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.\" ======================================================================== |
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.\" |
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.IX Title "LIBEIO 3" |
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.TH LIBEIO 3 "2008-05-11" "libeio-1.0" "libeio - truly asynchronous POSIX I/O" |
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.\" For nroff, turn off justification. Always turn off hyphenation; it makes |
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.\" way too many mistakes in technical documents. |
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.if n .ad l |
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.nh |
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.SH "NAME" |
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libev \- a high performance full\-featured event loop written in C |
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.SH "SYNOPSIS" |
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.IX Header "SYNOPSIS" |
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.Vb 1 |
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\& #include <ev.h> |
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.Ve |
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.Sh "\s-1EXAMPLE\s0 \s-1PROGRAM\s0" |
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.IX Subsection "EXAMPLE PROGRAM" |
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.Vb 2 |
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\& // a single header file is required |
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\& #include <ev.h> |
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\& |
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\& // every watcher type has its own typedef\*(Aqd struct |
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\& // with the name ev_<type> |
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\& ev_io stdin_watcher; |
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\& ev_timer timeout_watcher; |
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\& |
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\& // all watcher callbacks have a similar signature |
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\& // this callback is called when data is readable on stdin |
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\& static void |
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\& stdin_cb (EV_P_ struct ev_io *w, int revents) |
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\& { |
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\& puts ("stdin ready"); |
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\& // for one\-shot events, one must manually stop the watcher |
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\& // with its corresponding stop function. |
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\& ev_io_stop (EV_A_ w); |
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\& |
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\& // this causes all nested ev_loop\*(Aqs to stop iterating |
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\& ev_unloop (EV_A_ EVUNLOOP_ALL); |
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\& } |
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\& |
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\& // another callback, this time for a time\-out |
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\& static void |
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\& timeout_cb (EV_P_ struct ev_timer *w, int revents) |
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\& { |
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\& puts ("timeout"); |
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\& // this causes the innermost ev_loop to stop iterating |
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\& ev_unloop (EV_A_ EVUNLOOP_ONE); |
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\& } |
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\& |
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\& int |
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\& main (void) |
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\& { |
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\& // use the default event loop unless you have special needs |
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\& struct ev_loop *loop = ev_default_loop (0); |
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\& |
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\& // initialise an io watcher, then start it |
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\& // this one will watch for stdin to become readable |
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\& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
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\& ev_io_start (loop, &stdin_watcher); |
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\& |
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\& // initialise a timer watcher, then start it |
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\& // simple non\-repeating 5.5 second timeout |
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\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
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\& ev_timer_start (loop, &timeout_watcher); |
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\& |
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\& // now wait for events to arrive |
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\& ev_loop (loop, 0); |
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\& |
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\& // unloop was called, so exit |
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\& return 0; |
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\& } |
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.Ve |
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.SH "DESCRIPTION" |
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.IX Header "DESCRIPTION" |
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The newest version of this document is also available as an html-formatted |
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web page you might find easier to navigate when reading it for the first |
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time: <http://cvs.schmorp.de/libev/ev.html>. |
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.PP |
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Libev is an event loop: you register interest in certain events (such as a |
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file descriptor being readable or a timeout occurring), and it will manage |
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these event sources and provide your program with events. |
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.PP |
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To do this, it must take more or less complete control over your process |
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(or thread) by executing the \fIevent loop\fR handler, and will then |
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communicate events via a callback mechanism. |
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.PP |
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You register interest in certain events by registering so-called \fIevent |
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watchers\fR, which are relatively small C structures you initialise with the |
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details of the event, and then hand it over to libev by \fIstarting\fR the |
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watcher. |
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.Sh "\s-1FEATURES\s0" |
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.IX Subsection "FEATURES" |
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Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the |
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BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms |
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for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface |
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(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers |
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with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals |
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(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event |
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watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, |
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\&\f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR watchers) as well as |
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file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events |
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(\f(CW\*(C`ev_fork\*(C'\fR). |
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.PP |
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It also is quite fast (see this |
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benchmark comparing it to libevent |
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for example). |
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.Sh "\s-1CONVENTIONS\s0" |
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.IX Subsection "CONVENTIONS" |
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Libev is very configurable. In this manual the default (and most common) |
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configuration will be described, which supports multiple event loops. For |
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more info about various configuration options please have a look at |
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\&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support |
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for multiple event loops, then all functions taking an initial argument of |
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name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have |
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this argument. |
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.Sh "\s-1TIME\s0 \s-1REPRESENTATION\s0" |
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.IX Subsection "TIME REPRESENTATION" |
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Libev represents time as a single floating point number, representing the |
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(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near |
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the beginning of 1970, details are complicated, don't ask). This type is |
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called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases |
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to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on |
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it, you should treat it as some floatingpoint value. Unlike the name |
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component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences |
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throughout libev. |
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.SH "GLOBAL FUNCTIONS" |
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.IX Header "GLOBAL FUNCTIONS" |
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These functions can be called anytime, even before initialising the |
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library in any way. |
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.IP "ev_tstamp ev_time ()" 4 |
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.IX Item "ev_tstamp ev_time ()" |
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Returns the current time as libev would use it. Please note that the |
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\&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp |
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you actually want to know. |
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.IP "ev_sleep (ev_tstamp interval)" 4 |
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.IX Item "ev_sleep (ev_tstamp interval)" |
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Sleep for the given interval: The current thread will be blocked until |
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either it is interrupted or the given time interval has passed. Basically |
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this is a subsecond-resolution \f(CW\*(C`sleep ()\*(C'\fR. |
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.IP "int ev_version_major ()" 4 |
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.IX Item "int ev_version_major ()" |
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.PD 0 |
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.IP "int ev_version_minor ()" 4 |
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.IX Item "int ev_version_minor ()" |
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.PD |
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You can find out the major and minor \s-1ABI\s0 version numbers of the library |
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you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and |
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\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global |
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symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the |
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version of the library your program was compiled against. |
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.Sp |
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These version numbers refer to the \s-1ABI\s0 version of the library, not the |
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release version. |
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.Sp |
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Usually, it's a good idea to terminate if the major versions mismatch, |
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as this indicates an incompatible change. Minor versions are usually |
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compatible to older versions, so a larger minor version alone is usually |
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not a problem. |
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.Sp |
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Example: Make sure we haven't accidentally been linked against the wrong |
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version. |
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.Sp |
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.Vb 3 |
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\& assert (("libev version mismatch", |
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\& ev_version_major () == EV_VERSION_MAJOR |
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\& && ev_version_minor () >= EV_VERSION_MINOR)); |
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.Ve |
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.IP "unsigned int ev_supported_backends ()" 4 |
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.IX Item "unsigned int ev_supported_backends ()" |
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Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR |
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value) compiled into this binary of libev (independent of their |
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availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for |
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a description of the set values. |
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.Sp |
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Example: make sure we have the epoll method, because yeah this is cool and |
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a must have and can we have a torrent of it please!!!11 |
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.Sp |
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.Vb 2 |
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\& assert (("sorry, no epoll, no sex", |
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\& ev_supported_backends () & EVBACKEND_EPOLL)); |
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.Ve |
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.IP "unsigned int ev_recommended_backends ()" 4 |
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.IX Item "unsigned int ev_recommended_backends ()" |
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Return the set of all backends compiled into this binary of libev and also |
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recommended for this platform. This set is often smaller than the one |
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returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on |
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most BSDs and will not be autodetected unless you explicitly request it |
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(assuming you know what you are doing). This is the set of backends that |
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|
|
libev will probe for if you specify no backends explicitly. |
321 |
|
|
.IP "unsigned int ev_embeddable_backends ()" 4 |
322 |
|
|
.IX Item "unsigned int ev_embeddable_backends ()" |
323 |
|
|
Returns the set of backends that are embeddable in other event loops. This |
324 |
|
|
is the theoretical, all-platform, value. To find which backends |
325 |
|
|
might be supported on the current system, you would need to look at |
326 |
|
|
\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for |
327 |
|
|
recommended ones. |
328 |
|
|
.Sp |
329 |
|
|
See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
330 |
|
|
.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 |
331 |
|
|
.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" |
332 |
|
|
Sets the allocation function to use (the prototype is similar \- the |
333 |
|
|
semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is |
334 |
|
|
used to allocate and free memory (no surprises here). If it returns zero |
335 |
|
|
when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort |
336 |
|
|
or take some potentially destructive action. |
337 |
|
|
.Sp |
338 |
|
|
Since some systems (at least OpenBSD and Darwin) fail to implement |
339 |
|
|
correct \f(CW\*(C`realloc\*(C'\fR semantics, libev will use a wrapper around the system |
340 |
|
|
\&\f(CW\*(C`realloc\*(C'\fR and \f(CW\*(C`free\*(C'\fR functions by default. |
341 |
|
|
.Sp |
342 |
|
|
You could override this function in high-availability programs to, say, |
343 |
|
|
free some memory if it cannot allocate memory, to use a special allocator, |
344 |
|
|
or even to sleep a while and retry until some memory is available. |
345 |
|
|
.Sp |
346 |
|
|
Example: Replace the libev allocator with one that waits a bit and then |
347 |
|
|
retries (example requires a standards-compliant \f(CW\*(C`realloc\*(C'\fR). |
348 |
|
|
.Sp |
349 |
|
|
.Vb 6 |
350 |
|
|
\& static void * |
351 |
|
|
\& persistent_realloc (void *ptr, size_t size) |
352 |
|
|
\& { |
353 |
|
|
\& for (;;) |
354 |
|
|
\& { |
355 |
|
|
\& void *newptr = realloc (ptr, size); |
356 |
|
|
\& |
357 |
|
|
\& if (newptr) |
358 |
|
|
\& return newptr; |
359 |
|
|
\& |
360 |
|
|
\& sleep (60); |
361 |
|
|
\& } |
362 |
|
|
\& } |
363 |
|
|
\& |
364 |
|
|
\& ... |
365 |
|
|
\& ev_set_allocator (persistent_realloc); |
366 |
|
|
.Ve |
367 |
|
|
.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 |
368 |
|
|
.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" |
369 |
|
|
Set the callback function to call on a retryable syscall error (such |
370 |
|
|
as failed select, poll, epoll_wait). The message is a printable string |
371 |
|
|
indicating the system call or subsystem causing the problem. If this |
372 |
|
|
callback is set, then libev will expect it to remedy the sitution, no |
373 |
|
|
matter what, when it returns. That is, libev will generally retry the |
374 |
|
|
requested operation, or, if the condition doesn't go away, do bad stuff |
375 |
|
|
(such as abort). |
376 |
|
|
.Sp |
377 |
|
|
Example: This is basically the same thing that libev does internally, too. |
378 |
|
|
.Sp |
379 |
|
|
.Vb 6 |
380 |
|
|
\& static void |
381 |
|
|
\& fatal_error (const char *msg) |
382 |
|
|
\& { |
383 |
|
|
\& perror (msg); |
384 |
|
|
\& abort (); |
385 |
|
|
\& } |
386 |
|
|
\& |
387 |
|
|
\& ... |
388 |
|
|
\& ev_set_syserr_cb (fatal_error); |
389 |
|
|
.Ve |
390 |
|
|
.SH "FUNCTIONS CONTROLLING THE EVENT LOOP" |
391 |
|
|
.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" |
392 |
|
|
An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two |
393 |
|
|
types of such loops, the \fIdefault\fR loop, which supports signals and child |
394 |
|
|
events, and dynamically created loops which do not. |
395 |
|
|
.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 |
396 |
|
|
.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" |
397 |
|
|
This will initialise the default event loop if it hasn't been initialised |
