From 6cabea563e17d3cac984fde4453c630421d05222 Mon Sep 17 00:00:00 2001
From: Conner Fromknecht <conner@lightning.engineering>
Date: Fri, 22 Nov 2019 02:24:44 -0800
Subject: [PATCH] channeldb/invoices: optimize deserializeHtlcs

Instead of allocating a byte slice to read in each htlc's raw TLV
stream, use a LimitReader to truncate the stream to the proper length.
---
 channeldb/invoices.go | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/channeldb/invoices.go b/channeldb/invoices.go
index 1f17d5f3b..eaedd1781 100644
--- a/channeldb/invoices.go
+++ b/channeldb/invoices.go
@@ -1132,7 +1132,7 @@ func deserializeHtlcs(r io.Reader) (map[CircuitKey]*InvoiceHTLC, error) {
 
 	for {
 		// Read the length of the tlv stream for this htlc.
-		var streamLen uint64
+		var streamLen int64
 		if err := binary.Read(r, byteOrder, &streamLen); err != nil {
 			if err == io.EOF {
 				break
@@ -1141,11 +1141,9 @@ func deserializeHtlcs(r io.Reader) (map[CircuitKey]*InvoiceHTLC, error) {
 			return nil, err
 		}
 
-		streamBytes := make([]byte, streamLen)
-		if _, err := r.Read(streamBytes); err != nil {
-			return nil, err
-		}
-		streamReader := bytes.NewReader(streamBytes)
+		// Limit the reader so that it stops at the end of this htlc's
+		// stream.
+		htlcReader := io.LimitReader(r, streamLen)
 
 		// Decode the contents into the htlc fields.
 		var (
@@ -1172,7 +1170,7 @@ func deserializeHtlcs(r io.Reader) (map[CircuitKey]*InvoiceHTLC, error) {
 			return nil, err
 		}
 
-		if err := tlvStream.Decode(streamReader); err != nil {
+		if err := tlvStream.Decode(htlcReader); err != nil {
 			return nil, err
 		}