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| -rw-r--r-- | ev.pod | 276 |
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@@ -1416,6 +1416,282 @@ the constructor. io.start (fd, ev::READ); } +=head1 EMBEDDING + +Libev can (and often is) directly embedded into host +applications. Examples of applications that embed it include the Deliantra +Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) +and rxvt-unicode. + +The goal is to enable you to just copy the neecssary files into your +source directory without having to change even a single line in them, so +you can easily upgrade by simply copying (or having a checked-out copy of +libev somewhere in your source tree). + +=head2 FILESETS + +Depending on what features you need you need to include one or more sets of files +in your app. + +=head3 CORE EVENT LOOP + +To include only the libev core (all the C<ev_*> functions), with manual +configuration (no autoconf): + + #define EV_STANDALONE 1 + #include "ev.c" + +This will automatically include F<ev.h>, too, and should be done in a +single C source file only to provide the function implementations. To use +it, do the same for F<ev.h> in all files wishing to use this API (best +done by writing a wrapper around F<ev.h> that you can include instead and +where you can put other configuration options): + + #define EV_STANDALONE 1 + #include "ev.h" + +Both header files and implementation files can be compiled with a C++ +compiler (at least, thats a stated goal, and breakage will be treated +as a bug). + +You need the following files in your source tree, or in a directory +in your include path (e.g. in libev/ when using -Ilibev): + + ev.h + ev.c + ev_vars.h + ev_wrap.h + + ev_win32.c required on win32 platforms only + + ev_select.c only when select backend is enabled (which is is by default) + ev_poll.c only when poll backend is enabled (disabled by default) + ev_epoll.c only when the epoll backend is enabled (disabled by default) + ev_kqueue.c only when the kqueue backend is enabled (disabled by default) + ev_port.c only when the solaris port backend is enabled (disabled by default) + +F<ev.c> includes the backend files directly when enabled, so you only need +to compile a single file. + +=head3 LIBEVENT COMPATIBILITY API + +To include the libevent compatibility API, also include: + + #include "event.c" + +in the file including F<ev.c>, and: + + #include "event.h" + +in the files that want to use the libevent API. This also includes F<ev.h>. + +You need the following additional files for this: + + event.h + event.c + +=head3 AUTOCONF SUPPORT + +Instead of using C<EV_STANDALONE=1> and providing your config in +whatever way you want, you can also C<m4_include([libev.m4])> in your +F<configure.ac> and leave C<EV_STANDALONE> off. F<ev.c> will then include +F<config.h> and configure itself accordingly. + +For this of course you need the m4 file: + + libev.m4 + +=head2 PREPROCESSOR SYMBOLS/MACROS + +Libev can be configured via a variety of preprocessor symbols you have to define +before including any of its files. The default is not to build for multiplicity +and only include the select backend. + +=over 4 + +=item EV_STANDALONE + +Must always be C<1> if you do not use autoconf configuration, which +keeps libev from including F<config.h>, and it also defines dummy +implementations for some libevent functions (such as logging, which is not +supported). It will also not define any of the structs usually found in +F<event.h> that are not directly supported by the libev core alone. + +=item EV_USE_MONOTONIC + +If defined to be C<1>, libev will try to detect the availability of the +monotonic clock option at both compiletime and runtime. Otherwise no use +of the monotonic clock option will be attempted. If you enable this, you +usually have to link against librt or something similar. Enabling it when +the functionality isn't available is safe, though, althoguh you have +to make sure you link against any libraries where the C<clock_gettime> +function is hiding in (often F<-lrt>). + +=item EV_USE_REALTIME + +If defined to be C<1>, libev will try to detect the availability of the +realtime clock option at compiletime (and assume its availability at +runtime if successful). Otherwise no use of the realtime clock option will +be attempted. This effectively replaces C<gettimeofday> by C<clock_get +(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries +in the description of C<EV_USE_MONOTONIC>, though. + +=item EV_USE_SELECT + +If undefined or defined to be C<1>, libev will compile in support for the +C<select>(2) backend. No attempt at autodetection will be done: if no +other method takes over, select will be it. Otherwise the select backend +will not be compiled in. + +=item EV_SELECT_USE_FD_SET + +If defined to C<1>, then the select backend will use the system C<fd_set> +structure. This is useful if libev doesn't compile due to a missing +C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on +exotic systems. This usually limits the range of file descriptors to some +low limit such as 1024 or might have other limitations (winsocket only +allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might +influence the size of the C<fd_set> used. + +=item EV_SELECT_IS_WINSOCKET + +When defined to C<1>, the select backend will assume that +select/socket/connect etc. don't understand file descriptors but +wants osf handles on win32 (this is the case when the select to +be used is the winsock select). This means that it will call +C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, +it is assumed that all these functions actually work on fds, even +on win32. Should not be defined on non-win32 platforms. + +=item EV_USE_POLL + +If defined to be C<1>, libev will compile in support for the C<poll>(2) +backend. Otherwise it will be enabled on non-win32 platforms. It +takes precedence over select. + +=item EV_USE_EPOLL + +If defined to be C<1>, libev will compile in support for the Linux +C<epoll>(7) backend. Its availability will be detected at runtime, +otherwise another method will be used as fallback. This is the +preferred backend for GNU/Linux systems. + +=item EV_USE_KQUEUE + +If defined to be C<1>, libev will compile in support for the BSD style +C<kqueue>(2) backend. Its actual availability will be detected at runtime, +otherwise another method will be used as fallback. This is the preferred +backend for BSD and BSD-like systems, although on most BSDs kqueue only +supports some types of fds correctly (the only platform we found that +supports ptys for example was NetBSD), so kqueue might be compiled in, but +not be used unless explicitly requested. The best way to use it is to find +out wether kqueue supports your type of fd properly and use an embedded +kqueue loop. + +=item EV_USE_PORT + +If defined to be C<1>, libev will compile in support for the Solaris +10 port style backend. Its availability will be detected at runtime, +otherwise another method will be used as fallback. This is the preferred +backend for Solaris 10 systems. + +=item EV_USE_DEVPOLL + +reserved for future expansion, works like the USE symbols above. + +=item EV_H + +The name of the F<ev.h> header file used to include it. The default if +undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This +can be used to virtually rename the F<ev.h> header file in case of conflicts. + +=item EV_CONFIG_H + +If C<EV_STANDALONE> isn't C<1>, this variable can be used to override +F<ev.c>'s idea of where to find the F<config.h> file, similarly to +C<EV_H>, above. + +=item EV_EVENT_H + +Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea +of how the F<event.h> header can be found. + +=item EV_PROTOTYPES + +If defined to be C<0>, then F<ev.h> will not define any function +prototypes, but still define all the structs and other symbols. This is +occasionally useful if you want to provide your own wrapper functions +around libev functions. + +=item EV_MULTIPLICITY + +If undefined or defined to C<1>, then all event-loop-specific functions +will have the C<struct ev_loop *> as first argument, and you can create +additional independent event loops. Otherwise there will be no support +for multiple event loops and there is no first event loop pointer +argument. Instead, all functions act on the single default loop. + +=item EV_PERIODICS + +If undefined or defined to be C<1>, then periodic timers are supported, +otherwise not. This saves a few kb of code. + +=item EV_COMMON + +By default, all watchers have a C<void *data> member. By redefining +this macro to a something else you can include more and other types of +members. You have to define it each time you include one of the files, +though, and it must be identical each time. + +For example, the perl EV module uses something like this: + + #define EV_COMMON \ + SV *self; /* contains this struct */ \ + SV *cb_sv, *fh /* note no trailing ";" */ + +=item EV_CB_DECLARE(type) + +=item EV_CB_INVOKE(watcher,revents) + +=item ev_set_cb(ev,cb) + +Can be used to change the callback member declaration in each watcher, +and the way callbacks are invoked and set. Must expand to a struct member +definition and a statement, respectively. See the F<ev.v> header file for +their default definitions. One possible use for overriding these is to +avoid the ev_loop pointer as first argument in all cases, or to use method +calls instead of plain function calls in C++. + +=head2 EXAMPLES + +For a real-world example of a program the includes libev +verbatim, you can have a look at the EV perl module +(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in +the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public +interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file +will be compiled. It is pretty complex because it provides its own header +file. + +The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file +that everybody includes and which overrides some autoconf choices: + + #define EV_USE_POLL 0 + #define EV_MULTIPLICITY 0 + #define EV_PERIODICS 0 + #define EV_CONFIG_H <config.h> + + #include "ev++.h" + +And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: + + #include "rxvttoolkit.h" + + /* darwin has problems with its header files in C++, requiring this namespace juggling */ + using namespace ev; + + #include "ev.c" + + =head1 AUTHOR Marc Lehmann <libev@schmorp.de>. |