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| -rw-r--r-- | third_party/rust/uniffi_core/src/ffi/rustfuture.rs | 735 |
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diff --git a/third_party/rust/uniffi_core/src/ffi/rustfuture.rs b/third_party/rust/uniffi_core/src/ffi/rustfuture.rs deleted file mode 100644 index 0c1a24174b..0000000000 --- a/third_party/rust/uniffi_core/src/ffi/rustfuture.rs +++ /dev/null @@ -1,735 +0,0 @@ -/* This Source Code Form is subject to the terms of the Mozilla Public - * License, v. 2.0. If a copy of the MPL was not distributed with this - * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ - -//! [`RustFuture`] represents a [`Future`] that can be sent to the foreign code over FFI. -//! -//! This type is not instantiated directly, but via the procedural macros, such as `#[uniffi::export]`. -//! -//! # The big picture -//! -//! We implement async foreign functions using a simplified version of the Future API: -//! -//! 0. At startup, register a [RustFutureContinuationCallback] by calling -//! rust_future_continuation_callback_set. -//! 1. Call the scaffolding function to get a [RustFutureHandle] -//! 2a. In a loop: -//! - Call [rust_future_poll] -//! - Suspend the function until the [rust_future_poll] continuation function is called -//! - If the continuation was function was called with [RustFuturePoll::Ready], then break -//! otherwise continue. -//! 2b. If the async function is cancelled, then call [rust_future_cancel]. This causes the -//! continuation function to be called with [RustFuturePoll::Ready] and the [RustFuture] to -//! enter a cancelled state. -//! 3. Call [rust_future_complete] to get the result of the future. -//! 4. Call [rust_future_free] to free the future, ideally in a finally block. This: -//! - Releases any resources held by the future -//! - Calls any continuation callbacks that have not been called yet -//! -//! Note: Technically, the foreign code calls the scaffolding versions of the `rust_future_*` -//! functions. These are generated by the scaffolding macro, specially prefixed, and extern "C", -//! and manually monomorphized in the case of [rust_future_complete]. See -//! `uniffi_macros/src/setup_scaffolding.rs` for details. -//! -//! ## How does `Future` work exactly? -//! -//! A [`Future`] in Rust does nothing. When calling an async function, it just -//! returns a `Future` but nothing has happened yet. To start the computation, -//! the future must be polled. It returns [`Poll::Ready(r)`][`Poll::Ready`] if -//! the result is ready, [`Poll::Pending`] otherwise. `Poll::Pending` basically -//! means: -//! -//! > Please, try to poll me later, maybe the result will be ready! -//! -//! This model is very different than what other languages do, but it can actually -//! be translated quite easily, fortunately for us! -//! -//! But… wait a minute… who is responsible to poll the `Future` if a `Future` does -//! nothing? Well, it's _the executor_. The executor is responsible _to drive_ the -//! `Future`: that's where they are polled. -//! -//! But… wait another minute… how does the executor know when to poll a [`Future`]? -//! Does it poll them randomly in an endless loop? Well, no, actually it depends -//! on the executor! A well-designed `Future` and executor work as follows. -//! Normally, when [`Future::poll`] is called, a [`Context`] argument is -//! passed to it. It contains a [`Waker`]. The [`Waker`] is built on top of a -//! [`RawWaker`] which implements whatever is necessary. Usually, a waker will -//! signal the executor to poll a particular `Future`. A `Future` will clone -//! or pass-by-ref the waker to somewhere, as a callback, a completion, a -//! function, or anything, to the system that is responsible to notify when a -//! task is completed. So, to recap, the waker is _not_ responsible for waking the -//! `Future`, it _is_ responsible for _signaling_ the