Function fwrite 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn fwrite(
    ptr: *const c_void,
    size: size_t,
    nitems: size_t,
    stream: *mut FILE,
) -> size_t

See https://pubs.opengroup.org/onlinepubs/9799919799/functions/fwrite.html.

Write nitems of size size from ptr to stream