src/tools/futures.rs: switch to async

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

src/tools/futures.rs

@@ -1,11 +1,14 @@
 //! Provides utilities to deal with futures, such as a `Cancellable` future.
 
+use std::future::Future;
+use std::pin::Pin;
 use std::sync::{Arc, Mutex};
+use std::task::{Context, Poll};
 
 use failure::Error;
-use futures::{Async, Future, Poll};
+use futures::future::FutureExt;
 
-use crate::tools::async_mutex::{AsyncMutex, AsyncLockGuard, LockFuture};
+use crate::tools::async_mutex::{AsyncLockGuard, AsyncMutex, LockFuture};
 
 /// Make a future cancellable.
 ///
@@ -16,30 +19,30 @@ use crate::tools::async_mutex::{AsyncMutex, AsyncLockGuard, LockFuture};
 /// In order to cancel the future, a `Canceller` is used.
 ///
 /// ```no_run
+/// # use std::future::Future;
 /// # use failure::Error;
-/// # use futures::Future;
+/// # use futures::future::FutureExt;
 /// # use proxmox_backup::tools::futures::Cancellable;
 /// # fn doc<T>(future: T) -> Result<(), Error>
 /// # where
-/// #     T: Future<Item = i32, Error = ()> + Send + Sync + 'static,
+/// #     T: Future<Output = i32> + Unpin + Send + Sync + 'static,
 /// # {
 /// let (future, canceller) = Cancellable::new(future)?;
-/// tokio::spawn(future.and_then(|res| {
+/// tokio::spawn(future.map(|res| {
 ///     match res {
 ///         Some(value) => println!("Future finished with {}", value),
 ///         None => println!("Future was cancelled"),
 ///     }
-///     Ok(())
 /// }));
 /// // Do something
 /// canceller.cancel();
 /// # Ok(())
 /// # }
 /// ```
-pub struct Cancellable<T: Future> {
+pub struct Cancellable<T: Future + Unpin> {
     /// Our core: we're waiting on a future, on on a lock. The cancel method just unlocks the
     /// lock, so that our LockFuture finishes.
-    inner: futures::future::Select2<T, LockFuture<(), <T as Future>::Error>>,
+    inner: futures::future::Select<T, LockFuture<()>>,
 
     /// When this future is created, this holds a guard. When a `Canceller` wants to cancel the
     /// future, it'll drop this guard, causing our inner future to resolve to `None`.
@@ -63,7 +66,7 @@ impl Canceller {
     }
 }
 
-impl<T: Future> Cancellable<T> {
+impl<T: Future + Unpin> Cancellable<T> {
     /// Make a future cancellable.
     ///
     /// Returns a future and a `Canceller` which can be cloned and used later to cancel the future.
@@ -71,7 +74,7 @@ impl<T: Future> Cancellable<T> {
         // we don't even need to sture the mutex...
         let (mutex, guard) = AsyncMutex::new_locked(())?;
         let this = Self {
-            inner: inner.select2(mutex.lock()),
+            inner: futures::future::select(inner, mutex.lock()),
             guard: Arc::new(Mutex::new(Some(guard))),
         };
         let canceller = this.canceller();
@@ -87,22 +90,18 @@ impl<T: Future> Cancellable<T> {
 /// Make a future cancellable.
 ///
 /// This is a shortcut for `Cancellable::new`
-pub fn cancellable<T: Future>(future: T) -> Result<(Cancellable<T>, Canceller), Error> {
+pub fn cancellable<T: Future + Unpin>(future: T) -> Result<(Cancellable<T>, Canceller), Error> {
     Cancellable::new(future)
 }
 
-impl<T: Future> Future for Cancellable<T> {
-    type Item = Option<<T as Future>::Item>;
-    type Error = <T as Future>::Error;
-
-    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
+impl<T: Future + Unpin> Future for Cancellable<T> {
+    type Output = Option<<T as Future>::Output>;
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
         use futures::future::Either;
-        match self.inner.poll() {
-            Ok(Async::Ready(Either::A((item, _)))) => Ok(Async::Ready(Some(item))),
-            Ok(Async::Ready(Either::B(_))) => Ok(Async::Ready(None)),
-            Ok(Async::NotReady) => Ok(Async::NotReady),
-            Err(Either::A((err, _))) => Err(err),
-            Err(Either::B((err, _))) => Err(err),
+        match self.inner.poll_unpin(cx) {
+            Poll::Ready(Either::Left((output, _))) => Poll::Ready(Some(output)),
+            Poll::Ready(Either::Right(_)) => Poll::Ready(None),
+            Poll::Pending => Poll::Pending,
         }
     }
 }