… | |
… | |
4 | <head> |
4 | <head> |
5 | <title>libev</title> |
5 | <title>libev</title> |
6 | <meta name="description" content="Pod documentation for libev" /> |
6 | <meta name="description" content="Pod documentation for libev" /> |
7 | <meta name="inputfile" content="<standard input>" /> |
7 | <meta name="inputfile" content="<standard input>" /> |
8 | <meta name="outputfile" content="<standard output>" /> |
8 | <meta name="outputfile" content="<standard output>" /> |
9 | <meta name="created" content="Mon Nov 12 09:03:30 2007" /> |
9 | <meta name="created" content="Fri Dec 7 17:49:47 2007" /> |
10 | <meta name="generator" content="Pod::Xhtml 1.57" /> |
10 | <meta name="generator" content="Pod::Xhtml 1.57" /> |
11 | <link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> |
11 | <link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> |
12 | <body> |
12 | <body> |
13 | <div class="pod"> |
13 | <div class="pod"> |
14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
15 | <h3 id="TOP">Index</h3> |
15 | <h3 id="TOP">Index</h3> |
16 | |
16 | |
17 | <ul><li><a href="#NAME">NAME</a></li> |
17 | <ul><li><a href="#NAME">NAME</a></li> |
18 | <li><a href="#SYNOPSIS">SYNOPSIS</a></li> |
18 | <li><a href="#SYNOPSIS">SYNOPSIS</a></li> |
|
|
19 | <li><a href="#EXAMPLE_PROGRAM">EXAMPLE PROGRAM</a></li> |
19 | <li><a href="#DESCRIPTION">DESCRIPTION</a></li> |
20 | <li><a href="#DESCRIPTION">DESCRIPTION</a></li> |
20 | <li><a href="#FEATURES">FEATURES</a></li> |
21 | <li><a href="#FEATURES">FEATURES</a></li> |
21 | <li><a href="#CONVENTIONS">CONVENTIONS</a></li> |
22 | <li><a href="#CONVENTIONS">CONVENTIONS</a></li> |
|
|
23 | <li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li> |
22 | <li><a href="#TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</a></li> |
24 | <li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li> |
23 | <li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li> |
25 | <li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li> |
24 | <li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> |
26 | <li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> |
|
|
27 | <ul><li><a href="#GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</a></li> |
25 | <ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> |
28 | <li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> |
26 | </ul> |
29 | </ul> |
27 | </li> |
30 | </li> |
28 | <li><a href="#WATCHER_TYPES">WATCHER TYPES</a> |
31 | <li><a href="#WATCHER_TYPES">WATCHER TYPES</a> |
29 | <ul><li><a href="#struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</a></li> |
32 | <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> |
30 | <li><a href="#struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</a></li> |
33 | <li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</a></li> |
31 | <li><a href="#ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</a></li> |
34 | <li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</a></li> |
32 | <li><a href="#ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</a></li> |
35 | <li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</a></li> |
33 | <li><a href="#ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</a></li> |
36 | <li><a href="#code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</a></li> |
|
|
37 | <li><a href="#code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</a></li> |
34 | <li><a href="#ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</a></li> |
38 | <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> |
35 | <li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li> |
39 | <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> |
|
|
40 | <li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</a></li> |
|
|
41 | <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> |
36 | </ul> |
42 | </ul> |
37 | </li> |
43 | </li> |
38 | <li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> |
44 | <li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> |
|
|
45 | <li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> |
|
|
46 | <li><a href="#C_SUPPORT">C++ SUPPORT</a></li> |
|
|
47 | <li><a href="#MACRO_MAGIC">MACRO MAGIC</a></li> |
|
|
48 | <li><a href="#EMBEDDING">EMBEDDING</a> |
|
|
49 | <ul><li><a href="#FILESETS">FILESETS</a> |
|
|
50 | <ul><li><a href="#CORE_EVENT_LOOP">CORE EVENT LOOP</a></li> |
|
|
51 | <li><a href="#LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</a></li> |
|
|
52 | <li><a href="#AUTOCONF_SUPPORT">AUTOCONF SUPPORT</a></li> |
|
|
53 | </ul> |
|
|
54 | </li> |
|
|
55 | <li><a href="#PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</a></li> |
|
|
56 | <li><a href="#EXAMPLES">EXAMPLES</a></li> |
|
|
57 | </ul> |
|
|
58 | </li> |
|
|
59 | <li><a href="#COMPLEXITIES">COMPLEXITIES</a></li> |
39 | <li><a href="#AUTHOR">AUTHOR</a> |
60 | <li><a href="#AUTHOR">AUTHOR</a> |
40 | </li> |
61 | </li> |
41 | </ul><hr /> |
62 | </ul><hr /> |
42 | <!-- INDEX END --> |
63 | <!-- INDEX END --> |
43 | |
64 | |
44 | <h1 id="NAME">NAME</h1><p><a href="#TOP" class="toplink">Top</a></p> |
65 | <h1 id="NAME">NAME</h1> |
45 | <div id="NAME_CONTENT"> |
66 | <div id="NAME_CONTENT"> |
46 | <p>libev - a high performance full-featured event loop written in C</p> |
67 | <p>libev - a high performance full-featured event loop written in C</p> |
47 | |
68 | |
48 | </div> |
69 | </div> |
49 | <h1 id="SYNOPSIS">SYNOPSIS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
70 | <h1 id="SYNOPSIS">SYNOPSIS</h1> |
50 | <div id="SYNOPSIS_CONTENT"> |
71 | <div id="SYNOPSIS_CONTENT"> |
51 | <pre> #include <ev.h> |
72 | <pre> #include <ev.h> |
52 | |
73 | |
53 | </pre> |
74 | </pre> |
54 | |
75 | |
55 | </div> |
76 | </div> |
56 | <h1 id="DESCRIPTION">DESCRIPTION</h1><p><a href="#TOP" class="toplink">Top</a></p> |
77 | <h1 id="EXAMPLE_PROGRAM">EXAMPLE PROGRAM</h1> |
|
|
78 | <div id="EXAMPLE_PROGRAM_CONTENT"> |
|
|
79 | <pre> #include <ev.h> |
|
|
80 | |
|
|
81 | ev_io stdin_watcher; |
|
|
82 | ev_timer timeout_watcher; |
|
|
83 | |
|
|
84 | /* called when data readable on stdin */ |
|
|
85 | static void |
|
|
86 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
|
|
87 | { |
|
|
88 | /* puts ("stdin ready"); */ |
|
|
89 | ev_io_stop (EV_A_ w); /* just a syntax example */ |
|
|
90 | ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */ |
|
|
91 | } |
|
|
92 | |
|
|
93 | static void |
|
|
94 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
|
|
95 | { |
|
|
96 | /* puts ("timeout"); */ |
|
|
97 | ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */ |
|
|
98 | } |
|
|
99 | |
|
|
100 | int |
|
|
101 | main (void) |
|
|
102 | { |
|
|
103 | struct ev_loop *loop = ev_default_loop (0); |
|
|
104 | |
|
|
105 | /* initialise an io watcher, then start it */ |
|
|
106 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
|
|
107 | ev_io_start (loop, &stdin_watcher); |
|
|
108 | |
|
|
109 | /* simple non-repeating 5.5 second timeout */ |
|
|
110 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
111 | ev_timer_start (loop, &timeout_watcher); |
|
|
112 | |
|
|
113 | /* loop till timeout or data ready */ |
|
|
114 | ev_loop (loop, 0); |
|
|
115 | |
|
|
116 | return 0; |
|
|
117 | } |
|
|
118 | |
|
|
119 | </pre> |
|
|
120 | |
|
|
121 | </div> |
|
|
122 | <h1 id="DESCRIPTION">DESCRIPTION</h1> |
57 | <div id="DESCRIPTION_CONTENT"> |
123 | <div id="DESCRIPTION_CONTENT"> |
58 | <p>Libev is an event loop: you register interest in certain events (such as a |
124 | <p>Libev is an event loop: you register interest in certain events (such as a |
59 | file descriptor being readable or a timeout occuring), and it will manage |
125 | file descriptor being readable or a timeout occuring), and it will manage |
60 | these event sources and provide your program events.</p> |
126 | these event sources and provide your program with events.</p> |
61 | <p>To do this, it must take more or less complete control over your process |
127 | <p>To do this, it must take more or less complete control over your process |
62 | (or thread) by executing the <i>event loop</i> handler, and will then |
128 | (or thread) by executing the <i>event loop</i> handler, and will then |
63 | communicate events via a callback mechanism.</p> |
129 | communicate events via a callback mechanism.</p> |
64 | <p>You register interest in certain events by registering so-called <i>event |
130 | <p>You register interest in certain events by registering so-called <i>event |
65 | watchers</i>, which are relatively small C structures you initialise with the |
131 | watchers</i>, which are relatively small C structures you initialise with the |
66 | details of the event, and then hand it over to libev by <i>starting</i> the |
132 | details of the event, and then hand it over to libev by <i>starting</i> the |
67 | watcher.</p> |
133 | watcher.</p> |
68 | |
134 | |
69 | </div> |
135 | </div> |
70 | <h1 id="FEATURES">FEATURES</h1><p><a href="#TOP" class="toplink">Top</a></p> |
136 | <h1 id="FEATURES">FEATURES</h1> |
71 | <div id="FEATURES_CONTENT"> |
137 | <div id="FEATURES_CONTENT"> |
72 | <p>Libev supports select, poll, the linux-specific epoll and the bsd-specific |
138 | <p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the |
73 | kqueue mechanisms for file descriptor events, relative timers, absolute |
139 | BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms |
74 | timers with customised rescheduling, signal events, process status change |
140 | for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface |
75 | events (related to SIGCHLD), and event watchers dealing with the event |
141 | (for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers |
76 | loop mechanism itself (idle, prepare and check watchers).</p> |
142 | with customised rescheduling (<code>ev_periodic</code>), synchronous signals |
|
|
143 | (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event |
|
|
144 | watchers dealing with the event loop mechanism itself (<code>ev_idle</code>, |
|
|
145 | <code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as |
|
|
146 | file watchers (<code>ev_stat</code>) and even limited support for fork events |
|
|
147 | (<code>ev_fork</code>).</p> |
|
|
148 | <p>It also is quite fast (see this |
|
|
149 | <a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent |
|
|
150 | for example).</p> |
77 | |
151 | |
78 | </div> |
152 | </div> |
79 | <h1 id="CONVENTIONS">CONVENTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
153 | <h1 id="CONVENTIONS">CONVENTIONS</h1> |
80 | <div id="CONVENTIONS_CONTENT"> |
154 | <div id="CONVENTIONS_CONTENT"> |
81 | <p>Libev is very configurable. In this manual the default configuration |
155 | <p>Libev is very configurable. In this manual the default configuration will |
82 | will be described, which supports multiple event loops. For more info |
156 | be described, which supports multiple event loops. For more info about |
83 | about various configuraiton options please have a look at the file |
157 | various configuration options please have a look at <strong>EMBED</strong> section in |
84 | <cite>README.embed</cite> in the libev distribution. If libev was configured without |
158 | this manual. If libev was configured without support for multiple event |
85 | support for multiple event loops, then all functions taking an initial |
159 | loops, then all functions taking an initial argument of name <code>loop</code> |
86 | argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) |
160 | (which is always of type <code>struct ev_loop *</code>) will not have this argument.</p> |
87 | will not have this argument.</p> |
|
|
88 | |
161 | |
89 | </div> |
162 | </div> |
90 | <h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
163 | <h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1> |
91 | <div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT"> |
164 | <div id="TIME_REPRESENTATION_CONTENT"> |
92 | <p>Libev represents time as a single floating point number, representing the |
165 | <p>Libev represents time as a single floating point number, representing the |
93 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
166 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
94 | the beginning of 1970, details are complicated, don't ask). This type is |
167 | the beginning of 1970, details are complicated, don't ask). This type is |
95 | called <code>ev_tstamp</code>, which is what you should use too. It usually aliases |
168 | called <code>ev_tstamp</code>, which is what you should use too. It usually aliases |
96 | to the double type in C.</p> |
169 | to the <code>double</code> type in C, and when you need to do any calculations on |
|
|
170 | it, you should treat it as such.</p> |
|
|
171 | |
|
|
172 | </div> |
|
|
173 | <h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1> |
|
|
174 | <div id="GLOBAL_FUNCTIONS_CONTENT"> |
|
|
175 | <p>These functions can be called anytime, even before initialising the |
|
|
176 | library in any way.</p> |
97 | <dl> |
177 | <dl> |
98 | <dt>ev_tstamp ev_time ()</dt> |
178 | <dt>ev_tstamp ev_time ()</dt> |
99 | <dd> |
179 | <dd> |
100 | <p>Returns the current time as libev would use it.</p> |
180 | <p>Returns the current time as libev would use it. Please note that the |
|
|
181 | <code>ev_now</code> function is usually faster and also often returns the timestamp |
|
|
182 | you actually want to know.</p> |
101 | </dd> |
183 | </dd> |
102 | <dt>int ev_version_major ()</dt> |
184 | <dt>int ev_version_major ()</dt> |
103 | <dt>int ev_version_minor ()</dt> |
185 | <dt>int ev_version_minor ()</dt> |
104 | <dd> |
186 | <dd> |
105 | <p>You can find out the major and minor version numbers of the library |
187 | <p>You can find out the major and minor version numbers of the library |
106 | you linked against by calling the functions <code>ev_version_major</code> and |
188 | you linked against by calling the functions <code>ev_version_major</code> and |
107 | <code>ev_version_minor</code>. If you want, you can compare against the global |
189 | <code>ev_version_minor</code>. If you want, you can compare against the global |
108 | symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the |
190 | symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the |
109 | version of the library your program was compiled against.</p> |
191 | version of the library your program was compiled against.</p> |
110 | <p>Usually, its a good idea to terminate if the major versions mismatch, |
192 | <p>Usually, it's a good idea to terminate if the major versions mismatch, |
111 | as this indicates an incompatible change. Minor versions are usually |
193 | as this indicates an incompatible change. Minor versions are usually |
112 | compatible to older versions, so a larger minor version alone is usually |
194 | compatible to older versions, so a larger minor version alone is usually |
113 | not a problem.</p> |
195 | not a problem.</p> |
|
|
196 | <p>Example: Make sure we haven't accidentally been linked against the wrong |
|
|
197 | version.</p> |
|
|
198 | <pre> assert (("libev version mismatch", |
|
|
199 | ev_version_major () == EV_VERSION_MAJOR |
|
|
200 | && ev_version_minor () >= EV_VERSION_MINOR)); |
|
|
201 | |
|
|
202 | </pre> |
|
|
203 | </dd> |
|
|
204 | <dt>unsigned int ev_supported_backends ()</dt> |
|
|
205 | <dd> |
|
|
206 | <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code> |
|
|
207 | value) compiled into this binary of libev (independent of their |
|
|
208 | availability on the system you are running on). See <code>ev_default_loop</code> for |
|
|
209 | a description of the set values.</p> |
|
|
210 | <p>Example: make sure we have the epoll method, because yeah this is cool and |
|
|
211 | a must have and can we have a torrent of it please!!!11</p> |
|
|
212 | <pre> assert (("sorry, no epoll, no sex", |
|
|
213 | ev_supported_backends () & EVBACKEND_EPOLL)); |
|
|
214 | |
|
|
215 | </pre> |
|
|
216 | </dd> |
|
|
217 | <dt>unsigned int ev_recommended_backends ()</dt> |
|
|
218 | <dd> |
|
|
219 | <p>Return the set of all backends compiled into this binary of libev and also |
|
|
220 | recommended for this platform. This set is often smaller than the one |
|
|
221 | returned by <code>ev_supported_backends</code>, as for example kqueue is broken on |
|
|
222 | most BSDs and will not be autodetected unless you explicitly request it |
|
|
223 | (assuming you know what you are doing). This is the set of backends that |
|
|
224 | libev will probe for if you specify no backends explicitly.</p> |
|
|
225 | </dd> |
|
|
226 | <dt>unsigned int ev_embeddable_backends ()</dt> |
|
|
227 | <dd> |
|
|
228 | <p>Returns the set of backends that are embeddable in other event loops. This |
|
|
229 | is the theoretical, all-platform, value. To find which backends |
|
|
230 | might be supported on the current system, you would need to look at |
|
|
231 | <code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for |
|
|
232 | recommended ones.</p> |
|
|
233 | <p>See the description of <code>ev_embed</code> watchers for more info.</p> |
114 | </dd> |
234 | </dd> |
115 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
235 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
116 | <dd> |
236 | <dd> |
117 | <p>Sets the allocation function to use (the prototype is similar to the |
237 | <p>Sets the allocation function to use (the prototype is similar - the |
118 | realloc function). It is used to allocate and free memory (no surprises |
238 | semantics is identical - to the realloc C function). It is used to |
119 | here). If it returns zero when memory needs to be allocated, the library |
239 | allocate and free memory (no surprises here). If it returns zero when |
120 | might abort or take some potentially destructive action. The default is |
240 | memory needs to be allocated, the library might abort or take some |
121 | your system realloc function.</p> |
241 | potentially destructive action. The default is your system realloc |
|
|
242 | function.</p> |
122 | <p>You could override this function in high-availability programs to, say, |
243 | <p>You could override this function in high-availability programs to, say, |
123 | free some memory if it cannot allocate memory, to use a special allocator, |
244 | free some memory if it cannot allocate memory, to use a special allocator, |
124 | or even to sleep a while and retry until some memory is available.</p> |
