1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44

use std::sync::atomic::Ordering;
use crate::rw_lock_cycler::RwLockCycler;
use crate::traits::{CyclerReader, EnsureSend, EnsureSync, ReadAccess};
use parking_lot::{RwLock, RwLockReadGuard};

#[cfg(feature = "unsafe_cleanup")]
use crate::static_ref_holder::StaticRefHolder;
#[cfg(feature = "unsafe_cleanup")]
use std::sync::Arc;

/// The reader for an `RwLockCycler`
#[derive(Debug)]
pub struct RwLockCyclerReader<T> where T: 'static {
    pub(super) cycler: &'static RwLockCycler<T>,
    pub(super) reader: Option<RwLockReadGuard<'static, T>>,
    #[allow(dead_code)]
    #[cfg(feature = "unsafe_cleanup")]
    pub(super) ref_holder: Arc<StaticRefHolder<RwLockCycler<T>>>,
}
impl<T> EnsureSend for RwLockCyclerReader<T> where T: Send + Sync {}
impl<T> EnsureSync for RwLockCyclerReader<T> where T: Send + Sync {}
impl<T> ReadAccess for RwLockCyclerReader<T> where T: ReadAccess {
    type Read = T::Read;

    #[inline]
    fn read_data(&self) -> &Self::Read {
        // Reader should never be None except inside of read_latest
        self.reader.as_ref().unwrap().read_data()
    }
}
impl<T> CyclerReader<T> for RwLockCyclerReader<T> where T: ReadAccess {
    fn read_latest(&mut self) {
        drop(self.reader.take());
        let mut most_up_to_date = self.cycler.most_up_to_date.load(Ordering::Relaxed);
        loop {
            if let Some(reader) = RwLock::try_read(&self.cycler.data_slots[most_up_to_date as usize]) {
                self.reader = Some(reader);
                return;
            } else {
                most_up_to_date = self.cycler.most_up_to_date.load(Ordering::Relaxed);
            }
        }
    }
}