code>, <code>poll</code>, the linux-specific <code>epoll</code>, the |
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bsd-specific <code>kqueue</code> and the solaris-specific event port mechanisms |
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for file descriptor events (<code>ev_io</code>), relative timers (<code>ev_timer</code>), |
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absolute timers with customised rescheduling (<code>ev_periodic</code>), synchronous |
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signals (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and |
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event watchers dealing with the event loop mechanism itself (<code>ev_idle</code>, |
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<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as |
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file watchers (<code>ev_stat</code>) and even limited support for fork events |
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(<code>ev_fork</code>).</p> |
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<p>It also is quite fast (see this |
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<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent |
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for example).</p> |
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|
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</div> |
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<h1 id="CONVENTIONS">CONVENTIONS</h1> |
153 |
<div id="CONVENTIONS_CONTENT"> |
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<p>Libev is very configurable. In this manual the default configuration will |
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be described, which supports multiple event loops. For more info about |
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various configuration options please have a look at <strong>EMBED</strong> section in |
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this manual. If libev was configured without support for multiple event |
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loops, then all functions taking an initial argument of name <code>loop</code> |
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(which is always of type <code>struct ev_loop *</code>) will not have this argument.</p> |
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|
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</div> |
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<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1> |
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<div id="TIME_REPRESENTATION_CONTENT"> |
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<p>Libev represents time as a single floating point number, representing the |
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(fractional) number of seconds since the (POSIX) epoch (somewhere near |
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the beginning of 1970, details are complicated, don't ask). This type is |
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called <code>ev_tstamp</code>, which is what you should use too. It usually aliases |
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to the <code>double</code> type in C, and when you need to do any calculations on |
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it, you should treat it as such.</p> |
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|
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</div> |
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<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1> |
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<div id="GLOBAL_FUNCTIONS_CONTENT"> |
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<p>These functions can be called anytime, even before initialising the |
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library in any way.</p> |
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<dl> |
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<dt>ev_tstamp ev_time ()</dt> |
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<dd> |
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<p>Returns the current time as libev would use it. Please note that the |
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<code>ev_now</code> function is usually faster and also often returns the timestamp |
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you actually want to know.</p> |
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</dd> |
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<dt>int ev_version_major ()</dt> |
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<dt>int ev_version_minor ()</dt> |
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<dd> |
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<p>You can find out the major and minor version numbers of the library |
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you linked against by calling the functions <code>ev_version_major</code> and |
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<code>ev_version_minor</code>. If you want, you can compare against the global |
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symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the |
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version of the library your program was compiled against.</p> |
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<p>Usually, it's a good idea to terminate if the major versions mismatch, |
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as this indicates an incompatible change. Minor versions are usually |
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compatible to older versions, so a larger minor version alone is usually |
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not a problem.</p> |
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<p>Example: Make sure we haven't accidentally been linked against the wrong |
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version.</p> |
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<pre> assert (("libev version mismatch", |
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ev_version_major () == EV_VERSION_MAJOR |
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&& ev_version_minor () >= EV_VERSION_MINOR)); |
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|
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</pre> |
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</dd> |
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<dt>unsigned int ev_supported_backends ()</dt> |
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<dd> |
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<p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code> |
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value) compiled into this binary of libev (independent of their |
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availability on the system you are running on). See <code>ev_default_loop</code> for |
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a description of the set values.</p> |
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<p>Example: make sure we have the epoll method, because yeah this is cool and |
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a must have and can we have a torrent of it please!!!11</p> |
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<pre> assert (("sorry, no epoll, no sex", |
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ev_supported_backends () & EVBACKEND_EPOLL)); |
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|
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</pre> |
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</dd> |
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<dt>unsigned int ev_recommended_backends ()</dt> |
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<dd> |
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<p>Return the set of all backends compiled into this binary of libev and also |
219 |
recommended for this platform. This set is often smaller than the one |
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returned by <code>ev_supported_backends</code>, as for example kqueue is broken on |
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most BSDs and will not be autodetected unless you explicitly request it |
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(assuming you know what you are doing). This is the set of backends that |
223 |
libev will probe for if you specify no backends explicitly.</p> |
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</dd> |
225 |
<dt>unsigned int ev_embeddable_backends ()</dt> |
226 |
<dd> |
227 |
<p>Returns the set of backends that are embeddable in other event loops. This |
228 |
is the theoretical, all-platform, value. To find which backends |
229 |
might be supported on the current system, you would need to look at |
230 |
<code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for |
231 |
recommended ones.</p> |
232 |
<p>See the description of <code>ev_embed</code> watchers for more info.</p> |
233 |
</dd> |
234 |
<dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt> |
235 |
<dd> |
236 |
<p>Sets the allocation function to use (the prototype and semantics are |
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identical to the realloc C function). It is used to allocate and free |
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memory (no surprises here). If it returns zero when memory needs to be |
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allocated, the library might abort or take some potentially destructive |
240 |
action. The default is your system realloc function.</p> |
241 |
<p>You could override this function in high-availability programs to, say, |
242 |
free some memory if it cannot allocate memory, to use a special allocator, |
243 |
or even to sleep a while and retry until some memory is available.</p> |
244 |
<p>Example: Replace the libev allocator with one that waits a bit and then |
245 |
retries).</p> |
246 |
<pre> static void * |
247 |
persistent_realloc (void *ptr, size_t size) |
248 |
{ |
249 |
for (;;) |
250 |
{ |
251 |
void *newptr = realloc (ptr, size); |
252 |
|
253 |
if (newptr) |
254 |
return newptr; |
255 |
|
256 |
sleep (60); |
257 |
} |
258 |
} |
259 |
|
260 |
... |
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ev_set_allocator (persistent_realloc); |
262 |
|
263 |
</pre> |
264 |
</dd> |
265 |
<dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
266 |
<dd> |
267 |
<p>Set the callback function to call on a retryable syscall error (such |
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as failed select, poll, epoll_wait). The message is a printable string |
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indicating the system call or subsystem causing the problem. If this |
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callback is set, then libev will expect it to remedy the sitution, no |
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matter what, when it returns. That is, libev will generally retry the |
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requested operation, or, if the condition doesn't go away, do bad stuff |
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(such as abort).</p> |
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<p>Example: This is basically the same thing that libev does internally, too.</p> |
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<pre> static void |
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fatal_error (const char *msg) |
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{ |
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perror (msg); |
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abort (); |
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} |
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|
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... |
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ev_set_syserr_cb (fatal_error); |
284 |
|
285 |
</pre> |
286 |
</dd> |
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</dl> |
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|
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</div> |
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<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1> |
291 |
<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> |
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<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two |
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types of such loops, the <i>default</i> loop, which supports signals and child |
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events, and dynamically created loops which do not.</p> |
295 |
<p>If you use threads, a common model is to run the default event loop |
296 |
in your main thread (or in a separate thread) and for each thread you |
