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Instead of building the libev library you can also include the code
as-is into your programs. To update, you only have to copy a few files
into your source tree.
This is how it works:
To include only the libev core (all the ev_* functions):
#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):
#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_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.c" includes the backend files directly when enabled.
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:
Instead of using EV_STANDALONE=1 and providing your config in whatever
way you want, you can also m4_include([libev.m4]) in your
and leave EV_STANDALONE off. ev.c will then include "config.h" and
configure itself accordingly.
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", which keeps libev from including config.h or
other files, 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 libev code alone.
If undefined or 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
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.
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
doesn'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. Should not be defined on non-win32
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 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 backend. Its 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. Darwin brokenness
will be detected at runtime and routed around by disabling this
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
Similarly to EV_H, this macro cna 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 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 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
( 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.