Adding threading to connect wiimotes simultaneously.

[altcoin]

Adding adding wiimotes takes a significant amount of time (2-5 sec per wiimote).

After looking into the STK/wiiuse codebase, I successfully sped up the connection of multiple wiimotes by threading the wiiuse_os_connect function of wiiuse/os_nix.c.
I am not experienced with threading, but it works great on Artix Linux, with STK compiled from git, It can connect two wiimotes as fast as one.

Wiiuse is not threadsafe (https://github.com/wiiuse/wiiuse/issues/109), but since the multithreading is done inside the wiiuse_os_connect() function, only wiiuse_os_connect_single() in os_nix.c must be threadsafe.
I see nothing in wiiuse_os_connect_single() that would be thread-problematic, but someone with more experience can verify that.

Code diff.

wiiuse/src/os.h

Insert this struct to use for holding thread-specific data.


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struct wiiuse_connect_data_t {
    int ret;
    struct wiimote_t * wiimote;
    pthread_t thread_id;
};



wiiuse/src/os_nix.c

Include pthread.h for threading support.


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#include <pthread.h>




Insert this wrapper for wiiuse_os_connect_single(), for pthread_create() to use.


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/**
 *     @brief pthread-compatible wrapper for wiiuse_os_connect_single.
 *
 *     @param wd       Pointer to a wiimote_connect_data_t structure.
 *
 */
void wiiuse_os_connect_threaded(struct wiiuse_connect_data_t *wd) {
    wd->ret = wiiuse_os_connect_single(wd->wiimote, NULL);
}





Update the wiiuse_os_connect() function to look like this:


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/**
 *   @see wiiuse_connect()
 *   @see wiiuse_os_connect_threaded()
 */
int wiiuse_os_connect(struct wiimote_t **wm, int wiimotes)
{
    struct wiiuse_connect_data_t wd[wiimotes];
    int wd_len = 0;

    int connected = 0;
    int i         = 0;

    for (; i < wiimotes; ++i)
    {
        if (!WIIMOTE_IS_SET(wm[i], WIIMOTE_STATE_DEV_FOUND))
        /* if the device address is not set, skip it */
        {
            continue;
        }

        wd[wd_len].wiimote = wm[i];
        wd[wd_len].ret = 0;

        pthread_create(&wd[wd_len].thread_id, NULL, &wiiuse_os_connect_threaded, &wd[wd_len]);
        wd_len ++;
    }

    for (i = 0; i < wd_len; i++) {
        pthread_join(wd[i].thread_id, NULL);

        if (wd[i].ret)
        {
            ++connected;
        }
    }

    return connected;
}