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=head1 NAME |
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libev - a high performance full-featured event loop written in C |
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=head1 SYNOPSIS |
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#include <ev.h> |
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=head1 DESCRIPTION |
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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 occuring), and it will manage |
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these event sources and provide your program with events. |
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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 I<event loop> handler, and will then |
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communicate events via a callback mechanism. |
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You register interest in certain events by registering so-called I<event |
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watchers>, which are relatively small C structures you initialise with the |
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details of the event, and then hand it over to libev by I<starting> the |
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watcher. |
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=head1 FEATURES |
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Libev supports select, poll, the linux-specific epoll and the bsd-specific |
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kqueue mechanisms for file descriptor events, relative timers, absolute |
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timers with customised rescheduling, signal events, process status change |
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events (related to SIGCHLD), and event watchers dealing with the event |
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loop mechanism itself (idle, prepare and check watchers). It also is quite |
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fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing |
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it to libevent for example). |
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=head1 CONVENTIONS |
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Libev is very configurable. In this manual the default configuration |
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will be described, which supports multiple event loops. For more info |
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about various configuration options please have a look at the file |
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F<README.embed> in the libev distribution. If libev was configured without |
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support for multiple event loops, then all functions taking an initial |
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argument of name C<loop> (which is always of type C<struct ev_loop *>) |
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will not have this argument. |
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=head1 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 (POSIX) epoch (somewhere near |
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the beginning of 1970, details are complicated, don't ask). This type is |
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called C<ev_tstamp>, which is what you should use too. It usually aliases |
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to the C<double> type in C, and when you need to do any calculations on |
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it, you should treat it as such. |
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=head1 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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1.1 |
=over 4 |
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=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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C<ev_now> function is usually faster and also often returns the timestamp |
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you actually want to know. |
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=item int ev_version_major () |
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=item int ev_version_minor () |
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You can find out the major and minor version numbers of the library |
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you linked against by calling the functions C<ev_version_major> and |
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C<ev_version_minor>. If you want, you can compare against the global |
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symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the |
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version of the library your program was compiled against. |
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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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Example: make sure we haven't accidentally been linked against the wrong |
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version: |
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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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=item unsigned int ev_supported_backends () |
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Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
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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 C<ev_default_loop> for |
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a description of the set values. |
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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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assert (("sorry, no epoll, no sex", |
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ev_supported_backends () & EVBACKEND_EPOLL)); |
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=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 C<ev_supported_backends>, 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. |
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=item unsigned int ev_embeddable_backends () |
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Returns the set of backends that are embeddable in other event loops. This |
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is the theoretical, all-platform, value. To find which backends |
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might be supported on the current system, you would need to look at |
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C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
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recommended ones. |
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See the description of C<ev_embed> watchers for more info. |
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=item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
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Sets the allocation function to use (the prototype is similar to the |
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realloc C function, the semantics are identical). It is used to allocate |
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and free memory (no surprises here). If it returns zero when memory |
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needs to be allocated, the library might abort or take some potentially |
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destructive action. The default is your system realloc function. |
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You could override this function in high-availability programs to, say, |
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free some memory if it cannot allocate memory, to use a special allocator, |
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or even to sleep a while and retry until some memory is available. |
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Example: replace the libev allocator with one that waits a bit and then |
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retries: better than mine). |
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static void * |
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persistent_realloc (void *ptr, long size) |
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{ |
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for (;;) |
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{ |
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void *newptr = realloc (ptr, size); |
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if (newptr) |
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return newptr; |
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sleep (60); |
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} |
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} |
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... |
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ev_set_allocator (persistent_realloc); |
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=item ev_set_syserr_cb (void (*cb)(const char *msg)); |
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Set the callback function to call on a retryable syscall error (such |
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as failed select, poll, epoll_wait). The message is a printable string |
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indicating the system call or subsystem causing the problem. If this |
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callback is set, then libev will expect it to remedy the sitution, no |
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matter what, when it returns. That is, libev will generally retry the |
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requested operation, or, if the condition doesn't go away, do bad stuff |
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(such as abort). |
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Example: do the same thing as libev does internally: |
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static void |
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fatal_error (const char *msg) |
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{ |
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perror (msg); |
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abort (); |
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} |
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... |
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ev_set_syserr_cb (fatal_error); |
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1.1 |
=back |
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=head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
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An event loop is described by a C<struct ev_loop *>. The library knows two |
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types of such loops, the I<default> loop, which supports signals and child |
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events, and dynamically created loops which do not. |
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If you use threads, a common model is to run the default event loop |
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1.17 |
in your main thread (or in a separate thread) and for each thread you |
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1.7 |
create, you also create another event loop. Libev itself does no locking |
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whatsoever, so if you mix calls to the same event loop in different |
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threads, make sure you lock (this is usually a bad idea, though, even if |