executor that a particular -//! `Future` should be polled again. That's why the documentation of -//! [`Poll::Pending`] specifies: -//! -//! > When a function returns `Pending`, the function must also ensure that the -//! > current task is scheduled to be awoken when progress can be made. -//! -//! “awakening” is done by using the `Waker`. -//! -//! [`Future`]: https://doc.rust-lang.org/std/future/trait.Future.html -//! [`Future::poll`]: https://doc.rust-lang.org/std/future/trait.Future.html#tymethod.poll -//! [`Pol::Ready`]: https://doc.rust-lang.org/std/task/enum.Poll.html#variant.Ready -//! [`Poll::Pending`]: https://doc.rust-lang.org/std/task/enum.Poll.html#variant.Pending -//! [`Context`]: https://doc.rust-lang.org/std/task/struct.Context.html -//! [`Waker`]: https://doc.rust-lang.org/std/task/struct.Waker.html -//! [`RawWaker`]: https://doc.rust-lang.org/std/task/struct.RawWaker.html - -use std::{ - future::Future, - marker::PhantomData, - mem, - ops::Deref, - panic, - pin::Pin, - sync::{Arc, Mutex}, - task::{Context, Poll, Wake}, -}; - -use crate::{rust_call_with_out_status, FfiDefault, LowerReturn, RustCallStatus}; - -/// Result code for [rust_future_poll]. This is passed to the continuation function. -#[repr(i8)] -#[derive(Debug, PartialEq, Eq)] -pub enum RustFuturePoll { - /// The future is ready and is waiting for [rust_future_complete] to be called - Ready = 0, - /// The future might be ready and [rust_future_poll] should be called again - MaybeReady = 1, -} - -/// Foreign callback that's passed to [rust_future_poll] -/// -/// The Rust side of things calls this when the foreign side should call [rust_future_poll] again -/// to continue progress on the future. -pub type RustFutureContinuationCallback = extern "C" fn(callback_data: *const (), RustFuturePoll); - -/// Opaque handle for a Rust future that's stored by the foreign language code -#[repr(transparent)] -pub struct RustFutureHandle(*const ()); - -// === Public FFI API === - -/// Create a new [RustFutureHandle] -/// -/// For each exported async function, UniFFI will create a scaffolding function that uses this to -/// create the [RustFutureHandle] to pass to the foreign code. -pub fn rust_future_new<F, T, UT>(future: F, tag: UT) -> RustFutureHandle -where - // F is the future type returned by the exported async function. It needs to be Send + `static - // since it will move between threads for an indeterminate amount of time as the foreign - // executor calls polls it and the Rust executor wakes it. It does not need to by `Sync`, - // since we synchronize all access to the values. - F: Future<Output = T> + Send + 'static, - // T is the output of the Future. It needs to implement [LowerReturn]. Also it must be Send + - // 'static for the same reason as F. - T: LowerReturn<UT> + Send + 'static, - // The UniFfiTag ZST. The Send + 'static bound is to keep rustc happy. - UT: Send + 'static, -{ - // Create a RustFuture and coerce to `Arc<dyn RustFutureFfi>`, which is what we use to - // implement the FFI - let future_ffi = RustFuture::new(future, tag) as Arc<dyn RustFutureFfi<T::ReturnType>>; - // Box the Arc, to convert the wide pointer into a normal sized pointer so that we can pass it - // to the foreign code. - let boxed_ffi = Box::new(future_ffi); - // We can now create a RustFutureHandle - RustFutureHandle(Box::into_raw(boxed_ffi) as *mut ()) -} - -/// Poll a Rust future -/// -/// When the future is ready to progress the continuation will be called with the `data` value and -/// a [RustFuturePoll] value. For each [rust_future_poll] call the continuation will be called -/// exactly once. -/// -/// # Safety -/// -/// The [RustFutureHandle] must not previously have been passed to [rust_future_free] -pub unsafe fn rust_future_poll<ReturnType>( - handle: RustFutureHandle, - callback: RustFutureContinuationCallback, - data: *const (), -) { - let future = &*(handle.0 as *mut