245 | or even to sleep a while and retry until some memory is available.</p> |
|
|
246 | <p>Example: Replace the libev allocator with one that waits a bit and then |
|
|
247 | retries).</p> |
|
|
248 | <pre> static void * |
|
|
249 | persistent_realloc (void *ptr, size_t size) |
|
|
250 | { |
|
|
251 | for (;;) |
|
|
252 | { |
|
|
253 | void *newptr = realloc (ptr, size); |
|
|
254 | |
|
|
255 | if (newptr) |
|
|
256 | return newptr; |
|
|
257 | |
|
|
258 | sleep (60); |
|
|
259 | } |
|
|
260 | } |
|
|
261 | |
|
|
262 | ... |
|
|
263 | ev_set_allocator (persistent_realloc); |
|
|
264 | |
|
|
265 | </pre> |
125 | </dd> |
266 | </dd> |
126 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
267 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
127 | <dd> |
268 | <dd> |
128 | <p>Set the callback function to call on a retryable syscall error (such |
269 | <p>Set the callback function to call on a retryable syscall error (such |
129 | as failed select, poll, epoll_wait). The message is a printable string |
270 | as failed select, poll, epoll_wait). The message is a printable string |
130 | indicating the system call or subsystem causing the problem. If this |
271 | indicating the system call or subsystem causing the problem. If this |
131 | callback is set, then libev will expect it to remedy the sitution, no |
272 | callback is set, then libev will expect it to remedy the sitution, no |
132 | matter what, when it returns. That is, libev will geenrally retry the |
273 | matter what, when it returns. That is, libev will generally retry the |
133 | requested operation, or, if the condition doesn't go away, do bad stuff |
274 | requested operation, or, if the condition doesn't go away, do bad stuff |
134 | (such as abort).</p> |
275 | (such as abort).</p> |
|
|
276 | <p>Example: This is basically the same thing that libev does internally, too.</p> |
|
|
277 | <pre> static void |
|
|
278 | fatal_error (const char *msg) |
|
|
279 | { |
|
|
280 | perror (msg); |
|
|
281 | abort (); |
|
|
282 | } |
|
|
283 | |
|
|
284 | ... |
|
|
285 | ev_set_syserr_cb (fatal_error); |
|
|
286 | |
|
|
287 | </pre> |
135 | </dd> |
288 | </dd> |
136 | </dl> |
289 | </dl> |
137 | |
290 | |
138 | </div> |
291 | </div> |
139 | <h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> |
292 | <h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1> |
140 | <div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> |
293 | <div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> |
141 | <p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two |
294 | <p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two |
142 | types of such loops, the <i>default</i> loop, which supports signals and child |
295 | types of such loops, the <i>default</i> loop, which supports signals and child |
143 | events, and dynamically created loops which do not.</p> |
296 | events, and dynamically created loops which do not.</p> |
144 | <p>If you use threads, a common model is to run the default event loop |
297 | <p>If you use threads, a common model is to run the default event loop |
145 | in your main thread (or in a separate thrad) and for each thread you |
298 | in your main thread (or in a separate thread) and for each thread you |
146 | create, you also create another event loop. Libev itself does no lockign |
299 | create, you also create another event loop. Libev itself does no locking |
147 | whatsoever, so if you mix calls to different event loops, make sure you |
300 | whatsoever, so if you mix calls to the same event loop in different |
148 | lock (this is usually a bad idea, though, even if done right).</p> |
301 | threads, make sure you lock (this is usually a bad idea, though, even if |
|
|
302 | done correctly, because it's hideous and inefficient).</p> |
149 | <dl> |
303 | <dl> |
150 | <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> |
304 | <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> |
151 | <dd> |
305 | <dd> |
152 | <p>This will initialise the default event loop if it hasn't been initialised |
306 | <p>This will initialise the default event loop if it hasn't been initialised |
153 | yet and return it. If the default loop could not be initialised, returns |
307 | yet and return it. If the default loop could not be initialised, returns |
154 | false. If it already was initialised it simply returns it (and ignores the |
308 | false. If it already was initialised it simply returns it (and ignores the |
155 | flags).</p> |
309 | flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p> |
156 | <p>If you don't know what event loop to use, use the one returned from this |
310 | <p>If you don't know what event loop to use, use the one returned from this |
157 | function.</p> |
311 | function.</p> |
158 | <p>The flags argument can be used to specify special behaviour or specific |
312 | <p>The flags argument can be used to specify special behaviour or specific |
159 | backends to use, and is usually specified as 0 (or EVFLAG_AUTO)</p> |
313 | backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p> |
160 | <p>It supports the following flags:</p> |
314 | <p>The following flags are supported:</p> |
161 | <p> |
315 | <p> |
162 | <dl> |
316 | <dl> |
163 | <dt>EVFLAG_AUTO</dt> |
317 | <dt><code>EVFLAG_AUTO</code></dt> |
164 | <dd> |
318 | <dd> |
165 | <p>The default flags value. Use this if you have no clue (its the right |
319 | <p>The default flags value. Use this if you have no clue (it's the right |
166 | thing, believe me).</p> |
320 | thing, believe me).</p> |
167 | </dd> |
321 | </dd> |
168 | <dt>EVFLAG_NOENV</dt> |
322 | <dt><code>EVFLAG_NOENV</code></dt> |
169 | <dd> |
323 | <dd> |
170 | <p>If this flag bit is ored into the flag value then libev will <i>not</i> look |
324 | <p>If this flag bit is ored into the flag value (or the program runs setuid |
171 | at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this |
325 | or setgid) then libev will <i>not</i> look at the environment variable |
172 | environment variable will override the flags completely. This is useful |
326 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
|
|
327 | override the flags completely if it is found in the environment. This is |
173 | to try out specific backends to tets their performance, or to work around |
328 | useful to try out specific backends to test their performance, or to work |
174 | bugs.</p> |
329 | around bugs.</p> |
175 | </dd> |
330 | </dd> |
176 | <dt>EVMETHOD_SELECT portable select backend</dt> |
331 | <dt><code>EVFLAG_FORKCHECK</code></dt> |
177 | <dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt> |
|
|
178 | <dt>EVMETHOD_EPOLL linux only</dt> |
|
|
179 | <dt>EVMETHOD_KQUEUE some bsds only</dt> |
|
|
180 | <dt>EVMETHOD_DEVPOLL solaris 8 only</dt> |
|
|
181 | <dt>EVMETHOD_PORT solaris 10 only</dt> |
|
|
182 | <dd> |
332 | <dd> |
183 | <p>If one or more of these are ored into the flags value, then only these |
333 | <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after |
184 | backends will be tried (in the reverse order as given here). If one are |
334 | a fork, you can also make libev check for a fork in each iteration by |
185 | specified, any backend will do.</p> |
335 | enabling this flag.</p> |
|
|
336 | <p>This works by calling <code>getpid ()</code> on every iteration of the loop, |
|
|
337 | and thus this might slow down your event loop if you do a lot of loop |
|
|
338 | iterations and little real work, but is usually not noticeable (on my |
|
|
339 | Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence |
|
|
340 | without a syscall and thus <i>very</i> fast, but my Linux system also has |
|
|
341 | <code>pthread_atfork</code> which is even faster).</p> |
|
|
342 | <p>The big advantage of this flag is that you can forget about fork (and |
|
|
343 | forget about forgetting to tell libev about forking) when you use this |
|
|
344 | flag.</p> |
|
|
345 | <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code> |
|
|
346 | environment variable.</p> |
|
|
347 | </dd> |
|
|
348 | <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> |
|
|
349 | <dd> |
|
|
350 | <p>This is your standard select(2) backend. Not <i>completely</i> standard, as |
|
|
351 | libev tries to roll its own fd_set with no limits on the number of fds, |
|
|
352 | but if that fails, expect a fairly low limit on the number of fds when |
|
|
353 | using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
|
|
354 | the fastest backend for a low number of fds.</p> |
|
|
355 | </dd> |
|
|
356 | <dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt> |
|
|
357 | <dd> |
|
|
358 | <p>And this is your standard poll(2) backend. It's more complicated than |
|
|
359 | select, but handles sparse fds better and has no artificial limit on the |
|
|
360 | number of fds you can use (except it will slow down considerably with a |
|
|
361 | lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p> |
|
|
362 | </dd> |
|
|
363 | <dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt> |
|
|
364 | <dd> |
|
|
365 | <p>For few fds, this backend is a bit little slower than poll and select, |
|
|
366 | but it scales phenomenally better. While poll and select usually scale like |
|
|
367 | O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
|
|
368 | either O(1) or O(active_fds).</p> |
|
|
369 | <p>While stopping and starting an I/O watcher in the same iteration will |
|
|
370 | result in some caching, there is still a syscall per such incident |
|
|
371 | (because the fd could point to a different file description now), so its |
|
|
372 | best to avoid that. Also, dup()ed file descriptors might not work very |
|
|
373 | well if you register events for both fds.</p> |
|
|
374 | <p>Please note that epoll sometimes generates spurious notifications, so you |
|
|
375 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
376 | (or space) is available.</p> |
|
|
377 | </dd> |
|
|
378 | <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt> |
|
|
379 | <dd> |
|
|
380 | <p>Kqueue deserves special mention, as at the time of this writing, it |
|
|
381 | was broken on all BSDs except NetBSD (usually it doesn't work with |
|
|
382 | anything but sockets and pipes, except on Darwin, where of course its |
|
|
383 | completely useless). For this reason its not being "autodetected" |
|
|
384 | unless you explicitly specify it explicitly in the flags (i.e. using |
|
|
385 | <code>EVBACKEND_KQUEUE</code>).</p> |
|
|
386 | <p>It scales in the same way as the epoll backend, but the interface to the |
|
|
387 | kernel is more efficient (which says nothing about its actual speed, of |
|
|
388 | course). While starting and stopping an I/O watcher does not cause an |
|
|
389 | extra syscall as with epoll, it still adds up to four event changes per |
|
|
390 | incident, so its best to avoid that.</p> |
|
|
391 | </dd> |
|
|
392 | <dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt> |
|
|
393 | <dd> |
|
|
394 | <p>This is not implemented yet (and might never be).</p> |
|
|
395 | </dd> |
|
|
396 | <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt> |
|
|
397 | <dd> |
|
|
398 | <p>This uses the Solaris 10 port mechanism. As with everything on Solaris, |
|
|
399 | it's really slow, but it still scales very well (O(active_fds)).</p> |
|
|
400 | <p>Please note that solaris ports can result in a lot of spurious |
|
|
401 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
402 | blocking when no data (or space) is available.</p> |
|
|
403 | </dd> |
|
|
404 | <dt><code>EVBACKEND_ALL</code></dt> |
|
|
405 | <dd> |
|
|
406 | <p>Try all backends (even potentially broken ones that wouldn't be tried |
|
|
407 | with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as |
|
|
408 | <code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p> |
186 | </dd> |
409 | </dd> |
187 | </dl> |
410 | </dl> |
188 | </p> |
411 | </p> |
|
|
412 | <p>If one or more of these are ored into the flags value, then only these |
|
|
413 | backends will be tried (in the reverse order as given here). If none are |
|
|
414 | specified, most compiled-in backend will be tried, usually in reverse |
|
|
415 | order of their flag values :)</p> |
|
|
416 | <p>The most typical usage is like this:</p> |
|
|
417 | <pre> if (!ev_default_loop (0)) |
|
|
418 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
419 | |
|
|
420 | </pre> |
|
|
421 | <p>Restrict libev to the select and poll backends, and do not allow |
|
|
422 | environment settings to be taken into account:</p> |
|
|
423 | <pre> ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
424 | |
|
|
425 | </pre> |
|
|
426 | <p>Use whatever libev has to offer, but make sure that kqueue is used if |
|
|
427 | available (warning, breaks stuff, best use only with your own private |
|
|
428 | event loop and only if you know the OS supports your types of fds):</p> |
|
|
429 | <pre> ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
430 | |
|
|
431 | </pre> |
189 | </dd> |
432 | </dd> |
190 | <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> |
433 | <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> |
191 | <dd> |
434 | <dd> |
192 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
435 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
193 | always distinct from the default loop. Unlike the default loop, it cannot |
436 | always distinct from the default loop. Unlike the default loop, it cannot |
194 | handle signal and child watchers, and attempts to do so will be greeted by |
437 | handle signal and child watchers, and attempts to do so will be greeted by |
195 | undefined behaviour (or a failed assertion if assertions are enabled).</p> |
438 | undefined behaviour (or a failed assertion if assertions are enabled).</p> |
|
|
439 | <p>Example: Try to create a event loop that uses epoll and nothing else.</p> |
|
|
440 | <pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
|
|
441 | if (!epoller) |
|
|
442 | fatal ("no epoll found here, maybe it hides under your chair"); |
|
|
443 | |
|
|
444 | </pre> |
196 | </dd> |
445 | </dd> |
197 | <dt>ev_default_destroy ()</dt> |
446 | <dt>ev_default_destroy ()</dt> |
198 | <dd> |
447 | <dd> |
199 | <p>Destroys the default loop again (frees all memory and kernel state |
448 | <p>Destroys the default loop again (frees all memory and kernel state |
200 | etc.). This stops all registered event watchers (by not touching them in |
449 | etc.). None of the active event watchers will be stopped in the normal |
201 | any way whatsoever, although you cnanot rely on this :).</p> |
450 | sense, so e.g. <code>ev_is_active</code> might still return true. It is your |
|
|
451 | responsibility to either stop all watchers cleanly yoursef <i>before</i> |
|
|
452 | calling this function, or cope with the fact afterwards (which is usually |
|
|
453 | the easiest thing, youc na just ignore the watchers and/or <code>free ()</code> them |
|
|
454 | for example).</p> |
202 | </dd> |
455 | </dd> |
203 | <dt>ev_loop_destroy (loop)</dt> |
456 | <dt>ev_loop_destroy (loop)</dt> |
204 | <dd> |
457 | <dd> |
205 | <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an |
458 | <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an |
206 | earlier call to <code>ev_loop_new</code>.</p> |
459 | earlier call to <code>ev_loop_new</code>.</p> |
… | |
… | |
209 | <dd> |
462 | <dd> |
210 | <p>This function reinitialises the kernel state for backends that have |
463 | <p>This function reinitialises the kernel state for backends that have |
211 | one. Despite the name, you can call it anytime, but it makes most sense |
464 | one. Despite the name, you can call it anytime, but it makes most sense |
212 | after forking, in either the parent or child process (or both, but that |
465 | after forking, in either the parent or child process (or both, but that |
213 | again makes little sense).</p> |
466 | again makes little sense).</p> |
214 | <p>You <i>must</i> call this function after forking if and only if you want to |
467 | <p>You <i>must</i> call this function in the child process after forking if and |
215 | use the event library in both processes. If you just fork+exec, you don't |
468 | only if you want to use the event library in both processes. If you just |
216 | have to call it.</p> |
469 | fork+exec, you don't have to call it.</p> |
217 | <p>The function itself is quite fast and its usually not a problem to call |
470 | <p>The function itself is quite fast and it's usually not a problem to call |
218 | it just in case after a fork. To make this easy, the function will fit in |
471 | it just in case after a fork. To make this easy, the function will fit in |
219 | quite nicely into a call to <code>pthread_atfork</code>:</p> |
472 | quite nicely into a call to <code>pthread_atfork</code>:</p> |
220 | <pre> pthread_atfork (0, 0, ev_default_fork); |
473 | <pre> pthread_atfork (0, 0, ev_default_fork); |
221 | |
474 | |
222 | </pre> |
475 | </pre> |
|
|
476 | <p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use |
|
|
477 | without calling this function, so if you force one of those backends you |
|
|
478 | do not need to care.</p> |
223 | </dd> |
479 | </dd> |
224 | <dt>ev_loop_fork (loop)</dt> |
480 | <dt>ev_loop_fork (loop)</dt> |
225 | <dd> |
481 | <dd> |
226 | <p>Like <code>ev_default_fork</code>, but acts on an event loop created by |
482 | <p>Like <code>ev_default_fork</code>, but acts on an event loop created by |
227 | <code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop |
483 | <code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop |
228 | after fork, and how you do this is entirely your own problem.</p> |
484 | after fork, and how you do this is entirely your own problem.</p> |
229 | </dd> |
485 | </dd> |
230 | <dt>unsigned int ev_method (loop)</dt> |
486 | <dt>unsigned int ev_loop_count (loop)</dt> |
|
|
487 | <dd> |
|
|
488 | <p>Returns the count of loop iterations for the loop, which is identical to |
|
|
489 | the number of times libev did poll for new events. It starts at <code>0</code> and |
|
|
490 | happily wraps around with enough iterations.</p> |
|
|
491 | <p>This value can sometimes be useful as a generation counter of sorts (it |
|
|
492 | "ticks" the number of loop iterations), as it roughly corresponds with |
|
|
493 | <code>ev_prepare</code> and <code>ev_check</code> calls.</p> |
231 | <dd> |
