tag | 2ef16fcc975b86582b48e73b7ba046049f0dea87 | |
---|---|---|
tagger | The Android Open Source Project <initial-contribution@android.com> | Tue May 14 16:44:25 2024 -0700 |
object | eb2b79170ea88c50320e752448ae6205b8b195cb |
Android 14.0.0 release 43
commit | eb2b79170ea88c50320e752448ae6205b8b195cb | [log] [tgz] |
---|---|---|
author | Matthew Maurer <mmaurer@google.com> | Thu Mar 09 18:07:14 2023 +0000 |
committer | Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com> | Thu Mar 09 18:07:14 2023 +0000 |
tree | 12c59a21225d1e0948cd3b4c7db5e10c2aec25e6 | |
parent | 24b33bc54334e8b8fca9badb02cddad3ffa33069 [diff] | |
parent | ef448c2b5be6605dcd317ccee0827ad2206dd755 [diff] |
Make once_cell available to product and vendor am: a7bb59bc1a am: 99bf616a5f am: 5d3c9a7e9c am: ef448c2b5b Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/once_cell/+/2476446 Change-Id: I398c0785797a242a36dadf99b3b23219b84c337e Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
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
.