listener_main.cpp

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/**
 * @file listener_main.cpp
 *
 * Tool for listening to topics.
 */

#include <px4_platform_common/module.h>
#include <px4_platform_common/getopt.h>

#include <poll.h>

#include "topic_listener.hpp"
#include "topic_listener_generated.hpp"

// Amount of time to wait when listening for a message, before giving up.
static constexpr float MESSAGE_TIMEOUT_S = 2.0f;

extern "C" __EXPORT int listener_main(int argc, char *argv[]);

static void usage();

void listener(listener_print_topic_cb cb, const orb_id_t &id, unsigned num_msgs, int topic_instance,
          unsigned topic_interval)
{

    if (topic_instance == -1 && num_msgs == 1) {
        // first count the number of instances
        int instances = 0;

        for (int i = 0; i < ORB_MULTI_MAX_INSTANCES; i++) {
            if (orb_exists(id, i) == PX4_OK) {
                instances++;
            }
        }

        if (instances == 1) {
            PX4_INFO_RAW("\nTOPIC: %s\n", id->o_name);
            int sub = orb_subscribe(id);
            cb(id, sub);
            orb_unsubscribe(sub);

        } else if (instances > 1) {
            PX4_INFO_RAW("\nTOPIC: %s %d instances\n", id->o_name, instances);

            for (int i = 0; i < ORB_MULTI_MAX_INSTANCES; i++) {
                if (orb_exists(id, i) == PX4_OK) {
                    PX4_INFO_RAW("\nInstance %d:\n", i);
                    int sub = orb_subscribe_multi(id, i);
                    cb(id, sub);
                    orb_unsubscribe(sub);
                }
            }
        }

        if (instances == 0) {
            PX4_INFO_RAW("never published\n");
        }

    } else {
        // default to the first instance if not specified
        if (topic_instance == -1) {
            topic_instance = 0;
        }

        if (orb_exists(id, topic_instance) != 0) {
            PX4_INFO_RAW("never published\n");
            return;
        }

        int sub = orb_subscribe_multi(id, topic_instance);
        orb_set_interval(sub, topic_interval);

        unsigned msgs_received = 0;

        struct pollfd fds[2] {};
        // Poll for user input (for q or escape)
        fds[0].fd = 0; /* stdin */
        fds[0].events = POLLIN;
        // Poll the UOrb subscription
        fds[1].fd = sub;
        fds[1].events = POLLIN;

        while (msgs_received < num_msgs) {

            if (poll(&fds[0], 2, int(MESSAGE_TIMEOUT_S * 1000)) > 0) {

                // Received character from stdin
                if (fds[0].revents & POLLIN) {
                    char c = 0;
                    int ret = read(0, &c, 1);

                    if (ret) {
                        return;
                    }

                    switch (c) {
                    case 0x03: // ctrl-c
                    case 0x1b: // esc
                    case 'q':
                        return;
                        /* not reached */
                    }
                }

                // Received message from subscription
                if (fds[1].revents & POLLIN) {
                    msgs_received++;

                    PX4_INFO_RAW("\nTOPIC: %s instance %d #%d\n", id->o_name, topic_instance, msgs_received);

                    int ret = cb(id, sub);

                    if (ret != PX4_OK) {
                        PX4_ERR("listener callback failed (%i)", ret);
                    }
                }

            } else {
                PX4_INFO_RAW("Waited for %.1f seconds without a message. Giving up.\n", (double) MESSAGE_TIMEOUT_S);
                break;
            }
        }

        orb_unsubscribe(sub);
    }


}

int listener_main(int argc, char *argv[])
{
    if (argc <= 1) {
        usage();
        return 1;
    }

    char *topic_name = argv[1];

    int topic_instance = -1;
    unsigned topic_rate = 0;
    unsigned num_msgs = 0;

    int myoptind = 1;
    int ch;
    const char *myoptarg = nullptr;

    while ((ch = px4_getopt(argc, argv, "i:r:n:", &myoptind, &myoptarg)) != EOF) {
        switch (ch) {

        case 'i':
            topic_instance = strtol(myoptarg, nullptr, 0);
            break;

        case 'r':
            topic_rate = strtol(myoptarg, nullptr, 0);
            break;

        case 'n':
            num_msgs = strtol(myoptarg, nullptr, 0);
            break;

        default:
            usage();
            return -1;
            break;
        }
    }

    if (num_msgs == 0) {
        if (topic_rate != 0) {
            num_msgs = 30 * topic_rate; // arbitrary limit (30 seconds at max rate)

        } else {
            num_msgs = 1;
        }
    }

    listener_generated(topic_name, topic_instance, topic_rate, num_msgs);

    return 0;
}


static void
usage()
{
    PRINT_MODULE_DESCRIPTION(
        R"DESCR_STR(
Utility to listen on uORB topics and print the data to the console.

The listener can be exited any time by pressing Ctrl+C, Esc, or Q.
)DESCR_STR");

    PRINT_MODULE_USAGE_NAME("listener", "command");
    PRINT_MODULE_USAGE_ARG("<topic_name>", "uORB topic name", false);

    PRINT_MODULE_USAGE_PARAM_INT('i', 0, 0, ORB_MULTI_MAX_INSTANCES - 1, "Topic instance", true);
    PRINT_MODULE_USAGE_PARAM_INT('n', 1, 0, 100, "Number of messages", true);
    PRINT_MODULE_USAGE_PARAM_INT('r', 0, 0, 1000, "Subscription rate (unlimited if 0)", true);
}