494 | </dd> |
|
|
495 | <dt>unsigned int ev_backend (loop)</dt> |
|
|
496 | <dd> |
232 | <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in |
497 | <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in |
233 | use.</p> |
498 | use.</p> |
234 | </dd> |
499 | </dd> |
235 | <dt>ev_tstamp = ev_now (loop)</dt> |
500 | <dt>ev_tstamp ev_now (loop)</dt> |
236 | <dd> |
501 | <dd> |
237 | <p>Returns the current "event loop time", which is the time the event loop |
502 | <p>Returns the current "event loop time", which is the time the event loop |
238 | got events and started processing them. This timestamp does not change |
503 | received events and started processing them. This timestamp does not |
239 | as long as callbacks are being processed, and this is also the base time |
504 | change as long as callbacks are being processed, and this is also the base |
240 | used for relative timers. You can treat it as the timestamp of the event |
505 | time used for relative timers. You can treat it as the timestamp of the |
241 | occuring (or more correctly, the mainloop finding out about it).</p> |
506 | event occuring (or more correctly, libev finding out about it).</p> |
242 | </dd> |
507 | </dd> |
243 | <dt>ev_loop (loop, int flags)</dt> |
508 | <dt>ev_loop (loop, int flags)</dt> |
244 | <dd> |
509 | <dd> |
245 | <p>Finally, this is it, the event handler. This function usually is called |
510 | <p>Finally, this is it, the event handler. This function usually is called |
246 | after you initialised all your watchers and you want to start handling |
511 | after you initialised all your watchers and you want to start handling |
247 | events.</p> |
512 | events.</p> |
248 | <p>If the flags argument is specified as 0, it will not return until either |
513 | <p>If the flags argument is specified as <code>0</code>, it will not return until |
249 | no event watchers are active anymore or <code>ev_unloop</code> was called.</p> |
514 | either no event watchers are active anymore or <code>ev_unloop</code> was called.</p> |
|
|
515 | <p>Please note that an explicit <code>ev_unloop</code> is usually better than |
|
|
516 | relying on all watchers to be stopped when deciding when a program has |
|
|
517 | finished (especially in interactive programs), but having a program that |
|
|
518 | automatically loops as long as it has to and no longer by virtue of |
|
|
519 | relying on its watchers stopping correctly is a thing of beauty.</p> |
250 | <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle |
520 | <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle |
251 | those events and any outstanding ones, but will not block your process in |
521 | those events and any outstanding ones, but will not block your process in |
252 | case there are no events.</p> |
522 | case there are no events and will return after one iteration of the loop.</p> |
253 | <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if |
523 | <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if |
254 | neccessary) and will handle those and any outstanding ones. It will block |
524 | neccessary) and will handle those and any outstanding ones. It will block |
255 | your process until at least one new event arrives.</p> |
525 | your process until at least one new event arrives, and will return after |
256 | <p>This flags value could be used to implement alternative looping |
526 | one iteration of the loop. This is useful if you are waiting for some |
257 | constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and |
527 | external event in conjunction with something not expressible using other |
258 | more generic mechanism.</p> |
528 | libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is |
|
|
529 | usually a better approach for this kind of thing.</p> |
|
|
530 | <p>Here are the gory details of what <code>ev_loop</code> does:</p> |
|
|
531 | <pre> * If there are no active watchers (reference count is zero), return. |
|
|
532 | - Queue prepare watchers and then call all outstanding watchers. |
|
|
533 | - If we have been forked, recreate the kernel state. |
|
|
534 | - Update the kernel state with all outstanding changes. |
|
|
535 | - Update the "event loop time". |
|
|
536 | - Calculate for how long to block. |
|
|
537 | - Block the process, waiting for any events. |
|
|
538 | - Queue all outstanding I/O (fd) events. |
|
|
539 | - Update the "event loop time" and do time jump handling. |
|
|
540 | - Queue all outstanding timers. |
|
|
541 | - Queue all outstanding periodics. |
|
|
542 | - If no events are pending now, queue all idle watchers. |
|
|
543 | - Queue all check watchers. |
|
|
544 | - Call all queued watchers in reverse order (i.e. check watchers first). |
|
|
545 | Signals and child watchers are implemented as I/O watchers, and will |
|
|
546 | be handled here by queueing them when their watcher gets executed. |
|
|
547 | - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
|
|
548 | were used, return, otherwise continue with step *. |
|
|
549 | |
|
|
550 | </pre> |
|
|
551 | <p>Example: Queue some jobs and then loop until no events are outsanding |
|
|
552 | anymore.</p> |
|
|
553 | <pre> ... queue jobs here, make sure they register event watchers as long |
|
|
554 | ... as they still have work to do (even an idle watcher will do..) |
|
|
555 | ev_loop (my_loop, 0); |
|
|
556 | ... jobs done. yeah! |
|
|
557 | |
|
|
558 | </pre> |
259 | </dd> |
559 | </dd> |
260 | <dt>ev_unloop (loop, how)</dt> |
560 | <dt>ev_unloop (loop, how)</dt> |
261 | <dd> |
561 | <dd> |
262 | <p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument |
562 | <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it |
|
|
563 | has processed all outstanding events). The <code>how</code> argument must be either |
263 | must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> |
564 | <code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or |
264 | call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> |
565 | <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> |
265 | calls return.</p> |
|
|
266 | </dd> |
566 | </dd> |
267 | <dt>ev_ref (loop)</dt> |
567 | <dt>ev_ref (loop)</dt> |
268 | <dt>ev_unref (loop)</dt> |
568 | <dt>ev_unref (loop)</dt> |
269 | <dd> |
569 | <dd> |
270 | <p>Ref/unref can be used to add or remove a refcount on the event loop: Every |
570 | <p>Ref/unref can be used to add or remove a reference count on the event |
271 | watcher keeps one reference. If you have a long-runing watcher you never |
571 | loop: Every watcher keeps one reference, and as long as the reference |
272 | unregister that should not keep ev_loop from running, ev_unref() after |
572 | count is nonzero, <code>ev_loop</code> will not return on its own. If you have |
273 | starting, and ev_ref() before stopping it. Libev itself uses this for |
573 | a watcher you never unregister that should not keep <code>ev_loop</code> from |
274 | example for its internal signal pipe: It is not visible to you as a user |
574 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
275 | and should not keep <code>ev_loop</code> from exiting if the work is done. It is |
575 | example, libev itself uses this for its internal signal pipe: It is not |
276 | also an excellent way to do this for generic recurring timers or from |
576 | visible to the libev user and should not keep <code>ev_loop</code> from exiting if |
277 | within third-party libraries. Just remember to unref after start and ref |
577 | no event watchers registered by it are active. It is also an excellent |
278 | before stop.</p> |
578 | way to do this for generic recurring timers or from within third-party |
|
|
579 | libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> |
|
|
580 | <p>Example: Create a signal watcher, but keep it from keeping <code>ev_loop</code> |
|
|
581 | running when nothing else is active.</p> |
|
|
582 | <pre> struct ev_signal exitsig; |
|
|
583 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
|
|
584 | ev_signal_start (loop, &exitsig); |
|
|
585 | evf_unref (loop); |
|
|
586 | |
|
|
587 | </pre> |
|
|
588 | <p>Example: For some weird reason, unregister the above signal handler again.</p> |
|
|
589 | <pre> ev_ref (loop); |
|
|
590 | ev_signal_stop (loop, &exitsig); |
|
|
591 | |
|
|
592 | </pre> |
279 | </dd> |
593 | </dd> |
280 | </dl> |
594 | </dl> |
281 | |
595 | |
|
|
596 | |
|
|
597 | |
|
|
598 | |
|
|
599 | |
282 | </div> |
600 | </div> |
283 | <h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> |
601 | <h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1> |
284 | <div id="ANATOMY_OF_A_WATCHER_CONTENT"> |
602 | <div id="ANATOMY_OF_A_WATCHER_CONTENT"> |
285 | <p>A watcher is a structure that you create and register to record your |
603 | <p>A watcher is a structure that you create and register to record your |
286 | interest in some event. For instance, if you want to wait for STDIN to |
604 | interest in some event. For instance, if you want to wait for STDIN to |
287 | become readable, you would create an ev_io watcher for that:</p> |
605 | become readable, you would create an <code>ev_io</code> watcher for that:</p> |
288 | <pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
606 | <pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
289 | { |
607 | { |
290 | ev_io_stop (w); |
608 | ev_io_stop (w); |
291 | ev_unloop (loop, EVUNLOOP_ALL); |
609 | ev_unloop (loop, EVUNLOOP_ALL); |
292 | } |
610 | } |
… | |
… | |
315 | with a watcher-specific start function (<code>ev_<type>_start (loop, watcher |
633 | with a watcher-specific start function (<code>ev_<type>_start (loop, watcher |
316 | *)</code>), and you can stop watching for events at any time by calling the |
634 | *)</code>), and you can stop watching for events at any time by calling the |
317 | corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p> |
635 | corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p> |
318 | <p>As long as your watcher is active (has been started but not stopped) you |
636 | <p>As long as your watcher is active (has been started but not stopped) you |
319 | must not touch the values stored in it. Most specifically you must never |
637 | must not touch the values stored in it. Most specifically you must never |
320 | reinitialise it or call its set method.</p> |
638 | reinitialise it or call its <code>set</code> macro.</p> |
321 | <p>You cna check wether an event is active by calling the <code>ev_is_active |
|
|
322 | (watcher *)</code> macro. To see wether an event is outstanding (but the |
|
|
323 | callback for it has not been called yet) you cna use the <code>ev_is_pending |
|
|
324 | (watcher *)</code> macro.</p> |
|
|
325 | <p>Each and every callback receives the event loop pointer as first, the |
639 | <p>Each and every callback receives the event loop pointer as first, the |
326 | registered watcher structure as second, and a bitset of received events as |
640 | registered watcher structure as second, and a bitset of received events as |
327 | third argument.</p> |
641 | third argument.</p> |
328 | <p>The rceeived events usually include a single bit per event type received |
642 | <p>The received events usually include a single bit per event type received |
329 | (you can receive multiple events at the same time). The possible bit masks |
643 | (you can receive multiple events at the same time). The possible bit masks |
330 | are:</p> |
644 | are:</p> |
331 | <dl> |
645 | <dl> |
332 | <dt>EV_READ</dt> |
646 | <dt><code>EV_READ</code></dt> |
333 | <dt>EV_WRITE</dt> |
647 | <dt><code>EV_WRITE</code></dt> |
334 | <dd> |
648 | <dd> |
335 | <p>The file descriptor in the ev_io watcher has become readable and/or |
649 | <p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or |
336 | writable.</p> |
650 | writable.</p> |
337 | </dd> |
651 | </dd> |
338 | <dt>EV_TIMEOUT</dt> |
652 | <dt><code>EV_TIMEOUT</code></dt> |
339 | <dd> |
|
|
340 | <p>The ev_timer watcher has timed out.</p> |
|
|
341 | </dd> |
653 | <dd> |
342 | <dt>EV_PERIODIC</dt> |
654 | <p>The <code>ev_timer</code> watcher has timed out.</p> |
343 | <dd> |
655 | </dd> |
344 | <p>The ev_periodic watcher has timed out.</p> |
656 | <dt><code>EV_PERIODIC</code></dt> |
345 | </dd> |
657 | <dd> |
346 | <dt>EV_SIGNAL</dt> |
658 | <p>The <code>ev_periodic</code> watcher has timed out.</p> |
347 | <dd> |
659 | </dd> |
|
|
660 | <dt><code>EV_SIGNAL</code></dt> |
|
|
661 | <dd> |
348 | <p>The signal specified in the ev_signal watcher has been received by a thread.</p> |
662 | <p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p> |
349 | </dd> |
|
|
350 | <dt>EV_CHILD</dt> |
|
|
351 | <dd> |
663 | </dd> |
|
|
664 | <dt><code>EV_CHILD</code></dt> |
|
|
665 | <dd> |
352 | <p>The pid specified in the ev_child watcher has received a status change.</p> |
666 | <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p> |
353 | </dd> |
|
|
354 | <dt>EV_IDLE</dt> |
|
|
355 | <dd> |
667 | </dd> |
|
|
668 | <dt><code>EV_STAT</code></dt> |
|
|
669 | <dd> |
|
|
670 | <p>The path specified in the <code>ev_stat</code> watcher changed its attributes somehow.</p> |
|
|
671 | </dd> |
|
|
672 | <dt><code>EV_IDLE</code></dt> |
|
|
673 | <dd> |
356 | <p>The ev_idle watcher has determined that you have nothing better to do.</p> |
674 | <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p> |
357 | </dd> |
|
|
358 | <dt>EV_PREPARE</dt> |
|
|
359 | <dt>EV_CHECK</dt> |
|
|
360 | <dd> |
675 | </dd> |
|
|
676 | <dt><code>EV_PREPARE</code></dt> |
|
|
677 | <dt><code>EV_CHECK</code></dt> |
|
|
678 | <dd> |
361 | <p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts |
679 | <p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts |
362 | to gather new events, and all ev_check watchers are invoked just after |
680 | to gather new events, and all <code>ev_check</code> watchers are invoked just after |
363 | <code>ev_loop</code> has gathered them, but before it invokes any callbacks for any |
681 | <code>ev_loop</code> has gathered them, but before it invokes any callbacks for any |
364 | received events. Callbacks of both watcher types can start and stop as |
682 | received events. Callbacks of both watcher types can start and stop as |
365 | many watchers as they want, and all of them will be taken into account |
683 | many watchers as they want, and all of them will be taken into account |
366 | (for example, a ev_prepare watcher might start an idle watcher to keep |
684 | (for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep |
367 | <code>ev_loop</code> from blocking).</p> |
685 | <code>ev_loop</code> from blocking).</p> |
368 | </dd> |
686 | </dd> |
369 | <dt>EV_ERROR</dt> |
687 | <dt><code>EV_EMBED</code></dt> |
|
|
688 | <dd> |
|
|
689 | <p>The embedded event loop specified in the <code>ev_embed</code> watcher needs attention.</p> |
|
|
690 | </dd> |
|
|
691 | <dt><code>EV_FORK</code></dt> |
|
|
692 | <dd> |
|
|
693 | <p>The event loop has been resumed in the child process after fork (see |
|
|
694 | <code>ev_fork</code>).</p> |
|
|
695 | </dd> |
|
|
696 | <dt><code>EV_ERROR</code></dt> |
370 | <dd> |
697 | <dd> |
371 | <p>An unspecified error has occured, the watcher has been stopped. This might |
698 | <p>An unspecified error has occured, the watcher has been stopped. This might |
372 | happen because the watcher could not be properly started because libev |
699 | happen because the watcher could not be properly started because libev |
373 | ran out of memory, a file descriptor was found to be closed or any other |
700 | ran out of memory, a file descriptor was found to be closed or any other |
374 | problem. You best act on it by reporting the problem and somehow coping |
701 | problem. You best act on it by reporting the problem and somehow coping |
… | |
… | |
380 | programs, though, so beware.</p> |
707 | programs, though, so beware.</p> |
381 | </dd> |
708 | </dd> |
382 | </dl> |
709 | </dl> |
383 | |
710 | |
384 | </div> |
711 | </div> |
|
|
712 | <h2 id="GENERIC_WATCHER_FUNCTIONS">GENERIC WATCHER FUNCTIONS</h2> |
|
|
713 | <div id="GENERIC_WATCHER_FUNCTIONS_CONTENT"> |
|
|
714 | <p>In the following description, <code>TYPE</code> stands for the watcher type, |
|
|
715 | e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p> |
|
|
716 | <dl> |
|
|
717 | <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt> |
|
|
718 | <dd> |
|
|
719 | <p>This macro initialises the generic portion of a watcher. The contents |
|
|
720 | of the watcher object can be arbitrary (so <code>malloc</code> will do). Only |
|
|
721 | the generic parts of the watcher are initialised, you <i>need</i> to call |
|
|
722 | the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the |
|
|
723 | type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro |
|
|
724 | which rolls both calls into one.</p> |
|
|
725 | <p>You can reinitialise a watcher at any time as long as it has been stopped |
|
|
726 | (or never started) and there are no pending events outstanding.</p> |
|
|
727 | <p>The callback is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher, |
|
|
728 | int revents)</code>.</p> |
|
|
729 | </dd> |
|
|
730 | <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt> |
|
|
731 | <dd> |
|
|
732 | <p>This macro initialises the type-specific parts of a watcher. You need to |
|
|
733 | call <code>ev_init</code> at least once before you call this macro, but you can |
|
|
734 | call <code>ev_TYPE_set</code> any number of times. You must not, however, call this |
|
|
735 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
736 | difference to the <code>ev_init</code> macro).</p> |
|
|
737 | <p>Although some watcher types do not have type-specific arguments |
|
|
738 | (e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p> |
|
|
739 | </dd> |
|
|
740 | <dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt> |
|
|
741 | <dd> |
|
|
742 | <p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro |
|
|
743 | calls into a single call. This is the most convinient method to initialise |
|
|
744 | a watcher. The same limitations apply, of course.</p> |
|
|
745 | </dd> |
|
|
746 | <dt><code>ev_TYPE_start</code> (loop *, ev_TYPE *watcher)</dt> |
|
|
747 | <dd> |
|
|
748 | <p>Starts (activates) the given watcher. Only active watchers will receive |
|
|
749 | events. If the watcher is already active nothing will happen.</p> |
|
|
750 | </dd> |
|
|
751 | <dt><code>ev_TYPE_stop</code> (loop *, ev_TYPE *watcher)</dt> |