Arc<dyn RustFutureFfi<ReturnType>>); - future.clone().ffi_poll(callback, data) -} - -/// Cancel a Rust future -/// -/// Any current and future continuations will be immediately called with RustFuturePoll::Ready. -/// -/// This is needed for languages like Swift, which continuation to wait for the continuation to be -/// called when tasks are cancelled. -/// -/// # Safety -/// -/// The [RustFutureHandle] must not previously have been passed to [rust_future_free] -pub unsafe fn rust_future_cancel<ReturnType>(handle: RustFutureHandle) { - let future = &*(handle.0 as *mut Arc<dyn RustFutureFfi<ReturnType>>); - future.clone().ffi_cancel() -} - -/// Complete a Rust future -/// -/// Note: the actually extern "C" scaffolding functions can't be generic, so we generate one for -/// each supported FFI type. -/// -/// # Safety -/// -/// - The [RustFutureHandle] must not previously have been passed to [rust_future_free] -/// - The `T` param must correctly correspond to the [rust_future_new] call. It must -/// be `<Output as LowerReturn<UT>>::ReturnType` -pub unsafe fn rust_future_complete<ReturnType>( - handle: RustFutureHandle, - out_status: &mut RustCallStatus, -) -> ReturnType { - let future = &*(handle.0 as *mut Arc<dyn RustFutureFfi<ReturnType>>); - future.ffi_complete(out_status) -} - -/// Free a Rust future, dropping the strong reference and releasing all references held by the -/// future. -/// -/// # Safety -/// -/// The [RustFutureHandle] must not previously have been passed to [rust_future_free] -pub unsafe fn rust_future_free<ReturnType>(handle: RustFutureHandle) { - let future = Box::from_raw(handle.0 as *mut Arc<dyn RustFutureFfi<ReturnType>>); - future.ffi_free() -} - -/// Thread-safe storage for [RustFutureContinuationCallback] data -/// -/// The basic guarantee is that all data pointers passed in are passed out exactly once to the -/// foreign continuation callback. This enables us to uphold the [rust_future_poll] guarantee. -/// -/// [ContinuationDataCell] also tracks cancellation, which is closely tied to continuation data. -#[derive(Debug)] -enum ContinuationDataCell { - /// No continuations set, neither wake() nor cancel() called. - Empty, - /// `wake()` was called when there was no continuation set. The next time `store` is called, - /// the continuation should be immediately invoked with `RustFuturePoll::MaybeReady` - Waked, - /// The future has been cancelled, any future `store` calls should immediately result in the - /// continuation being called with `RustFuturePoll::Ready`. - Cancelled, - /// Continuation set, the next time `wake()` is called is called, we should invoke it. - Set(RustFutureContinuationCallback, *const ()), -} - -impl ContinuationDataCell { - fn new() -> Self { - Self::Empty - } - - /// Store new continuation data if we are in the `Empty` state. If we are in the `Waked` or - /// `Cancelled` state, call the continuation immediately with the data. - fn store(&mut self, callback: RustFutureContinuationCallback, data: *const ()) { - match self { - Self::Empty => *self = Self::Set(callback, data), - Self::Set(old_callback, old_data) => { - log::error!( - "store: observed `Self::Set` state. Is poll() being called from multiple threads at once?" - ); - old_callback(*old_data, RustFuturePoll::Ready); - *self = Self::Set(callback, data); - } - Self::Waked => { - *self = Self::Empty; - callback(data, RustFuturePoll::MaybeReady); - } - Self::Cancelled => { - callback(data, RustFuturePoll::Ready); - } - } - } - - fn wake(&mut self) { - match self { - // If we had a continuation set, then call it and transition to the `Empty` state. - Self::Set(callback, old_data) => { - let old_data = *old_data; - let callback = *callback; - *self = Self::Empty; - callback(old_data, RustFuturePoll::MaybeReady); - } - // If we were in the `Empty` state, then transition to `Waked`. The next time `store` - // is called, we will immediately call the continuation. - Self::Empty => *self = Self::Waked, - // This is a no-op if we were in the `Cancelled` or `Waked` state. - _ => (), - } - } - - fn cancel(&mut self) { - if let Self::Set(callback, old_data) = mem::replace(self, Self::Cancelled) { - callback(old_data, RustFuturePoll::Ready); - } - } - - fn is_cancelled(&self) -> bool { - matches!