trixy/src/lib.rs

pub mod types {
    pub use trixy_types::*;
}

pub mod macros {
    pub use trixy_macros::*;
}

pub mod oneshot {
    //! This module provides a synced version of tokio's oneshot channel.
    //! Notably this is implemented as wrapper around std's mpsc channel, which closes after one received value
    use std::{
        mem,
        sync::mpsc::{self, RecvError, SendError, TryRecvError},
    };

    #[derive(Clone, Debug)]
    pub struct Sender<T> {
        channel: mpsc::Sender<T>,
    }
    #[derive(Debug)]
    pub struct Receiver<T> {
        channel: mpsc::Receiver<T>,
        last_value: Option<T>,
    }

    pub fn channel<T>() -> (Sender<T>, Receiver<T>) {
        let (tx, rx) = mpsc::channel();
        (
            Sender { channel: tx },
            Receiver {
                channel: rx,
                last_value: None,
            },
        )
    }
    impl<T> Sender<T> {
        pub fn send(&self, input: T) -> Result<(), SendError<T>> {
            self.channel.send(input)
        }
    }
    impl<T> Receiver<T> {
        pub fn try_recv(&mut self) -> Result<bool, TryRecvError> {
            match self.channel.try_recv() {
                Ok(ok) => {
                    self.close();
                    self.last_value = Some(ok);
                    Ok(true)
                }
                Err(err) => Err(err),
            }
        }

        pub fn close(&mut self) {
            let (_, recv) = mpsc::channel();
            let channel = mem::replace(&mut self.channel, recv);
            drop(channel);
        }

        pub fn recv(mut self) -> Result<T, RecvError> {
            match self.channel.recv() {
                Ok(ok) => {
                    self.close();
                    Ok(ok)
                }
                Err(err) => {
                    if let Some(val) = self.last_value {
                        Ok(val)
                    } else {
                        Err(err)
                    }
                }
            }
        }
    }
}