|
|
752 | <dd> |
|
|
753 | <p>Stops the given watcher again (if active) and clears the pending |
|
|
754 | status. It is possible that stopped watchers are pending (for example, |
|
|
755 | non-repeating timers are being stopped when they become pending), but |
|
|
756 | <code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If |
|
|
757 | you want to free or reuse the memory used by the watcher it is therefore a |
|
|
758 | good idea to always call its <code>ev_TYPE_stop</code> function.</p> |
|
|
759 | </dd> |
|
|
760 | <dt>bool ev_is_active (ev_TYPE *watcher)</dt> |
|
|
761 | <dd> |
|
|
762 | <p>Returns a true value iff the watcher is active (i.e. it has been started |
|
|
763 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
764 | it.</p> |
|
|
765 | </dd> |
|
|
766 | <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> |
|
|
767 | <dd> |
|
|
768 | <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
769 | events but its callback has not yet been invoked). As long as a watcher |
|
|
770 | is pending (but not active) you must not call an init function on it (but |
|
|
771 | <code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to |
|
|
772 | libev (e.g. you cnanot <code>free ()</code> it).</p> |
|
|
773 | </dd> |
|
|
774 | <dt>callback ev_cb (ev_TYPE *watcher)</dt> |
|
|
775 | <dd> |
|
|
776 | <p>Returns the callback currently set on the watcher.</p> |
|
|
777 | </dd> |
|
|
778 | <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> |
|
|
779 | <dd> |
|
|
780 | <p>Change the callback. You can change the callback at virtually any time |
|
|
781 | (modulo threads).</p> |
|
|
782 | </dd> |
|
|
783 | <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt> |
|
|
784 | <dt>int ev_priority (ev_TYPE *watcher)</dt> |
|
|
785 | <dd> |
|
|
786 | <p>Set and query the priority of the watcher. The priority is a small |
|
|
787 | integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code> |
|
|
788 | (default: <code>-2</code>). Pending watchers with higher priority will be invoked |
|
|
789 | before watchers with lower priority, but priority will not keep watchers |
|
|
790 | from being executed (except for <code>ev_idle</code> watchers).</p> |
|
|
791 | <p>This means that priorities are <i>only</i> used for ordering callback |
|
|
792 | invocation after new events have been received. This is useful, for |
|
|
793 | example, to reduce latency after idling, or more often, to bind two |
|
|
794 | watchers on the same event and make sure one is called first.</p> |
|
|
795 | <p>If you need to suppress invocation when higher priority events are pending |
|
|
796 | you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p> |
|
|
797 | <p>The default priority used by watchers when no priority has been set is |
|
|
798 | always <code>0</code>, which is supposed to not be too high and not be too low :).</p> |
|
|
799 | <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is |
|
|
800 | fine, as long as you do not mind that the priority value you query might |
|
|
801 | or might not have been adjusted to be within valid range.</p> |
|
|
802 | </dd> |
|
|
803 | </dl> |
|
|
804 | |
|
|
805 | |
|
|
806 | |
|
|
807 | |
|
|
808 | |
|
|
809 | </div> |
385 | <h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> |
810 | <h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> |
386 | <div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> |
811 | <div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> |
387 | <p>Each watcher has, by default, a member <code>void *data</code> that you can change |
812 | <p>Each watcher has, by default, a member <code>void *data</code> that you can change |
388 | and read at any time, libev will completely ignore it. This cna be used |
813 | and read at any time, libev will completely ignore it. This can be used |
389 | to associate arbitrary data with your watcher. If you need more data and |
814 | to associate arbitrary data with your watcher. If you need more data and |
390 | don't want to allocate memory and store a pointer to it in that data |
815 | don't want to allocate memory and store a pointer to it in that data |
391 | member, you can also "subclass" the watcher type and provide your own |
816 | member, you can also "subclass" the watcher type and provide your own |
392 | data:</p> |
817 | data:</p> |
393 | <pre> struct my_io |
818 | <pre> struct my_io |
… | |
… | |
406 | struct my_io *w = (struct my_io *)w_; |
831 | struct my_io *w = (struct my_io *)w_; |
407 | ... |
832 | ... |
408 | } |
833 | } |
409 | |
834 | |
410 | </pre> |
835 | </pre> |
411 | <p>More interesting and less C-conformant ways of catsing your callback type |
836 | <p>More interesting and less C-conformant ways of casting your callback type |
412 | have been omitted....</p> |
837 | instead have been omitted.</p> |
|
|
838 | <p>Another common scenario is having some data structure with multiple |
|
|
839 | watchers:</p> |
|
|
840 | <pre> struct my_biggy |
|
|
841 | { |
|
|
842 | int some_data; |
|
|
843 | ev_timer t1; |
|
|
844 | ev_timer t2; |
|
|
845 | } |
413 | |
846 | |
|
|
847 | </pre> |
|
|
848 | <p>In this case getting the pointer to <code>my_biggy</code> is a bit more complicated, |
|
|
849 | you need to use <code>offsetof</code>:</p> |
|
|
850 | <pre> #include <stddef.h> |
414 | |
851 | |
|
|
852 | static void |
|
|
853 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
|
|
854 | { |
|
|
855 | struct my_biggy big = (struct my_biggy * |
|
|
856 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
857 | } |
415 | |
858 | |
|
|
859 | static void |
|
|
860 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
|
|
861 | { |
|
|
862 | struct my_biggy big = (struct my_biggy * |
|
|
863 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
864 | } |
416 | |
865 | |
417 | |
866 | |
|
|
867 | |
|
|
868 | |
|
|
869 | </pre> |
|
|
870 | |
418 | </div> |
871 | </div> |
419 | <h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> |
872 | <h1 id="WATCHER_TYPES">WATCHER TYPES</h1> |
420 | <div id="WATCHER_TYPES_CONTENT"> |
873 | <div id="WATCHER_TYPES_CONTENT"> |
421 | <p>This section describes each watcher in detail, but will not repeat |
874 | <p>This section describes each watcher in detail, but will not repeat |
422 | information given in the last section.</p> |
875 | information given in the last section. Any initialisation/set macros, |
|
|
876 | functions and members specific to the watcher type are explained.</p> |
|
|
877 | <p>Members are additionally marked with either <i>[read-only]</i>, meaning that, |
|
|
878 | while the watcher is active, you can look at the member and expect some |
|
|
879 | sensible content, but you must not modify it (you can modify it while the |
|
|
880 | watcher is stopped to your hearts content), or <i>[read-write]</i>, which |
|
|
881 | means you can expect it to have some sensible content while the watcher |
|
|
882 | is active, but you can also modify it. Modifying it may not do something |
|
|
883 | sensible or take immediate effect (or do anything at all), but libev will |
|
|
884 | not crash or malfunction in any way.</p> |
423 | |
885 | |
|
|
886 | |
|
|
887 | |
|
|
888 | |
|
|
889 | |
424 | </div> |
890 | </div> |
425 | <h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2> |
891 | <h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable?</h2> |
426 | <div id="struct_ev_io_is_my_file_descriptor_r-2"> |
892 | <div id="code_ev_io_code_is_this_file_descrip-2"> |
427 | <p>I/O watchers check wether a file descriptor is readable or writable |
893 | <p>I/O watchers check whether a file descriptor is readable or writable |
428 | in each iteration of the event loop (This behaviour is called |
894 | in each iteration of the event loop, or, more precisely, when reading |
429 | level-triggering because you keep receiving events as long as the |
895 | would not block the process and writing would at least be able to write |
430 | condition persists. Remember you cna stop the watcher if you don't want to |
896 | some data. This behaviour is called level-triggering because you keep |
431 | act on the event and neither want to receive future events).</p> |
897 | receiving events as long as the condition persists. Remember you can stop |
|
|
898 | the watcher if you don't want to act on the event and neither want to |
|
|
899 | receive future events.</p> |
|
|
900 | <p>In general you can register as many read and/or write event watchers per |
|
|
901 | fd as you want (as long as you don't confuse yourself). Setting all file |
|
|
902 | descriptors to non-blocking mode is also usually a good idea (but not |
|
|
903 | required if you know what you are doing).</p> |
|
|
904 | <p>You have to be careful with dup'ed file descriptors, though. Some backends |
|
|
905 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
|
|
906 | descriptors correctly if you register interest in two or more fds pointing |
|
|
907 | to the same underlying file/socket/etc. description (that is, they share |
|
|
908 | the same underlying "file open").</p> |
|
|
909 | <p>If you must do this, then force the use of a known-to-be-good backend |
|
|
910 | (at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and |
|
|
911 | <code>EVBACKEND_POLL</code>).</p> |
|
|
912 | <p>Another thing you have to watch out for is that it is quite easy to |
|
|
913 | receive "spurious" readyness notifications, that is your callback might |
|
|
914 | be called with <code>EV_READ</code> but a subsequent <code>read</code>(2) will actually block |
|
|
915 | because there is no data. Not only are some backends known to create a |
|
|
916 | lot of those (for example solaris ports), it is very easy to get into |
|
|
917 | this situation even with a relatively standard program structure. Thus |
|
|
918 | it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning |
|
|
919 | <code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> |
|
|
920 | <p>If you cannot run the fd in non-blocking mode (for example you should not |
|
|
921 | play around with an Xlib connection), then you have to seperately re-test |
|
|
922 | wether a file descriptor is really ready with a known-to-be good interface |
|
|
923 | such as poll (fortunately in our Xlib example, Xlib already does this on |
|
|
924 | its own, so its quite safe to use).</p> |
432 | <dl> |
925 | <dl> |
433 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
926 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
434 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
927 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
435 | <dd> |
928 | <dd> |
436 | <p>Configures an ev_io watcher. The fd is the file descriptor to rceeive |
929 | <p>Configures an <code>ev_io</code> watcher. The <code>fd</code> is the file descriptor to |
437 | events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | |
930 | rceeive events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or |
438 | EV_WRITE</code> to receive the given events.</p> |
931 | <code>EV_READ | EV_WRITE</code> to receive the given events.</p> |
|
|
932 | </dd> |
|
|
933 | <dt>int fd [read-only]</dt> |
|
|
934 | <dd> |
|
|
935 | <p>The file descriptor being watched.</p> |
|
|
936 | </dd> |
|
|
937 | <dt>int events [read-only]</dt> |
|
|
938 | <dd> |
|
|
939 | <p>The events being watched.</p> |
439 | </dd> |
940 | </dd> |
440 | </dl> |
941 | </dl> |
|
|
942 | <p>Example: Call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well |
|
|
943 | readable, but only once. Since it is likely line-buffered, you could |
|
|
944 | attempt to read a whole line in the callback.</p> |
|
|
945 | <pre> static void |
|
|
946 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
|
|
947 | { |
|
|
948 | ev_io_stop (loop, w); |
|
|
949 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
|
|
950 | } |
441 | |
951 | |
|
|
952 | ... |
|
|
953 | struct ev_loop *loop = ev_default_init (0); |
|
|
954 | struct ev_io stdin_readable; |
|
|
955 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
|
|
956 | ev_io_start (loop, &stdin_readable); |
|
|
957 | ev_loop (loop, 0); |
|
|
958 | |
|
|
959 | |
|
|
960 | |
|
|
961 | |
|
|
962 | </pre> |
|
|
963 | |
442 | </div> |
964 | </div> |
443 | <h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2> |
965 | <h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally repeating timeouts</h2> |
444 | <div id="struct_ev_timer_relative_and_optiona-2"> |
966 | <div id="code_ev_timer_code_relative_and_opti-2"> |
445 | <p>Timer watchers are simple relative timers that generate an event after a |
967 | <p>Timer watchers are simple relative timers that generate an event after a |
446 | given time, and optionally repeating in regular intervals after that.</p> |
968 | given time, and optionally repeating in regular intervals after that.</p> |
447 | <p>The timers are based on real time, that is, if you register an event that |
969 | <p>The timers are based on real time, that is, if you register an event that |
448 | times out after an hour and youreset your system clock to last years |
970 | times out after an hour and you reset your system clock to last years |
449 | time, it will still time out after (roughly) and hour. "Roughly" because |
971 | time, it will still time out after (roughly) and hour. "Roughly" because |
450 | detecting time jumps is hard, and soem inaccuracies are unavoidable (the |
972 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
451 | monotonic clock option helps a lot here).</p> |
973 | monotonic clock option helps a lot here).</p> |
|
|
974 | <p>The relative timeouts are calculated relative to the <code>ev_now ()</code> |
|
|
975 | time. This is usually the right thing as this timestamp refers to the time |
|
|
976 | of the event triggering whatever timeout you are modifying/starting. If |
|
|
977 | you suspect event processing to be delayed and you <i>need</i> to base the timeout |
|
|
978 | on the current time, use something like this to adjust for this:</p> |
|
|
979 | <pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
|
|
980 | |
|
|
981 | </pre> |
|
|
982 | <p>The callback is guarenteed to be invoked only when its timeout has passed, |
|
|
983 | but if multiple timers become ready during the same loop iteration then |
|
|
984 | order of execution is undefined.</p> |
452 | <dl> |
985 | <dl> |
453 | <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> |
986 | <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> |
454 | <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> |
987 | <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> |
455 | <dd> |
988 | <dd> |
456 | <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is |
989 | <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is |
… | |
… | |
458 | timer will automatically be configured to trigger again <code>repeat</code> seconds |
991 | timer will automatically be configured to trigger again <code>repeat</code> seconds |
459 | later, again, and again, until stopped manually.</p> |
992 | later, again, and again, until stopped manually.</p> |
460 | <p>The timer itself will do a best-effort at avoiding drift, that is, if you |
993 | <p>The timer itself will do a best-effort at avoiding drift, that is, if you |
461 | configure a timer to trigger every 10 seconds, then it will trigger at |
994 | configure a timer to trigger every 10 seconds, then it will trigger at |
462 | exactly 10 second intervals. If, however, your program cannot keep up with |
995 | exactly 10 second intervals. If, however, your program cannot keep up with |
463 | the timer (ecause it takes longer than those 10 seconds to do stuff) the |
996 | the timer (because it takes longer than those 10 seconds to do stuff) the |
464 | timer will not fire more than once per event loop iteration.</p> |
997 | timer will not fire more than once per event loop iteration.</p> |
465 | </dd> |
998 | </dd> |
466 | <dt>ev_timer_again (loop)</dt> |
999 | <dt>ev_timer_again (loop)</dt> |
467 | <dd> |
1000 | <dd> |
468 | <p>This will act as if the timer timed out and restart it again if it is |
1001 | <p>This will act as if the timer timed out and restart it again if it is |
469 | repeating. The exact semantics are:</p> |
1002 | repeating. The exact semantics are:</p> |
|
|
1003 | <p>If the timer is pending, its pending status is cleared.</p> |
470 | <p>If the timer is started but nonrepeating, stop it.</p> |
1004 | <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p> |
471 | <p>If the timer is repeating, either start it if necessary (with the repeat |
1005 | <p>If the timer is repeating, either start it if necessary (with the |
472 | value), or reset the running timer to the repeat value.</p> |
1006 | <code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p> |
473 | <p>This sounds a bit complicated, but here is a useful and typical |
1007 | <p>This sounds a bit complicated, but here is a useful and typical |
474 | example: Imagine you have a tcp connection and you want a so-called idle |
1008 | example: Imagine you have a tcp connection and you want a so-called idle |
475 | timeout, that is, you want to be called when there have been, say, 60 |
1009 | timeout, that is, you want to be called when there have been, say, 60 |
476 | seconds of inactivity on the socket. The easiest way to do this is to |
1010 | seconds of inactivity on the socket. The easiest way to do this is to |
477 | configure an ev_timer with after=repeat=60 and calling ev_timer_again each |
1011 | configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call |
478 | time you successfully read or write some data. If you go into an idle |
1012 | <code>ev_timer_again</code> each time you successfully read or write some data. If |
479 | state where you do not expect data to travel on the socket, you can stop |
1013 | you go into an idle state where you do not expect data to travel on the |
|
|
1014 | socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will |
480 | the timer, and again will automatically restart it if need be.</p> |
1015 | automatically restart it if need be.</p> |
|
|
1016 | <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code> |
|
|
1017 | altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p> |
|
|
1018 | <pre> ev_timer_init (timer, callback, 0., 5.); |
|
|
1019 | ev_timer_again (loop, timer); |
|
|
1020 | ... |
|
|
1021 | timer->again = 17.; |
|
|
