From 34be7b1d776b4f5d86020f414b985f9a08f69975 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Thu, 21 Sep 2017 20:10:02 -0700
Subject: [PATCH] ircd::util: Add enum-flag accumulator util.

---
 include/ircd/util.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/include/ircd/util.h b/include/ircd/util.h
index 738082690..f938ce416 100644
--- a/include/ircd/util.h
+++ b/include/ircd/util.h
@@ -557,6 +557,28 @@ operator^=(Enum &a, const Enum &b)
 	return (a = (a ^ b));
 }
 
+template<class Enum,
+         class it>
+typename std::enable_if<std::is_enum<Enum>::value, typename std::underlying_type<Enum>::type>::type
+combine_flags(const it &begin,
+              const it &end)
+{
+	using type = typename std::underlying_type<Enum>::type;
+
+	return std::accumulate(begin, end, type(0), []
+	(auto ret, const auto &val)
+	{
+		return ret |= type(val);
+	});
+}
+
+template<class Enum>
+typename std::enable_if<std::is_enum<Enum>::value, typename std::underlying_type<Enum>::type>::type
+combine_flags(const std::initializer_list<Enum> &list)
+{
+	return combine_flags<Enum>(begin(list), end(list));
+}
+
 
 inline size_t
 size(std::ostream &s)