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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" /> |
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13 | <div class="pod"> |
13 | <div class="pod"> |
14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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32 | <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="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li> |
33 | <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="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li> |
34 | <li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> |
34 | <li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> |
35 | <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="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li> |
36 | <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> |
36 | <li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li> |
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37 | <li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</a></li> |
37 | </ul> |
38 | </ul> |
38 | </li> |
39 | </li> |
39 | <li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> |
40 | <li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> |
40 | <li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> |
41 | <li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> |
41 | <li><a href="#C_SUPPORT">C++ SUPPORT</a></li> |
42 | <li><a href="#C_SUPPORT">C++ SUPPORT</a></li> |
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96 | <div id="TIME_REPRESENTATION_CONTENT"> |
97 | <div id="TIME_REPRESENTATION_CONTENT"> |
97 | <p>Libev represents time as a single floating point number, representing the |
98 | <p>Libev represents time as a single floating point number, representing the |
98 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
99 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
99 | the beginning of 1970, details are complicated, don't ask). This type is |
100 | the beginning of 1970, details are complicated, don't ask). This type is |
100 | called <code>ev_tstamp</code>, which is what you should use too. It usually aliases |
101 | called <code>ev_tstamp</code>, which is what you should use too. It usually aliases |
101 | to the double type in C.</p> |
102 | to the <code>double</code> type in C, and when you need to do any calculations on |
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103 | it, you should treat it as such.</p> |
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104 | |
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105 | |
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106 | |
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107 | |
102 | |
108 | |
103 | </div> |
109 | </div> |
104 | <h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
110 | <h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
105 | <div id="GLOBAL_FUNCTIONS_CONTENT"> |
111 | <div id="GLOBAL_FUNCTIONS_CONTENT"> |
106 | <p>These functions can be called anytime, even before initialising the |
112 | <p>These functions can be called anytime, even before initialising the |
107 | library in any way.</p> |
113 | library in any way.</p> |
108 | <dl> |
114 | <dl> |
109 | <dt>ev_tstamp ev_time ()</dt> |
115 | <dt>ev_tstamp ev_time ()</dt> |
110 | <dd> |
116 | <dd> |
111 | <p>Returns the current time as libev would use it.</p> |
117 | <p>Returns the current time as libev would use it. Please note that the |
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118 | <code>ev_now</code> function is usually faster and also often returns the timestamp |
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119 | you actually want to know.</p> |
112 | </dd> |
120 | </dd> |
113 | <dt>int ev_version_major ()</dt> |
121 | <dt>int ev_version_major ()</dt> |
114 | <dt>int ev_version_minor ()</dt> |
122 | <dt>int ev_version_minor ()</dt> |
115 | <dd> |
123 | <dd> |
116 | <p>You can find out the major and minor version numbers of the library |
124 | <p>You can find out the major and minor version numbers of the library |
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120 | version of the library your program was compiled against.</p> |
128 | version of the library your program was compiled against.</p> |
121 | <p>Usually, it's a good idea to terminate if the major versions mismatch, |
129 | <p>Usually, it's a good idea to terminate if the major versions mismatch, |
122 | as this indicates an incompatible change. Minor versions are usually |
130 | as this indicates an incompatible change. Minor versions are usually |
123 | compatible to older versions, so a larger minor version alone is usually |
131 | compatible to older versions, so a larger minor version alone is usually |
124 | not a problem.</p> |
132 | not a problem.</p> |
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133 | <p>Example: make sure we haven't accidentally been linked against the wrong |
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134 | version:</p> |
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135 | <pre> assert (("libev version mismatch", |
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136 | ev_version_major () == EV_VERSION_MAJOR |
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137 | && ev_version_minor () >= EV_VERSION_MINOR)); |
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138 | |
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139 | </pre> |
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140 | </dd> |
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141 | <dt>unsigned int ev_supported_backends ()</dt> |
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142 | <dd> |
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143 | <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code> |
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144 | value) compiled into this binary of libev (independent of their |
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145 | availability on the system you are running on). See <code>ev_default_loop</code> for |
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146 | a description of the set values.</p> |
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147 | <p>Example: make sure we have the epoll method, because yeah this is cool and |
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148 | a must have and can we have a torrent of it please!!!11</p> |
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149 | <pre> assert (("sorry, no epoll, no sex", |
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150 | ev_supported_backends () & EVBACKEND_EPOLL)); |
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151 | |
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152 | </pre> |
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153 | </dd> |
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154 | <dt>unsigned int ev_recommended_backends ()</dt> |
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155 | <dd> |
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156 | <p>Return the set of all backends compiled into this binary of libev and also |
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157 | recommended for this platform. This set is often smaller than the one |
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158 | returned by <code>ev_supported_backends</code>, as for example kqueue is broken on |
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159 | most BSDs and will not be autodetected unless you explicitly request it |
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160 | (assuming you know what you are doing). This is the set of backends that |
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161 | libev will probe for if you specify no backends explicitly.</p> |
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162 | </dd> |
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163 | <dt>unsigned int ev_embeddable_backends ()</dt> |
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164 | <dd> |
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165 | <p>Returns the set of backends that are embeddable in other event loops. This |
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166 | is the theoretical, all-platform, value. To find which backends |
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167 | might be supported on the current system, you would need to look at |
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168 | <code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for |
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169 | recommended ones.</p> |
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170 | <p>See the description of <code>ev_embed</code> watchers for more info.</p> |
125 | </dd> |
171 | </dd> |
126 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
172 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
127 | <dd> |
173 | <dd> |
128 | <p>Sets the allocation function to use (the prototype is similar to the |
174 | <p>Sets the allocation function to use (the prototype is similar to the |