1022 | ev_timer_again (loop, timer); |
|
|
1023 | ... |
|
|
1024 | timer->again = 10.; |
|
|
1025 | ev_timer_again (loop, timer); |
|
|
1026 | |
|
|
1027 | </pre> |
|
|
1028 | <p>This is more slightly efficient then stopping/starting the timer each time |
|
|
1029 | you want to modify its timeout value.</p> |
|
|
1030 | </dd> |
|
|
1031 | <dt>ev_tstamp repeat [read-write]</dt> |
|
|
1032 | <dd> |
|
|
1033 | <p>The current <code>repeat</code> value. Will be used each time the watcher times out |
|
|
1034 | or <code>ev_timer_again</code> is called and determines the next timeout (if any), |
|
|
1035 | which is also when any modifications are taken into account.</p> |
481 | </dd> |
1036 | </dd> |
482 | </dl> |
1037 | </dl> |
|
|
1038 | <p>Example: Create a timer that fires after 60 seconds.</p> |
|
|
1039 | <pre> static void |
|
|
1040 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
|
|
1041 | { |
|
|
1042 | .. one minute over, w is actually stopped right here |
|
|
1043 | } |
483 | |
1044 | |
|
|
1045 | struct ev_timer mytimer; |
|
|
1046 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
|
|
1047 | ev_timer_start (loop, &mytimer); |
|
|
1048 | |
|
|
1049 | </pre> |
|
|
1050 | <p>Example: Create a timeout timer that times out after 10 seconds of |
|
|
1051 | inactivity.</p> |
|
|
1052 | <pre> static void |
|
|
1053 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
|
|
1054 | { |
|
|
1055 | .. ten seconds without any activity |
|
|
1056 | } |
|
|
1057 | |
|
|
1058 | struct ev_timer mytimer; |
|
|
1059 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
|
|
1060 | ev_timer_again (&mytimer); /* start timer */ |
|
|
1061 | ev_loop (loop, 0); |
|
|
1062 | |
|
|
1063 | // and in some piece of code that gets executed on any "activity": |
|
|
1064 | // reset the timeout to start ticking again at 10 seconds |
|
|
1065 | ev_timer_again (&mytimer); |
|
|
1066 | |
|
|
1067 | |
|
|
1068 | |
|
|
1069 | |
|
|
1070 | </pre> |
|
|
1071 | |
484 | </div> |
1072 | </div> |
485 | <h2 id="ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</h2> |
1073 | <h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron?</h2> |
486 | <div id="ev_periodic_to_cron_or_not_to_cron_i-2"> |
1074 | <div id="code_ev_periodic_code_to_cron_or_not-2"> |
487 | <p>Periodic watchers are also timers of a kind, but they are very versatile |
1075 | <p>Periodic watchers are also timers of a kind, but they are very versatile |
488 | (and unfortunately a bit complex).</p> |
1076 | (and unfortunately a bit complex).</p> |
489 | <p>Unlike ev_timer's, they are not based on real time (or relative time) |
1077 | <p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) |
490 | but on wallclock time (absolute time). You can tell a periodic watcher |
1078 | but on wallclock time (absolute time). You can tell a periodic watcher |
491 | to trigger "at" some specific point in time. For example, if you tell a |
1079 | to trigger "at" some specific point in time. For example, if you tell a |
492 | periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () |
1080 | periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () |
493 | + 10.>) and then reset your system clock to the last year, then it will |
1081 | + 10.</code>) and then reset your system clock to the last year, then it will |
494 | take a year to trigger the event (unlike an ev_timer, which would trigger |
1082 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
495 | roughly 10 seconds later and of course not if you reset your system time |
1083 | roughly 10 seconds later and of course not if you reset your system time |
496 | again).</p> |
1084 | again).</p> |
497 | <p>They can also be used to implement vastly more complex timers, such as |
1085 | <p>They can also be used to implement vastly more complex timers, such as |
498 | triggering an event on eahc midnight, local time.</p> |
1086 | triggering an event on eahc midnight, local time.</p> |
|
|
1087 | <p>As with timers, the callback is guarenteed to be invoked only when the |
|
|
1088 | time (<code>at</code>) has been passed, but if multiple periodic timers become ready |
|
|
1089 | during the same loop iteration then order of execution is undefined.</p> |
499 | <dl> |
1090 | <dl> |
500 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
1091 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
501 | <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> |
1092 | <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> |
502 | <dd> |
1093 | <dd> |
503 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
1094 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
504 | operation, and we will explain them from simplest to complex:</p> |
1095 | operation, and we will explain them from simplest to complex:</p> |
505 | |
|
|
506 | |
|
|
507 | |
|
|
508 | |
|
|
509 | <p> |
1096 | <p> |
510 | <dl> |
1097 | <dl> |
511 | <dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
1098 | <dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
512 | <dd> |
1099 | <dd> |
513 | <p>In this configuration the watcher triggers an event at the wallclock time |
1100 | <p>In this configuration the watcher triggers an event at the wallclock time |
… | |
… | |
525 | <pre> ev_periodic_set (&periodic, 0., 3600., 0); |
1112 | <pre> ev_periodic_set (&periodic, 0., 3600., 0); |
526 | |
1113 | |
527 | </pre> |
1114 | </pre> |
528 | <p>This doesn't mean there will always be 3600 seconds in between triggers, |
1115 | <p>This doesn't mean there will always be 3600 seconds in between triggers, |
529 | but only that the the callback will be called when the system time shows a |
1116 | but only that the the callback will be called when the system time shows a |
530 | full hour (UTC), or more correct, when the system time is evenly divisible |
1117 | full hour (UTC), or more correctly, when the system time is evenly divisible |
531 | by 3600.</p> |
1118 | by 3600.</p> |
532 | <p>Another way to think about it (for the mathematically inclined) is that |
1119 | <p>Another way to think about it (for the mathematically inclined) is that |
533 | ev_periodic will try to run the callback in this mode at the next possible |
1120 | <code>ev_periodic</code> will try to run the callback in this mode at the next possible |
534 | time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> |
1121 | time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> |
535 | </dd> |
1122 | </dd> |
536 | <dt>* manual reschedule mode (reschedule_cb = callback)</dt> |
1123 | <dt>* manual reschedule mode (reschedule_cb = callback)</dt> |
537 | <dd> |
1124 | <dd> |
538 | <p>In this mode the values for <code>interval</code> and <code>at</code> are both being |
1125 | <p>In this mode the values for <code>interval</code> and <code>at</code> are both being |
539 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1126 | ignored. Instead, each time the periodic watcher gets scheduled, the |
540 | reschedule callback will be called with the watcher as first, and the |
1127 | reschedule callback will be called with the watcher as first, and the |
541 | current time as second argument.</p> |
1128 | current time as second argument.</p> |
542 | <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other |
1129 | <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, |
543 | periodic watcher, ever, or make any event loop modificstions</i>. If you need |
1130 | ever, or make any event loop modifications</i>. If you need to stop it, |
544 | to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p> |
1131 | return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by |
|
|
1132 | starting a prepare watcher).</p> |
545 | <p>Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1133 | <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
546 | ev_tstamp now)>, e.g.:</p> |
1134 | ev_tstamp now)</code>, e.g.:</p> |
547 | <pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1135 | <pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
548 | { |
1136 | { |
549 | return now + 60.; |
1137 | return now + 60.; |
550 | } |
1138 | } |
551 | |
1139 | |
552 | </pre> |
1140 | </pre> |
553 | <p>It must return the next time to trigger, based on the passed time value |
1141 | <p>It must return the next time to trigger, based on the passed time value |
554 | (that is, the lowest time value larger than to the second argument). It |
1142 | (that is, the lowest time value larger than to the second argument). It |
555 | will usually be called just before the callback will be triggered, but |
1143 | will usually be called just before the callback will be triggered, but |
556 | might be called at other times, too.</p> |
1144 | might be called at other times, too.</p> |
|
|
1145 | <p>NOTE: <i>This callback must always return a time that is later than the |
|
|
1146 | passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p> |
557 | <p>This can be used to create very complex timers, such as a timer that |
1147 | <p>This can be used to create very complex timers, such as a timer that |
558 | triggers on each midnight, local time. To do this, you would calculate the |
1148 | triggers on each midnight, local time. To do this, you would calculate the |
559 | next midnight after <code>now</code> and return the timestamp value for this. How you do this |
1149 | next midnight after <code>now</code> and return the timestamp value for this. How |
560 | is, again, up to you (but it is not trivial).</p> |
1150 | you do this is, again, up to you (but it is not trivial, which is the main |
|
|
1151 | reason I omitted it as an example).</p> |
561 | </dd> |
1152 | </dd> |
562 | </dl> |
1153 | </dl> |
563 | </p> |
1154 | </p> |
564 | </dd> |
1155 | </dd> |
565 | <dt>ev_periodic_again (loop, ev_periodic *)</dt> |
1156 | <dt>ev_periodic_again (loop, ev_periodic *)</dt> |
… | |
… | |
567 | <p>Simply stops and restarts the periodic watcher again. This is only useful |
1158 | <p>Simply stops and restarts the periodic watcher again. This is only useful |
568 | when you changed some parameters or the reschedule callback would return |
1159 | when you changed some parameters or the reschedule callback would return |
569 | a different time than the last time it was called (e.g. in a crond like |
1160 | a different time than the last time it was called (e.g. in a crond like |
570 | program when the crontabs have changed).</p> |
1161 | program when the crontabs have changed).</p> |
571 | </dd> |
1162 | </dd> |
|
|
1163 | <dt>ev_tstamp interval [read-write]</dt> |
|
|
1164 | <dd> |
|
|
1165 | <p>The current interval value. Can be modified any time, but changes only |
|
|
1166 | take effect when the periodic timer fires or <code>ev_periodic_again</code> is being |
|
|
1167 | called.</p> |
|
|
1168 | </dd> |
|
|
1169 | <dt>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]</dt> |
|
|
1170 | <dd> |
|
|
1171 | <p>The current reschedule callback, or <code>0</code>, if this functionality is |
|
|
1172 | switched off. Can be changed any time, but changes only take effect when |
|
|
1173 | the periodic timer fires or <code>ev_periodic_again</code> is being called.</p> |
|
|
1174 | </dd> |
572 | </dl> |
1175 | </dl> |
|
|
1176 | <p>Example: Call a callback every hour, or, more precisely, whenever the |
|
|
1177 | system clock is divisible by 3600. The callback invocation times have |
|
|
1178 | potentially a lot of jittering, but good long-term stability.</p> |
|
|
1179 | <pre> static void |
|
|
1180 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
|
|
1181 | { |
|
|
1182 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
|
|
1183 | } |
573 | |
1184 | |
|
|
1185 | struct ev_periodic hourly_tick; |
|
|
1186 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
|
|
1187 | ev_periodic_start (loop, &hourly_tick); |
|
|
1188 | |
|
|
1189 | </pre> |
|
|
1190 | <p>Example: The same as above, but use a reschedule callback to do it:</p> |
|
|
1191 | <pre> #include <math.h> |
|
|
1192 | |
|
|
1193 | static ev_tstamp |
|
|
1194 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
|
|
1195 | { |
|
|
1196 | return fmod (now, 3600.) + 3600.; |
|
|
1197 | } |
|
|
1198 | |
|
|
1199 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
|
|
1200 | |
|
|
1201 | </pre> |
|
|
1202 | <p>Example: Call a callback every hour, starting now:</p> |
|
|
1203 | <pre> struct ev_periodic hourly_tick; |
|
|
1204 | ev_periodic_init (&hourly_tick, clock_cb, |
|
|
1205 | fmod (ev_now (loop), 3600.), 3600., 0); |
|
|
1206 | ev_periodic_start (loop, &hourly_tick); |
|
|
1207 | |
|
|
1208 | |
|
|
1209 | |
|
|
1210 | |
|
|
1211 | </pre> |
|
|
1212 | |
574 | </div> |
1213 | </div> |
575 | <h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2> |
1214 | <h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled!</h2> |
576 | <div id="ev_signal_signal_me_when_a_signal_ge-2"> |
1215 | <div id="code_ev_signal_code_signal_me_when_a-2"> |
577 | <p>Signal watchers will trigger an event when the process receives a specific |
1216 | <p>Signal watchers will trigger an event when the process receives a specific |
578 | signal one or more times. Even though signals are very asynchronous, libev |
1217 | signal one or more times. Even though signals are very asynchronous, libev |
579 | will try its best to deliver signals synchronously, i.e. as part of the |
1218 | will try it's best to deliver signals synchronously, i.e. as part of the |
580 | normal event processing, like any other event.</p> |
1219 | normal event processing, like any other event.</p> |
581 | <p>You cna configure as many watchers as you like per signal. Only when the |
1220 | <p>You can configure as many watchers as you like per signal. Only when the |
582 | first watcher gets started will libev actually register a signal watcher |
1221 | first watcher gets started will libev actually register a signal watcher |
583 | with the kernel (thus it coexists with your own signal handlers as long |
1222 | with the kernel (thus it coexists with your own signal handlers as long |
584 | as you don't register any with libev). Similarly, when the last signal |
1223 | as you don't register any with libev). Similarly, when the last signal |
585 | watcher for a signal is stopped libev will reset the signal handler to |
1224 | watcher for a signal is stopped libev will reset the signal handler to |
586 | SIG_DFL (regardless of what it was set to before).</p> |
1225 | SIG_DFL (regardless of what it was set to before).</p> |
… | |
… | |
589 | <dt>ev_signal_set (ev_signal *, int signum)</dt> |
1228 | <dt>ev_signal_set (ev_signal *, int signum)</dt> |
590 | <dd> |
1229 | <dd> |
591 | <p>Configures the watcher to trigger on the given signal number (usually one |
1230 | <p>Configures the watcher to trigger on the given signal number (usually one |
592 | of the <code>SIGxxx</code> constants).</p> |
1231 | of the <code>SIGxxx</code> constants).</p> |
593 | </dd> |
1232 | </dd> |
|
|
1233 | <dt>int signum [read-only]</dt> |
|
|
1234 | <dd> |
|
|
1235 | <p>The signal the watcher watches out for.</p> |
|
|
1236 | </dd> |
594 | </dl> |
1237 | </dl> |
595 | |
1238 | |
|
|
1239 | |
|
|
1240 | |
|
|
1241 | |
|
|
1242 | |
596 | </div> |
1243 | </div> |
597 | <h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2> |
1244 | <h2 id="code_ev_child_code_watch_out_for_pro"><code>ev_child</code> - watch out for process status changes</h2> |
598 | <div id="ev_child_wait_for_pid_status_changes-2"> |
1245 | <div id="code_ev_child_code_watch_out_for_pro-2"> |
599 | <p>Child watchers trigger when your process receives a SIGCHLD in response to |
1246 | <p>Child watchers trigger when your process receives a SIGCHLD in response to |
600 | some child status changes (most typically when a child of yours dies).</p> |
1247 | some child status changes (most typically when a child of yours dies).</p> |
601 | <dl> |
1248 | <dl> |
602 | <dt>ev_child_init (ev_child *, callback, int pid)</dt> |
1249 | <dt>ev_child_init (ev_child *, callback, int pid)</dt> |
603 | <dt>ev_child_set (ev_child *, int pid)</dt> |
1250 | <dt>ev_child_set (ev_child *, int pid)</dt> |
604 | <dd> |
1251 | <dd> |
605 | <p>Configures the watcher to wait for status changes of process <code>pid</code> (or |
1252 | <p>Configures the watcher to wait for status changes of process <code>pid</code> (or |
606 | <i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look |
1253 | <i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look |
607 | at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see |
1254 | at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see |
608 | the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member |
1255 | the status word (use the macros from <code>sys/wait.h</code> and see your systems |
|
|
1256 | <code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the |
609 | contains the pid of the process causing the status change.</p> |
1257 | process causing the status change.</p> |
|
|
1258 | </dd> |
|
|
1259 | <dt>int pid [read-only]</dt> |
|
|
1260 | <dd> |
|
|
1261 | <p>The process id this watcher watches out for, or <code>0</code>, meaning any process id.</p> |
|
|
1262 | </dd> |
|
|
1263 | <dt>int rpid [read-write]</dt> |
|
|
1264 | <dd> |
|
|
1265 | <p>The process id that detected a status change.</p> |
|
|
1266 | </dd> |
|
|
1267 | <dt>int rstatus [read-write]</dt> |
|
|
1268 | <dd> |
|
|
1269 | <p>The process exit/trace status caused by <code>rpid</code> (see your systems |
|
|
1270 | <code>waitpid</code> and <code>sys/wait.h</code> documentation for details).</p> |
610 | </dd> |
1271 | </dd> |
611 | </dl> |
1272 | </dl> |
|
|
1273 | <p>Example: Try to exit cleanly on SIGINT and SIGTERM.</p> |
|
|
1274 | <pre> static void |
|
|
1275 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
|
|
1276 | { |
|
|
1277 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
1278 | } |
612 | |
1279 | |
|
|
1280 | struct ev_signal signal_watcher; |
|
|
1281 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1282 | ev_signal_start (loop, &sigint_cb); |
|
|
1283 | |
|
|
1284 | |
|
|
1285 | |
|
|
1286 | |
|
|
1287 | </pre> |
|
|
1288 | |
613 | </div> |
1289 | </div> |
|
|
1290 | <h2 id="code_ev_stat_code_did_the_file_attri"><code>ev_stat</code> - did the file attributes just change?</h2> |
|
|
1291 | <div id="code_ev_stat_code_did_the_file_attri-2"> |
|
|
1292 | <p>This watches a filesystem path for attribute changes. That is, it calls |