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1.9 |
done correctly, because it's hideous and inefficient). |
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=over 4 |
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=item struct ev_loop *ev_default_loop (unsigned int flags) |
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This will initialise the default event loop if it hasn't been initialised |
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yet and return it. If the default loop could not be initialised, returns |
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false. If it already was initialised it simply returns it (and ignores the |
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flags. If that is troubling you, check C<ev_backend ()> afterwards). |
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If you don't know what event loop to use, use the one returned from this |
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function. |
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The flags argument can be used to specify special behaviour or specific |
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backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
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The following flags are supported: |
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=over 4 |
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=item C<EVFLAG_AUTO> |
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The default flags value. Use this if you have no clue (it's the right |
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thing, believe me). |
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=item C<EVFLAG_NOENV> |
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If this flag bit is ored into the flag value (or the program runs setuid |
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or setgid) then libev will I<not> look at the environment variable |
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C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
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override the flags completely if it is found in the environment. This is |
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useful to try out specific backends to test their performance, or to work |
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around bugs. |
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=item C<EVBACKEND_SELECT> (value 1, portable select backend) |
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This is your standard select(2) backend. Not I<completely> standard, as |
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libev tries to roll its own fd_set with no limits on the number of fds, |
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but if that fails, expect a fairly low limit on the number of fds when |
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using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
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the fastest backend for a low number of fds. |
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=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
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And this is your standard poll(2) backend. It's more complicated than |
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select, but handles sparse fds better and has no artificial limit on the |
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number of fds you can use (except it will slow down considerably with a |
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lot of inactive fds). It scales similarly to select, i.e. O(total_fds). |
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=item C<EVBACKEND_EPOLL> (value 4, Linux) |
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For few fds, this backend is a bit little slower than poll and select, |
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but it scales phenomenally better. While poll and select usually scale like |
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O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
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either O(1) or O(active_fds). |
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While stopping and starting an I/O watcher in the same iteration will |
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result in some caching, there is still a syscall per such incident |
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(because the fd could point to a different file description now), so its |
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best to avoid that. Also, dup()ed file descriptors might not work very |
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well if you register events for both fds. |
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1.32 |
Please note that epoll sometimes generates spurious notifications, so you |
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need to use non-blocking I/O or other means to avoid blocking when no data |
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(or space) is available. |
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=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
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1.29 |
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Kqueue deserves special mention, as at the time of this writing, it |
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was broken on all BSDs except NetBSD (usually it doesn't work with |
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anything but sockets and pipes, except on Darwin, where of course its |
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1.33 |
completely useless). For this reason its not being "autodetected" |
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unless you explicitly specify it explicitly in the flags (i.e. using |
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C<EVBACKEND_KQUEUE>). |
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1.29 |
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It scales in the same way as the epoll backend, but the interface to the |
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kernel is more efficient (which says nothing about its actual speed, of |
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course). While starting and stopping an I/O watcher does not cause an |
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extra syscall as with epoll, it still adds up to four event changes per |
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incident, so its best to avoid that. |
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1.31 |
=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
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1.29 |
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This is not implemented yet (and might never be). |
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=item C<EVBACKEND_PORT> (value 32, Solaris 10) |
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1.29 |
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This uses the Solaris 10 port mechanism. As with everything on Solaris, |
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it's really slow, but it still scales very well (O(active_fds)). |
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1.32 |
Please note that solaris ports can result in a lot of spurious |
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notifications, so you need to use non-blocking I/O or other means to avoid |
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blocking when no data (or space) is available. |
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1.31 |
=item C<EVBACKEND_ALL> |
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1.29 |
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Try all backends (even potentially broken ones that wouldn't be tried |
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with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
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1.31 |
C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
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=back |
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1.29 |
If one or more of these are ored into the flags value, then only these |
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backends will be tried (in the reverse order as given here). If none are |
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specified, most compiled-in backend will be tried, usually in reverse |
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order of their flag values :) |
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1.33 |
The most typical usage is like this: |
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if (!ev_default_loop (0)) |
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fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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Restrict libev to the select and poll backends, and do not allow |
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environment settings to be taken into account: |
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ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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Use whatever libev has to offer, but make sure that kqueue is used if |
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available (warning, breaks stuff, best use only with your own private |
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event loop and only if you know the OS supports your types of fds): |
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ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
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1.1 |
=item struct ev_loop *ev_loop_new (unsigned int flags) |
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Similar to C<ev_default_loop>, but always creates a new event loop that is |
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always distinct from the default loop. Unlike the default loop, it cannot |
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handle signal and child watchers, and attempts to do so will be greeted by |
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undefined behaviour (or a failed assertion if assertions are enabled). |
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1.34 |
Example: try to create a event loop that uses epoll and nothing else. |
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struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
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if (!epoller) |
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fatal ("no epoll found here, maybe it hides under your chair"); |
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1.1 |
=item ev_default_destroy () |
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Destroys the default loop again (frees all memory and kernel state |
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1.37 |
etc.). None of the active event watchers will be stopped in the normal |
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sense, so e.g. C<ev_is_active> might still return true. It is your |
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responsibility to either stop all watchers cleanly yoursef I<before> |
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calling this function, or cope with the fact afterwards (which is usually |
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the easiest thing, youc na just ignore the watchers and/or C<free ()> them |
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for example). |
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1.1 |
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=item ev_loop_destroy (loop) |