(self, Self::Cancelled) - } -} - -// ContinuationDataCell is Send + Sync as long we handle the *const () pointer correctly - -unsafe impl Send for ContinuationDataCell {} -unsafe impl Sync for ContinuationDataCell {} - -/// Wraps the actual future we're polling -struct WrappedFuture<F, T, UT> -where - // See rust_future_new for an explanation of these trait bounds - F: Future<Output = T> + Send + 'static, - T: LowerReturn<UT> + Send + 'static, - UT: Send + 'static, -{ - // Note: this could be a single enum, but that would make it easy to mess up the future pinning - // guarantee. For example you might want to call `std::mem::take()` to try to get the result, - // but if the future happened to be stored that would move and break all internal references. - future: Option<F>, - result: Option<Result<T::ReturnType, RustCallStatus>>, -} - -impl<F, T, UT> WrappedFuture<F, T, UT> -where - // See rust_future_new for an explanation of these trait bounds - F: Future<Output = T> + Send + 'static, - T: LowerReturn<UT> + Send + 'static, - UT: Send + 'static, -{ - fn new(future: F) -> Self { - Self { - future: Some(future), - result: None, - } - } - - // Poll the future and check if it's ready or not - fn poll(&mut self, context: &mut Context<'_>) -> bool { - if self.result.is_some() { - true - } else if let Some(future) = &mut self.future { - // SAFETY: We can call Pin::new_unchecked because: - // - This is the only time we get a &mut to `self.future` - // - We never poll the future after it's moved (for example by using take()) - // - We never move RustFuture, which contains us. - // - RustFuture is private to this module so no other code can move it. - let pinned = unsafe { Pin::new_unchecked(future) }; - // Run the poll and lift the result if it's ready - let mut out_status = RustCallStatus::default(); - let result: Option<Poll<T::ReturnType>> = rust_call_with_out_status( - &mut out_status, - // This closure uses a `&mut F` value, which means it's not UnwindSafe by - // default. If the future panics, it may be in an invalid state. - // - // However, we can safely use `AssertUnwindSafe` since a panic will lead the `None` - // case below and we will never poll the future again. - panic::AssertUnwindSafe(|| match pinned.poll(context) { - Poll::Pending => Ok(Poll::Pending), - Poll::Ready(v) => T::lower_return(v).map(Poll::Ready), - }), - ); - match result { - Some(Poll::Pending) => false, - Some(Poll::Ready(v)) => { - self.future = None; - self.result = Some(Ok(v)); - true - } - None => { - self.future = None; - self.result = Some(Err(out_status)); - true - } - } - } else { - log::error!("poll with neither future nor result set"); - true - } - } - - fn complete(&mut self, out_status: &mut RustCallStatus) -> T::ReturnType { - let mut return_value = T::ReturnType::ffi_default(); - match self.result.take() { - Some(Ok(v)) => return_value = v, - Some(Err(call_status)) => *out_status = call_status, - None => *out_status = RustCallStatus::cancelled(), - } - self.free(); - return_value - } - - fn free(&mut self) { - self.future = None; - self.result = None; - } -} - -// If F and T are Send, then WrappedFuture is too -// -// Rust will not mark it Send by default when T::ReturnType is a raw pointer. This is promising -// that we will treat the raw pointer properly, for example by not returning it twice. -unsafe impl<F, T, UT> Send for WrappedFuture<F, T, UT> -where - // See rust_future_new for an explanation of these trait bounds - F: Future<Output = T> + Send + 'static, - T: LowerReturn<UT> + Send + 