129 | realloc C function, the semantics are identical). It is used to allocate |
175 | realloc C function, the semantics are identical). It is used to allocate |
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131 | needs to be allocated, the library might abort or take some potentially |
177 | needs to be allocated, the library might abort or take some potentially |
132 | destructive action. The default is your system realloc function.</p> |
178 | destructive action. The default is your system realloc function.</p> |
133 | <p>You could override this function in high-availability programs to, say, |
179 | <p>You could override this function in high-availability programs to, say, |
134 | free some memory if it cannot allocate memory, to use a special allocator, |
180 | free some memory if it cannot allocate memory, to use a special allocator, |
135 | or even to sleep a while and retry until some memory is available.</p> |
181 | or even to sleep a while and retry until some memory is available.</p> |
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182 | <p>Example: replace the libev allocator with one that waits a bit and then |
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183 | retries: better than mine).</p> |
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184 | <pre> static void * |
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185 | persistent_realloc (void *ptr, long size) |
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186 | { |
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187 | for (;;) |
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188 | { |
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189 | void *newptr = realloc (ptr, size); |
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190 | |
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191 | if (newptr) |
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192 | return newptr; |
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193 | |
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194 | sleep (60); |
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195 | } |
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196 | } |
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197 | |
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198 | ... |
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199 | ev_set_allocator (persistent_realloc); |
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200 | |
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201 | </pre> |
136 | </dd> |
202 | </dd> |
137 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
203 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
138 | <dd> |
204 | <dd> |
139 | <p>Set the callback function to call on a retryable syscall error (such |
205 | <p>Set the callback function to call on a retryable syscall error (such |
140 | as failed select, poll, epoll_wait). The message is a printable string |
206 | as failed select, poll, epoll_wait). The message is a printable string |
141 | indicating the system call or subsystem causing the problem. If this |
207 | indicating the system call or subsystem causing the problem. If this |
142 | callback is set, then libev will expect it to remedy the sitution, no |
208 | callback is set, then libev will expect it to remedy the sitution, no |
143 | matter what, when it returns. That is, libev will generally retry the |
209 | matter what, when it returns. That is, libev will generally retry the |
144 | requested operation, or, if the condition doesn't go away, do bad stuff |
210 | requested operation, or, if the condition doesn't go away, do bad stuff |
145 | (such as abort).</p> |
211 | (such as abort).</p> |
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212 | <p>Example: do the same thing as libev does internally:</p> |
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213 | <pre> static void |
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214 | fatal_error (const char *msg) |
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215 | { |
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216 | perror (msg); |
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217 | abort (); |
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218 | } |
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219 | |
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220 | ... |
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221 | ev_set_syserr_cb (fatal_error); |
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222 | |
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223 | </pre> |
146 | </dd> |
224 | </dd> |
147 | </dl> |
225 | </dl> |
148 | |
226 | |
149 | </div> |
227 | </div> |
150 | <h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> |
228 | <h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> |
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162 | <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> |
240 | <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> |
163 | <dd> |
241 | <dd> |
164 | <p>This will initialise the default event loop if it hasn't been initialised |
242 | <p>This will initialise the default event loop if it hasn't been initialised |
165 | yet and return it. If the default loop could not be initialised, returns |
243 | yet and return it. If the default loop could not be initialised, returns |
166 | false. If it already was initialised it simply returns it (and ignores the |
244 | false. If it already was initialised it simply returns it (and ignores the |
167 | flags).</p> |
245 | flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p> |
168 | <p>If you don't know what event loop to use, use the one returned from this |
246 | <p>If you don't know what event loop to use, use the one returned from this |
169 | function.</p> |
247 | function.</p> |
170 | <p>The flags argument can be used to specify special behaviour or specific |
248 | <p>The flags argument can be used to specify special behaviour or specific |
171 | backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p> |
249 | backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p> |
172 | <p>It supports the following flags:</p> |
250 | <p>The following flags are supported:</p> |
173 | <p> |
251 | <p> |
174 | <dl> |
252 | <dl> |
175 | <dt><code>EVFLAG_AUTO</code></dt> |
253 | <dt><code>EVFLAG_AUTO</code></dt> |
176 | <dd> |
254 | <dd> |
177 | <p>The default flags value. Use this if you have no clue (it's the right |
255 | <p>The default flags value. Use this if you have no clue (it's the right |
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184 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
262 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
185 | override the flags completely if it is found in the environment. This is |
263 | override the flags completely if it is found in the environment. This is |
186 | useful to try out specific backends to test their performance, or to work |
264 | useful to try out specific backends to test their performance, or to work |
187 | around bugs.</p> |
265 | around bugs.</p> |
188 | </dd> |
266 | </dd> |
189 | <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt> |
267 | <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> |
190 | <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt> |
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191 | <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt> |
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192 | <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt> |
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193 | <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt> |
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194 | <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt> |
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195 | <dd> |
268 | <dd> |
196 | <p>If one or more of these are ored into the flags value, then only these |
269 | <p>This is your standard select(2) backend. Not <i>completely</i> standard, as |
197 | backends will be tried (in the reverse order as given here). If one are |
270 | libev tries to roll its own fd_set with no limits on the number of fds, |
198 | specified, any backend will do.</p> |
271 | but if that fails, expect a fairly low limit on the number of fds when |
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272 | using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
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273 | the fastest backend for a low number of fds.</p> |
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274 | </dd> |
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275 | <dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt> |
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276 | <dd> |
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277 | <p>And this is your standard poll(2) backend. It's more complicated than |
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278 | select, but handles sparse fds better and has no artificial limit on the |
