652 lines
20 KiB
Rust
652 lines
20 KiB
Rust
//! Async byte stream pipe.
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use core::cell::{RefCell, UnsafeCell};
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use core::future::Future;
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use core::ops::Range;
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use core::pin::Pin;
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use core::task::{Context, Poll};
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use crate::blocking_mutex::raw::RawMutex;
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use crate::blocking_mutex::Mutex;
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use crate::ring_buffer::RingBuffer;
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use crate::waitqueue::WakerRegistration;
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/// Write-only access to a [`Pipe`].
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pub struct Writer<'p, M, const N: usize>
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where
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M: RawMutex,
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{
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pipe: &'p Pipe<M, N>,
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}
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impl<'p, M, const N: usize> Clone for Writer<'p, M, N>
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where
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M: RawMutex,
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{
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fn clone(&self) -> Self {
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Writer { pipe: self.pipe }
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}
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}
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impl<'p, M, const N: usize> Copy for Writer<'p, M, N> where M: RawMutex {}
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impl<'p, M, const N: usize> Writer<'p, M, N>
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where
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M: RawMutex,
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{
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/// Write some bytes to the pipe.
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///
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/// See [`Pipe::write()`]
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pub fn write<'a>(&'a self, buf: &'a [u8]) -> WriteFuture<'a, M, N> {
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self.pipe.write(buf)
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}
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/// Attempt to immediately write some bytes to the pipe.
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///
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/// See [`Pipe::try_write()`]
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pub fn try_write(&self, buf: &[u8]) -> Result<usize, TryWriteError> {
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self.pipe.try_write(buf)
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}
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}
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/// Future returned by [`Pipe::write`] and [`Writer::write`].
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#[must_use = "futures do nothing unless you `.await` or poll them"]
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pub struct WriteFuture<'p, M, const N: usize>
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where
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M: RawMutex,
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{
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pipe: &'p Pipe<M, N>,
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buf: &'p [u8],
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}
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impl<'p, M, const N: usize> Future for WriteFuture<'p, M, N>
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where
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M: RawMutex,
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{
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type Output = usize;
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fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
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match self.pipe.try_write_with_context(Some(cx), self.buf) {
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Ok(n) => Poll::Ready(n),
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Err(TryWriteError::Full) => Poll::Pending,
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}
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}
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}
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impl<'p, M, const N: usize> Unpin for WriteFuture<'p, M, N> where M: RawMutex {}
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/// Read-only access to a [`Pipe`].
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pub struct Reader<'p, M, const N: usize>
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where
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M: RawMutex,
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{
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pipe: &'p Pipe<M, N>,
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}
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impl<'p, M, const N: usize> Reader<'p, M, N>
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where
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M: RawMutex,
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{
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/// Read some bytes from the pipe.
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///
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/// See [`Pipe::read()`]
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pub fn read<'a>(&'a self, buf: &'a mut [u8]) -> ReadFuture<'a, M, N> {
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self.pipe.read(buf)
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}
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/// Attempt to immediately read some bytes from the pipe.
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///
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/// See [`Pipe::try_read()`]
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pub fn try_read(&self, buf: &mut [u8]) -> Result<usize, TryReadError> {
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self.pipe.try_read(buf)
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}
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/// Return the contents of the internal buffer, filling it with more data from the inner reader if it is empty.
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///
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/// If no bytes are currently available to read, this function waits until at least one byte is available.
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///
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/// If the reader is at end-of-file (EOF), an empty slice is returned.
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pub fn fill_buf(&mut self) -> FillBufFuture<'_, M, N> {
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FillBufFuture { pipe: Some(self.pipe) }
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}
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/// Try returning contents of the internal buffer.
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///
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/// If no bytes are currently available to read, this function returns `Err(TryReadError::Empty)`.
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///
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/// If the reader is at end-of-file (EOF), an empty slice is returned.
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pub fn try_fill_buf(&mut self) -> Result<&[u8], TryReadError> {
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unsafe { self.pipe.try_fill_buf_with_context(None) }
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}
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/// Tell this buffer that `amt` bytes have been consumed from the buffer, so they should no longer be returned in calls to `fill_buf`.
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pub fn consume(&mut self, amt: usize) {
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self.pipe.consume(amt)
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}
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}
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/// Future returned by [`Pipe::read`] and [`Reader::read`].
