X-Git-Url: https://git.llucax.com/software/libev.git/blobdiff_plain/469af6002e7d33bcc351c1113afb188c3c246b91..1e251ffd9e2bf720df7759c2eb3c807f5b0d474f:/README?ds=inline diff --git a/README b/README index f86fcf6..1585243 100644 --- a/README +++ b/README @@ -1,69 +1,125 @@ -libev is modelled after libevent (http://monkey.org/~provos/libevent/), but aims -to be faster and more correct, and also more featureful. Examples: +libev is a high-performance event loop/event model with lots of features. +(see benchmark at http://libev.schmorp.de/bench.html) -(comparisons relative to libevent-1.3e and libev-0.00) + Homepage: http://software.schmorp.de/pkg/libev + E-Mail: libev@lists.schmorp.de -- 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) + It is modelled (very losely) after libevent + (http://monkey.org/~provos/libevent/) and the Event perl module, but aims + to be faster and more correct, and also more featureful. -- fork() is supported and can be handled - (there is no way to recover from a fork when libevent is active) +ABOUT THIS DISTRIBUTION -- timers are handled as a priority queue - (libevent uses a less efficient red-black tree) + If you downloaded a 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. -- 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. + If you are looking for an easily embeddable version, I recommend using + the CVS repository (linked from the homepage, above), which contains + only the libev core parts. -- timers can be repeating (both absolute and relative ones) + Examples of programs that embed libev: the EV perl module, + rxvt-unicode, gvpe (GNU Virtual Private Ethernet) and deliantra + (http://www.deliantra.net). -- detects time jumps and adjusts timers - (works for both forward and backward time jumps and also for absolute timers) +DIFFERENCES AND COMPARISON TO LIBEVENT -- can correctly remove timers while executing callbacks - (libevent doesn't handle this reliably and can crash) + The comparisons below are relative to libevent-1.3e. -- race-free signal processing - (libevent may delay processing signals till after the next event) + - 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). -- less calls to epoll_ctl - (stopping and starting an io watcher between two loop iterations will now - result in spuriois epoll_ctl calls) + - fork() is supported and can be handled + (there is no way to recover from a fork with libevent). -- usually less calls to gettimeofday and clock_gettime - (libevent calls it on every timer event change, libev twice per iteration) + - timers are handled as a priority queue (important operations are O(1)) + (libevent uses a much less efficient but more complex red-black tree). -- watchers use less memory - (libevent on amd64: 152 bytes, libev: <= 56 bytes) + - 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. -- library uses less memory - (libevent allocates large data structures wether used or not, libev - scales all its data structures dynamically) + - timers can be repeating (both absolute and relative ones). -- no hardcoded arbitrary limits - (libevent contains an off-by-one bug and sometimes hardcodes a limit of - 32000 fds) + - absolute timers can have customised rescheduling hooks (suitable for cron-like + applications). -- 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) + - detects time jumps and adjusts timers + (works for both forward and backward time jumps and also for absolute timers). -- simpler design, backends are potentially much simpler - (in libevent, backends have to deal with watchers, thus the problems) - (epoll backend in libevent: 366 lines, libev: 90 lines, and more features) + - race-free signal processing + (libevent may delay processing signals till after the next event). -- libev handles EBADF gracefully by removing the offending fds. + - more efficient epoll backend + (stopping and starting an io watcher between two loop iterations will not + result in spurious epoll_ctl calls). -whats missing? + - usually less calls to gettimeofday and clock_gettime + (libevent calls it on every timer event change, libev twice per iteration). -- evdns, evhttp, bufferevent are missing, libev is only an even library at - the moment. + - watchers use less memory + (libevent watcher on amd64: 152 bytes, libev native: <= 56 bytes, libevent emulation: 144 bytes). -- no priority support at the moment + - library uses less memory + (libevent allocates large data structures wether used or not, libev + scales all its data structures dynamically). -- kqueue, poll (libev currently implements epoll and select) + - no hardcoded arbitrary limits + (libevent contains an off-by-one bug and sometimes hardcodes limits). -- windows support (whats windows?) + - 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? + + - 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 + + 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): + + W.C.A. Wijngaards + Christopher Layne + Chris Brody