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create, you also create another event loop. Libev itself does no locking |
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whatsoever, so if you mix calls to the same event loop in different |
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threads, make sure you lock (this is usually a bad idea, though, even if |
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done correctly, because it's hideous and inefficient).</p> |
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<dl> |
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<dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> |
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<dd> |
304 |
<p>This will initialise the default event loop if it hasn't been initialised |
305 |
yet and return it. If the default loop could not be initialised, returns |
306 |
false. If it already was initialised it simply returns it (and ignores the |
307 |
flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p> |
308 |
<p>If you don't know what event loop to use, use the one returned from this |
309 |
function.</p> |
310 |
<p>The flags argument can be used to specify special behaviour or specific |
311 |
backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p> |
312 |
<p>The following flags are supported:</p> |
313 |
<p> |
314 |
<dl> |
315 |
<dt><code>EVFLAG_AUTO</code></dt> |
316 |
<dd> |
317 |
<p>The default flags value. Use this if you have no clue (it's the right |
318 |
thing, believe me).</p> |
319 |
</dd> |
320 |
<dt><code>EVFLAG_NOENV</code></dt> |
321 |
<dd> |
322 |
<p>If this flag bit is ored into the flag value (or the program runs setuid |
323 |
or setgid) then libev will <i>not</i> look at the environment variable |
324 |
<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
325 |
override the flags completely if it is found in the environment. This is |
326 |
useful to try out specific backends to test their performance, or to work |
327 |
around bugs.</p> |
328 |
</dd> |
329 |
<dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> |
330 |
<dd> |
331 |
<p>This is your standard select(2) backend. Not <i>completely</i> standard, as |
332 |
libev tries to roll its own fd_set with no limits on the number of fds, |
333 |
but if that fails, expect a fairly low limit on the number of fds when |
334 |
using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
335 |
the fastest backend for a low number of fds.</p> |
336 |
</dd> |
337 |
<dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt> |
338 |
<dd> |
339 |
<p>And this is your standard poll(2) backend. It's more complicated than |
340 |
select, but handles sparse fds better and has no artificial limit on the |
341 |
number of fds you can use (except it will slow down considerably with a |
342 |
lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p> |
343 |
</dd> |
344 |
<dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt> |
345 |
<dd> |
346 |
<p>For few fds, this backend is a bit little slower than poll and select, |
347 |
but it scales phenomenally better. While poll and select usually scale like |
348 |
O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
349 |
either O(1) or O(active_fds).</p> |
350 |
<p>While stopping and starting an I/O watcher in the same iteration will |
351 |
result in some caching, there is still a syscall per such incident |
352 |
(because the fd could point to a different file description now), so its |
353 |
best to avoid that. Also, dup()ed file descriptors might not work very |
354 |
well if you register events for both fds.</p> |
355 |
<p>Please note that epoll sometimes generates spurious notifications, so you |
356 |
need to use non-blocking I/O or other means to avoid blocking when no data |
357 |
(or space) is available.</p> |
358 |
</dd> |
359 |
<dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt> |
360 |
<dd> |
361 |
<p>Kqueue deserves special mention, as at the time of this writing, it |
362 |
was broken on all BSDs except NetBSD (usually it doesn't work with |
363 |
anything but sockets and pipes, except on Darwin, where of course its |
364 |
completely useless). For this reason its not being "autodetected" |
365 |
unless you explicitly specify it explicitly in the flags (i.e. using |
366 |
<code>EVBACKEND_KQUEUE</code>).</p> |
367 |
<p>It scales in the same way as the epoll backend, but the interface to the |
368 |
kernel is more efficient (which says nothing about its actual speed, of |
369 |
course). While starting and stopping an I/O watcher does not cause an |
370 |
extra syscall as with epoll, it still adds up to four event changes per |
371 |
incident, so its best to avoid that.</p> |
372 |
</dd> |
373 |
<dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt> |
374 |
<dd> |
375 |
<p>This is not implemented yet (and might never be).</p> |
376 |
</dd> |
377 |
<dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt> |
378 |
<dd> |
379 |
<p>This uses the Solaris 10 port mechanism. As with everything on Solaris, |
380 |
it's really slow, but it still scales very well (O(active_fds)).</p> |
381 |
<p>Please note that solaris ports can result in a lot of spurious |
382 |
notifications, so you need to use non-blocking I/O or other means to avoid |
383 |
blocking when no data (or space) is available.</p> |
384 |
</dd> |
385 |
<dt><code>EVBACKEND_ALL</code></dt> |
386 |
<dd> |
387 |
<p>Try all backends (even potentially broken ones that wouldn't be tried |
388 |
with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as |
389 |
<code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p> |
390 |
</dd> |
391 |
</dl> |
392 |
</p> |
393 |
<p>If one or more of these are ored into the flags value, then only these |
394 |
backends will be tried (in the reverse order as given here). If none are |
395 |
specified, most compiled-in backend will be tried, usually in reverse |
396 |
order of their flag values :)</p> |
397 |
<p>The most typical usage is like this:</p> |
398 |
<pre> if (!ev_default_loop (0)) |
399 |
fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
400 |
|
401 |
</pre> |
402 |
<p>Restrict libev to the select and poll backends, and do not allow |
403 |
environment settings to be taken into account:</p> |
404 |
<pre> ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
405 |
|
406 |
</pre> |
407 |
<p>Use whatever libev has to offer, but make sure that kqueue is used if |
408 |
available (warning, breaks stuff, best use only with your own private |
409 |
event loop and only if you know the OS supports your types of fds):</p> |
410 |
<pre> ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
411 |
|
412 |
</pre> |
413 |
</dd> |
414 |
<dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> |
415 |
<dd> |
416 |
<p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
417 |
always distinct from the default loop. Unlike the default loop, it cannot |
418 |
handle signal and child watchers, and attempts to do so will be greeted by |
419 |
undefined behaviour (or a failed assertion if assertions are enabled).</p> |
420 |
<p>Example: Try to create a event loop that uses epoll and nothing else.</p> |
421 |
<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
422 |
if (!epoller) |
423 |
fatal ("no epoll found here, maybe it hides under your chair"); |
424 |
|
425 |
</pre> |
426 |
</dd> |
427 |
<dt>ev_default_destroy ()</dt> |
428 |
<dd> |
429 |
<p>Destroys the default loop again (frees all memory and kernel state |
430 |
etc.). None of the active event watchers will be stopped in the normal |
431 |
sense, so e.g. <code>ev_is_active</code> might still return true. It is your |
432 |
responsibility to either stop all watchers cleanly yoursef <i>before</i> |
433 |
calling this function, or cope with the fact afterwards (which is usually |
434 |
the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them |
435 |
for example).</p> |
436 |
</dd> |
437 |
<dt>ev_loop_destroy (loop)</dt> |
438 |
<dd> |
439 |
<p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an |
440 |
earlier call to <code>ev_loop_new</code>.</p> |
441 |
</dd> |
442 |
<dt>ev_default_fork ()</dt> |
443 |
<dd> |
444 |
<p>This function reinitialises the kernel state for backends that have |
445 |
one. Despite the name, you can call it anytime, but it makes most sense |
446 |
after forking, in either the parent or child process (or both, but that |
447 |
again makes little sense).</p> |
448 |
<p>You <i>must</i> call this function in the child process after forking if and |
449 |
only if you want to use the event library in both processes. If you just |
450 |
fork+exec, you don't have to call it.</p> |
451 |
<p>The function itself is quite fast and it's usually not a problem to call |
452 |
it just in case after a fork. To make this easy, the function will fit in |
453 |
quite nicely into a call to <code>pthread_atfork</code>:</p> |
454 |
<pre> pthread_atfork (0, 0, ev_default_fork); |
455 |
|
456 |
</pre> |
457 |
<p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use |
458 |
without calling this function, so if you force one of those backends you |
459 |
do not need to care.</p> |
460 |
</dd> |
461 |
<dt>ev_loop_fork (loop)</dt> |
462 |
<dd> |
463 |
<p>Like <code>ev_default_fork</code>, but acts on an event loop created by |
464 |
<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop |
465 |
after fork, and how you do this is entirely your own problem.</p> |
466 |
</dd> |
467 |
<dt>unsigned int ev_backend (loop)</dt> |
468 |
<dd> |
469 |
<p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in |
470 |
use.</p> |
471 |
</dd> |
472 |
<dt>ev_tstamp ev_now (loop)</dt> |
473 |
<dd> |
474 |
<p>Returns the current "event loop time", which is the time the event loop |
475 |
received events and started processing them. This timestamp does not |
476 |
change as long as callbacks are being processed, and this is also the base |
477 |
time used for relative timers. You can treat it as the timestamp of the |
478 |
event occuring (or more correctly, libev finding out about it).</p> |
479 |
</dd> |
480 |
<dt>ev_loop (loop, int flags)</dt> |
481 |
<dd> |
482 |
<p>Finally, this is it, the event handler. This function usually is called |
483 |
after you initialised all your watchers and you want to start handling |
484 |
events.</p> |
485 |
<p>If the flags argument is specified as <code>0</code>, it will not return until |
486 |
either no event watchers are active anymore or <code>ev_unloop</code> was called.</p> |
487 |
<p>Please note that an explicit <code>ev_unloop</code> is usually better than |
488 |
relying on all watchers to be stopped when deciding when a program has |
489 |
finished (especially in interactive programs), but having a program that |
490 |
automatically loops as long as it has to and no longer by virtue of |
491 |
relying on its watchers stopping correctly is a thing of beauty.</p> |
492 |
<p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle |
493 |
those events and any outstanding ones, but will not block your process in |
494 |
case there are no events and will return after one iteration of the loop.</p> |
495 |
<p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if |
496 |
neccessary) and will handle those and any outstanding ones. It will block |
497 |
your process until at least one new event arrives, and will return after |
498 |
one iteration of the loop. This is useful if you are waiting for some |
499 |
external event in conjunction with something not expressible using other |
500 |
libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is |
501 |
usually a better approach for this kind of thing.</p> |
502 |
<p>Here are the gory details of what <code>ev_loop</code> does:</p> |
503 |
<pre> * If there are no active watchers (reference count is zero), return. |
504 |
- Queue prepare watchers and then call all outstanding watchers. |
505 |
- If we have been forked, recreate the kernel state. |
506 |
- Update the kernel state with all outstanding changes. |
507 |
- Update the "event loop time". |
508 |
- Calculate for how long to block. |
509 |
- Block the process, waiting for any events. |
510 |
- Queue all outstanding I/O (fd) events. |
511 |
- Update the "event loop time" and do time jump handling. |
512 |
- Queue all outstanding timers. |
513 |
- Queue all outstanding periodics. |
514 |
- If no events are pending now, queue all idle watchers. |
515 |
- Queue all check watchers. |
516 |
- Call all queued watchers in reverse order (i.e. check watchers first). |
517 |
Signals and child watchers are implemented as I/O watchers, and will |
518 |
be handled here by queueing them when their watcher gets executed. |
519 |
- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
520 |
were used, return, otherwise continue with step *. |
521 |
|
522 |
</pre> |
523 |
<p>Example: Queue some jobs and then loop until no events are outsanding |
524 |
anymore.</p> |
525 |
<pre> ... queue jobs here, make sure they register event watchers as long |
526 |
... as they still have work to do (even an idle watcher will do..) |
527 |
ev_loop (my_loop, 0); |