398 |
|
|
yet and return it. If the default loop could not be initialised, returns |
399 |
|
|
false. If it already was initialised it simply returns it (and ignores the |
400 |
|
|
flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards). |
401 |
|
|
.Sp |
402 |
|
|
If you don't know what event loop to use, use the one returned from this |
403 |
|
|
function. |
404 |
|
|
.Sp |
405 |
|
|
Note that this function is \fInot\fR thread-safe, so if you want to use it |
406 |
|
|
from multiple threads, you have to lock (note also that this is unlikely, |
407 |
|
|
as loops cannot bes hared easily between threads anyway). |
408 |
|
|
.Sp |
409 |
|
|
The default loop is the only loop that can handle \f(CW\*(C`ev_signal\*(C'\fR and |
410 |
|
|
\&\f(CW\*(C`ev_child\*(C'\fR watchers, and to do this, it always registers a handler |
411 |
|
|
for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is a problem for your app you can either |
412 |
|
|
create a dynamic loop with \f(CW\*(C`ev_loop_new\*(C'\fR that doesn't do that, or you |
413 |
|
|
can simply overwrite the \f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling |
414 |
|
|
\&\f(CW\*(C`ev_default_init\*(C'\fR. |
415 |
|
|
.Sp |
416 |
|
|
The flags argument can be used to specify special behaviour or specific |
417 |
|
|
backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). |
418 |
|
|
.Sp |
419 |
|
|
The following flags are supported: |
420 |
|
|
.RS 4 |
421 |
|
|
.ie n .IP """EVFLAG_AUTO""" 4 |
422 |
|
|
.el .IP "\f(CWEVFLAG_AUTO\fR" 4 |
423 |
|
|
.IX Item "EVFLAG_AUTO" |
424 |
|
|
The default flags value. Use this if you have no clue (it's the right |
425 |
|
|
thing, believe me). |
426 |
|
|
.ie n .IP """EVFLAG_NOENV""" 4 |
427 |
|
|
.el .IP "\f(CWEVFLAG_NOENV\fR" 4 |
428 |
|
|
.IX Item "EVFLAG_NOENV" |
429 |
|
|
If this flag bit is ored into the flag value (or the program runs setuid |
430 |
|
|
or setgid) then libev will \fInot\fR look at the environment variable |
431 |
|
|
\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will |
432 |
|
|
override the flags completely if it is found in the environment. This is |
433 |
|
|
useful to try out specific backends to test their performance, or to work |
434 |
|
|
around bugs. |
435 |
|
|
.ie n .IP """EVFLAG_FORKCHECK""" 4 |
436 |
|
|
.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4 |
437 |
|
|
.IX Item "EVFLAG_FORKCHECK" |
438 |
|
|
Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after |
439 |
|
|
a fork, you can also make libev check for a fork in each iteration by |
440 |
|
|
enabling this flag. |
441 |
|
|
.Sp |
442 |
|
|
This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop, |
443 |
|
|
and thus this might slow down your event loop if you do a lot of loop |
444 |
|
|
iterations and little real work, but is usually not noticeable (on my |
445 |
|
|
GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence |
446 |
|
|
without a syscall and thus \fIvery\fR fast, but my GNU/Linux system also has |
447 |
|
|
\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). |
448 |
|
|
.Sp |
449 |
|
|
The big advantage of this flag is that you can forget about fork (and |
450 |
|
|
forget about forgetting to tell libev about forking) when you use this |
451 |
|
|
flag. |
452 |
|
|
.Sp |
453 |
|
|
This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR |
454 |
|
|
environment variable. |
455 |
|
|
.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
456 |
|
|
.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
457 |
|
|
.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
458 |
|
|
This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
459 |
|
|
libev tries to roll its own fd_set with no limits on the number of fds, |
460 |
|
|
but if that fails, expect a fairly low limit on the number of fds when |
461 |
|
|
using this backend. It doesn't scale too well (O(highest_fd)), but its |
462 |
|
|
usually the fastest backend for a low number of (low-numbered :) fds. |
463 |
|
|
.Sp |
464 |
|
|
To get good performance out of this backend you need a high amount of |
465 |
|
|
parallelity (most of the file descriptors should be busy). If you are |
466 |
|
|
writing a server, you should \f(CW\*(C`accept ()\*(C'\fR in a loop to accept as many |
467 |
|
|
connections as possible during one iteration. You might also want to have |
468 |
|
|
a look at \f(CW\*(C`ev_set_io_collect_interval ()\*(C'\fR to increase the amount of |
469 |
|
|
readyness notifications you get per iteration. |
470 |
|
|
.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 |
471 |
|
|
.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 |
472 |
|
|
.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" |
473 |
|
|
And this is your standard \fIpoll\fR\|(2) backend. It's more complicated |
474 |
|
|
than select, but handles sparse fds better and has no artificial |
475 |
|
|
limit on the number of fds you can use (except it will slow down |
476 |
|
|
considerably with a lot of inactive fds). It scales similarly to select, |
477 |
|
|
i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for |
478 |
|
|
performance tips. |
479 |
|
|
.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 |
480 |
|
|
.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
481 |
|
|
.IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
482 |
|
|
For few fds, this backend is a bit little slower than poll and select, |
483 |
|
|
but it scales phenomenally better. While poll and select usually scale |
484 |
|
|
like O(total_fds) where n is the total number of fds (or the highest fd), |
485 |
|
|
epoll scales either O(1) or O(active_fds). The epoll design has a number |
486 |
|
|
of shortcomings, such as silently dropping events in some hard-to-detect |
487 |
|
|
cases and requiring a syscall per fd change, no fork support and bad |
488 |
|
|
support for dup. |
489 |
|
|
.Sp |
490 |
|
|
While stopping, setting and starting an I/O watcher in the same iteration |
491 |
|
|
will result in some caching, there is still a syscall per such incident |
492 |
|
|
(because the fd could point to a different file description now), so its |
493 |
|
|
best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors might not work |
494 |
|
|
very well if you register events for both fds. |
495 |
|
|
.Sp |
496 |
|
|
Please note that epoll sometimes generates spurious notifications, so you |
497 |
|
|
need to use non-blocking I/O or other means to avoid blocking when no data |
498 |
|
|
(or space) is available. |
499 |
|
|
.Sp |
500 |
|
|
Best performance from this backend is achieved by not unregistering all |
501 |
|
|
watchers for a file descriptor until it has been closed, if possible, i.e. |
502 |
|
|
keep at least one watcher active per fd at all times. |
503 |
|
|
.Sp |
504 |
|
|
While nominally embeddeble in other event loops, this feature is broken in |
505 |
|
|
all kernel versions tested so far. |
506 |
|
|
.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
507 |
|
|
.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
508 |
|
|
.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
509 |
|
|
Kqueue deserves special mention, as at the time of this writing, it |
510 |
|
|
was broken on all BSDs except NetBSD (usually it doesn't work reliably |
511 |
|
|
with anything but sockets and pipes, except on Darwin, where of course |
512 |
|
|
it's completely useless). For this reason it's not being \*(L"autodetected\*(R" |
513 |
|
|
unless you explicitly specify it explicitly in the flags (i.e. using |
514 |
|
|
\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough) |
515 |
|
|
system like NetBSD. |
516 |
|
|
.Sp |
517 |
|
|
You still can embed kqueue into a normal poll or select backend and use it |
518 |
|
|
only for sockets (after having made sure that sockets work with kqueue on |
519 |
|
|
the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
520 |
|
|
.Sp |
521 |
|
|
It scales in the same way as the epoll backend, but the interface to the |
522 |
|
|
kernel is more efficient (which says nothing about its actual speed, of |
523 |
|
|
course). While stopping, setting and starting an I/O watcher does never |
524 |
|
|
cause an extra syscall as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to |
525 |
|
|
two event changes per incident, support for \f(CW\*(C`fork ()\*(C'\fR is very bad and it |
526 |
|
|
drops fds silently in similarly hard-to-detect cases. |
527 |
|
|
.Sp |
528 |
|
|
This backend usually performs well under most conditions. |
529 |
|
|
.Sp |
530 |
|
|
While nominally embeddable in other event loops, this doesn't work |
531 |
|
|
everywhere, so you might need to test for this. And since it is broken |
532 |
|
|
almost everywhere, you should only use it when you have a lot of sockets |
533 |
|
|
(for which it usually works), by embedding it into another event loop |
534 |
|
|
(e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR) and using it only for |
535 |
|
|
sockets. |
536 |
|
|
.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 |
537 |
|
|
.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 |
538 |
|
|
.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" |
539 |
|
|
This is not implemented yet (and might never be, unless you send me an |
540 |
|
|
implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets |
541 |
|
|
and is not embeddable, which would limit the usefulness of this backend |
542 |
|
|
immensely. |
543 |
|
|
.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 |
544 |
|
|
.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 |
545 |
|
|
.IX Item "EVBACKEND_PORT (value 32, Solaris 10)" |
546 |
|
|
This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
547 |
|
|
it's really slow, but it still scales very well (O(active_fds)). |
548 |
|
|
.Sp |
549 |
|
|
Please note that solaris event ports can deliver a lot of spurious |
550 |
|
|
notifications, so you need to use non-blocking I/O or other means to avoid |
551 |
|
|
blocking when no data (or space) is available. |
552 |
|
|
.Sp |
553 |
|
|
While this backend scales well, it requires one system call per active |
554 |
|
|
file descriptor per loop iteration. For small and medium numbers of file |
555 |
|
|
descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend |
556 |
|
|
might perform better. |
557 |
|
|
.Sp |
558 |
|
|
On the positive side, ignoring the spurious readyness notifications, this |
559 |
|
|
backend actually performed to specification in all tests and is fully |
560 |
|
|
embeddable, which is a rare feat among the OS-specific backends. |
561 |
|
|
.ie n .IP """EVBACKEND_ALL""" 4 |
562 |
|
|
.el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
563 |
|
|
.IX Item "EVBACKEND_ALL" |
564 |
|
|
Try all backends (even potentially broken ones that wouldn't be tried |
565 |
|
|
with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as |
566 |
|
|
\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. |
567 |
|
|
.Sp |
568 |
|
|
It is definitely not recommended to use this flag. |
569 |
|
|
.RE |
570 |
|
|
.RS 4 |
571 |
|
|
.Sp |
572 |
|
|
If one or more of these are ored into the flags value, then only these |
573 |
|
|
backends will be tried (in the reverse order as listed here). If none are |
574 |
|
|
specified, all backends in \f(CW\*(C`ev_recommended_backends ()\*(C'\fR will be tried. |
575 |
|
|
.Sp |
576 |
|
|
The most typical usage is like this: |
577 |
|
|
.Sp |
578 |
|
|
.Vb 2 |
579 |
|
|
\& if (!ev_default_loop (0)) |
580 |
|
|
\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
581 |
|
|
.Ve |
582 |
|
|
.Sp |
583 |
|
|
Restrict libev to the select and poll backends, and do not allow |
584 |
|
|
environment settings to be taken into account: |
585 |
|
|
.Sp |
586 |
|
|
.Vb 1 |
587 |
|
|
\& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
588 |
|
|
.Ve |
589 |
|
|
.Sp |
590 |
|
|
Use whatever libev has to offer, but make sure that kqueue is used if |
591 |
|
|
available (warning, breaks stuff, best use only with your own private |
592 |
|
|
event loop and only if you know the \s-1OS\s0 supports your types of fds): |
593 |
|
|
.Sp |
594 |
|
|
.Vb 1 |
595 |
|
|
\& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
596 |
|
|
.Ve |
597 |
|
|
.RE |
598 |
|
|
.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 |
599 |
|
|
.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" |
600 |
|
|
Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is |
601 |
|
|
always distinct from the default loop. Unlike the default loop, it cannot |
602 |
|
|
handle signal and child watchers, and attempts to do so will be greeted by |
603 |
|
|
undefined behaviour (or a failed assertion if assertions are enabled). |
604 |
|
|
.Sp |
605 |
|
|
Note that this function \fIis\fR thread-safe, and the recommended way to use |
606 |
|
|
libev with threads is indeed to create one loop per thread, and using the |
607 |
|
|
default loop in the \*(L"main\*(R" or \*(L"initial\*(R" thread. |
608 |
|
|
.Sp |
609 |
|
|
Example: Try to create a event loop that uses epoll and nothing else. |
610 |
|
|
.Sp |
611 |
|
|
.Vb 3 |
612 |
|
|
\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
613 |
|
|
\& if (!epoller) |
614 |
|
|
\& fatal ("no epoll found here, maybe it hides under your chair"); |
615 |
|
|
.Ve |
616 |
|
|
.IP "ev_default_destroy ()" 4 |
617 |
|
|
.IX Item "ev_default_destroy ()" |
618 |
|
|
Destroys the default loop again (frees all memory and kernel state |
619 |
|
|
etc.). None of the active event watchers will be stopped in the normal |
620 |
|
|
sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your |
621 |
|
|
responsibility to either stop all watchers cleanly yoursef \fIbefore\fR |
622 |
|
|
calling this function, or cope with the fact afterwards (which is usually |
623 |
|
|
the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them |
624 |
|
|
for example). |
625 |
|
|
.Sp |
626 |
|
|
Note that certain global state, such as signal state, will not be freed by |
627 |
|
|
this function, and related watchers (such as signal and child watchers) |
628 |
|
|
would need to be stopped manually. |
629 |
|
|
.Sp |
630 |
|
|
In general it is not advisable to call this function except in the |
631 |
|
|
rare occasion where you really need to free e.g. the signal handling |
632 |
|
|
pipe fds. If you need dynamically allocated loops it is better to use |
633 |
|
|
\&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR). |
634 |
|
|
.IP "ev_loop_destroy (loop)" 4 |
635 |
|
|
.IX Item "ev_loop_destroy (loop)" |
636 |
|
|
Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an |
637 |
|
|
earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. |
638 |
|
|
.IP "ev_default_fork ()" 4 |
639 |
|
|
.IX Item "ev_default_fork ()" |
640 |
|
|
This function sets a flag that causes subsequent \f(CW\*(C`ev_loop\*(C'\fR iterations |
641 |
|
|
to reinitialise the kernel state for backends that have one. Despite the |
642 |
|
|
name, you can call it anytime, but it makes most sense after forking, in |
643 |
|
|
the child process (or both child and parent, but that again makes little |
644 |
|
|
sense). You \fImust\fR call it in the child before using any of the libev |
645 |
|
|
functions, and it will only take effect at the next \f(CW\*(C`ev_loop\*(C'\fR iteration. |
646 |
|
|
.Sp |
647 |
|
|
On the other hand, you only need to call this function in the child |
648 |
|
|
process if and only if you want to use the event library in the child. If |
649 |
|
|
you just fork+exec, you don't have to call it at all. |
650 |
|
|
.Sp |
651 |
|
|
The function itself is quite fast and it's usually not a problem to call |
652 |
|
|
it just in case after a fork. To make this easy, the function will fit in |
653 |
|
|
quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR: |
654 |
|
|
.Sp |
655 |
|
|
.Vb 1 |
656 |
|
|
\& pthread_atfork (0, 0, ev_default_fork); |
657 |
|
|
.Ve |
658 |
|
|
.IP "ev_loop_fork (loop)" 4 |
659 |
|
|
.IX Item "ev_loop_fork (loop)" |
660 |
|
|
Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by |
661 |
|
|
\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop |
662 |
|
|
after fork, and how you do this is entirely your own problem. |
663 |
|
|
.IP "int ev_is_default_loop (loop)" 4 |
664 |
|
|
.IX Item "int ev_is_default_loop (loop)" |
665 |
|
|
Returns true when the given loop actually is the default loop, false otherwise. |
666 |
|
|
.IP "unsigned int ev_loop_count (loop)" 4 |
667 |
|
|
.IX Item "unsigned int ev_loop_count (loop)" |
668 |
|
|
Returns the count of loop iterations for the loop, which is identical to |
669 |
|
|
the number of times libev did poll for new events. It starts at \f(CW0\fR and |
670 |
|
|
happily wraps around with enough iterations. |
671 |
|
|
.Sp |
672 |
|
|
This value can sometimes be useful as a generation counter of sorts (it |
673 |
|
|
\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with |
674 |
|
|
\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls. |
675 |
|
|
.IP "unsigned int ev_backend (loop)" 4 |
676 |
|
|
.IX Item "unsigned int ev_backend (loop)" |
677 |
|
|
Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in |
678 |
|
|
use. |
679 |
|
|
.IP "ev_tstamp ev_now (loop)" 4 |
680 |
|
|
.IX Item "ev_tstamp ev_now (loop)" |
681 |
|
|
Returns the current \*(L"event loop time\*(R", which is the time the event loop |
682 |
|
|
received events and started processing them. This timestamp does not |
683 |
|
|
change as long as callbacks are being processed, and this is also the base |
684 |
|
|
time used for relative timers. You can treat it as the timestamp of the |
685 |
|
|
event occurring (or more correctly, libev finding out about it). |
686 |
|
|
.IP "ev_loop (loop, int flags)" 4 |
687 |
|
|
.IX Item "ev_loop (loop, int flags)" |
688 |
|
|
Finally, this is it, the event handler. This function usually is called |
689 |
|
|
after you initialised all your watchers and you want to start handling |
690 |
|
|
events. |
691 |
|
|
.Sp |
692 |
|
|
If the flags argument is specified as \f(CW0\fR, it will not return until |
693 |
|
|
either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. |
694 |
|
|
.Sp |
695 |
|
|
Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than |
696 |
|
|
relying on all watchers to be stopped when deciding when a program has |
697 |
|
|
finished (especially in interactive programs), but having a program that |
698 |
|
|
automatically loops as long as it has to and no longer by virtue of |
699 |
|
|
relying on its watchers stopping correctly is a thing of beauty. |
700 |
|
|
.Sp |
701 |
|
|
A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle |
702 |
|
|
those events and any outstanding ones, but will not block your process in |
703 |
|
|
case there are no events and will return after one iteration of the loop. |
704 |
|
|
.Sp |
705 |
|
|
A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if |
706 |
|
|
neccessary) and will handle those and any outstanding ones. It will block |
707 |
|
|
your process until at least one new event arrives, and will return after |
708 |
|
|
one iteration of the loop. This is useful if you are waiting for some |
709 |
|
|
external event in conjunction with something not expressible using other |
710 |
|
|
libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is |
711 |
|
|
usually a better approach for this kind of thing. |
712 |
|
|
.Sp |
713 |
|
|
Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: |
714 |
|
|
.Sp |
715 |
|
|
.Vb 10 |
716 |
|
|
\& \- Before the first iteration, call any pending watchers. |
717 |
|
|
\& * If EVFLAG_FORKCHECK was used, check for a fork. |
718 |
|
|
\& \- If a fork was detected, queue and call all fork watchers. |
719 |
|
|
\& \- Queue and call all prepare watchers. |
720 |
|
|
\& \- If we have been forked, recreate the kernel state. |
721 |
|
|
\& \- Update the kernel state with all outstanding changes. |
722 |
|
|
\& \- Update the "event loop time". |
723 |
|
|
\& \- Calculate for how long to sleep or block, if at all |
724 |
|
|
\& (active idle watchers, EVLOOP_NONBLOCK or not having |
725 |
|
|
\& any active watchers at all will result in not sleeping). |
726 |
|
|
\& \- Sleep if the I/O and timer collect interval say so. |
727 |
|
|
\& \- Block the process, waiting for any events. |
728 |
|
|
\& \- Queue all outstanding I/O (fd) events. |
729 |
|
|
\& \- Update the "event loop time" and do time jump handling. |
730 |
|
|
\& \- Queue all outstanding timers. |
731 |
|
|
\& \- Queue all outstanding periodics. |
732 |
|
|
\& \- If no events are pending now, queue all idle watchers. |
733 |
|
|
\& \- Queue all check watchers. |
734 |
|
|
\& \- Call all queued watchers in reverse order (i.e. check watchers first). |
735 |
|
|
\& Signals and child watchers are implemented as I/O watchers, and will |
736 |
|
|
\& be handled here by queueing them when their watcher gets executed. |
737 |
|
|
\& \- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
738 |
|
|
\& were used, or there are no active watchers, return, otherwise |
739 |
|
|
\& continue with step *. |
740 |
|
|
.Ve |
741 |
|
|
.Sp |
742 |
|
|
Example: Queue some jobs and then loop until no events are outstanding |
743 |
|
|
anymore. |
744 |
|
|
.Sp |
745 |
|
|
.Vb 4 |
746 |
|
|
\& ... queue jobs here, make sure they register event watchers as long |
747 |
|
|
\& ... as they still have work to do (even an idle watcher will do..) |
748 |
|
|
\& ev_loop (my_loop, 0); |
749 |
|
|
\& ... jobs done. yeah! |
750 |
|
|
.Ve |
751 |
|
|
.IP "ev_unloop (loop, how)" 4 |
752 |
|
|
.IX Item "ev_unloop (loop, how)" |
753 |
|
|
Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it |
754 |
|
|
has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
755 |
|
|
\&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or |