|
|
1293 | <code>stat</code> regularly (or when the OS says it changed) and sees if it changed |
|
|
1294 | compared to the last time, invoking the callback if it did.</p> |
|
|
1295 | <p>The path does not need to exist: changing from "path exists" to "path does |
|
|
1296 | not exist" is a status change like any other. The condition "path does |
|
|
1297 | not exist" is signified by the <code>st_nlink</code> field being zero (which is |
|
|
1298 | otherwise always forced to be at least one) and all the other fields of |
|
|
1299 | the stat buffer having unspecified contents.</p> |
|
|
1300 | <p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is |
|
|
1301 | relative and your working directory changes, the behaviour is undefined.</p> |
|
|
1302 | <p>Since there is no standard to do this, the portable implementation simply |
|
|
1303 | calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You |
|
|
1304 | can specify a recommended polling interval for this case. If you specify |
|
|
1305 | a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, |
|
|
1306 | unspecified default</i> value will be used (which you can expect to be around |
|
|
1307 | five seconds, although this might change dynamically). Libev will also |
|
|
1308 | impose a minimum interval which is currently around <code>0.1</code>, but thats |
|
|
1309 | usually overkill.</p> |
|
|
1310 | <p>This watcher type is not meant for massive numbers of stat watchers, |
|
|
1311 | as even with OS-supported change notifications, this can be |
|
|
1312 | resource-intensive.</p> |
|
|
1313 | <p>At the time of this writing, only the Linux inotify interface is |
|
|
1314 | implemented (implementing kqueue support is left as an exercise for the |
|
|
1315 | reader). Inotify will be used to give hints only and should not change the |
|
|
1316 | semantics of <code>ev_stat</code> watchers, which means that libev sometimes needs |
|
|
1317 | to fall back to regular polling again even with inotify, but changes are |
|
|
1318 | usually detected immediately, and if the file exists there will be no |
|
|
1319 | polling.</p> |
|
|
1320 | <dl> |
|
|
1321 | <dt>ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)</dt> |
|
|
1322 | <dt>ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)</dt> |
|
|
1323 | <dd> |
|
|
1324 | <p>Configures the watcher to wait for status changes of the given |
|
|
1325 | <code>path</code>. The <code>interval</code> is a hint on how quickly a change is expected to |
|
|
1326 | be detected and should normally be specified as <code>0</code> to let libev choose |
|
|
1327 | a suitable value. The memory pointed to by <code>path</code> must point to the same |
|
|
1328 | path for as long as the watcher is active.</p> |
|
|
1329 | <p>The callback will be receive <code>EV_STAT</code> when a change was detected, |
|
|
1330 | relative to the attributes at the time the watcher was started (or the |
|
|
1331 | last change was detected).</p> |
|
|
1332 | </dd> |
|
|
1333 | <dt>ev_stat_stat (ev_stat *)</dt> |
|
|
1334 | <dd> |
|
|
1335 | <p>Updates the stat buffer immediately with new values. If you change the |
|
|
1336 | watched path in your callback, you could call this fucntion to avoid |
|
|
1337 | detecting this change (while introducing a race condition). Can also be |
|
|
1338 | useful simply to find out the new values.</p> |
|
|
1339 | </dd> |
|
|
1340 | <dt>ev_statdata attr [read-only]</dt> |
|
|
1341 | <dd> |
|
|
1342 | <p>The most-recently detected attributes of the file. Although the type is of |
|
|
1343 | <code>ev_statdata</code>, this is usually the (or one of the) <code>struct stat</code> types |
|
|
1344 | suitable for your system. If the <code>st_nlink</code> member is <code>0</code>, then there |
|
|
1345 | was some error while <code>stat</code>ing the file.</p> |
|
|
1346 | </dd> |
|
|
1347 | <dt>ev_statdata prev [read-only]</dt> |
|
|
1348 | <dd> |
|
|
1349 | <p>The previous attributes of the file. The callback gets invoked whenever |
|
|
1350 | <code>prev</code> != <code>attr</code>.</p> |
|
|
1351 | </dd> |
|
|
1352 | <dt>ev_tstamp interval [read-only]</dt> |
|
|
1353 | <dd> |
|
|
1354 | <p>The specified interval.</p> |
|
|
1355 | </dd> |
|
|
1356 | <dt>const char *path [read-only]</dt> |
|
|
1357 | <dd> |
|
|
1358 | <p>The filesystem path that is being watched.</p> |
|
|
1359 | </dd> |
|
|
1360 | </dl> |
|
|
1361 | <p>Example: Watch <code>/etc/passwd</code> for attribute changes.</p> |
|
|
1362 | <pre> static void |
|
|
1363 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
|
|
1364 | { |
|
|
1365 | /* /etc/passwd changed in some way */ |
|
|
1366 | if (w->attr.st_nlink) |
|
|
1367 | { |
|
|
1368 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
|
|
1369 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
|
|
1370 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
|
|
1371 | } |
|
|
1372 | else |
|
|
1373 | /* you shalt not abuse printf for puts */ |
|
|
1374 | puts ("wow, /etc/passwd is not there, expect problems. " |
|
|
1375 | "if this is windows, they already arrived\n"); |
|
|
1376 | } |
|
|
1377 | |
|
|
1378 | ... |
|
|
1379 | ev_stat passwd; |
|
|
1380 | |
|
|
1381 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); |
|
|
1382 | ev_stat_start (loop, &passwd); |
|
|
1383 | |
|
|
1384 | |
|
|
1385 | |
|
|
1386 | |
|
|
1387 | </pre> |
|
|
1388 | |
|
|
1389 | </div> |
614 | <h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2> |
1390 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> |
615 | <div id="ev_idle_when_you_ve_got_nothing_bett-2"> |
1391 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
616 | <p>Idle watchers trigger events when there are no other I/O or timer (or |
1392 | <p>Idle watchers trigger events when no other events of the same or higher |
617 | periodic) events pending. That is, as long as your process is busy |
1393 | priority are pending (prepare, check and other idle watchers do not |
618 | handling sockets or timeouts it will not be called. But when your process |
1394 | count).</p> |
619 | is idle all idle watchers are being called again and again - until |
1395 | <p>That is, as long as your process is busy handling sockets or timeouts |
|
|
1396 | (or even signals, imagine) of the same or higher priority it will not be |
|
|
1397 | triggered. But when your process is idle (or only lower-priority watchers |
|
|
1398 | are pending), the idle watchers are being called once per event loop |
620 | stopped, that is, or your process receives more events.</p> |
1399 | iteration - until stopped, that is, or your process receives more events |
|
|
1400 | and becomes busy again with higher priority stuff.</p> |
621 | <p>The most noteworthy effect is that as long as any idle watchers are |
1401 | <p>The most noteworthy effect is that as long as any idle watchers are |
622 | active, the process will not block when waiting for new events.</p> |
1402 | active, the process will not block when waiting for new events.</p> |
623 | <p>Apart from keeping your process non-blocking (which is a useful |
1403 | <p>Apart from keeping your process non-blocking (which is a useful |
624 | effect on its own sometimes), idle watchers are a good place to do |
1404 | effect on its own sometimes), idle watchers are a good place to do |
625 | "pseudo-background processing", or delay processing stuff to after the |
1405 | "pseudo-background processing", or delay processing stuff to after the |
… | |
… | |
630 | <p>Initialises and configures the idle watcher - it has no parameters of any |
1410 | <p>Initialises and configures the idle watcher - it has no parameters of any |
631 | kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, |
1411 | kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, |
632 | believe me.</p> |
1412 | believe me.</p> |
633 | </dd> |
1413 | </dd> |
634 | </dl> |
1414 | </dl> |
|
|
1415 | <p>Example: Dynamically allocate an <code>ev_idle</code> watcher, start it, and in the |
|
|
1416 | callback, free it. Also, use no error checking, as usual.</p> |
|
|
1417 | <pre> static void |
|
|
1418 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
|
|
1419 | { |
|
|
1420 | free (w); |
|
|
1421 | // now do something you wanted to do when the program has |
|
|
1422 | // no longer asnything immediate to do. |
|
|
1423 | } |
635 | |
1424 | |
|
|
1425 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
|
|
1426 | ev_idle_init (idle_watcher, idle_cb); |
|
|
1427 | ev_idle_start (loop, idle_cb); |
|
|
1428 | |
|
|
1429 | |
|
|
1430 | |
|
|
1431 | |
|
|
1432 | </pre> |
|
|
1433 | |
636 | </div> |
1434 | </div> |
637 | <h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> |
1435 | <h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop!</h2> |
638 | <div id="prepare_and_check_your_hooks_into_th-2"> |
1436 | <div id="code_ev_prepare_code_and_code_ev_che-2"> |
639 | <p>Prepare and check watchers usually (but not always) are used in |
1437 | <p>Prepare and check watchers are usually (but not always) used in tandem: |
640 | tandom. Prepare watchers get invoked before the process blocks and check |
1438 | prepare watchers get invoked before the process blocks and check watchers |
641 | watchers afterwards.</p> |
1439 | afterwards.</p> |
|
|
1440 | <p>You <i>must not</i> call <code>ev_loop</code> or similar functions that enter |
|
|
1441 | the current event loop from either <code>ev_prepare</code> or <code>ev_check</code> |
|
|
1442 | watchers. Other loops than the current one are fine, however. The |
|
|
1443 | rationale behind this is that you do not need to check for recursion in |
|
|
1444 | those watchers, i.e. the sequence will always be <code>ev_prepare</code>, blocking, |
|
|
1445 | <code>ev_check</code> so if you have one watcher of each kind they will always be |
|
|
1446 | called in pairs bracketing the blocking call.</p> |
642 | <p>Their main purpose is to integrate other event mechanisms into libev. This |
1447 | <p>Their main purpose is to integrate other event mechanisms into libev and |
643 | could be used, for example, to track variable changes, implement your own |
1448 | their use is somewhat advanced. This could be used, for example, to track |
644 | watchers, integrate net-snmp or a coroutine library and lots more.</p> |
1449 | variable changes, implement your own watchers, integrate net-snmp or a |
|
|
1450 | coroutine library and lots more. They are also occasionally useful if |
|
|
1451 | you cache some data and want to flush it before blocking (for example, |
|
|
1452 | in X programs you might want to do an <code>XFlush ()</code> in an <code>ev_prepare</code> |
|
|
1453 | watcher).</p> |
645 | <p>This is done by examining in each prepare call which file descriptors need |
1454 | <p>This is done by examining in each prepare call which file descriptors need |
646 | to be watched by the other library, registering ev_io watchers for them |
1455 | to be watched by the other library, registering <code>ev_io</code> watchers for |
647 | and starting an ev_timer watcher for any timeouts (many libraries provide |
1456 | them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries |
648 | just this functionality). Then, in the check watcher you check for any |
1457 | provide just this functionality). Then, in the check watcher you check for |
649 | events that occured (by making your callbacks set soem flags for example) |
1458 | any events that occured (by checking the pending status of all watchers |
650 | and call back into the library.</p> |
1459 | and stopping them) and call back into the library. The I/O and timer |
|
|
1460 | callbacks will never actually be called (but must be valid nevertheless, |
|
|
1461 | because you never know, you know?).</p> |
651 | <p>As another example, the perl Coro module uses these hooks to integrate |
1462 | <p>As another example, the Perl Coro module uses these hooks to integrate |
652 | coroutines into libev programs, by yielding to other active coroutines |
1463 | coroutines into libev programs, by yielding to other active coroutines |
653 | during each prepare and only letting the process block if no coroutines |
1464 | during each prepare and only letting the process block if no coroutines |
654 | are ready to run.</p> |
1465 | are ready to run (it's actually more complicated: it only runs coroutines |
|
|
1466 | with priority higher than or equal to the event loop and one coroutine |
|
|
1467 | of lower priority, but only once, using idle watchers to keep the event |
|
|
1468 | loop from blocking if lower-priority coroutines are active, thus mapping |
|
|
1469 | low-priority coroutines to idle/background tasks).</p> |
655 | <dl> |
1470 | <dl> |
656 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
1471 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
657 | <dt>ev_check_init (ev_check *, callback)</dt> |
1472 | <dt>ev_check_init (ev_check *, callback)</dt> |
658 | <dd> |
1473 | <dd> |
659 | <p>Initialises and configures the prepare or check watcher - they have no |
1474 | <p>Initialises and configures the prepare or check watcher - they have no |
660 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1475 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
661 | macros, but using them is utterly, utterly pointless.</p> |
1476 | macros, but using them is utterly, utterly and completely pointless.</p> |
662 | </dd> |
1477 | </dd> |
663 | </dl> |
1478 | </dl> |
|
|
1479 | <p>Example: To include a library such as adns, you would add IO watchers |
|
|
1480 | and a timeout watcher in a prepare handler, as required by libadns, and |
|
|
1481 | in a check watcher, destroy them and call into libadns. What follows is |
|
|
1482 | pseudo-code only of course:</p> |
|
|
1483 | <pre> static ev_io iow [nfd]; |
|
|
1484 | static ev_timer tw; |
664 | |
1485 | |
|
|
1486 | static void |
|
|
1487 | io_cb (ev_loop *loop, ev_io *w, int revents) |
|
|
1488 | { |
|
|
1489 | // set the relevant poll flags |
|
|
1490 | // could also call adns_processreadable etc. here |
|
|
1491 | struct pollfd *fd = (struct pollfd *)w->data; |
|
|
1492 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1493 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
1494 | } |
|
|
1495 | |
|
|
1496 | // create io watchers for each fd and a timer before blocking |
|
|
1497 | static void |
|
|
1498 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
|
|
1499 | { |
|
|
1500 | int timeout = 3600000; |
|
|
1501 | struct pollfd fds [nfd]; |
|
|
1502 | // actual code will need to loop here and realloc etc. |
|
|
1503 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
|
|
1504 | |
|
|
1505 | /* the callback is illegal, but won't be called as we stop during check */ |
|
|
1506 | ev_timer_init (&tw, 0, timeout * 1e-3); |
|
|
1507 | ev_timer_start (loop, &tw); |
|
|
1508 | |
|
|
1509 | // create on ev_io per pollfd |
|
|
1510 | for (int i = 0; i < nfd; ++i) |
|
|
1511 | { |
|
|
1512 | ev_io_init (iow + i, io_cb, fds [i].fd, |
|
|
1513 | ((fds [i].events & POLLIN ? EV_READ : 0) |
|
|
1514 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
|
|
1515 | |
|
|
1516 | fds [i].revents = 0; |
|
|
1517 | iow [i].data = fds + i; |
|
|
1518 | ev_io_start (loop, iow + i); |
|
|
1519 | } |
|
|
1520 | } |
|
|
1521 | |
|
|
1522 | // stop all watchers after blocking |
|
|
1523 | static void |
|
|
1524 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
|
|
1525 | { |
|
|
1526 | ev_timer_stop (loop, &tw); |
|
|
1527 | |
|
|
1528 | for (int i = 0; i < nfd; ++i) |
|
|
1529 | ev_io_stop (loop, iow + i); |
|
|
1530 | |
|
|
1531 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
|
|
1532 | } |
|
|
1533 | |
|
|
1534 | |
|
|
1535 | |
|
|
1536 | |
|
|
1537 | </pre> |
|
|
1538 | |
665 | </div> |
1539 | </div> |
666 | <h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
1540 | <h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough...</h2> |
|
|
1541 | <div id="code_ev_embed_code_when_one_backend_-2"> |
|
|
1542 | <p>This is a rather advanced watcher type that lets you embed one event loop |
|
|
1543 | into another (currently only <code>ev_io</code> events are supported in the embedded |
|
|
1544 | loop, other types of watchers might be handled in a delayed or incorrect |
|
|
1545 | fashion and must not be used).</p> |
|
|
1546 | <p>There are primarily two reasons you would want that: work around bugs and |
|
|
1547 | prioritise I/O.</p> |
|
|
1548 | <p>As an example for a bug workaround, the kqueue backend might only support |
|
|
1549 | sockets on some platform, so it is unusable as generic backend, but you |
|
|
1550 | still want to make use of it because you have many sockets and it scales |
|
|
1551 | so nicely. In this case, you would create a kqueue-based loop and embed it |
|
|
1552 | into your default loop (which might use e.g. poll). Overall operation will |
|
|
1553 | be a bit slower because first libev has to poll and then call kevent, but |
|
|
1554 | at least you can use both at what they are best.</p> |
|
|
1555 | <p>As for prioritising I/O: rarely you have the case where some fds have |
|
|
1556 | to be watched and handled very quickly (with low latency), and even |
|
|
1557 | priorities and idle watchers might have too much overhead. In this case |
|
|
1558 | you would put all the high priority stuff in one loop and all the rest in |
|
|
1559 | a second one, and embed the second one in the first.</p> |
|
|
1560 | <p>As long as the watcher is active, the callback will be invoked every time |
|
|
1561 | there might be events pending in the embedded loop. The callback must then |
|
|
1562 | call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke |
|
|
1563 | their callbacks (you could also start an idle watcher to give the embedded |
|
|
1564 | loop strictly lower priority for example). You can also set the callback |
|
|
1565 | to <code>0</code>, in which case the embed watcher will automatically execute the |
|
|
1566 | embedded loop sweep.</p> |
|
|
1567 | <p>As long as the watcher is started it will automatically handle events. The |
|
|
1568 | callback will be invoked whenever some events have been handled. You can |
|
|
1569 | set the callback to <code>0</code> to avoid having to specify one if you are not |
|
|
1570 | interested in that.</p> |
|
|
1571 | <p>Also, there have not currently been made special provisions for forking: |
|
|
