整理

include/boost/container_hash/hash_is_avalanching.hpp

@@ -0,0 +1,57 @@
+// Copyright 2025 Joaquin M Lopez Munoz.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#ifndef BOOST_HASH_HASH_IS_AVALANCHING_HPP_INCLUDED
+#define BOOST_HASH_HASH_IS_AVALANCHING_HPP_INCLUDED
+
+#include <type_traits>
+
+namespace boost
+{
+namespace hash_detail
+{
+
+template<class... Ts> struct make_void
+{
+    using type = void;
+};
+
+template<class... Ts> using void_t = typename make_void<Ts...>::type;
+
+template<class IsAvalanching> struct avalanching_value
+{
+    static constexpr bool value = IsAvalanching::value;
+};
+
+// may be explicitly marked as BOOST_DEPRECATED in the future
+template<> struct avalanching_value<void>
+{
+    static constexpr bool value = true;
+};
+
+template<class Hash, class = void> struct hash_is_avalanching_impl: std::false_type
+{
+};
+
+template<class Hash> struct hash_is_avalanching_impl<Hash, void_t<typename Hash::is_avalanching> >:
+    std::integral_constant<bool, avalanching_value<typename Hash::is_avalanching>::value>
+{
+};
+
+template<class Hash>
+struct hash_is_avalanching_impl<Hash, typename std::enable_if< ((void)Hash::is_avalanching, true) >::type>
+{
+  // Hash::is_avalanching is not a type: we don't define value to produce
+  // a compile error downstream
+};
+
+} // namespace hash_detail
+
+template<class Hash> struct hash_is_avalanching: hash_detail::hash_is_avalanching_impl<Hash>::type
+{
+};
+
+} // namespace boost
+
+#endif // #ifndef BOOST_HASH_HASH_IS_AVALANCHING_HPP_INCLUDED