528 |
... jobs done. yeah! |
529 |
|
530 |
</pre> |
531 |
</dd> |
532 |
<dt>ev_unloop (loop, how)</dt> |
533 |
<dd> |
534 |
<p>Can be used to make a call to <code>ev_loop</code> return early (but only after it |
535 |
has processed all outstanding events). The <code>how</code> argument must be either |
536 |
<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or |
537 |
<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> |
538 |
</dd> |
539 |
<dt>ev_ref (loop)</dt> |
540 |
<dt>ev_unref (loop)</dt> |
541 |
<dd> |
542 |
<p>Ref/unref can be used to add or remove a reference count on the event |
543 |
loop: Every watcher keeps one reference, and as long as the reference |
544 |
count is nonzero, <code>ev_loop</code> will not return on its own. If you have |
545 |
a watcher you never unregister that should not keep <code>ev_loop</code> from |
546 |
returning, ev_unref() after starting, and ev_ref() before stopping it. For |
547 |
example, libev itself uses this for its internal signal pipe: It is not |
548 |
visible to the libev user and should not keep <code>ev_loop</code> from exiting if |
549 |
no event watchers registered by it are active. It is also an excellent |
550 |
way to do this for generic recurring timers or from within third-party |
551 |
libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> |
552 |
<p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code> |
553 |
running when nothing else is active.</p> |
554 |
<pre> struct ev_signal exitsig; |
555 |
ev_signal_init (&exitsig, sig_cb, SIGINT); |
556 |
ev_signal_start (loop, &exitsig); |
557 |
evf_unref (loop); |
558 |
|
559 |
</pre> |
560 |
<p>Example: For some weird reason, unregister the above signal handler again.</p> |
561 |
<pre> ev_ref (loop); |
562 |
ev_signal_stop (loop, &exitsig); |
563 |
|
564 |
</pre> |
565 |
</dd> |
566 |
</dl> |
567 |
|
568 |
|
569 |
|
570 |
|
571 |
|
572 |
</div> |
573 |
<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1> |
574 |
<div id="ANATOMY_OF_A_WATCHER_CONTENT"> |
575 |
<p>A watcher is a structure that you create and register to record your |
576 |
interest in some event. For instance, if you want to wait for STDIN to |
577 |
become readable, you would create an <code>ev_io</code> watcher for that:</p> |
578 |
<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
579 |
{ |
580 |
ev_io_stop (w); |
581 |
ev_unloop (loop, EVUNLOOP_ALL); |
582 |
} |
583 |
|
584 |
struct ev_loop *loop = ev_default_loop (0); |
585 |
struct ev_io stdin_watcher; |
586 |
ev_init (&stdin_watcher, my_cb); |
587 |
ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
588 |
ev_io_start (loop, &stdin_watcher); |
589 |
ev_loop (loop, 0); |
590 |
|
591 |
</pre> |
592 |
<p>As you can see, you are responsible for allocating the memory for your |
593 |
watcher structures (and it is usually a bad idea to do this on the stack, |
594 |
although this can sometimes be quite valid).</p> |
595 |
<p>Each watcher structure must be initialised by a call to <code>ev_init |
596 |
(watcher *, callback)</code>, which expects a callback to be provided. This |
597 |
callback gets invoked each time the event occurs (or, in the case of io |
598 |
watchers, each time the event loop detects that the file descriptor given |
599 |
is readable and/or writable).</p> |
600 |
<p>Each watcher type has its own <code>ev_<type>_set (watcher *, ...)</code> macro |
601 |
with arguments specific to this watcher type. There is also a macro |
602 |
to combine initialisation and setting in one call: <code>ev_<type>_init |
603 |
(watcher *, callback, ...)</code>.</p> |
604 |
<p>To make the watcher actually watch out for events, you have to start it |
605 |
with a watcher-specific start function (<code>ev_<type>_start (loop, watcher |
606 |
*)</code>), and you can stop watching for events at any time by calling the |
607 |
corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p> |
608 |
<p>As long as your watcher is active (has been started but not stopped) you |
609 |
must not touch the values stored in it. Most specifically you must never |
610 |
reinitialise it or call its <code>set</code> macro.</p> |
611 |
<p>Each and every callback receives the event loop pointer as first, the |
612 |
registered watcher structure as second, and a bitset of received events as |
613 |
third argument.</p> |
614 |
<p>The received events usually include a single bit per event type received |
615 |
(you can receive multiple events at the same time). The possible bit masks |
616 |
are:</p> |
617 |
<dl> |
618 |
<dt><code>EV_READ</code></dt> |
619 |
<dt><code>EV_WRITE</code></dt> |
620 |
<dd> |
621 |
<p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or |
622 |
writable.</p> |
623 |
</dd> |
624 |
<dt><code>EV_TIMEOUT</code></dt> |
625 |
<dd> |
626 |
<p>The <code>ev_timer</code> watcher has timed out.</p> |
627 |
</dd> |
628 |
<dt><code>EV_PERIODIC</code></dt> |
629 |
<dd> |
630 |
<p>The <code>ev_periodic</code> watcher has timed out.</p> |
631 |
</dd> |
632 |
<dt><code>EV_SIGNAL</code></dt> |
633 |
<dd> |
634 |
<p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p> |
635 |
</dd> |
636 |
<dt><code>EV_CHILD</code></dt> |
637 |
<dd> |
638 |
<p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> |
639 |
</dd> |
640 |
<dt><code>EV_STAT</code></dt> |
641 |
<dd> |
642 |
<p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p> |
643 |
</dd> |
644 |
<dt><code>EV_IDLE</code></dt> |
645 |
<dd> |
646 |
<p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> |
647 |
</dd> |
648 |
<dt><code>EV_PREPARE</code></dt> |
649 |
<dt><code>EV_CHECK</code></dt> |
650 |
<dd> |
651 |
<p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts |
652 |
to gather new events, and all <code>ev_check</code> watchers are invoked just after |
653 |
<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any |
654 |
received events. Callbacks of both watcher types can start and stop as |
655 |
many watchers as they want, and all of them will be taken into account |
656 |
(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep |
657 |
<code>ev_loop</code> from blocking).</p> |
658 |
</dd> |
659 |
<dt><code>EV_EMBED</code></dt> |
660 |
<dd> |
661 |
<p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p> |
662 |
</dd> |
663 |
<dt><code>EV_FORK</code></dt> |
664 |
<dd> |
665 |
<p>The event loop has been resumed in the child process after fork (see |
666 |
<code>ev_fork</code>).</p> |
667 |
</dd> |
668 |
<dt><code>EV_ERROR</code></dt> |
669 |
<dd> |
670 |
<p>An unspecified error has occured, the watcher has been stopped. This might |
671 |
happen because the watcher could not be properly started because libev |
672 |
ran out of memory, a file descriptor was found to be closed or any other |
673 |
problem. You best act on it by reporting the problem and somehow coping |
674 |
with the watcher being stopped.</p> |
675 |
<p>Libev will usually signal a few "dummy" events together with an error, |
676 |
for example it might indicate that a fd is readable or writable, and if |
677 |
your callbacks is well-written it can just attempt the operation and cope |
678 |
with the error from read() or write(). This will not work in multithreaded |
679 |
programs, though, so beware.</p> |
680 |
</dd> |
681 |
</dl> |
682 |
|
683 |
</div> |
684 |
<h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2> |
685 |
<div id="GENERIC_WATCHER_FUNCTIONS_CONTENT"> |
686 |
<p>In the following description, <code>TYPE</code> stands for the watcher type, |
687 |
e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p> |
688 |
<dl> |
689 |
<dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt> |
690 |
<dd> |
691 |
<p>This macro initialises the generic portion of a watcher. The contents |
692 |
of the watcher object can be arbitrary (so <code>malloc</code> will do). Only |
693 |
the generic parts of the watcher are initialised, you <i>need</i> to call |
694 |
the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the |
695 |
type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro |
696 |
which rolls both calls into one.</p> |
697 |
<p>You can reinitialise a watcher at any time as long as it has been stopped |
698 |
(or never started) and there are no pending events outstanding.</p> |
699 |
<p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher, |
700 |
int revents)</code>.</p> |
701 |
</dd> |
702 |
<dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt> |
703 |
<dd> |
704 |
<p>This macro initialises the type-specific parts of a watcher. You need to |
705 |
call <code>ev_init</code> at least once before you call this macro, but you can |
706 |
call <code>ev_TYPE_set</code> any number of times. You must not, however, call this |
707 |
macro on a watcher that is active (it can be pending, however, which is a |
708 |
difference to the <code>ev_init</code> macro).</p> |
709 |
<p>Although some watcher types do not have type-specific arguments |
710 |
(e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p> |
711 |
</dd> |
712 |
<dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt> |
713 |
<dd> |
714 |
<p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro |
715 |
calls into a single call. This is the most convinient method to initialise |
716 |
a watcher. The same limitations apply, of course.</p> |
717 |
</dd> |
718 |
<dt><code>ev_TYPE_start</code> (loop *, ev_TYPE *watcher)</dt> |
719 |
<dd> |
720 |
<p>Starts (activates) the given watcher. Only active watchers will receive |
721 |
events. If the watcher is already active nothing will happen.</p> |
722 |
</dd> |
723 |
<dt><code>ev_TYPE_stop</code> (loop *, ev_TYPE *watcher)</dt> |
724 |
<dd> |
725 |
<p>Stops the given watcher again (if active) and clears the pending |
726 |
status. It is possible that stopped watchers are pending (for example, |
727 |
non-repeating timers are being stopped when they become pending), but |
728 |
<code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If |
729 |
you want to free or reuse the memory used by the watcher it is therefore a |
730 |
good idea to always call its <code>ev_TYPE_stop</code> function.</p> |
731 |
</dd> |
732 |
<dt>bool ev_is_active (ev_TYPE *watcher)</dt> |
733 |
<dd> |
734 |
<p>Returns a true value iff the watcher is active (i.e. it has been started |
735 |
and not yet been stopped). As long as a watcher is active you must not modify |
736 |
it.</p> |
737 |
</dd> |
738 |
<dt>bool ev_is_pending (ev_TYPE *watcher)</dt> |
739 |
<dd> |
740 |
<p>Returns a true value iff the watcher is pending, (i.e. it has outstanding |
741 |
events but its callback has not yet been invoked). As long as a watcher |
742 |
is pending (but not active) you must not call an init function on it (but |
743 |
<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to |
744 |
libev (e.g. you cnanot <code>free ()</code> it).</p> |
745 |
</dd> |
746 |
<dt>callback ev_cb (ev_TYPE *watcher)</dt> |
747 |
<dd> |
748 |
<p>Returns the callback currently set on the watcher.</p> |
749 |
</dd> |
750 |
<dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> |
751 |
<dd> |
752 |
<p>Change the callback. You can change the callback at virtually any time |
753 |
(modulo threads).</p> |
754 |
</dd> |
755 |
</dl> |
756 |
|
757 |
|
758 |
|
759 |
|
760 |
|
761 |
</div> |
762 |
<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> |
763 |
<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> |
764 |
<p>Each watcher has, by default, a member <code>void *data</code> that you can change |
765 |
and read at any time, libev will completely ignore it. This can be used |
766 |
to associate arbitrary data with your watcher. If you need more data and |
767 |
don't want to allocate memory and store a pointer to it in that data |
768 |
member, you can also "subclass" the watcher type and provide your own |
769 |
data:</p> |
770 |
<pre> struct my_io |
771 |
{ |
772 |
struct ev_io io; |
773 |
int otherfd; |
774 |
void *somedata; |
775 |
struct whatever *mostinteresting; |
776 |
} |
777 |
|
778 |
</pre> |
779 |
<p>And since your callback will be called with a pointer to the watcher, you |
780 |
can cast it back to your own type:</p> |
781 |
<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
782 |
{ |
783 |
struct my_io *w = (struct my_io *)w_; |
784 |
... |
785 |
} |
786 |
|
787 |
</pre> |
788 |
<p>More interesting and less C-conformant ways of casting your callback type |
789 |
instead have been omitted.</p> |
790 |
<p>Another common scenario is having some data structure with multiple |
791 |
watchers:</p> |
792 |
<pre> struct my_biggy |
793 |
{ |
794 |
int some_data; |
795 |
ev_timer t1; |
796 |
ev_timer t2; |
797 |
} |
798 |
|
799 |
</pre> |
800 |
<p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated, |
801 |
you need to use <code>offsetof</code>:</p> |
802 |
<pre> #include <stddef.h> |
803 |
|
804 |
static void |
805 |
t1_cb (EV_P_ struct ev_timer *w, int revents) |
806 |
{ |
807 |
struct my_biggy big = (struct my_biggy * |
808 |
(((char *)w) - offsetof (struct my_biggy, t1)); |
809 |
} |
810 |
|
811 |
static void |
812 |
t2_cb (EV_P_ struct ev_timer *w, int revents) |
813 |
{ |
814 |
struct my_biggy big = (struct my_biggy * |