'static, - UT: Send + 'static, -{ -} - -/// Future that the foreign code is awaiting -struct RustFuture<F, T, UT> -where - // See rust_future_new for an explanation of these trait bounds - F: Future<Output = T> + Send + 'static, - T: LowerReturn<UT> + Send + 'static, - UT: Send + 'static, -{ - // This Mutex should never block if our code is working correctly, since there should not be - // multiple threads calling [Self::poll] and/or [Self::complete] at the same time. - future: Mutex<WrappedFuture<F, T, UT>>, - continuation_data: Mutex<ContinuationDataCell>, - // UT is used as the generic parameter for [LowerReturn]. - // Let's model this with PhantomData as a function that inputs a UT value. - _phantom: PhantomData<fn(UT) -> ()>, -} - -impl<F, T, UT> RustFuture<F, T, UT> -where - // See rust_future_new for an explanation of these trait bounds - F: Future<Output = T> + Send + 'static, - T: LowerReturn<UT> + Send + 'static, - UT: Send + 'static, -{ - fn new(future: F, _tag: UT) -> Arc<Self> { - Arc::new(Self { - future: Mutex::new(WrappedFuture::new(future)), - continuation_data: Mutex::new(ContinuationDataCell::new()), - _phantom: PhantomData, - }) - } - - fn poll(self: Arc<Self>, callback: RustFutureContinuationCallback, data: *const ()) { - let ready = self.is_cancelled() || { - let mut locked = self.future.lock().unwrap(); - let waker: std::task::Waker = Arc::clone(&self).into(); - locked.poll(&mut Context::from_waker(&waker)) - }; - if ready { - callback(data, RustFuturePoll::Ready) - } else { - self.continuation_data.lock().unwrap().store(callback, data); - } - } - - fn is_cancelled(&self) -> bool { - self.continuation_data.lock().unwrap().is_cancelled() - } - - fn wake(&self) { - self.continuation_data.lock().unwrap().wake(); - } - - fn cancel(&self) { - self.continuation_data.lock().unwrap().cancel(); - } - - fn complete(&self, call_status: &mut RustCallStatus) -> T::ReturnType { - self.future.lock().unwrap().complete(call_status) - } - - fn free(self: Arc<Self>) { - // Call cancel() to send any leftover data to the continuation callback - self.continuation_data.lock().unwrap().cancel(); - // Ensure we drop our inner future, releasing all held references - self.future.lock().unwrap().free(); - } -} - -impl<F, T, UT> Wake for RustFuture<F, T, UT> -where - // See rust_future_new for an explanation of these trait bounds - F: Future<Output = T> + Send + 'static, - T: LowerReturn<UT> + Send + 'static, - UT: Send + 'static, -{ - fn wake(self: Arc<Self>) { - self.deref().wake() - } - - fn wake_by_ref(self: &Arc<Self>) { - self.deref().wake() - } -} - -/// RustFuture FFI trait. This allows `Arc<RustFuture<F, T, UT>>` to be cast to -/// `Arc<dyn RustFutureFfi<T::ReturnType>>`, which is needed to implement the public FFI API. In particular, this -/// allows you to use RustFuture functionality without knowing the concrete Future type, which is -/// unnamable. -/// -/// This is parametrized on the ReturnType rather than the `T` directly, to reduce the number of -/// scaffolding functions we need to generate. If it was parametrized on `T`, then we would need -/// to create a poll, cancel, complete, and free scaffolding function for each exported async -/// function. That would add ~1kb binary size per exported function based on a quick estimate on a -/// x86-64 machine . By parametrizing on `T::ReturnType` we can instead monomorphize by hand and -/// only create those functions for each of the 13 possible FFI return types. -#[doc(hidden)] -trait RustFutureFfi<ReturnType> { - fn ffi_poll(self: Arc<Self>, callback: RustFutureContinuationCallback, data: *const ()); - fn ffi_cancel(&self); - fn ffi_complete(&self, call_status: &mut RustCallStatus) -> ReturnType; - fn ffi_free(self: Arc<Self>); -} - -impl<F, T, UT> RustFutureFfi<T::ReturnType> for RustFuture<F, T, UT> -where - // See rust_future_new for an explanation of these trait bounds - F: