EV
Light event-loop library loosely inspired by the excellent libuv, in a single
small (< 700 sloc) header, based on the common IO multiplexing
implementations available, epoll on linux, kqueue on BSD-like and OSX,
poll/select as a fallback, dependencies-free.
A common usage of the library is to craft event-driven TCP servers, ev_tcp.h
exposes a set of APIs to fulfill this purpose in a simple manner.
TLS is supported as well through OpenSSL, and source have to be compiled adding
a -DHAVE_OPENSSL=1 to enable it. Of course it requires libssl-dev installed
on the host machine to work.
In conclusion the library is composed of 2 distinct modules
ev.ha generic eventloop for I/O bound concurrency on a single-thread:- Based on the best multiplexing IO implementation available on the host, supporting epoll/poll/select on linux and kqueue on BSD
- All IO operations are done in a non-blocking way
- Support for time based repeated tasks
ev_tcp.hexposes a set of APIs to simply create an event-driven TCP server usingev.has the main engine:- TCP/UNIX socket connections
- Basic TLS support through OpenSSL
- Callback oriented design
To adopt these libraries it's required to define a value just before inclusion in one file only in the project:
#define EV_SOURCE
#include "ev.h"Or in case of ev_tcp.h
#define EV_SOURCE
#define EV_TCP_SOURCE
#include "ev_tcp.h"Running examples
A simple event-driven echo server
$ make echo-server
Write periodically on the screen ping and pong on different frequencies,
referred as cron tasks
$ make ping-pong
Helper APIs
Lightweight event-driven hello world TCP server
#include <stdio.h>
#include <stdlib.h>
#define EV_SOURCE // add before ev_tcp
#define EV_TCP_SOURCE // add before ev_tcp
#include "../ev_tcp.h"
#define HOST "127.0.0.1"
#define PORT 5959
#define BACKLOG 128
static void on_close(ev_tcp_handle *client, int err) {
(void) client;
if (err == EV_TCP_SUCCESS)
printf("Connection closed\n");
else
printf("Connection closed: %s\n", ev_tcp_err(err));
free(client);
}
static void on_write(ev_tcp_handle *client) {
(void) client;
printf("Written response\n");
}
static void on_data(ev_tcp_handle *client) {
printf("Received %li bytes\n", client->buffer.size);
if (strncmp(client->buffer.buf, "quit", 4) == 0)
ev_tcp_close_handle(client);
else
// Enqueue a write of the buffer content for the next loop cycle
ev_tcp_enqueue_write(client);
// If want to respond on the same loop cycle
// ev_tcp_write(client);
}
static void on_connection(ev_tcp_handle *server) {
ev_tcp_handle *client = malloc(sizeof(*client));
if (!client) {
fprintf(stderr, "On connection failed: Out of memory");
exit(EXIT_FAILURE);
}
int err = ev_tcp_server_accept(server, client, on_data, on_write);
if (err < 0)
free(client);
else
ev_tcp_handle_set_on_close(client, on_close);
}
int main(void) {
ev_context *ctx = ev_get_ev_context();
ev_tcp_server server;
int err = 0;
if ((err = ev_tcp_server_init(&server, ctx, 128)) < 0) {
fprintf(stderr, "ev_tcp_server_init failed: %s", ev_tcp_err(err));
exit(EXIT_FAILURE);
}
// To set TLS using OpenSSL
// struct ev_tls_options tls_opt = {
// .ca = CA,
// .cert = CERT,
// .key = KEY
// };
// tls_opt.protocols = EV_TLSv1_2|EV_TLSv1_3;
// ev_tcp_server_set_tls(&server, &tls_opt);
int err = ev_tcp_server_listen(&server, HOST, PORT, on_connection);
if (err < 0)
exit(EXIT_FAILURE);
// Blocking call
ev_tcp_server_run(&server);
// This could be registered to a SIGINT|SIGTERM signal notification
// to stop the server with Ctrl+C
ev_tcp_server_stop(&server);
return 0;
}Take a look to examples/ directory for more snippets.
Roadmap
- (Re)Move server abstraction on generic
ev_tcp_handle, add client - UDP helper APIs
- Improve error handling
- Documentation