Add some comments for proof extraction

1 files changed, 8 insertions, 8 deletions

diff --git a/merkle.go b/merkle.go
index 9257c64..99fae7d 100644
--- a/merkle.go
+++ b/merkle.go
@@ -85,15 +85,15 @@ func (m *BFSMerkle) Build() []byte {
 func (m *BFSMerkle) Proof(id int64) [][]byte {
 	proof := make([][]byte, m.height)
 	proof[0] = make([]byte, hashSize)
-	m.ReadAt(proof[0], id*hashSize)
-	for i := 1; id > 0; i++ {
-		proof[i] = make([]byte, hashSize)
-		if id&1 == 0 {
-			m.ReadAt(proof[i], (id-1)*hashSize)
-		} else {
-			m.ReadAt(proof[i], (id+1)*hashSize)
+	m.ReadAt(proof[0], id*hashSize)                       // read the queried node
+	for height := int64(1); height < m.height; height++ { //construct the proof bottom-up
+		proof[height] = make([]byte, hashSize)
+		if id&1 == 0 { // right child, reading left sibling
+			m.ReadAt(proof[height], (id-1)*hashSize)
+		} else { // left child, reading right sibling
+			m.ReadAt(proof[height], (id+1)*hashSize)
 		}
-		id = (id - 1) >> 1
+		id = (id - 1) >> 1 // move to parent node
 	}
 	return proof
 }