1572 | when you fork, you not only have to call <code>ev_loop_fork</code> on both loops, |
|
|
1573 | but you will also have to stop and restart any <code>ev_embed</code> watchers |
|
|
1574 | yourself.</p> |
|
|
1575 | <p>Unfortunately, not all backends are embeddable, only the ones returned by |
|
|
1576 | <code>ev_embeddable_backends</code> are, which, unfortunately, does not include any |
|
|
1577 | portable one.</p> |
|
|
1578 | <p>So when you want to use this feature you will always have to be prepared |
|
|
1579 | that you cannot get an embeddable loop. The recommended way to get around |
|
|
1580 | this is to have a separate variables for your embeddable loop, try to |
|
|
1581 | create it, and if that fails, use the normal loop for everything:</p> |
|
|
1582 | <pre> struct ev_loop *loop_hi = ev_default_init (0); |
|
|
1583 | struct ev_loop *loop_lo = 0; |
|
|
1584 | struct ev_embed embed; |
|
|
1585 | |
|
|
1586 | // see if there is a chance of getting one that works |
|
|
1587 | // (remember that a flags value of 0 means autodetection) |
|
|
1588 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
|
|
1589 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
|
|
1590 | : 0; |
|
|
1591 | |
|
|
1592 | // if we got one, then embed it, otherwise default to loop_hi |
|
|
1593 | if (loop_lo) |
|
|
1594 | { |
|
|
1595 | ev_embed_init (&embed, 0, loop_lo); |
|
|
1596 | ev_embed_start (loop_hi, &embed); |
|
|
1597 | } |
|
|
1598 | else |
|
|
1599 | loop_lo = loop_hi; |
|
|
1600 | |
|
|
1601 | </pre> |
|
|
1602 | <dl> |
|
|
1603 | <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt> |
|
|
1604 | <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt> |
|
|
1605 | <dd> |
|
|
1606 | <p>Configures the watcher to embed the given loop, which must be |
|
|
1607 | embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be |
|
|
1608 | invoked automatically, otherwise it is the responsibility of the callback |
|
|
1609 | to invoke it (it will continue to be called until the sweep has been done, |
|
|
1610 | if you do not want thta, you need to temporarily stop the embed watcher).</p> |
|
|
1611 | </dd> |
|
|
1612 | <dt>ev_embed_sweep (loop, ev_embed *)</dt> |
|
|
1613 | <dd> |
|
|
1614 | <p>Make a single, non-blocking sweep over the embedded loop. This works |
|
|
1615 | similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most |
|
|
1616 | apropriate way for embedded loops.</p> |
|
|
1617 | </dd> |
|
|
1618 | <dt>struct ev_loop *loop [read-only]</dt> |
|
|
1619 | <dd> |
|
|
1620 | <p>The embedded event loop.</p> |
|
|
1621 | </dd> |
|
|
1622 | </dl> |
|
|
1623 | |
|
|
1624 | |
|
|
1625 | |
|
|
1626 | |
|
|
1627 | |
|
|
1628 | </div> |
|
|
1629 | <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> |
|
|
1630 | <div id="code_ev_fork_code_the_audacity_to_re-2"> |
|
|
1631 | <p>Fork watchers are called when a <code>fork ()</code> was detected (usually because |
|
|
1632 | whoever is a good citizen cared to tell libev about it by calling |
|
|
1633 | <code>ev_default_fork</code> or <code>ev_loop_fork</code>). The invocation is done before the |
|
|
1634 | event loop blocks next and before <code>ev_check</code> watchers are being called, |
|
|
1635 | and only in the child after the fork. If whoever good citizen calling |
|
|
1636 | <code>ev_default_fork</code> cheats and calls it in the wrong process, the fork |
|
|
1637 | handlers will be invoked, too, of course.</p> |
|
|
1638 | <dl> |
|
|
1639 | <dt>ev_fork_init (ev_signal *, callback)</dt> |
|
|
1640 | <dd> |
|
|
1641 | <p>Initialises and configures the fork watcher - it has no parameters of any |
|
|
1642 | kind. There is a <code>ev_fork_set</code> macro, but using it is utterly pointless, |
|
|
1643 | believe me.</p> |
|
|
1644 | </dd> |
|
|
1645 | </dl> |
|
|
1646 | |
|
|
1647 | |
|
|
1648 | |
|
|
1649 | |
|
|
1650 | |
|
|
1651 | </div> |
|
|
1652 | <h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1> |
667 | <div id="OTHER_FUNCTIONS_CONTENT"> |
1653 | <div id="OTHER_FUNCTIONS_CONTENT"> |
668 | <p>There are some other fucntions of possible interest. Described. Here. Now.</p> |
1654 | <p>There are some other functions of possible interest. Described. Here. Now.</p> |
669 | <dl> |
1655 | <dl> |
670 | <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> |
1656 | <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> |
671 | <dd> |
1657 | <dd> |
672 | <p>This function combines a simple timer and an I/O watcher, calls your |
1658 | <p>This function combines a simple timer and an I/O watcher, calls your |
673 | callback on whichever event happens first and automatically stop both |
1659 | callback on whichever event happens first and automatically stop both |
674 | watchers. This is useful if you want to wait for a single event on an fd |
1660 | watchers. This is useful if you want to wait for a single event on an fd |
675 | or timeout without havign to allocate/configure/start/stop/free one or |
1661 | or timeout without having to allocate/configure/start/stop/free one or |
676 | more watchers yourself.</p> |
1662 | more watchers yourself.</p> |
677 | <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is |
1663 | <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events |
678 | ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set |
1664 | is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and |
679 | will be craeted and started.</p> |
1665 | <code>events</code> set will be craeted and started.</p> |
680 | <p>If <code>timeout</code> is less than 0, then no timeout watcher will be |
1666 | <p>If <code>timeout</code> is less than 0, then no timeout watcher will be |
681 | started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat |
1667 | started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and |
682 | = 0) will be started.</p> |
1668 | repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of |
|
|
1669 | dubious value.</p> |
683 | <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and |
1670 | <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets |
684 | gets passed an events set (normally a combination of EV_ERROR, EV_READ, |
1671 | passed an <code>revents</code> set like normal event callbacks (a combination of |
685 | EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p> |
1672 | <code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> |
|
|
1673 | value passed to <code>ev_once</code>:</p> |
686 | <pre> static void stdin_ready (int revents, void *arg) |
1674 | <pre> static void stdin_ready (int revents, void *arg) |
687 | { |
1675 | { |
688 | if (revents & EV_TIMEOUT) |
1676 | if (revents & EV_TIMEOUT) |
689 | /* doh, nothing entered */ |
1677 | /* doh, nothing entered */; |
690 | else if (revents & EV_READ) |
1678 | else if (revents & EV_READ) |
691 | /* stdin might have data for us, joy! */ |
1679 | /* stdin might have data for us, joy! */; |
692 | } |
1680 | } |
693 | |
1681 | |
694 | ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); |
1682 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
695 | |
1683 | |
696 | </pre> |
1684 | </pre> |
697 | </dd> |
1685 | </dd> |
698 | <dt>ev_feed_event (loop, watcher, int events)</dt> |
1686 | <dt>ev_feed_event (ev_loop *, watcher *, int revents)</dt> |
699 | <dd> |
1687 | <dd> |
700 | <p>Feeds the given event set into the event loop, as if the specified event |
1688 | <p>Feeds the given event set into the event loop, as if the specified event |
701 | has happened for the specified watcher (which must be a pointer to an |
1689 | had happened for the specified watcher (which must be a pointer to an |
702 | initialised but not necessarily active event watcher).</p> |
1690 | initialised but not necessarily started event watcher).</p> |
703 | </dd> |
1691 | </dd> |
704 | <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> |
1692 | <dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt> |
705 | <dd> |
1693 | <dd> |
706 | <p>Feed an event on the given fd, as if a file descriptor backend detected it.</p> |
1694 | <p>Feed an event on the given fd, as if a file descriptor backend detected |
|
|
1695 | the given events it.</p> |
707 | </dd> |
1696 | </dd> |
708 | <dt>ev_feed_signal_event (loop, int signum)</dt> |
1697 | <dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt> |
709 | <dd> |
1698 | <dd> |
710 | <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> |
1699 | <p>Feed an event as if the given signal occured (<code>loop</code> must be the default |
|
|
1700 | loop!).</p> |
711 | </dd> |
1701 | </dd> |
712 | </dl> |
1702 | </dl> |
713 | |
1703 | |
|
|
1704 | |
|
|
1705 | |
|
|
1706 | |
|
|
1707 | |
714 | </div> |
1708 | </div> |
715 | <h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> |
1709 | <h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1> |
|
|
1710 | <div id="LIBEVENT_EMULATION_CONTENT"> |
|
|
1711 | <p>Libev offers a compatibility emulation layer for libevent. It cannot |
|
|
1712 | emulate the internals of libevent, so here are some usage hints:</p> |
|
|
1713 | <dl> |
|
|
1714 | <dt>* Use it by including <event.h>, as usual.</dt> |
|
|
1715 | <dt>* The following members are fully supported: ev_base, ev_callback, |
|
|
1716 | ev_arg, ev_fd, ev_res, ev_events.</dt> |
|
|
1717 | <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is |
|
|
1718 | maintained by libev, it does not work exactly the same way as in libevent (consider |
|
|
1719 | it a private API).</dt> |
|
|
1720 | <dt>* Priorities are not currently supported. Initialising priorities |
|
|
1721 | will fail and all watchers will have the same priority, even though there |
|
|
1722 | is an ev_pri field.</dt> |
|
|
1723 | <dt>* Other members are not supported.</dt> |
|
|
1724 | <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need |
|
|
1725 | to use the libev header file and library.</dt> |
|
|
1726 | </dl> |
|
|
1727 | |
|
|
1728 | </div> |
|
|
1729 | <h1 id="C_SUPPORT">C++ SUPPORT</h1> |
|
|
1730 | <div id="C_SUPPORT_CONTENT"> |
|
|
1731 | <p>Libev comes with some simplistic wrapper classes for C++ that mainly allow |
|
|
1732 | you to use some convinience methods to start/stop watchers and also change |
|
|
1733 | the callback model to a model using method callbacks on objects.</p> |
|
|
1734 | <p>To use it,</p> |
|
|
1735 | <pre> #include <ev++.h> |
|
|
1736 | |
|
|
1737 | </pre> |
|
|
1738 | <p>(it is not installed by default). This automatically includes <cite>ev.h</cite> |
|
|
1739 | and puts all of its definitions (many of them macros) into the global |
|
|
1740 | namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> |
|
|
1741 | <p>It should support all the same embedding options as <cite>ev.h</cite>, most notably |
|
|
1742 | <code>EV_MULTIPLICITY</code>.</p> |
|
|
1743 | <p>Here is a list of things available in the <code>ev</code> namespace:</p> |
|
|
1744 | <dl> |
|
|
1745 | <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> |
|
|
1746 | <dd> |
|
|
1747 | <p>These are just enum values with the same values as the <code>EV_READ</code> etc. |
|
|
1748 | macros from <cite>ev.h</cite>.</p> |
|
|
1749 | </dd> |
|
|
1750 | <dt><code>ev::tstamp</code>, <code>ev::now</code></dt> |
|
|
1751 | <dd> |
|
|
1752 | <p>Aliases to the same types/functions as with the <code>ev_</code> prefix.</p> |
|
|
1753 | </dd> |
|
|
1754 | <dt><code>ev::io</code>, <code>ev::timer</code>, <code>ev::periodic</code>, <code>ev::idle</code>, <code>ev::sig</code> etc.</dt> |
|
|
1755 | <dd> |
|
|
1756 | <p>For each <code>ev_TYPE</code> watcher in <cite>ev.h</cite> there is a corresponding class of |
|
|
1757 | the same name in the <code>ev</code> namespace, with the exception of <code>ev_signal</code> |
|
|
1758 | which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro |
|
|
1759 | defines by many implementations.</p> |
|
|
1760 | <p>All of those classes have these methods:</p> |
|
|
1761 | <p> |
|
|
1762 | <dl> |
|
|
1763 | <dt>ev::TYPE::TYPE (object *, object::method *)</dt> |
|
|
1764 | <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> |
|
|
1765 | <dt>ev::TYPE::~TYPE</dt> |
|
|
1766 | <dd> |
|
|
1767 | <p>The constructor takes a pointer to an object and a method pointer to |
|
|
1768 | the event handler callback to call in this class. The constructor calls |
|
|
1769 | <code>ev_init</code> for you, which means you have to call the <code>set</code> method |
|
|
1770 | before starting it. If you do not specify a loop then the constructor |
|
|
1771 | automatically associates the default loop with this watcher.</p> |
|
|
1772 | <p>The destructor automatically stops the watcher if it is active.</p> |
|
|
1773 | </dd> |
|
|
1774 | <dt>w->set (struct ev_loop *)</dt> |
|
|
1775 | <dd> |
|
|
1776 | <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only |
|
|
1777 | do this when the watcher is inactive (and not pending either).</p> |
|
|
1778 | </dd> |
|
|
1779 | <dt>w->set ([args])</dt> |
|
|
1780 | <dd> |
|
|
1781 | <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be |
|
|
1782 | called at least once. Unlike the C counterpart, an active watcher gets |
|
|
1783 | automatically stopped and restarted.</p> |
|
|
1784 | </dd> |
|
|
1785 | <dt>w->start ()</dt> |
|
|
1786 | <dd> |
|
|
1787 | <p>Starts the watcher. Note that there is no <code>loop</code> argument as the |
|
|
1788 | constructor already takes the loop.</p> |
|
|
1789 | </dd> |
|
|
1790 | <dt>w->stop ()</dt> |
|
|
1791 | <dd> |
|
|
1792 | <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> |
|
|
1793 | </dd> |
|
|
1794 | <dt>w->again () <code>ev::timer</code>, <code>ev::periodic</code> only</dt> |
|
|
1795 | <dd> |
|
|
1796 | <p>For <code>ev::timer</code> and <code>ev::periodic</code>, this invokes the corresponding |
|
|
1797 | <code>ev_TYPE_again</code> function.</p> |
|
|
1798 | </dd> |
|
|
1799 | <dt>w->sweep () <code>ev::embed</code> only</dt> |
|
|
1800 | <dd> |
|
|
1801 | <p>Invokes <code>ev_embed_sweep</code>.</p> |
|
|
1802 | </dd> |
|
|
1803 | <dt>w->update () <code>ev::stat</code> only</dt> |
|
|
1804 | <dd> |
|
|
1805 | <p>Invokes <code>ev_stat_stat</code>.</p> |
|
|
1806 | </dd> |
|
|
1807 | </dl> |
|
|
1808 | </p> |
|
|
1809 | </dd> |
|
|
1810 | </dl> |
|
|
1811 | <p>Example: Define a class with an IO and idle watcher, start one of them in |
|
|
1812 | the constructor.</p> |
|
|
1813 | <pre> class myclass |
|
|
1814 | { |
|
|
1815 | ev_io io; void io_cb (ev::io &w, int revents); |
|
|
1816 | ev_idle idle void idle_cb (ev::idle &w, int revents); |
|
|
1817 | |
|
|
1818 | myclass (); |
|
|
1819 | } |
|
|
1820 | |
|
|
1821 | myclass::myclass (int fd) |
|
|
1822 | : io (this, &myclass::io_cb), |
|
|
1823 | idle (this, &myclass::idle_cb) |
|
|
1824 | { |
|
|
1825 | io.start (fd, ev::READ); |
|
|
1826 | } |
|
|
1827 | |
|
|
1828 | |
|
|
1829 | |
|
|
1830 | |
|
|
1831 | </pre> |
|
|
1832 | |
|
|
1833 | </div> |
|
|
1834 | <h1 id="MACRO_MAGIC">MACRO MAGIC</h1> |
|
|
1835 | <div id="MACRO_MAGIC_CONTENT"> |
|
|
1836 | <p>Libev can be compiled with a variety of options, the most fundemantal is |
|
|
1837 | <code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and |
|
|
1838 | callbacks have an initial <code>struct ev_loop *</code> argument.</p> |
|
|
1839 | <p>To make it easier to write programs that cope with either variant, the |
|
|
1840 | following macros are defined:</p> |
|
|
1841 | <dl> |
|
|
1842 | <dt><code>EV_A</code>, <code>EV_A_</code></dt> |
|
|
1843 | <dd> |
|
|
1844 | <p>This provides the loop <i>argument</i> for functions, if one is required ("ev |
|
|
1845 | loop argument"). The <code>EV_A</code> form is used when this is the sole argument, |
|
|
1846 | <code>EV_A_</code> is used when other arguments are following. Example:</p> |
|
|
1847 | <pre> ev_unref (EV_A); |
|
|
1848 | ev_timer_add (EV_A_ watcher); |
|
|
1849 | ev_loop (EV_A_ 0); |
|
|
1850 | |
|
|
1851 | </pre> |
|
|
1852 | <p>It assumes the variable <code>loop</code> of type <code>struct ev_loop *</code> is in scope, |
|
|
1853 | which is often provided by the following macro.</p> |
|
|
1854 | </dd> |
|
|
1855 | <dt><code>EV_P</code>, <code>EV_P_</code></dt> |
|
|
1856 | <dd> |
|
|
1857 | <p>This provides the loop <i>parameter</i> for functions, if one is required ("ev |
|
|
1858 | loop parameter"). The <code>EV_P</code> form is used when this is the sole parameter, |
|
|
1859 | <code>EV_P_</code> is used when other parameters are following. Example:</p> |
|
|
1860 | <pre> // this is how ev_unref is being declared |
|
|
1861 | static void ev_unref (EV_P); |
|
|
1862 | |
|
|
1863 | // this is how you can declare your typical callback |
|
|
1864 | static void cb (EV_P_ ev_timer *w, int revents) |
|
|
1865 | |
|
|
1866 | </pre> |
|
|
1867 | <p>It declares a parameter <code>loop</code> of type <code>struct ev_loop *</code>, quite |
|
|
1868 | suitable for use with <code>EV_A</code>.</p> |
|
|
1869 | </dd> |
|
|
1870 | <dt><code>EV_DEFAULT</code>, <code>EV_DEFAULT_</code></dt> |
|
|
1871 | <dd> |
|
|
1872 | <p>Similar to the other two macros, this gives you the value of the default |
|
|
1873 | loop, if multiple loops are supported ("ev loop default").</p> |
|
|
1874 | </dd> |
|
|
1875 | </dl> |
|
|
1876 | <p>Example: Declare and initialise a check watcher, utilising the above |
|
|
1877 | macros so it will work regardless of wether multiple loops are supported |
|
|
1878 | or not.</p> |
|
|
1879 | <pre> static void |
|
|
1880 | check_cb (EV_P_ ev_timer *w, int revents) |
|
|
1881 | { |
|
|
1882 | ev_check_stop (EV_A_ w); |
|
|
1883 | } |
|
|
1884 | |
|
|
1885 | ev_check check; |
|
|
1886 | ev_check_init (&check, check_cb); |
|
|
1887 | ev_check_start (EV_DEFAULT_ &check); |
|
|
1888 | ev_loop (EV_DEFAULT_ 0); |
|
|
1889 | |
|
|
1890 | </pre> |
|
|
1891 | |
|
|
1892 | </div> |
|
|
1893 | <h1 id="EMBEDDING">EMBEDDING</h1> |
|
|
1894 | <div id="EMBEDDING_CONTENT"> |
|
|
1895 | <p>Libev can (and often is) directly embedded into host |
|
|
1896 | applications. Examples of applications that embed it include the Deliantra |
|
|
1897 | Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) |
|
|
1898 | and rxvt-unicode.</p> |
|
|
1899 | <p>The goal is to enable you to just copy the neecssary files into your |
|
|
1900 | source directory without having to change even a single line in them, so |
|
|
1901 | you can easily upgrade by simply copying (or having a checked-out copy of |
|
|
1902 | libev somewhere in your source tree).</p> |
|
|
1903 | |
|
|
1904 | </div> |
|
|
1905 | <h2 id="FILESETS">FILESETS</h2> |
