MainLoop API

Below example shows a tiny PulseAudio client that commuincates with the server asking for its basic information. It demonstrates the MainLoop API in action. As we've stated earlier, the Simple API actually uses the mainloop API in a different thread to give the illusion of synchronousness to the calling programs.

#include <locale.h>
#include <signal.h>
#include <errno.h>

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <pulse/pulseaudio.h>
#include <pulsecore/log.h>
#include <pulsecore/core-util.h>

static void quit(pa_mainloop_api *m, int ret) {
    pa_assert(m);
    m->quit(m, ret);
}

static void exit_signal_cb(pa_mainloop_api *m, pa_signal_event *e,
                                 int sig, void *userdata) {
    pa_log("Got %s, exiting ..", strsignal(sig));
    quit(m, 0);
}

static void get_server_info_cb(pa_context *c, const pa_server_info *i,
                                void *userdata) {

    pa_mainloop_api *api = userdata;

    printf("User name: %s\n", i->user_name);
    printf("Host name: %s\n", i->host_name);
    printf("Server name: %s\n", i->server_name);
    printf("Default sink name: %s\n", i->default_sink_name);
    printf("Default source name: %s\n", i->default_source_name);
    printf("Cookie: %04x: %04x\n", i->cookie >> 16, i->cookie & 0xFFFFU);

    quit(api, 0);
}

static void context_state_cb(pa_context *context, void *userdata) {
    pa_operation *o = NULL;
    pa_mainloop_api *api = userdata;

    pa_assert(context);

    switch (pa_context_get_state(context)) {
        case PA_CONTEXT_CONNECTING:
        case PA_CONTEXT_AUTHORIZING:
        case PA_CONTEXT_SETTING_NAME:
            break;

        case PA_CONTEXT_READY:
            o = pa_context_get_server_info(context, get_server_info_cb, api);
            pa_operation_unref(o);
            break;

        case PA_CONTEXT_TERMINATED:
            quit(api, 0);
            break;

        case PA_CONTEXT_FAILED:
        default:
            pa_log_error("Connection failure: %s",
                    pa_strerror(pa_context_errno(context)));
            quit(api, 0);
    }
}

int main(int argc, char *argv[]) {
    pa_context *context = NULL;
    pa_mainloop *mainloop = NULL;
    pa_mainloop_api *api = NULL;
    int ret = 1, mainloop_ret;

    mainloop = pa_mainloop_new();
    if (!mainloop) {
        pa_log_error("pa_mainloop_new() failed");
        goto quit;
    }

    api = pa_mainloop_get_api(mainloop);

    pa_assert_se(pa_signal_init(api) == 0);
    pa_signal_new(SIGINT, exit_signal_cb, NULL);
    pa_signal_new(SIGTERM, exit_signal_cb, NULL);
    pa_disable_sigpipe();

    context = pa_context_new(api, "patest application!");
    if (!context) {
        pa_log_error("pa_context_new() failed");
        goto quit;
    }

    pa_context_set_state_callback(context, context_state_cb, api);
    ret = pa_context_connect(context, NULL, 0, NULL);
    if ( ret < 0) {
        pa_log_error("pa_context_connect(): %s",
                pa_strerror(pa_context_errno(context)));
        goto quit;
    }

    ret = pa_mainloop_run(mainloop, &mainloop_ret);
    if (ret < 0) {
        pa_log("pa_mainloop_run() failed");
        goto quit;
    }

 quit:
    if (context)
        pa_context_unref(context);

    if (mainloop)
        pa_mainloop_free(mainloop);
    return ret;
}