Add CondVar::wait_{timeout_,}while to debug_sync

These are useful, but we previously couldn't use them due to our
MSRV. Now that we can, we should use them, so we expose them via
our normal debug_sync wrappers.

Author: TheBlueMatt

lightning/src/sync/debug_sync.rs

@@ -26,6 +26,11 @@ impl Backtrace { fn new() -> Backtrace { Backtrace {} } }
 
 pub type LockResult<Guard> = Result<Guard, ()>;
 
+pub struct WaitTimeoutResult(bool);
+impl WaitTimeoutResult {
+	pub fn timed_out(&self) -> bool { self.0 }
+}
+
 pub struct Condvar {
 	inner: StdCondvar,
 }
@@ -40,12 +45,27 @@ impl Condvar {
 		self.inner.wait(guard.into_inner()).map(|lock| MutexGuard { mutex, lock }).map_err(|_| ())
 	}
 
+	pub fn wait_while<'a, T, F: FnMut(&mut T) -> bool>(&'a self, guard: MutexGuard<'a, T>, condition: F)
+	-> LockResult<MutexGuard<'a, T>> {
+		let mutex: &'a Mutex<T> = guard.mutex;
+		self.inner.wait_while(guard.into_inner(), condition).map(|lock| MutexGuard { mutex, lock })
+			.map_err(|_| ())
+	}
+
 	#[allow(unused)]
 	pub fn wait_timeout<'a, T>(&'a self, guard: MutexGuard<'a, T>, dur: Duration) -> LockResult<(MutexGuard<'a, T>, ())> {
 		let mutex = guard.mutex;
 		self.inner.wait_timeout(guard.into_inner(), dur).map(|(lock, _)| (MutexGuard { mutex, lock }, ())).map_err(|_| ())
 	}
 
+	#[allow(unused)]
+	pub fn wait_timeout_while<'a, T, F: FnMut(&mut T) -> bool>(&'a self, guard: MutexGuard<'a, T>, dur: Duration, condition: F)
+	-> LockResult<(MutexGuard<'a, T>, WaitTimeoutResult)> {
+		let mutex = guard.mutex;
+		self.inner.wait_timeout_while(guard.into_inner(), dur, condition).map_err(|_| ())
+			.map(|(lock, e)| (MutexGuard { mutex, lock }, WaitTimeoutResult(e.timed_out())))
+	}
+
 	pub fn notify_all(&self) { self.inner.notify_all(); }
 }