| //! Generic support for building blocking abstractions. |
| |
| use crate::mem; |
| use crate::sync::atomic::{AtomicBool, Ordering}; |
| use crate::sync::Arc; |
| use crate::thread::{self, Thread}; |
| use crate::time::Instant; |
| |
| struct Inner { |
| thread: Thread, |
| woken: AtomicBool, |
| } |
| |
| unsafe impl Send for Inner {} |
| unsafe impl Sync for Inner {} |
| |
| #[derive(Clone)] |
| pub struct SignalToken { |
| inner: Arc<Inner>, |
| } |
| |
| pub struct WaitToken { |
| inner: Arc<Inner>, |
| } |
| |
| impl !Send for WaitToken {} |
| |
| impl !Sync for WaitToken {} |
| |
| pub fn tokens() -> (WaitToken, SignalToken) { |
| let inner = Arc::new(Inner { thread: thread::current(), woken: AtomicBool::new(false) }); |
| let wait_token = WaitToken { inner: inner.clone() }; |
| let signal_token = SignalToken { inner }; |
| (wait_token, signal_token) |
| } |
| |
| impl SignalToken { |
| pub fn signal(&self) -> bool { |
| let wake = !self.inner.woken.compare_and_swap(false, true, Ordering::SeqCst); |
| if wake { |
| self.inner.thread.unpark(); |
| } |
| wake |
| } |
| |
| /// Converts to an unsafe usize value. Useful for storing in a pipe's state |
| /// flag. |
| #[inline] |
| pub unsafe fn cast_to_usize(self) -> usize { |
| mem::transmute(self.inner) |
| } |
| |
| /// Converts from an unsafe usize value. Useful for retrieving a pipe's state |
| /// flag. |
| #[inline] |
| pub unsafe fn cast_from_usize(signal_ptr: usize) -> SignalToken { |
| SignalToken { inner: mem::transmute(signal_ptr) } |
| } |
| } |
| |
| impl WaitToken { |
| pub fn wait(self) { |
| while !self.inner.woken.load(Ordering::SeqCst) { |
| thread::park() |
| } |
| } |
| |
| /// Returns `true` if we wake up normally. |
| pub fn wait_max_until(self, end: Instant) -> bool { |
| while !self.inner.woken.load(Ordering::SeqCst) { |
| let now = Instant::now(); |
| if now >= end { |
| return false; |
| } |
| thread::park_timeout(end - now) |
| } |
| true |
| } |
| } |