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Like C<ev_default_destroy>, but destroys an event loop created by an |
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earlier call to C<ev_loop_new>. |
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=item ev_default_fork () |
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This function reinitialises the kernel state for backends that have |
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one. Despite the name, you can call it anytime, but it makes most sense |
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after forking, in either the parent or child process (or both, but that |
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again makes little sense). |
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1.30 |
You I<must> call this function in the child process after forking if and |
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only if you want to use the event library in both processes. If you just |
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|
fork+exec, you don't have to call it. |
350 |
root |
1.1 |
|
351 |
root |
1.9 |
The function itself is quite fast and it's usually not a problem to call |
352 |
root |
1.1 |
it just in case after a fork. To make this easy, the function will fit in |
353 |
|
|
quite nicely into a call to C<pthread_atfork>: |
354 |
|
|
|
355 |
|
|
pthread_atfork (0, 0, ev_default_fork); |
356 |
|
|
|
357 |
root |
1.31 |
At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use |
358 |
|
|
without calling this function, so if you force one of those backends you |
359 |
|
|
do not need to care. |
360 |
|
|
|
361 |
root |
1.1 |
=item ev_loop_fork (loop) |
362 |
|
|
|
363 |
|
|
Like C<ev_default_fork>, but acts on an event loop created by |
364 |
|
|
C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
365 |
|
|
after fork, and how you do this is entirely your own problem. |
366 |
|
|
|
367 |
root |
1.31 |
=item unsigned int ev_backend (loop) |
368 |
root |
1.1 |
|
369 |
root |
1.31 |
Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
370 |
root |
1.1 |
use. |
371 |
|
|
|
372 |
root |
1.9 |
=item ev_tstamp ev_now (loop) |
373 |
root |
1.1 |
|
374 |
|
|
Returns the current "event loop time", which is the time the event loop |
375 |
root |
1.34 |
received events and started processing them. This timestamp does not |
376 |
|
|
change as long as callbacks are being processed, and this is also the base |
377 |
|
|
time used for relative timers. You can treat it as the timestamp of the |
378 |
|
|
event occuring (or more correctly, libev finding out about it). |
379 |
root |
1.1 |
|
380 |
|
|
=item ev_loop (loop, int flags) |
381 |
|
|
|
382 |
|
|
Finally, this is it, the event handler. This function usually is called |
383 |
|
|
after you initialised all your watchers and you want to start handling |
384 |
|
|
events. |
385 |
|
|
|
386 |
root |
1.33 |
If the flags argument is specified as C<0>, it will not return until |
387 |
|
|
either no event watchers are active anymore or C<ev_unloop> was called. |
388 |
root |
1.1 |
|
389 |
root |
1.34 |
Please note that an explicit C<ev_unloop> is usually better than |
390 |
|
|
relying on all watchers to be stopped when deciding when a program has |
391 |
|
|
finished (especially in interactive programs), but having a program that |
392 |
|
|
automatically loops as long as it has to and no longer by virtue of |
393 |
|
|
relying on its watchers stopping correctly is a thing of beauty. |
394 |
|
|
|
395 |
root |
1.1 |
A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
396 |
|
|
those events and any outstanding ones, but will not block your process in |
397 |
root |
1.9 |
case there are no events and will return after one iteration of the loop. |
398 |
root |
1.1 |
|
399 |
|
|
A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
400 |
|
|
neccessary) and will handle those and any outstanding ones. It will block |
401 |
root |
1.9 |
your process until at least one new event arrives, and will return after |
402 |
root |
1.33 |
one iteration of the loop. This is useful if you are waiting for some |
403 |
|
|
external event in conjunction with something not expressible using other |
404 |
|
|
libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
405 |
|
|
usually a better approach for this kind of thing. |
406 |
|
|
|
407 |
|
|
Here are the gory details of what C<ev_loop> does: |
408 |
|
|
|
409 |
|
|
* If there are no active watchers (reference count is zero), return. |
410 |
|
|
- Queue prepare watchers and then call all outstanding watchers. |
411 |
|
|
- If we have been forked, recreate the kernel state. |
412 |
|
|
- Update the kernel state with all outstanding changes. |
413 |
|
|
- Update the "event loop time". |
414 |
|
|
- Calculate for how long to block. |
415 |
|
|
- Block the process, waiting for any events. |
416 |
|
|
- Queue all outstanding I/O (fd) events. |
417 |
|
|
- Update the "event loop time" and do time jump handling. |
418 |
|
|
- Queue all outstanding timers. |
419 |
|
|
- Queue all outstanding periodics. |
420 |
|
|
- If no events are pending now, queue all idle watchers. |
421 |
|
|
- Queue all check watchers. |
422 |
|
|
- Call all queued watchers in reverse order (i.e. check watchers first). |
423 |
|
|
Signals and child watchers are implemented as I/O watchers, and will |
424 |
|
|
be handled here by queueing them when their watcher gets executed. |
425 |
|
|
- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
426 |
|
|
were used, return, otherwise continue with step *. |
427 |
root |
1.27 |
|
428 |
root |
1.34 |
Example: queue some jobs and then loop until no events are outsanding |
429 |
|
|
anymore. |
430 |
|
|
|
431 |
|
|
... queue jobs here, make sure they register event watchers as long |
432 |
|
|
... as they still have work to do (even an idle watcher will do..) |
433 |
|
|
ev_loop (my_loop, 0); |
434 |
|
|
... jobs done. yeah! |
435 |
|
|
|
436 |
root |
1.1 |
=item ev_unloop (loop, how) |
437 |
|
|
|
438 |
root |
1.9 |
Can be used to make a call to C<ev_loop> return early (but only after it |
439 |
|
|
has processed all outstanding events). The C<how> argument must be either |
440 |
root |
1.25 |
C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
441 |
root |
1.9 |
C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
442 |
root |
1.1 |
|
443 |
|
|
=item ev_ref (loop) |
444 |
|
|
|
445 |
|
|
=item ev_unref (loop) |
446 |
|
|
|
447 |
root |
1.9 |
Ref/unref can be used to add or remove a reference count on the event |
448 |
|
|
loop: Every watcher keeps one reference, and as long as the reference |
449 |
|
|
count is nonzero, C<ev_loop> will not return on its own. If you have |
450 |
|
|
a watcher you never unregister that should not keep C<ev_loop> from |
451 |
|
|
returning, ev_unref() after starting, and ev_ref() before stopping it. For |
452 |
|
|
example, libev itself uses this for its internal signal pipe: It is not |
453 |
|
|
visible to the libev user and should not keep C<ev_loop> from exiting if |
454 |
|
|
no event watchers registered by it are active. It is also an excellent |
455 |
|
|
way to do this for generic recurring timers or from within third-party |
456 |
|
|
libraries. Just remember to I<unref after start> and I<ref before stop>. |
457 |
root |
1.1 |
|
458 |
root |
1.34 |
Example: create a signal watcher, but keep it from keeping C<ev_loop> |
459 |
|
|
running when nothing else is active. |
460 |
|
|
|
461 |
|
|
struct dv_signal exitsig; |
462 |
|
|
ev_signal_init (&exitsig, sig_cb, SIGINT); |
463 |
|
|
ev_signal_start (myloop, &exitsig); |
464 |
|
|
evf_unref (myloop); |
465 |
|
|
|
466 |
|
|
Example: for some weird reason, unregister the above signal handler again. |
467 |
|
|
|
468 |
|
|
ev_ref (myloop); |
469 |
|
|
ev_signal_stop (myloop, &exitsig); |
470 |
|
|
|
471 |
root |
1.1 |
=back |
472 |
|
|
|
473 |
root |
1.42 |
|
474 |
root |
1.1 |
=head1 ANATOMY OF A WATCHER |
475 |
|
|
|
476 |
|
|
A watcher is a structure that you create and register to record your |
477 |
|
|
interest in some event. For instance, if you want to wait for STDIN to |
478 |
root |
1.10 |
become readable, you would create an C<ev_io> watcher for that: |
479 |
root |
1.1 |
|
480 |
|
|
static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
481 |
|
|
{ |
482 |
|
|
ev_io_stop (w); |
483 |
|
|
ev_unloop (loop, EVUNLOOP_ALL); |
484 |
|
|
} |
485 |
|
|
|
486 |
|
|
struct ev_loop *loop = ev_default_loop (0); |
487 |
|
|
struct ev_io stdin_watcher; |
488 |
|
|
ev_init (&stdin_watcher, my_cb); |
489 |
|
|
ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
490 |
|
|
ev_io_start (loop, &stdin_watcher); |
491 |
|
|
ev_loop (loop, 0); |
492 |
|
|
|
493 |
|
|
As you can see, you are responsible for allocating the memory for your |
494 |
|
|
watcher structures (and it is usually a bad idea to do this on the stack, |
495 |
|
|
although this can sometimes be quite valid). |
496 |
|
|
|
497 |
|
|
Each watcher structure must be initialised by a call to C<ev_init |
498 |
|
|
(watcher *, callback)>, which expects a callback to be provided. This |
499 |
|
|
callback gets invoked each time the event occurs (or, in the case of io |
500 |
|
|
watchers, each time the event loop detects that the file descriptor given |
501 |
|
|
is readable and/or writable). |
502 |
|
|
|
503 |
|
|
Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
504 |
|
|
with arguments specific to this watcher type. There is also a macro |
505 |
|
|
to combine initialisation and setting in one call: C<< ev_<type>_init |
506 |
|
|
(watcher *, callback, ...) >>. |
507 |
|
|
|
508 |
|
|
To make the watcher actually watch out for events, you have to start it |
509 |
|
|
with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
510 |
|
|
*) >>), and you can stop watching for events at any time by calling the |
511 |
|
|
corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
512 |
|
|
|
513 |
|
|
As long as your watcher is active (has been started but not stopped) you |
514 |
|
|
must not touch the values stored in it. Most specifically you must never |
515 |
root |
1.36 |
reinitialise it or call its C<set> macro. |
516 |
root |
1.1 |
|
517 |
|
|
Each and every callback receives the event loop pointer as first, the |
518 |
|
|
registered watcher structure as second, and a bitset of received events as |
519 |
|
|
third argument. |
520 |
|
|
|
521 |
root |
1.14 |
The received events usually include a single bit per event type received |
522 |
root |
1.1 |
(you can receive multiple events at the same time). The possible bit masks |
523 |
|
|
are: |
524 |
|
|
|
525 |
|
|
=over 4 |
526 |
|
|
|
527 |
root |
1.10 |
=item C<EV_READ> |
528 |
root |
1.1 |
|
529 |
root |
1.10 |
=item C<EV_WRITE> |
530 |
root |
1.1 |
|
531 |
root |
1.10 |
The file descriptor in the C<ev_io> watcher has become readable and/or |
532 |
root |
1.1 |
writable. |
533 |
|
|
|
534 |
root |
1.10 |
=item C<EV_TIMEOUT> |
535 |
root |
1.1 |
|
536 |
root |
1.10 |
The C<ev_timer> watcher has timed out. |
537 |
root |
1.1 |
|
538 |
root |
1.10 |
=item C<EV_PERIODIC> |
539 |
root |
1.1 |
|
540 |
root |
1.10 |
The C<ev_periodic> watcher has timed out. |
541 |
root |
1.1 |
|
542 |
root |
1.10 |
=item C<EV_SIGNAL> |
543 |
root |
1.1 |
|
544 |
root |
1.10 |
The signal specified in the C<ev_signal> watcher has been received by a thread. |
545 |
root |
1.1 |
|
546 |
root |
1.10 |
=item C<EV_CHILD> |
547 |
root |
1.1 |
|
548 |
root |
1.10 |
The pid specified in the C<ev_child> watcher has received a status change. |
549 |
root |
1.1 |
|
550 |
root |
1.10 |
=item C<EV_IDLE> |
551 |
root |
1.1 |
|
552 |
root |
1.10 |
The C<ev_idle> watcher has determined that you have nothing better to do. |
553 |
root |
1.1 |
|
554 |
root |
1.10 |
=item C<EV_PREPARE> |
555 |
root |
1.1 |
|
556 |
root |
1.10 |
=item C<EV_CHECK> |
557 |
root |
1.1 |
|
558 |
root |
1.10 |
All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
559 |
|
|
to gather new events, and all C<ev_check> watchers are invoked just after |
560 |
root |
1.1 |
