| commit | 05c782f3199c27909fbb4ced6dcc9367158b46a6 | [log] [tgz] |
|---|---|---|
| author | Android Build Coastguard Worker <android-build-coastguard-worker@google.com> | Wed Nov 22 21:41:31 2023 +0000 |
| committer | Android Build Coastguard Worker <android-build-coastguard-worker@google.com> | Wed Nov 22 21:41:31 2023 +0000 |
| tree | f1e300fd061c117d42ca0da249952f2a1ba267b2 | |
| parent | f14edac6a697f481be2359588fd942e2bad4a62e [diff] | |
| parent | 73154adc132e8b8b45cd7c6682d9dd3058332841 [diff] |
Snap for 11135399 from 73154adc132e8b8b45cd7c6682d9dd3058332841 to simpleperf-release Change-Id: Ib4178a9ad7405e247c1bc1571b15cdbf1f009bf8
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.