borrow-or-share

Traits for either borrowing or sharing data.

See below for a basic usage of the crate. See the documentation for a detailed walkthrough.

Basic usage

Suppose that you have a generic type that either owns some data or holds a reference to them. You can use this crate to implement on this type a method taking &self that either borrows from *self or from behind a reference it holds:

use borrow_or_share::BorrowOrShare;

struct Text<T>(T);

impl<'i, 'o, T: BorrowOrShare<'i, 'o, str>> Text<T> {
    fn as_str(&'i self) -> &'o str {
        self.0.borrow_or_share()
    }
}

// The returned reference is borrowed from `*text`
// and lives as long as `text`.
fn borrow(text: &Text<String>) -> &str {
    text.as_str()
}

// The returned reference is borrowed from `*text.0`, lives
// longer than `text` and is said to be shared with `*text`.
fn share<'a>(text: &Text<&'a str>) -> &'a str {
    text.as_str()
}

Credit

Credit goes to @beepster4096 for figuring out a safe version of the code.