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#[must_use = "futures do nothing unless you `.await` or poll them"]
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pub struct ReadFuture<'p, M, const N: usize>
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where
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M: RawMutex,
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{
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pipe: &'p Pipe<M, N>,
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buf: &'p mut [u8],
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}
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impl<'p, M, const N: usize> Future for ReadFuture<'p, M, N>
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where
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M: RawMutex,
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{
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type Output = usize;
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fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
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match self.pipe.try_read_with_context(Some(cx), self.buf) {
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Ok(n) => Poll::Ready(n),
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Err(TryReadError::Empty) => Poll::Pending,
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}
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}
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}
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impl<'p, M, const N: usize> Unpin for ReadFuture<'p, M, N> where M: RawMutex {}
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/// Future returned by [`Pipe::fill_buf`] and [`Reader::fill_buf`].
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#[must_use = "futures do nothing unless you `.await` or poll them"]
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pub struct FillBufFuture<'p, M, const N: usize>
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where
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M: RawMutex,
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{
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pipe: Option<&'p Pipe<M, N>>,
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}
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impl<'p, M, const N: usize> Future for FillBufFuture<'p, M, N>
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where
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M: RawMutex,
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{
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type Output = &'p [u8];
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fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
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let pipe = self.pipe.take().unwrap();
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match unsafe { pipe.try_fill_buf_with_context(Some(cx)) } {
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Ok(buf) => Poll::Ready(buf),
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Err(TryReadError::Empty) => {
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self.pipe = Some(pipe);
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Poll::Pending
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}
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}
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}
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}
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impl<'p, M, const N: usize> Unpin for FillBufFuture<'p, M, N> where M: RawMutex {}
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/// Error returned by [`try_read`](Pipe::try_read).
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#[derive(PartialEq, Eq, Clone, Copy, Debug)]
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#[cfg_attr(feature = "defmt", derive(defmt::Format))]
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pub enum TryReadError {
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/// No data could be read from the pipe because it is currently
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/// empty, and reading would require blocking.
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Empty,
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}
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/// Error returned by [`try_write`](Pipe::try_write).
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#[derive(PartialEq, Eq, Clone, Copy, Debug)]
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#[cfg_attr(feature = "defmt", derive(defmt::Format))]
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pub enum TryWriteError {
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/// No data could be written to the pipe because it is
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/// currently full, and writing would require blocking.
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Full,
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}
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struct PipeState<const N: usize> {
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buffer: RingBuffer<N>,
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read_waker: WakerRegistration,
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write_waker: WakerRegistration,
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}
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#[repr(transparent)]
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struct Buffer<const N: usize>(UnsafeCell<[u8; N]>);
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impl<const N: usize> Buffer<N> {
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unsafe fn get<'a>(&self, r: Range<usize>) -> &'a [u8] {
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let p = self.0.get() as *const u8;
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core::slice::from_raw_parts(p.add(r.start), r.end - r.start)
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}
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unsafe fn get_mut<'a>(&self, r: Range<usize>) -> &'a mut [u8] {
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let p = self.0.get() as *mut u8;
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core::slice::from_raw_parts_mut(p.add(r.start), r.end - r.start)
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}
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}
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unsafe impl<const N: usize> Send for Buffer<N> {}
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unsafe impl<const N: usize> Sync for Buffer<N> {}
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/// A bounded byte-oriented pipe for communicating between asynchronous tasks
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/// with backpressure.
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///
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/// The pipe will buffer up to the provided number of bytes. Once the
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/// buffer is full, attempts to `write` new bytes will wait until buffer space is freed up.
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///
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/// All data written will become available in the same order as it was written.
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pub struct Pipe<M, const N: usize>
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where
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M: RawMutex,
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{
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buf: Buffer<N>,
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inner: Mutex<M, RefCell<PipeState<N>>>,
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}
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impl<M, const N: usize> Pipe<M, N>
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where
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M: RawMutex,
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{
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/// Establish a new bounded pipe. For example, to create one with a NoopMutex:
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///
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/// ```
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/// use embassy_sync::pipe::Pipe;
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/// use embassy_sync::blocking_mutex::raw::NoopRawMutex;
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///
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/// // Declare a bounded pipe, with a buffer of 256 bytes.
