state_lock

StateLock provide a sync primitive that can be used to wait for a state to be ready.

The state type must impl State trait, which contains the tear up and tear down logic to prepare and destroy the state. They you can call the StateLock::lock to obtain the state.

Multi thread could call StateLock::lock at the same time. if the state is ready, the thread would not block, else block until the state is ready.

Usage

use may::go;
use state_lock::{RawState, State, StateLock};

const STATE_FAMILY: &str = "StateIter";

#[derive(State, Default)]
#[family(STATE_FAMILY)]
struct A;

#[derive(State, Default)]
#[family(STATE_FAMILY)]
struct B;

#[derive(State, Default)]
#[family("StateIter")]
struct C;

#[derive(State, Default)]
#[family("StateIter")]
struct D;

trait Test {
    fn hello(&self);
}

impl Test for A {
    fn hello(&self) {
        println!("A is hello");
    }
}

impl Test for B {
    fn hello(&self) {
        println!("B is hello");
    }
}

impl Test for C {
    fn hello(&self) {
        println!("C is hello");
    }
}

impl Test for D {
    fn hello(&self) {
        println!("D is hello");
    }
}

// we have to write this by hand, there is no way to automatically generate those code.
fn as_test<'a>(raw_state: &'a RawState) -> &'a dyn Test {
    match raw_state.name() {
        "A" => raw_state.as_state::<A>() as &dyn Test,
        "B" => raw_state.as_state::<B>() as &dyn Test,
        "C" => raw_state.as_state::<C>() as &dyn Test,
        "D" => raw_state.as_state::<D>() as &dyn Test,
        state_name => panic!("Unknown state: {}", state_name),
    }
}

fn main() {
    env_logger::init();

    use std::sync::Arc;
    let state_lock = Arc::new(StateLock::new(STATE_FAMILY));

    for _ in 0..100 {
        may::coroutine::scope(|scope| {
            for _ in 0..100 {
                state_lock.state_names().for_each(|name| {
                    let state_lock_clone = state_lock.clone();
                    go!(scope, move || {
                        let state = state_lock_clone.lock_by_state_name(name).unwrap();
                        println!("state: {:?} waiting done", state);
                        let test = as_test(&state);
                        test.hello();
                    });
                });
            }
        });
        println!("==============================================================");
    }
}