From e969cff5f9006d4374b3fef5387a88d744766240 Mon Sep 17 00:00:00 2001
From: Paul Wells <paulwe@gmail.com>
Date: Wed, 9 Oct 2024 16:32:37 -0700
Subject: [PATCH] fix guid append write offset

---
 utils/guid/id.go      |  3 ++-
 utils/guid/id_test.go | 10 ++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/utils/guid/id.go b/utils/guid/id.go
index 2ffd852e..89da4e41 100644
--- a/utils/guid/id.go
+++ b/utils/guid/id.go
@@ -155,10 +155,11 @@ func Marshal[T livekit.Guid](id T) livekit.GuidBlock {
 }
 
 func MarshalAppend[T livekit.Guid](b []byte, id T) []byte {
+	off := len(b)
 	b = append(b, make([]byte, Size*3/4)...)
 	idb := []byte(id)[len(id)-Size:]
 	for i := 0; i < 3; i++ {
-		j := i * 3
+		j := i*3 + off
 		k := i * 4
 		b[j] = b57Index[idb[k]]<<2 | b57Index[idb[k+1]]>>4
 		b[j+1] = b57Index[idb[k+1]]<<4 | b57Index[idb[k+2]]>>2
diff --git a/utils/guid/id_test.go b/utils/guid/id_test.go
index d824524d..a03f46b4 100644
--- a/utils/guid/id_test.go
+++ b/utils/guid/id_test.go
@@ -31,6 +31,16 @@ func TestMarshalUnmarshal(t *testing.T) {
 	require.EqualValues(t, b0, b1)
 }
 
+func TestMarshalAppend(t *testing.T) {
+	id0 := livekit.RoomID(New(RoomPrefix))
+	id1 := livekit.RoomID(New(RoomPrefix))
+	var b []byte
+	b = MarshalAppend(b, id0)
+	b = MarshalAppend(b, id1)
+	require.Equal(t, id0, Unmarshal[livekit.RoomID](livekit.GuidBlock(b[0:])))
+	require.Equal(t, id1, Unmarshal[livekit.RoomID](livekit.GuidBlock(b[9:])))
+}
+
 func BenchmarkNew(b *testing.B) {
 	b.Run("new", func(b *testing.B) {
 		var guid string