feat: implement Read, BufRead, and Write for VecDeque<u8>

Author: mkroening

embedded-io-async/src/impls/mod.rs

@@ -5,3 +5,5 @@ mod slice_ref;
 mod boxx;
 #[cfg(feature = "alloc")]
 mod vec;
+#[cfg(feature = "alloc")]
+mod vec_deque;

embedded-io-async/src/impls/vec_deque.rs

@@ -0,0 +1,83 @@
+//! Adapted from std.
+
+use alloc::collections::vec_deque::VecDeque;
+
+use crate::{BufRead, Read, ReadExactError, Write};
+
+/// Read is implemented for `VecDeque<u8>` by consuming bytes from the front of the `VecDeque`.
+#[cfg_attr(docsrs, doc(cfg(any(feature = "std", feature = "alloc"))))]
+impl Read for VecDeque<u8> {
+    /// Fill `buf` with the contents of the "front" slice as returned by
+    /// [`as_slices`][`VecDeque::as_slices`]. If the contained byte slices of the `VecDeque` are
+    /// discontiguous, multiple calls to `read` will be needed to read the entire content.
+    #[inline]
+    async fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
+        let (ref mut front, _) = self.as_slices();
+        let n = Read::read(front, buf).await?;
+        self.drain(..n);
+        Ok(n)
+    }
+
+    #[inline]
+    async fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), ReadExactError<Self::Error>> {
+        let (front, back) = self.as_slices();
+
+        // Use only the front buffer if it is big enough to fill `buf`, else use
+        // the back buffer too.
+        match buf.split_at_mut_checked(front.len()) {
+            None => buf.copy_from_slice(&front[..buf.len()]),
+            Some((buf_front, buf_back)) => match back.split_at_checked(buf_back.len()) {
+                Some((back, _)) => {
+                    buf_front.copy_from_slice(front);
+                    buf_back.copy_from_slice(back);
+                }
+                None => {
+                    self.clear();
+                    return Err(ReadExactError::UnexpectedEof);
+                }
+            },
+        }
+
+        self.drain(..buf.len());
+        Ok(())
+    }
+}
+
+/// BufRead is implemented for `VecDeque<u8>` by reading bytes from the front of the `VecDeque`.
+#[cfg_attr(docsrs, doc(cfg(any(feature = "std", feature = "alloc"))))]
+impl BufRead for VecDeque<u8> {
+    /// Returns the contents of the "front" slice as returned by
+    /// [`as_slices`][`VecDeque::as_slices`]. If the contained byte slices of the `VecDeque` are
+    /// discontiguous, multiple calls to `fill_buf` will be needed to read the entire content.
+    #[inline]
+    async fn fill_buf(&mut self) -> Result<&[u8], Self::Error> {
+        let (front, _) = self.as_slices();
+        Ok(front)
+    }
+
+    #[inline]
+    fn consume(&mut self, amt: usize) {
+        self.drain(..amt);
+    }
+}
+
+/// Write is implemented for `VecDeque<u8>` by appending to the `VecDeque`, growing it as needed.
+#[cfg_attr(docsrs, doc(cfg(any(feature = "std", feature = "alloc"))))]
+impl Write for VecDeque<u8> {
+    #[inline]
+    async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
+        self.extend(buf);
+        Ok(buf.len())
+    }
+
+    #[inline]
+    async fn write_all(&mut self, buf: &[u8]) -> Result<(), Self::Error> {
+        self.extend(buf);
+        Ok(())
+    }
+
+    #[inline]
+    async fn flush(&mut self) -> Result<(), Self::Error> {
+        Ok(())
+    }
+}

embedded-io/src/impls/mod.rs

@@ -5,3 +5,5 @@ mod slice_ref;
 mod boxx;
 #[cfg(feature = "alloc")]
 mod vec;
+#[cfg(feature = "alloc")]
+mod vec_deque;

embedded-io/src/impls/vec_deque.rs

@@ -0,0 +1,90 @@
+//! Adapted from std.
+
+use core::convert::Infallible;
+
+use alloc::collections::vec_deque::VecDeque;
+
+use crate::{BufRead, ErrorType, Read, ReadExactError, Write};
+
+#[cfg_attr(docsrs, doc(cfg(any(feature = "std", feature = "alloc"))))]
+impl ErrorType for VecDeque<u8> {
+    type Error = Infallible;
+}
+
+/// Read is implemented for `VecDeque<u8>` by consuming bytes from the front of the `VecDeque`.
+#[cfg_attr(docsrs, doc(cfg(any(feature = "std", feature = "alloc"))))]
+impl Read for VecDeque<u8> {
+    /// Fill `buf` with the contents of the "front" slice as returned by
+    /// [`as_slices`][`VecDeque::as_slices`]. If the contained byte slices of the `VecDeque` are
+    /// discontiguous, multiple calls to `read` will be needed to read the entire content.
+    #[inline]
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize, Self::Error> {
+        let (ref mut front, _) = self.as_slices();
+        let n = Read::read(front, buf)?;
+        self.drain(..n);
+        Ok(n)
+    }
+
+    #[inline]
+    fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), ReadExactError<Self::Error>> {
+        let (front, back) = self.as_slices();
+
+        // Use only the front buffer if it is big enough to fill `buf`, else use
+        // the back buffer too.
+        match buf.split_at_mut_checked(front.len()) {
+            None => buf.copy_from_slice(&front[..buf.len()]),
+            Some((buf_front, buf_back)) => match back.split_at_checked(buf_back.len()) {
+                Some((back, _)) => {
+                    buf_front.copy_from_slice(front);
+                    buf_back.copy_from_slice(back);
+                }
+                None => {
+                    self.clear();
+                    return Err(ReadExactError::UnexpectedEof);
+                }
+            },
+        }
+
+        self.drain(..buf.len());
+        Ok(())
+    }
+}
+
+/// BufRead is implemented for `VecDeque<u8>` by reading bytes from the front of the `VecDeque`.
+#[cfg_attr(docsrs, doc(cfg(any(feature = "std", feature = "alloc"))))]
+impl BufRead for VecDeque<u8> {
+    /// Returns the contents of the "front" slice as returned by
+    /// [`as_slices`][`VecDeque::as_slices`]. If the contained byte slices of the `VecDeque` are
+    /// discontiguous, multiple calls to `fill_buf` will be needed to read the entire content.
+    #[inline]
+    fn fill_buf(&mut self) -> Result<&[u8], Self::Error> {
+        let (front, _) = self.as_slices();
+        Ok(front)
+    }
+
+    #[inline]
+    fn consume(&mut self, amt: usize) {
+        self.drain(..amt);
+    }
+}
+
+/// Write is implemented for `VecDeque<u8>` by appending to the `VecDeque`, growing it as needed.
+#[cfg_attr(docsrs, doc(cfg(any(feature = "std", feature = "alloc"))))]
+impl Write for VecDeque<u8> {
+    #[inline]
+    fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
+        self.extend(buf);
+        Ok(buf.len())
+    }
+
+    #[inline]
+    fn write_all(&mut self, buf: &[u8]) -> Result<(), Self::Error> {
+        self.extend(buf);
+        Ok(())
+    }
+
+    #[inline]
+    fn flush(&mut self) -> Result<(), Self::Error> {
+        Ok(())
+    }
+}