coderjie / libuev

Lightweight event loop library for Linux

libuEv | Simple event loop for Linux

• Introduction
• API
  • Create an Event Context
  • Register an Event Watcher
  • Start Event Loop
  • Summary
• Using -luev
• Joystick Example
• Build & Install
• Origin & References

NOTE: Incompatible failure mode changes in v2.0 compared to v1.x!

Introduction

libuEv is a simple event loop in the style of the more established libevent, libev and the venerable Xt(3) event loop. The u (micro) in the name refers to both the small feature set and the small size overhead impact of the library.

Failure mode changes introduced in v2.0 may affect users of v1.x, See the ChangeLog for the full details.

The API documentation is available as a separate document.

Example

Notice below how watcher UEV_ERROR conditions must be handled by each callback. I/O watchers must also check for UEV_HUP. Both errors are usually fatal, libuEv makes sure to stop each watcher before a callback runs, leaving it up to the callback to take appropriate action.

#include <stdio.h>
#include <uev/uev.h>

static void cb(uev_t *w, void *arg, int events)
{
    if (UEV_ERROR == events) {
        puts("Problem with timer, attempting to restart.");
        uev_timer_start(w);
    }
	puts("Every other second");
}

int main(void)
{
	uev_t timer;
	uev_ctx_t ctx;

	uev_init(&ctx);
	/* Set up a timer watcher to call cb() every other second */
	uev_timer_init(&ctx, &timer, cb, NULL, 2 * 1000, 2 * 1000);

	return uev_run(&ctx, 0);
}

Build & Install

libuEv use the GNU configure and build system. To try out the bundled examples, use the --enable-examples switch to the configure script. There is also a limited unit test suite that can be useful to learn how the library works.

./configure
make -j5
make test
sudo make install-strip
sudo ldconfig

The resulting .so file is ~14 kiB.

Origin & References

libuEv originates from LibUEvent by Flemming Madsen, but with a rewritten and much cleaner API. It is now more similar to the famous libev by Mark Lehmann. Another library inspiring this project is picoev by Oku Kazuho.

libuEv is developed and maintained by Joachim Nilsson. It is built for and developed on GNU/Linux systems, patches to support *BSD and its kqueue interface are most welcome.