Method _save_backup

libraries/AP_HAL_ChibiOS/Storage.cpp:128–203

save a backup of storage file if we have microSD available. This is very handy for diagnostics, and for moving a copy of storage into SITL for testing */

  SITL for testing
 */
void Storage::_save_backup(void)
{
#ifdef USE_POSIX
    // allow for fallback to microSD based storage
    // create the backup directory if need be
    int ret;
    const char* _storage_bak_directory = HAL_STORAGE_BACKUP_FOLDER;

    if (hal.util->was_watchdog_armed()) {
        // we are under watchdog reset
        // ain't got no time...
        return;
    }

    EXPECT_DELAY_MS(3000);

    // We want to do this desperately,
    // So we keep trying this for a second
    uint32_t start_millis = AP_HAL::millis();
    while(!AP::FS().retry_mount() && (AP_HAL::millis() - start_millis) < 1000) {
        hal.scheduler->delay(1);        
    }

    ret = AP::FS().mkdir(_storage_bak_directory);
    if (ret == -1 && errno != EEXIST) {
        return;
    }

    char* fname = nullptr;
    unsigned curr_bak = 0;
    ret = asprintf(&fname, "%s/last_storage_bak", _storage_bak_directory);
    if (fname == nullptr && (ret <= 0)) {
        return;
    }
    int fd = AP::FS().open(fname, O_RDONLY);
    if (fd != -1) {
        char buf[10];
        memset(buf, 0, sizeof(buf));
        if (AP::FS().read(fd, buf, sizeof(buf)-1) > 0) {
            //only record last HAL_STORAGE_BACKUP_COUNT backups
            curr_bak = (strtol(buf, NULL, 10) + 1)%HAL_STORAGE_BACKUP_COUNT;
        }
        AP::FS().close(fd);
    }

    fd = AP::FS().open(fname, O_WRONLY|O_CREAT|O_TRUNC);
    free(fname);
    fname = nullptr;
    if (fd != -1) {
        char buf[10];
        snprintf(buf, sizeof(buf), "%u\r\n", (unsigned)curr_bak);
        const ssize_t to_write = strlen(buf);
        const ssize_t written = AP::FS().write(fd, buf, to_write);
        AP::FS().close(fd);
        if (written < to_write) {
            return;
        }
    } else {