756 |
|
|
\&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. |
757 |
|
|
.Sp |
758 |
|
|
This \*(L"unloop state\*(R" will be cleared when entering \f(CW\*(C`ev_loop\*(C'\fR again. |
759 |
|
|
.IP "ev_ref (loop)" 4 |
760 |
|
|
.IX Item "ev_ref (loop)" |
761 |
|
|
.PD 0 |
762 |
|
|
.IP "ev_unref (loop)" 4 |
763 |
|
|
.IX Item "ev_unref (loop)" |
764 |
|
|
.PD |
765 |
|
|
Ref/unref can be used to add or remove a reference count on the event |
766 |
|
|
loop: Every watcher keeps one reference, and as long as the reference |
767 |
|
|
count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. If you have |
768 |
|
|
a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from |
769 |
|
|
returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For |
770 |
|
|
example, libev itself uses this for its internal signal pipe: It is not |
771 |
|
|
visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if |
772 |
|
|
no event watchers registered by it are active. It is also an excellent |
773 |
|
|
way to do this for generic recurring timers or from within third-party |
774 |
|
|
libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR |
775 |
|
|
(but only if the watcher wasn't active before, or was active before, |
776 |
|
|
respectively). |
777 |
|
|
.Sp |
778 |
|
|
Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR |
779 |
|
|
running when nothing else is active. |
780 |
|
|
.Sp |
781 |
|
|
.Vb 4 |
782 |
|
|
\& struct ev_signal exitsig; |
783 |
|
|
\& ev_signal_init (&exitsig, sig_cb, SIGINT); |
784 |
|
|
\& ev_signal_start (loop, &exitsig); |
785 |
|
|
\& evf_unref (loop); |
786 |
|
|
.Ve |
787 |
|
|
.Sp |
788 |
|
|
Example: For some weird reason, unregister the above signal handler again. |
789 |
|
|
.Sp |
790 |
|
|
.Vb 2 |
791 |
|
|
\& ev_ref (loop); |
792 |
|
|
\& ev_signal_stop (loop, &exitsig); |
793 |
|
|
.Ve |
794 |
|
|
.IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4 |
795 |
|
|
.IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)" |
796 |
|
|
.PD 0 |
797 |
|
|
.IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4 |
798 |
|
|
.IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" |
799 |
|
|
.PD |
800 |
|
|
These advanced functions influence the time that libev will spend waiting |
801 |
|
|
for events. Both are by default \f(CW0\fR, meaning that libev will try to |
802 |
|
|
invoke timer/periodic callbacks and I/O callbacks with minimum latency. |
803 |
|
|
.Sp |
804 |
|
|
Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR) |
805 |
|
|
allows libev to delay invocation of I/O and timer/periodic callbacks to |
806 |
|
|
increase efficiency of loop iterations. |
807 |
|
|
.Sp |
808 |
|
|
The background is that sometimes your program runs just fast enough to |
809 |
|
|
handle one (or very few) event(s) per loop iteration. While this makes |
810 |
|
|
the program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new |
811 |
|
|
events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high |
812 |
|
|
overhead for the actual polling but can deliver many events at once. |
813 |
|
|
.Sp |
814 |
|
|
By setting a higher \fIio collect interval\fR you allow libev to spend more |
815 |
|
|
time collecting I/O events, so you can handle more events per iteration, |
816 |
|
|
at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and |
817 |
|
|
\&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null value will |
818 |
|
|
introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. |
819 |
|
|
.Sp |
820 |
|
|
Likewise, by setting a higher \fItimeout collect interval\fR you allow libev |
821 |
|
|
to spend more time collecting timeouts, at the expense of increased |
822 |
|
|
latency (the watcher callback will be called later). \f(CW\*(C`ev_io\*(C'\fR watchers |
823 |
|
|
will not be affected. Setting this to a non-null value will not introduce |
824 |
|
|
any overhead in libev. |
825 |
|
|
.Sp |
826 |
|
|
Many (busy) programs can usually benefit by setting the io collect |
827 |
|
|
interval to a value near \f(CW0.1\fR or so, which is often enough for |
828 |
|
|
interactive servers (of course not for games), likewise for timeouts. It |
829 |
|
|
usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR, |
830 |
|
|
as this approsaches the timing granularity of most systems. |
831 |
|
|
.SH "ANATOMY OF A WATCHER" |
832 |
|
|
.IX Header "ANATOMY OF A WATCHER" |
833 |
|
|
A watcher is a structure that you create and register to record your |
834 |
|
|
interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to |
835 |
|
|
become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: |
836 |
|
|
.PP |
837 |
|
|
.Vb 5 |
838 |
|
|
\& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
839 |
|
|
\& { |
840 |
|
|
\& ev_io_stop (w); |
841 |
|
|
\& ev_unloop (loop, EVUNLOOP_ALL); |
842 |
|
|
\& } |
843 |
|
|
\& |
844 |
|
|
\& struct ev_loop *loop = ev_default_loop (0); |
845 |
|
|
\& struct ev_io stdin_watcher; |
846 |
|
|
\& ev_init (&stdin_watcher, my_cb); |
847 |
|
|
\& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
848 |
|
|
\& ev_io_start (loop, &stdin_watcher); |
849 |
|
|
\& ev_loop (loop, 0); |
850 |
|
|
.Ve |
851 |
|
|
.PP |
852 |
|
|
As you can see, you are responsible for allocating the memory for your |
853 |
|
|
watcher structures (and it is usually a bad idea to do this on the stack, |
854 |
|
|
although this can sometimes be quite valid). |
855 |
|
|
.PP |
856 |
|
|
Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init |
857 |
|
|
(watcher *, callback)\*(C'\fR, which expects a callback to be provided. This |
858 |
|
|
callback gets invoked each time the event occurs (or, in the case of io |
859 |
|
|
watchers, each time the event loop detects that the file descriptor given |
860 |
|
|
is readable and/or writable). |
861 |
|
|
.PP |
862 |
|
|
Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro |
863 |
|
|
with arguments specific to this watcher type. There is also a macro |
864 |
|
|
to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init |
865 |
|
|
(watcher *, callback, ...)\*(C'\fR. |
866 |
|
|
.PP |
867 |
|
|
To make the watcher actually watch out for events, you have to start it |
868 |
|
|
with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher |
869 |
|
|
*)\*(C'\fR), and you can stop watching for events at any time by calling the |
870 |
|
|
corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. |
871 |
|
|
.PP |
872 |
|
|
As long as your watcher is active (has been started but not stopped) you |
873 |
|
|
must not touch the values stored in it. Most specifically you must never |
874 |
|
|
reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro. |
875 |
|
|
.PP |
876 |
|
|
Each and every callback receives the event loop pointer as first, the |
877 |
|
|
registered watcher structure as second, and a bitset of received events as |
878 |
|
|
third argument. |
879 |
|
|
.PP |
880 |
|
|
The received events usually include a single bit per event type received |
881 |
|
|
(you can receive multiple events at the same time). The possible bit masks |
882 |
|
|
are: |
883 |
|
|
.ie n .IP """EV_READ""" 4 |
884 |
|
|
.el .IP "\f(CWEV_READ\fR" 4 |
885 |
|
|
.IX Item "EV_READ" |
886 |
|
|
.PD 0 |
887 |
|
|
.ie n .IP """EV_WRITE""" 4 |
888 |
|
|
.el .IP "\f(CWEV_WRITE\fR" 4 |
889 |
|
|
.IX Item "EV_WRITE" |
890 |
|
|
.PD |
891 |
|
|
The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or |
892 |
|
|
writable. |
893 |
|
|
.ie n .IP """EV_TIMEOUT""" 4 |
894 |
|
|
.el .IP "\f(CWEV_TIMEOUT\fR" 4 |
895 |
|
|
.IX Item "EV_TIMEOUT" |
896 |
|
|
The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out. |
897 |
|
|
.ie n .IP """EV_PERIODIC""" 4 |
898 |
|
|
.el .IP "\f(CWEV_PERIODIC\fR" 4 |
899 |
|
|
.IX Item "EV_PERIODIC" |
900 |
|
|
The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out. |
901 |
|
|
.ie n .IP """EV_SIGNAL""" 4 |
902 |
|
|
.el .IP "\f(CWEV_SIGNAL\fR" 4 |
903 |
|
|
.IX Item "EV_SIGNAL" |
904 |
|
|
The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. |
905 |
|
|
.ie n .IP """EV_CHILD""" 4 |
906 |
|
|
.el .IP "\f(CWEV_CHILD\fR" 4 |
907 |
|
|
.IX Item "EV_CHILD" |
908 |
|
|
The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. |
909 |
|
|
.ie n .IP """EV_STAT""" 4 |
910 |
|
|
.el .IP "\f(CWEV_STAT\fR" 4 |
911 |
|
|
.IX Item "EV_STAT" |
912 |
|
|
The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow. |
913 |
|
|
.ie n .IP """EV_IDLE""" 4 |
914 |
|
|
.el .IP "\f(CWEV_IDLE\fR" 4 |
915 |
|
|
.IX Item "EV_IDLE" |
916 |
|
|
The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. |
917 |
|
|
.ie n .IP """EV_PREPARE""" 4 |
918 |
|
|
.el .IP "\f(CWEV_PREPARE\fR" 4 |
919 |
|
|
.IX Item "EV_PREPARE" |
920 |
|
|
.PD 0 |
921 |
|
|
.ie n .IP """EV_CHECK""" 4 |
922 |
|
|
.el .IP "\f(CWEV_CHECK\fR" 4 |
923 |
|
|
.IX Item "EV_CHECK" |
924 |
|
|
.PD |
925 |
|
|
All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_loop\*(C'\fR starts |
926 |
|
|
to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after |
927 |
|
|
\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any |
928 |
|
|
received events. Callbacks of both watcher types can start and stop as |
929 |
|
|
many watchers as they want, and all of them will be taken into account |
930 |
|
|
(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep |
931 |
|
|
\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). |
932 |
|
|
.ie n .IP """EV_EMBED""" 4 |
933 |
|
|
.el .IP "\f(CWEV_EMBED\fR" 4 |
934 |
|
|
.IX Item "EV_EMBED" |
935 |
|
|
The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention. |
936 |
|
|
.ie n .IP """EV_FORK""" 4 |
937 |
|
|
.el .IP "\f(CWEV_FORK\fR" 4 |
938 |
|
|
.IX Item "EV_FORK" |
939 |
|
|
The event loop has been resumed in the child process after fork (see |
940 |
|
|
\&\f(CW\*(C`ev_fork\*(C'\fR). |
941 |
|
|
.ie n .IP """EV_ASYNC""" 4 |
942 |
|
|
.el .IP "\f(CWEV_ASYNC\fR" 4 |
943 |
|
|
.IX Item "EV_ASYNC" |
944 |
|
|
The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR). |
945 |
|
|
.ie n .IP """EV_ERROR""" 4 |
946 |
|
|
.el .IP "\f(CWEV_ERROR\fR" 4 |
947 |
|
|
.IX Item "EV_ERROR" |
948 |
|
|
An unspecified error has occured, the watcher has been stopped. This might |
949 |
|
|
happen because the watcher could not be properly started because libev |
950 |
|
|
ran out of memory, a file descriptor was found to be closed or any other |
951 |
|
|
problem. You best act on it by reporting the problem and somehow coping |
952 |
|
|
with the watcher being stopped. |
953 |
|
|
.Sp |
954 |
|
|
Libev will usually signal a few \*(L"dummy\*(R" events together with an error, |
955 |
|
|
for example it might indicate that a fd is readable or writable, and if |
956 |
|
|
your callbacks is well-written it can just attempt the operation and cope |
957 |
|
|
with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded |
958 |
|
|
programs, though, so beware. |
959 |
|
|
.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" |
960 |
|
|
.IX Subsection "GENERIC WATCHER FUNCTIONS" |
961 |
|
|
In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type, |
962 |
|
|
e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers. |
963 |
|
|
.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 |
964 |
|
|
.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 |
965 |
|
|
.IX Item "ev_init (ev_TYPE *watcher, callback)" |
966 |
|
|
This macro initialises the generic portion of a watcher. The contents |
967 |
|
|
of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only |
968 |
|
|
the generic parts of the watcher are initialised, you \fIneed\fR to call |
969 |
|
|
the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the |
970 |
|
|
type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro |
971 |
|
|
which rolls both calls into one. |
972 |
|
|
.Sp |
973 |
|
|
You can reinitialise a watcher at any time as long as it has been stopped |
974 |
|
|
(or never started) and there are no pending events outstanding. |
975 |
|
|
.Sp |
976 |
|
|
The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, |
977 |
|
|
int revents)\*(C'\fR. |
978 |
|
|
.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 |
979 |
|
|
.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 |
980 |
|
|
.IX Item "ev_TYPE_set (ev_TYPE *, [args])" |
981 |
|
|
This macro initialises the type-specific parts of a watcher. You need to |
982 |
|
|
call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can |
983 |
|
|
call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this |
984 |
|
|
macro on a watcher that is active (it can be pending, however, which is a |
985 |
|
|
difference to the \f(CW\*(C`ev_init\*(C'\fR macro). |
986 |
|
|
.Sp |
987 |
|
|
Although some watcher types do not have type-specific arguments |
988 |
|
|
(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro. |
989 |
|
|
.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4 |
990 |
|
|
.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4 |
991 |
|
|
.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])" |
992 |
|
|
This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro |
993 |
|
|
calls into a single call. This is the most convinient method to initialise |
994 |
|
|
a watcher. The same limitations apply, of course. |
995 |
|
|
.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4 |
996 |
|
|
.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4 |
997 |
|
|
.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)" |
998 |
|
|
Starts (activates) the given watcher. Only active watchers will receive |
999 |
|
|
events. If the watcher is already active nothing will happen. |
1000 |
|
|
.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4 |
1001 |
|
|
.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4 |
1002 |
|
|
.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)" |
1003 |
|
|
Stops the given watcher again (if active) and clears the pending |
1004 |
|
|
status. It is possible that stopped watchers are pending (for example, |
1005 |
|
|
non-repeating timers are being stopped when they become pending), but |
1006 |
|
|
\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If |
1007 |
|
|
you want to free or reuse the memory used by the watcher it is therefore a |
1008 |
|
|
good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. |
1009 |
|
|
.IP "bool ev_is_active (ev_TYPE *watcher)" 4 |
1010 |
|
|
.IX Item "bool ev_is_active (ev_TYPE *watcher)" |
1011 |
|
|
Returns a true value iff the watcher is active (i.e. it has been started |
1012 |
|
|
and not yet been stopped). As long as a watcher is active you must not modify |
1013 |
|
|
it. |
1014 |
|
|
.IP "bool ev_is_pending (ev_TYPE *watcher)" 4 |
1015 |
|
|
.IX Item "bool ev_is_pending (ev_TYPE *watcher)" |
1016 |
|
|
Returns a true value iff the watcher is pending, (i.e. it has outstanding |
1017 |
|
|
events but its callback has not yet been invoked). As long as a watcher |
1018 |
|
|
is pending (but not active) you must not call an init function on it (but |
1019 |
|
|
\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must |
1020 |
|
|
make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR |
1021 |
|
|
it). |
1022 |
|
|
.IP "callback ev_cb (ev_TYPE *watcher)" 4 |
1023 |
|
|
.IX Item "callback ev_cb (ev_TYPE *watcher)" |
1024 |
|
|
Returns the callback currently set on the watcher. |
1025 |
|
|
.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 |
1026 |
|
|
.IX Item "ev_cb_set (ev_TYPE *watcher, callback)" |
1027 |
|
|
Change the callback. You can change the callback at virtually any time |
1028 |
|
|
(modulo threads). |
1029 |
|
|
.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4 |
1030 |
|
|
.IX Item "ev_set_priority (ev_TYPE *watcher, priority)" |
1031 |
|
|
.PD 0 |
1032 |
|
|
.IP "int ev_priority (ev_TYPE *watcher)" 4 |
1033 |
|
|
.IX Item "int ev_priority (ev_TYPE *watcher)" |
1034 |
|
|
.PD |
1035 |
|
|
Set and query the priority of the watcher. The priority is a small |
1036 |
|
|
integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR |
1037 |
|
|
(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked |
1038 |
|
|
before watchers with lower priority, but priority will not keep watchers |
1039 |
|
|
from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers). |
1040 |
|
|
.Sp |
1041 |
|
|
This means that priorities are \fIonly\fR used for ordering callback |
1042 |
|
|
invocation after new events have been received. This is useful, for |
1043 |
|
|
example, to reduce latency after idling, or more often, to bind two |
1044 |
|
|
watchers on the same event and make sure one is called first. |
1045 |
|
|
.Sp |
1046 |
|
|
If you need to suppress invocation when higher priority events are pending |
1047 |
|
|
you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality. |
1048 |
|
|
.Sp |
1049 |
|
|
You \fImust not\fR change the priority of a watcher as long as it is active or |
1050 |
|
|
pending. |
1051 |
|
|
.Sp |
1052 |
|
|
The default priority used by watchers when no priority has been set is |
1053 |
|
|
always \f(CW0\fR, which is supposed to not be too high and not be too low :). |
1054 |
|
|
.Sp |
1055 |
|
|
Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is |
1056 |
|
|
fine, as long as you do not mind that the priority value you query might |
1057 |
|
|
or might not have been adjusted to be within valid range. |
1058 |
|
|
.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4 |
1059 |
|
|
.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)" |
1060 |
|
|
Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither |
1061 |
|
|
\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback |
1062 |
|
|
can deal with that fact. |
1063 |
|
|
.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4 |
1064 |
|
|
.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)" |
1065 |
|
|
If the watcher is pending, this function returns clears its pending status |
1066 |
|
|
and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the |
1067 |
|
|
watcher isn't pending it does nothing and returns \f(CW0\fR. |
1068 |
|
|
.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" |
1069 |
|
|
.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" |
1070 |
|
|
Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change |
1071 |
|
|
and read at any time, libev will completely ignore it. This can be used |
1072 |
|
|
to associate arbitrary data with your watcher. If you need more data and |
1073 |
|
|
don't want to allocate memory and store a pointer to it in that data |
1074 |
|
|
member, you can also \*(L"subclass\*(R" the watcher type and provide your own |
1075 |
|
|
data: |
1076 |
|
|
.PP |
1077 |
|
|
.Vb 7 |
1078 |
|
|
\& struct my_io |
1079 |
|
|
\& { |
1080 |
|
|
\& struct ev_io io; |
1081 |
|
|
\& int otherfd; |
1082 |
|
|
\& void *somedata; |
1083 |
|
|
\& struct whatever *mostinteresting; |
1084 |
|
|
\& } |
1085 |
|
|
.Ve |
1086 |
|
|
.PP |
1087 |
|
|
And since your callback will be called with a pointer to the watcher, you |
1088 |
|
|
can cast it back to your own type: |
1089 |
|
|
.PP |
1090 |
|
|
.Vb 5 |
1091 |
|
|
\& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1092 |
|
|
\& { |
1093 |
|
|
\& struct my_io *w = (struct my_io *)w_; |
1094 |
|
|
\& ... |
1095 |
|
|
\& } |
1096 |
|
|
.Ve |
1097 |
|
|
.PP |
1098 |
|
|
More interesting and less C\-conformant ways of casting your callback type |
1099 |
|
|
instead have been omitted. |
1100 |
|
|
.PP |
1101 |
|
|
Another common scenario is having some data structure with multiple |
1102 |
|
|
watchers: |
1103 |
|
|
.PP |
1104 |
|
|
.Vb 6 |
1105 |
|
|
\& struct my_biggy |
1106 |
|
|
\& { |
1107 |
|
|
\& int some_data; |
1108 |
|
|
\& ev_timer t1; |
1109 |
|
|
\& ev_timer t2; |
1110 |
|
|
\& } |
1111 |
|
|
.Ve |
1112 |
|
|
.PP |
1113 |
|
|
In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated, |
1114 |
|
|
you need to use \f(CW\*(C`offsetof\*(C'\fR: |
1115 |
|
|
.PP |
1116 |
|
|
.Vb 1 |
1117 |
|
|
\& #include <stddef.h> |
1118 |
|
|
\& |
1119 |
|
|
\& static void |
1120 |
|
|
\& t1_cb (EV_P_ struct ev_timer *w, int revents) |
1121 |
|
|
\& { |
1122 |
|
|
\& struct my_biggy big = (struct my_biggy * |
1123 |
|
|
\& (((char *)w) \- offsetof (struct my_biggy, t1)); |
1124 |
|
|
\& } |
1125 |
|
|
\& |
1126 |
|
|
\& static void |
1127 |
|
|
\& t2_cb (EV_P_ struct ev_timer *w, int revents) |
1128 |
|
|
\& { |
1129 |
|
|
\& struct my_biggy big = (struct my_biggy * |
1130 |
|
|
\& (((char *)w) \- offsetof (struct my_biggy, t2)); |
1131 |
|
|
\& } |
1132 |
|
|
.Ve |
1133 |
|
|
.SH "WATCHER TYPES" |
1134 |
|
|
.IX Header "WATCHER TYPES" |
1135 |
|
|
This section describes each watcher in detail, but will not repeat |
1136 |
|
|
information given in the last section. Any initialisation/set macros, |
1137 |
|
|
functions and members specific to the watcher type are explained. |
1138 |
|
|
.PP |
1139 |
|
|
Members are additionally marked with either \fI[read\-only]\fR, meaning that, |
1140 |
|
|
while the watcher is active, you can look at the member and expect some |
1141 |
|
|
sensible content, but you must not modify it (you can modify it while the |
1142 |
|
|
watcher is stopped to your hearts content), or \fI[read\-write]\fR, which |
1143 |
|
|
means you can expect it to have some sensible content while the watcher |
1144 |
|
|
is active, but you can also modify it. Modifying it may not do something |
1145 |
|
|
sensible or take immediate effect (or do anything at all), but libev will |
1146 |
|
|
not crash or malfunction in any way. |
1147 |
|
|
.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?" |
1148 |
|
|
.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?" |
1149 |
|
|
.IX Subsection "ev_io - is this file descriptor readable or writable?" |
1150 |
|
|
I/O watchers check whether a file descriptor is readable or writable |
1151 |
|
|
