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).
+ +Depending on what features you need you need to include one or more sets of files +in your app.
+ +To include only the libev core (all the ev_* functions), with manual
+configuration (no autoconf):
#define EV_STANDALONE 1 + #include "ev.c" + ++
This will automatically include 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 ev.h in all files wishing to use this API (best +done by writing a wrapper around 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) + ++
ev.c includes the backend files directly when enabled, so you only need +to compile a single file.
+ +To include the libevent compatibility API, also include:
+#include "event.c" + ++
in the file including ev.c, and:
+#include "event.h" + ++
in the files that want to use the libevent API. This also includes ev.h.
+You need the following additional files for this:
+event.h + event.c + ++ +
Instead of using EV_STANDALONE=1 and providing your config in
+whatever way you want, you can also m4_include([libev.m4]) in your
+configure.ac and leave EV_STANDALONE off. ev.c will then include
+config.h and configure itself accordingly.
For this of course you need the m4 file:
+libev.m4 + ++ +
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.
+Must always be 1 if you do not use autoconf configuration, which
+keeps libev from including 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
+event.h that are not directly supported by the libev core alone.
If defined to be 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 clock_gettime
+function is hiding in (often -lrt).
If defined to be 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 gettimeofday by clock_get
+(CLOCK_REALTIME, ...) and will not normally affect correctness. See tzhe note about libraries
+in the description of EV_USE_MONOTONIC, though.
If undefined or defined to be 1, libev will compile in support for the
+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.
If defined to 1, then the select backend will use the system fd_set
+structure. This is useful if libev doesn't compile due to a missing
+NFDBITS or 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 FD_SETSIZE macro, set before compilation, might
+influence the size of the fd_set used.
When defined to 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
+_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.
If defined to be 1, libev will compile in support for the poll(2)
+backend. Otherwise it will be enabled on non-win32 platforms. It
+takes precedence over select.
If defined to be 1, libev will compile in support for the Linux
+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.
If defined to be 1, libev will compile in support for the BSD style
+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.
If defined to be 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.
reserved for future expansion, works like the USE symbols above.
+The name of the ev.h header file used to include it. The default if
+undefined is <ev.h> in event.h and "ev.h" in ev.c. This
+can be used to virtually rename the ev.h header file in case of conflicts.
If EV_STANDALONE isn't 1, this variable can be used to override
+ev.c's idea of where to find the config.h file, similarly to
+EV_H, above.
Similarly to EV_H, this macro can be used to override event.c's idea
+of how the event.h header can be found.
If defined to be 0, then 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.
If undefined or defined to 1, then all event-loop-specific functions
+will have the 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.
If undefined or defined to be 1, then periodic timers are supported,
+otherwise not. This saves a few kb of code.
By default, all watchers have a 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 ";" */ + ++
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 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++.
+ +For a real-world example of a program the includes libev +verbatim, you can have a look at the EV perl module +(http://software.schmorp.de/pkg/EV.html). It has the libev files in +the libev/ subdirectory and includes them in the EV/EVAPI.h (public +interface) and EV.xs (implementation) files. Only the 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 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 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" + + + +
Marc Lehmann <libev@schmorp.de>.
+Marc Lehmann <libev@schmorp.de>.