embedded_io_adapters::unblock::Unblock: adapter from embedded_io::{Read, Write} to embedded_io_async::{Read, Write}

embedded-io-adapters/Cargo.toml

@@ -16,14 +16,16 @@ categories = [
 std = ["embedded-io/std"]
 tokio-1 = ["std", "dep:tokio", "dep:embedded-io-async", "embedded-io-async?/std"]
 futures-03 = ["std", "dep:futures", "dep:embedded-io-async", "embedded-io-async?/std"]
+unblock = ["std", "dep:embedded-io-async", "dep:blocking"]
 
 [dependencies]
+blocking = { version = "1.6.0", optional = true }
 embedded-io = { version = "0.6", path = "../embedded-io" }
 embedded-io-async = { version = "0.6.1", path = "../embedded-io-async", optional = true }
 
 futures = { version = "0.3.21", features = ["std"], default-features = false, optional = true }
 tokio = { version = "1", features = ["io-util"], default-features = false, optional = true }
 
 [package.metadata.docs.rs]
-features = ["std", "tokio-1", "futures-03"]
+features = ["std", "tokio-1", "futures-03", "unblock"]
 rustdoc-args = ["--cfg", "docsrs"]

embedded-io-adapters/src/lib.rs

@@ -16,3 +16,7 @@ pub mod futures_03;
 #[cfg(feature = "tokio-1")]
 #[cfg_attr(docsrs, doc(cfg(feature = "tokio-1")))]
 pub mod tokio_1;
+
+#[cfg(feature = "unblock")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
+pub mod unblock;

embedded-io-adapters/src/unblock.rs

@@ -0,0 +1,168 @@
+//! Adapters to/from `futures::io` traits.
+
+// MSRV is 1.60 if you don't enable async, 1.80 if you do.
+// Cargo.toml has 1.60, which makes Clippy complain that `poll_fn` was introduced
+// in 1.64. So, just silence it for this file.
+#![allow(clippy::incompatible_msrv)]
+
+use std::sync::{Arc, Mutex};
+
+use blocking::unblock;
+
+/// Adapter from `embedded_io` traits to `embedded_io_async` traits.
+///
+/// This is not suitable for use in embedded environments, but it can be useful for quickly
+/// iterating on driver code from your desktop without constantly re-flashing development boards.
+///
+/// This is quite inefficient, because it does IO operations on a threadpool, and does
+/// an awful lot of copying. No attempt has been made to optimize this.
+///
+/// If you have access to a port implementing std::io::Read + std::io::Write and either
+/// std::os::unix::io::AsRawFd or std::os::windows::io::AsRawSocket, you should attempt to use
+/// `async_io::Async` followed by `embedded_io_adapters::futures_03::FromFutures` instead.
+///
+/// If you only need `embedded_io_async::Read` or `embedded_io_async::Write`, you can use
+/// `UnblockRead` or `UnblockWrite`. In practice, most of the time you should just use this adapter.
+///
+/// The ergonomics of this are a bit worse than the other adapters because we need to avoid
+/// overlapping impls of embedded_io::ErrorType.
+pub struct Unblock<T: Send + Sync> {
+    read: UnblockRead<T>,
+    write: UnblockWrite<T>,
+}
+
+impl<T: Send + Sync + 'static> Unblock<T> {
+    /// Create a new adapter.
+    pub fn new(port: T) -> Self {
+        let inner = Arc::new(Mutex::new(port));
+        Self {
+            read: UnblockRead {
+                inner: inner.clone(),
+            },
+            write: UnblockWrite { inner },
+        }
+    }
+}
+
+impl<T: embedded_io::Read + embedded_io::Write + Send + Sync> embedded_io::ErrorType
+    for Unblock<T>
+{
+    type Error = T::Error;
+}
+
+impl<T: embedded_io::Read + embedded_io::Write + Send + Sync + 'static> embedded_io_async::Read
+    for Unblock<T>
+where
+    T::Error: Send + 'static,
+{
+    async fn read(&mut self, buf: &mut [u8]) -> Result<usize, T::Error> {
+        self.read.read(buf).await
+    }
+}
+
+impl<T: embedded_io::Read + embedded_io::Write + Send + Sync + 'static> embedded_io_async::Write
+    for Unblock<T>
+where
+    T::Error: Send + 'static,
+{
+    async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
+        self.write.write(buf).await
+    }
+
+    async fn flush(&mut self) -> Result<(), Self::Error> {
+        self.write.flush().await
+    }
+}
+
+/// Use this if you have a port that only implements `embedded_io::Read`. Otherwise, use `Unblock`.
+///
+/// The ergonomics of this are a bit worse than the other adapters because we need to avoid
+/// overlapping impls of embedded_io::ErrorType.
+pub struct UnblockRead<T: Send + Sync> {
+    inner: Arc<Mutex<T>>,
+}
+
+impl<T: Send + Sync + 'static> UnblockRead<T> {
+    /// Create a new adapter.
+    pub fn new(port: T) -> Self {
+        Self {
+            inner: Arc::new(Mutex::new(port)),
+        }
+    }
+}
+
+impl<T: embedded_io::Read + Send + Sync + 'static> embedded_io_async::Read for UnblockRead<T>
+where
+    T::Error: Send + 'static,
+{
+    async fn read(&mut self, buf: &mut [u8]) -> Result<usize, T::Error> {
+        let max_len = buf.len();
+        let inner = self.inner.clone();
+
+        let result = unblock(move || {
+            let mut inner_buf: Vec<_> = std::iter::repeat(0u8).take(max_len).collect();
+            match inner.lock().unwrap().read(&mut inner_buf) {
+                Ok(count) => {
+                    inner_buf.resize(count, 0);
+                    Ok(inner_buf)
+                }
+                Err(e) => Err(e),
+            }
+        })
+        .await;
+
+        match result {
+            Ok(inner_buf) => {
+                buf[..inner_buf.len()].copy_from_slice(&inner_buf);
+                Ok(inner_buf.len())
+            }
+            Err(e) => Err(e),
+        }
+    }
+}
+
+impl<T: embedded_io::Read + Send + Sync> embedded_io::ErrorType for UnblockRead<T> {
+    type Error = T::Error;
+}
+
+/// Use this if you have a port that only implements `embedded_io::Write`. Otherwise, use `Unblock`.
+///
+/// The ergonomics of this are a bit worse than the other adapters because we need to avoid
+/// overlapping impls of embedded_io::ErrorType.
+pub struct UnblockWrite<T: Send + Sync> {
+    inner: Arc<Mutex<T>>,
+}
+
+impl<T: Send + Sync + 'static> UnblockWrite<T> {
+    /// Create a new adapter.
+    pub fn new(port: T) -> Self {
+        Self {
+            inner: Arc::new(Mutex::new(port)),
+        }
+    }
+}
+
+impl<T: embedded_io::Write + Send + Sync> embedded_io::ErrorType for UnblockWrite<T> {
+    type Error = T::Error;
+}
+
+impl<T: embedded_io::Write + Send + Sync + 'static> embedded_io_async::Write for UnblockWrite<T>
+where
+    T::Error: Send + 'static,
+{
+    async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
+        let inner = self.inner.clone();
+        let inner_buf = Vec::from(buf);
+
+        unblock(move || {
+            let inner_buf = inner_buf;
+            inner.lock().unwrap().write(&inner_buf)
+        })
+        .await
+    }
+
+    async fn flush(&mut self) -> Result<(), Self::Error> {
+        let inner = self.inner.clone();
+        unblock(move || inner.lock().unwrap().flush()).await
+    }
+}