C<ev_loop> has gathered them, but before it invokes any callbacks for any |
561 |
|
|
received events. Callbacks of both watcher types can start and stop as |
562 |
|
|
many watchers as they want, and all of them will be taken into account |
563 |
root |
1.10 |
(for example, a C<ev_prepare> watcher might start an idle watcher to keep |
564 |
root |
1.1 |
C<ev_loop> from blocking). |
565 |
|
|
|
566 |
root |
1.10 |
=item C<EV_ERROR> |
567 |
root |
1.1 |
|
568 |
|
|
An unspecified error has occured, the watcher has been stopped. This might |
569 |
|
|
happen because the watcher could not be properly started because libev |
570 |
|
|
ran out of memory, a file descriptor was found to be closed or any other |
571 |
|
|
problem. You best act on it by reporting the problem and somehow coping |
572 |
|
|
with the watcher being stopped. |
573 |
|
|
|
574 |
|
|
Libev will usually signal a few "dummy" events together with an error, |
575 |
|
|
for example it might indicate that a fd is readable or writable, and if |
576 |
|
|
your callbacks is well-written it can just attempt the operation and cope |
577 |
|
|
with the error from read() or write(). This will not work in multithreaded |
578 |
|
|
programs, though, so beware. |
579 |
|
|
|
580 |
|
|
=back |
581 |
|
|
|
582 |
root |
1.42 |
=head2 GENERIC WATCHER FUNCTIONS |
583 |
root |
1.36 |
|
584 |
|
|
In the following description, C<TYPE> stands for the watcher type, |
585 |
|
|
e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
586 |
|
|
|
587 |
|
|
=over 4 |
588 |
|
|
|
589 |
|
|
=item C<ev_init> (ev_TYPE *watcher, callback) |
590 |
|
|
|
591 |
|
|
This macro initialises the generic portion of a watcher. The contents |
592 |
|
|
of the watcher object can be arbitrary (so C<malloc> will do). Only |
593 |
|
|
the generic parts of the watcher are initialised, you I<need> to call |
594 |
|
|
the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
595 |
|
|
type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
596 |
|
|
which rolls both calls into one. |
597 |
|
|
|
598 |
|
|
You can reinitialise a watcher at any time as long as it has been stopped |
599 |
|
|
(or never started) and there are no pending events outstanding. |
600 |
|
|
|
601 |
root |
1.42 |
The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
602 |
root |
1.36 |
int revents)>. |
603 |
|
|
|
604 |
|
|
=item C<ev_TYPE_set> (ev_TYPE *, [args]) |
605 |
|
|
|
606 |
|
|
This macro initialises the type-specific parts of a watcher. You need to |
607 |
|
|
call C<ev_init> at least once before you call this macro, but you can |
608 |
|
|
call C<ev_TYPE_set> any number of times. You must not, however, call this |
609 |
|
|
macro on a watcher that is active (it can be pending, however, which is a |
610 |
|
|
difference to the C<ev_init> macro). |
611 |
|
|
|
612 |
|
|
Although some watcher types do not have type-specific arguments |
613 |
|
|
(e.g. C<ev_prepare>) you still need to call its C<set> macro. |
614 |
|
|
|
615 |
|
|
=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
616 |
|
|
|
617 |
|
|
This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
618 |
|
|
calls into a single call. This is the most convinient method to initialise |
619 |
|
|
a watcher. The same limitations apply, of course. |
620 |
|
|
|
621 |
|
|
=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
622 |
|
|
|
623 |
|
|
Starts (activates) the given watcher. Only active watchers will receive |
624 |
|
|
events. If the watcher is already active nothing will happen. |
625 |
|
|
|
626 |
|
|
=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
627 |
|
|
|
628 |
|
|
Stops the given watcher again (if active) and clears the pending |
629 |
|
|
status. It is possible that stopped watchers are pending (for example, |
630 |
|
|
non-repeating timers are being stopped when they become pending), but |
631 |
|
|
C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
632 |
|
|
you want to free or reuse the memory used by the watcher it is therefore a |
633 |
|
|
good idea to always call its C<ev_TYPE_stop> function. |
634 |
|
|
|
635 |
|
|
=item bool ev_is_active (ev_TYPE *watcher) |
636 |
|
|
|
637 |
|
|
Returns a true value iff the watcher is active (i.e. it has been started |
638 |
|
|
and not yet been stopped). As long as a watcher is active you must not modify |
639 |
|
|
it. |
640 |
|
|
|
641 |
|
|
=item bool ev_is_pending (ev_TYPE *watcher) |
642 |
|
|
|
643 |
|
|
Returns a true value iff the watcher is pending, (i.e. it has outstanding |
644 |
|
|
events but its callback has not yet been invoked). As long as a watcher |
645 |
|
|
is pending (but not active) you must not call an init function on it (but |
646 |
|
|
C<ev_TYPE_set> is safe) and you must make sure the watcher is available to |
647 |
|
|
libev (e.g. you cnanot C<free ()> it). |
648 |
|
|
|
649 |
|
|
=item callback = ev_cb (ev_TYPE *watcher) |
650 |
|
|
|
651 |
|
|
Returns the callback currently set on the watcher. |
652 |
|
|
|
653 |
|
|
=item ev_cb_set (ev_TYPE *watcher, callback) |
654 |
|
|
|
655 |
|
|
Change the callback. You can change the callback at virtually any time |
656 |
|
|
(modulo threads). |
657 |
|
|
|
658 |
|
|
=back |
659 |
|
|
|
660 |
|
|
|
661 |
root |
1.1 |
=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
662 |
|
|
|
663 |
|
|
Each watcher has, by default, a member C<void *data> that you can change |
664 |
root |
1.14 |
and read at any time, libev will completely ignore it. This can be used |
665 |
root |
1.1 |
to associate arbitrary data with your watcher. If you need more data and |
666 |
|
|
don't want to allocate memory and store a pointer to it in that data |
667 |
|
|
member, you can also "subclass" the watcher type and provide your own |
668 |
|
|
data: |
669 |
|
|
|
670 |
|
|
struct my_io |
671 |
|
|
{ |
672 |
|
|
struct ev_io io; |
673 |
|
|
int otherfd; |
674 |
|
|
void *somedata; |
675 |
|
|
struct whatever *mostinteresting; |
676 |
|
|
} |
677 |
|
|
|
678 |
|
|
And since your callback will be called with a pointer to the watcher, you |
679 |
|
|
can cast it back to your own type: |
680 |
|
|
|
681 |
|
|
static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
682 |
|
|
{ |
683 |
|
|
struct my_io *w = (struct my_io *)w_; |
684 |
|
|
... |
685 |
|
|
} |
686 |
|
|
|
687 |
|
|
More interesting and less C-conformant ways of catsing your callback type |
688 |
|
|
have been omitted.... |
689 |
|
|
|
690 |
|
|
|
691 |
|
|
=head1 WATCHER TYPES |
692 |
|
|
|
693 |
|
|
This section describes each watcher in detail, but will not repeat |
694 |
|
|
information given in the last section. |
695 |
|
|
|
696 |
root |
1.34 |
|
697 |
root |
1.42 |
=head2 C<ev_io> - is this file descriptor readable or writable? |
698 |
root |
1.1 |
|
699 |
root |
1.4 |
I/O watchers check whether a file descriptor is readable or writable |
700 |
root |
1.42 |
in each iteration of the event loop, or, more precisely, when reading |
701 |
|
|
would not block the process and writing would at least be able to write |
702 |
|
|
some data. This behaviour is called level-triggering because you keep |
703 |
|
|
receiving events as long as the condition persists. Remember you can stop |
704 |
|
|
the watcher if you don't want to act on the event and neither want to |
705 |
|
|
receive future events. |
706 |
root |
1.1 |
|
707 |
root |
1.23 |
In general you can register as many read and/or write event watchers per |
708 |
root |
1.8 |
fd as you want (as long as you don't confuse yourself). Setting all file |
709 |
|
|
descriptors to non-blocking mode is also usually a good idea (but not |
710 |
|
|
required if you know what you are doing). |
711 |
|
|
|
712 |
|
|
You have to be careful with dup'ed file descriptors, though. Some backends |
713 |
|
|
(the linux epoll backend is a notable example) cannot handle dup'ed file |
714 |
|
|
descriptors correctly if you register interest in two or more fds pointing |
715 |
root |
1.42 |
to the same underlying file/socket/etc. description (that is, they share |
716 |
root |
1.24 |
the same underlying "file open"). |
717 |
root |
1.8 |
|
718 |
|
|
If you must do this, then force the use of a known-to-be-good backend |
719 |
root |
1.31 |
(at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
720 |
|
|
C<EVBACKEND_POLL>). |
721 |
root |
1.8 |
|
722 |
root |
1.42 |
Another thing you have to watch out for is that it is quite easy to |
723 |
|
|
receive "spurious" readyness notifications, that is your callback might |
724 |
|
|
be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
725 |
|
|
because there is no data. Not only are some backends known to create a |
726 |
|
|
lot of those (for example solaris ports), it is very easy to get into |
727 |
|
|
this situation even with a relatively standard program structure. Thus |
728 |
|
|
it is best to always use non-blocking I/O: An extra C<read>(2) returning |
729 |
|
|
C<EAGAIN> is far preferable to a program hanging until some data arrives. |
730 |
|
|
|
731 |
|
|
If you cannot run the fd in non-blocking mode (for example you should not |
732 |
|
|
play around with an Xlib connection), then you have to seperately re-test |
733 |
|
|
wether a file descriptor is really ready with a known-to-be good interface |
734 |
|
|
such as poll (fortunately in our Xlib example, Xlib already does this on |
735 |
|
|
its own, so its quite safe to use). |
736 |
|
|
|
737 |
root |
1.1 |
=over 4 |
738 |
|
|
|
739 |
|
|
=item ev_io_init (ev_io *, callback, int fd, int events) |
740 |
|
|
|
741 |
|
|
=item ev_io_set (ev_io *, int fd, int events) |
742 |
|
|
|
743 |
root |
1.42 |
Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
744 |
|
|
rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or |
745 |
|
|
C<EV_READ | EV_WRITE> to receive the given events. |
746 |
root |
1.32 |
|
747 |
root |
1.1 |
=back |
748 |
|
|
|
749 |
root |
1.34 |
Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well |
750 |
|
|
readable, but only once. Since it is likely line-buffered, you could |
751 |
|
|
attempt to read a whole line in the callback: |
752 |
|
|
|
753 |
|
|
static void |
754 |
|
|
stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
755 |
|
|
{ |
756 |
|
|
ev_io_stop (loop, w); |
757 |
|
|
.. read from stdin here (or from w->fd) and haqndle any I/O errors |
758 |
|
|
} |
759 |
|
|
|
760 |
|
|
... |
761 |
|
|
struct ev_loop *loop = ev_default_init (0); |
762 |
|
|
struct ev_io stdin_readable; |
763 |
|
|
ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
764 |
|
|
ev_io_start (loop, &stdin_readable); |
765 |
|
|
ev_loop (loop, 0); |
766 |
|
|
|
767 |
|
|
|
768 |
root |
1.42 |
=head2 C<ev_timer> - relative and optionally repeating timeouts |
769 |
root |
1.1 |
|
770 |
|
|
Timer watchers are simple relative timers that generate an event after a |
771 |
|
|
given time, and optionally repeating in regular intervals after that. |
772 |
|
|
|
773 |
|
|
The timers are based on real time, that is, if you register an event that |
774 |
root |
1.22 |
times out after an hour and you reset your system clock to last years |
775 |
root |
1.1 |
time, it will still time out after (roughly) and hour. "Roughly" because |
776 |
root |
1.28 |
detecting time jumps is hard, and some inaccuracies are unavoidable (the |
777 |
root |
1.1 |
monotonic clock option helps a lot here). |
778 |
|
|
|
779 |
root |
1.9 |
The relative timeouts are calculated relative to the C<ev_now ()> |
780 |
|
|
time. This is usually the right thing as this timestamp refers to the time |
781 |
root |
1.28 |
of the event triggering whatever timeout you are modifying/starting. If |
782 |
|
|
you suspect event processing to be delayed and you I<need> to base the timeout |
783 |
root |
1.22 |
on the current time, use something like this to adjust for this: |
784 |
root |
1.9 |
|
785 |
|
|
ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
786 |
|
|
|
787 |
root |
1.28 |
The callback is guarenteed to be invoked only when its timeout has passed, |
788 |
|
|
but if multiple timers become ready during the same loop iteration then |
789 |
|
|
order of execution is undefined. |
790 |
|
|
|
791 |
root |
1.1 |