815 |
(((char *)w) - offsetof (struct my_biggy, t2)); |
816 |
} |
817 |
|
818 |
|
819 |
|
820 |
|
821 |
</pre> |
822 |
|
823 |
</div> |
824 |
<h1 id="WATCHER_TYPES">WATCHER TYPES</h1> |
825 |
<div id="WATCHER_TYPES_CONTENT"> |
826 |
<p>This section describes each watcher in detail, but will not repeat |
827 |
information given in the last section. Any initialisation/set macros, |
828 |
functions and members specific to the watcher type are explained.</p> |
829 |
<p>Members are additionally marked with either <i>[read-only]</i>, meaning that, |
830 |
while the watcher is active, you can look at the member and expect some |
831 |
sensible content, but you must not modify it (you can modify it while the |
832 |
watcher is stopped to your hearts content), or <i>[read-write]</i>, which |
833 |
means you can expect it to have some sensible content while the watcher |
834 |
is active, but you can also modify it. Modifying it may not do something |
835 |
sensible or take immediate effect (or do anything at all), but libev will |
836 |
not crash or malfunction in any way.</p> |
837 |
|
838 |
|
839 |
|
840 |
|
841 |
|
842 |
</div> |
843 |
<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2> |
844 |
<div id="code_ev_io_code_is_this_file_descrip-2"> |
845 |
<p>I/O watchers check whether a file descriptor is readable or writable |
846 |
in each iteration of the event loop, or, more precisely, when reading |
847 |
would not block the process and writing would at least be able to write |
848 |
some data. This behaviour is called level-triggering because you keep |
849 |
receiving events as long as the condition persists. Remember you can stop |
850 |
the watcher if you don't want to act on the event and neither want to |
851 |
receive future events.</p> |
852 |
<p>In general you can register as many read and/or write event watchers per |
853 |
fd as you want (as long as you don't confuse yourself). Setting all file |
854 |
descriptors to non-blocking mode is also usually a good idea (but not |
855 |
required if you know what you are doing).</p> |
856 |
<p>You have to be careful with dup'ed file descriptors, though. Some backends |
857 |
(the linux epoll backend is a notable example) cannot handle dup'ed file |
858 |
descriptors correctly if you register interest in two or more fds pointing |
859 |
to the same underlying file/socket/etc. description (that is, they share |
860 |
the same underlying "file open").</p> |
861 |
<p>If you must do this, then force the use of a known-to-be-good backend |
862 |
(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and |
863 |
<code>EVBACKEND_POLL</code>).</p> |
864 |
<p>Another thing you have to watch out for is that it is quite easy to |
865 |
receive "spurious" readyness notifications, that is your callback might |
866 |
be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block |
867 |
because there is no data. Not only are some backends known to create a |
868 |
lot of those (for example solaris ports), it is very easy to get into |
869 |
this situation even with a relatively standard program structure. Thus |
870 |
it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning |
871 |
<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> |
872 |
<p>If you cannot run the fd in non-blocking mode (for example you should not |
873 |
play around with an Xlib connection), then you have to seperately re-test |
874 |
wether a file descriptor is really ready with a known-to-be good interface |
875 |
such as poll (fortunately in our Xlib example, Xlib already does this on |
876 |
its own, so its quite safe to use).</p> |
877 |
<dl> |
878 |
<dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
879 |
<dt>ev_io_set (ev_io *, int fd, int events)</dt> |
880 |
<dd> |
881 |
<p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to |
882 |
rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or |
883 |
<code>EV_READ | EV_WRITE</code> to receive the given events.</p> |
884 |
</dd> |
885 |
<dt>int fd [read-only]</dt> |
886 |
<dd> |
887 |
<p>The file descriptor being watched.</p> |
888 |
</dd> |
889 |
<dt>int events [read-only]</dt> |
890 |
<dd> |
891 |
<p>The events being watched.</p> |
892 |
</dd> |
893 |
</dl> |
894 |
<p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well |
895 |
readable, but only once. Since it is likely line-buffered, you could |
896 |
attempt to read a whole line in the callback.</p> |
897 |
<pre> static void |
898 |
stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
899 |
{ |
900 |
ev_io_stop (loop, w); |
901 |
.. read from stdin here (or from w->fd) and haqndle any I/O errors |
902 |
} |
903 |
|
904 |
... |
905 |
struct ev_loop *loop = ev_default_init (0); |
906 |
struct ev_io stdin_readable; |
907 |
ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
908 |
ev_io_start (loop, &stdin_readable); |
909 |
ev_loop (loop, 0); |
910 |
|
911 |
|
912 |
|
913 |
|
914 |
</pre> |
915 |
|
916 |
</div> |
917 |
<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2> |
918 |
<div id="code_ev_timer_code_relative_and_opti-2"> |
919 |
<p>Timer watchers are simple relative timers that generate an event after a |
920 |
given time, and optionally repeating in regular intervals after that.</p> |
921 |
<p>The timers are based on real time, that is, if you register an event that |
922 |
times out after an hour and you reset your system clock to last years |
923 |
time, it will still time out after (roughly) and hour. "Roughly" because |
924 |
detecting time jumps is hard, and some inaccuracies are unavoidable (the |
925 |
monotonic clock option helps a lot here).</p> |
926 |
<p>The relative timeouts are calculated relative to the <code>ev_now ()</code> |
927 |
time. This is usually the right thing as this timestamp refers to the time |
928 |
of the event triggering whatever timeout you are modifying/starting. If |
929 |
you suspect event processing to be delayed and you <i>need</i> to base the timeout |
930 |
on the current time, use something like this to adjust for this:</p> |
931 |
<pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
932 |
|
933 |
</pre> |
934 |
<p>The callback is guarenteed to be invoked only when its timeout has passed, |
935 |
but if multiple timers become ready during the same loop iteration then |
936 |
order of execution is undefined.</p> |
937 |
<dl> |
938 |
<dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> |
939 |
<dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> |
940 |
<dd> |
941 |
<p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is |
942 |
<code>0.</code>, then it will automatically be stopped. If it is positive, then the |
943 |
timer will automatically be configured to trigger again <code>repeat</code> seconds |
944 |
later, again, and again, until stopped manually.</p> |
945 |
<p>The timer itself will do a best-effort at avoiding drift, that is, if you |
946 |
configure a timer to trigger every 10 seconds, then it will trigger at |
947 |
exactly 10 second intervals. If, however, your program cannot keep up with |
948 |
the timer (because it takes longer than those 10 seconds to do stuff) the |
949 |
timer will not fire more than once per event loop iteration.</p> |
950 |
</dd> |
951 |
<dt>ev_timer_again (loop)</dt> |
952 |
<dd> |
953 |
<p>This will act as if the timer timed out and restart it again if it is |
954 |
repeating. The exact semantics are:</p> |
955 |
<p>If the timer is started but nonrepeating, stop it.</p> |
956 |
<p>If the timer is repeating, either start it if necessary (with the repeat |
957 |
value), or reset the running timer to the repeat value.</p> |
958 |
<p>This sounds a bit complicated, but here is a useful and typical |
959 |
example: Imagine you have a tcp connection and you want a so-called |
960 |
idle timeout, that is, you want to be called when there have been, |
961 |
say, 60 seconds of inactivity on the socket. The easiest way to do |
962 |
this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling |
963 |
<code>ev_timer_again</code> each time you successfully read or write some data. If |
964 |
you go into an idle state where you do not expect data to travel on the |
965 |
socket, you can stop the timer, and again will automatically restart it if |
966 |
need be.</p> |
967 |
<p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether |
968 |
and only ever use the <code>repeat</code> value:</p> |
969 |
<pre> ev_timer_init (timer, callback, 0., 5.); |
970 |
ev_timer_again (loop, timer); |
971 |
... |
972 |
timer->again = 17.; |
973 |
ev_timer_again (loop, timer); |
974 |
... |
975 |
timer->again = 10.; |
976 |
ev_timer_again (loop, timer); |
977 |
|
978 |
</pre> |
979 |
<p>This is more efficient then stopping/starting the timer eahc time you want |
980 |
to modify its timeout value.</p> |
981 |
</dd> |
982 |
<dt>ev_tstamp repeat [read-write]</dt> |
983 |
<dd> |
984 |
<p>The current <code>repeat</code> value. Will be used each time the watcher times out |
985 |
or <code>ev_timer_again</code> is called and determines the next timeout (if any), |
986 |
which is also when any modifications are taken into account.</p> |
987 |
</dd> |
988 |
</dl> |
989 |
<p>Example: Create a timer that fires after 60 seconds.</p> |
990 |
<pre> static void |
991 |
one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
992 |
{ |
993 |
.. one minute over, w is actually stopped right here |
994 |
} |
995 |
|
996 |
struct ev_timer mytimer; |
997 |
ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
998 |
ev_timer_start (loop, &mytimer); |
999 |
|
1000 |
</pre> |
1001 |
<p>Example: Create a timeout timer that times out after 10 seconds of |
1002 |
inactivity.</p> |
1003 |
<pre> static void |
1004 |
timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1005 |
{ |
1006 |
.. ten seconds without any activity |
1007 |
} |
1008 |
|
1009 |
struct ev_timer mytimer; |
1010 |
ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1011 |
ev_timer_again (&mytimer); /* start timer */ |
1012 |
ev_loop (loop, 0); |
1013 |
|
1014 |
// and in some piece of code that gets executed on any "activity": |
1015 |
// reset the timeout to start ticking again at 10 seconds |
1016 |
ev_timer_again (&mytimer); |
1017 |
|
1018 |
|
1019 |
|
1020 |
|
1021 |
</pre> |
1022 |
|
1023 |
</div> |
1024 |
<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2> |
1025 |
<div id="code_ev_periodic_code_to_cron_or_not-2"> |
1026 |
<p>Periodic watchers are also timers of a kind, but they are very versatile |
1027 |
(and unfortunately a bit complex).</p> |
1028 |
<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) |
1029 |
but on wallclock time (absolute time). You can tell a periodic watcher |
1030 |
to trigger "at" some specific point in time. For example, if you tell a |
1031 |
periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () |
1032 |
+ 10.</code>) and then reset your system clock to the last year, then it will |
1033 |
take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
1034 |
roughly 10 seconds later and of course not if you reset your system time |
1035 |
again).</p> |
1036 |
<p>They can also be used to implement vastly more complex timers, such as |
1037 |
triggering an event on eahc midnight, local time.</p> |
1038 |
<p>As with timers, the callback is guarenteed to be invoked only when the |
1039 |
time (<code>at</code>) has been passed, but if multiple periodic timers become ready |
1040 |
during the same loop iteration then order of execution is undefined.</p> |
1041 |
<dl> |
1042 |
<dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
1043 |
<dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> |
1044 |
<dd> |
1045 |
<p>Lots of arguments, lets sort it out... There are basically three modes of |
1046 |
operation, and we will explain them from simplest to complex:</p> |
1047 |
<p> |
1048 |
<dl> |
1049 |
<dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
1050 |
<dd> |
1051 |
<p>In this configuration the watcher triggers an event at the wallclock time |
1052 |
<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, |
1053 |
that is, if it is to be run at January 1st 2011 then it will run when the |
1054 |
system time reaches or surpasses this time.</p> |
1055 |
</dd> |
1056 |
<dt>* non-repeating interval timer (interval > 0, reschedule_cb = 0)</dt> |
1057 |
<dd> |
1058 |
<p>In this mode the watcher will always be scheduled to time out at the next |
1059 |
<code>at + N * interval</code> time (for some integer N) and then repeat, regardless |
1060 |
of any time jumps.</p> |
1061 |
<p>This can be used to create timers that do not drift with respect to system |
1062 |
time:</p> |
1063 |
<pre> ev_periodic_set (&periodic, 0., 3600., 0); |
1064 |
|
1065 |
</pre> |
1066 |
<p>This doesn't mean there will always be 3600 seconds in between triggers, |
1067 |
but only that the the callback will be called when the system time shows a |
1068 |
full hour (UTC), or more correctly, when the system time is evenly divisible |
1069 |
by 3600.</p> |
1070 |
<p>Another way to think about it (for the mathematically inclined) is that |
1071 |
<code>ev_periodic</code> will try to run the callback in this mode at the next possible |
