From 73245554f9159afa2c0092f4170a02a91e0858ef Mon Sep 17 00:00:00 2001
From: qmuntal <qmuntaldiaz@microsoft.com>
Date: Fri, 29 Sep 2023 14:39:13 +0200
Subject: [PATCH] add more docs

---
 cng/hkdf.go | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/cng/hkdf.go b/cng/hkdf.go
index f3dbb06..8467f3e 100644
--- a/cng/hkdf.go
+++ b/cng/hkdf.go
@@ -37,8 +37,11 @@ type hkdf struct {
 	info []byte
 
 	hashLen int
-	buf     []byte
-	n       int
+	n       int // count of bytes requested from Read
+	// buf contains the derived data.
+	// len(buf) can be larger than n, as Read may derive
+	// more data than requested and cache it in buf.
+	buf []byte
 }
 
 func (c *hkdf) finalize() {