in each iteration of the event loop, or, more precisely, when reading |
1152 |
|
|
would not block the process and writing would at least be able to write |
1153 |
|
|
some data. This behaviour is called level-triggering because you keep |
1154 |
|
|
receiving events as long as the condition persists. Remember you can stop |
1155 |
|
|
the watcher if you don't want to act on the event and neither want to |
1156 |
|
|
receive future events. |
1157 |
|
|
.PP |
1158 |
|
|
In general you can register as many read and/or write event watchers per |
1159 |
|
|
fd as you want (as long as you don't confuse yourself). Setting all file |
1160 |
|
|
descriptors to non-blocking mode is also usually a good idea (but not |
1161 |
|
|
required if you know what you are doing). |
1162 |
|
|
.PP |
1163 |
|
|
If you must do this, then force the use of a known-to-be-good backend |
1164 |
|
|
(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and |
1165 |
|
|
\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). |
1166 |
|
|
.PP |
1167 |
|
|
Another thing you have to watch out for is that it is quite easy to |
1168 |
|
|
receive \*(L"spurious\*(R" readyness notifications, that is your callback might |
1169 |
|
|
be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
1170 |
|
|
because there is no data. Not only are some backends known to create a |
1171 |
|
|
lot of those (for example solaris ports), it is very easy to get into |
1172 |
|
|
this situation even with a relatively standard program structure. Thus |
1173 |
|
|
it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning |
1174 |
|
|
\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. |
1175 |
|
|
.PP |
1176 |
|
|
If you cannot run the fd in non-blocking mode (for example you should not |
1177 |
|
|
play around with an Xlib connection), then you have to seperately re-test |
1178 |
|
|
whether a file descriptor is really ready with a known-to-be good interface |
1179 |
|
|
such as poll (fortunately in our Xlib example, Xlib already does this on |
1180 |
|
|
its own, so its quite safe to use). |
1181 |
|
|
.PP |
1182 |
|
|
\fIThe special problem of disappearing file descriptors\fR |
1183 |
|
|
.IX Subsection "The special problem of disappearing file descriptors" |
1184 |
|
|
.PP |
1185 |
|
|
Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1186 |
|
|
descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means, |
1187 |
|
|
such as \f(CW\*(C`dup\*(C'\fR). The reason is that you register interest in some file |
1188 |
|
|
descriptor, but when it goes away, the operating system will silently drop |
1189 |
|
|
this interest. If another file descriptor with the same number then is |
1190 |
|
|
registered with libev, there is no efficient way to see that this is, in |
1191 |
|
|
fact, a different file descriptor. |
1192 |
|
|
.PP |
1193 |
|
|
To avoid having to explicitly tell libev about such cases, libev follows |
1194 |
|
|
the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev |
1195 |
|
|
will assume that this is potentially a new file descriptor, otherwise |
1196 |
|
|
it is assumed that the file descriptor stays the same. That means that |
1197 |
|
|
you \fIhave\fR to call \f(CW\*(C`ev_io_set\*(C'\fR (or \f(CW\*(C`ev_io_init\*(C'\fR) when you change the |
1198 |
|
|
descriptor even if the file descriptor number itself did not change. |
1199 |
|
|
.PP |
1200 |
|
|
This is how one would do it normally anyway, the important point is that |
1201 |
|
|
the libev application should not optimise around libev but should leave |
1202 |
|
|
optimisations to libev. |
1203 |
|
|
.PP |
1204 |
|
|
\fIThe special problem of dup'ed file descriptors\fR |
1205 |
|
|
.IX Subsection "The special problem of dup'ed file descriptors" |
1206 |
|
|
.PP |
1207 |
|
|
Some backends (e.g. epoll), cannot register events for file descriptors, |
1208 |
|
|
but only events for the underlying file descriptions. That means when you |
1209 |
|
|
have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or weirder constellations, and register |
1210 |
|
|
events for them, only one file descriptor might actually receive events. |
1211 |
|
|
.PP |
1212 |
|
|
There is no workaround possible except not registering events |
1213 |
|
|
for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to |
1214 |
|
|
\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
1215 |
|
|
.PP |
1216 |
|
|
\fIThe special problem of fork\fR |
1217 |
|
|
.IX Subsection "The special problem of fork" |
1218 |
|
|
.PP |
1219 |
|
|
Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit |
1220 |
|
|
useless behaviour. Libev fully supports fork, but needs to be told about |
1221 |
|
|
it in the child. |
1222 |
|
|
.PP |
1223 |
|
|
To support fork in your programs, you either have to call |
1224 |
|
|
\&\f(CW\*(C`ev_default_fork ()\*(C'\fR or \f(CW\*(C`ev_loop_fork ()\*(C'\fR after a fork in the child, |
1225 |
|
|
enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or |
1226 |
|
|
\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
1227 |
|
|
.PP |
1228 |
|
|
\fIThe special problem of \s-1SIGPIPE\s0\fR |
1229 |
|
|
.IX Subsection "The special problem of SIGPIPE" |
1230 |
|
|
.PP |
1231 |
|
|
While not really specific to libev, it is easy to forget about \s-1SIGPIPE:\s0 |
1232 |
|
|
when reading from a pipe whose other end has been closed, your program |
1233 |
|
|
gets send a \s-1SIGPIPE\s0, which, by default, aborts your program. For most |
1234 |
|
|
programs this is sensible behaviour, for daemons, this is usually |
1235 |
|
|
undesirable. |
1236 |
|
|
.PP |
1237 |
|
|
So when you encounter spurious, unexplained daemon exits, make sure you |
1238 |
|
|
ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon |
1239 |
|
|
somewhere, as that would have given you a big clue). |
1240 |
|
|
.PP |
1241 |
|
|
\fIWatcher-Specific Functions\fR |
1242 |
|
|
.IX Subsection "Watcher-Specific Functions" |
1243 |
|
|
.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 |
1244 |
|
|
.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" |
1245 |
|
|
.PD 0 |
1246 |
|
|
.IP "ev_io_set (ev_io *, int fd, int events)" 4 |
1247 |
|
|
.IX Item "ev_io_set (ev_io *, int fd, int events)" |
1248 |
|
|
.PD |
1249 |
|
|
Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to |
1250 |
|
|
rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or |
1251 |
|
|
\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events. |
1252 |
|
|
.IP "int fd [read\-only]" 4 |
1253 |
|
|
.IX Item "int fd [read-only]" |
1254 |
|
|
The file descriptor being watched. |
1255 |
|
|
.IP "int events [read\-only]" 4 |
1256 |
|
|
.IX Item "int events [read-only]" |
1257 |
|
|
The events being watched. |
1258 |
|
|
.PP |
1259 |
|
|
\fIExamples\fR |
1260 |
|
|
.IX Subsection "Examples" |
1261 |
|
|
.PP |
1262 |
|
|
Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well |
1263 |
|
|
readable, but only once. Since it is likely line-buffered, you could |
1264 |
|
|
attempt to read a whole line in the callback. |
1265 |
|
|
.PP |
1266 |
|
|
.Vb 6 |
1267 |
|
|
\& static void |
1268 |
|
|
\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1269 |
|
|
\& { |
1270 |
|
|
\& ev_io_stop (loop, w); |
1271 |
|
|
\& .. read from stdin here (or from w\->fd) and haqndle any I/O errors |
1272 |
|
|
\& } |
1273 |
|
|
\& |
1274 |
|
|
\& ... |
1275 |
|
|
\& struct ev_loop *loop = ev_default_init (0); |
1276 |
|
|
\& struct ev_io stdin_readable; |
1277 |
|
|
\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1278 |
|
|
\& ev_io_start (loop, &stdin_readable); |
1279 |
|
|
\& ev_loop (loop, 0); |
1280 |
|
|
.Ve |
1281 |
|
|
.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts" |
1282 |
|
|
.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts" |
1283 |
|
|
.IX Subsection "ev_timer - relative and optionally repeating timeouts" |
1284 |
|
|
Timer watchers are simple relative timers that generate an event after a |
1285 |
|
|
given time, and optionally repeating in regular intervals after that. |
1286 |
|
|
.PP |
1287 |
|
|
The timers are based on real time, that is, if you register an event that |
1288 |
|
|
times out after an hour and you reset your system clock to last years |
1289 |
|
|
time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because |
1290 |
|
|
detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1291 |
|
|
monotonic clock option helps a lot here). |
1292 |
|
|
.PP |
1293 |
|
|
The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR |
1294 |
|
|
time. This is usually the right thing as this timestamp refers to the time |
1295 |
|
|
of the event triggering whatever timeout you are modifying/starting. If |
1296 |
|
|
you suspect event processing to be delayed and you \fIneed\fR to base the timeout |
1297 |
|
|
on the current time, use something like this to adjust for this: |
1298 |
|
|
.PP |
1299 |
|
|
.Vb 1 |
1300 |
|
|
\& ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.); |
1301 |
|
|
.Ve |
1302 |
|
|
.PP |
1303 |
|
|
The callback is guarenteed to be invoked only when its timeout has passed, |
1304 |
|
|
but if multiple timers become ready during the same loop iteration then |
1305 |
|
|
order of execution is undefined. |
1306 |
|
|
.PP |
1307 |
|
|
\fIWatcher-Specific Functions and Data Members\fR |
1308 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
1309 |
|
|
.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 |
1310 |
|
|
.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" |
1311 |
|
|
.PD 0 |
1312 |
|
|
.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 |
1313 |
|
|
.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" |
1314 |
|
|
.PD |
1315 |
|
|
Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR is |
1316 |
|
|
\&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the |
1317 |
|
|
timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds |
1318 |
|
|
later, again, and again, until stopped manually. |
1319 |
|
|
.Sp |
1320 |
|
|
The timer itself will do a best-effort at avoiding drift, that is, if you |
1321 |
|
|
configure a timer to trigger every 10 seconds, then it will trigger at |
1322 |
|
|
exactly 10 second intervals. If, however, your program cannot keep up with |
1323 |
|
|
the timer (because it takes longer than those 10 seconds to do stuff) the |
1324 |
|
|
timer will not fire more than once per event loop iteration. |
1325 |
|
|
.IP "ev_timer_again (loop, ev_timer *)" 4 |
1326 |
|
|
.IX Item "ev_timer_again (loop, ev_timer *)" |
1327 |
|
|
This will act as if the timer timed out and restart it again if it is |
1328 |
|
|
repeating. The exact semantics are: |
1329 |
|
|
.Sp |
1330 |
|
|
If the timer is pending, its pending status is cleared. |
1331 |
|
|
.Sp |
1332 |
|
|
If the timer is started but nonrepeating, stop it (as if it timed out). |
1333 |
|
|
.Sp |
1334 |
|
|
If the timer is repeating, either start it if necessary (with the |
1335 |
|
|
\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value. |
1336 |
|
|
.Sp |
1337 |
|
|
This sounds a bit complicated, but here is a useful and typical |
1338 |
|
|
example: Imagine you have a tcp connection and you want a so-called idle |
1339 |
|
|
timeout, that is, you want to be called when there have been, say, 60 |
1340 |
|
|
seconds of inactivity on the socket. The easiest way to do this is to |
1341 |
|
|
configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call |
1342 |
|
|
\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If |
1343 |
|
|
you go into an idle state where you do not expect data to travel on the |
1344 |
|
|
socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will |
1345 |
|
|
automatically restart it if need be. |
1346 |
|
|
.Sp |
1347 |
|
|
That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR |
1348 |
|
|
altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR: |
1349 |
|
|
.Sp |
1350 |
|
|
.Vb 8 |
1351 |
|
|
\& ev_timer_init (timer, callback, 0., 5.); |
1352 |
|
|
\& ev_timer_again (loop, timer); |
1353 |
|
|
\& ... |
1354 |
|
|
\& timer\->again = 17.; |
1355 |
|
|
\& ev_timer_again (loop, timer); |
1356 |
|
|
\& ... |
1357 |
|
|
\& timer\->again = 10.; |
1358 |
|
|
\& ev_timer_again (loop, timer); |
1359 |
|
|
.Ve |
1360 |
|
|
.Sp |
1361 |
|
|
This is more slightly efficient then stopping/starting the timer each time |
1362 |
|
|
you want to modify its timeout value. |
1363 |
|
|
.IP "ev_tstamp repeat [read\-write]" 4 |
1364 |
|
|
.IX Item "ev_tstamp repeat [read-write]" |
1365 |
|
|
The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out |
1366 |
|
|
or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any), |
1367 |
|
|
which is also when any modifications are taken into account. |
1368 |
|
|
.PP |
1369 |
|
|
\fIExamples\fR |
1370 |
|
|
.IX Subsection "Examples" |
1371 |
|
|
.PP |
1372 |
|
|
Example: Create a timer that fires after 60 seconds. |
1373 |
|
|
.PP |
1374 |
|
|
.Vb 5 |
1375 |
|
|
\& static void |
1376 |
|
|
\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1377 |
|
|
\& { |
1378 |
|
|
\& .. one minute over, w is actually stopped right here |
1379 |
|
|
\& } |
1380 |
|
|
\& |
1381 |
|
|
\& struct ev_timer mytimer; |
1382 |
|
|
\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1383 |
|
|
\& ev_timer_start (loop, &mytimer); |
1384 |
|
|
.Ve |
1385 |
|
|
.PP |
1386 |
|
|
Example: Create a timeout timer that times out after 10 seconds of |
1387 |
|
|
inactivity. |
1388 |
|
|
.PP |
1389 |
|
|
.Vb 5 |
1390 |
|
|
\& static void |
1391 |
|
|
\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1392 |
|
|
\& { |
1393 |
|
|
\& .. ten seconds without any activity |
1394 |
|
|
\& } |
1395 |
|
|
\& |
1396 |
|
|
\& struct ev_timer mytimer; |
1397 |
|
|
\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1398 |
|
|
\& ev_timer_again (&mytimer); /* start timer */ |
1399 |
|
|
\& ev_loop (loop, 0); |
1400 |
|
|
\& |
1401 |
|
|
\& // and in some piece of code that gets executed on any "activity": |
1402 |
|
|
\& // reset the timeout to start ticking again at 10 seconds |
1403 |
|
|
\& ev_timer_again (&mytimer); |
1404 |
|
|
.Ve |
1405 |
|
|
.ie n .Sh """ev_periodic"" \- to cron or not to cron?" |
1406 |
|
|
.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?" |
1407 |
|
|
.IX Subsection "ev_periodic - to cron or not to cron?" |
1408 |
|
|
Periodic watchers are also timers of a kind, but they are very versatile |
1409 |
|
|
(and unfortunately a bit complex). |
1410 |
|
|
.PP |
1411 |
|
|
Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) |
1412 |
|
|
but on wallclock time (absolute time). You can tell a periodic watcher |
1413 |
|
|
to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a |
1414 |
|
|
periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now () |
1415 |
|
|
+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will |
1416 |
|
|
take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger |
1417 |
|
|
roughly 10 seconds later). |
1418 |
|
|
.PP |
1419 |
|
|
They can also be used to implement vastly more complex timers, such as |
1420 |
|
|
triggering an event on each midnight, local time or other, complicated, |
1421 |
|
|
rules. |
1422 |
|
|
.PP |
1423 |
|
|
As with timers, the callback is guarenteed to be invoked only when the |
1424 |
|
|
time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready |
1425 |
|
|
during the same loop iteration then order of execution is undefined. |
1426 |
|
|
.PP |
1427 |
|
|
\fIWatcher-Specific Functions and Data Members\fR |
1428 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
1429 |
|
|
.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 |
1430 |
|
|
.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" |
1431 |
|
|
.PD 0 |
1432 |
|
|
.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 |
1433 |
|
|
.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" |
1434 |
|
|
.PD |
1435 |
|
|
Lots of arguments, lets sort it out... There are basically three modes of |
1436 |
|
|
operation, and we will explain them from simplest to complex: |
1437 |
|
|
.RS 4 |
1438 |
|
|
.IP "\(bu" 4 |
1439 |
|
|
absolute timer (at = time, interval = reschedule_cb = 0) |
1440 |
|
|
.Sp |
1441 |
|
|
In this configuration the watcher triggers an event at the wallclock time |
1442 |
|
|
\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, |
1443 |
|
|
that is, if it is to be run at January 1st 2011 then it will run when the |
1444 |
|
|
system time reaches or surpasses this time. |
1445 |
|
|
.IP "\(bu" 4 |
1446 |
|
|
repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1447 |
|
|
.Sp |
1448 |
|
|
In this mode the watcher will always be scheduled to time out at the next |
1449 |
|
|
\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative) |
1450 |
|
|
and then repeat, regardless of any time jumps. |
1451 |
|
|
.Sp |
1452 |
|
|
This can be used to create timers that do not drift with respect to system |
1453 |
|
|
time: |
1454 |
|
|
.Sp |
1455 |
|
|
.Vb 1 |
1456 |
|
|
\& ev_periodic_set (&periodic, 0., 3600., 0); |
1457 |
|
|
.Ve |
1458 |
|
|
.Sp |
1459 |
|
|
This doesn't mean there will always be 3600 seconds in between triggers, |
1460 |
|
|
but only that the the callback will be called when the system time shows a |
1461 |
|
|
full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible |
1462 |
|
|
by 3600. |
1463 |
|
|
.Sp |
1464 |
|
|
Another way to think about it (for the mathematically inclined) is that |
1465 |
|
|
\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
1466 |
|
|
time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. |
1467 |
|
|
.Sp |
1468 |
|
|
For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near |
1469 |
|
|
\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for |
1470 |
|
|
this value. |
1471 |
|
|
.IP "\(bu" 4 |
1472 |
|
|
manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1473 |
|
|
.Sp |
1474 |
|
|
In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being |
1475 |
|
|
ignored. Instead, each time the periodic watcher gets scheduled, the |
1476 |
|
|
reschedule callback will be called with the watcher as first, and the |
1477 |
|
|
current time as second argument. |
1478 |
|
|
.Sp |
1479 |
|
|
\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, |
1480 |
|
|
ever, or make any event loop modifications\fR. If you need to stop it, |
1481 |
|
|
return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by |
1482 |
|
|
starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal). |
1483 |
|
|
.Sp |
1484 |
|
|
Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1485 |
|
|
ev_tstamp now)\*(C'\fR, e.g.: |
1486 |
|
|
.Sp |
1487 |
|
|
.Vb 4 |
1488 |
|
|
\& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1489 |
|
|
\& { |
1490 |
|
|
\& return now + 60.; |
1491 |
|
|
\& } |
1492 |
|
|
.Ve |
1493 |
|
|
.Sp |
1494 |
|
|
It must return the next time to trigger, based on the passed time value |
1495 |
|
|
(that is, the lowest time value larger than to the second argument). It |
1496 |
|
|
will usually be called just before the callback will be triggered, but |
1497 |
|
|
might be called at other times, too. |
1498 |
|
|
.Sp |
1499 |
|
|
\&\s-1NOTE:\s0 \fIThis callback must always return a time that is later than the |
1500 |
|
|
passed \f(CI\*(C`now\*(C'\fI value\fR. Not even \f(CW\*(C`now\*(C'\fR itself will do, it \fImust\fR be larger. |
1501 |
|
|
.Sp |
1502 |
|
|
This can be used to create very complex timers, such as a timer that |
1503 |
|
|
triggers on each midnight, local time. To do this, you would calculate the |
1504 |
|
|
next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How |
1505 |
|
|
you do this is, again, up to you (but it is not trivial, which is the main |
1506 |
|
|
reason I omitted it as an example). |
1507 |
|
|
.RE |
1508 |
|
|
.RS 4 |
1509 |
|
|
.RE |
1510 |
|
|
.IP "ev_periodic_again (loop, ev_periodic *)" 4 |
1511 |
|
|
.IX Item "ev_periodic_again (loop, ev_periodic *)" |
1512 |
|
|
Simply stops and restarts the periodic watcher again. This is only useful |
1513 |
|
|
when you changed some parameters or the reschedule callback would return |
1514 |
|
|
a different time than the last time it was called (e.g. in a crond like |
1515 |
|
|
program when the crontabs have changed). |
1516 |
|
|
.IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4 |
1517 |
|
|
.IX Item "ev_tstamp ev_periodic_at (ev_periodic *)" |
1518 |
|
|
When active, returns the absolute time that the watcher is supposed to |
1519 |
|
|
trigger next. |
1520 |
|
|
.IP "ev_tstamp offset [read\-write]" 4 |
1521 |
|
|
.IX Item "ev_tstamp offset [read-write]" |
1522 |
|
|
When repeating, this contains the offset value, otherwise this is the |
1523 |
|
|
absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR). |
1524 |
|
|
.Sp |
1525 |
|
|
Can be modified any time, but changes only take effect when the periodic |
1526 |
|
|
timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
1527 |
|
|
.IP "ev_tstamp interval [read\-write]" 4 |
1528 |
|
|
.IX Item "ev_tstamp interval [read-write]" |
1529 |
|
|
The current interval value. Can be modified any time, but changes only |
1530 |
|
|
take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being |
1531 |
|
|
called. |
1532 |
|
|
.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4 |
1533 |
|
|
.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]" |
1534 |
|
|
The current reschedule callback, or \f(CW0\fR, if this functionality is |
1535 |
|
|
switched off. Can be changed any time, but changes only take effect when |
1536 |
|
|
the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
1537 |
|
|
.PP |
1538 |
|
|
\fIExamples\fR |
1539 |
|
|
.IX Subsection "Examples" |
1540 |
|
|
.PP |
1541 |
|
|
Example: Call a callback every hour, or, more precisely, whenever the |
1542 |
|
|
system clock is divisible by 3600. The callback invocation times have |