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279 | number of fds you can use (except it will slow down considerably with a |
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280 | lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p> |
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281 | </dd> |
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282 | <dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt> |
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283 | <dd> |
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284 | <p>For few fds, this backend is a bit little slower than poll and select, |
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285 | but it scales phenomenally better. While poll and select usually scale like |
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286 | O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
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287 | either O(1) or O(active_fds).</p> |
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288 | <p>While stopping and starting an I/O watcher in the same iteration will |
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289 | result in some caching, there is still a syscall per such incident |
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290 | (because the fd could point to a different file description now), so its |
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291 | best to avoid that. Also, dup()ed file descriptors might not work very |
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292 | well if you register events for both fds.</p> |
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293 | <p>Please note that epoll sometimes generates spurious notifications, so you |
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294 | need to use non-blocking I/O or other means to avoid blocking when no data |
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295 | (or space) is available.</p> |
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296 | </dd> |
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297 | <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt> |
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298 | <dd> |
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299 | <p>Kqueue deserves special mention, as at the time of this writing, it |
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300 | was broken on all BSDs except NetBSD (usually it doesn't work with |
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301 | anything but sockets and pipes, except on Darwin, where of course its |
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302 | completely useless). For this reason its not being "autodetected" |
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303 | unless you explicitly specify it explicitly in the flags (i.e. using |
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304 | <code>EVBACKEND_KQUEUE</code>).</p> |
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305 | <p>It scales in the same way as the epoll backend, but the interface to the |
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306 | kernel is more efficient (which says nothing about its actual speed, of |
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307 | course). While starting and stopping an I/O watcher does not cause an |
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308 | extra syscall as with epoll, it still adds up to four event changes per |
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309 | incident, so its best to avoid that.</p> |
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310 | </dd> |
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311 | <dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt> |
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312 | <dd> |
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313 | <p>This is not implemented yet (and might never be).</p> |
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314 | </dd> |
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315 | <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt> |
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316 | <dd> |
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317 | <p>This uses the Solaris 10 port mechanism. As with everything on Solaris, |
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318 | it's really slow, but it still scales very well (O(active_fds)).</p> |
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319 | <p>Please note that solaris ports can result in a lot of spurious |
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320 | notifications, so you need to use non-blocking I/O or other means to avoid |
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321 | blocking when no data (or space) is available.</p> |
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322 | </dd> |
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323 | <dt><code>EVBACKEND_ALL</code></dt> |
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324 | <dd> |
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325 | <p>Try all backends (even potentially broken ones that wouldn't be tried |
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326 | with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as |
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327 | <code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p> |
199 | </dd> |
328 | </dd> |
200 | </dl> |
329 | </dl> |
201 | </p> |
330 | </p> |
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331 | <p>If one or more of these are ored into the flags value, then only these |
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332 | backends will be tried (in the reverse order as given here). If none are |
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333 | specified, most compiled-in backend will be tried, usually in reverse |
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334 | order of their flag values :)</p> |
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335 | <p>The most typical usage is like this:</p> |
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336 | <pre> if (!ev_default_loop (0)) |
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337 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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338 | |
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339 | </pre> |
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340 | <p>Restrict libev to the select and poll backends, and do not allow |
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341 | environment settings to be taken into account:</p> |
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342 | <pre> ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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343 | |
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344 | </pre> |
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345 | <p>Use whatever libev has to offer, but make sure that kqueue is used if |
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346 | available (warning, breaks stuff, best use only with your own private |
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347 | event loop and only if you know the OS supports your types of fds):</p> |
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348 | <pre> ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
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349 | |
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350 | </pre> |
202 | </dd> |
351 | </dd> |
203 | <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> |
352 | <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> |
204 | <dd> |
353 | <dd> |
205 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
354 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
206 | always distinct from the default loop. Unlike the default loop, it cannot |
355 | always distinct from the default loop. Unlike the default loop, it cannot |
207 | handle signal and child watchers, and attempts to do so will be greeted by |
356 | handle signal and child watchers, and attempts to do so will be greeted by |
208 | undefined behaviour (or a failed assertion if assertions are enabled).</p> |
357 | undefined behaviour (or a failed assertion if assertions are enabled).</p> |
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358 | <p>Example: try to create a event loop that uses epoll and nothing else.</p> |
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359 | <pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
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360 | if (!epoller) |
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361 | fatal ("no epoll found here, maybe it hides under your chair"); |
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362 | |
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363 | </pre> |
209 | </dd> |
364 | </dd> |
210 | <dt>ev_default_destroy ()</dt> |
365 | <dt>ev_default_destroy ()</dt> |
211 | <dd> |
366 | <dd> |
212 | <p>Destroys the default loop again (frees all memory and kernel state |
