Function lv_cache_add 

pub unsafe extern "C" fn lv_cache_add(
    cache: *mut lv_cache_t,
    key: *const c_void,
    user_data: *mut c_void,
) -> *mut lv_cache_entry_t

Add a new cache entry with the given key and data. If the cache is full, the cache’s policy will be used to evict an entry. @param cache The cache object pointer to add the entry. @param key The key of the entry to add. @param user_data A user data pointer that will be passed to the create callback. @return Returns a pointer to the added cache entry on success with lv_cache_entry_t::ref_cnt incremented, NULL on error.