1 files changed, 2 insertions, 2 deletions
diff --git a/lib/sha512.h b/lib/sha512.h
index 121e6c3a252..4460e6c9b76 100644
--- a/lib/sha512.h
+++ b/lib/sha512.h
@@ -44,8 +44,8 @@ struct sha512_ctx
   u64 state[8];
 
   u64 total[2];
-  size_t buflen;
-  u64 buffer[32];
+  size_t buflen;  /* ≥ 0, ≤ 256 */
+  u64 buffer[32]; /* 256 bytes; the first buflen bytes are in use */
 };
 
 /* Initialize structure containing state of computation. */