367 | <p>Destroys the default loop again (frees all memory and kernel state |
213 | etc.). This stops all registered event watchers (by not touching them in |
368 | etc.). This stops all registered event watchers (by not touching them in |
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222 | <dd> |
377 | <dd> |
223 | <p>This function reinitialises the kernel state for backends that have |
378 | <p>This function reinitialises the kernel state for backends that have |
224 | one. Despite the name, you can call it anytime, but it makes most sense |
379 | one. Despite the name, you can call it anytime, but it makes most sense |
225 | after forking, in either the parent or child process (or both, but that |
380 | after forking, in either the parent or child process (or both, but that |
226 | again makes little sense).</p> |
381 | again makes little sense).</p> |
227 | <p>You <i>must</i> call this function after forking if and only if you want to |
382 | <p>You <i>must</i> call this function in the child process after forking if and |
228 | use the event library in both processes. If you just fork+exec, you don't |
383 | only if you want to use the event library in both processes. If you just |
229 | have to call it.</p> |
384 | fork+exec, you don't have to call it.</p> |
230 | <p>The function itself is quite fast and it's usually not a problem to call |
385 | <p>The function itself is quite fast and it's usually not a problem to call |
231 | it just in case after a fork. To make this easy, the function will fit in |
386 | it just in case after a fork. To make this easy, the function will fit in |
232 | quite nicely into a call to <code>pthread_atfork</code>:</p> |
387 | quite nicely into a call to <code>pthread_atfork</code>:</p> |
233 | <pre> pthread_atfork (0, 0, ev_default_fork); |
388 | <pre> pthread_atfork (0, 0, ev_default_fork); |
234 | |
389 | |
235 | </pre> |
390 | </pre> |
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391 | <p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use |
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392 | without calling this function, so if you force one of those backends you |
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393 | do not need to care.</p> |
236 | </dd> |
394 | </dd> |
237 | <dt>ev_loop_fork (loop)</dt> |
395 | <dt>ev_loop_fork (loop)</dt> |
238 | <dd> |
396 | <dd> |
239 | <p>Like <code>ev_default_fork</code>, but acts on an event loop created by |
397 | <p>Like <code>ev_default_fork</code>, but acts on an event loop created by |
240 | <code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop |
398 | <code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop |
241 | after fork, and how you do this is entirely your own problem.</p> |
399 | after fork, and how you do this is entirely your own problem.</p> |
242 | </dd> |
400 | </dd> |
243 | <dt>unsigned int ev_method (loop)</dt> |
401 | <dt>unsigned int ev_backend (loop)</dt> |
244 | <dd> |
402 | <dd> |
245 | <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in |
403 | <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in |
246 | use.</p> |
404 | use.</p> |
247 | </dd> |
405 | </dd> |
248 | <dt>ev_tstamp ev_now (loop)</dt> |
406 | <dt>ev_tstamp ev_now (loop)</dt> |
249 | <dd> |
407 | <dd> |
250 | <p>Returns the current "event loop time", which is the time the event loop |
408 | <p>Returns the current "event loop time", which is the time the event loop |
251 | got events and started processing them. This timestamp does not change |
409 | received events and started processing them. This timestamp does not |
252 | as long as callbacks are being processed, and this is also the base time |
410 | change as long as callbacks are being processed, and this is also the base |
253 | used for relative timers. You can treat it as the timestamp of the event |
411 | time used for relative timers. You can treat it as the timestamp of the |
254 | occuring (or more correctly, the mainloop finding out about it).</p> |
412 | event occuring (or more correctly, libev finding out about it).</p> |
255 | </dd> |
413 | </dd> |
256 | <dt>ev_loop (loop, int flags)</dt> |
414 | <dt>ev_loop (loop, int flags)</dt> |
257 | <dd> |
415 | <dd> |
258 | <p>Finally, this is it, the event handler. This function usually is called |
416 | <p>Finally, this is it, the event handler. This function usually is called |
259 | after you initialised all your watchers and you want to start handling |
417 | after you initialised all your watchers and you want to start handling |
260 | events.</p> |
418 | events.</p> |
261 | <p>If the flags argument is specified as 0, it will not return until either |
419 | <p>If the flags argument is specified as <code>0</code>, it will not return until |
262 | no event watchers are active anymore or <code>ev_unloop</code> was called.</p> |
420 | either no event watchers are active anymore or <code>ev_unloop</code> was called.</p> |
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|
421 | <p>Please note that an explicit <code>ev_unloop</code> is usually better than |
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422 | relying on all watchers to be stopped when deciding when a program has |
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423 | finished (especially in interactive programs), but having a program that |
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424 | automatically loops as long as it has to and no longer by virtue of |
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425 | relying on its watchers stopping correctly is a thing of beauty.</p> |
263 | <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle |
426 | <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle |
264 | those events and any outstanding ones, but will not block your process in |
427 | those events and any outstanding ones, but will not block your process in |
265 | case there are no events and will return after one iteration of the loop.</p> |
428 | case there are no events and will return after one iteration of the loop.</p> |
266 | <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if |
429 | <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if |
267 | neccessary) and will handle those and any outstanding ones. It will block |
430 | neccessary) and will handle those and any outstanding ones. It will block |
268 | your process until at least one new event arrives, and will return after |
431 | your process until at least one new event arrives, and will return after |
269 | one iteration of the loop.</p> |
432 | one iteration of the loop. This is useful if you are waiting for some |
270 | <p>This flags value could be used to implement alternative looping |
433 | external event in conjunction with something not expressible using other |
271 | constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and |
434 | libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is |
272 | more generic mechanism.</p> |
435 | usually a better approach for this kind of thing.</p> |
|
|
436 | <p>Here are the gory details of what <code>ev_loop</code> does:</p> |
|
|
437 | <pre> * If there are no active watchers (reference count is zero), return. |
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438 | - Queue prepare watchers and then call all outstanding watchers. |
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439 | - If we have been forked, recreate the kernel state. |
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440 | - Update the kernel state with all outstanding changes. |
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441 | - Update the "event loop time". |
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442 | - Calculate for how long to block. |
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443 | - Block the process, waiting for any events. |
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444 | - Queue all outstanding I/O (fd) events. |
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445 | - Update the "event loop time" and do time jump handling. |
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446 | - Queue all outstanding timers. |
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447 | - Queue all outstanding periodics. |
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448 | - If no events are pending now, queue all idle watchers. |
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449 | - Queue all check watchers. |
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450 | - Call all queued watchers in reverse order (i.e. check watchers first). |
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451 | Signals and child watchers are implemented as I/O watchers, and will |
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452 | be handled here by queueing them when their watcher gets executed. |
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453 | - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
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454 | were used, return, otherwise continue with step *. |
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455 | |