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/// let mut pipe = Pipe::<NoopRawMutex, 256>::new();
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/// ```
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pub const fn new() -> Self {
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Self {
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buf: Buffer(UnsafeCell::new([0; N])),
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inner: Mutex::new(RefCell::new(PipeState {
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buffer: RingBuffer::new(),
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read_waker: WakerRegistration::new(),
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write_waker: WakerRegistration::new(),
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})),
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}
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}
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fn lock<R>(&self, f: impl FnOnce(&mut PipeState<N>) -> R) -> R {
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self.inner.lock(|rc| f(&mut *rc.borrow_mut()))
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}
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fn try_read_with_context(&self, cx: Option<&mut Context<'_>>, buf: &mut [u8]) -> Result<usize, TryReadError> {
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self.inner.lock(|rc: &RefCell<PipeState<N>>| {
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let s = &mut *rc.borrow_mut();
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if s.buffer.is_full() {
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s.write_waker.wake();
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}
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let available = unsafe { self.buf.get(s.buffer.pop_buf()) };
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if available.is_empty() {
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if let Some(cx) = cx {
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s.read_waker.register(cx.waker());
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}
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return Err(TryReadError::Empty);
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}
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let n = available.len().min(buf.len());
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buf[..n].copy_from_slice(&available[..n]);
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s.buffer.pop(n);
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Ok(n)
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})
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}
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// safety: While the returned slice is alive,
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// no `read` or `consume` methods in the pipe must be called.
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unsafe fn try_fill_buf_with_context(&self, cx: Option<&mut Context<'_>>) -> Result<&[u8], TryReadError> {
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self.inner.lock(|rc: &RefCell<PipeState<N>>| {
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let s = &mut *rc.borrow_mut();
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if s.buffer.is_full() {
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s.write_waker.wake();
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}
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let available = unsafe { self.buf.get(s.buffer.pop_buf()) };
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if available.is_empty() {
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if let Some(cx) = cx {
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s.read_waker.register(cx.waker());
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}
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return Err(TryReadError::Empty);
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}
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Ok(available)
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})
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}
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fn consume(&self, amt: usize) {
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self.inner.lock(|rc: &RefCell<PipeState<N>>| {
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let s = &mut *rc.borrow_mut();
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let available = s.buffer.pop_buf();
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assert!(amt <= available.len());
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s.buffer.pop(amt);
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})
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}
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fn try_write_with_context(&self, cx: Option<&mut Context<'_>>, buf: &[u8]) -> Result<usize, TryWriteError> {
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self.inner.lock(|rc: &RefCell<PipeState<N>>| {
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let s = &mut *rc.borrow_mut();
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if s.buffer.is_empty() {
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s.read_waker.wake();
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}
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let available = unsafe { self.buf.get_mut(s.buffer.push_buf()) };
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if available.is_empty() {
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if let Some(cx) = cx {
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s.write_waker.register(cx.waker());
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}
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return Err(TryWriteError::Full);
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}
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let n = available.len().min(buf.len());
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available[..n].copy_from_slice(&buf[..n]);
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s.buffer.push(n);
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Ok(n)
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})
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}
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/// Split this pipe into a BufRead-capable reader and a writer.
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///
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/// The reader and writer borrow the current pipe mutably, so it is not
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/// possible to use it directly while they exist. This is needed because
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/// implementing `BufRead` requires there is a single reader.
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///
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/// The writer is cloneable, the reader is not.
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pub fn split(&mut self) -> (Reader<'_, M, N>, Writer<'_, M, N>) {
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(Reader { pipe: self }, Writer { pipe: self })
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}
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/// Write some bytes to the pipe.
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///
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/// This method writes a nonzero amount of bytes from `buf` into the pipe, and
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/// returns the amount of bytes written.
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///
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/// If it is not possible to write a nonzero amount of bytes because the pipe's buffer is full,
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/// this method will wait until it isn't. See [`try_write`](Self::try_write) for a variant that
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/// returns an error instead of waiting.
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///
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/// It is not guaranteed that all bytes in the buffer are written, even if there's enough
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/// free space in the pipe buffer for all. In other words, it is possible for `write` to return
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/// without writing all of `buf` (returning a number less than `buf.len()`) and still leave
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/// free space in the pipe buffer. You should always `write` in a loop, or use helpers like
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/// `write_all` from the `embedded-io` crate.