1072 |
time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> |
1073 |
</dd> |
1074 |
<dt>* manual reschedule mode (reschedule_cb = callback)</dt> |
1075 |
<dd> |
1076 |
<p>In this mode the values for <code>interval</code> and <code>at</code> are both being |
1077 |
ignored. Instead, each time the periodic watcher gets scheduled, the |
1078 |
reschedule callback will be called with the watcher as first, and the |
1079 |
current time as second argument.</p> |
1080 |
<p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, |
1081 |
ever, or make any event loop modifications</i>. If you need to stop it, |
1082 |
return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by |
1083 |
starting a prepare watcher).</p> |
1084 |
<p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1085 |
ev_tstamp now)</code>, e.g.:</p> |
1086 |
<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1087 |
{ |
1088 |
return now + 60.; |
1089 |
} |
1090 |
|
1091 |
</pre> |
1092 |
<p>It must return the next time to trigger, based on the passed time value |
1093 |
(that is, the lowest time value larger than to the second argument). It |
1094 |
will usually be called just before the callback will be triggered, but |
1095 |
might be called at other times, too.</p> |
1096 |
<p>NOTE: <i>This callback must always return a time that is later than the |
1097 |
passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p> |
1098 |
<p>This can be used to create very complex timers, such as a timer that |
1099 |
triggers on each midnight, local time. To do this, you would calculate the |
1100 |
next midnight after <code>now</code> and return the timestamp value for this. How |
1101 |
you do this is, again, up to you (but it is not trivial, which is the main |
1102 |
reason I omitted it as an example).</p> |
1103 |
</dd> |
1104 |
</dl> |
1105 |
</p> |
1106 |
</dd> |
1107 |
<dt>ev_periodic_again (loop, ev_periodic *)</dt> |
1108 |
<dd> |
1109 |
<p>Simply stops and restarts the periodic watcher again. This is only useful |
1110 |
when you changed some parameters or the reschedule callback would return |
1111 |
a different time than the last time it was called (e.g. in a crond like |
1112 |
program when the crontabs have changed).</p> |
1113 |
</dd> |
1114 |
<dt>ev_tstamp interval [read-write]</dt> |
1115 |
<dd> |
1116 |
<p>The current interval value. Can be modified any time, but changes only |
1117 |
take effect when the periodic timer fires or <code>ev_periodic_again</code> is being |
1118 |
called.</p> |
1119 |
</dd> |
1120 |
<dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt> |
1121 |
<dd> |
1122 |
<p>The current reschedule callback, or <code>0</code>, if this functionality is |
1123 |
switched off. Can be changed any time, but changes only take effect when |
1124 |
the periodic timer fires or <code>ev_periodic_again</code> is being called.</p> |
1125 |
</dd> |
1126 |
</dl> |
1127 |
<p>Example: Call a callback every hour, or, more precisely, whenever the |
1128 |
system clock is divisible by 3600. The callback invocation times have |
1129 |
potentially a lot of jittering, but good long-term stability.</p> |
1130 |
<pre> static void |
1131 |
clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1132 |
{ |
1133 |
... its now a full hour (UTC, or TAI or whatever your clock follows) |
1134 |
} |
1135 |
|
1136 |
struct ev_periodic hourly_tick; |
1137 |
ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1138 |
ev_periodic_start (loop, &hourly_tick); |
1139 |
|
1140 |
</pre> |
1141 |
<p>Example: The same as above, but use a reschedule callback to do it:</p> |
1142 |
<pre> #include <math.h> |
1143 |
|
1144 |
static ev_tstamp |
1145 |
my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1146 |
{ |
1147 |
return fmod (now, 3600.) + 3600.; |
1148 |
} |
1149 |
|
1150 |
ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1151 |
|
1152 |
</pre> |
1153 |
<p>Example: Call a callback every hour, starting now:</p> |
1154 |
<pre> struct ev_periodic hourly_tick; |
1155 |
ev_periodic_init (&hourly_tick, clock_cb, |
1156 |
fmod (ev_now (loop), 3600.), 3600., 0); |
1157 |
ev_periodic_start (loop, &hourly_tick); |
1158 |
|
1159 |
|
1160 |
|
1161 |
|
1162 |
</pre> |
1163 |
|
1164 |
</div> |
1165 |
<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2> |
1166 |
<div id="code_ev_signal_code_signal_me_when_a-2"> |
1167 |
<p>Signal watchers will trigger an event when the process receives a specific |
1168 |
signal one or more times. Even though signals are very asynchronous, libev |
1169 |
will try it's best to deliver signals synchronously, i.e. as part of the |
1170 |
normal event processing, like any other event.</p> |
1171 |
<p>You can configure as many watchers as you like per signal. Only when the |
1172 |
first watcher gets started will libev actually register a signal watcher |
1173 |
with the kernel (thus it coexists with your own signal handlers as long |
1174 |
as you don't register any with libev). Similarly, when the last signal |
1175 |
watcher for a signal is stopped libev will reset the signal handler to |
1176 |
SIG_DFL (regardless of what it was set to before).</p> |
1177 |
<dl> |
1178 |
<dt>ev_signal_init (ev_signal *, callback, int signum)</dt> |
1179 |
<dt>ev_signal_set (ev_signal *, int signum)</dt> |
1180 |
<dd> |
1181 |
<p>Configures the watcher to trigger on the given signal number (usually one |
1182 |
of the <code>SIGxxx</code> constants).</p> |
1183 |
</dd> |
1184 |
<dt>int signum [read-only]</dt> |
1185 |
<dd> |
1186 |
<p>The signal the watcher watches out for.</p> |
1187 |
</dd> |
1188 |
</dl> |
1189 |
|
1190 |
|
1191 |
|
1192 |
|
1193 |
|
1194 |
</div> |
1195 |
<h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2> |
1196 |
<div id="code_ev_child_code_watch_out_for_pro-2"> |
1197 |
<p>Child watchers trigger when your process receives a SIGCHLD in response to |
1198 |
some child status changes (most typically when a child of yours dies).</p> |
1199 |
<dl> |
1200 |
<dt>ev_child_init (ev_child *, callback, int pid)</dt> |
1201 |
<dt>ev_child_set (ev_child *, int pid)</dt> |
1202 |
<dd> |
1203 |
<p>Configures the watcher to wait for status changes of process <code>pid</code> (or |
1204 |
<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look |
1205 |
at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see |
1206 |
the status word (use the macros from <code>sys/wait.h</code> and see your systems |
1207 |
<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the |
1208 |
process causing the status change.</p> |
1209 |
</dd> |
1210 |
<dt>int pid [read-only]</dt> |
1211 |
<dd> |
1212 |
<p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p> |
1213 |
</dd> |
1214 |
<dt>int rpid [read-write]</dt> |
1215 |
<dd> |
1216 |
<p>The process id that detected a status change.</p> |
1217 |
</dd> |
1218 |
<dt>int rstatus [read-write]</dt> |
1219 |
<dd> |
1220 |
<p>The process exit/trace status caused by <code>rpid</code> (see your systems |
1221 |
<code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p> |
1222 |
</dd> |
1223 |
</dl> |
1224 |
<p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p> |
1225 |
<pre> static void |
1226 |
sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1227 |
{ |
1228 |
ev_unloop (loop, EVUNLOOP_ALL); |
1229 |
} |
1230 |
|
1231 |
struct ev_signal signal_watcher; |
1232 |
ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1233 |
ev_signal_start (loop, &sigint_cb); |
1234 |
|
1235 |
|
1236 |
|
1237 |
|
1238 |
</pre> |
1239 |
|
1240 |
</div> |
1241 |
<h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2> |
1242 |
<div id="code_ev_stat_code_did_the_file_attri-2"> |
1243 |
<p>This watches a filesystem path for attribute changes. That is, it calls |
1244 |
<code>stat</code> regularly (or when the OS says it changed) and sees if it changed |
1245 |
compared to the last time, invoking the callback if it did.</p> |
1246 |
<p>The path does not need to exist: changing from "path exists" to "path does |
1247 |
not exist" is a status change like any other. The condition "path does |
1248 |
not exist" is signified by the <code>st_nlink</code> field being zero (which is |
1249 |
otherwise always forced to be at least one) and all the other fields of |
1250 |
the stat buffer having unspecified contents.</p> |
1251 |
<p>Since there is no standard to do this, the portable implementation simply |
1252 |
calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You |
1253 |
can specify a recommended polling interval for this case. If you specify |
1254 |
a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, |
1255 |
unspecified default</i> value will be used (which you can expect to be around |
1256 |
five seconds, although this might change dynamically). Libev will also |
1257 |
impose a minimum interval which is currently around <code>0.1</code>, but thats |
1258 |
usually overkill.</p> |
1259 |
<p>This watcher type is not meant for massive numbers of stat watchers, |
1260 |
as even with OS-supported change notifications, this can be |
1261 |
resource-intensive.</p> |
1262 |
<p>At the time of this writing, only the Linux inotify interface is |
1263 |
implemented (implementing kqueue support is left as an exercise for the |
1264 |
reader). Inotify will be used to give hints only and should not change the |
1265 |
semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs |
1266 |
to fall back to regular polling again even with inotify, but changes are |
1267 |
usually detected immediately, and if the file exists there will be no |
1268 |
polling.</p> |
1269 |
<dl> |
1270 |
<dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> |
1271 |
<dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt> |
1272 |
<dd> |
1273 |
<p>Configures the watcher to wait for status changes of the given |
1274 |
<code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to |
1275 |
be detected and should normally be specified as <code>0</code> to let libev choose |
1276 |
a suitable value. The memory pointed to by <code>path</code> must point to the same |
1277 |
path for as long as the watcher is active.</p> |
1278 |
<p>The callback will be receive <code>EV_STAT</code> when a change was detected, |
1279 |
relative to the attributes at the time the watcher was started (or the |
1280 |
last change was detected).</p> |
1281 |
</dd> |
1282 |
<dt>ev_stat_stat (ev_stat *)</dt> |
1283 |
<dd> |
1284 |
<p>Updates the stat buffer immediately with new values. If you change the |
1285 |
watched path in your callback, you could call this fucntion to avoid |
1286 |
detecting this change (while introducing a race condition). Can also be |
1287 |
useful simply to find out the new values.</p> |
1288 |
</dd> |
1289 |
<dt>ev_statdata attr [read-only]</dt> |
1290 |
<dd> |
1291 |
<p>The most-recently detected attributes of the file. Although the type is of |
1292 |
<code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types |
1293 |
suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there |
1294 |
was some error while <code>stat</code>ing the file.</p> |
1295 |
</dd> |
1296 |
<dt>ev_statdata prev [read-only]</dt> |
1297 |
<dd> |
1298 |
<p>The previous attributes of the file. The callback gets invoked whenever |
1299 |
<code>prev</code> != <code>attr</code>.</p> |
1300 |
</dd> |
1301 |
<dt>ev_tstamp interval [read-only]</dt> |
1302 |
<dd> |
1303 |
<p>The specified interval.</p> |
1304 |
</dd> |
1305 |
<dt>const char *path [read-only]</dt> |
1306 |
<dd> |
1307 |
<p>The filesystem path that is being watched.</p> |
1308 |
</dd> |
1309 |
</dl> |
1310 |
<p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p> |
1311 |
<pre> static void |
1312 |
passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
1313 |
{ |
1314 |
/* /etc/passwd changed in some way */ |
1315 |
if (w->attr.st_nlink) |
1316 |
{ |
1317 |
printf ("passwd current size %ld\n", (long)w->attr.st_size); |
1318 |
printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
1319 |
printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
1320 |
} |
1321 |
else |
1322 |
/* you shalt not abuse printf for puts */ |
1323 |
puts ("wow, /etc/passwd is not there, expect problems. " |
1324 |
"if this is windows, they already arrived\n"); |
1325 |
} |
1326 |
|
1327 |
... |
1328 |
ev_stat passwd; |
1329 |
|
1330 |
ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); |
1331 |
ev_stat_start (loop, &passwd); |
1332 |
|
1333 |
|
1334 |
|
1335 |
|
1336 |
</pre> |
1337 |
|
1338 |
</div> |
1339 |
<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> |
1340 |
<div id="code_ev_idle_code_when_you_ve_got_no-2"> |
1341 |
<p>Idle watchers trigger events when there are no other events are pending |
1342 |
(prepare, check and other idle watchers do not count). That is, as long |
1343 |
as your process is busy handling sockets or timeouts (or even signals, |
1344 |
imagine) it will not be triggered. But when your process is idle all idle |
1345 |
watchers are being called again and again, once per event loop iteration - |
1346 |
until stopped, that is, or your process receives more events and becomes |
1347 |
busy.</p> |
1348 |
