Merge #318

318: CAN improvements r=ryankurte a=eldruin

I added a few unit tests and then run clippy, which made me notice some small issues.
Most importantly, I changed the return type of the `Frame::new()` and `Frame::new_remote()` to be an `Option` since there is no error type defined for that.
This matches the interface of `StandardId::new()` / `ExtendedId::new()`.

`@timokroeger` do you expect any other failure reasons in these methods or is having an `Option` fine here?

Co-authored-by: Diego Barrios Romero <[email protected]>

Author: bors[bot]

src/can/id.rs

@@ -24,6 +24,9 @@ impl StandardId {
     }
 
     /// Creates a new `StandardId` without checking if it is inside the valid range.
+    ///
+    /// # Safety
+    /// Using this method can create an invalid ID and is thus marked as unsafe.
     #[inline]
     pub const unsafe fn new_unchecked(raw: u16) -> Self {
         Self(raw)
@@ -60,6 +63,9 @@ impl ExtendedId {
     }
 
     /// Creates a new `ExtendedId` without checking if it is inside the valid range.
+    ///
+    /// # Safety
+    /// Using this method can create an invalid ID and is thus marked as unsafe.
     #[inline]
     pub const unsafe fn new_unchecked(raw: u32) -> Self {
         Self(raw)
@@ -101,3 +107,54 @@ impl From<ExtendedId> for Id {
         Id::Extended(id)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn standard_id_new() {
+        assert_eq!(
+            StandardId::new(StandardId::MAX.as_raw()),
+            Some(StandardId::MAX)
+        );
+    }
+
+    #[test]
+    fn standard_id_new_out_of_range() {
+        assert_eq!(StandardId::new(StandardId::MAX.as_raw() + 1), None);
+    }
+
+    #[test]
+    fn standard_id_new_unchecked_out_of_range() {
+        let id = StandardId::MAX.as_raw() + 1;
+        assert_eq!(unsafe { StandardId::new_unchecked(id) }, StandardId(id));
+    }
+
+    #[test]
+    fn extended_id_new() {
+        assert_eq!(
+            ExtendedId::new(ExtendedId::MAX.as_raw()),
+            Some(ExtendedId::MAX)
+        );
+    }
+
+    #[test]
+    fn extended_id_new_out_of_range() {
+        assert_eq!(ExtendedId::new(ExtendedId::MAX.as_raw() + 1), None);
+    }
+
+    #[test]
+    fn extended_id_new_unchecked_out_of_range() {
+        let id = ExtendedId::MAX.as_raw() + 1;
+        assert_eq!(unsafe { ExtendedId::new_unchecked(id) }, ExtendedId(id));
+    }
+
+    #[test]
+    fn get_standard_id_from_extended_id() {
+        assert_eq!(
+            Some(ExtendedId::MAX.standard_id()),
+            StandardId::new((ExtendedId::MAX.0 >> 18) as u16)
+        );
+    }
+}

src/can/mod.rs

@@ -10,12 +10,14 @@ pub use id::*;
 /// A CAN2.0 Frame
 pub trait Frame: Sized {
     /// Creates a new frame.
-    /// Returns an error when the data slice is too long.
-    fn new(id: impl Into<Id>, data: &[u8]) -> Result<Self, ()>;
+    ///
+    /// This will return `None` if the data slice is too long.
+    fn new(id: impl Into<Id>, data: &[u8]) -> Option<Self>;
 
     /// Creates a new remote frame (RTR bit set).
-    /// Returns an error when the data length code (DLC) is not valid.
-    fn new_remote(id: impl Into<Id>, dlc: usize) -> Result<Self, ()>;
+    ///
+    /// This will return `None` if the data length code (DLC) is not valid.
+    fn new_remote(id: impl Into<Id>, dlc: usize) -> Option<Self>;
 
     /// Returns true if this frame is a extended frame.
     fn is_extended(&self) -> bool;