| commit | 1da3db55c968861a587abbe8b29659537a7bbaee | [log] [tgz] |
|---|---|---|
| author | Jeff Vander Stoep <jeffv@google.com> | Thu Feb 16 15:42:21 2023 +0100 |
| committer | Jeff Vander Stoep <jeffv@google.com> | Thu Feb 16 15:42:21 2023 +0100 |
| tree | f0df62c2365cf1af4985701b56e920f31df686ec | |
| parent | c78c9dff44a4f09e9f32272ff362260f4dabce01 [diff] |
Upgrade once_cell to 1.17.1 This project was upgraded with external_updater. Usage: tools/external_updater/updater.sh update rust/crates/once_cell For more info, check https://cs.android.com/android/platform/superproject/+/master:tools/external_updater/README.md Test: TreeHugger Change-Id: I714361ebe227bfb157b33f5000ae8c963ebc1fc6
once_cell provides two new cell-like types, unsync::OnceCell and sync::OnceCell. OnceCell might store arbitrary non-Copy types, can be assigned to at most once and provide direct access to the stored contents. In a nutshell, API looks roughly like this:
impl OnceCell<T> { fn new() -> OnceCell<T> { ... } fn set(&self, value: T) -> Result<(), T> { ... } fn get(&self) -> Option<&T> { ... } }
Note that, like with RefCell and Mutex, the set method requires only a shared reference. Because of the single assignment restriction get can return an &T instead of Ref<T> or MutexGuard<T>.
once_cell also has a Lazy<T> type, build on top of OnceCell which provides the same API as the lazy_static! macro, but without using any macros:
use std::{sync::Mutex, collections::HashMap}; use once_cell::sync::Lazy; static GLOBAL_DATA: Lazy<Mutex<HashMap<i32, String>>> = Lazy::new(|| { let mut m = HashMap::new(); m.insert(13, "Spica".to_string()); m.insert(74, "Hoyten".to_string()); Mutex::new(m) }); fn main() { println!("{:?}", GLOBAL_DATA.lock().unwrap()); }
More patterns and use-cases are in the docs!
The API of once_cell is being proposed for inclusion in std.