Added message header accessors.

Fortune for rsh's current commit: Future small blessing − 末小吉

src/message.rs

@@ -37,6 +37,7 @@ pub trait MessageValue: Serialize + for<'de> Deserialize<'de>{}
 impl<T: ?Sized> MessageValue for T
 where T: Serialize + for<'de> Deserialize<'de>{}
 
+/// A message that can send a value into bytes.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Message<V: ?Sized + MessageValue>
 {
@@ -50,6 +51,34 @@ pub struct Message<V: ?Sized + MessageValue>
     value: V,
 }
 
+// Accessors
+impl<V: ?Sized + MessageValue> Message<V>
+{
+    /// Get a reference to this message's header
+    #[inline(always)] pub fn header(&self) -> MessageHeader<'_, V>
+    {
+	MessageHeader(&self.header, PhantomData)
+    }
+}
+macro_rules! accessor {
+    ($name:ident, $fn_name:ident, $type:ty $(; $comment:literal)?) => {
+	$(#[doc = $comment])?
+	#[inline] pub fn $fn_name(&self) -> &$type
+	{
+	    &self.0.$name
+	}
+    };
+    ($name:ident, $type:ty $(; $comment:literal)?) => (accessor!($name, $name, $type $(; $comment)?););
+
+}
+impl<'a, V: ?Sized> MessageHeader<'a, V>
+{    
+    accessor!(id, Uuid; "This message's randomly generated ID");
+    accessor!(idemp, idempotence, Uuid; "This message's idempotence key");
+    accessor!(timestamp, unix_timestamp_utc, u64; "This message's UTX unix timestamp");
+    accessor!(responds_to, Option<Uuid>; "The ID this message is responding to (if any)");
+}
+
 /// `SerializedMessage` header.
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
 struct SerHeader
@@ -64,6 +93,10 @@ struct SerHeader
     responds_to: Option<Uuid>,
 }
 
+/// A reference to a message's header.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct MessageHeader<'a, V:?Sized>(&'a SerHeader, PhantomData<&'a V>);
+
 impl<V: ?Sized + MessageValue> AsRef<V> for Message<V>
 {
     #[inline(always)] fn as_ref(&self) -> &V