Example epoll-based ncurses MPD client

epoll_mpd_client.c

#include <curses.h>
#include <mpd/client.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <unistd.h>

#define MAX_EVENTS 10

void
toggle_play_pause(struct mpd_connection *mpd_conn) {
    // Get the current status
    struct mpd_status *status = mpd_run_status(mpd_conn);

    // Play/pause/unpase depending on the current state
    switch (mpd_status_get_state(status)) {
    case MPD_STATE_UNKNOWN:
        break;
    case MPD_STATE_STOP:
        mpd_run_play(mpd_conn);
        break;
    case MPD_STATE_PAUSE:
        mpd_run_pause(mpd_conn, 0);
        break;
    case MPD_STATE_PLAY:
        mpd_run_pause(mpd_conn, 1);
        break;
    default:
        break;
    }
}

int
main(int argc, char **argv) {
    // Initialize the mpd connection and get the underlying socket fd
    struct mpd_connection *mpd_conn = mpd_connection_new("127.0.0.1", 6600, 0);
    if (mpd_conn == NULL)
        exit(EXIT_FAILURE);
    mpd_send_idle(mpd_conn);
    int mpd_fd = mpd_connection_get_fd(mpd_conn);

    // Startup ncurses
    initscr();
    noecho();
    curs_set(0);
    timeout(0);

    // Print the available key commands
    printw("Commands:");
    mvprintw(1, 0, "    Toggle Play/Pause:     p");
    mvprintw(2, 0, "    Quit:                  q");
    refresh();

    // Create an epoll instance for the event loop
    int epfd = epoll_create1(0);
    if (epfd == -1)
        exit(EXIT_FAILURE);

    // Register the mpd socket with epoll
    struct epoll_event ev_mpd = {.events = EPOLLIN, .data = {.fd = mpd_fd}};
    if (epoll_ctl(epfd, EPOLL_CTL_ADD, mpd_fd, &ev_mpd) == -1)
        exit(EXIT_FAILURE);

    // Register stdin with epoll
    struct epoll_event ev_stdin = {.events = EPOLLIN,
                                   .data = {.fd = STDIN_FILENO}};
    if (epoll_ctl(epfd, EPOLL_CTL_ADD, STDIN_FILENO, &ev_stdin) == -1)
        exit(EXIT_FAILURE);

    // Main event loop
    struct epoll_event evlist[MAX_EVENTS];
    for (;;) {
        int nfds = epoll_wait(epfd, evlist, MAX_EVENTS, -1);
        if (nfds == -1)
            exit(EXIT_FAILURE);
        for (int i = 0; i < nfds; ++i) {
            if (evlist[i].data.fd == mpd_fd) {
                enum mpd_idle idle = mpd_recv_idle(mpd_conn, false);
                time_t t = time(NULL);
                mvprintw(5, 0, "State last changed: %s %s\n",
                         mpd_idle_name(idle), asctime(localtime(&t)));
                mpd_send_idle(mpd_conn);
            } else if (evlist[i].data.fd == STDIN_FILENO) {
                int c = getch();
                mpd_run_noidle(mpd_conn);
                while (c != -1) {
                    mvprintw(4, 0, "Key pressed: %c\n", (char)c);
                    if (c == 112) // p
                        toggle_play_pause(mpd_conn);
                    if (c == 113) // q
                        goto done;
                    c = getch();
                }
                mpd_send_idle(mpd_conn);
            }
        }

        refresh();
    }

done:
    endwin();
    mpd_connection_free(mpd_conn);
    return EXIT_SUCCESS;
}