<p>The most noteworthy effect is that as long as any idle watchers are |
1349 |
active, the process will not block when waiting for new events.</p> |
1350 |
<p>Apart from keeping your process non-blocking (which is a useful |
1351 |
effect on its own sometimes), idle watchers are a good place to do |
1352 |
"pseudo-background processing", or delay processing stuff to after the |
1353 |
event loop has handled all outstanding events.</p> |
1354 |
<dl> |
1355 |
<dt>ev_idle_init (ev_signal *, callback)</dt> |
1356 |
<dd> |
1357 |
<p>Initialises and configures the idle watcher - it has no parameters of any |
1358 |
kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, |
1359 |
believe me.</p> |
1360 |
</dd> |
1361 |
</dl> |
1362 |
<p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the |
1363 |
callback, free it. Also, use no error checking, as usual.</p> |
1364 |
<pre> static void |
1365 |
idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
1366 |
{ |
1367 |
free (w); |
1368 |
// now do something you wanted to do when the program has |
1369 |
// no longer asnything immediate to do. |
1370 |
} |
1371 |
|
1372 |
struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
1373 |
ev_idle_init (idle_watcher, idle_cb); |
1374 |
ev_idle_start (loop, idle_cb); |
1375 |
|
1376 |
|
1377 |
|
1378 |
|
1379 |
</pre> |
1380 |
|
1381 |
</div> |
1382 |
<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2> |
1383 |
<div id="code_ev_prepare_code_and_code_ev_che-2"> |
1384 |
<p>Prepare and check watchers are usually (but not always) used in tandem: |
1385 |
prepare watchers get invoked before the process blocks and check watchers |
1386 |
afterwards.</p> |
1387 |
<p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter |
1388 |
the current event loop from either <code>ev_prepare</code> or <code>ev_check</code> |
1389 |
watchers. Other loops than the current one are fine, however. The |
1390 |
rationale behind this is that you do not need to check for recursion in |
1391 |
those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking, |
1392 |
<code>ev_check</code> so if you have one watcher of each kind they will always be |
1393 |
called in pairs bracketing the blocking call.</p> |
1394 |
<p>Their main purpose is to integrate other event mechanisms into libev and |
1395 |
their use is somewhat advanced. This could be used, for example, to track |
1396 |
variable changes, implement your own watchers, integrate net-snmp or a |
1397 |
coroutine library and lots more. They are also occasionally useful if |
1398 |
you cache some data and want to flush it before blocking (for example, |
1399 |
in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code> |
1400 |
watcher).</p> |
1401 |
<p>This is done by examining in each prepare call which file descriptors need |
1402 |
to be watched by the other library, registering <code>ev_io</code> watchers for |
1403 |
them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries |
1404 |
provide just this functionality). Then, in the check watcher you check for |
1405 |
any events that occured (by checking the pending status of all watchers |
1406 |
and stopping them) and call back into the library. The I/O and timer |
1407 |
callbacks will never actually be called (but must be valid nevertheless, |
1408 |
because you never know, you know?).</p> |
1409 |
<p>As another example, the Perl Coro module uses these hooks to integrate |
1410 |
coroutines into libev programs, by yielding to other active coroutines |
1411 |
during each prepare and only letting the process block if no coroutines |
1412 |
are ready to run (it's actually more complicated: it only runs coroutines |
1413 |
with priority higher than or equal to the event loop and one coroutine |
1414 |
of lower priority, but only once, using idle watchers to keep the event |
1415 |
loop from blocking if lower-priority coroutines are active, thus mapping |
1416 |
low-priority coroutines to idle/background tasks).</p> |
1417 |
<dl> |
1418 |
<dt>ev_prepare_init (ev_prepare *, callback)</dt> |
1419 |
<dt>ev_check_init (ev_check *, callback)</dt> |
1420 |
<dd> |
1421 |
<p>Initialises and configures the prepare or check watcher - they have no |
1422 |
parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1423 |
macros, but using them is utterly, utterly and completely pointless.</p> |
1424 |
</dd> |
1425 |
</dl> |
1426 |
<p>Example: To include a library such as adns, you would add IO watchers |
1427 |
and a timeout watcher in a prepare handler, as required by libadns, and |
1428 |
in a check watcher, destroy them and call into libadns. What follows is |
1429 |
pseudo-code only of course:</p> |
1430 |
<pre> static ev_io iow [nfd]; |
1431 |
static ev_timer tw; |
1432 |
|
1433 |
static void |
1434 |
io_cb (ev_loop *loop, ev_io *w, int revents) |
1435 |
{ |
1436 |
// set the relevant poll flags |
1437 |
// could also call adns_processreadable etc. here |
1438 |
struct pollfd *fd = (struct pollfd *)w->data; |
1439 |
if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
1440 |
if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
1441 |
} |
1442 |
|
1443 |
// create io watchers for each fd and a timer before blocking |
1444 |
static void |
1445 |
adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
1446 |
{ |
1447 |
int timeout = 3600000;truct pollfd fds [nfd]; |
1448 |
// actual code will need to loop here and realloc etc. |
1449 |
adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1450 |
|
1451 |
/* the callback is illegal, but won't be called as we stop during check */ |
1452 |
ev_timer_init (&tw, 0, timeout * 1e-3); |
1453 |
ev_timer_start (loop, &tw); |
1454 |
|
1455 |
// create on ev_io per pollfd |
1456 |
for (int i = 0; i < nfd; ++i) |
1457 |
{ |
1458 |
ev_io_init (iow + i, io_cb, fds [i].fd, |
1459 |
((fds [i].events & POLLIN ? EV_READ : 0) |
1460 |
| (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1461 |
|
1462 |
fds [i].revents = 0; |
1463 |
iow [i].data = fds + i; |
1464 |
ev_io_start (loop, iow + i); |
1465 |
} |
1466 |
} |
1467 |
|
1468 |
// stop all watchers after blocking |
1469 |
static void |
1470 |
adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1471 |
{ |
1472 |
ev_timer_stop (loop, &tw); |
1473 |
|
1474 |
for (int i = 0; i < nfd; ++i) |
1475 |
ev_io_stop (loop, iow + i); |
1476 |
|
1477 |
adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1478 |
} |
1479 |
|
1480 |
|
1481 |
|
1482 |
|
1483 |
</pre> |
1484 |
|
1485 |
</div> |
1486 |
<h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2> |
1487 |
<div id="code_ev_embed_code_when_one_backend_-2"> |
1488 |
<p>This is a rather advanced watcher type that lets you embed one event loop |
1489 |
into another (currently only <code>ev_io</code> events are supported in the embedded |
1490 |
loop, other types of watchers might be handled in a delayed or incorrect |
1491 |
fashion and must not be used).</p> |
1492 |
<p>There are primarily two reasons you would want that: work around bugs and |
1493 |
prioritise I/O.</p> |
1494 |
<p>As an example for a bug workaround, the kqueue backend might only support |
1495 |
sockets on some platform, so it is unusable as generic backend, but you |
1496 |
still want to make use of it because you have many sockets and it scales |
1497 |
so nicely. In this case, you would create a kqueue-based loop and embed it |
1498 |
into your default loop (which might use e.g. poll). Overall operation will |
1499 |
be a bit slower because first libev has to poll and then call kevent, but |
1500 |
at least you can use both at what they are best.</p> |
1501 |
<p>As for prioritising I/O: rarely you have the case where some fds have |
1502 |
to be watched and handled very quickly (with low latency), and even |
1503 |
priorities and idle watchers might have too much overhead. In this case |
1504 |
you would put all the high priority stuff in one loop and all the rest in |
1505 |
a second one, and embed the second one in the first.</p> |
1506 |
<p>As long as the watcher is active, the callback will be invoked every time |
1507 |
there might be events pending in the embedded loop. The callback must then |
1508 |
call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke |
1509 |
their callbacks (you could also start an idle watcher to give the embedded |
1510 |
loop strictly lower priority for example). You can also set the callback |
1511 |
to <code>0</code>, in which case the embed watcher will automatically execute the |
1512 |
embedded loop sweep.</p> |
1513 |
<p>As long as the watcher is started it will automatically handle events. The |
1514 |
callback will be invoked whenever some events have been handled. You can |
1515 |
set the callback to <code>0</code> to avoid having to specify one if you are not |
1516 |
interested in that.</p> |
1517 |
<p>Also, there have not currently been made special provisions for forking: |
1518 |
when you fork, you not only have to call <code>ev_loop_fork</code> on both loops, |
1519 |
but you will also have to stop and restart any <code>ev_embed</code> watchers |
1520 |
yourself.</p> |
1521 |
<p>Unfortunately, not all backends are embeddable, only the ones returned by |
1522 |
<code>ev_embeddable_backends</code> are, which, unfortunately, does not include any |
1523 |
portable one.</p> |
1524 |
<p>So when you want to use this feature you will always have to be prepared |
1525 |
that you cannot get an embeddable loop. The recommended way to get around |
1526 |
this is to have a separate variables for your embeddable loop, try to |
1527 |
create it, and if that fails, use the normal loop for everything:</p> |
1528 |
<pre> struct ev_loop *loop_hi = ev_default_init (0); |
1529 |
struct ev_loop *loop_lo = 0; |
1530 |
struct ev_embed embed; |
1531 |
|
1532 |
// see if there is a chance of getting one that works |
1533 |
// (remember that a flags value of 0 means autodetection) |
1534 |
loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
1535 |
? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
1536 |
: 0; |
1537 |
|
1538 |
// if we got one, then embed it, otherwise default to loop_hi |
1539 |
if (loop_lo) |
1540 |
{ |
1541 |
ev_embed_init (&embed, 0, loop_lo); |
1542 |
ev_embed_start (loop_hi, &embed); |
1543 |
} |
1544 |
else |
1545 |
loop_lo = loop_hi; |
1546 |
|
1547 |
</pre> |
1548 |
<dl> |
1549 |
<dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt> |
1550 |
<dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt> |
1551 |
<dd> |
1552 |
<p>Configures the watcher to embed the given loop, which must be |
1553 |
embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be |
1554 |
invoked automatically, otherwise it is the responsibility of the callback |
1555 |
to invoke it (it will continue to be called until the sweep has been done, |
1556 |
if you do not want thta, you need to temporarily stop the embed watcher).</p> |
1557 |
</dd> |
1558 |
<dt>ev_embed_sweep (loop, ev_embed *)</dt> |
1559 |
<dd> |
1560 |
<p>Make a single, non-blocking sweep over the embedded loop. This works |
1561 |
similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most |
1562 |
apropriate way for embedded loops.</p> |
1563 |
</dd> |
1564 |
<dt>struct ev_loop *loop [read-only]</dt> |
1565 |
<dd> |
1566 |
<p>The embedded event loop.</p> |
1567 |
</dd> |
1568 |
</dl> |
1569 |
|
1570 |
|
1571 |
|
1572 |
|
1573 |
|
1574 |
</div> |
1575 |
<h2 id="code_ev_fork_code_the_audacity_to_re"><code>ev_fork</code> - the audacity to resume the event loop after a fork</h2> |
1576 |
<div id="code_ev_fork_code_the_audacity_to_re-2"> |
1577 |
<p>Fork watchers are called when a <code>fork ()</code> was detected (usually because |
1578 |
whoever is a good citizen cared to tell libev about it by calling |
1579 |
<code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the |
1580 |
event loop blocks next and before <code>ev_check</code> watchers are being called, |
1581 |
and only in the child after the fork. If whoever good citizen calling |
1582 |
<code>ev_default_fork</code> cheats and calls it in the wrong process, the fork |
1583 |
handlers will be invoked, too, of course.</p> |
1584 |
<dl> |
1585 |
<dt>ev_fork_init (ev_signal *, callback)</dt> |
1586 |
<dd> |
1587 |
<p>Initialises and configures the fork watcher - it has no parameters of any |
1588 |
kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless, |
1589 |
believe me.</p> |
1590 |
</dd> |
1591 |
</dl> |
1592 |
|
1593 |
|
1594 |
|
1595 |
|
1596 |
|
1597 |
</div> |
1598 |
<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1> |
1599 |
<div id="OTHER_FUNCTIONS_CONTENT"> |
1600 |
<p>There are some other functions of possible interest. Described. Here. Now.</p> |
1601 |
<dl> |
1602 |
<dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> |
1603 |
<dd> |
1604 |
<p>This function combines a simple timer and an I/O watcher, calls your |
1605 |
callback on whichever event happens first and automatically stop both |
1606 |
watchers. This is useful if you want to wait for a single event on an fd |
1607 |
or timeout without having to allocate/configure/start/stop/free one or |
1608 |
more watchers yourself.</p> |
1609 |