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pub fn write<'a>(&'a self, buf: &'a [u8]) -> WriteFuture<'a, M, N> {
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WriteFuture { pipe: self, buf }
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}
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/// Write all bytes to the pipe.
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///
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/// This method writes all bytes from `buf` into the pipe
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pub async fn write_all(&self, mut buf: &[u8]) {
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while !buf.is_empty() {
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let n = self.write(buf).await;
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buf = &buf[n..];
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}
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}
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/// Attempt to immediately write some bytes to the pipe.
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///
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/// This method will either write a nonzero amount of bytes to the pipe immediately,
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/// or return an error if the pipe is empty. See [`write`](Self::write) for a variant
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/// that waits instead of returning an error.
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pub fn try_write(&self, buf: &[u8]) -> Result<usize, TryWriteError> {
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self.try_write_with_context(None, buf)
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}
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/// Read some bytes from the pipe.
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///
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/// This method reads a nonzero amount of bytes from the pipe into `buf` and
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/// returns the amount of bytes read.
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///
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/// If it is not possible to read a nonzero amount of bytes because the pipe's buffer is empty,
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/// this method will wait until it isn't. See [`try_read`](Self::try_read) for a variant that
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/// returns an error instead of waiting.
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///
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/// It is not guaranteed that all bytes in the buffer are read, even if there's enough
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/// space in `buf` for all. In other words, it is possible for `read` to return
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/// without filling `buf` (returning a number less than `buf.len()`) and still leave bytes
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/// in the pipe buffer. You should always `read` in a loop, or use helpers like
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/// `read_exact` from the `embedded-io` crate.
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pub fn read<'a>(&'a self, buf: &'a mut [u8]) -> ReadFuture<'a, M, N> {
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ReadFuture { pipe: self, buf }
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}
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/// Attempt to immediately read some bytes from the pipe.
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///
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/// This method will either read a nonzero amount of bytes from the pipe immediately,
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/// or return an error if the pipe is empty. See [`read`](Self::read) for a variant
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/// that waits instead of returning an error.
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pub fn try_read(&self, buf: &mut [u8]) -> Result<usize, TryReadError> {
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self.try_read_with_context(None, buf)
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}
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/// Clear the data in the pipe's buffer.
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pub fn clear(&self) {
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self.inner.lock(|rc: &RefCell<PipeState<N>>| {
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let s = &mut *rc.borrow_mut();
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s.buffer.clear();
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s.write_waker.wake();
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})
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}
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/// Return whether the pipe is full (no free space in the buffer)
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pub fn is_full(&self) -> bool {
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self.len() == N
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}
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/// Return whether the pipe is empty (no data buffered)
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pub fn is_empty(&self) -> bool {
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self.len() == 0
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}
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/// Total byte capacity.
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///
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/// This is the same as the `N` generic param.
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pub fn capacity(&self) -> usize {
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N
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}
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/// Used byte capacity.
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pub fn len(&self) -> usize {
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self.lock(|c| c.buffer.len())
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}
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/// Free byte capacity.
