lnwire: add custom records field to type CommitSig

lnwire/commit_sig.go

@@ -45,6 +45,10 @@ type CommitSig struct {
 	// being signed for. In this case, the above Sig type MUST be blank.
 	PartialSig OptPartialSigWithNonceTLV
 
+	// CustomRecords maps TLV types to byte slices, storing arbitrary data
+	// intended for inclusion in the ExtraData field.
+	CustomRecords CustomRecords
+
 	// ExtraData is the set of data that was appended to this message to
 	// fill out the full maximum transport message size. These fields can
 	// be used to specify optional data such as custom TLV fields.
@@ -53,9 +57,7 @@ type CommitSig struct {
 
 // NewCommitSig creates a new empty CommitSig message.
 func NewCommitSig() *CommitSig {
-	return &CommitSig{
-		ExtraData: make([]byte, 0),
-	}
+	return &CommitSig{}
 }
 
 // A compile time check to ensure CommitSig implements the lnwire.Message
@@ -67,34 +69,37 @@ var _ Message = (*CommitSig)(nil)
 //
 // This is part of the lnwire.Message interface.
 func (c *CommitSig) Decode(r io.Reader, pver uint32) error {
+	// msgExtraData is a temporary variable used to read the message extra
+	// data field from the reader.
+	var msgExtraData ExtraOpaqueData
+
 	err := ReadElements(r,
 		&c.ChanID,
 		&c.CommitSig,
 		&c.HtlcSigs,
+		&msgExtraData,
 	)
 	if err != nil {
 		return err
 	}
 
-	var tlvRecords ExtraOpaqueData
-	if err := ReadElements(r, &tlvRecords); err != nil {
-		return err
-	}
-
+	// Extract TLV records from the extra data field.
 	partialSig := c.PartialSig.Zero()
-	typeMap, err := tlvRecords.ExtractRecords(&partialSig)
+
+	customRecords, parsed, extraData, err := ParseAndExtractCustomRecords(
+		msgExtraData, &partialSig,
+	)
 	if err != nil {
 		return err
 	}
 
 	// Set the corresponding TLV types if they were included in the stream.
-	if val, ok := typeMap[c.PartialSig.TlvType()]; ok && val == nil {
+	if _, ok := parsed[partialSig.TlvType()]; ok {
 		c.PartialSig = tlv.SomeRecordT(partialSig)
 	}
 
-	if len(tlvRecords) != 0 {
-		c.ExtraData = tlvRecords
-	}
+	c.CustomRecords = customRecords
+	c.ExtraData = extraData
 
 	return nil
 }
@@ -108,7 +113,10 @@ func (c *CommitSig) Encode(w *bytes.Buffer, pver uint32) error {
 	c.PartialSig.WhenSome(func(sig PartialSigWithNonceTLV) {
 		recordProducers = append(recordProducers, &sig)
 	})
-	err := EncodeMessageExtraData(&c.ExtraData, recordProducers...)
+
+	extraData, err := MergeAndEncode(
+		recordProducers, c.ExtraData, c.CustomRecords,
+	)
 	if err != nil {
 		return err
 	}
@@ -125,7 +133,7 @@ func (c *CommitSig) Encode(w *bytes.Buffer, pver uint32) error {
 		return err
 	}
 
-	return WriteBytes(w, c.ExtraData)
+	return WriteBytes(w, extraData)
 }
 
 // MsgType returns the integer uniquely identifying this message type on the