<p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events |
1610 |
is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and |
1611 |
<code>events</code> set will be craeted and started.</p> |
1612 |
<p>If <code>timeout</code> is less than 0, then no timeout watcher will be |
1613 |
started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and |
1614 |
repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of |
1615 |
dubious value.</p> |
1616 |
<p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets |
1617 |
passed an <code>revents</code> set like normal event callbacks (a combination of |
1618 |
<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> |
1619 |
value passed to <code>ev_once</code>:</p> |
1620 |
<pre> static void stdin_ready (int revents, void *arg) |
1621 |
{ |
1622 |
if (revents & EV_TIMEOUT) |
1623 |
/* doh, nothing entered */; |
1624 |
else if (revents & EV_READ) |
1625 |
/* stdin might have data for us, joy! */; |
1626 |
} |
1627 |
|
1628 |
ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
1629 |
|
1630 |
</pre> |
1631 |
</dd> |
1632 |
<dt>ev_feed_event (ev_loop *, watcher *, int revents)</dt> |
1633 |
<dd> |
1634 |
<p>Feeds the given event set into the event loop, as if the specified event |
1635 |
had happened for the specified watcher (which must be a pointer to an |
1636 |
initialised but not necessarily started event watcher).</p> |
1637 |
</dd> |
1638 |
<dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt> |
1639 |
<dd> |
1640 |
<p>Feed an event on the given fd, as if a file descriptor backend detected |
1641 |
the given events it.</p> |
1642 |
</dd> |
1643 |
<dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt> |
1644 |
<dd> |
1645 |
<p>Feed an event as if the given signal occured (<code>loop</code> must be the default |
1646 |
loop!).</p> |
1647 |
</dd> |
1648 |
</dl> |
1649 |
|
1650 |
|
1651 |
|
1652 |
|
1653 |
|
1654 |
</div> |
1655 |
<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1> |
1656 |
<div id="LIBEVENT_EMULATION_CONTENT"> |
1657 |
<p>Libev offers a compatibility emulation layer for libevent. It cannot |
1658 |
emulate the internals of libevent, so here are some usage hints:</p> |
1659 |
<dl> |
1660 |
<dt>* Use it by including <event.h>, as usual.</dt> |
1661 |
<dt>* The following members are fully supported: ev_base, ev_callback, |
1662 |
ev_arg, ev_fd, ev_res, ev_events.</dt> |
1663 |
<dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is |
1664 |
maintained by libev, it does not work exactly the same way as in libevent (consider |
1665 |
it a private API).</dt> |
1666 |
<dt>* Priorities are not currently supported. Initialising priorities |
1667 |
will fail and all watchers will have the same priority, even though there |
1668 |
is an ev_pri field.</dt> |
1669 |
<dt>* Other members are not supported.</dt> |
1670 |
<dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need |
1671 |
to use the libev header file and library.</dt> |
1672 |
</dl> |
1673 |
|
1674 |
</div> |
1675 |
<h1 id="C_SUPPORT">C++ SUPPORT</h1> |
1676 |
<div id="C_SUPPORT_CONTENT"> |
1677 |
<p>Libev comes with some simplistic wrapper classes for C++ that mainly allow |
1678 |
you to use some convinience methods to start/stop watchers and also change |
1679 |
the callback model to a model using method callbacks on objects.</p> |
1680 |
<p>To use it,</p> |
1681 |
<pre> #include <ev++.h> |
1682 |
|
1683 |
</pre> |
1684 |
<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> |
1685 |
and puts all of its definitions (many of them macros) into the global |
1686 |
namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> |
1687 |
<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably |
1688 |
<code>EV_MULTIPLICITY</code>.</p> |
1689 |
<p>Here is a list of things available in the <code>ev</code> namespace:</p> |
1690 |
<dl> |
1691 |
<dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> |
1692 |
<dd> |
1693 |
<p>These are just enum values with the same values as the <code>EV_READ</code> etc. |
1694 |
macros from <cite>ev.h</cite>.</p> |
1695 |
</dd> |
1696 |
<dt><code>ev::tstamp</code>, <code>ev::now</code></dt> |
1697 |
<dd> |
1698 |
<p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p> |
1699 |
</dd> |
1700 |
<dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt> |
1701 |
<dd> |
1702 |
<p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of |
1703 |
the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code> |
1704 |
which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro |
1705 |
defines by many implementations.</p> |
1706 |
<p>All of those classes have these methods:</p> |
1707 |
<p> |
1708 |
<dl> |
1709 |
<dt>ev::TYPE::TYPE (object *, object::method *)</dt> |
1710 |
<dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> |
1711 |
<dt>ev::TYPE::~TYPE</dt> |
1712 |
<dd> |
1713 |
<p>The constructor takes a pointer to an object and a method pointer to |
1714 |
the event handler callback to call in this class. The constructor calls |
1715 |
<code>ev_init</code> for you, which means you have to call the <code>set</code> method |
1716 |
before starting it. If you do not specify a loop then the constructor |
1717 |
automatically associates the default loop with this watcher.</p> |
1718 |
<p>The destructor automatically stops the watcher if it is active.</p> |
1719 |
</dd> |
1720 |
<dt>w->set (struct ev_loop *)</dt> |
1721 |
<dd> |
1722 |
<p>Associates a different <code>struct ev_loop</code> with this watcher. You can only |
1723 |
do this when the watcher is inactive (and not pending either).</p> |
1724 |
</dd> |
1725 |
<dt>w->set ([args])</dt> |
1726 |
<dd> |
1727 |
<p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be |
1728 |
called at least once. Unlike the C counterpart, an active watcher gets |
1729 |
automatically stopped and restarted.</p> |
1730 |
</dd> |
1731 |
<dt>w->start ()</dt> |
1732 |
<dd> |
1733 |
<p>Starts the watcher. Note that there is no <code>loop</code> argument as the |
1734 |
constructor already takes the loop.</p> |
1735 |
</dd> |
1736 |
<dt>w->stop ()</dt> |
1737 |
<dd> |
1738 |
<p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> |
1739 |
</dd> |
1740 |
<dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt> |
1741 |
<dd> |
1742 |
<p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding |
1743 |
<code>ev_TYPE_again</code> function.</p> |
1744 |
</dd> |
1745 |
<dt>w->sweep () <code>ev::embed</code> only</dt> |
1746 |
<dd> |
1747 |
<p>Invokes <code>ev_embed_sweep</code>.</p> |
1748 |
</dd> |
1749 |
<dt>w->update () <code>ev::stat</code> only</dt> |
1750 |
<dd> |
1751 |
<p>Invokes <code>ev_stat_stat</code>.</p> |
1752 |
</dd> |
1753 |
</dl> |
1754 |
</p> |
1755 |
</dd> |
1756 |
</dl> |
1757 |
<p>Example: Define a class with an IO and idle watcher, start one of them in |
1758 |
the constructor.</p> |
1759 |
<pre> class myclass |
1760 |
{ |
1761 |
ev_io io; void io_cb (ev::io &w, int revents); |
1762 |
ev_idle idle void idle_cb (ev::idle &w, int revents); |
1763 |
|
1764 |
myclass (); |
1765 |
} |
1766 |
|
1767 |
myclass::myclass (int fd) |
1768 |
: io (this, &myclass::io_cb), |
1769 |
idle (this, &myclass::idle_cb) |
1770 |
{ |
1771 |
io.start (fd, ev::READ); |
1772 |
} |
1773 |
|
1774 |
|
1775 |
|
1776 |
|
1777 |
</pre> |
1778 |
|
1779 |
</div> |
1780 |
<h1 id="MACRO_MAGIC">MACRO MAGIC</h1> |
1781 |
<div id="MACRO_MAGIC_CONTENT"> |
1782 |
<p>Libev can be compiled with a variety of options, the most fundemantal is |
1783 |
<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and |
1784 |
callbacks have an initial <code>struct ev_loop *</code> argument.</p> |
1785 |
<p>To make it easier to write programs that cope with either variant, the |
1786 |
following macros are defined:</p> |
1787 |
<dl> |
1788 |
<dt><code>EV_A</code>, <code>EV_A_</code></dt> |
1789 |
<dd> |
1790 |
<p>This provides the loop <i>argument</i> for functions, if one is required ("ev |
1791 |
loop argument"). The <code>EV_A</code> form is used when this is the sole argument, |
1792 |
<code>EV_A_</code> is used when other arguments are following. Example:</p> |
1793 |
<pre> ev_unref (EV_A); |
1794 |
ev_timer_add (EV_A_ watcher); |
1795 |
ev_loop (EV_A_ 0); |
1796 |
|
1797 |
</pre> |
1798 |
<p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope, |
1799 |
which is often provided by the following macro.</p> |
1800 |
</dd> |
1801 |
<dt><code>EV_P</code>, <code>EV_P_</code></dt> |
1802 |
<dd> |
1803 |
<p>This provides the loop <i>parameter</i> for functions, if one is required ("ev |
1804 |
loop parameter"). The <code>EV_P</code> form is used when this is the sole parameter, |
1805 |
<code>EV_P_</code> is used when other parameters are following. Example:</p> |
1806 |
<pre> // this is how ev_unref is being declared |
1807 |
static void ev_unref (EV_P); |
1808 |
|
1809 |
// this is how you can declare your typical callback |
1810 |
static void cb (EV_P_ ev_timer *w, int revents) |
1811 |
|
1812 |
</pre> |
1813 |
<p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite |
1814 |
suitable for use with <code>EV_A</code>.</p> |
1815 |
</dd> |
1816 |
<dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt> |
1817 |
<dd> |
1818 |
<p>Similar to the other two macros, this gives you the value of the default |
1819 |
loop, if multiple loops are supported ("ev loop default").</p> |
1820 |
</dd> |
1821 |
</dl> |
1822 |
<p>Example: Declare and initialise a check watcher, working regardless of |
1823 |
wether multiple loops are supported or not.</p> |
1824 |
<pre> static void |
1825 |
check_cb (EV_P_ ev_timer *w, int revents) |
1826 |
{ |
1827 |
ev_check_stop (EV_A_ w); |
1828 |
} |
1829 |
|
1830 |
ev_check check; |
1831 |
ev_check_init (&check, check_cb); |
1832 |
ev_check_start (EV_DEFAULT_ &check); |
1833 |
ev_loop (EV_DEFAULT_ 0); |
1834 |
|
1835 |
|
1836 |
|
1837 |
|
1838 |
</pre> |
1839 |
|
1840 |
</div> |
1841 |
<h1 id="EMBEDDING">EMBEDDING</h1> |
1842 |
<div id="EMBEDDING_CONTENT"> |
1843 |
<p>Libev can (and often is) directly embedded into host |
1844 |
applications. Examples of applications that embed it include the Deliantra |
1845 |
Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) |
1846 |
and rxvt-unicode.</p> |
1847 |
<p>The goal is to enable you to just copy the neecssary files into your |
1848 |
source directory without having to change even a single line in them, so |
1849 |
you can easily upgrade by simply copying (or having a checked-out copy of |
1850 |
libev somewhere in your source tree).</p> |
1851 |
|
1852 |
</div> |
1853 |
<h2 id="FILESETS">FILESETS</h2> |
1854 |
<div id="FILESETS_CONTENT"> |
1855 |
<p>Depending on what features you need you need to include one or more sets of files |
1856 |
in your app.</p> |
1857 |
|
1858 |
</div> |
1859 |
<h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3> |
1860 |
<div id="CORE_EVENT_LOOP_CONTENT"> |
1861 |
<p>To include only the libev core (all the <code>ev_*</code> functions), with manual |
1862 |
configuration (no autoconf):</p> |
1863 |
<pre> #define EV_STANDALONE 1 |
1864 |
#include "ev.c" |
1865 |
|
1866 |
</pre> |
1867 |
<p>This will automatically include <cite>ev.h</cite>, too, and should be done in a |
1868 |
single C source file only to provide the function implementations. To use |
1869 |
it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best |
1870 |
done by writing a wrapper around <cite>ev.h</cite> that you can include instead and |
1871 |
where you can put other configuration options):</p> |
1872 |
<pre> #define EV_STANDALONE 1 |
1873 |
#include "ev.h" |
1874 |
|
1875 |
</pre> |
1876 |
<p>Both header files and implementation files can be compiled with a C++ |
1877 |
compiler (at least, thats a stated goal, and breakage will be treated |
1878 |
as a bug).</p> |
1879 |
<p>You need the following files in your source tree, or in a directory |
1880 |
in your include path (e.g. in libev/ when using -Ilibev):</p> |
1881 |
<pre> ev.h |
1882 |
ev.c |
1883 |
ev_vars.h |
1884 |
ev_wrap.h |
1885 |
|
1886 |
ev_win32.c required on win32 platforms only |
1887 |
|
1888 |
ev_select.c only when select backend is enabled (which is by default) |
1889 |
ev_poll.c only when poll backend is enabled (disabled by default) |
1890 |
ev_epoll.c only when the epoll backend is enabled (disabled by default) |
1891 |
ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
1892 |
ev_port.c only when the solaris port backend is enabled (disabled by default) |
1893 |
|
1894 |
</pre> |
1895 |
<p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need |
1896 |
to compile this single file.</p> |
1897 |
|
1898 |
</div> |
1899 |
<h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3> |
1900 |
<div id="LIBEVENT_COMPATIBILITY_API_CONTENT"> |
1901 |
<p>To include the libevent compatibility API, also include:</p> |
1902 |
<pre> #include "event.c" |
1903 |
|
1904 |
</pre> |
1905 |
<p>in the file including <cite>ev.c</cite>, and:</p> |
1906 |
<pre> #include "event.h" |
1907 |
|
1908 |
</pre> |
1909 |
<p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p> |
1910 |
<p>You need the following additional files for this:</p> |
1911 |
<pre> event.h |
1912 |
event.c |
1913 |
|
1914 |
</pre> |