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456 | </pre> |
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|
457 | <p>Example: queue some jobs and then loop until no events are outsanding |
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458 | anymore.</p> |
|
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459 | <pre> ... queue jobs here, make sure they register event watchers as long |
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460 | ... as they still have work to do (even an idle watcher will do..) |
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461 | ev_loop (my_loop, 0); |
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462 | ... jobs done. yeah! |
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463 | |
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464 | </pre> |
273 | </dd> |
465 | </dd> |
274 | <dt>ev_unloop (loop, how)</dt> |
466 | <dt>ev_unloop (loop, how)</dt> |
275 | <dd> |
467 | <dd> |
276 | <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it |
468 | <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it |
277 | has processed all outstanding events). The <code>how</code> argument must be either |
469 | has processed all outstanding events). The <code>how</code> argument must be either |
278 | <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or |
470 | <code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or |
279 | <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> |
471 | <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> |
280 | </dd> |
472 | </dd> |
281 | <dt>ev_ref (loop)</dt> |
473 | <dt>ev_ref (loop)</dt> |
282 | <dt>ev_unref (loop)</dt> |
474 | <dt>ev_unref (loop)</dt> |
283 | <dd> |
475 | <dd> |
… | |
… | |
289 | example, libev itself uses this for its internal signal pipe: It is not |
481 | example, libev itself uses this for its internal signal pipe: It is not |
290 | visible to the libev user and should not keep <code>ev_loop</code> from exiting if |
482 | visible to the libev user and should not keep <code>ev_loop</code> from exiting if |
291 | no event watchers registered by it are active. It is also an excellent |
483 | no event watchers registered by it are active. It is also an excellent |
292 | way to do this for generic recurring timers or from within third-party |
484 | way to do this for generic recurring timers or from within third-party |
293 | libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> |
485 | libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> |
|
|
486 | <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> |
|
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487 | running when nothing else is active.</p> |
|
|
488 | <pre> struct dv_signal exitsig; |
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489 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
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490 | ev_signal_start (myloop, &exitsig); |
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491 | evf_unref (myloop); |
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492 | |
|
|
493 | </pre> |
|
|
494 | <p>Example: for some weird reason, unregister the above signal handler again.</p> |
|
|
495 | <pre> ev_ref (myloop); |
|
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496 | ev_signal_stop (myloop, &exitsig); |
|
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497 | |
|
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498 | </pre> |
294 | </dd> |
499 | </dd> |
295 | </dl> |
500 | </dl> |
296 | |
501 | |
297 | </div> |
502 | </div> |
298 | <h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> |
503 | <h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> |
… | |
… | |
330 | with a watcher-specific start function (<code>ev_<type>_start (loop, watcher |
535 | with a watcher-specific start function (<code>ev_<type>_start (loop, watcher |
331 | *)</code>), and you can stop watching for events at any time by calling the |
536 | *)</code>), and you can stop watching for events at any time by calling the |
332 | corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p> |
537 | corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p> |
333 | <p>As long as your watcher is active (has been started but not stopped) you |
538 | <p>As long as your watcher is active (has been started but not stopped) you |
334 | must not touch the values stored in it. Most specifically you must never |
539 | must not touch the values stored in it. Most specifically you must never |
335 | reinitialise it or call its set method.</p> |
540 | reinitialise it or call its set macro.</p> |
336 | <p>You can check whether an event is active by calling the <code>ev_is_active |
541 | <p>You can check whether an event is active by calling the <code>ev_is_active |
337 | (watcher *)</code> macro. To see whether an event is outstanding (but the |
542 | (watcher *)</code> macro. To see whether an event is outstanding (but the |
338 | callback for it has not been called yet) you can use the <code>ev_is_pending |
543 | callback for it has not been called yet) you can use the <code>ev_is_pending |
339 | (watcher *)</code> macro.</p> |
544 | (watcher *)</code> macro.</p> |
340 | <p>Each and every callback receives the event loop pointer as first, the |
545 | <p>Each and every callback receives the event loop pointer as first, the |
… | |
… | |
434 | <h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> |
639 | <h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> |
435 | <div id="WATCHER_TYPES_CONTENT"> |
640 | <div id="WATCHER_TYPES_CONTENT"> |
436 | <p>This section describes each watcher in detail, but will not repeat |
641 | <p>This section describes each watcher in detail, but will not repeat |
437 | information given in the last section.</p> |
642 | information given in the last section.</p> |
438 | |
643 | |
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644 | |
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645 | |
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646 | |
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647 | |
439 | </div> |
648 | </div> |
440 | <h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> |
649 | <h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> |
441 | <div id="code_ev_io_code_is_this_file_descrip-2"> |
650 | <div id="code_ev_io_code_is_this_file_descrip-2"> |
442 | <p>I/O watchers check whether a file descriptor is readable or writable |
651 | <p>I/O watchers check whether a file descriptor is readable or writable |
443 | in each iteration of the event loop (This behaviour is called |
652 | in each iteration of the event loop (This behaviour is called |
444 | level-triggering because you keep receiving events as long as the |
653 | level-triggering because you keep receiving events as long as the |
445 | condition persists. Remember you can stop the watcher if you don't want to |
654 | condition persists. Remember you can stop the watcher if you don't want to |
446 | act on the event and neither want to receive future events).</p> |
655 | act on the event and neither want to receive future events).</p> |
447 | <p>In general you can register as many read and/or write event watchers oer |
656 | <p>In general you can register as many read and/or write event watchers per |
448 | fd as you want (as long as you don't confuse yourself). Setting all file |
657 | fd as you want (as long as you don't confuse yourself). Setting all file |
449 | descriptors to non-blocking mode is also usually a good idea (but not |
658 | descriptors to non-blocking mode is also usually a good idea (but not |
450 | required if you know what you are doing).</p> |
659 | required if you know what you are doing).</p> |
451 | <p>You have to be careful with dup'ed file descriptors, though. Some backends |
660 | <p>You have to be careful with dup'ed file descriptors, though. Some backends |
452 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
661 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
453 | descriptors correctly if you register interest in two or more fds pointing |
662 | descriptors correctly if you register interest in two or more fds pointing |
454 | to the same file/socket etc. description.</p> |
663 | to the same underlying file/socket etc. description (that is, they share |
|
|
664 | the same underlying "file open").</p> |
455 | <p>If you must do this, then force the use of a known-to-be-good backend |
665 | <p>If you must do this, then force the use of a known-to-be-good backend |
456 | (at the time of this writing, this includes only EVMETHOD_SELECT and |
666 | (at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and |
457 | EVMETHOD_POLL).</p> |
667 | <code>EVBACKEND_POLL</code>).</p> |
458 | <dl> |
668 | <dl> |
459 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
669 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
460 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
670 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
461 | <dd> |
671 | <dd> |
462 | <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive |
