sleep(4) frizz reduction spray for zoom

ldpreload.c

/*
sleep(4) frizz reduction spray for zoom

because this thing decides to freeze for a long time every time i plug/unplug
my usb hub, or when any cable is loose. seems to be 4 seconds multiplied by
number of plug/unplug events received

caveats:
- your video will still be frozen as usual, re-enable video
- this might increase the risk of your devices not showing up after it
unfreezes (hopefully the first longer sleep takes care of that)
- no manual entry for sleep in section 4

to compile:

$ gcc -fPIC -Wall -ldl -shared ldpreload.c -o ldpreload.so

to use:

$ LD_PRELOAD=$PWD/ldpreload.so zoom
*/

#define _GNU_SOURCE
#include <dlfcn.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <time.h>

/* seconds since the last sleep(4) call in which shorter sleeps are applied */
#define GRACE_PERIOD_S 4

/* the first sleep is longer, which seems needed to get devices back */
#define FIRST_LONG_SLEEP_MS 2000

/* each sleep within the grace period is shorter, to avoid accumulating */
#define SHORTER_SLEEPS_MS 1000

static int (* sleep_real)(wchar_t) = NULL;

static __attribute__((__constructor__)) void init(void) {
    sleep_real = dlsym(RTLD_NEXT, "sleep");
}

unsigned int sleep(unsigned int seconds) {
    static time_t last_long_sleep = 0;

    if (seconds == 4) {
        time_t now = time(NULL);
        if (now - last_long_sleep < 3) {
            /* subsequent sleeps within 3 seconds are shorter each */
            usleep(SHORTER_SLEEPS_MS * 1000);
        } else {
            /* the first sleep is longer,
             * which appears to be needed for getting devices back */
            usleep(FIRST_LONG_SLEEP_MS * 1000);
        }
        last_long_sleep = now;
        return 0;
    }
    return sleep_real(seconds);
}