Add detail::has_constant_size

include/boost/hash2/detail/has_constant_size.hpp

@@ -0,0 +1,25 @@
+#ifndef BOOST_HASH2_DETAIL_HAS_CONSTANT_SIZE_HPP_INCLUDED
+#define BOOST_HASH2_DETAIL_HAS_CONSTANT_SIZE_HPP_INCLUDED
+
+// Copyright 2023 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/mp11/integral.hpp>
+#include <boost/mp11/utility.hpp>
+
+namespace boost
+{
+namespace hash2
+{
+namespace detail
+{
+
+template<class T> using has_constant_size_impl = mp11::mp_size_t< T().size() >;
+template<class T> using has_constant_size = mp11::mp_valid<has_constant_size_impl, T>;
+
+} // namespace detail
+} // namespace hash2
+} // namespace boost
+
+#endif // #ifndef BOOST_HASH2_DETAIL_HAS_CONSTANT_SIZE_HPP_INCLUDED

test/Jamfile

@@ -1,4 +1,4 @@
-# Copyright 2017-2019 Peter Dimov
+# Copyright 2017-2023 Peter Dimov
 # Distributed under the Boost Software License, Version 1.0.
 
 import testing ;
@@ -11,6 +11,7 @@ run is_contiguous_range.cpp ;
 run is_unordered_range.cpp ;
 run is_tuple_like.cpp ;
 run endian.cpp ;
+run has_constant_size.cpp ;
 
 # helpers
 

test/has_constant_size.cpp

@@ -0,0 +1,91 @@
+// Copyright 2023 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/hash2/detail/has_constant_size.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <boost/array.hpp>
+#include <string>
+#include <vector>
+#include <list>
+#include <deque>
+#include <set>
+#include <map>
+#include <array>
+#include <forward_list>
+#include <unordered_set>
+#include <unordered_map>
+
+struct X
+{
+};
+
+int main()
+{
+    using boost::hash2::detail::has_constant_size;
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size<void>));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size<void const>));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size<int>));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size<int const>));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size<X>));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size<X const>));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size<int[2]>));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size<int const[2]>));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size<std::string>));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size<std::string const>));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size<std::wstring>));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size<std::wstring const>));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::vector<X> >));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::vector<X> const >));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::deque<X> >));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::deque<X> const >));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::set<int> >));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::set<int> const >));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::multiset<int> >));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::multiset<int> const >));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::map<int, X> >));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::map<int, X> const >));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::multimap<int, X> >));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::multimap<int, X> const >));
+
+    BOOST_TEST_TRAIT_TRUE((has_constant_size< std::array<X, 2> >));
+    BOOST_TEST_TRAIT_TRUE((has_constant_size< std::array<X, 2> const >));
+
+    BOOST_TEST_TRAIT_TRUE((has_constant_size< std::array<X, 0> >));
+    BOOST_TEST_TRAIT_TRUE((has_constant_size< std::array<X, 0> const >));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::forward_list<X> >));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::forward_list<X> const >));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::unordered_set<int> >));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::unordered_set<int> const >));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::unordered_multiset<int> >));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::unordered_multiset<int> const >));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::unordered_map<int, X> >));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::unordered_map<int, X> const >));
+
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::unordered_multimap<int, X> >));
+    BOOST_TEST_TRAIT_FALSE((has_constant_size< std::unordered_multimap<int, X> const >));
+
+    BOOST_TEST_TRAIT_TRUE((has_constant_size< boost::array<X, 2> >));
+    BOOST_TEST_TRAIT_TRUE((has_constant_size< boost::array<X, 2> const >));
+
+    BOOST_TEST_TRAIT_TRUE((has_constant_size< boost::array<X, 0> >));
+    BOOST_TEST_TRAIT_TRUE((has_constant_size< boost::array<X, 0> const >));
+
+    return boost::report_errors();
+}