比较 Rust 中异步操作的句柄与流。

huangapple
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英文:

Comparing handles vs streams for async operations in rust

问题

In rust, we can write a vector of handles that allows to have asynchronous operation without blocking:

  1. use tokio;
  3. #[derive(Clone)]
  4. struct Cont {
  5.     delta: usize,
  6. }
  8. impl Cont {
  9.     fn get(&mut self) -> usize {
  10.         self.delta
  11.     }
  12. }
  14. #[tokio::main]
  15. async fn main() {
  16.     let delta = 3;
  17.     let cont = Cont { delta };
  18.     let mut handles = Vec::new();
  19.     for i in 0..10 {
  20.         let mut cont = cont.clone();
  21.         handles.push(tokio::spawn(async move {
  22.             cont.get() + i.clone()
  23.         }));
  24.     }
  25.     let _response = futures::future::join_all(handles).await;
  26. }

But this builds a vector of handles which might be considered a negative.

The stream version would replace the main with

  1. #[tokio::main]
  2. async fn main() {
  3.     let delta = 3;
  4.     let cont = Cont { delta };
  5.     let stream = stream::iter(0..10).then(|i| async move {
  6.         cont.clone().get() + i.clone()
  7.     });
  8.     let _result : Vec<usize> = stream.collect().await;
  9. }

Unfortunately, it does not compile.

So my questions are the following:

  • Is it possible to have the stream version of the code working correctly, that is, is there a way to clone the cont?
  • Apart from the building of a vector of handles, which does not occur in the stream version, are both versions the same? I mean, are they both based on green threads?
英文:

In rust, we can write a vector of handles that allows to have asynchronous operation without blocking:

  1. use tokio;
  3. #[derive(Clone)]
  4. struct Cont {
  5.     delta: usize,
  6. }
  8. impl Cont {
  9.     fn get(&amp;mut self) -&gt; usize {
  10.         self.delta
  11.     }
  12. }
  14. #[tokio::main]
  15. async fn main() {
  16.     let delta = 3;
  17.     let cont = Cont { delta };
  18.     let mut handles = Vec::new();
  19.     for i in 0..10 {
  20.         let mut cont = cont.clone();
  21.         handles.push(tokio::spawn(async move {
  22.             cont.get() + i.clone()
  23.         }));
  24.     }
  25.     let _response = futures::future::join_all(handles).await;
  26. }

But this builds a vector of handles which might be considered a negative.

The stream version would replace the main with

  1. #[tokio::main]
  2. async fn main() {
  3.     let delta = 3;
  4.     let cont = Cont { delta };
  5.     let stream = stream::iter(0..10).then(|i| async move {
  6.         cont.clone().get() + i.clone()
  7.     });
  8.     let _result : Vec&lt;usize&gt; = stream.collect().await;
  9. }

Unfortunately, it does not compile.

So my questions are the following:

  • Is it possible to have the stream version of the code working correctly, that is, is there a way to clone the cont?
  • Apart from the building of a vector of handles, which does not occur in the stream version, are both versions the same? I mean, are they both based on green threads?

答案1

得分: 1

Sure, here's the translated code portion:

是的，可以做到：

  1. fn main() {
  2.     let delta = 3;
  3.     let cont = Cont { delta };
  4.     let stream = futures::stream::iter(0..10).then(move |i| {
  5.         let mut cont = cont.clone();
  6.         async move { cont.get() + i.clone() }
  7.     });
  8.     let _result: Vec<usize> = stream.collect().await;
  9. }

基本上只需在闭包中克隆 cont，然后将其移动到异步块中。

是的，它们在功能上是等效的。

英文:

Yup, it's doable:

  1. fn main() {
  2.     let delta = 3;
  3.     let cont = Cont { delta };
  4.     let stream = futures::stream::iter(0..10).then(move |i| {
  5.         let mut cont = cont.clone();
  6.         async move { cont.get() + i.clone() }
  7.     });
  8.     let _result: Vec&lt;usize&gt; = stream.collect().await;
  9. }

Basically just clone the cont in the closure and then move it to the async block.

And yes, they are functionally equivalent.

huangapple
  • 本文由 发表于 2023年5月13日 19:52:06
  • 转载请务必保留本文链接：https://go.coder-hub.com/76242578.html
  • async-await
  • asynchronous
  • rust
  • rust-tokio
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