=over 4 |
792 |
|
|
|
793 |
|
|
=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
794 |
|
|
|
795 |
|
|
=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
796 |
|
|
|
797 |
|
|
Configure the timer to trigger after C<after> seconds. If C<repeat> is |
798 |
|
|
C<0.>, then it will automatically be stopped. If it is positive, then the |
799 |
|
|
timer will automatically be configured to trigger again C<repeat> seconds |
800 |
|
|
later, again, and again, until stopped manually. |
801 |
|
|
|
802 |
|
|
The timer itself will do a best-effort at avoiding drift, that is, if you |
803 |
|
|
configure a timer to trigger every 10 seconds, then it will trigger at |
804 |
|
|
exactly 10 second intervals. If, however, your program cannot keep up with |
805 |
root |
1.22 |
the timer (because it takes longer than those 10 seconds to do stuff) the |
806 |
root |
1.1 |
timer will not fire more than once per event loop iteration. |
807 |
|
|
|
808 |
|
|
=item ev_timer_again (loop) |
809 |
|
|
|
810 |
|
|
This will act as if the timer timed out and restart it again if it is |
811 |
|
|
repeating. The exact semantics are: |
812 |
|
|
|
813 |
|
|
If the timer is started but nonrepeating, stop it. |
814 |
|
|
|
815 |
|
|
If the timer is repeating, either start it if necessary (with the repeat |
816 |
|
|
value), or reset the running timer to the repeat value. |
817 |
|
|
|
818 |
|
|
This sounds a bit complicated, but here is a useful and typical |
819 |
|
|
example: Imagine you have a tcp connection and you want a so-called idle |
820 |
|
|
timeout, that is, you want to be called when there have been, say, 60 |
821 |
|
|
seconds of inactivity on the socket. The easiest way to do this is to |
822 |
root |
1.10 |
configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each |
823 |
root |
1.1 |
time you successfully read or write some data. If you go into an idle |
824 |
|
|
state where you do not expect data to travel on the socket, you can stop |
825 |
|
|
the timer, and again will automatically restart it if need be. |
826 |
|
|
|
827 |
|
|
=back |
828 |
|
|
|
829 |
root |
1.34 |
Example: create a timer that fires after 60 seconds. |
830 |
|
|
|
831 |
|
|
static void |
832 |
|
|
one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
833 |
|
|
{ |
834 |
|
|
.. one minute over, w is actually stopped right here |
835 |
|
|
} |
836 |
|
|
|
837 |
|
|
struct ev_timer mytimer; |
838 |
|
|
ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
839 |
|
|
ev_timer_start (loop, &mytimer); |
840 |
|
|
|
841 |
|
|
Example: create a timeout timer that times out after 10 seconds of |
842 |
|
|
inactivity. |
843 |
|
|
|
844 |
|
|
static void |
845 |
|
|
timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
846 |
|
|
{ |
847 |
|
|
.. ten seconds without any activity |
848 |
|
|
} |
849 |
|
|
|
850 |
|
|
struct ev_timer mytimer; |
851 |
|
|
ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
852 |
|
|
ev_timer_again (&mytimer); /* start timer */ |
853 |
|
|
ev_loop (loop, 0); |
854 |
|
|
|
855 |
|
|
// and in some piece of code that gets executed on any "activity": |
856 |
|
|
// reset the timeout to start ticking again at 10 seconds |
857 |
|
|
ev_timer_again (&mytimer); |
858 |
|
|
|
859 |
|
|
|
860 |
root |
1.42 |
=head2 C<ev_periodic> - to cron or not to cron? |
861 |
root |
1.1 |
|
862 |
|
|
Periodic watchers are also timers of a kind, but they are very versatile |
863 |
|
|
(and unfortunately a bit complex). |
864 |
|
|
|
865 |
root |
1.10 |
Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
866 |
root |
1.1 |
but on wallclock time (absolute time). You can tell a periodic watcher |
867 |
|
|
to trigger "at" some specific point in time. For example, if you tell a |
868 |
root |
1.38 |
periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
869 |
root |
1.1 |
+ 10.>) and then reset your system clock to the last year, then it will |
870 |
root |
1.10 |
take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
871 |
root |
1.1 |
roughly 10 seconds later and of course not if you reset your system time |
872 |
|
|
again). |
873 |
|
|
|
874 |
|
|
They can also be used to implement vastly more complex timers, such as |
875 |
|
|
triggering an event on eahc midnight, local time. |
876 |
|
|
|
877 |
root |
1.28 |
As with timers, the callback is guarenteed to be invoked only when the |
878 |
|
|
time (C<at>) has been passed, but if multiple periodic timers become ready |
879 |
|
|
during the same loop iteration then order of execution is undefined. |
880 |
|
|
|
881 |
root |
1.1 |
=over 4 |
882 |
|
|
|
883 |
|
|
=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
884 |
|
|
|
885 |
|
|
=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
886 |
|
|
|
887 |
|
|
Lots of arguments, lets sort it out... There are basically three modes of |
888 |
|
|
operation, and we will explain them from simplest to complex: |
889 |
|
|
|
890 |
|
|
=over 4 |
891 |
|
|
|
892 |
|
|
=item * absolute timer (interval = reschedule_cb = 0) |
893 |
|
|
|
894 |
|
|
In this configuration the watcher triggers an event at the wallclock time |
895 |
|
|
C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
896 |
|
|
that is, if it is to be run at January 1st 2011 then it will run when the |
897 |
|
|
system time reaches or surpasses this time. |
898 |
|
|
|
899 |
|
|
=item * non-repeating interval timer (interval > 0, reschedule_cb = 0) |
900 |
|
|
|
901 |
|
|
In this mode the watcher will always be scheduled to time out at the next |
902 |
|
|
C<at + N * interval> time (for some integer N) and then repeat, regardless |
903 |
|
|
of any time jumps. |
904 |
|
|
|
905 |
|
|
This can be used to create timers that do not drift with respect to system |
906 |
|
|
time: |
907 |
|
|
|
908 |
|
|
ev_periodic_set (&periodic, 0., 3600., 0); |
909 |
|
|
|
910 |
|
|
This doesn't mean there will always be 3600 seconds in between triggers, |
911 |
|
|
but only that the the callback will be called when the system time shows a |
912 |
root |
1.12 |
full hour (UTC), or more correctly, when the system time is evenly divisible |
913 |
root |
1.1 |
by 3600. |
914 |
|
|
|
915 |
|
|
Another way to think about it (for the mathematically inclined) is that |
916 |
root |
1.10 |
C<ev_periodic> will try to run the callback in this mode at the next possible |
917 |
root |
1.1 |
time where C<time = at (mod interval)>, regardless of any time jumps. |
918 |
|
|
|
919 |
|
|
=item * manual reschedule mode (reschedule_cb = callback) |
920 |
|
|
|
921 |
|
|
In this mode the values for C<interval> and C<at> are both being |
922 |
|
|
ignored. Instead, each time the periodic watcher gets scheduled, the |
923 |
|
|
reschedule callback will be called with the watcher as first, and the |
924 |
|
|
current time as second argument. |
925 |
|
|
|
926 |
root |
1.18 |
NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
927 |
|
|
ever, or make any event loop modifications>. If you need to stop it, |
928 |
|
|
return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
929 |
|
|
starting a prepare watcher). |
930 |
root |
1.1 |
|
931 |
root |
1.13 |
Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
932 |
root |
1.1 |
ev_tstamp now)>, e.g.: |
933 |
|
|
|
934 |
|
|
static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
935 |
|
|
{ |
936 |
|
|
return now + 60.; |
937 |
|
|
} |
938 |
|
|
|
939 |
|
|
It must return the next time to trigger, based on the passed time value |
940 |
|
|
(that is, the lowest time value larger than to the second argument). It |
941 |
|
|
will usually be called just before the callback will be triggered, but |
942 |
|
|
might be called at other times, too. |
943 |
|
|
|
944 |
root |
1.18 |
NOTE: I<< This callback must always return a time that is later than the |
945 |
root |
1.19 |
passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger. |
946 |
root |
1.18 |
|
947 |
root |
1.1 |
This can be used to create very complex timers, such as a timer that |
948 |
|
|
triggers on each midnight, local time. To do this, you would calculate the |
949 |
root |
1.19 |
next midnight after C<now> and return the timestamp value for this. How |
950 |
|
|
you do this is, again, up to you (but it is not trivial, which is the main |
951 |
|
|
reason I omitted it as an example). |
952 |
root |
1.1 |
|
953 |
|
|
=back |
954 |
|
|
|
955 |
|
|
=item ev_periodic_again (loop, ev_periodic *) |
956 |
|
|
|
957 |
|
|
Simply stops and restarts the periodic watcher again. This is only useful |
958 |
|
|
when you changed some parameters or the reschedule callback would return |
959 |
|
|
a different time than the last time it was called (e.g. in a crond like |
960 |
|
|
program when the crontabs have changed). |
961 |
|
|
|
962 |
|
|
=back |
963 |
|
|
|
964 |
root |
1.34 |
Example: call a callback every hour, or, more precisely, whenever the |
965 |
|
|
system clock is divisible by 3600. The callback invocation times have |
966 |
|
|
potentially a lot of jittering, but good long-term stability. |
967 |
|
|
|
968 |
|
|
static void |
969 |
|
|
clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
970 |
|
|
{ |
971 |
|
|
... its now a full hour (UTC, or TAI or whatever your clock follows) |
972 |
|
|
} |
973 |
|
|
|
974 |
|
|
struct ev_periodic hourly_tick; |
975 |
|
|
ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
976 |
|
|
ev_periodic_start (loop, &hourly_tick); |
977 |
|
|
|
978 |
|
|
Example: the same as above, but use a reschedule callback to do it: |
979 |
|
|
|
980 |
|
|
#include <math.h> |
981 |
|
|
|
982 |
|
|
static ev_tstamp |
983 |
|
|
my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
984 |
|
|
{ |
985 |
|
|
return fmod (now, 3600.) + 3600.; |
986 |
|
|
} |
987 |
|
|
|
988 |
|
|
ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
989 |
|
|
|
990 |
|
|
Example: call a callback every hour, starting now: |
991 |
|
|
|
992 |
|
|
struct ev_periodic hourly_tick; |
993 |
|
|
ev_periodic_init (&hourly_tick, clock_cb, |
994 |
|
|
fmod (ev_now (loop), 3600.), 3600., 0); |
995 |
|
|
ev_periodic_start (loop, &hourly_tick); |
996 |
|
|
|
997 |
|
|
|
998 |
root |
1.42 |
=head2 C<ev_signal> - signal me when a signal gets signalled! |
999 |
root |
1.1 |
|
1000 |
|
|
Signal watchers will trigger an event when the process receives a specific |
1001 |
|
|
signal one or more times. Even though signals are very asynchronous, libev |
1002 |
root |
1.9 |
will try it's best to deliver signals synchronously, i.e. as part of the |
1003 |
root |
1.1 |
normal event processing, like any other event. |
1004 |
|
|
|
1005 |
root |
1.14 |
You can configure as many watchers as you like per signal. Only when the |
1006 |
root |
1.1 |
first watcher gets started will libev actually register a signal watcher |
1007 |
|
|
with the kernel (thus it coexists with your own signal handlers as long |
1008 |
|
|
as you don't register any with libev). Similarly, when the last signal |
1009 |
|
|
watcher for a signal is stopped libev will reset the signal handler to |
1010 |
|
|
SIG_DFL (regardless of what it was set to before). |
1011 |
|
|
|
1012 |
|
|
=over 4 |
1013 |
|
|
|
1014 |
|
|
=item ev_signal_init (ev_signal *, callback, int signum) |
1015 |
|
|
|
1016 |
|
|
=item ev_signal_set (ev_signal *, int signum) |
1017 |
|
|
|
1018 |
|
|
Configures the watcher to trigger on the given signal number (usually one |
1019 |
|
|
of the C<SIGxxx> constants). |
1020 |
|
|
|
1021 |
|
|
=back |
1022 |
|
|
|
1023 |
root |
1.35 |
|
1024 |
root |
1.42 |
=head2 C<ev_child> - watch out for process status changes |
1025 |
root |
1.1 |
|
1026 |
|
|
Child watchers trigger when your process receives a SIGCHLD in response to |
1027 |
|
|
some child status changes (most typically when a child of yours dies). |
1028 |
|
|
|
1029 |
|
|
=over 4 |
1030 |
|
|
|
1031 |
|
|
=item ev_child_init (ev_child *, callback, int pid) |
1032 |
|
|
|
1033 |
|
|
=item ev_child_set (ev_child *, int pid) |
1034 |
|
|
|
1035 |
|
|
Configures the watcher to wait for status changes of process C<pid> (or |
1036 |
|
|
I<any> process if C<pid> is specified as C<0>). The callback can look |
1037 |
|
|
