lnwire: refactor Encode to use specific writers - III

This commit refactors the remaining usage of WriteElements. By
replacing the interface types with concrete types for the params used in
the methods, most of the encoding of the messages now takes zero heap
allocations.

lnwire/channel_reestablish.go

@@ -77,12 +77,15 @@ var _ Message = (*ChannelReestablish)(nil)
 //
 // This is part of the lnwire.Message interface.
 func (a *ChannelReestablish) Encode(w *bytes.Buffer, pver uint32) error {
-	err := WriteElements(w,
-		a.ChanID,
-		a.NextLocalCommitHeight,
-		a.RemoteCommitTailHeight,
-	)
-	if err != nil {
+	if err := WriteChannelID(w, a.ChanID); err != nil {
+		return err
+	}
+
+	if err := WriteUint64(w, a.NextLocalCommitHeight); err != nil {
+		return err
+	}
+
+	if err := WriteUint64(w, a.RemoteCommitTailHeight); err != nil {
 		return err
 	}
 
@@ -94,15 +97,18 @@ func (a *ChannelReestablish) Encode(w *bytes.Buffer, pver uint32) error {
 		//
 		// NOTE: This is here primarily for the quickcheck tests, in
 		// practice, we'll always populate this field.
-		return WriteElements(w, a.ExtraData)
+		return WriteBytes(w, a.ExtraData)
 	}
 
 	// Otherwise, we'll write out the remaining elements.
-	return WriteElements(w,
-		a.LastRemoteCommitSecret[:],
-		a.LocalUnrevokedCommitPoint,
-		a.ExtraData,
-	)
+	if err := WriteBytes(w, a.LastRemoteCommitSecret[:]); err != nil {
+		return err
+	}
+
+	if err := WritePublicKey(w, a.LocalUnrevokedCommitPoint); err != nil {
+		return err
+	}
+	return WriteBytes(w, a.ExtraData)
 }
 
 // Decode deserializes a serialized ChannelReestablish stored in the passed