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///
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/// This is equivalent to `capacity() - len()`
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pub fn free_capacity(&self) -> usize {
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N - self.len()
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}
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}
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#[cfg(feature = "nightly")]
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mod io_impls {
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use core::convert::Infallible;
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use super::*;
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impl<M: RawMutex, const N: usize> embedded_io_async::ErrorType for Pipe<M, N> {
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type Error = Infallible;
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}
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impl<M: RawMutex, const N: usize> embedded_io_async::Read for Pipe<M, N> {
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async fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
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Ok(Pipe::read(self, buf).await)
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}
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}
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impl<M: RawMutex, const N: usize> embedded_io_async::Write for Pipe<M, N> {
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async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
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Ok(Pipe::write(self, buf).await)
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}
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async fn flush(&mut self) -> Result<(), Self::Error> {
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Ok(())
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}
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}
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impl<M: RawMutex, const N: usize> embedded_io_async::ErrorType for &Pipe<M, N> {
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type Error = Infallible;
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}
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impl<M: RawMutex, const N: usize> embedded_io_async::Read for &Pipe<M, N> {
|
|
async fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
|
|
Ok(Pipe::read(self, buf).await)
|
|
}
|
|
}
|
|
|
|
impl<M: RawMutex, const N: usize> embedded_io_async::Write for &Pipe<M, N> {
|
|
async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
|
|
Ok(Pipe::write(self, buf).await)
|
|
}
|
|
|
|
async fn flush(&mut self) -> Result<(), Self::Error> {
|
|
Ok(())
|
|
}
|
|
}
|
|
|
|
impl<M: RawMutex, const N: usize> embedded_io_async::ErrorType for Reader<'_, M, N> {
|
|
type Error = Infallible;
|
|
}
|
|
|
|
impl<M: RawMutex, const N: usize> embedded_io_async::Read for Reader<'_, M, N> {
|
|
async fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
|
|
Ok(Reader::read(self, buf).await)
|
|
}
|
|
}
|
|
|
|
impl<M: RawMutex, const N: usize> embedded_io_async::BufRead for Reader<'_, M, N> {
|
|
async fn fill_buf(&mut self) -> Result<&[u8], Self::Error> {
|
|
Ok(Reader::fill_buf(self).await)
|
|
}
|
|
|
|
fn consume(&mut self, amt: usize) {
|
|
Reader::consume(self, amt)
|
|
}
|
|
}
|
|
|
|
impl<M: RawMutex, const N: usize> embedded_io_async::ErrorType for Writer<'_, M, N> {
|
|
type Error = Infallible;
|
|
}
|
|
|
|
impl<M: RawMutex, const N: usize> embedded_io_async::Write for Writer<'_, M, N> {
|
|
async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
|
|
Ok(Writer::write(self, buf).await)
|
|
}
|
|
|
|
async fn flush(&mut self) -> Result<(), Self::Error> {
|
|
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};
|
|
|
|
#[test]
|
|
fn writing_once() {
|
|
let c = Pipe::<NoopRawMutex, 3>::new();
|
|
assert!(c.try_write(&[1]).is_ok());
|
|
assert_eq!(c.free_capacity(), 2);
|
|
}
|
|
|
|
#[test]
|
|
fn writing_when_full() {
|
|
let c = Pipe::<NoopRawMutex, 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!(c.free_capacity(), 0);
|
|
}
|
|
|
|
#[test]
|
|
fn receiving_once_with_one_send() {
|
|
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);
|
|
assert_eq!(c.free_capacity(), 3);
|
|
}
|
|
|
|
#[test]
|
|
fn receiving_when_empty() {
|
|
let c = Pipe::<NoopRawMutex, 3>::new();
|
|
let mut buf = [0; 16];
|
|
assert_eq!(c.try_read(&mut buf), Err(TryReadError::Empty));
|
|
assert_eq!(c.free_capacity(), 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 read_buf() {
|
|
let mut c = Pipe::<NoopRawMutex, 3>::new();
|
|
let (mut r, w) = c.split();
|
|
assert!(w.try_write(&[42, 43]).is_ok());
|
|
let buf = r.try_fill_buf().unwrap();
|
|
assert_eq!(buf, &[42, 43]);
|
|
let buf = r.try_fill_buf().unwrap();
|
|
assert_eq!(buf, &[42, 43]);
|
|
r.consume(1);
|
|
let buf = r.try_fill_buf().unwrap();
|
|
assert_eq!(buf, &[43]);
|
|
r.consume(1);
|
|
assert_eq!(r.try_fill_buf(), Err(TryReadError::Empty));
|
|
assert_eq!(w.try_write(&[44, 45, 46]), Ok(1));
|
|
assert_eq!(w.try_write(&[45, 46]), Ok(2));
|
|
let buf = r.try_fill_buf().unwrap();
|
|
assert_eq!(buf, &[44]); // only one byte due to wraparound.
|
|
r.consume(1);
|
|
let buf = r.try_fill_buf().unwrap();
|
|
assert_eq!(buf, &[45, 46]);
|
|
assert!(w.try_write(&[47]).is_ok());
|
|
let buf = r.try_fill_buf().unwrap();
|
|
assert_eq!(buf, &[45, 46, 47]);
|
|
r.consume(3);
|
|
}
|
|
|
|
#[test]
|
|
fn writer_is_cloneable() {
|
|
let mut c = Pipe::<NoopRawMutex, 3>::new();
|
|
let (_r, w) = c.split();
|
|
let _ = w.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);
|
|
}
|
|
}
|