Merge #172

172: defmt impl for Vec r=korken89 a=theunkn0wn1

This PR adds support for encoding `heapless::Vec` for usage with `defmt`.
`defmt` can already handle slices, so this impl simply invokes that encoder method.

I chose to use the slice implementation is I did not perceive the difference between a Vec and a Slice to be of specific importance in a log file, but rather the contents of the vec / slice to be of interest. It also appeared to me as the path of least resistance.

I am marking this as a draft as I have yet to be able to validate this against my local hardware, `probe-run` is giving me some grief that I am reasonably sure is unrelated to this change set. 

Relates to #171 

Co-authored-by: joshua salzedo <thHunkn0WNd@gmail.com>
Co-authored-by: Joshua Salzedo <joshuasalzedo@gmail.com>

Cargo.toml

@@ -27,6 +27,7 @@ ufmt-impl = ["ufmt-write"]
 x86-sync-pool = []
 # only for tests
 __trybuild = []
+defmt-impl = ["defmt"]
 
 [target.x86_64-unknown-linux-gnu.dev-dependencies]
 scoped_threadpool = "0.1.8"
@@ -51,3 +52,8 @@ optional = true
 
 [dev-dependencies.ufmt]
 version = "0.1"
+
+[dependencies.defmt]
+git = "https://github.com/knurling-rs/defmt"
+branch = "main"
+optional = true

src/defmt.rs

@@ -0,0 +1,86 @@
+//! Defmt implementations for heapless types
+//!
+
+use crate::ArrayLength;
+use crate::Vec;
+use defmt::Formatter;
+
+impl<T, N> defmt::Format for Vec<T, N>
+where
+    N: ArrayLength<T>,
+    T: defmt::Format,
+{
+    fn format(&self, fmt: &mut Formatter) {
+        fmt.fmt_slice(self)
+    }
+}
+
+impl<N> defmt::Format for crate::String<N>
+where
+    N: ArrayLength<u8>,
+    u8: defmt::Format,
+{
+    fn format(&self, fmt: &mut Formatter) {
+        fmt.str(self.as_str());
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::convert::TryInto;
+
+    use crate::{consts::*, Vec};
+
+    #[test]
+    /// Tests encoding Vec with defmt,
+    /// based loosely on https://github.com/knurling-rs/defmt/blob/main/tests/encode.rs#L483
+    fn test_defmt_format_vec() {
+        let v: Vec<_, U8> = Vec::from_slice(b"abc").unwrap();
+        let index = defmt::export::fetch_string_index();
+
+        // borrowed from https://github.com/knurling-rs/defmt/blob/main/tests/encode.rs#L49
+        let fake_interned = index.wrapping_add(1) & 0x7F;
+
+        let timestamp = defmt::export::fetch_timestamp();
+        let mut formatter = defmt::Formatter::new();
+        defmt::winfo!(formatter, "{:?}", v);
+        assert_eq!(
+            formatter.bytes(),
+            &[
+                index,
+                timestamp,
+                v.len().try_into().unwrap(),
+                fake_interned, // Faked
+                // Data bytes.
+                97u8,
+                98u8,
+                99u8,
+            ]
+        );
+    }
+
+    /// Tests encoding String with defmt,
+    /// based loosely on https://github.com/knurling-rs/defmt/blob/main/tests/encode.rs#L483
+    #[test]
+    fn test_defmt_format_str() {
+        let mut v: crate::String<crate::consts::U32> = crate::String::new();
+        v.push_str("foo").unwrap();
+        let index = defmt::export::fetch_string_index();
+
+        let timestamp = defmt::export::fetch_timestamp();
+        let mut formatter = defmt::Formatter::new();
+        defmt::winfo!(formatter, "{:?}", v);
+        assert_eq!(
+            formatter.bytes(),
+            &[
+                index,
+                timestamp,
+                v.len().try_into().unwrap(),
+                // Data bytes.
+                102u8,
+                111u8,
+                111u8,
+            ]
+        );
+    }
+}

src/lib.rs

@@ -106,6 +106,8 @@ pub mod mpmc;
 pub mod pool;
 #[cfg(has_atomics)]
 pub mod spsc;
+#[cfg(feature = "defmt-impl")]
+mod defmt;
 
 #[cfg(feature = "ufmt-impl")]
 mod ufmt;