Future<Output = T> + Send + 'static, - T: LowerReturn<UT> + Send + 'static, - UT: Send + 'static, -{ - fn ffi_poll(self: Arc<Self>, callback: RustFutureContinuationCallback, data: *const ()) { - self.poll(callback, data) - } - - fn ffi_cancel(&self) { - self.cancel() - } - - fn ffi_complete(&self, call_status: &mut RustCallStatus) -> T::ReturnType { - self.complete(call_status) - } - - fn ffi_free(self: Arc<Self>) { - self.free(); - } -} - -#[cfg(test)] -mod tests { - use super::*; - use crate::{test_util::TestError, Lift, RustBuffer, RustCallStatusCode}; - use once_cell::sync::OnceCell; - use std::task::Waker; - - // Sender/Receiver pair that we use for testing - struct Channel { - result: Option<Result<String, TestError>>, - waker: Option<Waker>, - } - - struct Sender(Arc<Mutex<Channel>>); - - impl Sender { - fn wake(&self) { - let inner = self.0.lock().unwrap(); - if let Some(waker) = &inner.waker { - waker.wake_by_ref(); - } - } - - fn send(&self, value: Result<String, TestError>) { - let mut inner = self.0.lock().unwrap(); - if inner.result.replace(value).is_some() { - panic!("value already sent"); - } - if let Some(waker) = &inner.waker { - waker.wake_by_ref(); - } - } - } - - struct Receiver(Arc<Mutex<Channel>>); - - impl Future for Receiver { - type Output = Result<String, TestError>; - - fn poll( - self: Pin<&mut Self>, - context: &mut Context<'_>, - ) -> Poll<Result<String, TestError>> { - let mut inner = self.0.lock().unwrap(); - match &inner.result { - Some(v) => Poll::Ready(v.clone()), - None => { - inner.waker = Some(context.waker().clone()); - Poll::Pending - } - } - } - } - - // Create a sender and rust future that we can use for testing - fn channel() -> (Sender, Arc<dyn RustFutureFfi<RustBuffer>>) { - let channel = Arc::new(Mutex::new(Channel { - result: None, - waker: None, - })); - let rust_future = RustFuture::new(Receiver(channel.clone()), crate::UniFfiTag); - (Sender(channel), rust_future) - } - - /// Poll a Rust future and get an OnceCell that's set when the continuation is called - fn poll(rust_future: &Arc<dyn RustFutureFfi<RustBuffer>>) -> Arc<OnceCell<RustFuturePoll>> { - let cell = Arc::new(OnceCell::new()); - let cell_ptr = Arc::into_raw(cell.clone()) as *const (); - rust_future.clone().ffi_poll(poll_continuation, cell_ptr); - cell - } - - extern "C" fn poll_continuation(data: *const (), code: RustFuturePoll) { - let cell = unsafe { Arc::from_raw(data as *const OnceCell<RustFuturePoll>) }; - cell.set(code).expect("Error setting OnceCell"); - } - - fn complete(rust_future: Arc<dyn RustFutureFfi<RustBuffer>>) -> (RustBuffer, RustCallStatus) { - let mut out_status_code = RustCallStatus::default(); - let return_value = rust_future.ffi_complete(&mut out_status_code); - (return_value, out_status_code) - } - - #[test] - fn test_success() { - let (sender, rust_future) = channel(); - - // Test polling the rust future before it's ready - let continuation_result = poll(&rust_future); - assert_eq!(continuation_result.get(), None); - sender.wake(); - assert_eq!(continuation_result.get(), Some(&RustFuturePoll::MaybeReady)); - - // Test polling the rust future when it's ready - let continuation_result = poll(&rust_future); - assert_eq!(continuation_result.get(), None); - sender.send(Ok("All done".into())); - assert_eq!(continuation_result.get(), Some(&RustFuturePoll::MaybeReady)); - - // Future polls should immediately return ready - let continuation_result = poll(&rust_future); - assert_eq!(continuation_result.get(), Some(&RustFuturePoll::Ready)); - - // Complete the future - let (return_buf, call_status) = complete(rust_future); - assert_eq!(call_status.code, RustCallStatusCode::Success); - assert_eq!( - <String as Lift<crate::UniFfiTag>>::try_lift(return_buf).unwrap(), - "All done" - ); - } - - #[test] - fn test_error() { - let (sender, rust_future) = channel(); - - let continuation_result = poll(&rust_future); - assert_eq!