Add enums describing message metadata

src/io/mod.rs

@@ -116,6 +116,24 @@ pub enum KeyboardKeyEvent {
     Released(KeyboardKey),
 }
 
+/// Describes a message sent using SendMessage
+#[derive(Clone, Debug)]
+pub enum SentMessage<'m> {
+    /// A file is sent
+    File(RawFd),
+    /// Binary data is sent
+    Data(&'m [u8]),
+}
+
+/// Describes a message received using ReceiveMessage
+#[derive(Debug)]
+pub enum ReceivedMessageMetadata {
+    /// A file was received
+    File(RawFd),
+    /// Binary data was received (contains data length)
+    Data(usize),
+}
+
 /// Specifies where a message should be delivered on a channel
 #[derive(Clone, Copy, Debug)]
 pub enum MessageDestination {