672 | <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive |
463 | events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | |
673 | events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | |
464 | EV_WRITE</code> to receive the given events.</p> |
674 | EV_WRITE</code> to receive the given events.</p> |
|
|
675 | <p>Please note that most of the more scalable backend mechanisms (for example |
|
|
676 | epoll and solaris ports) can result in spurious readyness notifications |
|
|
677 | for file descriptors, so you practically need to use non-blocking I/O (and |
|
|
678 | treat callback invocation as hint only), or retest separately with a safe |
|
|
679 | interface before doing I/O (XLib can do this), or force the use of either |
|
|
680 | <code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this |
|
|
681 | problem. Also note that it is quite easy to have your callback invoked |
|
|
682 | when the readyness condition is no longer valid even when employing |
|
|
683 | typical ways of handling events, so its a good idea to use non-blocking |
|
|
684 | I/O unconditionally.</p> |
465 | </dd> |
685 | </dd> |
466 | </dl> |
686 | </dl> |
|
|
687 | <p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well |
|
|
688 | readable, but only once. Since it is likely line-buffered, you could |
|
|
689 | attempt to read a whole line in the callback:</p> |
|
|
690 | <pre> static void |
|
|
691 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
|
|
692 | { |
|
|
693 | ev_io_stop (loop, w); |
|
|
694 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
|
|
695 | } |
|
|
696 | |
|
|
697 | ... |
|
|
698 | struct ev_loop *loop = ev_default_init (0); |
|
|
699 | struct ev_io stdin_readable; |
|
|
700 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
|
|
701 | ev_io_start (loop, &stdin_readable); |
|
|
702 | ev_loop (loop, 0); |
|
|
703 | |
|
|
704 | |
|
|
705 | |
|
|
706 | |
|
|
707 | </pre> |
467 | |
708 | |
468 | </div> |
709 | </div> |
469 | <h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> |
710 | <h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> |
470 | <div id="code_ev_timer_code_relative_and_opti-2"> |
711 | <div id="code_ev_timer_code_relative_and_opti-2"> |
471 | <p>Timer watchers are simple relative timers that generate an event after a |
712 | <p>Timer watchers are simple relative timers that generate an event after a |
472 | given time, and optionally repeating in regular intervals after that.</p> |
713 | given time, and optionally repeating in regular intervals after that.</p> |
473 | <p>The timers are based on real time, that is, if you register an event that |
714 | <p>The timers are based on real time, that is, if you register an event that |
474 | times out after an hour and youreset your system clock to last years |
715 | times out after an hour and you reset your system clock to last years |
475 | time, it will still time out after (roughly) and hour. "Roughly" because |
716 | time, it will still time out after (roughly) and hour. "Roughly" because |
476 | detecting time jumps is hard, and soem inaccuracies are unavoidable (the |
717 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
477 | monotonic clock option helps a lot here).</p> |
718 | monotonic clock option helps a lot here).</p> |
478 | <p>The relative timeouts are calculated relative to the <code>ev_now ()</code> |
719 | <p>The relative timeouts are calculated relative to the <code>ev_now ()</code> |
479 | time. This is usually the right thing as this timestamp refers to the time |
720 | time. This is usually the right thing as this timestamp refers to the time |
480 | of the event triggering whatever timeout you are modifying/starting. If |
721 | of the event triggering whatever timeout you are modifying/starting. If |
481 | you suspect event processing to be delayed and you *need* to base the timeout |
722 | you suspect event processing to be delayed and you <i>need</i> to base the timeout |
482 | ion the current time, use something like this to adjust for this:</p> |
723 | on the current time, use something like this to adjust for this:</p> |
483 | <pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
724 | <pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
484 | |
725 | |
485 | </pre> |
726 | </pre> |
|
|
727 | <p>The callback is guarenteed to be invoked only when its timeout has passed, |
|
|
728 | but if multiple timers become ready during the same loop iteration then |
|
|
729 | order of execution is undefined.</p> |
486 | <dl> |
730 | <dl> |
487 | <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> |
731 | <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> |
488 | <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> |
732 | <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> |
489 | <dd> |
733 | <dd> |
490 | <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is |
734 | <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is |
… | |
… | |
492 | timer will automatically be configured to trigger again <code>repeat</code> seconds |
736 | timer will automatically be configured to trigger again <code>repeat</code> seconds |
493 | later, again, and again, until stopped manually.</p> |
737 | later, again, and again, until stopped manually.</p> |
494 | <p>The timer itself will do a best-effort at avoiding drift, that is, if you |
738 | <p>The timer itself will do a best-effort at avoiding drift, that is, if you |
495 | configure a timer to trigger every 10 seconds, then it will trigger at |
739 | configure a timer to trigger every 10 seconds, then it will trigger at |
496 | exactly 10 second intervals. If, however, your program cannot keep up with |
740 | exactly 10 second intervals. If, however, your program cannot keep up with |
497 | the timer (ecause it takes longer than those 10 seconds to do stuff) the |
741 | the timer (because it takes longer than those 10 seconds to do stuff) the |
498 | timer will not fire more than once per event loop iteration.</p> |
742 | timer will not fire more than once per event loop iteration.</p> |
499 | </dd> |
743 | </dd> |
500 | <dt>ev_timer_again (loop)</dt> |
744 | <dt>ev_timer_again (loop)</dt> |
501 | <dd> |
745 | <dd> |
502 | <p>This will act as if the timer timed out and restart it again if it is |
746 | <p>This will act as if the timer timed out and restart it again if it is |
… | |
… | |
512 | time you successfully read or write some data. If you go into an idle |
756 | time you successfully read or write some data. If you go into an idle |
513 | state where you do not expect data to travel on the socket, you can stop |
757 | state where you do not expect data to travel on the socket, you can stop |
514 | the timer, and again will automatically restart it if need be.</p> |
758 | the timer, and again will automatically restart it if need be.</p> |
515 | </dd> |
759 | </dd> |
516 | </dl> |
760 | </dl> |
|
|
761 | <p>Example: create a timer that fires after 60 seconds.</p> |
|
|
762 | <pre> static void |
|
|
763 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
|
|
764 | { |
|
|
765 | .. one minute over, w is actually stopped right here |
|
|
766 | } |
|
|
767 | |
|
|
768 | struct ev_timer mytimer; |
|
|
769 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
|
|
770 | ev_timer_start (loop, &mytimer); |
|
|
771 | |
|
|
772 | </pre> |
|
|
773 | <p>Example: create a timeout timer that times out after 10 seconds of |
|
|
774 | inactivity.</p> |
|
|
775 | <pre> static void |
|
|
776 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
|
|
777 | { |
|
|
778 | .. ten seconds without any activity |
|
|
779 | } |
|
|
780 | |
|
|
781 | struct ev_timer mytimer; |
|
|
782 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
|
|
783 | ev_timer_again (&mytimer); /* start timer */ |
|
|
784 | ev_loop (loop, 0); |
|
|
785 | |
|
|
786 | // and in some piece of code that gets executed on any "activity": |
|
|
787 | // reset the timeout to start ticking again at 10 seconds |
|
|
788 | ev_timer_again (&mytimer); |
|
|
789 | |
|
|
790 | |
|
|
791 | |
|
|
792 | |
|
|
793 | </pre> |
517 | |
794 | |
518 | </div> |
795 | </div> |
519 | <h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> |
796 | <h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> |
520 | <div id="code_ev_periodic_code_to_cron_or_not-2"> |
797 | <div id="code_ev_periodic_code_to_cron_or_not-2"> |
521 | <p>Periodic watchers are also timers of a kind, but they are very versatile |
798 | <p>Periodic watchers are also timers of a kind, but they are very versatile |
… | |
… | |
528 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
805 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
529 | roughly 10 seconds later and of course not if you reset your system time |
806 | roughly 10 seconds later and of course not if you reset your system time |
530 | again).</p> |
807 | again).</p> |
531 | <p>They can also be used to implement vastly more complex timers, such as |
808 | <p>They can also be used to implement vastly more complex timers, such as |
532 | triggering an event on eahc midnight, local time.</p> |
809 | triggering an event on eahc midnight, local time.</p> |
|
