diff options
Diffstat (limited to 'embassy-sync/src/pipe.rs')
| -rw-r--r-- | embassy-sync/src/pipe.rs | 551 |
1 files changed, 551 insertions, 0 deletions
diff --git a/embassy-sync/src/pipe.rs b/embassy-sync/src/pipe.rs new file mode 100644 index 00000000..7d64b648 --- /dev/null +++ b/embassy-sync/src/pipe.rs @@ -0,0 +1,551 @@ +//! Async byte stream pipe. + +use core::cell::RefCell; +use core::future::Future; +use core::pin::Pin; +use core::task::{Context, Poll}; + +use crate::blocking_mutex::raw::RawMutex; +use crate::blocking_mutex::Mutex; +use crate::ring_buffer::RingBuffer; +use crate::waitqueue::WakerRegistration; + +/// Write-only access to a [`Pipe`]. +#[derive(Copy)] +pub struct Writer<'p, M, const N: usize> +where + M: RawMutex, +{ + pipe: &'p Pipe<M, N>, +} + +impl<'p, M, const N: usize> Clone for Writer<'p, M, N> +where + M: RawMutex, +{ + fn clone(&self) -> Self { + Writer { pipe: self.pipe } + } +} + +impl<'p, M, const N: usize> Writer<'p, M, N> +where + M: RawMutex, +{ + /// Writes a value. + /// + /// See [`Pipe::write()`] + pub fn write<'a>(&'a self, buf: &'a [u8]) -> WriteFuture<'a, M, N> { + self.pipe.write(buf) + } + + /// Attempt to immediately write a message. + /// + /// See [`Pipe::write()`] + pub fn try_write(&self, buf: &[u8]) -> Result<usize, TryWriteError> { + self.pipe.try_write(buf) + } +} + +/// Future returned by [`Pipe::write`] and [`Writer::write`]. +pub struct WriteFuture<'p, M, const N: usize> +where + M: RawMutex, +{ + pipe: &'p Pipe<M, N>, + buf: &'p [u8], +} + +impl<'p, M, const N: usize> Future for WriteFuture<'p, M, N> +where + M: RawMutex, +{ + type Output = usize; + + fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> { + match self.pipe.try_write_with_context(Some(cx), self.buf) { + Ok(n) => Poll::Ready(n), + Err(TryWriteError::Full) => Poll::Pending, + } + } +} + +impl<'p, M, const N: usize> Unpin for WriteFuture<'p, M, N> where M: RawMutex {} + +/// Read-only access to a [`Pipe`]. +#[derive(Copy)] +pub struct Reader<'p, M, const N: usize> +where + M: RawMutex, +{ + pipe: &'p Pipe<M, N>, +} + +impl<'p, M, const N: usize> Clone for Reader<'p, M, N> +where + M: RawMutex, +{ + fn clone(&self) -> Self { + Reader { pipe: self.pipe } + } +} + +impl<'p, M, const N: usize> Reader<'p, M, N> +where + M: RawMutex, +{ + /// Reads a value. + /// + /// See [`Pipe::read()`] + pub fn read<'a>(&'a self, buf: &'a mut [u8]) -> ReadFuture<'a, M, N> { + self.pipe.read(buf) + } + + /// Attempt to immediately read a message. + /// + /// See [`Pipe::read()`] + pub fn try_read(&self, buf: &mut [u8]) -> Result<usize, TryReadError> { + self.pipe.try_read(buf) + } +} + +/// Future returned by [`Pipe::read`] and [`Reader::read`]. +pub struct ReadFuture<'p, M, const N: usize> +where + M: RawMutex, +{ + pipe: &'p Pipe<M, N>, + buf: &'p mut [u8], +} + +impl<'p, M, const N: usize> Future for ReadFuture<'p, M, N> +where + M: RawMutex, +{ + type Output = usize; + + fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> { + match self.pipe.try_read_with_context(Some(cx), self.buf) { + Ok(n) => Poll::Ready(n), + Err(TryReadError::Empty) => Poll::Pending, + } + } +} + +impl<'p, M, const N: usize> Unpin for ReadFuture<'p, M, N> where M: RawMutex {} + +/// Error returned by [`try_read`](Pipe::try_read). +#[derive(PartialEq, Eq, Clone, Copy, Debug)] +#[cfg_attr(feature = "defmt", derive(defmt::Format))] +pub enum TryReadError { + /// No data could be read from the pipe because it is currently + /// empty, and reading would require blocking. + Empty, +} + +/// Error returned by [`try_write`](Pipe::try_write). +#[derive(PartialEq, Eq, Clone, Copy, Debug)] +#[cfg_attr(feature = "defmt", derive(defmt::Format))] +pub enum TryWriteError { + /// No data could be written to the pipe because it is + /// currently full, and writing would require blocking. + Full, +} + +struct PipeState<const N: usize> { + buffer: RingBuffer<N>, + read_waker: WakerRegistration, + write_waker: WakerRegistration, +} + +impl<const N: usize> PipeState<N> { + const fn new() -> Self { + PipeState { + buffer: RingBuffer::new(), + read_waker: WakerRegistration::new(), + write_waker: WakerRegistration::new(), + } + } + + fn clear(&mut self) { + self.buffer.clear(); + self.write_waker.wake(); + } + + fn try_read(&mut self, buf: &mut [u8]) -> Result<usize, TryReadError> { + self.try_read_with_context(None, buf) + } + + fn try_read_with_context(&mut self, cx: Option<&mut Context<'_>>, buf: &mut [u8]) -> Result<usize, TryReadError> { + if self.buffer.is_full() { + self.write_waker.wake(); + } + + let available = self.buffer.pop_buf(); + if available.is_empty() { + if let Some(cx) = cx { + self.read_waker.register(cx.waker()); + } + return Err(TryReadError::Empty); + } + + let n = available.len().min(buf.len()); + buf[..n].copy_from_slice(&available[..n]); + self.buffer.pop(n); + Ok(n) + } + + fn try_write(&mut self, buf: &[u8]) -> Result<usize, TryWriteError> { + self.try_write_with_context(None, buf) + } + + fn try_write_with_context(&mut self, cx: Option<&mut Context<'_>>, buf: &[u8]) -> Result<usize, TryWriteError> { + if self.buffer.is_empty() { + self.read_waker.wake(); + } + + let available = self.buffer.push_buf(); + if available.is_empty() { + if let Some(cx) = cx { + self.write_waker.register(cx.waker()); + } + return Err(TryWriteError::Full); + } + + let n = available.len().min(buf.len()); + available[..n].copy_from_slice(&buf[..n]); + self.buffer.push(n); + Ok(n) + } +} + +/// A bounded pipe for communicating between asynchronous tasks +/// with backpressure. +/// +/// The pipe will buffer up to the provided number of messages. Once the +/// buffer is full, attempts to `write` new messages will wait until a message is +/// read from the pipe. +/// +/// All data written will become available in the same order as it was written. +pub struct Pipe<M, const N: usize> +where + M: RawMutex, +{ + inner: Mutex<M, RefCell<PipeState<N>>>, +} + +impl<M, const N: usize> Pipe<M, N> +where + M: RawMutex, +{ + /// Establish a new bounded pipe. For example, to create one with a NoopMutex: + /// + /// ``` + /// use embassy_sync::pipe::Pipe; + /// use embassy_sync::blocking_mutex::raw::NoopRawMutex; + /// + /// // Declare a bounded pipe, with a buffer of 256 bytes. + /// let mut pipe = Pipe::<NoopRawMutex, 256>::new(); + /// ``` + pub const fn new() -> Self { + Self { + inner: Mutex::new(RefCell::new(PipeState::new())), + } + } + + fn lock<R>(&self, f: impl FnOnce(&mut PipeState<N>) -> R) -> R { + self.inner.lock(|rc| f(&mut *rc.borrow_mut())) + } + + fn try_read_with_context(&self, cx: Option<&mut Context<'_>>, buf: &mut [u8]) -> Result<usize, TryReadError> { + self.lock(|c| c.try_read_with_context(cx, buf)) + } + + fn try_write_with_context(&self, cx: Option<&mut Context<'_>>, buf: &[u8]) -> Result<usize, TryWriteError> { + self.lock(|c| c.try_write_with_context(cx, buf)) + } + + /// Get a writer for this pipe. + pub fn writer(&self) -> Writer<'_, M, N> { + Writer { pipe: self } + } + + /// Get a reader for this pipe. + pub fn reader(&self) -> Reader<'_, M, N> { + Reader { pipe: self } + } + + /// Write a value, waiting until there is capacity. + /// + /// Writeing completes when