at the C<rstatus> member of the C<ev_child> watcher structure to see |
1038 |
root |
1.14 |
the status word (use the macros from C<sys/wait.h> and see your systems |
1039 |
|
|
C<waitpid> documentation). The C<rpid> member contains the pid of the |
1040 |
|
|
process causing the status change. |
1041 |
root |
1.1 |
|
1042 |
|
|
=back |
1043 |
|
|
|
1044 |
root |
1.34 |
Example: try to exit cleanly on SIGINT and SIGTERM. |
1045 |
|
|
|
1046 |
|
|
static void |
1047 |
|
|
sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1048 |
|
|
{ |
1049 |
|
|
ev_unloop (loop, EVUNLOOP_ALL); |
1050 |
|
|
} |
1051 |
|
|
|
1052 |
|
|
struct ev_signal signal_watcher; |
1053 |
|
|
ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1054 |
|
|
ev_signal_start (loop, &sigint_cb); |
1055 |
|
|
|
1056 |
|
|
|
1057 |
root |
1.42 |
=head2 C<ev_idle> - when you've got nothing better to do... |
1058 |
root |
1.1 |
|
1059 |
root |
1.14 |
Idle watchers trigger events when there are no other events are pending |
1060 |
|
|
(prepare, check and other idle watchers do not count). That is, as long |
1061 |
|
|
as your process is busy handling sockets or timeouts (or even signals, |
1062 |
|
|
imagine) it will not be triggered. But when your process is idle all idle |
1063 |
|
|
watchers are being called again and again, once per event loop iteration - |
1064 |
|
|
until stopped, that is, or your process receives more events and becomes |
1065 |
|
|
busy. |
1066 |
root |
1.1 |
|
1067 |
|
|
The most noteworthy effect is that as long as any idle watchers are |
1068 |
|
|
active, the process will not block when waiting for new events. |
1069 |
|
|
|
1070 |
|
|
Apart from keeping your process non-blocking (which is a useful |
1071 |
|
|
effect on its own sometimes), idle watchers are a good place to do |
1072 |
|
|
"pseudo-background processing", or delay processing stuff to after the |
1073 |
|
|
event loop has handled all outstanding events. |
1074 |
|
|
|
1075 |
|
|
=over 4 |
1076 |
|
|
|
1077 |
|
|
=item ev_idle_init (ev_signal *, callback) |
1078 |
|
|
|
1079 |
|
|
Initialises and configures the idle watcher - it has no parameters of any |
1080 |
|
|
kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1081 |
|
|
believe me. |
1082 |
|
|
|
1083 |
|
|
=back |
1084 |
|
|
|
1085 |
root |
1.34 |
Example: dynamically allocate an C<ev_idle>, start it, and in the |
1086 |
|
|
callback, free it. Alos, use no error checking, as usual. |
1087 |
|
|
|
1088 |
|
|
static void |
1089 |
|
|
idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
1090 |
|
|
{ |
1091 |
|
|
free (w); |
1092 |
|
|
// now do something you wanted to do when the program has |
1093 |
|
|
// no longer asnything immediate to do. |
1094 |
|
|
} |
1095 |
|
|
|
1096 |
|
|
struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
1097 |
|
|
ev_idle_init (idle_watcher, idle_cb); |
1098 |
|
|
ev_idle_start (loop, idle_cb); |
1099 |
|
|
|
1100 |
|
|
|
1101 |
root |
1.42 |
=head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1102 |
root |
1.1 |
|
1103 |
root |
1.14 |
Prepare and check watchers are usually (but not always) used in tandem: |
1104 |
root |
1.20 |
prepare watchers get invoked before the process blocks and check watchers |
1105 |
root |
1.14 |
afterwards. |
1106 |
root |
1.1 |
|
1107 |
root |
1.45 |
You I<must not> call C<ev_loop> or similar functions that enter |
1108 |
|
|
the current event loop from either C<ev_prepare> or C<ev_check> |
1109 |
|
|
watchers. Other loops than the current one are fine, however. The |
1110 |
|
|
rationale behind this is that you do not need to check for recursion in |
1111 |
|
|
those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
1112 |
|
|
C<ev_check> so if you have one watcher of each kind they will always be |
1113 |
|
|
called in pairs bracketing the blocking call. |
1114 |
|
|
|
1115 |
root |
1.35 |
Their main purpose is to integrate other event mechanisms into libev and |
1116 |
|
|
their use is somewhat advanced. This could be used, for example, to track |
1117 |
|
|
variable changes, implement your own watchers, integrate net-snmp or a |
1118 |
root |
1.45 |
coroutine library and lots more. They are also occasionally useful if |
1119 |
|
|
you cache some data and want to flush it before blocking (for example, |
1120 |
|
|
in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1121 |
|
|
watcher). |
1122 |
root |
1.1 |
|
1123 |
|
|
This is done by examining in each prepare call which file descriptors need |
1124 |
root |
1.14 |
to be watched by the other library, registering C<ev_io> watchers for |
1125 |
|
|
them and starting an C<ev_timer> watcher for any timeouts (many libraries |
1126 |
|
|
provide just this functionality). Then, in the check watcher you check for |
1127 |
|
|
any events that occured (by checking the pending status of all watchers |
1128 |
|
|
and stopping them) and call back into the library. The I/O and timer |
1129 |
root |
1.20 |
callbacks will never actually be called (but must be valid nevertheless, |
1130 |
root |
1.14 |
because you never know, you know?). |
1131 |
root |
1.1 |
|
1132 |
root |
1.14 |
As another example, the Perl Coro module uses these hooks to integrate |
1133 |
root |
1.1 |
coroutines into libev programs, by yielding to other active coroutines |
1134 |
|
|
during each prepare and only letting the process block if no coroutines |
1135 |
root |
1.20 |
are ready to run (it's actually more complicated: it only runs coroutines |
1136 |
|
|
with priority higher than or equal to the event loop and one coroutine |
1137 |
|
|
of lower priority, but only once, using idle watchers to keep the event |
1138 |
|
|
loop from blocking if lower-priority coroutines are active, thus mapping |
1139 |
|
|
low-priority coroutines to idle/background tasks). |
1140 |
root |
1.1 |
|
1141 |
|
|
=over 4 |
1142 |
|
|
|
1143 |
|
|
=item ev_prepare_init (ev_prepare *, callback) |
1144 |
|
|
|
1145 |
|
|
=item ev_check_init (ev_check *, callback) |
1146 |
|
|
|
1147 |
|
|
Initialises and configures the prepare or check watcher - they have no |
1148 |
|
|
parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1149 |
root |
1.14 |
macros, but using them is utterly, utterly and completely pointless. |
1150 |
root |
1.1 |
|
1151 |
|
|
=back |
1152 |
|
|
|
1153 |
root |
1.45 |
Example: To include a library such as adns, you would add IO watchers |
1154 |
|
|
and a timeout watcher in a prepare handler, as required by libadns, and |
1155 |
|
|
in a check watcher, destroy them and call into libadns. What follows is |
1156 |
|
|
pseudo-code only of course: |
1157 |
|
|
|
1158 |
|
|
static ev_io iow [nfd]; |
1159 |
|
|
static ev_timer tw; |
1160 |
|
|
|
1161 |
|
|
static void |
1162 |
|
|
io_cb (ev_loop *loop, ev_io *w, int revents) |
1163 |
|
|
{ |
1164 |
|
|
// set the relevant poll flags |
1165 |
root |
1.46 |
// could also call adns_processreadable etc. here |
1166 |
root |
1.45 |
struct pollfd *fd = (struct pollfd *)w->data; |
1167 |
|
|
if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
1168 |
|
|
if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
1169 |
|
|
} |
1170 |
|
|
|
1171 |
|
|
// create io watchers for each fd and a timer before blocking |
1172 |
|
|
static void |
1173 |
|
|
adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
1174 |
|
|
{ |
1175 |
|
|
int timeout = 3600000;truct pollfd fds [nfd]; |
1176 |
|
|
// actual code will need to loop here and realloc etc. |
1177 |
|
|
adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1178 |
|
|
|
1179 |
|
|
/* the callback is illegal, but won't be called as we stop during check */ |
1180 |
|
|
ev_timer_init (&tw, 0, timeout * 1e-3); |
1181 |
|
|
ev_timer_start (loop, &tw); |
1182 |
|
|
|
1183 |
|
|
// create on ev_io per pollfd |
1184 |
|
|
for (int i = 0; i < nfd; ++i) |
1185 |
|
|
{ |
1186 |
|
|
ev_io_init (iow + i, io_cb, fds [i].fd, |
1187 |
|
|
((fds [i].events & POLLIN ? EV_READ : 0) |
1188 |
|
|
| (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1189 |
|
|
|
1190 |
|
|
fds [i].revents = 0; |
1191 |
|
|
iow [i].data = fds + i; |
1192 |
|
|
ev_io_start (loop, iow + i); |
1193 |
|
|
} |
1194 |
|
|
} |
1195 |
|
|
|
1196 |
|
|
// stop all watchers after blocking |
1197 |
|
|
static void |
1198 |
|
|
adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1199 |
|
|
{ |
1200 |
|
|
ev_timer_stop (loop, &tw); |
1201 |
|
|
|
1202 |
|
|
for (int i = 0; i < nfd; ++i) |
1203 |
|
|
ev_io_stop (loop, iow + i); |
1204 |
|
|
|
1205 |
|
|
adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1206 |
|
|
} |
1207 |
root |
1.34 |
|
1208 |
|
|
|
1209 |
root |
1.42 |
=head2 C<ev_embed> - when one backend isn't enough... |
1210 |
root |
1.35 |
|
1211 |
|
|
This is a rather advanced watcher type that lets you embed one event loop |
1212 |
root |
1.36 |
into another (currently only C<ev_io> events are supported in the embedded |
1213 |
|
|
loop, other types of watchers might be handled in a delayed or incorrect |
1214 |
|
|
fashion and must not be used). |
1215 |
root |
1.35 |
|
1216 |
|
|
There are primarily two reasons you would want that: work around bugs and |
1217 |
|
|
prioritise I/O. |
1218 |
|
|
|
1219 |
|
|
As an example for a bug workaround, the kqueue backend might only support |
1220 |
|
|
sockets on some platform, so it is unusable as generic backend, but you |
1221 |
|
|
still want to make use of it because you have many sockets and it scales |
1222 |
|
|
so nicely. In this case, you would create a kqueue-based loop and embed it |
1223 |
|
|
into your default loop (which might use e.g. poll). Overall operation will |
1224 |
|
|
be a bit slower because first libev has to poll and then call kevent, but |
1225 |
|
|
at least you can use both at what they are best. |
1226 |
|
|
|
1227 |
|
|
As for prioritising I/O: rarely you have the case where some fds have |
1228 |
|
|
to be watched and handled very quickly (with low latency), and even |
1229 |
|
|
priorities and idle watchers might have too much overhead. In this case |
1230 |
|
|
you would put all the high priority stuff in one loop and all the rest in |
1231 |
|
|
a second one, and embed the second one in the first. |
1232 |
|
|
|
1233 |
root |
1.36 |
As long as the watcher is active, the callback will be invoked every time |
1234 |
|
|
there might be events pending in the embedded loop. The callback must then |
1235 |
|
|
call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
1236 |
|
|
their callbacks (you could also start an idle watcher to give the embedded |
1237 |
|
|
loop strictly lower priority for example). You can also set the callback |
1238 |
|
|
to C<0>, in which case the embed watcher will automatically execute the |
1239 |
|
|
embedded loop sweep. |
1240 |
|
|
|
1241 |
root |
1.35 |
As long as the watcher is started it will automatically handle events. The |
1242 |
|
|
callback will be invoked whenever some events have been handled. You can |
1243 |
|
|
set the callback to C<0> to avoid having to specify one if you are not |
1244 |
|
|
interested in that. |
1245 |
|
|
|
1246 |
|
|
Also, there have not currently been made special provisions for forking: |
1247 |
|
|
when you fork, you not only have to call C<ev_loop_fork> on both loops, |
1248 |
|
|
but you will also have to stop and restart any C<ev_embed> watchers |
1249 |
|
|
yourself. |
1250 |
|
|
|
1251 |
|
|
Unfortunately, not all backends are embeddable, only the ones returned by |
1252 |
|
|
C<ev_embeddable_backends> are, which, unfortunately, does not include any |
1253 |
|
|
portable one. |
1254 |
|
|
|
1255 |
|
|
So when you want to use this feature you will always have to be prepared |
1256 |
|
|
that you cannot get an embeddable loop. The recommended way to get around |
1257 |
|
|
this is to have a separate variables for your embeddable loop, try to |
1258 |
|
|
create it, and if that fails, use the normal loop for everything: |
1259 |
|
|
|
1260 |
|
|
struct ev_loop *loop_hi = ev_default_init (0); |
1261 |
|
|
struct ev_loop *loop_lo = 0; |
1262 |
|
|
struct ev_embed embed; |
1263 |
|
|
|
1264 |
|
|
// see if there is a chance of getting one that works |
1265 |
|
|
