Clarify current salt link comment

Author: timc995

src/cracker.c

@@ -93,10 +93,10 @@ static int crk_key_index, crk_last_key;
 static void *crk_last_salt;
 
 /*
- * Experimental optimization: while crk_salt_loop() is walking the salt
- * linked list, keep the address of the link pointing at the current salt.
- * This permits O(1) unlinking of the current salt instead of scanning the
- * list from its head for every successful crack.
+ * While crk_salt_loop() walks the salt linked list, keep a pointer to the
+ * link that references the current salt.  Using a pointer-to-pointer lets
+ * crk_remove_salt() update that link directly when unlinking the current
+ * salt, avoiding a scan from the head of the list.
  */
 static struct db_salt **crk_current_salt_link;
 static struct db_keys *crk_guesses;