1543 |
|
|
potentially a lot of jittering, but good long-term stability. |
1544 |
|
|
.PP |
1545 |
|
|
.Vb 5 |
1546 |
|
|
\& static void |
1547 |
|
|
\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1548 |
|
|
\& { |
1549 |
|
|
\& ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1550 |
|
|
\& } |
1551 |
|
|
\& |
1552 |
|
|
\& struct ev_periodic hourly_tick; |
1553 |
|
|
\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1554 |
|
|
\& ev_periodic_start (loop, &hourly_tick); |
1555 |
|
|
.Ve |
1556 |
|
|
.PP |
1557 |
|
|
Example: The same as above, but use a reschedule callback to do it: |
1558 |
|
|
.PP |
1559 |
|
|
.Vb 1 |
1560 |
|
|
\& #include <math.h> |
1561 |
|
|
\& |
1562 |
|
|
\& static ev_tstamp |
1563 |
|
|
\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1564 |
|
|
\& { |
1565 |
|
|
\& return fmod (now, 3600.) + 3600.; |
1566 |
|
|
\& } |
1567 |
|
|
\& |
1568 |
|
|
\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1569 |
|
|
.Ve |
1570 |
|
|
.PP |
1571 |
|
|
Example: Call a callback every hour, starting now: |
1572 |
|
|
.PP |
1573 |
|
|
.Vb 4 |
1574 |
|
|
\& struct ev_periodic hourly_tick; |
1575 |
|
|
\& ev_periodic_init (&hourly_tick, clock_cb, |
1576 |
|
|
\& fmod (ev_now (loop), 3600.), 3600., 0); |
1577 |
|
|
\& ev_periodic_start (loop, &hourly_tick); |
1578 |
|
|
.Ve |
1579 |
|
|
.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!" |
1580 |
|
|
.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!" |
1581 |
|
|
.IX Subsection "ev_signal - signal me when a signal gets signalled!" |
1582 |
|
|
Signal watchers will trigger an event when the process receives a specific |
1583 |
|
|
signal one or more times. Even though signals are very asynchronous, libev |
1584 |
|
|
will try it's best to deliver signals synchronously, i.e. as part of the |
1585 |
|
|
normal event processing, like any other event. |
1586 |
|
|
.PP |
1587 |
|
|
You can configure as many watchers as you like per signal. Only when the |
1588 |
|
|
first watcher gets started will libev actually register a signal watcher |
1589 |
|
|
with the kernel (thus it coexists with your own signal handlers as long |
1590 |
|
|
as you don't register any with libev). Similarly, when the last signal |
1591 |
|
|
watcher for a signal is stopped libev will reset the signal handler to |
1592 |
|
|
\&\s-1SIG_DFL\s0 (regardless of what it was set to before). |
1593 |
|
|
.PP |
1594 |
|
|
If possible and supported, libev will install its handlers with |
1595 |
|
|
\&\f(CW\*(C`SA_RESTART\*(C'\fR behaviour enabled, so syscalls should not be unduly |
1596 |
|
|
interrupted. If you have a problem with syscalls getting interrupted by |
1597 |
|
|
signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher and unblock |
1598 |
|
|
them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher. |
1599 |
|
|
.PP |
1600 |
|
|
\fIWatcher-Specific Functions and Data Members\fR |
1601 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
1602 |
|
|
.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 |
1603 |
|
|
.IX Item "ev_signal_init (ev_signal *, callback, int signum)" |
1604 |
|
|
.PD 0 |
1605 |
|
|
.IP "ev_signal_set (ev_signal *, int signum)" 4 |
1606 |
|
|
.IX Item "ev_signal_set (ev_signal *, int signum)" |
1607 |
|
|
.PD |
1608 |
|
|
Configures the watcher to trigger on the given signal number (usually one |
1609 |
|
|
of the \f(CW\*(C`SIGxxx\*(C'\fR constants). |
1610 |
|
|
.IP "int signum [read\-only]" 4 |
1611 |
|
|
.IX Item "int signum [read-only]" |
1612 |
|
|
The signal the watcher watches out for. |
1613 |
|
|
.PP |
1614 |
|
|
\fIExamples\fR |
1615 |
|
|
.IX Subsection "Examples" |
1616 |
|
|
.PP |
1617 |
|
|
Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. |
1618 |
|
|
.PP |
1619 |
|
|
.Vb 5 |
1620 |
|
|
\& static void |
1621 |
|
|
\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1622 |
|
|
\& { |
1623 |
|
|
\& ev_unloop (loop, EVUNLOOP_ALL); |
1624 |
|
|
\& } |
1625 |
|
|
\& |
1626 |
|
|
\& struct ev_signal signal_watcher; |
1627 |
|
|
\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1628 |
|
|
\& ev_signal_start (loop, &sigint_cb); |
1629 |
|
|
.Ve |
1630 |
|
|
.ie n .Sh """ev_child"" \- watch out for process status changes" |
1631 |
|
|
.el .Sh "\f(CWev_child\fP \- watch out for process status changes" |
1632 |
|
|
.IX Subsection "ev_child - watch out for process status changes" |
1633 |
|
|
Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
1634 |
|
|
some child status changes (most typically when a child of yours dies). It |
1635 |
|
|
is permissible to install a child watcher \fIafter\fR the child has been |
1636 |
|
|
forked (which implies it might have already exited), as long as the event |
1637 |
|
|
loop isn't entered (or is continued from a watcher). |
1638 |
|
|
.PP |
1639 |
|
|
Only the default event loop is capable of handling signals, and therefore |
1640 |
|
|
you can only rgeister child watchers in the default event loop. |
1641 |
|
|
.PP |
1642 |
|
|
\fIProcess Interaction\fR |
1643 |
|
|
.IX Subsection "Process Interaction" |
1644 |
|
|
.PP |
1645 |
|
|
Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is |
1646 |
|
|
initialised. This is necessary to guarantee proper behaviour even if |
1647 |
|
|
the first child watcher is started after the child exits. The occurance |
1648 |
|
|
of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done |
1649 |
|
|
synchronously as part of the event loop processing. Libev always reaps all |
1650 |
|
|
children, even ones not watched. |
1651 |
|
|
.PP |
1652 |
|
|
\fIOverriding the Built-In Processing\fR |
1653 |
|
|
.IX Subsection "Overriding the Built-In Processing" |
1654 |
|
|
.PP |
1655 |
|
|
Libev offers no special support for overriding the built-in child |
1656 |
|
|
processing, but if your application collides with libev's default child |
1657 |
|
|
handler, you can override it easily by installing your own handler for |
1658 |
|
|
\&\f(CW\*(C`SIGCHLD\*(C'\fR after initialising the default loop, and making sure the |
1659 |
|
|
default loop never gets destroyed. You are encouraged, however, to use an |
1660 |
|
|
event-based approach to child reaping and thus use libev's support for |
1661 |
|
|
that, so other libev users can use \f(CW\*(C`ev_child\*(C'\fR watchers freely. |
1662 |
|
|
.PP |
1663 |
|
|
\fIWatcher-Specific Functions and Data Members\fR |
1664 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
1665 |
|
|
.IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4 |
1666 |
|
|
.IX Item "ev_child_init (ev_child *, callback, int pid, int trace)" |
1667 |
|
|
.PD 0 |
1668 |
|
|
.IP "ev_child_set (ev_child *, int pid, int trace)" 4 |
1669 |
|
|
.IX Item "ev_child_set (ev_child *, int pid, int trace)" |
1670 |
|
|
.PD |
1671 |
|
|
Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or |
1672 |
|
|
\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look |
1673 |
|
|
at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see |
1674 |
|
|
the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems |
1675 |
|
|
\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the |
1676 |
|
|
process causing the status change. \f(CW\*(C`trace\*(C'\fR must be either \f(CW0\fR (only |
1677 |
|
|
activate the watcher when the process terminates) or \f(CW1\fR (additionally |
1678 |
|
|
activate the watcher when the process is stopped or continued). |
1679 |
|
|
.IP "int pid [read\-only]" 4 |
1680 |
|
|
.IX Item "int pid [read-only]" |
1681 |
|
|
The process id this watcher watches out for, or \f(CW0\fR, meaning any process id. |
1682 |
|
|
.IP "int rpid [read\-write]" 4 |
1683 |
|
|
.IX Item "int rpid [read-write]" |
1684 |
|
|
The process id that detected a status change. |
1685 |
|
|
.IP "int rstatus [read\-write]" 4 |
1686 |
|
|
.IX Item "int rstatus [read-write]" |
1687 |
|
|
The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems |
1688 |
|
|
\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details). |
1689 |
|
|
.PP |
1690 |
|
|
\fIExamples\fR |
1691 |
|
|
.IX Subsection "Examples" |
1692 |
|
|
.PP |
1693 |
|
|
Example: \f(CW\*(C`fork()\*(C'\fR a new process and install a child handler to wait for |
1694 |
|
|
its completion. |
1695 |
|
|
.PP |
1696 |
|
|
.Vb 1 |
1697 |
|
|
\& ev_child cw; |
1698 |
|
|
\& |
1699 |
|
|
\& static void |
1700 |
|
|
\& child_cb (EV_P_ struct ev_child *w, int revents) |
1701 |
|
|
\& { |
1702 |
|
|
\& ev_child_stop (EV_A_ w); |
1703 |
|
|
\& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus); |
1704 |
|
|
\& } |
1705 |
|
|
\& |
1706 |
|
|
\& pid_t pid = fork (); |
1707 |
|
|
\& |
1708 |
|
|
\& if (pid < 0) |
1709 |
|
|
\& // error |
1710 |
|
|
\& else if (pid == 0) |
1711 |
|
|
\& { |
1712 |
|
|
\& // the forked child executes here |
1713 |
|
|
\& exit (1); |
1714 |
|
|
\& } |
1715 |
|
|
\& else |
1716 |
|
|
\& { |
1717 |
|
|
\& ev_child_init (&cw, child_cb, pid, 0); |
1718 |
|
|
\& ev_child_start (EV_DEFAULT_ &cw); |
1719 |
|
|
\& } |
1720 |
|
|
.Ve |
1721 |
|
|
.ie n .Sh """ev_stat"" \- did the file attributes just change?" |
1722 |
|
|
.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?" |
1723 |
|
|
.IX Subsection "ev_stat - did the file attributes just change?" |
1724 |
|
|
This watches a filesystem path for attribute changes. That is, it calls |
1725 |
|
|
\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed |
1726 |
|
|
compared to the last time, invoking the callback if it did. |
1727 |
|
|
.PP |
1728 |
|
|
The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does |
1729 |
|
|
not exist\*(R" is a status change like any other. The condition \*(L"path does |
1730 |
|
|
not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is |
1731 |
|
|
otherwise always forced to be at least one) and all the other fields of |
1732 |
|
|
the stat buffer having unspecified contents. |
1733 |
|
|
.PP |
1734 |
|
|
The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is |
1735 |
|
|
relative and your working directory changes, the behaviour is undefined. |
1736 |
|
|
.PP |
1737 |
|
|
Since there is no standard to do this, the portable implementation simply |
1738 |
|
|
calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You |
1739 |
|
|
can specify a recommended polling interval for this case. If you specify |
1740 |
|
|
a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable, |
1741 |
|
|
unspecified default\fR value will be used (which you can expect to be around |
1742 |
|
|
five seconds, although this might change dynamically). Libev will also |
1743 |
|
|
impose a minimum interval which is currently around \f(CW0.1\fR, but thats |
1744 |
|
|
usually overkill. |
1745 |
|
|
.PP |
1746 |
|
|
This watcher type is not meant for massive numbers of stat watchers, |
1747 |
|
|
as even with OS-supported change notifications, this can be |
1748 |
|
|
resource-intensive. |
1749 |
|
|
.PP |
1750 |
|
|
At the time of this writing, only the Linux inotify interface is |
1751 |
|
|
implemented (implementing kqueue support is left as an exercise for the |
1752 |
|
|
reader, note, however, that the author sees no way of implementing ev_stat |
1753 |
|
|
semantics with kqueue). Inotify will be used to give hints only and should |
1754 |
|
|
not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev |
1755 |
|
|
sometimes needs to fall back to regular polling again even with inotify, |
1756 |
|
|
but changes are usually detected immediately, and if the file exists there |
1757 |
|
|
will be no polling. |
1758 |
|
|
.PP |
1759 |
|
|
\fI\s-1ABI\s0 Issues (Largefile Support)\fR |
1760 |
|
|
.IX Subsection "ABI Issues (Largefile Support)" |
1761 |
|
|
.PP |
1762 |
|
|
Libev by default (unless the user overrides this) uses the default |
1763 |
|
|
compilation environment, which means that on systems with optionally |
1764 |
|
|
disabled large file support, you get the 32 bit version of the stat |
1765 |
|
|
structure. When using the library from programs that change the \s-1ABI\s0 to |
1766 |
|
|
use 64 bit file offsets the programs will fail. In that case you have to |
1767 |
|
|
compile libev with the same flags to get binary compatibility. This is |
1768 |
|
|
obviously the case with any flags that change the \s-1ABI\s0, but the problem is |
1769 |
|
|
most noticably with ev_stat and largefile support. |
1770 |
|
|
.PP |
1771 |
|
|
\fIInotify\fR |
1772 |
|
|
.IX Subsection "Inotify" |
1773 |
|
|
.PP |
1774 |
|
|
When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev (generally only |
1775 |
|
|
available on Linux) and present at runtime, it will be used to speed up |
1776 |
|
|
change detection where possible. The inotify descriptor will be created lazily |
1777 |
|
|
when the first \f(CW\*(C`ev_stat\*(C'\fR watcher is being started. |
1778 |
|
|
.PP |
1779 |
|
|
Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers |
1780 |
|
|
except that changes might be detected earlier, and in some cases, to avoid |
1781 |
|
|
making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support |
1782 |
|
|
there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling. |
1783 |
|
|
.PP |
1784 |
|
|
(There is no support for kqueue, as apparently it cannot be used to |
1785 |
|
|
implement this functionality, due to the requirement of having a file |
1786 |
|
|
descriptor open on the object at all times). |
1787 |
|
|
.PP |
1788 |
|
|
\fIThe special problem of stat time resolution\fR |
1789 |
|
|
.IX Subsection "The special problem of stat time resolution" |
1790 |
|
|
.PP |
1791 |
|
|
The \f(CW\*(C`stat ()\*(C'\fR syscall only supports full-second resolution portably, and |
1792 |
|
|
even on systems where the resolution is higher, many filesystems still |
1793 |
|
|
only support whole seconds. |
1794 |
|
|
.PP |
1795 |
|
|
That means that, if the time is the only thing that changes, you can |
1796 |
|
|
easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and |
1797 |
|
|
calls your callback, which does something. When there is another update |
1798 |
|
|
within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect it as the stat |
1799 |
|
|
data does not change. |
1800 |
|
|
.PP |
1801 |
|
|
The solution to this is to delay acting on a change for slightly more |
1802 |
|
|
than second (or till slightly after the next full second boundary), using |
1803 |
|
|
a roughly one-second-delay \f(CW\*(C`ev_timer\*(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02); |
1804 |
|
|
ev_timer_again (loop, w)\*(C'\fR). |
1805 |
|
|
.PP |
1806 |
|
|
The \f(CW.02\fR offset is added to work around small timing inconsistencies |
1807 |
|
|
of some operating systems (where the second counter of the current time |
1808 |
|
|
might be be delayed. One such system is the Linux kernel, where a call to |
1809 |
|
|
\&\f(CW\*(C`gettimeofday\*(C'\fR might return a timestamp with a full second later than |
1810 |
|
|
a subsequent \f(CW\*(C`time\*(C'\fR call \- if the equivalent of \f(CW\*(C`time ()\*(C'\fR is used to |
1811 |
|
|
update file times then there will be a small window where the kernel uses |
1812 |
|
|
the previous second to update file times but libev might already execute |
1813 |
|
|
the timer callback). |
1814 |
|
|
.PP |
1815 |
|
|
\fIWatcher-Specific Functions and Data Members\fR |
1816 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
1817 |
|
|
.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4 |
1818 |
|
|
.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" |
1819 |
|
|
.PD 0 |
1820 |
|
|
.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4 |
1821 |
|
|
.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" |
1822 |
|
|
.PD |
1823 |
|
|
Configures the watcher to wait for status changes of the given |
1824 |
|
|
\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to |
1825 |
|
|
be detected and should normally be specified as \f(CW0\fR to let libev choose |
1826 |
|
|
a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same |
1827 |
|
|
path for as long as the watcher is active. |
1828 |
|
|
.Sp |
1829 |
|
|
The callback will receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected, relative |
1830 |
|
|
to the attributes at the time the watcher was started (or the last change |
1831 |
|
|
was detected). |
1832 |
|
|
.IP "ev_stat_stat (loop, ev_stat *)" 4 |
1833 |
|
|
.IX Item "ev_stat_stat (loop, ev_stat *)" |
1834 |
|
|
Updates the stat buffer immediately with new values. If you change the |
1835 |
|
|
watched path in your callback, you could call this function to avoid |
1836 |
|
|
detecting this change (while introducing a race condition if you are not |
1837 |
|
|
the only one changing the path). Can also be useful simply to find out the |
1838 |
|
|
new values. |
1839 |
|
|
.IP "ev_statdata attr [read\-only]" 4 |
1840 |
|
|
.IX Item "ev_statdata attr [read-only]" |
1841 |
|
|
The most-recently detected attributes of the file. Although the type is |
1842 |
|
|
\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types |
1843 |
|
|
suitable for your system, but you can only rely on the POSIX-standardised |
1844 |
|
|
members to be present. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there was |
1845 |
|
|
some error while \f(CW\*(C`stat\*(C'\fRing the file. |
1846 |
|
|
.IP "ev_statdata prev [read\-only]" 4 |
1847 |
|
|
.IX Item "ev_statdata prev [read-only]" |
1848 |
|
|
The previous attributes of the file. The callback gets invoked whenever |
1849 |
|
|
\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR, or, more precisely, one or more of these members |
1850 |
|
|
differ: \f(CW\*(C`st_dev\*(C'\fR, \f(CW\*(C`st_ino\*(C'\fR, \f(CW\*(C`st_mode\*(C'\fR, \f(CW\*(C`st_nlink\*(C'\fR, \f(CW\*(C`st_uid\*(C'\fR, |
1851 |
|
|
\&\f(CW\*(C`st_gid\*(C'\fR, \f(CW\*(C`st_rdev\*(C'\fR, \f(CW\*(C`st_size\*(C'\fR, \f(CW\*(C`st_atime\*(C'\fR, \f(CW\*(C`st_mtime\*(C'\fR, \f(CW\*(C`st_ctime\*(C'\fR. |
1852 |
|
|
.IP "ev_tstamp interval [read\-only]" 4 |
1853 |
|
|
.IX Item "ev_tstamp interval [read-only]" |
1854 |
|
|
The specified interval. |
1855 |
|
|
.IP "const char *path [read\-only]" 4 |
1856 |
|
|
.IX Item "const char *path [read-only]" |
1857 |
|
|
The filesystem path that is being watched. |
1858 |
|
|
.PP |
1859 |
|
|
\fIExamples\fR |
1860 |
|
|
.IX Subsection "Examples" |
1861 |
|
|
.PP |
1862 |
|
|
Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes. |
1863 |
|
|
.PP |
1864 |
|
|
.Vb 10 |
1865 |
|
|
\& static void |
1866 |
|
|
\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
1867 |
|
|
\& { |
1868 |
|
|
\& /* /etc/passwd changed in some way */ |
1869 |
|
|
\& if (w\->attr.st_nlink) |
1870 |
|
|
\& { |
1871 |
|
|
\& printf ("passwd current size %ld\en", (long)w\->attr.st_size); |
1872 |
|
|
\& printf ("passwd current atime %ld\en", (long)w\->attr.st_mtime); |
1873 |
|
|
\& printf ("passwd current mtime %ld\en", (long)w\->attr.st_mtime); |
1874 |
|
|
\& } |
1875 |
|
|
\& else |
1876 |
|
|
\& /* you shalt not abuse printf for puts */ |
1877 |
|
|
\& puts ("wow, /etc/passwd is not there, expect problems. " |
1878 |
|
|
\& "if this is windows, they already arrived\en"); |
1879 |
|
|
\& } |
1880 |
|
|
\& |
1881 |
|
|
\& ... |
1882 |
|
|
\& ev_stat passwd; |
1883 |
|
|
\& |
1884 |
|
|
\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
1885 |
|
|
\& ev_stat_start (loop, &passwd); |
1886 |
|
|
.Ve |
1887 |
|
|
.PP |
1888 |
|
|
Example: Like above, but additionally use a one-second delay so we do not |
1889 |
|
|
miss updates (however, frequent updates will delay processing, too, so |
1890 |
|
|
one might do the work both on \f(CW\*(C`ev_stat\*(C'\fR callback invocation \fIand\fR on |
1891 |
|
|
\&\f(CW\*(C`ev_timer\*(C'\fR callback invocation). |
1892 |
|
|
.PP |
1893 |
|
|
.Vb 2 |
1894 |
|
|
\& static ev_stat passwd; |
1895 |
|
|
\& static ev_timer timer; |
1896 |
|
|
\& |
1897 |
|
|
\& static void |
1898 |
|
|
\& timer_cb (EV_P_ ev_timer *w, int revents) |
1899 |
|
|
\& { |
1900 |
|
|
\& ev_timer_stop (EV_A_ w); |
1901 |
|
|
\& |
1902 |
|
|
\& /* now it\*(Aqs one second after the most recent passwd change */ |
1903 |
|
|
\& } |
1904 |
|
|
\& |
1905 |
|
|
\& static void |
1906 |
|
|
\& stat_cb (EV_P_ ev_stat *w, int revents) |
1907 |
|
|
\& { |
1908 |
|
|
\& /* reset the one\-second timer */ |
1909 |
|
|
\& ev_timer_again (EV_A_ &timer); |
1910 |
|
|
\& } |
1911 |
|
|
\& |
1912 |
|
|
\& ... |
1913 |
|
|
\& ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1914 |
|
|
\& ev_stat_start (loop, &passwd); |
1915 |
|
|
\& ev_timer_init (&timer, timer_cb, 0., 1.02); |
1916 |
|
|
.Ve |
1917 |
|
|
.ie n .Sh """ev_idle"" \- when you've got nothing better to do..." |
1918 |
|
|
.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..." |
1919 |
|
|
.IX Subsection "ev_idle - when you've got nothing better to do..." |
1920 |
|
|
Idle watchers trigger events when no other events of the same or higher |
1921 |
|
|
priority are pending (prepare, check and other idle watchers do not |
1922 |
|
|
count). |
1923 |
|
|
.PP |
1924 |
|
|
That is, as long as your process is busy handling sockets or timeouts |
1925 |
|
|
(or even signals, imagine) of the same or higher priority it will not be |
1926 |
|
|
triggered. But when your process is idle (or only lower-priority watchers |
1927 |
|
|
are pending), the idle watchers are being called once per event loop |
1928 |
|
|
iteration \- until stopped, that is, or your process receives more events |
1929 |
|
|
and becomes busy again with higher priority stuff. |
1930 |
|
|
.PP |
1931 |
|
|
The most noteworthy effect is that as long as any idle watchers are |
1932 |
|
|
active, the process will not block when waiting for new events. |
1933 |
|
|
.PP |
1934 |
|
|
Apart from keeping your process non-blocking (which is a useful |
1935 |
|
|
effect on its own sometimes), idle watchers are a good place to do |
1936 |
|
|
