Function default_write_vectored 

#[doc(hidden)]
pub(crate) fn default_write_vectored<F>(
    write: F,
    bufs: &[IoSlice<'_>],
) -> Result<usize, Error>
where
    F: FnOnce(&[u8]) -> Result<usize, Error>,

🔬This is a nightly-only experimental API. (core_io_internals)

Default implementation of Write::write_vectored, which is currently used in libstd for file system implementations of similar methods.