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libev is a high-performance event loop/event model with lots of features.
(see benchmark at http://libev.schmorp.de/bench.html)
- Homepage: http://software.schmorp.de/pkg/libev
- E-Mail: libev@lists.schmorp.de
- Library Documentation: http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod
-
- It is modelled (very losely) after libevent and the Event perl module,
- but aims to be faster and more correct, and also more featureful. And
- also smaller. Yay.
-ABOUT THIS DISTRIBUTION
+ABOUT
- If you downloaded the libevent+libev distribution of libev, you will
- find it looks very much like libevent. In fact, the distributed libev
- tarballs are indeed libevent tarballs patched up with the libev
- event core, taking the evbuffer, evtag, evdns and evhttpd parts from
- libevent (they use the libevent emulation inside libev). Configure and
- Makefile stuff is also a more or less direct copy of libevent, and are
- maintained by the libevent authors.
-
- If you downloaded the libev distribution (without libevent), then
- you only get the core parts of the library, meaning http and dns
- client/server code and similar things are missing. Only the core event
- loop is included.
+ Homepage: http://software.schmorp.de/pkg/libev
+ Mailinglist: libev@lists.schmorp.de
+ http://lists.schmorp.de/cgi-bin/mailman/listinfo/libev
+ Library Documentation: http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod
- If you are looking for an easily embeddable version, I recommend using
- the libev standalone distribution or the CVS repository.
+ Libev is modelled (very losely) after libevent and the Event perl
+ module, but is faster, scales better and is more correct, and also more
+ featureful. And also smaller. Yay.
+
+ Some of the specialties of libev not commonly found elsewhere are:
+
+ - extensive and detailed, readable documentation (not doxygen garbage).
+ - fully supports fork, can detect fork in various ways and automatically
+ re-arms kernel mechanisms that do not support fork.
+ - highly optimised select, poll, epoll, kqueue and event ports backends.
+ - filesystem object (path) watching (with optional linux inotify support).
+ - wallclock-based times (using absolute time, cron-like).
+ - relative timers/timeouts (handle time jumps).
+ - fast intra-thread communication between multiple
+ event loops (with optional fast linux eventfd backend).
+ - extremely easy to embed.
+ - very small codebase, no bloated library.
+ - fully extensible by being able to plug into the event loop,
+ integrate other event loops, integrate other event loop users.
+ - very little memory use (small watchers, small event loop data).
+ - optional C++ interface allowing method and function callbacks
+ at no extra memory or runtime overhead.
+ - optional Perl interface with similar characteristics (capable
+ of running Glib/Gtk2 on libev, interfaces with Net::SNMP and
+ libadns).
+ - support for other languages (multiple C++ interfaces, D, Ruby,
+ Python) available from third-parties.
Examples of programs that embed libev: the EV perl module,
- rxvt-unicode, gvpe (GNU Virtual Private Ethernet) and deliantra
- (http://www.deliantra.net).
-
-DIFFERENCES AND COMPARISON TO LIBEVENT
-
- The comparisons below are relative to libevent-1.3e.
-
- - multiple watchers can wait for the same event without deregistering others,
- both for file descriptors as well as signals.
- (registering two read events on fd 10 and unregistering one will not
- break the other).
-
- - fork() is supported and can be handled
- (there is no way to recover from a fork with libevent).
-
- - timers are handled as a priority queue (important operations are O(1))
- (libevent uses a much less efficient but more complex red-black tree).
-
- - supports absolute (wallclock-based) timers in addition to relative ones,
- i.e. can schedule timers to occur after n seconds, or at a specific time.
-
- - timers can be repeating (both absolute and relative ones).
-
- - absolute timers can have customised rescheduling hooks (suitable for cron-like
- applications).
-
- - detects time jumps and adjusts timers
- (works for both forward and backward time jumps and also for absolute timers).
-
- - race-free signal processing
- (libevent may delay processing signals till after the next event).
-
- - more efficient epoll backend
- (stopping and starting an io watcher between two loop iterations will not
- result in spurious epoll_ctl calls).
-
- - usually less calls to gettimeofday and clock_gettime
- (libevent calls it on every timer event change, libev twice per iteration).
-
- - watchers use less memory
- (libevent watcher on amd64: 152 bytes, libev native: <= 56 bytes, libevent emulation: 144 bytes).
-
- - library uses less memory
- (libevent allocates large data structures wether used or not, libev
- scales all its data structures dynamically).
-
- - no hardcoded arbitrary limits
- (libevent contains an off-by-one bug and sometimes hardcodes limits).
-
- - libev separates timer, signal and io watchers from each other
- (libevent combines them, but with libev you can combine them yourself
- by reusing the same callback and still save memory).
-
- - simpler design, backends are potentially much simpler
- (in libevent, backends have to deal with watchers, thus the problems with
- wildly different semantics between diferent backends)
- (epoll backend in libevent: 366 lines no caching, libev: 90 lines full caching).
-
- - libev handles EBADF gracefully by removing the offending fds.
-
- - libev communicates errors to the callback, libevent to the
- event adder or not at all.
-
- - doesn't rely on nonportable BSD header files.
-
- - an event.h compatibility header exists, and can be used to run a wide
- range of libevent programs unchanged (such as evdns.c).
-
- - win32 compatibility for the core parts.
- (the backend is fd-based as documented and on other platforms,
- not handle-based like libevent, and can be used for both winscoket environments
- and unix-like ones).
-
- - libev can be embedded easily with or without autoconf support into
- other programs, with no changes to the source code necessary.
-
- - the event core library (ev and event layer) compiles and works both as
- C and C++.
-
- - a simple C++ wrapper that supports methods as callbacks exists.
-
- - a full featured and widely used perl module is available.
-
- whats missing?
+ rxvt-unicode, gvpe (GNU Virtual Private Ethernet), the Deliantra MMORPG
+ server (http://www.deliantra.net/), Rubinius (a next-generation Ruby
+ VM), the Ebb web server, the Rev event toolkit.
- - no event-like priority support at the moment (the ev priorities work
- differently, but you can use idle watchers to get a similar effect).
-AUTHOR
+CONTRIBUTORS
libev was written and designed by Marc Lehmann and Emanuele Giaquinta.
The following people sent in patches or made other noteworthy
- contributions to the design (if I forgot to include you, please shout
- at me, it was an accident):
+ contributions to the design (for minor patches, see the Changes
+ file. If I forgot to include you, please shout at me, it was an
+ accident):
W.C.A. Wijngaards
Christopher Layne