wasmer_wasix/fs/
notification.rs

1use std::{
2    collections::VecDeque,
3    sync::Mutex,
4    task::{Poll, Waker},
5};
6
7use virtual_mio::{InterestHandler, InterestType};
8
9#[derive(Debug)]
10#[cfg_attr(feature = "enable-serde", derive(Serialize, Deserialize))]
11struct NotificationState {
12    /// Used for event notifications by the user application or operating system
13    /// (positive number means there are events waiting to be processed)
14    counter: u64,
15    /// Counter used to prevent duplicate notification events
16    last_poll: u64,
17    /// Flag that indicates if this is operating
18    is_semaphore: bool,
19    /// All the registered wakers
20    #[cfg_attr(feature = "enable-serde", serde(skip))]
21    wakers: VecDeque<Waker>,
22    /// InterestHandler for use with epoll
23    #[cfg_attr(feature = "enable-serde", serde(skip))]
24    interest_handler: Option<Box<dyn InterestHandler>>,
25}
26
27impl NotificationState {
28    fn add_waker(&mut self, waker: &Waker) {
29        if !self.wakers.iter().any(|a| a.will_wake(waker)) {
30            self.wakers.push_front(waker.clone());
31        }
32    }
33
34    fn wake_all(&mut self) {
35        self.last_poll = u64::MAX;
36        while let Some(waker) = self.wakers.pop_front() {
37            waker.wake();
38        }
39        if let Some(handler) = self.interest_handler.as_mut() {
40            handler.push_interest(InterestType::Readable);
41        }
42    }
43
44    fn inc(&mut self, val: u64) {
45        self.counter += val;
46        self.wake_all();
47    }
48
49    fn dec(&mut self) -> u64 {
50        let val = self.counter;
51        if self.is_semaphore {
52            if self.counter > 0 {
53                self.counter -= 1;
54                if self.counter > 0 {
55                    self.wake_all();
56                }
57            }
58        } else {
59            self.counter = 0;
60        }
61        val
62    }
63}
64
65#[derive(Debug)]
66#[cfg_attr(feature = "enable-serde", derive(Serialize, Deserialize))]
67pub struct NotificationInner {
68    /// Receiver that wakes sleeping threads
69    #[cfg_attr(feature = "enable-serde", serde(skip))]
70    state: Mutex<NotificationState>,
71}
72
73impl NotificationInner {
74    pub fn new(initial_val: u64, is_semaphore: bool) -> Self {
75        Self {
76            state: Mutex::new(NotificationState {
77                counter: initial_val,
78                last_poll: u64::MAX,
79                is_semaphore,
80                wakers: Default::default(),
81                interest_handler: None,
82            }),
83        }
84    }
85    pub fn poll(&self, waker: &Waker) -> Poll<usize> {
86        let mut state = self.state.lock().unwrap();
87        state.add_waker(waker);
88
89        if state.last_poll != state.counter {
90            state.last_poll = state.counter;
91            Poll::Ready(state.counter as usize)
92        } else {
93            Poll::Pending
94        }
95    }
96
97    pub fn write(&self, val: u64) {
98        let mut state = self.state.lock().unwrap();
99        state.inc(val);
100    }
101
102    pub fn read(&self, waker: &Waker) -> Poll<u64> {
103        let mut state = self.state.lock().unwrap();
104        state.add_waker(waker);
105        match state.dec() {
106            0 => Poll::Pending,
107            res => Poll::Ready(res),
108        }
109    }
110
111    pub fn try_read(&self) -> Option<u64> {
112        let mut state = self.state.lock().unwrap();
113        match state.dec() {
114            0 => None,
115            res => Some(res),
116        }
117    }
118
119    pub fn reset(&self) {
120        let mut state = self.state.lock().unwrap();
121        state.last_poll = u64::MAX;
122    }
123
124    pub fn set_interest_handler(&self, handler: Box<dyn InterestHandler>) {
125        let mut state = self.state.lock().unwrap();
126        state.interest_handler.replace(handler);
127    }
128
129    pub fn remove_interest_handler(&self) -> Option<Box<dyn InterestHandler>> {
130        let mut state = self.state.lock().unwrap();
131        state.interest_handler.take()
132    }
133}
wasmer_wasix/fs/notification.rs

wasmer_wasix/fs/
notification.rs
