From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 14:02:58 +0200 Subject: Adding upstream version 1.64.0+dfsg1. Signed-off-by: Daniel Baumann --- vendor/once_cell/README.md | 56 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 56 insertions(+) create mode 100644 vendor/once_cell/README.md (limited to 'vendor/once_cell/README.md') diff --git a/vendor/once_cell/README.md b/vendor/once_cell/README.md new file mode 100644 index 000000000..de65dbbcc --- /dev/null +++ b/vendor/once_cell/README.md @@ -0,0 +1,56 @@ +

once_cell

+ + +[![Build Status](https://github.com/matklad/once_cell/actions/workflows/ci.yaml/badge.svg)](https://github.com/matklad/once_cell/actions) +[![Crates.io](https://img.shields.io/crates/v/once_cell.svg)](https://crates.io/crates/once_cell) +[![API reference](https://docs.rs/once_cell/badge.svg)](https://docs.rs/once_cell/) + +# Overview + +`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: + +```rust +impl OnceCell { + fn new() -> OnceCell { ... } + 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` +or `MutexGuard`. + +`once_cell` also has a `Lazy` type, build on top of `OnceCell` which provides the same API as +the `lazy_static!` macro, but without using any macros: + +```rust +use std::{sync::Mutex, collections::HashMap}; +use once_cell::sync::Lazy; + +static GLOBAL_DATA: Lazy>> = 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](https://docs.rs/once_cell/)! + +# Related crates + +* [double-checked-cell](https://github.com/niklasf/double-checked-cell) +* [lazy-init](https://crates.io/crates/lazy-init) +* [lazycell](https://crates.io/crates/lazycell) +* [mitochondria](https://crates.io/crates/mitochondria) +* [lazy_static](https://crates.io/crates/lazy_static) + +The API of `once_cell` is being proposed for inclusion in +[`std`](https://github.com/rust-lang/rfcs/pull/2788). -- cgit v1.2.3