1915 |
|
1916 |
</div> |
1917 |
<h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3> |
1918 |
<div id="AUTOCONF_SUPPORT_CONTENT"> |
1919 |
<p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in |
1920 |
whatever way you want, you can also <code>m4_include([libev.m4])</code> in your |
1921 |
<cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then |
1922 |
include <cite>config.h</cite> and configure itself accordingly.</p> |
1923 |
<p>For this of course you need the m4 file:</p> |
1924 |
<pre> libev.m4 |
1925 |
|
1926 |
</pre> |
1927 |
|
1928 |
</div> |
1929 |
<h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2> |
1930 |
<div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT"> |
1931 |
<p>Libev can be configured via a variety of preprocessor symbols you have to define |
1932 |
before including any of its files. The default is not to build for multiplicity |
1933 |
and only include the select backend.</p> |
1934 |
<dl> |
1935 |
<dt>EV_STANDALONE</dt> |
1936 |
<dd> |
1937 |
<p>Must always be <code>1</code> if you do not use autoconf configuration, which |
1938 |
keeps libev from including <cite>config.h</cite>, and it also defines dummy |
1939 |
implementations for some libevent functions (such as logging, which is not |
1940 |
supported). It will also not define any of the structs usually found in |
1941 |
<cite>event.h</cite> that are not directly supported by the libev core alone.</p> |
1942 |
</dd> |
1943 |
<dt>EV_USE_MONOTONIC</dt> |
1944 |
<dd> |
1945 |
<p>If defined to be <code>1</code>, libev will try to detect the availability of the |
1946 |
monotonic clock option at both compiletime and runtime. Otherwise no use |
1947 |
of the monotonic clock option will be attempted. If you enable this, you |
1948 |
usually have to link against librt or something similar. Enabling it when |
1949 |
the functionality isn't available is safe, though, althoguh you have |
1950 |
to make sure you link against any libraries where the <code>clock_gettime</code> |
1951 |
function is hiding in (often <cite>-lrt</cite>).</p> |
1952 |
</dd> |
1953 |
<dt>EV_USE_REALTIME</dt> |
1954 |
<dd> |
1955 |
<p>If defined to be <code>1</code>, libev will try to detect the availability of the |
1956 |
realtime clock option at compiletime (and assume its availability at |
1957 |
runtime if successful). Otherwise no use of the realtime clock option will |
1958 |
be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get |
1959 |
(CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries |
1960 |
in the description of <code>EV_USE_MONOTONIC</code>, though.</p> |
1961 |
</dd> |
1962 |
<dt>EV_USE_SELECT</dt> |
1963 |
<dd> |
1964 |
<p>If undefined or defined to be <code>1</code>, libev will compile in support for the |
1965 |
<code>select</code>(2) backend. No attempt at autodetection will be done: if no |
1966 |
other method takes over, select will be it. Otherwise the select backend |
1967 |
will not be compiled in.</p> |
1968 |
</dd> |
1969 |
<dt>EV_SELECT_USE_FD_SET</dt> |
1970 |
<dd> |
1971 |
<p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code> |
1972 |
structure. This is useful if libev doesn't compile due to a missing |
1973 |
<code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on |
1974 |
exotic systems. This usually limits the range of file descriptors to some |
1975 |
low limit such as 1024 or might have other limitations (winsocket only |
1976 |
allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might |
1977 |
influence the size of the <code>fd_set</code> used.</p> |
1978 |
</dd> |
1979 |
<dt>EV_SELECT_IS_WINSOCKET</dt> |
1980 |
<dd> |
1981 |
<p>When defined to <code>1</code>, the select backend will assume that |
1982 |
select/socket/connect etc. don't understand file descriptors but |
1983 |
wants osf handles on win32 (this is the case when the select to |
1984 |
be used is the winsock select). This means that it will call |
1985 |
<code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise, |
1986 |
it is assumed that all these functions actually work on fds, even |
1987 |
on win32. Should not be defined on non-win32 platforms.</p> |
1988 |
</dd> |
1989 |
<dt>EV_USE_POLL</dt> |
1990 |
<dd> |
1991 |
<p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2) |
1992 |
backend. Otherwise it will be enabled on non-win32 platforms. It |
1993 |
takes precedence over select.</p> |
1994 |
</dd> |
1995 |
<dt>EV_USE_EPOLL</dt> |
1996 |
<dd> |
1997 |
<p>If defined to be <code>1</code>, libev will compile in support for the Linux |
1998 |
<code>epoll</code>(7) backend. Its availability will be detected at runtime, |
1999 |
otherwise another method will be used as fallback. This is the |
2000 |
preferred backend for GNU/Linux systems.</p> |
2001 |
</dd> |
2002 |
<dt>EV_USE_KQUEUE</dt> |
2003 |
<dd> |
2004 |
<p>If defined to be <code>1</code>, libev will compile in support for the BSD style |
2005 |
<code>kqueue</code>(2) backend. Its actual availability will be detected at runtime, |
2006 |
otherwise another method will be used as fallback. This is the preferred |
2007 |
backend for BSD and BSD-like systems, although on most BSDs kqueue only |
2008 |
supports some types of fds correctly (the only platform we found that |
2009 |
supports ptys for example was NetBSD), so kqueue might be compiled in, but |
2010 |
not be used unless explicitly requested. The best way to use it is to find |
2011 |
out whether kqueue supports your type of fd properly and use an embedded |
2012 |
kqueue loop.</p> |
2013 |
</dd> |
2014 |
<dt>EV_USE_PORT</dt> |
2015 |
<dd> |
2016 |
<p>If defined to be <code>1</code>, libev will compile in support for the Solaris |
2017 |
10 port style backend. Its availability will be detected at runtime, |
2018 |
otherwise another method will be used as fallback. This is the preferred |
2019 |
backend for Solaris 10 systems.</p> |
2020 |
</dd> |
2021 |
<dt>EV_USE_DEVPOLL</dt> |
2022 |
<dd> |
2023 |
<p>reserved for future expansion, works like the USE symbols above.</p> |
2024 |
</dd> |
2025 |
<dt>EV_USE_INOTIFY</dt> |
2026 |
<dd> |
2027 |
<p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify |
2028 |
interface to speed up <code>ev_stat</code> watchers. Its actual availability will |
2029 |
be detected at runtime.</p> |
2030 |
</dd> |
2031 |
<dt>EV_H</dt> |
2032 |
<dd> |
2033 |
<p>The name of the <cite>ev.h</cite> header file used to include it. The default if |
2034 |
undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This |
2035 |
can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> |
2036 |
</dd> |
2037 |
<dt>EV_CONFIG_H</dt> |
2038 |
<dd> |
2039 |
<p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override |
2040 |
<cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to |
2041 |
<code>EV_H</code>, above.</p> |
2042 |
</dd> |
2043 |
<dt>EV_EVENT_H</dt> |
2044 |
<dd> |
2045 |
<p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea |
2046 |
of how the <cite>event.h</cite> header can be found.</p> |
2047 |
</dd> |
2048 |
<dt>EV_PROTOTYPES</dt> |
2049 |
<dd> |
2050 |
<p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function |
2051 |
prototypes, but still define all the structs and other symbols. This is |
2052 |
occasionally useful if you want to provide your own wrapper functions |
2053 |
around libev functions.</p> |
2054 |
</dd> |
2055 |
<dt>EV_MULTIPLICITY</dt> |
2056 |
<dd> |
2057 |
<p>If undefined or defined to <code>1</code>, then all event-loop-specific functions |
2058 |
will have the <code>struct ev_loop *</code> as first argument, and you can create |
2059 |
additional independent event loops. Otherwise there will be no support |
2060 |
for multiple event loops and there is no first event loop pointer |
2061 |
argument. Instead, all functions act on the single default loop.</p> |
2062 |
</dd> |
2063 |
<dt>EV_PERIODIC_ENABLE</dt> |
2064 |
<dd> |
2065 |
<p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If |
2066 |
defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
2067 |
code.</p> |
2068 |
</dd> |
2069 |
<dt>EV_EMBED_ENABLE</dt> |
2070 |
<dd> |
2071 |
<p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If |
2072 |
defined to be <code>0</code>, then they are not.</p> |
2073 |
</dd> |
2074 |
<dt>EV_STAT_ENABLE</dt> |
2075 |
<dd> |
2076 |
<p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If |
2077 |
defined to be <code>0</code>, then they are not.</p> |
2078 |
</dd> |
2079 |
<dt>EV_FORK_ENABLE</dt> |
2080 |
<dd> |
2081 |
<p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If |
2082 |
defined to be <code>0</code>, then they are not.</p> |
2083 |
</dd> |
2084 |
<dt>EV_MINIMAL</dt> |
2085 |
<dd> |
2086 |
<p>If you need to shave off some kilobytes of code at the expense of some |
2087 |
speed, define this symbol to <code>1</code>. Currently only used for gcc to override |
2088 |
some inlining decisions, saves roughly 30% codesize of amd64.</p> |
2089 |
</dd> |
2090 |
<dt>EV_PID_HASHSIZE</dt> |
2091 |
<dd> |
2092 |
<p><code>ev_child</code> watchers use a small hash table to distribute workload by |
2093 |
pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more |
2094 |
than enough. If you need to manage thousands of children you might want to |
2095 |
increase this value (<i>must</i> be a power of two).</p> |
2096 |
</dd> |
2097 |
<dt>EV_INOTIFY_HASHSIZE</dt> |
2098 |
<dd> |
2099 |
<p><code>ev_staz</code> watchers use a small hash table to distribute workload by |
2100 |
inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), |
2101 |
usually more than enough. If you need to manage thousands of <code>ev_stat</code> |
2102 |
watchers you might want to increase this value (<i>must</i> be a power of |
2103 |
two).</p> |
2104 |
</dd> |
2105 |
<dt>EV_COMMON</dt> |
2106 |
<dd> |
2107 |
<p>By default, all watchers have a <code>void *data</code> member. By redefining |
2108 |
this macro to a something else you can include more and other types of |
2109 |
members. You have to define it each time you include one of the files, |
2110 |
though, and it must be identical each time.</p> |
2111 |
<p>For example, the perl EV module uses something like this:</p> |
2112 |
<pre> #define EV_COMMON \ |
2113 |
SV *self; /* contains this struct */ \ |
2114 |
SV *cb_sv, *fh /* note no trailing ";" */ |
2115 |
|
2116 |
</pre> |
2117 |
</dd> |
2118 |
<dt>EV_CB_DECLARE (type)</dt> |
2119 |
<dt>EV_CB_INVOKE (watcher, revents)</dt> |
2120 |
<dt>ev_set_cb (ev, cb)</dt> |
2121 |
<dd> |
2122 |
<p>Can be used to change the callback member declaration in each watcher, |
2123 |
and the way callbacks are invoked and set. Must expand to a struct member |
2124 |
definition and a statement, respectively. See the <cite>ev.v</cite> header file for |
2125 |
their default definitions. One possible use for overriding these is to |
2126 |
avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use |
2127 |
method calls instead of plain function calls in C++.</p> |
2128 |
|
2129 |
</div> |
2130 |
<h2 id="EXAMPLES">EXAMPLES</h2> |
2131 |
<div id="EXAMPLES_CONTENT"> |
2132 |
<p>For a real-world example of a program the includes libev |
2133 |
verbatim, you can have a look at the EV perl module |
2134 |
(<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in |
2135 |
the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public |
2136 |
interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file |
2137 |
will be compiled. It is pretty complex because it provides its own header |
2138 |
file.</p> |
2139 |
<p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file |
2140 |
that everybody includes and which overrides some autoconf choices:</p> |
2141 |
<pre> #define EV_USE_POLL 0 |
2142 |
#define EV_MULTIPLICITY 0 |
2143 |
#define EV_PERIODICS 0 |
2144 |
#define EV_CONFIG_H <config.h> |
2145 |
|
2146 |
#include "ev++.h" |
2147 |
|
2148 |
</pre> |
2149 |
<p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> |
2150 |
<pre> #include "ev_cpp.h" |
2151 |
#include "ev.c" |
2152 |
|
2153 |
|
2154 |
|
2155 |
|
2156 |
</pre> |
2157 |
|
2158 |
</div> |
2159 |
<h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
2160 |
<div id="COMPLEXITIES_CONTENT"> |
2161 |
<p>In this section the complexities of (many of) the algorithms used inside |
2162 |
libev will be explained. For complexity discussions about backends see the |
2163 |
documentation for <code>ev_default_init</code>.</p> |
2164 |
<p> |
2165 |
<dl> |
2166 |
<dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
2167 |
<dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
2168 |
<dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
2169 |
<dt>Stopping check/prepare/idle watchers: O(1)</dt> |
2170 |
<dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
2171 |
<dt>Finding the next timer per loop iteration: O(1)</dt> |
2172 |
<dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
2173 |
<dt>Activating one watcher: O(1)</dt> |
2174 |
</dl> |
2175 |
</p> |
2176 |
|
2177 |
|
2178 |
|
2179 |
|
2180 |
|
2181 |
</div> |
2182 |
<h1 id="AUTHOR">AUTHOR</h1> |
2183 |
<div id="AUTHOR_CONTENT"> |
2184 |
<p>Marc Lehmann <libev@schmorp.de>.</p> |
2185 |
|
2186 |
</div> |
2187 |
</div></body> |
2188 |
</html> |