// (remember that a flags value of 0 means autodetection) |
1266 |
|
|
loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
1267 |
|
|
? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
1268 |
|
|
: 0; |
1269 |
|
|
|
1270 |
|
|
// if we got one, then embed it, otherwise default to loop_hi |
1271 |
|
|
if (loop_lo) |
1272 |
|
|
{ |
1273 |
|
|
ev_embed_init (&embed, 0, loop_lo); |
1274 |
|
|
ev_embed_start (loop_hi, &embed); |
1275 |
|
|
} |
1276 |
|
|
else |
1277 |
|
|
loop_lo = loop_hi; |
1278 |
|
|
|
1279 |
|
|
=over 4 |
1280 |
|
|
|
1281 |
root |
1.36 |
=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
1282 |
|
|
|
1283 |
|
|
=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
1284 |
|
|
|
1285 |
|
|
Configures the watcher to embed the given loop, which must be |
1286 |
|
|
embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
1287 |
|
|
invoked automatically, otherwise it is the responsibility of the callback |
1288 |
|
|
to invoke it (it will continue to be called until the sweep has been done, |
1289 |
|
|
if you do not want thta, you need to temporarily stop the embed watcher). |
1290 |
root |
1.35 |
|
1291 |
root |
1.36 |
=item ev_embed_sweep (loop, ev_embed *) |
1292 |
root |
1.35 |
|
1293 |
root |
1.36 |
Make a single, non-blocking sweep over the embedded loop. This works |
1294 |
|
|
similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
1295 |
|
|
apropriate way for embedded loops. |
1296 |
root |
1.35 |
|
1297 |
|
|
=back |
1298 |
|
|
|
1299 |
|
|
|
1300 |
root |
1.1 |
=head1 OTHER FUNCTIONS |
1301 |
|
|
|
1302 |
root |
1.14 |
There are some other functions of possible interest. Described. Here. Now. |
1303 |
root |
1.1 |
|
1304 |
|
|
=over 4 |
1305 |
|
|
|
1306 |
|
|
=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
1307 |
|
|
|
1308 |
|
|
This function combines a simple timer and an I/O watcher, calls your |
1309 |
|
|
callback on whichever event happens first and automatically stop both |
1310 |
|
|
watchers. This is useful if you want to wait for a single event on an fd |
1311 |
root |
1.22 |
or timeout without having to allocate/configure/start/stop/free one or |
1312 |
root |
1.1 |
more watchers yourself. |
1313 |
|
|
|
1314 |
root |
1.14 |
If C<fd> is less than 0, then no I/O watcher will be started and events |
1315 |
|
|
is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
1316 |
|
|
C<events> set will be craeted and started. |
1317 |
root |
1.1 |
|
1318 |
|
|
If C<timeout> is less than 0, then no timeout watcher will be |
1319 |
root |
1.14 |
started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
1320 |
|
|
repeat = 0) will be started. While C<0> is a valid timeout, it is of |
1321 |
|
|
dubious value. |
1322 |
|
|
|
1323 |
|
|
The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
1324 |
root |
1.21 |
passed an C<revents> set like normal event callbacks (a combination of |
1325 |
root |
1.14 |
C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
1326 |
|
|
value passed to C<ev_once>: |
1327 |
root |
1.1 |
|
1328 |
|
|
static void stdin_ready (int revents, void *arg) |
1329 |
|
|
{ |
1330 |
|
|
if (revents & EV_TIMEOUT) |
1331 |
root |
1.14 |
/* doh, nothing entered */; |
1332 |
root |
1.1 |
else if (revents & EV_READ) |
1333 |
root |
1.14 |
/* stdin might have data for us, joy! */; |
1334 |
root |
1.1 |
} |
1335 |
|
|
|
1336 |
root |
1.14 |
ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
1337 |
root |
1.1 |
|
1338 |
root |
1.36 |
=item ev_feed_event (ev_loop *, watcher *, int revents) |
1339 |
root |
1.1 |
|
1340 |
|
|
Feeds the given event set into the event loop, as if the specified event |
1341 |
root |
1.14 |
had happened for the specified watcher (which must be a pointer to an |
1342 |
|
|
initialised but not necessarily started event watcher). |
1343 |
root |
1.1 |
|
1344 |
root |
1.36 |
=item ev_feed_fd_event (ev_loop *, int fd, int revents) |
1345 |
root |
1.1 |
|
1346 |
root |
1.14 |
Feed an event on the given fd, as if a file descriptor backend detected |
1347 |
|
|
the given events it. |
1348 |
root |
1.1 |
|
1349 |
root |
1.36 |
=item ev_feed_signal_event (ev_loop *loop, int signum) |
1350 |
root |
1.1 |
|
1351 |
root |
1.36 |
Feed an event as if the given signal occured (C<loop> must be the default |
1352 |
|
|
loop!). |
1353 |
root |
1.1 |
|
1354 |
|
|
=back |
1355 |
|
|
|
1356 |
root |
1.34 |
|
1357 |
root |
1.20 |
=head1 LIBEVENT EMULATION |
1358 |
|
|
|
1359 |
root |
1.24 |
Libev offers a compatibility emulation layer for libevent. It cannot |
1360 |
|
|
emulate the internals of libevent, so here are some usage hints: |
1361 |
|
|
|
1362 |
|
|
=over 4 |
1363 |
|
|
|
1364 |
|
|
=item * Use it by including <event.h>, as usual. |
1365 |
|
|
|
1366 |
|
|
=item * The following members are fully supported: ev_base, ev_callback, |
1367 |
|
|
ev_arg, ev_fd, ev_res, ev_events. |
1368 |
|
|
|
1369 |
|
|
=item * Avoid using ev_flags and the EVLIST_*-macros, while it is |
1370 |
|
|
maintained by libev, it does not work exactly the same way as in libevent (consider |
1371 |
|
|
it a private API). |
1372 |
|
|
|
1373 |
|
|
=item * Priorities are not currently supported. Initialising priorities |
1374 |
|
|
will fail and all watchers will have the same priority, even though there |
1375 |
|
|
is an ev_pri field. |
1376 |
|
|
|
1377 |
|
|
=item * Other members are not supported. |
1378 |
|
|
|
1379 |
|
|
=item * The libev emulation is I<not> ABI compatible to libevent, you need |
1380 |
|
|
to use the libev header file and library. |
1381 |
|
|
|
1382 |
|
|
=back |
1383 |
root |
1.20 |
|
1384 |
|
|
=head1 C++ SUPPORT |
1385 |
|
|
|
1386 |
root |
1.38 |
Libev comes with some simplistic wrapper classes for C++ that mainly allow |
1387 |
|
|
you to use some convinience methods to start/stop watchers and also change |
1388 |
|
|
the callback model to a model using method callbacks on objects. |
1389 |
|
|
|
1390 |
|
|
To use it, |
1391 |
|
|
|
1392 |
|
|
#include <ev++.h> |
1393 |
|
|
|
1394 |
|
|
(it is not installed by default). This automatically includes F<ev.h> |
1395 |
|
|
and puts all of its definitions (many of them macros) into the global |
1396 |
|
|
namespace. All C++ specific things are put into the C<ev> namespace. |
1397 |
|
|
|
1398 |
|
|
It should support all the same embedding options as F<ev.h>, most notably |
1399 |
|
|
C<EV_MULTIPLICITY>. |
1400 |
|
|
|
1401 |
|
|
Here is a list of things available in the C<ev> namespace: |
1402 |
|
|
|
1403 |
|
|
=over 4 |
1404 |
|
|
|
1405 |
|
|
=item C<ev::READ>, C<ev::WRITE> etc. |
1406 |
|
|
|
1407 |
|
|
These are just enum values with the same values as the C<EV_READ> etc. |
1408 |
|
|
macros from F<ev.h>. |
1409 |
|
|
|
1410 |
|
|
=item C<ev::tstamp>, C<ev::now> |
1411 |
|
|
|
1412 |
|
|
Aliases to the same types/functions as with the C<ev_> prefix. |
1413 |
|
|
|
1414 |
|
|
=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
1415 |
|
|
|
1416 |
|
|
For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
1417 |
|
|
the same name in the C<ev> namespace, with the exception of C<ev_signal> |
1418 |
|
|
which is called C<ev::sig> to avoid clashes with the C<signal> macro |
1419 |
|
|
defines by many implementations. |
1420 |
|
|
|
1421 |
|
|
All of those classes have these methods: |
1422 |
|
|
|
1423 |
|
|
=over 4 |
1424 |
|
|
|
1425 |
|
|
=item ev::TYPE::TYPE (object *, object::method *) |
1426 |
|
|
|
1427 |
|
|
=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *) |
1428 |
|
|
|
1429 |
|
|
=item ev::TYPE::~TYPE |
1430 |
|
|
|
1431 |
|
|
The constructor takes a pointer to an object and a method pointer to |
1432 |
|
|
the event handler callback to call in this class. The constructor calls |
1433 |
|
|
C<ev_init> for you, which means you have to call the C<set> method |
1434 |
|
|
before starting it. If you do not specify a loop then the constructor |
1435 |
|
|
automatically associates the default loop with this watcher. |
1436 |
|
|
|
1437 |
|
|
The destructor automatically stops the watcher if it is active. |
1438 |
|
|
|
1439 |
|
|
=item w->set (struct ev_loop *) |
1440 |
|
|
|
1441 |
|
|
Associates a different C<struct ev_loop> with this watcher. You can only |
1442 |
|
|
do this when the watcher is inactive (and not pending either). |
1443 |
|
|
|
1444 |
|
|
=item w->set ([args]) |
1445 |
|
|
|
1446 |
|
|
Basically the same as C<ev_TYPE_set>, with the same args. Must be |
1447 |
|
|
called at least once. Unlike the C counterpart, an active watcher gets |
1448 |
|
|
automatically stopped and restarted. |
1449 |
|
|
|
1450 |
|
|
=item w->start () |
1451 |
|
|
|
1452 |
|
|
Starts the watcher. Note that there is no C<loop> argument as the |
1453 |
|
|
constructor already takes the loop. |
1454 |
|
|
|
1455 |
|
|
=item w->stop () |
1456 |
|
|
|
1457 |
|
|
Stops the watcher if it is active. Again, no C<loop> argument. |
1458 |
|
|
|
1459 |
|
|
=item w->again () C<ev::timer>, C<ev::periodic> only |
1460 |
|
|
|
1461 |
|
|
For C<ev::timer> and C<ev::periodic>, this invokes the corresponding |
1462 |
|
|
C<ev_TYPE_again> function. |
1463 |
|
|
|
1464 |
|
|
=item w->sweep () C<ev::embed> only |
1465 |
|
|
|
1466 |
|
|
Invokes C<ev_embed_sweep>. |
1467 |
|
|
|
1468 |
|
|
=back |
1469 |
|
|
|
1470 |
|
|
=back |
1471 |
|
|
|
1472 |
|
|
Example: Define a class with an IO and idle watcher, start one of them in |
1473 |
|
|
the constructor. |
1474 |
|
|
|
1475 |
|
|
class myclass |
1476 |
|
|
{ |
1477 |
|
|
ev_io io; void io_cb (ev::io &w, int revents); |
1478 |
|
|
ev_idle idle void idle_cb (ev::idle &w, int revents); |
1479 |
|
|
|
1480 |
|
|
myclass (); |
1481 |
|
|
} |
1482 |
|
|
|
1483 |
|
|
myclass::myclass (int fd) |
1484 |
|
|
: io (this, &myclass::io_cb), |
1485 |
|
|
idle (this, &myclass::idle_cb) |
1486 |
|
|
{ |
1487 |
|
|
io.start (fd, ev::READ); |
1488 |
|
|
} |
1489 |
root |
1.20 |
|
1490 |
root |
1.39 |
=head1 EMBEDDING |
1491 |
|
|
|
1492 |
|
|
Libev can (and often is) directly embedded into host |
1493 |
|
|
applications. Examples of applications that embed it include the Deliantra |
1494 |
|
|
Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) |
1495 |
|
|
and rxvt-unicode. |
1496 |
|
|
|
1497 |
|
|
The goal is to enable you to just copy the neecssary files into your |
1498 |
|
|
source directory without having to change even a single line in them, so |
1499 |
|
|
you can easily upgrade by simply copying (or having a checked-out copy of |
1500 |
|
|
libev somewhere in your source tree). |
1501 |
|
|
|
1502 |
|
|
=head2 FILESETS |
1503 |
|
|
|
1504 |
|
|
Depending on what features you need you need to include one or more sets of files |
1505 |
|
|
in your app. |
1506 |
|
|
|
1507 |
|
|
=head3 CORE EVENT LOOP |
1508 |
|
|
|
1509 |
|
|
To include only the libev core (all the C<ev_*> functions), with manual |
1510 |
|
|
configuration (no autoconf): |
1511 |
|
|
|
1512 |
|
|
#define EV_STANDALONE 1 |
1513 |
|
|
#include "ev.c" |
1514 |
|
|
|
1515 |
|
|
This will automatically include F<ev.h>, too, and should be done in a |
1516 |
|
|
single C source file only to provide the function implementations. To use |
1517 |
|
|
it, do the same for F<ev.h> in all files wishing to use this API (best |
1518 |
|
|
done by writing a wrapper around F<ev.h> that you can include instead and |
1519 |
|
|
where you can put other configuration options): |
1520 |
|
|
|
1521 |
|
|
#define EV_STANDALONE 1 |
1522 |
|
|
#include "ev.h" |
1523 |
|
|
|
1524 |
|
|
Both header files and implementation files can be compiled with a C++ |
1525 |
|
|
compiler (at least, thats a stated goal, and breakage will be treated |
1526 |
|
|
as a bug). |
1527 |
|
|
|
1528 |
|
|
You need the following files in your source tree, or in a directory |
1529 |
|
|
in your include path (e.g. in libev/ when using -Ilibev): |
1530 |
|
|
|
1531 |
|
|
ev.h |
1532 |
|
|
ev.c |
1533 |
|
|
ev_vars.h |
1534 |
|
|
ev_wrap.h |
1535 |
|
|
|
1536 |
|
|
ev_win32.c required on win32 platforms only |
1537 |
|
|
|
1538 |
root |
1.43 |
ev_select.c only when select backend is enabled (which is by default) |
1539 |
root |
1.39 |
ev_poll.c only when poll backend is enabled (disabled by default) |