|
810 | <p>As with timers, the callback is guarenteed to be invoked only when the |
|
|
811 | time (<code>at</code>) has been passed, but if multiple periodic timers become ready |
|
|
812 | during the same loop iteration then order of execution is undefined.</p> |
533 | <dl> |
813 | <dl> |
534 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
814 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
535 | <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> |
815 | <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> |
536 | <dd> |
816 | <dd> |
537 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
817 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
538 | operation, and we will explain them from simplest to complex:</p> |
818 | operation, and we will explain them from simplest to complex:</p> |
539 | |
|
|
540 | |
|
|
541 | |
|
|
542 | |
|
|
543 | <p> |
819 | <p> |
544 | <dl> |
820 | <dl> |
545 | <dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
821 | <dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
546 | <dd> |
822 | <dd> |
547 | <p>In this configuration the watcher triggers an event at the wallclock time |
823 | <p>In this configuration the watcher triggers an event at the wallclock time |
… | |
… | |
606 | when you changed some parameters or the reschedule callback would return |
882 | when you changed some parameters or the reschedule callback would return |
607 | a different time than the last time it was called (e.g. in a crond like |
883 | a different time than the last time it was called (e.g. in a crond like |
608 | program when the crontabs have changed).</p> |
884 | program when the crontabs have changed).</p> |
609 | </dd> |
885 | </dd> |
610 | </dl> |
886 | </dl> |
|
|
887 | <p>Example: call a callback every hour, or, more precisely, whenever the |
|
|
888 | system clock is divisible by 3600. The callback invocation times have |
|
|
889 | potentially a lot of jittering, but good long-term stability.</p> |
|
|
890 | <pre> static void |
|
|
891 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
|
|
892 | { |
|
|
893 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
|
|
894 | } |
|
|
895 | |
|
|
896 | struct ev_periodic hourly_tick; |
|
|
897 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
|
|
898 | ev_periodic_start (loop, &hourly_tick); |
|
|
899 | |
|
|
900 | </pre> |
|
|
901 | <p>Example: the same as above, but use a reschedule callback to do it:</p> |
|
|
902 | <pre> #include <math.h> |
|
|
903 | |
|
|
904 | static ev_tstamp |
|
|
905 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
|
|
906 | { |
|
|
907 | return fmod (now, 3600.) + 3600.; |
|
|
908 | } |
|
|
909 | |
|
|
910 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
|
|
911 | |
|
|
912 | </pre> |
|
|
913 | <p>Example: call a callback every hour, starting now:</p> |
|
|
914 | <pre> struct ev_periodic hourly_tick; |
|
|
915 | ev_periodic_init (&hourly_tick, clock_cb, |
|
|
916 | fmod (ev_now (loop), 3600.), 3600., 0); |
|
|
917 | ev_periodic_start (loop, &hourly_tick); |
|
|
918 | |
|
|
919 | |
|
|
920 | |
|
|
921 | |
|
|
922 | </pre> |
611 | |
923 | |
612 | </div> |
924 | </div> |
613 | <h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> |
925 | <h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> |
614 | <div id="code_ev_signal_code_signal_me_when_a-2"> |
926 | <div id="code_ev_signal_code_signal_me_when_a-2"> |
615 | <p>Signal watchers will trigger an event when the process receives a specific |
927 | <p>Signal watchers will trigger an event when the process receives a specific |
… | |
… | |
629 | <p>Configures the watcher to trigger on the given signal number (usually one |
941 | <p>Configures the watcher to trigger on the given signal number (usually one |
630 | of the <code>SIGxxx</code> constants).</p> |
942 | of the <code>SIGxxx</code> constants).</p> |
631 | </dd> |
943 | </dd> |
632 | </dl> |
944 | </dl> |
633 | |
945 | |
|
|
946 | |
|
|
947 | |
|
|
948 | |
|
|
949 | |
634 | </div> |
950 | </div> |
635 | <h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> |
951 | <h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> |
636 | <div id="code_ev_child_code_wait_for_pid_stat-2"> |
952 | <div id="code_ev_child_code_wait_for_pid_stat-2"> |
637 | <p>Child watchers trigger when your process receives a SIGCHLD in response to |
953 | <p>Child watchers trigger when your process receives a SIGCHLD in response to |
638 | some child status changes (most typically when a child of yours dies).</p> |
954 | some child status changes (most typically when a child of yours dies).</p> |
… | |
… | |
646 | the status word (use the macros from <code>sys/wait.h</code> and see your systems |
962 | the status word (use the macros from <code>sys/wait.h</code> and see your systems |
647 | <code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the |
963 | <code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the |
648 | process causing the status change.</p> |
964 | process causing the status change.</p> |
649 | </dd> |
965 | </dd> |
650 | </dl> |
966 | </dl> |
|
|
967 | <p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> |
|
|
968 | <pre> static void |
|
|
969 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
|
|
970 | { |
|
|
971 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
972 | } |
|
|
973 | |
|
|
974 | struct ev_signal signal_watcher; |
|
|
975 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
976 | ev_signal_start (loop, &sigint_cb); |
|
|
977 | |
|
|
978 | |
|
|
979 | |
|
|
980 | |
|
|
981 | </pre> |
651 | |
982 | |
652 | </div> |
983 | </div> |
653 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> |
984 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> |
654 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
985 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
655 | <p>Idle watchers trigger events when there are no other events are pending |
986 | <p>Idle watchers trigger events when there are no other events are pending |
… | |
… | |
671 | <p>Initialises and configures the idle watcher - it has no parameters of any |
1002 | <p>Initialises and configures the idle watcher - it has no parameters of any |
672 | kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, |
1003 | kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, |
673 | believe me.</p> |
1004 | believe me.</p> |
674 | </dd> |
1005 | </dd> |
675 | </dl> |
1006 | </dl> |
|
|
1007 | <p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the |
|
|
1008 | callback, free it. Alos, use no error checking, as usual.</p> |
|
|
1009 | <pre> static void |
|
|
1010 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
|
|
1011 | { |
|
|
1012 | free (w); |
|
|
1013 | // now do something you wanted to do when the program has |
|
|
1014 | // no longer asnything immediate to do. |
|
|
1015 | } |
|
|
1016 | |
|
|
1017 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
|
|
1018 | ev_idle_init (idle_watcher, idle_cb); |
|
|
1019 | ev_idle_start (loop, idle_cb); |
|
|
1020 | |
|
|
1021 | |
|
|
1022 | |
|
|
1023 | |
|
|
1024 | </pre> |
676 | |
1025 | |
677 | </div> |
1026 | </div> |
678 | <h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> |
1027 | <h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> |
679 | <div id="code_ev_prepare_code_and_code_ev_che-2"> |
1028 | <div id="code_ev_prepare_code_and_code_ev_che-2"> |
680 | <p>Prepare and check watchers are usually (but not always) used in tandem: |
1029 | <p>Prepare and check watchers are usually (but not always) used in tandem: |
681 | prepare watchers get invoked before the process blocks and check watchers |
1030 | prepare watchers get invoked before the process blocks and check watchers |
682 | afterwards.</p> |
1031 | afterwards.</p> |
683 | <p>Their main purpose is to integrate other event mechanisms into libev. This |
1032 | <p>Their main purpose is to integrate other event mechanisms into libev and |
684 | could be used, for example, to track variable changes, implement your own |
1033 | their use is somewhat advanced. This could be used, for example, to track |
685 | watchers, integrate net-snmp or a coroutine library and lots more.</p> |
1034 | variable changes, implement your own watchers, integrate net-snmp or a |
|
|
1035 | coroutine library and lots more.</p> |
686 | <p>This is done by examining in each prepare call which file descriptors need |
1036 | <p>This is done by examining in each prepare call which file descriptors need |
687 | to be watched by the other library, registering <code>ev_io</code> watchers for |
1037 | to be watched by the other library, registering <code>ev_io</code> watchers for |
688 | them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries |
1038 | them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries |
689 | provide just this functionality). Then, in the check watcher you check for |
1039 | provide just this functionality). Then, in the check watcher you check for |
690 | any events that occured (by checking the pending status of all watchers |
1040 | any events that occured (by checking the pending status of all watchers |
… | |
… | |