the value has been pushed to the pipe's queue. + /// This doesn't mean the value has been read yet. + pub fn write<'a>(&'a self, buf: &'a [u8]) -> WriteFuture<'a, M, N> { + WriteFuture { pipe: self, buf } + } + + /// Attempt to immediately write a message. + /// + /// This method differs from [`write`](Pipe::write) by returning immediately if the pipe's + /// buffer is full, instead of waiting. + /// + /// # Errors + /// + /// If the pipe capacity has been reached, i.e., the pipe has `n` + /// buffered values where `n` is the argument passed to [`Pipe`], then an + /// error is returned. + pub fn try_write(&self, buf: &[u8]) -> Result<usize, TryWriteError> { + self.lock(|c| c.try_write(buf)) + } + + /// Receive the next value. + /// + /// If there are no messages in the pipe's buffer, this method will + /// wait until a message is written. + pub fn read<'a>(&'a self, buf: &'a mut [u8]) -> ReadFuture<'a, M, N> { + ReadFuture { pipe: self, buf } + } + + /// Attempt to immediately read a message. + /// + /// This method will either read a message from the pipe immediately or return an error + /// if the pipe is empty. + pub fn try_read(&self, buf: &mut [u8]) -> Result<usize, TryReadError> { + self.lock(|c| c.try_read(buf)) + } + + /// Clear the data in the pipe's buffer. + pub fn clear(&self) { + self.lock(|c| c.clear()) + } + + /// Return whether the pipe is full (no free space in the buffer) + pub fn is_full(&self) -> bool { + self.len() == N + } + + /// Return whether the pipe is empty (no data buffered) + pub fn is_empty(&self) -> bool { + self.len() == 0 + } + + /// Total byte capacity. + /// + /// This is the same as the `N` generic param. + pub fn capacity(&self) -> usize { + N + } + + /// Used byte capacity. + pub fn len(&self) -> usize { + self.lock(|c| c.buffer.len()) + } + + /// Free byte capacity. + /// + /// This is equivalent to `capacity() - len()` + pub fn free_capacity(&self) -> usize { + N - self.len() + } +} + +#[cfg(feature = "nightly")] +mod io_impls { + use core::convert::Infallible; + + use futures_util::FutureExt; + + use super::*; + + impl<M: RawMutex, const N: usize> embedded_io::Io for Pipe<M, N> { + type Error = Infallible; + } + + impl<M: RawMutex, const N: usize> embedded_io::asynch::Read for Pipe<M, N> { + type ReadFuture<'a> = impl Future<Output = Result<usize, Self::Error>> + where + Self: 'a; + + fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> Self::ReadFuture<'a> { + Pipe::read(self, buf).map(Ok) + } + } + + impl<M: RawMutex, const N: usize> embedded_io::asynch::Write for Pipe<M, N> { + type WriteFuture<'a> = impl Future<Output = Result<usize, Self::Error>> + where + Self: 'a; + + fn write<'a>(&'a mut self, buf: &'a [u8]) -> Self::WriteFuture<'a> { + Pipe::write(self, buf).map(Ok) + } + + type FlushFuture<'a> = impl Future<Output = Result<(), Self::Error>> + where + Self: 'a; + + fn flush<'a>(&'a mut self) -> Self::FlushFuture<'a> { + futures_util::future::ready(Ok(())) + } + } + + impl<M: RawMutex, const N: usize> embedded_io::Io for &Pipe<M, N> { + type Error = Infallible; + } + + impl<M: RawMutex, const N: usize> embedded_io::asynch::Read for &Pipe<M, N> { + type ReadFuture<'a> = impl Future<Output = Result<usize, Self::Error>> + where + Self: 'a; + + fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> Self::ReadFuture<'a> { + Pipe::read(self, buf).map(Ok) + } + } + + impl<M: RawMutex, const N: usize> embedded_io::asynch::Write for &Pipe<M, N> { + type WriteFuture<'a> = impl Future<Output = Result<usize, Self::Error>> + where + Self: 'a; + + fn write<'a>(&'a mut self, buf: &'a [u8]) -> Self::WriteFuture<'a> { + Pipe::write(self, buf).map(Ok) + } + + type FlushFuture<'a> = impl Future<Output = Result<(), Self::Error>> + where + Self: 'a; + + fn flush<'a>(&'a mut self) -> Self::FlushFuture<'a> { + futures_util::future::ready(Ok(())) + } + } + + impl<M: RawMutex, const N: usize> embedded_io::Io for Reader<'_, M, N> { + type Error = Infallible; + } + + impl<M: RawMutex, const N: usize> embedded_io::asynch::Read for Reader<'_, M, N> { + type ReadFuture<'a> = impl Future<Output = Result<usize, Self::Error>> + where + Self: 'a; + + fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> Self::ReadFuture<'a> { + Reader::read(self, buf).map(Ok) + } + } + + impl<M: RawMutex, const N: usize> embedded_io::Io for Writer<'_, M, N> { + type Error = Infallible; + } + + impl<M: RawMutex, const N: usize> embedded_io::asynch::Write for Writer<'_, M, N> { + type WriteFuture<'a> = impl Future<Output = Result<usize, Self::Error>> + where + Self: 'a; + + fn write<'a>(&'a mut self, buf: &'a [u8]) -> Self::WriteFuture<'a> { + Writer::write(self, buf).map(Ok) + } + + type FlushFuture<'a> = impl Future<Output = Result<(), Self::Error>> + where + Self: 'a; + + fn flush<'a>(&'a mut self) -> Self::FlushFuture<'a> { + futures_util::future::ready(Ok(())) + } + } +} + +#[cfg(test)] +mod tests { + use futures_executor::ThreadPool; + use futures_util::task::SpawnExt; + use static_cell::StaticCell; + + use super::*; + use crate::blocking_mutex::raw::{CriticalSectionRawMutex, NoopRawMutex}; + + fn capacity<const N: usize>(c: &PipeState<N>) -> usize { + N - c.buffer.len() + } + + #[test] + fn writing_once() { + let mut c = PipeState::<3>::new(); + assert!(c.try_write(&[1]).is_ok()); + assert_eq!(capacity(&c), 2); + } + + #[test] + fn writing_when_full() { + let mut c = PipeState::<3>::new(); + assert_eq!(c.try_write(&[42]), Ok(1)); + assert_eq!(c.try_write(&[43]), Ok(1)); + assert_eq!(c.try_write(&[44]), Ok(1)); + assert_eq!(c.try_write(&[45]), Err(TryWriteError::Full)); + assert_eq!(capacity(&c), 0); + } + + #[test] + fn receiving_once_with_one_send() { + let mut c = PipeState::<3>::new(); + assert!(c.try_write(&[42]).is_ok()); + let mut buf = [0; 16]; + assert_eq!(c.try_read(&mut buf), Ok(1)); + assert_eq!(buf[0], 42); + assert_eq!(capacity(&c), 3); + } + + #[test] + fn receiving_when_empty() { + let mut c = PipeState::<3>::new(); + let mut buf = [0; 16]; + assert_eq!(c.try_read(&mut buf), Err(TryReadError::Empty)); + assert_eq!(capacity(&c), 3); + } + + #[test] + fn simple_send_and_receive() { + let c = Pipe::<NoopRawMutex, 3>::new(); + assert!(c.try_write(&[42]).is_ok()); + let mut buf = [0; 16]; + assert_eq!(c.try_read(&mut buf), Ok(1)); + assert_eq!(buf[0], 42); + } + + #[test] + fn cloning() { + let c = Pipe::<NoopRawMutex, 3>::new(); + let r1 = c.reader(); + let w1 = c.writer(); + + let _ = r1.clone(); + let _ = w1.clone(); + } + + #[futures_test::test] + async fn receiver_receives_given_try_write_async() { + let executor = ThreadPool::new().unwrap(); + + static CHANNEL: StaticCell<Pipe<CriticalSectionRawMutex, 3>> = StaticCell::new(); + let c = &*CHANNEL.init(Pipe::new()); + let c2 = c; + let f = async move { + assert_eq!(c2.try_write(&[42]), Ok(1)); + }; + executor.spawn(f).unwrap(); + let mut buf = [0; 16]; + assert_eq!(c.read(&mut buf).await, 1); + assert_eq!(buf[0], 42); + } + + #[futures_test::test] + async fn sender_send_completes_if_capacity() { + let c = Pipe::<CriticalSectionRawMutex, 1>::new(); + c.write(&[42]).await; + let mut buf = [0; 16]; + assert_eq!(c.read(&mut buf).await, 1); + assert_eq!(buf[0], 42); + } +} |