Add conversion functions on SysExMessage trait

src/midi/sysex.rs

@@ -7,10 +7,29 @@ pub trait SysExMessage: Debug + Clone + PartialEq + Send + Sync {
     /// The maximum SysEx message size, in bytes.
     const MAX_BUFFER_SIZE: usize;
 
-    // TODO: Conversion functions
+    /// Read a SysEx message from `buffer` and convert it to this message type if supported.
+    /// `buffer`'s length matches the received message. It is not padded to `MAX_BUFFER_SIZE` bytes.
+    fn from_buffer(buffer: &[u8]) -> Option<Self>;
+
+    /// Serialize this message object as a SysEx message in `buffer`, returning the message's length
+    /// in bytes.
+    ///
+    /// `buffer` is a `[u8; Self::MAX_BUFFER_SIZE]`, but Rust currently doesn't allow using
+    /// associated constants in method types:
+    ///
+    /// <https://github.com/rust-lang/rust/issues/60551>
+    fn to_buffer(self, buffer: &mut [u8]) -> usize;
 }
 
 /// A default implementation plugins that don't need SysEx support can use.
 impl SysExMessage for () {
     const MAX_BUFFER_SIZE: usize = 0;
+
+    fn from_buffer(_buffer: &[u8]) -> Option<Self> {
+        None
+    }
+
+    fn to_buffer(self, _buffer: &mut [u8]) -> usize {
+        0
+    }
 }