\&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the |
1937 |
|
|
event loop has handled all outstanding events. |
1938 |
|
|
.PP |
1939 |
|
|
\fIWatcher-Specific Functions and Data Members\fR |
1940 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
1941 |
|
|
.IP "ev_idle_init (ev_signal *, callback)" 4 |
1942 |
|
|
.IX Item "ev_idle_init (ev_signal *, callback)" |
1943 |
|
|
Initialises and configures the idle watcher \- it has no parameters of any |
1944 |
|
|
kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, |
1945 |
|
|
believe me. |
1946 |
|
|
.PP |
1947 |
|
|
\fIExamples\fR |
1948 |
|
|
.IX Subsection "Examples" |
1949 |
|
|
.PP |
1950 |
|
|
Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the |
1951 |
|
|
callback, free it. Also, use no error checking, as usual. |
1952 |
|
|
.PP |
1953 |
|
|
.Vb 7 |
1954 |
|
|
\& static void |
1955 |
|
|
\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
1956 |
|
|
\& { |
1957 |
|
|
\& free (w); |
1958 |
|
|
\& // now do something you wanted to do when the program has |
1959 |
|
|
\& // no longer anything immediate to do. |
1960 |
|
|
\& } |
1961 |
|
|
\& |
1962 |
|
|
\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
1963 |
|
|
\& ev_idle_init (idle_watcher, idle_cb); |
1964 |
|
|
\& ev_idle_start (loop, idle_cb); |
1965 |
|
|
.Ve |
1966 |
|
|
.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!" |
1967 |
|
|
.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" |
1968 |
|
|
.IX Subsection "ev_prepare and ev_check - customise your event loop!" |
1969 |
|
|
Prepare and check watchers are usually (but not always) used in tandem: |
1970 |
|
|
prepare watchers get invoked before the process blocks and check watchers |
1971 |
|
|
afterwards. |
1972 |
|
|
.PP |
1973 |
|
|
You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter |
1974 |
|
|
the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR |
1975 |
|
|
watchers. Other loops than the current one are fine, however. The |
1976 |
|
|
rationale behind this is that you do not need to check for recursion in |
1977 |
|
|
those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking, |
1978 |
|
|
\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be |
1979 |
|
|
called in pairs bracketing the blocking call. |
1980 |
|
|
.PP |
1981 |
|
|
Their main purpose is to integrate other event mechanisms into libev and |
1982 |
|
|
their use is somewhat advanced. This could be used, for example, to track |
1983 |
|
|
variable changes, implement your own watchers, integrate net-snmp or a |
1984 |
|
|
coroutine library and lots more. They are also occasionally useful if |
1985 |
|
|
you cache some data and want to flush it before blocking (for example, |
1986 |
|
|
in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR |
1987 |
|
|
watcher). |
1988 |
|
|
.PP |
1989 |
|
|
This is done by examining in each prepare call which file descriptors need |
1990 |
|
|
to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for |
1991 |
|
|
them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries |
1992 |
|
|
provide just this functionality). Then, in the check watcher you check for |
1993 |
|
|
any events that occured (by checking the pending status of all watchers |
1994 |
|
|
and stopping them) and call back into the library. The I/O and timer |
1995 |
|
|
callbacks will never actually be called (but must be valid nevertheless, |
1996 |
|
|
because you never know, you know?). |
1997 |
|
|
.PP |
1998 |
|
|
As another example, the Perl Coro module uses these hooks to integrate |
1999 |
|
|
coroutines into libev programs, by yielding to other active coroutines |
2000 |
|
|
during each prepare and only letting the process block if no coroutines |
2001 |
|
|
are ready to run (it's actually more complicated: it only runs coroutines |
2002 |
|
|
with priority higher than or equal to the event loop and one coroutine |
2003 |
|
|
of lower priority, but only once, using idle watchers to keep the event |
2004 |
|
|
loop from blocking if lower-priority coroutines are active, thus mapping |
2005 |
|
|
low-priority coroutines to idle/background tasks). |
2006 |
|
|
.PP |
2007 |
|
|
It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) |
2008 |
|
|
priority, to ensure that they are being run before any other watchers |
2009 |
|
|
after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, |
2010 |
|
|
too) should not activate (\*(L"feed\*(R") events into libev. While libev fully |
2011 |
|
|
supports this, they might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers |
2012 |
|
|
did their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other |
2013 |
|
|
(non-libev) event loops those other event loops might be in an unusable |
2014 |
|
|
state until their \f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to |
2015 |
|
|
coexist peacefully with others). |
2016 |
|
|
.PP |
2017 |
|
|
\fIWatcher-Specific Functions and Data Members\fR |
2018 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
2019 |
|
|
.IP "ev_prepare_init (ev_prepare *, callback)" 4 |
2020 |
|
|
.IX Item "ev_prepare_init (ev_prepare *, callback)" |
2021 |
|
|
.PD 0 |
2022 |
|
|
.IP "ev_check_init (ev_check *, callback)" 4 |
2023 |
|
|
.IX Item "ev_check_init (ev_check *, callback)" |
2024 |
|
|
.PD |
2025 |
|
|
Initialises and configures the prepare or check watcher \- they have no |
2026 |
|
|
parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR |
2027 |
|
|
macros, but using them is utterly, utterly and completely pointless. |
2028 |
|
|
.PP |
2029 |
|
|
\fIExamples\fR |
2030 |
|
|
.IX Subsection "Examples" |
2031 |
|
|
.PP |
2032 |
|
|
There are a number of principal ways to embed other event loops or modules |
2033 |
|
|
into libev. Here are some ideas on how to include libadns into libev |
2034 |
|
|
(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could |
2035 |
|
|
use as a working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR embeds a |
2036 |
|
|
Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0 into the |
2037 |
|
|
Glib event loop). |
2038 |
|
|
.PP |
2039 |
|
|
Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler, |
2040 |
|
|
and in a check watcher, destroy them and call into libadns. What follows |
2041 |
|
|
is pseudo-code only of course. This requires you to either use a low |
2042 |
|
|
priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as |
2043 |
|
|
the callbacks for the IO/timeout watchers might not have been called yet. |
2044 |
|
|
.PP |
2045 |
|
|
.Vb 2 |
2046 |
|
|
\& static ev_io iow [nfd]; |
2047 |
|
|
\& static ev_timer tw; |
2048 |
|
|
\& |
2049 |
|
|
\& static void |
2050 |
|
|
\& io_cb (ev_loop *loop, ev_io *w, int revents) |
2051 |
|
|
\& { |
2052 |
|
|
\& } |
2053 |
|
|
\& |
2054 |
|
|
\& // create io watchers for each fd and a timer before blocking |
2055 |
|
|
\& static void |
2056 |
|
|
\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2057 |
|
|
\& { |
2058 |
|
|
\& int timeout = 3600000; |
2059 |
|
|
\& struct pollfd fds [nfd]; |
2060 |
|
|
\& // actual code will need to loop here and realloc etc. |
2061 |
|
|
\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2062 |
|
|
\& |
2063 |
|
|
\& /* the callback is illegal, but won\*(Aqt be called as we stop during check */ |
2064 |
|
|
\& ev_timer_init (&tw, 0, timeout * 1e\-3); |
2065 |
|
|
\& ev_timer_start (loop, &tw); |
2066 |
|
|
\& |
2067 |
|
|
\& // create one ev_io per pollfd |
2068 |
|
|
\& for (int i = 0; i < nfd; ++i) |
2069 |
|
|
\& { |
2070 |
|
|
\& ev_io_init (iow + i, io_cb, fds [i].fd, |
2071 |
|
|
\& ((fds [i].events & POLLIN ? EV_READ : 0) |
2072 |
|
|
\& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
2073 |
|
|
\& |
2074 |
|
|
\& fds [i].revents = 0; |
2075 |
|
|
\& ev_io_start (loop, iow + i); |
2076 |
|
|
\& } |
2077 |
|
|
\& } |
2078 |
|
|
\& |
2079 |
|
|
\& // stop all watchers after blocking |
2080 |
|
|
\& static void |
2081 |
|
|
\& adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2082 |
|
|
\& { |
2083 |
|
|
\& ev_timer_stop (loop, &tw); |
2084 |
|
|
\& |
2085 |
|
|
\& for (int i = 0; i < nfd; ++i) |
2086 |
|
|
\& { |
2087 |
|
|
\& // set the relevant poll flags |
2088 |
|
|
\& // could also call adns_processreadable etc. here |
2089 |
|
|
\& struct pollfd *fd = fds + i; |
2090 |
|
|
\& int revents = ev_clear_pending (iow + i); |
2091 |
|
|
\& if (revents & EV_READ ) fd\->revents |= fd\->events & POLLIN; |
2092 |
|
|
\& if (revents & EV_WRITE) fd\->revents |= fd\->events & POLLOUT; |
2093 |
|
|
\& |
2094 |
|
|
\& // now stop the watcher |
2095 |
|
|
\& ev_io_stop (loop, iow + i); |
2096 |
|
|
\& } |
2097 |
|
|
\& |
2098 |
|
|
\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
2099 |
|
|
\& } |
2100 |
|
|
.Ve |
2101 |
|
|
.PP |
2102 |
|
|
Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR |
2103 |
|
|
in the prepare watcher and would dispose of the check watcher. |
2104 |
|
|
.PP |
2105 |
|
|
Method 3: If the module to be embedded supports explicit event |
2106 |
|
|
notification (adns does), you can also make use of the actual watcher |
2107 |
|
|
callbacks, and only destroy/create the watchers in the prepare watcher. |
2108 |
|
|
.PP |
2109 |
|
|
.Vb 5 |
2110 |
|
|
\& static void |
2111 |
|
|
\& timer_cb (EV_P_ ev_timer *w, int revents) |
2112 |
|
|
\& { |
2113 |
|
|
\& adns_state ads = (adns_state)w\->data; |
2114 |
|
|
\& update_now (EV_A); |
2115 |
|
|
\& |
2116 |
|
|
\& adns_processtimeouts (ads, &tv_now); |
2117 |
|
|
\& } |
2118 |
|
|
\& |
2119 |
|
|
\& static void |
2120 |
|
|
\& io_cb (EV_P_ ev_io *w, int revents) |
2121 |
|
|
\& { |
2122 |
|
|
\& adns_state ads = (adns_state)w\->data; |
2123 |
|
|
\& update_now (EV_A); |
2124 |
|
|
\& |
2125 |
|
|
\& if (revents & EV_READ ) adns_processreadable (ads, w\->fd, &tv_now); |
2126 |
|
|
\& if (revents & EV_WRITE) adns_processwriteable (ads, w\->fd, &tv_now); |
2127 |
|
|
\& } |
2128 |
|
|
\& |
2129 |
|
|
\& // do not ever call adns_afterpoll |
2130 |
|
|
.Ve |
2131 |
|
|
.PP |
2132 |
|
|
Method 4: Do not use a prepare or check watcher because the module you |
2133 |
|
|
want to embed is too inflexible to support it. Instead, youc na override |
2134 |
|
|
their poll function. The drawback with this solution is that the main |
2135 |
|
|
loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does |
2136 |
|
|
this. |
2137 |
|
|
.PP |
2138 |
|
|
.Vb 4 |
2139 |
|
|
\& static gint |
2140 |
|
|
\& event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2141 |
|
|
\& { |
2142 |
|
|
\& int got_events = 0; |
2143 |
|
|
\& |
2144 |
|
|
\& for (n = 0; n < nfds; ++n) |
2145 |
|
|
\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
2146 |
|
|
\& |
2147 |
|
|
\& if (timeout >= 0) |
2148 |
|
|
\& // create/start timer |
2149 |
|
|
\& |
2150 |
|
|
\& // poll |
2151 |
|
|
\& ev_loop (EV_A_ 0); |
2152 |
|
|
\& |
2153 |
|
|
\& // stop timer again |
2154 |
|
|
\& if (timeout >= 0) |
2155 |
|
|
\& ev_timer_stop (EV_A_ &to); |
2156 |
|
|
\& |
2157 |
|
|
\& // stop io watchers again \- their callbacks should have set |
2158 |
|
|
\& for (n = 0; n < nfds; ++n) |
2159 |
|
|
\& ev_io_stop (EV_A_ iow [n]); |
2160 |
|
|
\& |
2161 |
|
|
\& return got_events; |
2162 |
|
|
\& } |
2163 |
|
|
.Ve |
2164 |
|
|
.ie n .Sh """ev_embed"" \- when one backend isn't enough..." |
2165 |
|
|
.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." |
2166 |
|
|
.IX Subsection "ev_embed - when one backend isn't enough..." |
2167 |
|
|
This is a rather advanced watcher type that lets you embed one event loop |
2168 |
|
|
into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded |
2169 |
|
|
loop, other types of watchers might be handled in a delayed or incorrect |
2170 |
|
|
fashion and must not be used). |
2171 |
|
|
.PP |
2172 |
|
|
There are primarily two reasons you would want that: work around bugs and |
2173 |
|
|
prioritise I/O. |
2174 |
|
|
.PP |
2175 |
|
|
As an example for a bug workaround, the kqueue backend might only support |
2176 |
|
|
sockets on some platform, so it is unusable as generic backend, but you |
2177 |
|
|
still want to make use of it because you have many sockets and it scales |
2178 |
|
|
so nicely. In this case, you would create a kqueue-based loop and embed it |
2179 |
|
|
into your default loop (which might use e.g. poll). Overall operation will |
2180 |
|
|
be a bit slower because first libev has to poll and then call kevent, but |
2181 |
|
|
at least you can use both at what they are best. |
2182 |
|
|
.PP |
2183 |
|
|
As for prioritising I/O: rarely you have the case where some fds have |
2184 |
|
|
to be watched and handled very quickly (with low latency), and even |
2185 |
|
|
priorities and idle watchers might have too much overhead. In this case |
2186 |
|
|
you would put all the high priority stuff in one loop and all the rest in |
2187 |
|
|
a second one, and embed the second one in the first. |
2188 |
|
|
.PP |
2189 |
|
|
As long as the watcher is active, the callback will be invoked every time |
2190 |
|
|
there might be events pending in the embedded loop. The callback must then |
2191 |
|
|
call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke |
2192 |
|
|
their callbacks (you could also start an idle watcher to give the embedded |
2193 |
|
|
loop strictly lower priority for example). You can also set the callback |
2194 |
|
|
to \f(CW0\fR, in which case the embed watcher will automatically execute the |
2195 |
|
|
embedded loop sweep. |
2196 |
|
|
.PP |
2197 |
|
|
As long as the watcher is started it will automatically handle events. The |
2198 |
|
|
callback will be invoked whenever some events have been handled. You can |
2199 |
|
|
set the callback to \f(CW0\fR to avoid having to specify one if you are not |
2200 |
|
|
interested in that. |
2201 |
|
|
.PP |
2202 |
|
|
Also, there have not currently been made special provisions for forking: |
2203 |
|
|
when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops, |
2204 |
|
|
but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers |
2205 |
|
|
yourself. |
2206 |
|
|
.PP |
2207 |
|
|
Unfortunately, not all backends are embeddable, only the ones returned by |
2208 |
|
|
\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any |
2209 |
|
|
portable one. |
2210 |
|
|
.PP |
2211 |
|
|
So when you want to use this feature you will always have to be prepared |
2212 |
|
|
that you cannot get an embeddable loop. The recommended way to get around |
2213 |
|
|
this is to have a separate variables for your embeddable loop, try to |
2214 |
|
|
create it, and if that fails, use the normal loop for everything. |
2215 |
|
|
.PP |
2216 |
|
|
\fIWatcher-Specific Functions and Data Members\fR |
2217 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
2218 |
|
|
.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
2219 |
|
|
.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" |
2220 |
|
|
.PD 0 |
2221 |
|
|
.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
2222 |
|
|
.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" |
2223 |
|
|
.PD |
2224 |
|
|
Configures the watcher to embed the given loop, which must be |
2225 |
|
|
embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be |
2226 |
|
|
invoked automatically, otherwise it is the responsibility of the callback |
2227 |
|
|
to invoke it (it will continue to be called until the sweep has been done, |
2228 |
|
|
if you do not want thta, you need to temporarily stop the embed watcher). |
2229 |
|
|
.IP "ev_embed_sweep (loop, ev_embed *)" 4 |
2230 |
|
|
.IX Item "ev_embed_sweep (loop, ev_embed *)" |
2231 |
|
|
Make a single, non-blocking sweep over the embedded loop. This works |
2232 |
|
|
similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most |
2233 |
|
|
apropriate way for embedded loops. |
2234 |
|
|
.IP "struct ev_loop *other [read\-only]" 4 |
2235 |
|
|
.IX Item "struct ev_loop *other [read-only]" |
2236 |
|
|
The embedded event loop. |
2237 |
|
|
.PP |
2238 |
|
|
\fIExamples\fR |
2239 |
|
|
.IX Subsection "Examples" |
2240 |
|
|
.PP |
2241 |
|
|
Example: Try to get an embeddable event loop and embed it into the default |
2242 |
|
|
event loop. If that is not possible, use the default loop. The default |
2243 |
|
|
loop is stored in \f(CW\*(C`loop_hi\*(C'\fR, while the mebeddable loop is stored in |
2244 |
|
|
\&\f(CW\*(C`loop_lo\*(C'\fR (which is \f(CW\*(C`loop_hi\*(C'\fR in the acse no embeddable loop can be |
2245 |
|
|
used). |
2246 |
|
|
.PP |
2247 |
|
|
.Vb 3 |
2248 |
|
|
\& struct ev_loop *loop_hi = ev_default_init (0); |
2249 |
|
|
\& struct ev_loop *loop_lo = 0; |
2250 |
|
|
\& struct ev_embed embed; |
2251 |
|
|
\& |
2252 |
|
|
\& // see if there is a chance of getting one that works |
2253 |
|
|
\& // (remember that a flags value of 0 means autodetection) |
2254 |
|
|
\& loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2255 |
|
|
\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2256 |
|
|
\& : 0; |
2257 |
|
|
\& |
2258 |
|
|
\& // if we got one, then embed it, otherwise default to loop_hi |
2259 |
|
|
\& if (loop_lo) |
2260 |
|
|
\& { |
2261 |
|
|
\& ev_embed_init (&embed, 0, loop_lo); |
2262 |
|
|
\& ev_embed_start (loop_hi, &embed); |
2263 |
|
|
\& } |
2264 |
|
|
\& else |
2265 |
|
|
\& loop_lo = loop_hi; |
2266 |
|
|
.Ve |
2267 |
|
|
.PP |
2268 |
|
|
Example: Check if kqueue is available but not recommended and create |
2269 |
|
|
a kqueue backend for use with sockets (which usually work with any |
2270 |
|
|
kqueue implementation). Store the kqueue/socket\-only event loop in |
2271 |
|
|
\&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too). |
2272 |
|
|
.PP |
2273 |
|
|
.Vb 3 |
2274 |
|
|
\& struct ev_loop *loop = ev_default_init (0); |
2275 |
|
|
\& struct ev_loop *loop_socket = 0; |
2276 |
|
|
\& struct ev_embed embed; |
2277 |
|
|
\& |
2278 |
|
|
\& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2279 |
|
|
\& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2280 |
|
|
\& { |
2281 |
|
|
\& ev_embed_init (&embed, 0, loop_socket); |
2282 |
|
|
\& ev_embed_start (loop, &embed); |
2283 |
|
|
\& } |
2284 |
|
|
\& |
2285 |
|
|
\& if (!loop_socket) |
2286 |
|
|
\& loop_socket = loop; |
2287 |
|
|
\& |
2288 |
|
|
\& // now use loop_socket for all sockets, and loop for everything else |
2289 |
|
|
.Ve |
2290 |
|
|
.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork" |
2291 |
|
|
.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork" |
2292 |
|
|
.IX Subsection "ev_fork - the audacity to resume the event loop after a fork" |
2293 |
|
|
Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because |
2294 |
|
|
whoever is a good citizen cared to tell libev about it by calling |
2295 |
|
|
\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the |
2296 |
|
|
event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, |
2297 |
|
|
and only in the child after the fork. If whoever good citizen calling |
2298 |
|
|
\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork |
2299 |
|
|
handlers will be invoked, too, of course. |
2300 |
|
|
.PP |
2301 |
|
|
\fIWatcher-Specific Functions and Data Members\fR |
2302 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
2303 |
|
|
.IP "ev_fork_init (ev_signal *, callback)" 4 |
2304 |
|
|
.IX Item "ev_fork_init (ev_signal *, callback)" |
2305 |
|
|
Initialises and configures the fork watcher \- it has no parameters of any |
2306 |
|
|
kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless, |
2307 |
|
|
believe me. |
2308 |
|
|
.ie n .Sh """ev_async"" \- how to wake up another event loop" |
2309 |
|
|
.el .Sh "\f(CWev_async\fP \- how to wake up another event loop" |
2310 |
|
|
.IX Subsection "ev_async - how to wake up another event loop" |
2311 |
|
|
In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other |
2312 |
|
|
asynchronous sources such as signal handlers (as opposed to multiple event |
2313 |
|
|
loops \- those are of course safe to use in different threads). |
2314 |
|
|
.PP |
2315 |
|
|
Sometimes, however, you need to wake up another event loop you do not |
2316 |
|
|
control, for example because it belongs to another thread. This is what |
2317 |
|
|
\&\f(CW\*(C`ev_async\*(C'\fR watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you |
2318 |
|
|
can signal it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal |
2319 |
|
|
safe. |
2320 |
|
|
.PP |
2321 |
|
|
This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals, |
2322 |
|
|
too, are asynchronous in nature, and signals, too, will be compressed |
2323 |
|
|
(i.e. the number of callback invocations may be less than the number of |
2324 |
|
|
\&\f(CW\*(C`ev_async_sent\*(C'\fR calls). |
2325 |
|
|
.PP |
2326 |
|
|
Unlike \f(CW\*(C`ev_signal\*(C'\fR watchers, \f(CW\*(C`ev_async\*(C'\fR works with any event loop, not |
2327 |
|
|
just the default loop. |
2328 |
|
|
.PP |
2329 |
|
|
\fIQueueing\fR |
2330 |
|
|
.IX Subsection "Queueing" |
2331 |
|
|
.PP |
2332 |
|
|
\&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason |
2333 |
|
|
is that the author does not know of a simple (or any) algorithm for a |
2334 |
|
|
multiple-writer-single-reader queue that works in all cases and doesn't |
2335 |
|
|
need elaborate support such as pthreads. |
2336 |
|
|
.PP |
2337 |
|
|
That means that if you want to queue data, you have to provide your own |
2338 |
|
|
queue. But at least I can tell you would implement locking around your |
2339 |
|
|
queue: |
2340 |
|
|
.IP "queueing from a signal handler context" 4 |
2341 |
|
|
.IX Item "queueing from a signal handler context" |
2342 |
|
|
To implement race-free queueing, you simply add to the queue in the signal |
2343 |
|
|
handler but you block the signal handler in the watcher callback. Here is an example that does that for |
2344 |
|
|
some fictitiuous \s-1SIGUSR1\s0 handler: |
2345 |
|
|