1540 |
|
|
ev_epoll.c only when the epoll backend is enabled (disabled by default) |
1541 |
|
|
ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
1542 |
|
|
ev_port.c only when the solaris port backend is enabled (disabled by default) |
1543 |
|
|
|
1544 |
|
|
F<ev.c> includes the backend files directly when enabled, so you only need |
1545 |
root |
1.43 |
to compile this single file. |
1546 |
root |
1.39 |
|
1547 |
|
|
=head3 LIBEVENT COMPATIBILITY API |
1548 |
|
|
|
1549 |
|
|
To include the libevent compatibility API, also include: |
1550 |
|
|
|
1551 |
|
|
#include "event.c" |
1552 |
|
|
|
1553 |
|
|
in the file including F<ev.c>, and: |
1554 |
|
|
|
1555 |
|
|
#include "event.h" |
1556 |
|
|
|
1557 |
|
|
in the files that want to use the libevent API. This also includes F<ev.h>. |
1558 |
|
|
|
1559 |
|
|
You need the following additional files for this: |
1560 |
|
|
|
1561 |
|
|
event.h |
1562 |
|
|
event.c |
1563 |
|
|
|
1564 |
|
|
=head3 AUTOCONF SUPPORT |
1565 |
|
|
|
1566 |
|
|
Instead of using C<EV_STANDALONE=1> and providing your config in |
1567 |
|
|
whatever way you want, you can also C<m4_include([libev.m4])> in your |
1568 |
root |
1.43 |
F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
1569 |
|
|
include F<config.h> and configure itself accordingly. |
1570 |
root |
1.39 |
|
1571 |
|
|
For this of course you need the m4 file: |
1572 |
|
|
|
1573 |
|
|
libev.m4 |
1574 |
|
|
|
1575 |
|
|
=head2 PREPROCESSOR SYMBOLS/MACROS |
1576 |
|
|
|
1577 |
|
|
Libev can be configured via a variety of preprocessor symbols you have to define |
1578 |
|
|
before including any of its files. The default is not to build for multiplicity |
1579 |
|
|
and only include the select backend. |
1580 |
|
|
|
1581 |
|
|
=over 4 |
1582 |
|
|
|
1583 |
|
|
=item EV_STANDALONE |
1584 |
|
|
|
1585 |
|
|
Must always be C<1> if you do not use autoconf configuration, which |
1586 |
|
|
keeps libev from including F<config.h>, and it also defines dummy |
1587 |
|
|
implementations for some libevent functions (such as logging, which is not |
1588 |
|
|
supported). It will also not define any of the structs usually found in |
1589 |
|
|
F<event.h> that are not directly supported by the libev core alone. |
1590 |
|
|
|
1591 |
|
|
=item EV_USE_MONOTONIC |
1592 |
|
|
|
1593 |
|
|
If defined to be C<1>, libev will try to detect the availability of the |
1594 |
|
|
monotonic clock option at both compiletime and runtime. Otherwise no use |
1595 |
|
|
of the monotonic clock option will be attempted. If you enable this, you |
1596 |
|
|
usually have to link against librt or something similar. Enabling it when |
1597 |
|
|
the functionality isn't available is safe, though, althoguh you have |
1598 |
|
|
to make sure you link against any libraries where the C<clock_gettime> |
1599 |
|
|
function is hiding in (often F<-lrt>). |
1600 |
|
|
|
1601 |
|
|
=item EV_USE_REALTIME |
1602 |
|
|
|
1603 |
|
|
If defined to be C<1>, libev will try to detect the availability of the |
1604 |
|
|
realtime clock option at compiletime (and assume its availability at |
1605 |
|
|
runtime if successful). Otherwise no use of the realtime clock option will |
1606 |
|
|
be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
1607 |
|
|
(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries |
1608 |
|
|
in the description of C<EV_USE_MONOTONIC>, though. |
1609 |
|
|
|
1610 |
|
|
=item EV_USE_SELECT |
1611 |
|
|
|
1612 |
|
|
If undefined or defined to be C<1>, libev will compile in support for the |
1613 |
|
|
C<select>(2) backend. No attempt at autodetection will be done: if no |
1614 |
|
|
other method takes over, select will be it. Otherwise the select backend |
1615 |
|
|
will not be compiled in. |
1616 |
|
|
|
1617 |
|
|
=item EV_SELECT_USE_FD_SET |
1618 |
|
|
|
1619 |
|
|
If defined to C<1>, then the select backend will use the system C<fd_set> |
1620 |
|
|
structure. This is useful if libev doesn't compile due to a missing |
1621 |
|
|
C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on |
1622 |
|
|
exotic systems. This usually limits the range of file descriptors to some |
1623 |
|
|
low limit such as 1024 or might have other limitations (winsocket only |
1624 |
|
|
allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
1625 |
|
|
influence the size of the C<fd_set> used. |
1626 |
|
|
|
1627 |
|
|
=item EV_SELECT_IS_WINSOCKET |
1628 |
|
|
|
1629 |
|
|
When defined to C<1>, the select backend will assume that |
1630 |
|
|
select/socket/connect etc. don't understand file descriptors but |
1631 |
|
|
wants osf handles on win32 (this is the case when the select to |
1632 |
|
|
be used is the winsock select). This means that it will call |
1633 |
|
|
C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
1634 |
|
|
it is assumed that all these functions actually work on fds, even |
1635 |
|
|
on win32. Should not be defined on non-win32 platforms. |
1636 |
|
|
|
1637 |
|
|
=item EV_USE_POLL |
1638 |
|
|
|
1639 |
|
|
If defined to be C<1>, libev will compile in support for the C<poll>(2) |
1640 |
|
|
backend. Otherwise it will be enabled on non-win32 platforms. It |
1641 |
|
|
takes precedence over select. |
1642 |
|
|
|
1643 |
|
|
=item EV_USE_EPOLL |
1644 |
|
|
|
1645 |
|
|
If defined to be C<1>, libev will compile in support for the Linux |
1646 |
|
|
C<epoll>(7) backend. Its availability will be detected at runtime, |
1647 |
|
|
otherwise another method will be used as fallback. This is the |
1648 |
|
|
preferred backend for GNU/Linux systems. |
1649 |
|
|
|
1650 |
|
|
=item EV_USE_KQUEUE |
1651 |
|
|
|
1652 |
|
|
If defined to be C<1>, libev will compile in support for the BSD style |
1653 |
|
|
C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
1654 |
|
|
otherwise another method will be used as fallback. This is the preferred |
1655 |
|
|
backend for BSD and BSD-like systems, although on most BSDs kqueue only |
1656 |
|
|
supports some types of fds correctly (the only platform we found that |
1657 |
|
|
supports ptys for example was NetBSD), so kqueue might be compiled in, but |
1658 |
|
|
not be used unless explicitly requested. The best way to use it is to find |
1659 |
root |
1.41 |
out whether kqueue supports your type of fd properly and use an embedded |
1660 |
root |
1.39 |
kqueue loop. |
1661 |
|
|
|
1662 |
|
|
=item EV_USE_PORT |
1663 |
|
|
|
1664 |
|
|
If defined to be C<1>, libev will compile in support for the Solaris |
1665 |
|
|
10 port style backend. Its availability will be detected at runtime, |
1666 |
|
|
otherwise another method will be used as fallback. This is the preferred |
1667 |
|
|
backend for Solaris 10 systems. |
1668 |
|
|
|
1669 |
|
|
=item EV_USE_DEVPOLL |
1670 |
|
|
|
1671 |
|
|
reserved for future expansion, works like the USE symbols above. |
1672 |
|
|
|
1673 |
|
|
=item EV_H |
1674 |
|
|
|
1675 |
|
|
The name of the F<ev.h> header file used to include it. The default if |
1676 |
|
|
undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This |
1677 |
|
|
can be used to virtually rename the F<ev.h> header file in case of conflicts. |
1678 |
|
|
|
1679 |
|
|
=item EV_CONFIG_H |
1680 |
|
|
|
1681 |
|
|
If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
1682 |
|
|
F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
1683 |
|
|
C<EV_H>, above. |
1684 |
|
|
|
1685 |
|
|
=item EV_EVENT_H |
1686 |
|
|
|
1687 |
|
|
Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
1688 |
|
|
of how the F<event.h> header can be found. |
1689 |
|
|
|
1690 |
|
|
=item EV_PROTOTYPES |
1691 |
|
|
|
1692 |
|
|
If defined to be C<0>, then F<ev.h> will not define any function |
1693 |
|
|
prototypes, but still define all the structs and other symbols. This is |
1694 |
|
|
occasionally useful if you want to provide your own wrapper functions |
1695 |
|
|
around libev functions. |
1696 |
|
|
|
1697 |
|
|
=item EV_MULTIPLICITY |
1698 |
|
|
|
1699 |
|
|
If undefined or defined to C<1>, then all event-loop-specific functions |
1700 |
|
|
will have the C<struct ev_loop *> as first argument, and you can create |
1701 |
|
|
additional independent event loops. Otherwise there will be no support |
1702 |
|
|
for multiple event loops and there is no first event loop pointer |
1703 |
|
|
argument. Instead, all functions act on the single default loop. |
1704 |
|
|
|
1705 |
|
|
=item EV_PERIODICS |
1706 |
|
|
|
1707 |
|
|
If undefined or defined to be C<1>, then periodic timers are supported, |
1708 |
|
|
otherwise not. This saves a few kb of code. |
1709 |
|
|
|
1710 |
|
|
=item EV_COMMON |
1711 |
|
|
|
1712 |
|
|
By default, all watchers have a C<void *data> member. By redefining |
1713 |
|
|
this macro to a something else you can include more and other types of |
1714 |
|
|
members. You have to define it each time you include one of the files, |
1715 |
|
|
though, and it must be identical each time. |
1716 |
|
|
|
1717 |
|
|
For example, the perl EV module uses something like this: |
1718 |
|
|
|
1719 |
|
|
#define EV_COMMON \ |
1720 |
|
|
SV *self; /* contains this struct */ \ |
1721 |
|
|
SV *cb_sv, *fh /* note no trailing ";" */ |
1722 |
|
|
|
1723 |
root |
1.44 |
=item EV_CB_DECLARE (type) |
1724 |
root |
1.39 |
|
1725 |
root |
1.44 |
=item EV_CB_INVOKE (watcher, revents) |
1726 |
root |
1.39 |
|
1727 |
root |
1.44 |
=item ev_set_cb (ev, cb) |
1728 |
root |
1.39 |
|
1729 |
|
|
Can be used to change the callback member declaration in each watcher, |
1730 |
|
|
and the way callbacks are invoked and set. Must expand to a struct member |
1731 |
|
|
definition and a statement, respectively. See the F<ev.v> header file for |
1732 |
|
|
their default definitions. One possible use for overriding these is to |
1733 |
root |
1.44 |
avoid the C<struct ev_loop *> as first argument in all cases, or to use |
1734 |
|
|
method calls instead of plain function calls in C++. |
1735 |
root |
1.39 |
|
1736 |
|
|
=head2 EXAMPLES |
1737 |
|
|
|
1738 |
|
|
For a real-world example of a program the includes libev |
1739 |
|
|
verbatim, you can have a look at the EV perl module |
1740 |
|
|
(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in |
1741 |
|
|
the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public |
1742 |
|
|
interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file |
1743 |
|
|
will be compiled. It is pretty complex because it provides its own header |
1744 |
|
|
file. |
1745 |
|
|
|
1746 |
|
|
The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
1747 |
|
|
that everybody includes and which overrides some autoconf choices: |
1748 |
|
|
|
1749 |
root |
1.40 |
#define EV_USE_POLL 0 |
1750 |
|
|
#define EV_MULTIPLICITY 0 |
1751 |
|
|
#define EV_PERIODICS 0 |
1752 |
|
|
#define EV_CONFIG_H <config.h> |
1753 |
root |
1.39 |
|
1754 |
root |
1.40 |
#include "ev++.h" |
1755 |
root |
1.39 |
|
1756 |
|
|
And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
1757 |
|
|
|
1758 |
root |
1.40 |
#include "ev_cpp.h" |
1759 |
|
|
#include "ev.c" |
1760 |
root |
1.39 |
|
1761 |
root |
1.46 |
|
1762 |
|
|
=head1 COMPLEXITIES |
1763 |
|
|
|
1764 |
|
|
In this section the complexities of (many of) the algorithms used inside |
1765 |
|
|
libev will be explained. For complexity discussions about backends see the |
1766 |
|
|
documentation for C<ev_default_init>. |
1767 |
|
|
|
1768 |
|
|
=over 4 |
1769 |
|
|
|
1770 |
|
|
=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
1771 |
|
|
|
1772 |
|
|
=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) |
1773 |
|
|
|
1774 |
|
|
=item Starting io/check/prepare/idle/signal/child watchers: O(1) |
1775 |
|
|
|
1776 |
|
|
=item Stopping check/prepare/idle watchers: O(1) |
1777 |
|
|
|
1778 |
|
|
=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16)) |
1779 |
|
|
|
1780 |
|
|
=item Finding the next timer per loop iteration: O(1) |
1781 |
|
|
|
1782 |
|
|
=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
1783 |
|
|
|
1784 |
|
|
=item Activating one watcher: O(1) |
1785 |
|
|
|
1786 |
|
|
=back |
1787 |
|
|
|
1788 |
|
|
|
1789 |
root |
1.1 |
=head1 AUTHOR |
1790 |
|
|
|
1791 |
|
|
Marc Lehmann <libev@schmorp.de>. |
1792 |
|
|
|