How to make a manual future implementation into a async fn

95th · December 22, 2019, 3:24pm

I have this simple Accept Future manually implemented as:

95th/deno/blob/f07ffe89806392698fb8052691b2826f82f15bbe/cli/ops/net.rs#L50-L99


      
          pub struct Accept {
            accept_state: AcceptState,
            rid: ResourceId,
            state: ThreadSafeState,
          }
          
          
impl Future for Accept {
            type Output = Result<(TcpStream, SocketAddr), ErrBox>;
          
          
  fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
              let inner = self.get_mut();
              if inner.accept_state == AcceptState::Done {
                panic!("poll Accept after it's done");
              }
          
          
    let mut table = inner.state.lock_resource_table();
              let listener_resource = table
                .get_mut::<TcpListenerResource>(inner.rid)
                .ok_or_else(|| {
                  let e = std::io::Error::new(

This file has been truncated. show original

I thought (naively) of making it into an async function (and changed the mutex inside lock_resource_table to use Future-aware one from the futures crate.

github.com

95th/deno/blob/d43b5e4c7b2ebd44f76c3ba00e96c4036820d380/cli/ops/net.rs#L24-L39


      
          pub async fn accept(
            state: &ThreadSafeState,
            rid: ResourceId,
          ) -> Result<(TcpStream, SocketAddr), ErrBox> {
            let mut table = state.lock_resource_table_async().await;
            let listener_resource =
              table.get_mut::<TcpListenerResource>(rid).ok_or_else(|| {
                let e = std::io::Error::new(
                  std::io::ErrorKind::Other,
                  "Listener has been closed",
                );
                ErrBox::from(e)
              })?;
          
          
  Ok(listener_resource.listener.accept().await?)
          }

But this doesn't work the same way as original because in the original case the lock was held only when the future was polled but in the latter case, it is held until the accept future resolves.

How can I implement the above future correctly as an async function?

system · March 21, 2020, 3:24pm

This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.

Topic		Replies	Views
Implement Future "async waiting of specific response/body from reqwest" help	3	762	May 30, 2021
How can one implement a Future that returns a non-cloneable argument that was passed into the function that created it help	9	109	April 6, 2025
When will a Future return Pending? help	14	1386	February 5, 2022
Method that accepts future pointer help	2	416	July 30, 2020
[async][futures] Is there a better way to implement this future? help	5	680	January 9, 2020

How to make a manual future implementation into a async fn

Related topics