.Sp |
2346 |
|
|
.Vb 1 |
2347 |
|
|
\& static ev_async mysig; |
2348 |
|
|
\& |
2349 |
|
|
\& static void |
2350 |
|
|
\& sigusr1_handler (void) |
2351 |
|
|
\& { |
2352 |
|
|
\& sometype data; |
2353 |
|
|
\& |
2354 |
|
|
\& // no locking etc. |
2355 |
|
|
\& queue_put (data); |
2356 |
|
|
\& ev_async_send (EV_DEFAULT_ &mysig); |
2357 |
|
|
\& } |
2358 |
|
|
\& |
2359 |
|
|
\& static void |
2360 |
|
|
\& mysig_cb (EV_P_ ev_async *w, int revents) |
2361 |
|
|
\& { |
2362 |
|
|
\& sometype data; |
2363 |
|
|
\& sigset_t block, prev; |
2364 |
|
|
\& |
2365 |
|
|
\& sigemptyset (&block); |
2366 |
|
|
\& sigaddset (&block, SIGUSR1); |
2367 |
|
|
\& sigprocmask (SIG_BLOCK, &block, &prev); |
2368 |
|
|
\& |
2369 |
|
|
\& while (queue_get (&data)) |
2370 |
|
|
\& process (data); |
2371 |
|
|
\& |
2372 |
|
|
\& if (sigismember (&prev, SIGUSR1) |
2373 |
|
|
\& sigprocmask (SIG_UNBLOCK, &block, 0); |
2374 |
|
|
\& } |
2375 |
|
|
.Ve |
2376 |
|
|
.Sp |
2377 |
|
|
(Note: pthreads in theory requires you to use \f(CW\*(C`pthread_setmask\*(C'\fR |
2378 |
|
|
instead of \f(CW\*(C`sigprocmask\*(C'\fR when you use threads, but libev doesn't do it |
2379 |
|
|
either...). |
2380 |
|
|
.IP "queueing from a thread context" 4 |
2381 |
|
|
.IX Item "queueing from a thread context" |
2382 |
|
|
The strategy for threads is different, as you cannot (easily) block |
2383 |
|
|
threads but you can easily preempt them, so to queue safely you need to |
2384 |
|
|
employ a traditional mutex lock, such as in this pthread example: |
2385 |
|
|
.Sp |
2386 |
|
|
.Vb 2 |
2387 |
|
|
\& static ev_async mysig; |
2388 |
|
|
\& static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
2389 |
|
|
\& |
2390 |
|
|
\& static void |
2391 |
|
|
\& otherthread (void) |
2392 |
|
|
\& { |
2393 |
|
|
\& // only need to lock the actual queueing operation |
2394 |
|
|
\& pthread_mutex_lock (&mymutex); |
2395 |
|
|
\& queue_put (data); |
2396 |
|
|
\& pthread_mutex_unlock (&mymutex); |
2397 |
|
|
\& |
2398 |
|
|
\& ev_async_send (EV_DEFAULT_ &mysig); |
2399 |
|
|
\& } |
2400 |
|
|
\& |
2401 |
|
|
\& static void |
2402 |
|
|
\& mysig_cb (EV_P_ ev_async *w, int revents) |
2403 |
|
|
\& { |
2404 |
|
|
\& pthread_mutex_lock (&mymutex); |
2405 |
|
|
\& |
2406 |
|
|
\& while (queue_get (&data)) |
2407 |
|
|
\& process (data); |
2408 |
|
|
\& |
2409 |
|
|
\& pthread_mutex_unlock (&mymutex); |
2410 |
|
|
\& } |
2411 |
|
|
.Ve |
2412 |
|
|
.PP |
2413 |
|
|
\fIWatcher-Specific Functions and Data Members\fR |
2414 |
|
|
.IX Subsection "Watcher-Specific Functions and Data Members" |
2415 |
|
|
.IP "ev_async_init (ev_async *, callback)" 4 |
2416 |
|
|
.IX Item "ev_async_init (ev_async *, callback)" |
2417 |
|
|
Initialises and configures the async watcher \- it has no parameters of any |
2418 |
|
|
kind. There is a \f(CW\*(C`ev_asynd_set\*(C'\fR macro, but using it is utterly pointless, |
2419 |
|
|
believe me. |
2420 |
|
|
.IP "ev_async_send (loop, ev_async *)" 4 |
2421 |
|
|
.IX Item "ev_async_send (loop, ev_async *)" |
2422 |
|
|
Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds |
2423 |
|
|
an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop. Unlike |
2424 |
|
|
\&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do in other threads, signal or |
2425 |
|
|
similar contexts (see the dicusssion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding |
2426 |
|
|
section below on what exactly this means). |
2427 |
|
|
.Sp |
2428 |
|
|
This call incurs the overhead of a syscall only once per loop iteration, |
2429 |
|
|
so while the overhead might be noticable, it doesn't apply to repeated |
2430 |
|
|
calls to \f(CW\*(C`ev_async_send\*(C'\fR. |
2431 |
|
|
.IP "bool = ev_async_pending (ev_async *)" 4 |
2432 |
|
|
.IX Item "bool = ev_async_pending (ev_async *)" |
2433 |
|
|
Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the |
2434 |
|
|
watcher but the event has not yet been processed (or even noted) by the |
2435 |
|
|
event loop. |
2436 |
|
|
.Sp |
2437 |
|
|
\&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When |
2438 |
|
|
the loop iterates next and checks for the watcher to have become active, |
2439 |
|
|
it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very |
2440 |
|
|
quickly check wether invoking the loop might be a good idea. |
2441 |
|
|
.Sp |
2442 |
|
|
Not that this does \fInot\fR check wether the watcher itself is pending, only |
2443 |
|
|
wether it has been requested to make this watcher pending. |
2444 |
|
|
.SH "OTHER FUNCTIONS" |
2445 |
|
|
.IX Header "OTHER FUNCTIONS" |
2446 |
|
|
There are some other functions of possible interest. Described. Here. Now. |
2447 |
|
|
.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 |
2448 |
|
|
.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" |
2449 |
|
|
This function combines a simple timer and an I/O watcher, calls your |
2450 |
|
|
callback on whichever event happens first and automatically stop both |
2451 |
|
|
watchers. This is useful if you want to wait for a single event on an fd |
2452 |
|
|
or timeout without having to allocate/configure/start/stop/free one or |
2453 |
|
|
more watchers yourself. |
2454 |
|
|
.Sp |
2455 |
|
|
If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events |
2456 |
|
|
is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and |
2457 |
|
|
\&\f(CW\*(C`events\*(C'\fR set will be craeted and started. |
2458 |
|
|
.Sp |
2459 |
|
|
If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be |
2460 |
|
|
started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and |
2461 |
|
|
repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of |
2462 |
|
|
dubious value. |
2463 |
|
|
.Sp |
2464 |
|
|
The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets |
2465 |
|
|
passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of |
2466 |
|
|
\&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR |
2467 |
|
|
value passed to \f(CW\*(C`ev_once\*(C'\fR: |
2468 |
|
|
.Sp |
2469 |
|
|
.Vb 7 |
2470 |
|
|
\& static void stdin_ready (int revents, void *arg) |
2471 |
|
|
\& { |
2472 |
|
|
\& if (revents & EV_TIMEOUT) |
2473 |
|
|
\& /* doh, nothing entered */; |
2474 |
|
|
\& else if (revents & EV_READ) |
2475 |
|
|
\& /* stdin might have data for us, joy! */; |
2476 |
|
|
\& } |
2477 |
|
|
\& |
2478 |
|
|
\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2479 |
|
|
.Ve |
2480 |
|
|
.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4 |
2481 |
|
|
.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)" |
2482 |
|
|
Feeds the given event set into the event loop, as if the specified event |
2483 |
|
|
had happened for the specified watcher (which must be a pointer to an |
2484 |
|
|
initialised but not necessarily started event watcher). |
2485 |
|
|
.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4 |
2486 |
|
|
.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)" |
2487 |
|
|
Feed an event on the given fd, as if a file descriptor backend detected |
2488 |
|
|
the given events it. |
2489 |
|
|
.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4 |
2490 |
|
|
.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)" |
2491 |
|
|
Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default |
2492 |
|
|
loop!). |
2493 |
|
|
.SH "LIBEVENT EMULATION" |
2494 |
|
|
.IX Header "LIBEVENT EMULATION" |
2495 |
|
|
Libev offers a compatibility emulation layer for libevent. It cannot |
2496 |
|
|
emulate the internals of libevent, so here are some usage hints: |
2497 |
|
|
.IP "\(bu" 4 |
2498 |
|
|
Use it by including <event.h>, as usual. |
2499 |
|
|
.IP "\(bu" 4 |
2500 |
|
|
The following members are fully supported: ev_base, ev_callback, |
2501 |
|
|
ev_arg, ev_fd, ev_res, ev_events. |
2502 |
|
|
.IP "\(bu" 4 |
2503 |
|
|
Avoid using ev_flags and the EVLIST_*\-macros, while it is |
2504 |
|
|
maintained by libev, it does not work exactly the same way as in libevent (consider |
2505 |
|
|
it a private \s-1API\s0). |
2506 |
|
|
.IP "\(bu" 4 |
2507 |
|
|
Priorities are not currently supported. Initialising priorities |
2508 |
|
|
will fail and all watchers will have the same priority, even though there |
2509 |
|
|
is an ev_pri field. |
2510 |
|
|
.IP "\(bu" 4 |
2511 |
|
|
In libevent, the last base created gets the signals, in libev, the |
2512 |
|
|
first base created (== the default loop) gets the signals. |
2513 |
|
|
.IP "\(bu" 4 |
2514 |
|
|
Other members are not supported. |
2515 |
|
|
.IP "\(bu" 4 |
2516 |
|
|
The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need |
2517 |
|
|
to use the libev header file and library. |
2518 |
|
|
.SH "\*(C+ SUPPORT" |
2519 |
|
|
.IX Header " SUPPORT" |
2520 |
|
|
Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow |
2521 |
|
|
you to use some convinience methods to start/stop watchers and also change |
2522 |
|
|
the callback model to a model using method callbacks on objects. |
2523 |
|
|
.PP |
2524 |
|
|
To use it, |
2525 |
|
|
.PP |
2526 |
|
|
.Vb 1 |
2527 |
|
|
\& #include <ev++.h> |
2528 |
|
|
.Ve |
2529 |
|
|
.PP |
2530 |
|
|
This automatically includes \fIev.h\fR and puts all of its definitions (many |
2531 |
|
|
of them macros) into the global namespace. All \*(C+ specific things are |
2532 |
|
|
put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding |
2533 |
|
|
options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. |
2534 |
|
|
.PP |
2535 |
|
|
Care has been taken to keep the overhead low. The only data member the \*(C+ |
2536 |
|
|
classes add (compared to plain C\-style watchers) is the event loop pointer |
2537 |
|
|
that the watcher is associated with (or no additional members at all if |
2538 |
|
|
you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev). |
2539 |
|
|
.PP |
2540 |
|
|
Currently, functions, and static and non-static member functions can be |
2541 |
|
|
used as callbacks. Other types should be easy to add as long as they only |
2542 |
|
|
need one additional pointer for context. If you need support for other |
2543 |
|
|
types of functors please contact the author (preferably after implementing |
2544 |
|
|
it). |
2545 |
|
|
.PP |
2546 |
|
|
Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: |
2547 |
|
|
.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4 |
2548 |
|
|
.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 |
2549 |
|
|
.IX Item "ev::READ, ev::WRITE etc." |
2550 |
|
|
These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc. |
2551 |
|
|
macros from \fIev.h\fR. |
2552 |
|
|
.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4 |
2553 |
|
|
.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4 |
2554 |
|
|
.IX Item "ev::tstamp, ev::now" |
2555 |
|
|
Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix. |
2556 |
|
|
.ie n .IP """ev::io""\fR, \f(CW""ev::timer""\fR, \f(CW""ev::periodic""\fR, \f(CW""ev::idle""\fR, \f(CW""ev::sig"" etc." 4 |
2557 |
|
|
.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 |
2558 |
|
|
.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." |
2559 |
|
|
For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of |
2560 |
|
|
the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR |
2561 |
|
|
which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro |
2562 |
|
|
defines by many implementations. |
2563 |
|
|
.Sp |
2564 |
|
|
All of those classes have these methods: |
2565 |
|
|
.RS 4 |
2566 |
|
|
.IP "ev::TYPE::TYPE ()" 4 |
2567 |
|
|
.IX Item "ev::TYPE::TYPE ()" |
2568 |
|
|
.PD 0 |
2569 |
|
|
.IP "ev::TYPE::TYPE (struct ev_loop *)" 4 |
2570 |
|
|
.IX Item "ev::TYPE::TYPE (struct ev_loop *)" |
2571 |
|
|
.IP "ev::TYPE::~TYPE" 4 |
2572 |
|
|
.IX Item "ev::TYPE::~TYPE" |
2573 |
|
|
.PD |
2574 |
|
|
The constructor (optionally) takes an event loop to associate the watcher |
2575 |
|
|
with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR. |
2576 |
|
|
.Sp |
2577 |
|
|
The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the |
2578 |
|
|
\&\f(CW\*(C`set\*(C'\fR method before starting it. |
2579 |
|
|
.Sp |
2580 |
|
|
It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR |
2581 |
|
|
method to set a callback before you can start the watcher. |
2582 |
|
|
.Sp |
2583 |
|
|
(The reason why you have to use a method is a limitation in \*(C+ which does |
2584 |
|
|
not allow explicit template arguments for constructors). |
2585 |
|
|
.Sp |
2586 |
|
|
The destructor automatically stops the watcher if it is active. |
2587 |
|
|
.IP "w\->set<class, &class::method> (object *)" 4 |
2588 |
|
|
.IX Item "w->set<class, &class::method> (object *)" |
2589 |
|
|
This method sets the callback method to call. The method has to have a |
2590 |
|
|
signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as |
2591 |
|
|
first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as |
2592 |
|
|
parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher. |
2593 |
|
|
.Sp |
2594 |
|
|
This method synthesizes efficient thunking code to call your method from |
2595 |
|
|
the C callback that libev requires. If your compiler can inline your |
2596 |
|
|
callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and |
2597 |
|
|
your compiler is good :), then the method will be fully inlined into the |
2598 |
|
|
thunking function, making it as fast as a direct C callback. |
2599 |
|
|
.Sp |
2600 |
|
|
Example: simple class declaration and watcher initialisation |
2601 |
|
|
.Sp |
2602 |
|
|
.Vb 4 |
2603 |
|
|
\& struct myclass |
2604 |
|
|
\& { |
2605 |
|
|
\& void io_cb (ev::io &w, int revents) { } |
2606 |
|
|
\& } |
2607 |
|
|
\& |
2608 |
|
|
\& myclass obj; |
2609 |
|
|
\& ev::io iow; |
2610 |
|
|
\& iow.set <myclass, &myclass::io_cb> (&obj); |
2611 |
|
|
.Ve |
2612 |
|
|
.IP "w\->set<function> (void *data = 0)" 4 |
2613 |
|
|
.IX Item "w->set<function> (void *data = 0)" |
2614 |
|
|
Also sets a callback, but uses a static method or plain function as |
2615 |
|
|
callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's |
2616 |
|
|
\&\f(CW\*(C`data\*(C'\fR member and is free for you to use. |
2617 |
|
|
.Sp |
2618 |
|
|
The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR. |
2619 |
|
|
.Sp |
2620 |
|
|
See the method\-\f(CW\*(C`set\*(C'\fR above for more details. |
2621 |
|
|
.Sp |
2622 |
|
|
Example: |
2623 |
|
|
.Sp |
2624 |
|
|
.Vb 2 |
2625 |
|
|
\& static void io_cb (ev::io &w, int revents) { } |
2626 |
|
|
\& iow.set <io_cb> (); |
2627 |
|
|
.Ve |
2628 |
|
|
.IP "w\->set (struct ev_loop *)" 4 |
2629 |
|
|
.IX Item "w->set (struct ev_loop *)" |
2630 |
|
|
Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only |
2631 |
|
|
do this when the watcher is inactive (and not pending either). |
2632 |
|
|
.IP "w\->set ([args])" 4 |
2633 |
|
|
.IX Item "w->set ([args])" |
2634 |
|
|
Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be |
2635 |
|
|
called at least once. Unlike the C counterpart, an active watcher gets |
2636 |
|
|
automatically stopped and restarted when reconfiguring it with this |
2637 |
|
|
method. |
2638 |
|
|
.IP "w\->start ()" 4 |
2639 |
|
|
.IX Item "w->start ()" |
2640 |
|
|
Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the |
2641 |
|
|
constructor already stores the event loop. |
2642 |
|
|
.IP "w\->stop ()" 4 |
2643 |
|
|
.IX Item "w->stop ()" |
2644 |
|
|
Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. |
2645 |
|
|
.ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4 |
2646 |
|
|
.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4 |
2647 |
|
|
.IX Item "w->again () (ev::timer, ev::periodic only)" |
2648 |
|
|
For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding |
2649 |
|
|
\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. |
2650 |
|
|
.ie n .IP "w\->sweep () (""ev::embed"" only)" 4 |
2651 |
|
|
.el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4 |
2652 |
|
|
.IX Item "w->sweep () (ev::embed only)" |
2653 |
|
|
Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR. |
2654 |
|
|
.ie n .IP "w\->update () (""ev::stat"" only)" 4 |
2655 |
|
|
.el .IP "w\->update () (\f(CWev::stat\fR only)" 4 |
2656 |
|
|
.IX Item "w->update () (ev::stat only)" |
2657 |
|
|
Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR. |
2658 |
|
|
.RE |
2659 |
|
|
.RS 4 |
2660 |
|
|
.RE |
2661 |
|
|
.PP |
2662 |
|
|
Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in |
2663 |
|
|
the constructor. |
2664 |
|
|
.PP |
2665 |
|
|
.Vb 4 |
2666 |
|
|
\& class myclass |
2667 |
|
|
\& { |
2668 |
|
|
\& ev::io io; void io_cb (ev::io &w, int revents); |
2669 |
|
|
\& ev:idle idle void idle_cb (ev::idle &w, int revents); |
2670 |
|
|
\& |
2671 |
|
|
\& myclass (int fd) |
2672 |
|
|
\& { |
2673 |
|
|
\& io .set <myclass, &myclass::io_cb > (this); |
2674 |
|
|
\& idle.set <myclass, &myclass::idle_cb> (this); |
2675 |
|
|
\& |
2676 |
|
|
\& io.start (fd, ev::READ); |
2677 |
|
|
\& } |
2678 |
|
|
\& }; |
2679 |
|
|
.Ve |
2680 |
|
|
.SH "OTHER LANGUAGE BINDINGS" |
2681 |
|
|
.IX Header "OTHER LANGUAGE BINDINGS" |
2682 |
|
|
Libev does not offer other language bindings itself, but bindings for a |
2683 |
|
|
numbe rof languages exist in the form of third-party packages. If you know |
2684 |
|
|
any interesting language binding in addition to the ones listed here, drop |
2685 |
|
|
me a note. |
2686 |
|
|
.IP "Perl" 4 |
2687 |
|
|
.IX Item "Perl" |
2688 |
|
|
The \s-1EV\s0 module implements the full libev \s-1API\s0 and is actually used to test |
2689 |
|
|
libev. \s-1EV\s0 is developed together with libev. Apart from the \s-1EV\s0 core module, |
2690 |
|
|
there are additional modules that implement libev-compatible interfaces |
2691 |
|
|
to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR), \f(CW\*(C`Net::SNMP\*(C'\fR (\f(CW\*(C`Net::SNMP::EV\*(C'\fR) and the |
2692 |
|
|
\&\f(CW\*(C`libglib\*(C'\fR event core (\f(CW\*(C`Glib::EV\*(C'\fR and \f(CW\*(C`EV::Glib\*(C'\fR). |
2693 |
|
|
.Sp |
2694 |
|
|
It can be found and installed via \s-1CPAN\s0, its homepage is found at |
2695 |
|
|
<http://software.schmorp.de/pkg/EV>. |
2696 |
|
|
.IP "Ruby" 4 |
2697 |
|
|
.IX Item "Ruby" |
2698 |
|
|
Tony Arcieri has written a ruby extension that offers access to a subset |
2699 |
|
|
of the libev \s-1API\s0 and adds filehandle abstractions, asynchronous \s-1DNS\s0 and |
2700 |
|
|
more on top of it. It can be found via gem servers. Its homepage is at |
2701 |
|
|
<http://rev.rubyforge.org/>. |
2702 |
|
|
.IP "D" 4 |
2703 |
|
|
.IX Item "D" |
2704 |
|
|
Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to |
2705 |
|
|
be found at <http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
2706 |
|
|
.SH "MACRO MAGIC" |
2707 |
|
|
.IX Header "MACRO MAGIC" |
2708 |
|
|
Libev can be compiled with a variety of options, the most fundamantal |
2709 |
|
|
of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) |
2710 |
|
|
functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. |
2711 |
|
|
.PP |
2712 |
|
|
To make it easier to write programs that cope with either variant, the |
2713 |
|
|
following macros are defined: |
2714 |
|
|
.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4 |
2715 |
|
|
.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4 |
2716 |
|
|
.IX Item "EV_A, EV_A_" |
2717 |
|
|
This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev |
2718 |
|
|
loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument, |
2719 |
|
|
\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example: |
2720 |
|
|
.Sp |
2721 |
|
|
.Vb 3 |
2722 |
|
|
\& ev_unref (EV_A); |
2723 |
|
|
\& ev_timer_add (EV_A_ watcher); |
2724 |
|
|
\& ev_loop (EV_A_ 0); |
2725 |
|
|
.Ve |
2726 |
|
|
.Sp |
2727 |
|
|
It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope, |
2728 |
|
|
which is often provided by the following macro. |
2729 |
|
|
.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4 |
2730 |
|
|
.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4 |
2731 |
|
|
.IX Item "EV_P, EV_P_" |
2732 |
|
|
This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev |
2733 |
|
|
loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter, |
2734 |
|
|
\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example: |
2735 |
|
|
.Sp |
2736 |
|
|
.Vb 2 |
2737 |
|
|
\& // this is how ev_unref is being declared |
2738 |
|
|
\& static void ev_unref (EV_P); |
2739 |
|
|
\& |
2740 |
|
|
\& // this is how you can declare your typical callback |
2741 |
|
|
\& static void cb (EV_P_ ev_timer *w, int revents) |
2742 |
|
|
.Ve |
2743 |
|
|
.Sp |
2744 |
|
|
It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite |
2745 |
|
|
suitable for use with \f(CW\*(C`EV_A\*(C'\fR. |
2746 |
|
|
.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4 |
2747 |
|
|
.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 |
2748 |
|
|
.IX Item "EV_DEFAULT, EV_DEFAULT_" |
2749 |
|
|
Similar to the other two macros, this gives you the value of the default |
2750 |
|
|
loop, if multiple loops are supported (\*(L"ev loop default\*(R"). |
2751 |
|
|
.ie n .IP """EV_DEFAULT_UC""\fR, \f(CW""EV_DEFAULT_UC_""" 4 |
2752 |
|
|
.el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4 |
2753 |
|
|
.IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_" |
2754 |
|
|
Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the |
2755 |
|
|
default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour |
2756 |
|
|
is undefined when the default loop has not been initialised by a previous |
2757 |
|
|
execution of \f(CW\*(C`EV_DEFAULT\*(C'\fR, \f(CW\*(C`EV_DEFAULT_\*(C'\fR or \f(CW\*(C`ev_default_init (...)\*(C'\fR. |
2758 |
|
|
.Sp |
2759 |
|
|
It is often prudent to use \f(CW\*(C`EV_DEFAULT\*(C'\fR when initialising the first |
2760 |
|
|
watcher in a function but use \f(CW\*(C`EV_DEFAULT_UC\*(C'\fR afterwards. |
2761 |
|
|
.PP |
2762 |
|
|
Example: Declare and initialise a check watcher, utilising the above |
2763 |
|
|
