compact-waitgroup 0.1.3

A compact asynchronous WaitGroup synchronization primitive.
Documentation 
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use derive_more::Deref;

use crate::{
    twin_ref::{ClonableTwinRefType, TwinRef, TwinRefType},
    utils::*,
};

struct Canary {
    twin_count: AtomicU8,
    data: AtomicU8,
}

impl Canary {
    fn new() -> Self {
        Self {
            twin_count: AtomicU8::new(2),
            data: AtomicU8::new(0),
        }
    }

    fn load(&self) -> u8 {
        self.data.load(atomic::Relaxed)
    }

    fn set(&self, flag: u8) -> u8 {
        self.data.fetch_or(flag, atomic::Relaxed)
    }
}

unsafe impl TwinRefType for Canary {
    fn count(&self) -> &AtomicU8 {
        &self.twin_count
    }
}

#[derive(Deref)]
struct Data {
    cloned_count: AtomicUsize,
    twin_count: AtomicU8,
    #[deref]
    canary: TwinRef<Canary>,
}

impl Data {
    fn new(canary: TwinRef<Canary>) -> Self {
        Self {
            cloned_count: AtomicUsize::new(1),
            twin_count: AtomicU8::new(2),
            canary,
        }
    }
}

unsafe impl TwinRefType for Data {
    fn count(&self) -> &AtomicU8 {
        &self.twin_count
    }
}

unsafe impl ClonableTwinRefType for Data {
    fn cloned_count(&self) -> &AtomicUsize {
        &self.cloned_count
    }

    fn action_on_zero(&self) {
        self.canary.set(2);
    }
}

impl Drop for Data {
    fn drop(&mut self) {
        self.canary.set(1);
    }
}

#[test]
fn test_twin_ref_mono() {
    loom::model(|| {
        let (canary, inspector) = TwinRef::new_mono(Canary::new());
        assert_eq!(inspector.load(), 0);

        let (a, b) = TwinRef::new_mono(Data::new(canary));
        assert_eq!(inspector.load(), 0);
        assert_eq!(a.load(), 0);
        assert_eq!(b.load(), 0);

        b.set(4);
        assert_eq!(inspector.load(), 4);
        assert_eq!(a.load(), 4);
        assert_eq!(b.load(), 4);

        drop(b);
        assert_eq!(inspector.load(), 4);
        assert_eq!(a.load(), 4);

        drop(a);
        assert_eq!(inspector.load(), 5);
    });
}

#[test]
fn test_twin_ref_clonable() {
    loom::model(|| {
        let (canary, inspector) = TwinRef::new_mono(Canary::new());
        assert_eq!(inspector.load(), 0);

        let (a, b) = TwinRef::new_clonable(Data::new(canary));
        let c = b.clone();
        assert_eq!(inspector.load(), 0);
        assert_eq!(a.load(), 0);
        assert_eq!(b.load(), 0);
        assert_eq!(c.load(), 0);

        b.set(4);
        assert_eq!(inspector.load(), 4);
        assert_eq!(a.load(), 4);
        assert_eq!(b.load(), 4);
        assert_eq!(c.load(), 4);

        drop(c);
        assert_eq!(inspector.load(), 4);
        assert_eq!(a.load(), 4);
        assert_eq!(b.load(), 4);

        drop(b);
        assert_eq!(inspector.load(), 6);
        assert_eq!(a.load(), 6);

        drop(a);
        assert_eq!(inspector.load(), 7);
    });
}