706 | <p>Initialises and configures the prepare or check watcher - they have no |
1056 | <p>Initialises and configures the prepare or check watcher - they have no |
707 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1057 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
708 | macros, but using them is utterly, utterly and completely pointless.</p> |
1058 | macros, but using them is utterly, utterly and completely pointless.</p> |
709 | </dd> |
1059 | </dd> |
710 | </dl> |
1060 | </dl> |
|
|
1061 | <p>Example: *TODO*.</p> |
|
|
1062 | |
|
|
1063 | |
|
|
1064 | |
|
|
1065 | |
|
|
1066 | |
|
|
1067 | </div> |
|
|
1068 | <h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2> |
|
|
1069 | <div id="code_ev_embed_code_when_one_backend_-2"> |
|
|
1070 | <p>This is a rather advanced watcher type that lets you embed one event loop |
|
|
1071 | into another.</p> |
|
|
1072 | <p>There are primarily two reasons you would want that: work around bugs and |
|
|
1073 | prioritise I/O.</p> |
|
|
1074 | <p>As an example for a bug workaround, the kqueue backend might only support |
|
|
1075 | sockets on some platform, so it is unusable as generic backend, but you |
|
|
1076 | still want to make use of it because you have many sockets and it scales |
|
|
1077 | so nicely. In this case, you would create a kqueue-based loop and embed it |
|
|
1078 | into your default loop (which might use e.g. poll). Overall operation will |
|
|
1079 | be a bit slower because first libev has to poll and then call kevent, but |
|
|
1080 | at least you can use both at what they are best.</p> |
|
|
1081 | <p>As for prioritising I/O: rarely you have the case where some fds have |
|
|
1082 | to be watched and handled very quickly (with low latency), and even |
|
|
1083 | priorities and idle watchers might have too much overhead. In this case |
|
|
1084 | you would put all the high priority stuff in one loop and all the rest in |
|
|
1085 | a second one, and embed the second one in the first.</p> |
|
|
1086 | <p>As long as the watcher is started it will automatically handle events. The |
|
|
1087 | callback will be invoked whenever some events have been handled. You can |
|
|
1088 | set the callback to <code>0</code> to avoid having to specify one if you are not |
|
|
1089 | interested in that.</p> |
|
|
1090 | <p>Also, there have not currently been made special provisions for forking: |
|
|
1091 | when you fork, you not only have to call <code>ev_loop_fork</code> on both loops, |
|
|
1092 | but you will also have to stop and restart any <code>ev_embed</code> watchers |
|
|
1093 | yourself.</p> |
|
|
1094 | <p>Unfortunately, not all backends are embeddable, only the ones returned by |
|
|
1095 | <code>ev_embeddable_backends</code> are, which, unfortunately, does not include any |
|
|
1096 | portable one.</p> |
|
|
1097 | <p>So when you want to use this feature you will always have to be prepared |
|
|
1098 | that you cannot get an embeddable loop. The recommended way to get around |
|
|
1099 | this is to have a separate variables for your embeddable loop, try to |
|
|
1100 | create it, and if that fails, use the normal loop for everything:</p> |
|
|
1101 | <pre> struct ev_loop *loop_hi = ev_default_init (0); |
|
|
1102 | struct ev_loop *loop_lo = 0; |
|
|
1103 | struct ev_embed embed; |
|
|
1104 | |
|
|
1105 | // see if there is a chance of getting one that works |
|
|
1106 | // (remember that a flags value of 0 means autodetection) |
|
|
1107 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
|
|
1108 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
|
|
1109 | : 0; |
|
|
1110 | |
|
|
1111 | // if we got one, then embed it, otherwise default to loop_hi |
|
|
1112 | if (loop_lo) |
|
|
1113 | { |
|
|
1114 | ev_embed_init (&embed, 0, loop_lo); |
|
|
1115 | ev_embed_start (loop_hi, &embed); |
|
|
1116 | } |
|
|
1117 | else |
|
|
1118 | loop_lo = loop_hi; |
|
|
1119 | |
|
|
1120 | </pre> |
|
|
1121 | <dl> |
|
|
1122 | <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *loop)</dt> |
|
|
1123 | <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *loop)</dt> |
|
|
1124 | <dd> |
|
|
1125 | <p>Configures the watcher to embed the given loop, which must be embeddable.</p> |
|
|
1126 | </dd> |
|
|
1127 | </dl> |
|
|
1128 | |
|
|
1129 | |
|
|
1130 | |
|
|
1131 | |
711 | |
1132 | |
712 | </div> |
1133 | </div> |
713 | <h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
1134 | <h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
714 | <div id="OTHER_FUNCTIONS_CONTENT"> |
1135 | <div id="OTHER_FUNCTIONS_CONTENT"> |
715 | <p>There are some other functions of possible interest. Described. Here. Now.</p> |
1136 | <p>There are some other functions of possible interest. Described. Here. Now.</p> |
… | |
… | |
717 | <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> |
1138 | <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> |
718 | <dd> |
1139 | <dd> |
719 | <p>This function combines a simple timer and an I/O watcher, calls your |
1140 | <p>This function combines a simple timer and an I/O watcher, calls your |
720 | callback on whichever event happens first and automatically stop both |
1141 | callback on whichever event happens first and automatically stop both |
721 | watchers. This is useful if you want to wait for a single event on an fd |
1142 | watchers. This is useful if you want to wait for a single event on an fd |
722 | or timeout without havign to allocate/configure/start/stop/free one or |
1143 | or timeout without having to allocate/configure/start/stop/free one or |
723 | more watchers yourself.</p> |
1144 | more watchers yourself.</p> |
724 | <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events |
1145 | <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events |
725 | is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and |
1146 | is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and |
726 | <code>events</code> set will be craeted and started.</p> |
1147 | <code>events</code> set will be craeted and started.</p> |
727 | <p>If <code>timeout</code> is less than 0, then no timeout watcher will be |
1148 | <p>If <code>timeout</code> is less than 0, then no timeout watcher will be |
728 | started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and |
1149 | started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and |
729 | repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of |
1150 | repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of |
730 | dubious value.</p> |
1151 | dubious value.</p> |
731 | <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets |
1152 | <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets |
732 | passed an events set like normal event callbacks (with a combination of |
1153 | passed an <code>revents</code> set like normal event callbacks (a combination of |
733 | <code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> |
1154 | <code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> |
734 | value passed to <code>ev_once</code>:</p> |
1155 | value passed to <code>ev_once</code>:</p> |
735 | <pre> static void stdin_ready (int revents, void *arg) |
1156 | <pre> static void stdin_ready (int revents, void *arg) |
736 | { |
1157 | { |
737 | if (revents & EV_TIMEOUT) |
1158 | if (revents & EV_TIMEOUT) |
… | |
… | |
759 | <dd> |
1180 | <dd> |
760 | <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> |
1181 | <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> |
761 | </dd> |
1182 | </dd> |
762 | </dl> |
1183 | </dl> |
763 | |
1184 | |
|
|
1185 | |
|
|
1186 | |
|
|
1187 | |
|
|
1188 | |
764 | </div> |
1189 | </div> |
765 | <h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> |
1190 | <h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> |
766 | <div id="LIBEVENT_EMULATION_CONTENT"> |
1191 | <div id="LIBEVENT_EMULATION_CONTENT"> |
767 | <p>TBD.</p> |
1192 | <p>Libev offers a compatibility emulation layer for libevent. It cannot |
|
|
1193 | emulate the internals of libevent, so here are some usage hints:</p> |
|
|
1194 | <dl> |
|
|
1195 | <dt>* Use it by including <event.h>, as usual.</dt> |
|
|
1196 | <dt>* The following members are fully supported: ev_base, ev_callback, |
|
|
1197 | ev_arg, ev_fd, ev_res, ev_events.</dt> |
|
|
1198 | <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is |
|
|
1199 | maintained by libev, it does not work exactly the same way as in libevent (consider |
|
|
1200 | it a private API).</dt> |
|
|
1201 | <dt>* Priorities are not currently supported. Initialising priorities |
|
|
1202 | will fail and all watchers will have the same priority, even though there |
|
|
1203 | is an ev_pri field.</dt> |
|
|
1204 | <dt>* Other members are not supported.</dt> |
|
|
1205 | <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need |
|
|
1206 | to use the libev header file and library.</dt> |
|
|
1207 | </dl> |
768 | |
1208 | |
769 | </div> |
1209 | </div> |
770 | <h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> |
1210 | <h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> |
771 | <div id="C_SUPPORT_CONTENT"> |
1211 | <div id="C_SUPPORT_CONTENT"> |
772 | <p>TBD.</p> |
1212 | <p>TBD.</p> |