macros so it will work regardless of whether multiple loops are supported |
2764 |
|
|
or not. |
2765 |
|
|
.PP |
2766 |
|
|
.Vb 5 |
2767 |
|
|
\& static void |
2768 |
|
|
\& check_cb (EV_P_ ev_timer *w, int revents) |
2769 |
|
|
\& { |
2770 |
|
|
\& ev_check_stop (EV_A_ w); |
2771 |
|
|
\& } |
2772 |
|
|
\& |
2773 |
|
|
\& ev_check check; |
2774 |
|
|
\& ev_check_init (&check, check_cb); |
2775 |
|
|
\& ev_check_start (EV_DEFAULT_ &check); |
2776 |
|
|
\& ev_loop (EV_DEFAULT_ 0); |
2777 |
|
|
.Ve |
2778 |
|
|
.SH "EMBEDDING" |
2779 |
|
|
.IX Header "EMBEDDING" |
2780 |
|
|
Libev can (and often is) directly embedded into host |
2781 |
|
|
applications. Examples of applications that embed it include the Deliantra |
2782 |
|
|
Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe) |
2783 |
|
|
and rxvt-unicode. |
2784 |
|
|
.PP |
2785 |
|
|
The goal is to enable you to just copy the necessary files into your |
2786 |
|
|
source directory without having to change even a single line in them, so |
2787 |
|
|
you can easily upgrade by simply copying (or having a checked-out copy of |
2788 |
|
|
libev somewhere in your source tree). |
2789 |
|
|
.Sh "\s-1FILESETS\s0" |
2790 |
|
|
.IX Subsection "FILESETS" |
2791 |
|
|
Depending on what features you need you need to include one or more sets of files |
2792 |
|
|
in your app. |
2793 |
|
|
.PP |
2794 |
|
|
\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR |
2795 |
|
|
.IX Subsection "CORE EVENT LOOP" |
2796 |
|
|
.PP |
2797 |
|
|
To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual |
2798 |
|
|
configuration (no autoconf): |
2799 |
|
|
.PP |
2800 |
|
|
.Vb 2 |
2801 |
|
|
\& #define EV_STANDALONE 1 |
2802 |
|
|
\& #include "ev.c" |
2803 |
|
|
.Ve |
2804 |
|
|
.PP |
2805 |
|
|
This will automatically include \fIev.h\fR, too, and should be done in a |
2806 |
|
|
single C source file only to provide the function implementations. To use |
2807 |
|
|
it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best |
2808 |
|
|
done by writing a wrapper around \fIev.h\fR that you can include instead and |
2809 |
|
|
where you can put other configuration options): |
2810 |
|
|
.PP |
2811 |
|
|
.Vb 2 |
2812 |
|
|
\& #define EV_STANDALONE 1 |
2813 |
|
|
\& #include "ev.h" |
2814 |
|
|
.Ve |
2815 |
|
|
.PP |
2816 |
|
|
Both header files and implementation files can be compiled with a \*(C+ |
2817 |
|
|
compiler (at least, thats a stated goal, and breakage will be treated |
2818 |
|
|
as a bug). |
2819 |
|
|
.PP |
2820 |
|
|
You need the following files in your source tree, or in a directory |
2821 |
|
|
in your include path (e.g. in libev/ when using \-Ilibev): |
2822 |
|
|
.PP |
2823 |
|
|
.Vb 4 |
2824 |
|
|
\& ev.h |
2825 |
|
|
\& ev.c |
2826 |
|
|
\& ev_vars.h |
2827 |
|
|
\& ev_wrap.h |
2828 |
|
|
\& |
2829 |
|
|
\& ev_win32.c required on win32 platforms only |
2830 |
|
|
\& |
2831 |
|
|
\& ev_select.c only when select backend is enabled (which is enabled by default) |
2832 |
|
|
\& ev_poll.c only when poll backend is enabled (disabled by default) |
2833 |
|
|
\& ev_epoll.c only when the epoll backend is enabled (disabled by default) |
2834 |
|
|
\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
2835 |
|
|
\& ev_port.c only when the solaris port backend is enabled (disabled by default) |
2836 |
|
|
.Ve |
2837 |
|
|
.PP |
2838 |
|
|
\&\fIev.c\fR includes the backend files directly when enabled, so you only need |
2839 |
|
|
to compile this single file. |
2840 |
|
|
.PP |
2841 |
|
|
\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR |
2842 |
|
|
.IX Subsection "LIBEVENT COMPATIBILITY API" |
2843 |
|
|
.PP |
2844 |
|
|
To include the libevent compatibility \s-1API\s0, also include: |
2845 |
|
|
.PP |
2846 |
|
|
.Vb 1 |
2847 |
|
|
\& #include "event.c" |
2848 |
|
|
.Ve |
2849 |
|
|
.PP |
2850 |
|
|
in the file including \fIev.c\fR, and: |
2851 |
|
|
.PP |
2852 |
|
|
.Vb 1 |
2853 |
|
|
\& #include "event.h" |
2854 |
|
|
.Ve |
2855 |
|
|
.PP |
2856 |
|
|
in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR. |
2857 |
|
|
.PP |
2858 |
|
|
You need the following additional files for this: |
2859 |
|
|
.PP |
2860 |
|
|
.Vb 2 |
2861 |
|
|
\& event.h |
2862 |
|
|
\& event.c |
2863 |
|
|
.Ve |
2864 |
|
|
.PP |
2865 |
|
|
\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR |
2866 |
|
|
.IX Subsection "AUTOCONF SUPPORT" |
2867 |
|
|
.PP |
2868 |
|
|
Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in |
2869 |
|
|
whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your |
2870 |
|
|
\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then |
2871 |
|
|
include \fIconfig.h\fR and configure itself accordingly. |
2872 |
|
|
.PP |
2873 |
|
|
For this of course you need the m4 file: |
2874 |
|
|
.PP |
2875 |
|
|
.Vb 1 |
2876 |
|
|
\& libev.m4 |
2877 |
|
|
.Ve |
2878 |
|
|
.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0" |
2879 |
|
|
.IX Subsection "PREPROCESSOR SYMBOLS/MACROS" |
2880 |
|
|
Libev can be configured via a variety of preprocessor symbols you have to |
2881 |
|
|
define before including any of its files. The default in the absense of |
2882 |
|
|
autoconf is noted for every option. |
2883 |
|
|
.IP "\s-1EV_STANDALONE\s0" 4 |
2884 |
|
|
.IX Item "EV_STANDALONE" |
2885 |
|
|
Must always be \f(CW1\fR if you do not use autoconf configuration, which |
2886 |
|
|
keeps libev from including \fIconfig.h\fR, and it also defines dummy |
2887 |
|
|
implementations for some libevent functions (such as logging, which is not |
2888 |
|
|
supported). It will also not define any of the structs usually found in |
2889 |
|
|
\&\fIevent.h\fR that are not directly supported by the libev core alone. |
2890 |
|
|
.IP "\s-1EV_USE_MONOTONIC\s0" 4 |
2891 |
|
|
.IX Item "EV_USE_MONOTONIC" |
2892 |
|
|
If defined to be \f(CW1\fR, libev will try to detect the availability of the |
2893 |
|
|
monotonic clock option at both compiletime and runtime. Otherwise no use |
2894 |
|
|
of the monotonic clock option will be attempted. If you enable this, you |
2895 |
|
|
usually have to link against librt or something similar. Enabling it when |
2896 |
|
|
the functionality isn't available is safe, though, although you have |
2897 |
|
|
to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR |
2898 |
|
|
function is hiding in (often \fI\-lrt\fR). |
2899 |
|
|
.IP "\s-1EV_USE_REALTIME\s0" 4 |
2900 |
|
|
.IX Item "EV_USE_REALTIME" |
2901 |
|
|
If defined to be \f(CW1\fR, libev will try to detect the availability of the |
2902 |
|
|
realtime clock option at compiletime (and assume its availability at |
2903 |
|
|
runtime if successful). Otherwise no use of the realtime clock option will |
2904 |
|
|
be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get |
2905 |
|
|
(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the |
2906 |
|
|
note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. |
2907 |
|
|
.IP "\s-1EV_USE_NANOSLEEP\s0" 4 |
2908 |
|
|
.IX Item "EV_USE_NANOSLEEP" |
2909 |
|
|
If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available |
2910 |
|
|
and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. |
2911 |
|
|
.IP "\s-1EV_USE_EVENTFD\s0" 4 |
2912 |
|
|
.IX Item "EV_USE_EVENTFD" |
2913 |
|
|
If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is |
2914 |
|
|
available and will probe for kernel support at runtime. This will improve |
2915 |
|
|
\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption. |
2916 |
|
|
If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
2917 |
|
|
2.7 or newer, otherwise disabled. |
2918 |
|
|
.IP "\s-1EV_USE_SELECT\s0" 4 |
2919 |
|
|
.IX Item "EV_USE_SELECT" |
2920 |
|
|
If undefined or defined to be \f(CW1\fR, libev will compile in support for the |
2921 |
|
|
\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no |
2922 |
|
|
other method takes over, select will be it. Otherwise the select backend |
2923 |
|
|
will not be compiled in. |
2924 |
|
|
.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 |
2925 |
|
|
.IX Item "EV_SELECT_USE_FD_SET" |
2926 |
|
|
If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR |
2927 |
|
|
structure. This is useful if libev doesn't compile due to a missing |
2928 |
|
|
\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on |
2929 |
|
|
exotic systems. This usually limits the range of file descriptors to some |
2930 |
|
|
low limit such as 1024 or might have other limitations (winsocket only |
2931 |
|
|
allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might |
2932 |
|
|
influence the size of the \f(CW\*(C`fd_set\*(C'\fR used. |
2933 |
|
|
.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 |
2934 |
|
|
.IX Item "EV_SELECT_IS_WINSOCKET" |
2935 |
|
|
When defined to \f(CW1\fR, the select backend will assume that |
2936 |
|
|
select/socket/connect etc. don't understand file descriptors but |
2937 |
|
|
wants osf handles on win32 (this is the case when the select to |
2938 |
|
|
be used is the winsock select). This means that it will call |
2939 |
|
|
\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise, |
2940 |
|
|
it is assumed that all these functions actually work on fds, even |
2941 |
|
|
on win32. Should not be defined on non\-win32 platforms. |
2942 |
|
|
.IP "\s-1EV_FD_TO_WIN32_HANDLE\s0" 4 |
2943 |
|
|
.IX Item "EV_FD_TO_WIN32_HANDLE" |
2944 |
|
|
If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map |
2945 |
|
|
file descriptors to socket handles. When not defining this symbol (the |
2946 |
|
|
default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually |
2947 |
|
|
correct. In some cases, programs use their own file descriptor management, |
2948 |
|
|
in which case they can provide this function to map fds to socket handles. |
2949 |
|
|
.IP "\s-1EV_USE_POLL\s0" 4 |
2950 |
|
|
.IX Item "EV_USE_POLL" |
2951 |
|
|
If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2) |
2952 |
|
|
backend. Otherwise it will be enabled on non\-win32 platforms. It |
2953 |
|
|
takes precedence over select. |
2954 |
|
|
.IP "\s-1EV_USE_EPOLL\s0" 4 |
2955 |
|
|
.IX Item "EV_USE_EPOLL" |
2956 |
|
|
If defined to be \f(CW1\fR, libev will compile in support for the Linux |
2957 |
|
|
\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, |
2958 |
|
|
otherwise another method will be used as fallback. This is the preferred |
2959 |
|
|
backend for GNU/Linux systems. If undefined, it will be enabled if the |
2960 |
|
|
headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2961 |
|
|
.IP "\s-1EV_USE_KQUEUE\s0" 4 |
2962 |
|
|
.IX Item "EV_USE_KQUEUE" |
2963 |
|
|
If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style |
2964 |
|
|
\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, |
2965 |
|
|
otherwise another method will be used as fallback. This is the preferred |
2966 |
|
|
backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only |
2967 |
|
|
supports some types of fds correctly (the only platform we found that |
2968 |
|
|
supports ptys for example was NetBSD), so kqueue might be compiled in, but |
2969 |
|
|
not be used unless explicitly requested. The best way to use it is to find |
2970 |
|
|
out whether kqueue supports your type of fd properly and use an embedded |
2971 |
|
|
kqueue loop. |
2972 |
|
|
.IP "\s-1EV_USE_PORT\s0" 4 |
2973 |
|
|
.IX Item "EV_USE_PORT" |
2974 |
|
|
If defined to be \f(CW1\fR, libev will compile in support for the Solaris |
2975 |
|
|
10 port style backend. Its availability will be detected at runtime, |
2976 |
|
|
otherwise another method will be used as fallback. This is the preferred |
2977 |
|
|
backend for Solaris 10 systems. |
2978 |
|
|
.IP "\s-1EV_USE_DEVPOLL\s0" 4 |
2979 |
|
|
.IX Item "EV_USE_DEVPOLL" |
2980 |
|
|
reserved for future expansion, works like the \s-1USE\s0 symbols above. |
2981 |
|
|
.IP "\s-1EV_USE_INOTIFY\s0" 4 |
2982 |
|
|
.IX Item "EV_USE_INOTIFY" |
2983 |
|
|
If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify |
2984 |
|
|
interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will |
2985 |
|
|
be detected at runtime. If undefined, it will be enabled if the headers |
2986 |
|
|
indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2987 |
|
|
.IP "\s-1EV_ATOMIC_T\s0" 4 |
2988 |
|
|
.IX Item "EV_ATOMIC_T" |
2989 |
|
|
Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose |
2990 |
|
|
access is atomic with respect to other threads or signal contexts. No such |
2991 |
|
|
type is easily found in the C language, so you can provide your own type |
2992 |
|
|
that you know is safe for your purposes. It is used both for signal handler \*(L"locking\*(R" |
2993 |
|
|
as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR watchers. |
2994 |
|
|
.Sp |
2995 |
|
|
In the absense of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR |
2996 |
|
|
(from \fIsignal.h\fR), which is usually good enough on most platforms. |
2997 |
|
|
.IP "\s-1EV_H\s0" 4 |
2998 |
|
|
.IX Item "EV_H" |
2999 |
|
|
The name of the \fIev.h\fR header file used to include it. The default if |
3000 |
|
|
undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be |
3001 |
|
|
used to virtually rename the \fIev.h\fR header file in case of conflicts. |
3002 |
|
|
.IP "\s-1EV_CONFIG_H\s0" 4 |
3003 |
|
|
.IX Item "EV_CONFIG_H" |
3004 |
|
|
If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override |
3005 |
|
|
\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to |
3006 |
|
|
\&\f(CW\*(C`EV_H\*(C'\fR, above. |
3007 |
|
|
.IP "\s-1EV_EVENT_H\s0" 4 |
3008 |
|
|
.IX Item "EV_EVENT_H" |
3009 |
|
|
Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea |
3010 |
|
|
of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR. |
3011 |
|
|
.IP "\s-1EV_PROTOTYPES\s0" 4 |
3012 |
|
|
.IX Item "EV_PROTOTYPES" |
3013 |
|
|
If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function |
3014 |
|
|
prototypes, but still define all the structs and other symbols. This is |
3015 |
|
|
occasionally useful if you want to provide your own wrapper functions |
3016 |
|
|
around libev functions. |
3017 |
|
|
.IP "\s-1EV_MULTIPLICITY\s0" 4 |
3018 |
|
|
.IX Item "EV_MULTIPLICITY" |
3019 |
|
|
If undefined or defined to \f(CW1\fR, then all event-loop-specific functions |
3020 |
|
|
will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create |
3021 |
|
|
additional independent event loops. Otherwise there will be no support |
3022 |
|
|
for multiple event loops and there is no first event loop pointer |
3023 |
|
|
argument. Instead, all functions act on the single default loop. |
3024 |
|
|
.IP "\s-1EV_MINPRI\s0" 4 |
3025 |
|
|
.IX Item "EV_MINPRI" |
3026 |
|
|
.PD 0 |
3027 |
|
|
.IP "\s-1EV_MAXPRI\s0" 4 |
3028 |
|
|
.IX Item "EV_MAXPRI" |
3029 |
|
|
.PD |
3030 |
|
|
The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to |
3031 |
|
|
\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can |
3032 |
|
|
provide for more priorities by overriding those symbols (usually defined |
3033 |
|
|
to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively). |
3034 |
|
|
.Sp |
3035 |
|
|
When doing priority-based operations, libev usually has to linearly search |
3036 |
|
|
all the priorities, so having many of them (hundreds) uses a lot of space |
3037 |
|
|
and time, so using the defaults of five priorities (\-2 .. +2) is usually |
3038 |
|
|
fine. |
3039 |
|
|
.Sp |
3040 |
|
|
If your embedding app does not need any priorities, defining these both to |
3041 |
|
|
\&\f(CW0\fR will save some memory and cpu. |
3042 |
|
|
.IP "\s-1EV_PERIODIC_ENABLE\s0" 4 |
3043 |
|
|
.IX Item "EV_PERIODIC_ENABLE" |
3044 |
|
|
If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If |
3045 |
|
|
defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
3046 |
|
|
code. |
3047 |
|
|
.IP "\s-1EV_IDLE_ENABLE\s0" 4 |
3048 |
|
|
.IX Item "EV_IDLE_ENABLE" |
3049 |
|
|
If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If |
3050 |
|
|
defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
3051 |
|
|
code. |
3052 |
|
|
.IP "\s-1EV_EMBED_ENABLE\s0" 4 |
3053 |
|
|
.IX Item "EV_EMBED_ENABLE" |
3054 |
|
|
If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If |
3055 |
|
|
defined to be \f(CW0\fR, then they are not. |
3056 |
|
|
.IP "\s-1EV_STAT_ENABLE\s0" 4 |
3057 |
|
|
.IX Item "EV_STAT_ENABLE" |
3058 |
|
|
If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If |
3059 |
|
|
defined to be \f(CW0\fR, then they are not. |
3060 |
|
|
.IP "\s-1EV_FORK_ENABLE\s0" 4 |
3061 |
|
|
.IX Item "EV_FORK_ENABLE" |
3062 |
|
|
If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If |
3063 |
|
|
defined to be \f(CW0\fR, then they are not. |
3064 |
|
|
.IP "\s-1EV_ASYNC_ENABLE\s0" 4 |
3065 |
|
|
.IX Item "EV_ASYNC_ENABLE" |
3066 |
|
|
If undefined or defined to be \f(CW1\fR, then async watchers are supported. If |
3067 |
|
|
defined to be \f(CW0\fR, then they are not. |
3068 |
|
|
.IP "\s-1EV_MINIMAL\s0" 4 |
3069 |
|
|
.IX Item "EV_MINIMAL" |
3070 |
|
|
If you need to shave off some kilobytes of code at the expense of some |
3071 |
|
|
speed, define this symbol to \f(CW1\fR. Currently this is used to override some |
3072 |
|
|
inlining decisions, saves roughly 30% codesize of amd64. It also selects a |
3073 |
|
|
much smaller 2\-heap for timer management over the default 4\-heap. |
3074 |
|
|
.IP "\s-1EV_PID_HASHSIZE\s0" 4 |
3075 |
|
|
.IX Item "EV_PID_HASHSIZE" |
3076 |
|
|
\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by |
3077 |
|
|
pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more |
3078 |
|
|
than enough. If you need to manage thousands of children you might want to |
3079 |
|
|
increase this value (\fImust\fR be a power of two). |
3080 |
|
|
.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4 |
3081 |
|
|
.IX Item "EV_INOTIFY_HASHSIZE" |
3082 |
|
|
\&\f(CW\*(C`ev_stat\*(C'\fR watchers use a small hash table to distribute workload by |
3083 |
|
|
inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), |
3084 |
|
|
usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR |
3085 |
|
|
watchers you might want to increase this value (\fImust\fR be a power of |
3086 |
|
|
two). |
3087 |
|
|
.IP "\s-1EV_USE_4HEAP\s0" 4 |
3088 |
|
|
.IX Item "EV_USE_4HEAP" |
3089 |
|
|
Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3090 |
|
|
timer and periodics heap, libev uses a 4\-heap when this symbol is defined |
3091 |
|
|
to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has a |
3092 |
|
|
noticable after performance with many (thousands) of watchers. |
3093 |
|
|
.Sp |
3094 |
|
|
The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR |
3095 |
|
|
(disabled). |
3096 |
|
|
.IP "\s-1EV_HEAP_CACHE_AT\s0" 4 |
3097 |
|
|
.IX Item "EV_HEAP_CACHE_AT" |
3098 |
|
|
Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3099 |
|
|
timer and periodics heap, libev can cache the timestamp (\fIat\fR) within |
3100 |
|
|
the heap structure (selected by defining \f(CW\*(C`EV_HEAP_CACHE_AT\*(C'\fR to \f(CW1\fR), |
3101 |
|
|
which uses 8\-12 bytes more per watcher and a few hundred bytes more code, |
3102 |
|
|
but avoids random read accesses on heap changes. This noticably improves |
3103 |
|
|
performance noticably with with many (hundreds) of watchers. |
3104 |
|
|
.Sp |
3105 |
|
|
The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR |
3106 |
|
|
(disabled). |
3107 |
|
|
.IP "\s-1EV_COMMON\s0" 4 |
3108 |
|
|
.IX Item "EV_COMMON" |
3109 |
|
|
By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining |
3110 |
|
|
this macro to a something else you can include more and other types of |
3111 |
|
|
members. You have to define it each time you include one of the files, |
3112 |
|
|
though, and it must be identical each time. |
3113 |
|
|
.Sp |
3114 |
|
|
For example, the perl \s-1EV\s0 module uses something like this: |
3115 |
|
|
.Sp |
3116 |
|
|
.Vb 3 |
3117 |
|
|
\& #define EV_COMMON \e |
3118 |
|
|
\& SV *self; /* contains this struct */ \e |
3119 |
|
|
\& SV *cb_sv, *fh /* note no trailing ";" */ |
3120 |
|
|
.Ve |
3121 |
|
|
.IP "\s-1EV_CB_DECLARE\s0 (type)" 4 |
3122 |
|
|
.IX Item "EV_CB_DECLARE (type)" |
3123 |
|
|
.PD 0 |
3124 |
|
|
.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4 |
3125 |
|
|
.IX Item "EV_CB_INVOKE (watcher, revents)" |
3126 |
|
|
.IP "ev_set_cb (ev, cb)" 4 |
3127 |
|
|
.IX Item "ev_set_cb (ev, cb)" |
3128 |
|
|
.PD |
3129 |
|
|
Can be used to change the callback member declaration in each watcher, |
3130 |
|
|
and the way callbacks are invoked and set. Must expand to a struct member |
3131 |
|
|
definition and a statement, respectively. See the \fIev.h\fR header file for |
3132 |
|
|
their default definitions. One possible use for overriding these is to |
3133 |
|
|
avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use |
3134 |
|
|
method calls instead of plain function calls in \*(C+. |
3135 |
|
|
.Sh "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0" |
3136 |
|
|
.IX Subsection "EXPORTED API SYMBOLS" |
3137 |
|
|
If you need to re-export the \s-1API\s0 (e.g. via a dll) and you need a list of |
3138 |
|
|
exported symbols, you can use the provided \fISymbol.*\fR files which list |
3139 |
|
|
all public symbols, one per line: |
3140 |
|
|
.PP |
3141 |
|
|
.Vb 2 |
3142 |
|
|
\& Symbols.ev for libev proper |
3143 |
|
|
\& Symbols.event for the libevent emulation |
3144 |
|
|
.Ve |
3145 |
|
|
.PP |
3146 |
|
|
This can also be used to rename all public symbols to avoid clashes with |
3147 |
|
|
multiple versions of libev linked together (which is obviously bad in |
3148 |
|
|
itself, but sometimes it is inconvinient to avoid this). |
3149 |
|
|
.PP |
3150 |
|
|
A sed command like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to |
3151 |
|
|
include before including \fIev.h\fR: |
3152 |
|
|
.PP |
3153 |
|
|
.Vb 1 |
3154 |
|
|
\& <Symbols.ev sed \-e "s/.*/#define & myprefix_&/" >wrap.h |
3155 |
|
|
.Ve |
|