|
|
1906 | <div id="FILESETS_CONTENT"> |
|
|
1907 | <p>Depending on what features you need you need to include one or more sets of files |
|
|
1908 | in your app.</p> |
|
|
1909 | |
|
|
1910 | </div> |
|
|
1911 | <h3 id="CORE_EVENT_LOOP">CORE EVENT LOOP</h3> |
|
|
1912 | <div id="CORE_EVENT_LOOP_CONTENT"> |
|
|
1913 | <p>To include only the libev core (all the <code>ev_*</code> functions), with manual |
|
|
1914 | configuration (no autoconf):</p> |
|
|
1915 | <pre> #define EV_STANDALONE 1 |
|
|
1916 | #include "ev.c" |
|
|
1917 | |
|
|
1918 | </pre> |
|
|
1919 | <p>This will automatically include <cite>ev.h</cite>, too, and should be done in a |
|
|
1920 | single C source file only to provide the function implementations. To use |
|
|
1921 | it, do the same for <cite>ev.h</cite> in all files wishing to use this API (best |
|
|
1922 | done by writing a wrapper around <cite>ev.h</cite> that you can include instead and |
|
|
1923 | where you can put other configuration options):</p> |
|
|
1924 | <pre> #define EV_STANDALONE 1 |
|
|
1925 | #include "ev.h" |
|
|
1926 | |
|
|
1927 | </pre> |
|
|
1928 | <p>Both header files and implementation files can be compiled with a C++ |
|
|
1929 | compiler (at least, thats a stated goal, and breakage will be treated |
|
|
1930 | as a bug).</p> |
|
|
1931 | <p>You need the following files in your source tree, or in a directory |
|
|
1932 | in your include path (e.g. in libev/ when using -Ilibev):</p> |
|
|
1933 | <pre> ev.h |
|
|
1934 | ev.c |
|
|
1935 | ev_vars.h |
|
|
1936 | ev_wrap.h |
|
|
1937 | |
|
|
1938 | ev_win32.c required on win32 platforms only |
|
|
1939 | |
|
|
1940 | ev_select.c only when select backend is enabled (which is enabled by default) |
|
|
1941 | ev_poll.c only when poll backend is enabled (disabled by default) |
|
|
1942 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
|
|
1943 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
|
|
1944 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
|
|
1945 | |
|
|
1946 | </pre> |
|
|
1947 | <p><cite>ev.c</cite> includes the backend files directly when enabled, so you only need |
|
|
1948 | to compile this single file.</p> |
|
|
1949 | |
|
|
1950 | </div> |
|
|
1951 | <h3 id="LIBEVENT_COMPATIBILITY_API">LIBEVENT COMPATIBILITY API</h3> |
|
|
1952 | <div id="LIBEVENT_COMPATIBILITY_API_CONTENT"> |
|
|
1953 | <p>To include the libevent compatibility API, also include:</p> |
|
|
1954 | <pre> #include "event.c" |
|
|
1955 | |
|
|
1956 | </pre> |
|
|
1957 | <p>in the file including <cite>ev.c</cite>, and:</p> |
|
|
1958 | <pre> #include "event.h" |
|
|
1959 | |
|
|
1960 | </pre> |
|
|
1961 | <p>in the files that want to use the libevent API. This also includes <cite>ev.h</cite>.</p> |
|
|
1962 | <p>You need the following additional files for this:</p> |
|
|
1963 | <pre> event.h |
|
|
1964 | event.c |
|
|
1965 | |
|
|
1966 | </pre> |
|
|
1967 | |
|
|
1968 | </div> |
|
|
1969 | <h3 id="AUTOCONF_SUPPORT">AUTOCONF SUPPORT</h3> |
|
|
1970 | <div id="AUTOCONF_SUPPORT_CONTENT"> |
|
|
1971 | <p>Instead of using <code>EV_STANDALONE=1</code> and providing your config in |
|
|
1972 | whatever way you want, you can also <code>m4_include([libev.m4])</code> in your |
|
|
1973 | <cite>configure.ac</cite> and leave <code>EV_STANDALONE</code> undefined. <cite>ev.c</cite> will then |
|
|
1974 | include <cite>config.h</cite> and configure itself accordingly.</p> |
|
|
1975 | <p>For this of course you need the m4 file:</p> |
|
|
1976 | <pre> libev.m4 |
|
|
1977 | |
|
|
1978 | </pre> |
|
|
1979 | |
|
|
1980 | </div> |
|
|
1981 | <h2 id="PREPROCESSOR_SYMBOLS_MACROS">PREPROCESSOR SYMBOLS/MACROS</h2> |
|
|
1982 | <div id="PREPROCESSOR_SYMBOLS_MACROS_CONTENT"> |
|
|
1983 | <p>Libev can be configured via a variety of preprocessor symbols you have to define |
|
|
1984 | before including any of its files. The default is not to build for multiplicity |
|
|
1985 | and only include the select backend.</p> |
|
|
1986 | <dl> |
|
|
1987 | <dt>EV_STANDALONE</dt> |
|
|
1988 | <dd> |
|
|
1989 | <p>Must always be <code>1</code> if you do not use autoconf configuration, which |
|
|
1990 | keeps libev from including <cite>config.h</cite>, and it also defines dummy |
|
|
1991 | implementations for some libevent functions (such as logging, which is not |
|
|
1992 | supported). It will also not define any of the structs usually found in |
|
|
1993 | <cite>event.h</cite> that are not directly supported by the libev core alone.</p> |
|
|
1994 | </dd> |
|
|
1995 | <dt>EV_USE_MONOTONIC</dt> |
|
|
1996 | <dd> |
|
|
1997 | <p>If defined to be <code>1</code>, libev will try to detect the availability of the |
|
|
1998 | monotonic clock option at both compiletime and runtime. Otherwise no use |
|
|
1999 | of the monotonic clock option will be attempted. If you enable this, you |
|
|
2000 | usually have to link against librt or something similar. Enabling it when |
|
|
2001 | the functionality isn't available is safe, though, althoguh you have |
|
|
2002 | to make sure you link against any libraries where the <code>clock_gettime</code> |
|
|
2003 | function is hiding in (often <cite>-lrt</cite>).</p> |
|
|
2004 | </dd> |
|
|
2005 | <dt>EV_USE_REALTIME</dt> |
|
|
2006 | <dd> |
|
|
2007 | <p>If defined to be <code>1</code>, libev will try to detect the availability of the |
|
|
2008 | realtime clock option at compiletime (and assume its availability at |
|
|
2009 | runtime if successful). Otherwise no use of the realtime clock option will |
|
|
2010 | be attempted. This effectively replaces <code>gettimeofday</code> by <code>clock_get |
|
|
2011 | (CLOCK_REALTIME, ...)</code> and will not normally affect correctness. See tzhe note about libraries |
|
|
2012 | in the description of <code>EV_USE_MONOTONIC</code>, though.</p> |
|
|
2013 | </dd> |
|
|
2014 | <dt>EV_USE_SELECT</dt> |
|
|
2015 | <dd> |
|
|
2016 | <p>If undefined or defined to be <code>1</code>, libev will compile in support for the |
|
|
2017 | <code>select</code>(2) backend. No attempt at autodetection will be done: if no |
|
|
2018 | other method takes over, select will be it. Otherwise the select backend |
|
|
2019 | will not be compiled in.</p> |
|
|
2020 | </dd> |
|
|
2021 | <dt>EV_SELECT_USE_FD_SET</dt> |
|
|
2022 | <dd> |
|
|
2023 | <p>If defined to <code>1</code>, then the select backend will use the system <code>fd_set</code> |
|
|
2024 | structure. This is useful if libev doesn't compile due to a missing |
|
|
2025 | <code>NFDBITS</code> or <code>fd_mask</code> definition or it misguesses the bitset layout on |
|
|
2026 | exotic systems. This usually limits the range of file descriptors to some |
|
|
2027 | low limit such as 1024 or might have other limitations (winsocket only |
|
|
2028 | allows 64 sockets). The <code>FD_SETSIZE</code> macro, set before compilation, might |
|
|
2029 | influence the size of the <code>fd_set</code> used.</p> |
|
|
2030 | </dd> |
|
|
2031 | <dt>EV_SELECT_IS_WINSOCKET</dt> |
|
|
2032 | <dd> |
|
|
2033 | <p>When defined to <code>1</code>, the select backend will assume that |
|
|
2034 | select/socket/connect etc. don't understand file descriptors but |
|
|
2035 | wants osf handles on win32 (this is the case when the select to |
|
|
2036 | be used is the winsock select). This means that it will call |
|
|
2037 | <code>_get_osfhandle</code> on the fd to convert it to an OS handle. Otherwise, |
|
|
2038 | it is assumed that all these functions actually work on fds, even |
|
|
2039 | on win32. Should not be defined on non-win32 platforms.</p> |
|
|
2040 | </dd> |
|
|
2041 | <dt>EV_USE_POLL</dt> |
|
|
2042 | <dd> |
|
|
2043 | <p>If defined to be <code>1</code>, libev will compile in support for the <code>poll</code>(2) |
|
|
2044 | backend. Otherwise it will be enabled on non-win32 platforms. It |
|
|
2045 | takes precedence over select.</p> |
|
|
2046 | </dd> |
|
|
2047 | <dt>EV_USE_EPOLL</dt> |
|
|
2048 | <dd> |
|
|
2049 | <p>If defined to be <code>1</code>, libev will compile in support for the Linux |
|
|
2050 | <code>epoll</code>(7) backend. Its availability will be detected at runtime, |
|
|
2051 | otherwise another method will be used as fallback. This is the |
|
|
2052 | preferred backend for GNU/Linux systems.</p> |
|
|
2053 | </dd> |
|
|
2054 | <dt>EV_USE_KQUEUE</dt> |
|
|
2055 | <dd> |
|
|
2056 | <p>If defined to be <code>1</code>, libev will compile in support for the BSD style |
|
|
2057 | <code>kqueue</code>(2) backend. Its actual availability will be detected at runtime, |
|
|
2058 | otherwise another method will be used as fallback. This is the preferred |
|
|
2059 | backend for BSD and BSD-like systems, although on most BSDs kqueue only |
|
|
2060 | supports some types of fds correctly (the only platform we found that |
|
|
2061 | supports ptys for example was NetBSD), so kqueue might be compiled in, but |
|
|
2062 | not be used unless explicitly requested. The best way to use it is to find |
|
|
2063 | out whether kqueue supports your type of fd properly and use an embedded |
|
|
2064 | kqueue loop.</p> |
|
|
2065 | </dd> |
|
|
2066 | <dt>EV_USE_PORT</dt> |
|
|
2067 | <dd> |
|
|
2068 | <p>If defined to be <code>1</code>, libev will compile in support for the Solaris |
|
|
2069 | 10 port style backend. Its availability will be detected at runtime, |
|
|
2070 | otherwise another method will be used as fallback. This is the preferred |
|
|
2071 | backend for Solaris 10 systems.</p> |
|
|
2072 | </dd> |
|
|
2073 | <dt>EV_USE_DEVPOLL</dt> |
|
|
2074 | <dd> |
|
|
2075 | <p>reserved for future expansion, works like the USE symbols above.</p> |
|
|
2076 | </dd> |
|
|
2077 | <dt>EV_USE_INOTIFY</dt> |
|
|
2078 | <dd> |
|
|
2079 | <p>If defined to be <code>1</code>, libev will compile in support for the Linux inotify |
|
|
2080 | interface to speed up <code>ev_stat</code> watchers. Its actual availability will |
|
|
2081 | be detected at runtime.</p> |
|
|
2082 | </dd> |
|
|
2083 | <dt>EV_H</dt> |
|
|
2084 | <dd> |
|
|
2085 | <p>The name of the <cite>ev.h</cite> header file used to include it. The default if |
|
|
2086 | undefined is <code><ev.h></code> in <cite>event.h</cite> and <code>"ev.h"</code> in <cite>ev.c</cite>. This |
|
|
2087 | can be used to virtually rename the <cite>ev.h</cite> header file in case of conflicts.</p> |
|
|
2088 | </dd> |
|
|
2089 | <dt>EV_CONFIG_H</dt> |
|
|
2090 | <dd> |
|
|
2091 | <p>If <code>EV_STANDALONE</code> isn't <code>1</code>, this variable can be used to override |
|
|
2092 | <cite>ev.c</cite>'s idea of where to find the <cite>config.h</cite> file, similarly to |
|
|
2093 | <code>EV_H</code>, above.</p> |
|
|
2094 | </dd> |
|
|
2095 | <dt>EV_EVENT_H</dt> |
|
|
2096 | <dd> |
|
|
2097 | <p>Similarly to <code>EV_H</code>, this macro can be used to override <cite>event.c</cite>'s idea |
|
|
2098 | of how the <cite>event.h</cite> header can be found.</p> |
|
|
2099 | </dd> |
|
|
2100 | <dt>EV_PROTOTYPES</dt> |
|
|
2101 | <dd> |
|
|
2102 | <p>If defined to be <code>0</code>, then <cite>ev.h</cite> will not define any function |
|
|
2103 | prototypes, but still define all the structs and other symbols. This is |
|
|
2104 | occasionally useful if you want to provide your own wrapper functions |
|
|
2105 | around libev functions.</p> |
|
|
2106 | </dd> |
|
|
2107 | <dt>EV_MULTIPLICITY</dt> |
|
|
2108 | <dd> |
|
|
2109 | <p>If undefined or defined to <code>1</code>, then all event-loop-specific functions |
|
|
2110 | will have the <code>struct ev_loop *</code> as first argument, and you can create |
|
|
2111 | additional independent event loops. Otherwise there will be no support |
|
|
2112 | for multiple event loops and there is no first event loop pointer |
|
|
2113 | argument. Instead, all functions act on the single default loop.</p> |
|
|
2114 | </dd> |
|
|
2115 | <dt>EV_PERIODIC_ENABLE</dt> |
|
|
2116 | <dd> |
|
|
2117 | <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If |
|
|
2118 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
|
|
2119 | code.</p> |
|
|
2120 | </dd> |
|
|
2121 | <dt>EV_IDLE_ENABLE</dt> |
|
|
2122 | <dd> |
|
|
2123 | <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If |
|
|
2124 | defined to be <code>0</code>, then they are not. Disabling them saves a few kB of |
|
|
2125 | code.</p> |
|
|
2126 | </dd> |
|
|
2127 | <dt>EV_EMBED_ENABLE</dt> |
|
|
2128 | <dd> |
|
|
2129 | <p>If undefined or defined to be <code>1</code>, then embed watchers are supported. If |
|
|
2130 | defined to be <code>0</code>, then they are not.</p> |
|
|
2131 | </dd> |
|
|
2132 | <dt>EV_STAT_ENABLE</dt> |
|
|
2133 | <dd> |
|
|
2134 | <p>If undefined or defined to be <code>1</code>, then stat watchers are supported. If |
|
|
2135 | defined to be <code>0</code>, then they are not.</p> |
|
|
2136 | </dd> |
|
|
2137 | <dt>EV_FORK_ENABLE</dt> |
|
|
2138 | <dd> |
|
|
2139 | <p>If undefined or defined to be <code>1</code>, then fork watchers are supported. If |
|
|
2140 | defined to be <code>0</code>, then they are not.</p> |
|
|
2141 | </dd> |
|
|
2142 | <dt>EV_MINIMAL</dt> |
|
|
2143 | <dd> |
|
|
2144 | <p>If you need to shave off some kilobytes of code at the expense of some |
|
|
2145 | speed, define this symbol to <code>1</code>. Currently only used for gcc to override |
|
|
2146 | some inlining decisions, saves roughly 30% codesize of amd64.</p> |
|
|
2147 | </dd> |
|
|
2148 | <dt>EV_PID_HASHSIZE</dt> |
|
|
2149 | <dd> |
|
|
2150 | <p><code>ev_child</code> watchers use a small hash table to distribute workload by |
|
|
2151 | pid. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), usually more |
|
|
2152 | than enough. If you need to manage thousands of children you might want to |
|
|
2153 | increase this value (<i>must</i> be a power of two).</p> |
|
|
2154 | </dd> |
|
|
2155 | <dt>EV_INOTIFY_HASHSIZE</dt> |
|
|
2156 | <dd> |
|
|
2157 | <p><code>ev_staz</code> watchers use a small hash table to distribute workload by |
|
|
2158 | inotify watch id. The default size is <code>16</code> (or <code>1</code> with <code>EV_MINIMAL</code>), |
|
|
2159 | usually more than enough. If you need to manage thousands of <code>ev_stat</code> |
|
|
2160 | watchers you might want to increase this value (<i>must</i> be a power of |
|
|
2161 | two).</p> |
|
|
2162 | </dd> |
|
|
2163 | <dt>EV_COMMON</dt> |
|
|
2164 | <dd> |
|
|
2165 | <p>By default, all watchers have a <code>void *data</code> member. By redefining |
|
|
2166 | this macro to a something else you can include more and other types of |
|
|
2167 | members. You have to define it each time you include one of the files, |
|
|
2168 | though, and it must be identical each time.</p> |
|
|
2169 | <p>For example, the perl EV module uses something like this:</p> |
|
|
2170 | <pre> #define EV_COMMON \ |
|
|
2171 | SV *self; /* contains this struct */ \ |
|
|
2172 | SV *cb_sv, *fh /* note no trailing ";" */ |
|
|
2173 | |
|
|
2174 | </pre> |
|
|
2175 | </dd> |
|
|
2176 | <dt>EV_CB_DECLARE (type)</dt> |
|
|
2177 | <dt>EV_CB_INVOKE (watcher, revents)</dt> |
|
|
2178 | <dt>ev_set_cb (ev, cb)</dt> |
|
|
2179 | <dd> |
|
|
2180 | <p>Can be used to change the callback member declaration in each watcher, |
|
|
2181 | and the way callbacks are invoked and set. Must expand to a struct member |
|
|
2182 | definition and a statement, respectively. See the <cite>ev.v</cite> header file for |
|
|
2183 | their default definitions. One possible use for overriding these is to |
|
|
2184 | avoid the <code>struct ev_loop *</code> as first argument in all cases, or to use |
|
|
2185 | method calls instead of plain function calls in C++.</p> |
|
|
2186 | |
|
|
2187 | </div> |
|
|
2188 | <h2 id="EXAMPLES">EXAMPLES</h2> |
|
|
2189 | <div id="EXAMPLES_CONTENT"> |
|
|
2190 | <p>For a real-world example of a program the includes libev |
|
|
2191 | verbatim, you can have a look at the EV perl module |
|
|
2192 | (<a href="http://software.schmorp.de/pkg/EV.html">http://software.schmorp.de/pkg/EV.html</a>). It has the libev files in |
|
|
2193 | the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public |
|
|
2194 | interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file |
|
|
2195 | will be compiled. It is pretty complex because it provides its own header |
|
|
2196 | file.</p> |
|
|
2197 | <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file |
|
|
2198 | that everybody includes and which overrides some configure choices:</p> |
|
|
2199 | <pre> #define EV_MINIMAL 1 |
|
|
2200 | #define EV_USE_POLL 0 |
|
|
2201 | #define EV_MULTIPLICITY 0 |
|
|
2202 | #define EV_PERIODIC_ENABLE 0 |
|
|
2203 | #define EV_STAT_ENABLE 0 |
|
|
2204 | #define EV_FORK_ENABLE 0 |
|
|
2205 | #define EV_CONFIG_H <config.h> |
|
|
2206 | #define EV_MINPRI 0 |
|
|
2207 | #define EV_MAXPRI 0 |
|
|
2208 | |
|
|
2209 | #include "ev++.h" |
|
|
2210 | |
|
|
2211 | </pre> |
|
|
2212 | <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> |
|
|
2213 | <pre> #include "ev_cpp.h" |
|
|
2214 | #include "ev.c" |
|
|
2215 | |
|
|
2216 | |
|
|
2217 | |
|
|
2218 | |
|
|
2219 | </pre> |
|
|
2220 | |
|
|
2221 | </div> |
|
|
2222 | <h1 id="COMPLEXITIES">COMPLEXITIES</h1> |
|
|
2223 | <div id="COMPLEXITIES_CONTENT"> |
|
|
2224 | <p>In this section the complexities of (many of) the algorithms used inside |
|
|
2225 | libev will be explained. For complexity discussions about backends see the |
|
|
2226 | documentation for <code>ev_default_init</code>.</p> |
|
|
2227 | <p> |
|
|
2228 | <dl> |
|
|
2229 | <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> |
|
|
2230 | <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> |
|
|
2231 | <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> |
|
|
2232 | <dt>Stopping check/prepare/idle watchers: O(1)</dt> |
|
|
2233 | <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> |
|
|
2234 | <dt>Finding the next timer per loop iteration: O(1)</dt> |
|
|
2235 | <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> |
|
|
2236 | <dt>Activating one watcher: O(1)</dt> |
|
|
2237 | </dl> |
|
|
2238 | </p> |
|
|
2239 | |
|
|
2240 | |
|
|
2241 | |
|
|
2242 | |
|
|
2243 | |
|
|
2244 | </div> |
|
|
2245 | <h1 id="AUTHOR">AUTHOR</h1> |
716 | <div id="AUTHOR_CONTENT"> |
2246 | <div id="AUTHOR_CONTENT"> |
717 | <p>Marc Lehmann <libev@schmorp.de>.</p> |
2247 | <p>Marc Lehmann <libev@schmorp.de>.</p> |
718 | |
2248 | |
719 | </div> |
2249 | </div> |
720 | </div></body> |
2250 | </div></body> |
721 | </html> |
2251 | </html> |