(continuation_result.get(), None); - sender.send(Err("Something went wrong".into())); - assert_eq!(continuation_result.get(), Some(&RustFuturePoll::MaybeReady)); - - let continuation_result = poll(&rust_future); - assert_eq!(continuation_result.get(), Some(&RustFuturePoll::Ready)); - - let (_, call_status) = complete(rust_future); - assert_eq!(call_status.code, RustCallStatusCode::Error); - unsafe { - assert_eq!( - <TestError as Lift<crate::UniFfiTag>>::try_lift_from_rust_buffer( - call_status.error_buf.assume_init() - ) - .unwrap(), - TestError::from("Something went wrong"), - ) - } - } - - // Once `complete` is called, the inner future should be released, even if wakers still hold a - // reference to the RustFuture - #[test] - fn test_cancel() { - let (_sender, rust_future) = channel(); - - let continuation_result = poll(&rust_future); - assert_eq!(continuation_result.get(), None); - rust_future.ffi_cancel(); - // Cancellation should immediately invoke the callback with RustFuturePoll::Ready - assert_eq!(continuation_result.get(), Some(&RustFuturePoll::Ready)); - - // Future polls should immediately invoke the callback with RustFuturePoll::Ready - let continuation_result = poll(&rust_future); - assert_eq!(continuation_result.get(), Some(&RustFuturePoll::Ready)); - - let (_, call_status) = complete(rust_future); - assert_eq!(call_status.code, RustCallStatusCode::Cancelled); - } - - // Once `free` is called, the inner future should be released, even if wakers still hold a - // reference to the RustFuture - #[test] - fn test_release_future() { - let (sender, rust_future) = channel(); - // Create a weak reference to the channel to use to check if rust_future has dropped its - // future. - let channel_weak = Arc::downgrade(&sender.0); - drop(sender); - // Create an extra ref to rust_future, simulating a waker that still holds a reference to - // it - let rust_future2 = rust_future.clone(); - - // Complete the rust future - rust_future.ffi_free(); - // Even though rust_future is still alive, the channel shouldn't be - assert!(Arc::strong_count(&rust_future2) > 0); - assert_eq!(channel_weak.strong_count(), 0); - assert!(channel_weak.upgrade().is_none()); - } - - // If `free` is called with a continuation still stored, we should call it them then. - // - // This shouldn't happen in practice, but it seems like good defensive programming - #[test] - fn test_complete_with_stored_continuation() { - let (_sender, rust_future) = channel(); - - let continuation_result = poll(&rust_future); - rust_future.ffi_free(); - assert_eq!(continuation_result.get(), Some(&RustFuturePoll::Ready)); - } - - // Test what happens if we see a `wake()` call while we're polling the future. This can - // happen, for example, with futures that are handled by a tokio thread pool. We should - // schedule another poll of the future in this case. - #[test] - fn test_wake_during_poll() { - let mut first_time = true; - let future = std::future::poll_fn(move |ctx| { - if first_time { - first_time = false; - // Wake the future while we are in the middle of polling it - ctx.waker().clone().wake(); - Poll::Pending - } else { - // The second time we're polled, we're ready - Poll::Ready("All done".to_owned()) - } - }); - let rust_future: Arc<dyn RustFutureFfi<RustBuffer>> = - RustFuture::new(future, crate::UniFfiTag); - let continuation_result = poll(&rust_future); - // The continuation function should called immediately - assert_eq!(continuation_result.get(), Some(&RustFuturePoll::MaybeReady)); - // A second poll should finish the future - let continuation_result = poll(&rust_future); - assert_eq!(continuation_result.get(), Some(&RustFuturePoll::Ready)); - let (return_buf, call_status) = complete(rust_future); - assert_eq!(call_status.code, RustCallStatusCode::Success); - assert_eq!( - <String as Lift<crate::UniFfiTag>>::try_lift(return_buf).unwrap(), - "All done" - ); - } -} |