+=over 4
+
+=item C<EV_A>, C<EV_A_>
+
+This provides the loop I<argument> for functions, if one is required ("ev
+loop argument"). The C<EV_A> form is used when this is the sole argument,
+C<EV_A_> is used when other arguments are following. Example:
+
+ ev_unref (EV_A);
+ ev_timer_add (EV_A_ watcher);
+ ev_loop (EV_A_ 0);
+
+It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
+which is often provided by the following macro.
+
+=item C<EV_P>, C<EV_P_>
+
+This provides the loop I<parameter> for functions, if one is required ("ev
+loop parameter"). The C<EV_P> form is used when this is the sole parameter,
+C<EV_P_> is used when other parameters are following. Example:
+
+ // this is how ev_unref is being declared
+ static void ev_unref (EV_P);
+
+ // this is how you can declare your typical callback
+ static void cb (EV_P_ ev_timer *w, int revents)
+
+It declares a parameter C<loop> of type C<struct ev_loop *>, quite
+suitable for use with C<EV_A>.
+
+=item C<EV_DEFAULT>, C<EV_DEFAULT_>
+
+Similar to the other two macros, this gives you the value of the default
+loop, if multiple loops are supported ("ev loop default").
+
+=back
+
+Example: Declare and initialise a check watcher, utilising the above
+macros so it will work regardless of whether multiple loops are supported
+or not.
+
+ static void
+ check_cb (EV_P_ ev_timer *w, int revents)
+ {
+ ev_check_stop (EV_A_ w);
+ }
+
+ ev_check check;
+ ev_check_init (&check, check_cb);
+ ev_check_start (EV_DEFAULT_ &check);
+ ev_loop (EV_DEFAULT_ 0);
+
+=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 necessary 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 enabled 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 this 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> undefined. 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, although 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 the
+note about libraries in the description of C<EV_USE_MONOTONIC>, though.
+
+=item EV_USE_NANOSLEEP
+
+If defined to be C<1>, libev will assume that C<nanosleep ()> is available
+and will use it for delays. Otherwise it will use C<select ()>.
+
+=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 whether 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.