Rust · Class

Cow

Rust's Cow is a clone-on-write smart pointer. It reads borrowed data without copying and creates owned data only when mutation or ownership is needed.

Last updated 2 November 2026

Since

1.0.0

pub enum Cow<'a, B> where B: 'a + ToOwned + ?Sized {
    Borrowed(&'a B),
    Owned(<B as ToOwned>::Owned),
}

Source: Cow in std::borrow - Rust. Checked 2026-11-03.