e-io-adapters: add ToFmt: impl fmt::Write

embedded-io-adapters/CHANGELOG.md

@@ -7,7 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
-Add unreleased changes here
+- Added `ToFmt` adapter for `core::fmt::Write`.
 
 ## 0.6.1 - 2023-11-28
 

embedded-io-adapters/src/fmt.rs

@@ -0,0 +1,42 @@
+//! Adapters to the `core::fmt::Write`.
+
+/// Adapter to the `core::fmt::Write` trait.
+#[derive(Clone, Default, PartialEq, Debug)]
+pub struct ToFmt<T: ?Sized> {
+    inner: T,
+}
+
+impl<T> ToFmt<T> {
+    /// Create a new adapter.
+    pub fn new(inner: T) -> Self {
+        Self { inner }
+    }
+
+    /// Consume the adapter, returning the inner object.
+    pub fn into_inner(self) -> T {
+        self.inner
+    }
+}
+
+impl<T: ?Sized> ToFmt<T> {
+    /// Borrow the inner object.
+    pub fn inner(&self) -> &T {
+        &self.inner
+    }
+
+    /// Mutably borrow the inner object.
+    pub fn inner_mut(&mut self) -> &mut T {
+        &mut self.inner
+    }
+}
+
+impl<T: embedded_io::Write + ?Sized> core::fmt::Write for ToFmt<T> {
+    fn write_str(&mut self, s: &str) -> core::fmt::Result {
+        self.inner.write_all(s.as_bytes()).or(Err(core::fmt::Error))
+    }
+
+    // Use fmt::Write default impls for
+    // * write_fmt(): better here than e-io::Write::write_fmt
+    //   since we don't need to bother with saving the Error
+    // * write_char(): would be the same
+}

embedded-io-adapters/src/lib.rs

@@ -15,6 +15,8 @@
     feature(async_fn_in_trait, impl_trait_projections)
 )]
 
+pub mod fmt;
+
 #[cfg(feature = "std")]
 #[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 pub mod std;