Add descriptor_by_name

include/boost/describe.hpp

@@ -14,5 +14,6 @@
 #include <boost/describe/enum_to_string.hpp>
 #include <boost/describe/enum_from_string.hpp>
 #include <boost/describe/operators.hpp>
+#include <boost/describe/descriptor_by_name.hpp>
 
 #endif // #ifndef BOOST_DESCRIBE_HPP_INCLUDED

include/boost/describe/descriptor_by_name.hpp

@@ -0,0 +1,52 @@
+#ifndef BOOST_DESCRIBE_DESCRIPTOR_BY_NAME_HPP_INCLUDED
+#define BOOST_DESCRIBE_DESCRIPTOR_BY_NAME_HPP_INCLUDED
+
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/describe/detail/config.hpp>
+
+#if defined(BOOST_DESCRIBE_CXX14)
+
+#include <boost/mp11/algorithm.hpp>
+#include <boost/mp11/bind.hpp>
+#include <boost/mp11/integral.hpp>
+
+namespace boost
+{
+namespace describe
+{
+
+namespace detail
+{
+
+// cx_streq already defined in members.hpp
+constexpr bool dbn_cx_streq( char const * s1, char const * s2 )
+{
+    for( ;; )
+    {
+        if( *s1 != *s2 ) return false;
+        if( *s1 == 0 ) return true;
+        ++s1;
+        ++s2;
+    }
+}
+
+template<class D, class N> using match_by_name = mp11::mp_bool<dbn_cx_streq(D::name, N::name())>;
+
+#define BOOST_DESCRIBE_MAKE_NAME_IMPL2(s, k) struct _boost_name_##s##_##k { static constexpr char const * name() { return #s; } }
+#define BOOST_DESCRIBE_MAKE_NAME_IMPL(s, k) BOOST_DESCRIBE_MAKE_NAME_IMPL2(s, k)
+
+} // namespace detail
+
+#define BOOST_DESCRIBE_MAKE_NAME(s) BOOST_DESCRIBE_MAKE_NAME_IMPL(s, __LINE__)
+
+template<class L, class N> using descriptor_by_name = mp11::mp_at<L, mp11::mp_find_if_q<L, mp11::mp_bind_back<detail::match_by_name, N>>>;
+
+} // namespace describe
+} // namespace boost
+
+#endif // defined(BOOST_DESCRIBE_CXX14)
+
+#endif // #ifndef BOOST_DESCRIBE_DESCRIPTOR_BY_NAME_HPP_INCLUDED

test/Jamfile

@@ -60,6 +60,8 @@ run enum_from_string_test.cpp ;
 run operator_eq_test.cpp ;
 run operator_lt_test.cpp ;
 
+run descriptor_by_name_test.cpp ;
+
 # examples
 
 obj describe_cxx14 : describe_cxx14.cpp ;

test/descriptor_by_name_test.cpp

@@ -0,0 +1,64 @@
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/describe/descriptor_by_name.hpp>
+#include <boost/describe/class.hpp>
+#include <boost/describe/members.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+#if !defined(BOOST_DESCRIBE_CXX14)
+
+#include <boost/config/pragma_message.hpp>
+
+BOOST_PRAGMA_MESSAGE("Skipping test because C++14 is not available")
+int main() {}
+
+#else
+
+struct X
+{
+    int a = 1;
+    int b = 2;
+};
+
+BOOST_DESCRIBE_STRUCT(X, (), (a, b))
+
+struct Y
+{
+    int a = 1;
+    int c = 3;
+};
+
+BOOST_DESCRIBE_STRUCT(Y, (), (a, c))
+
+int main()
+{
+    {
+        using L = boost::describe::describe_members<X, boost::describe::mod_any_access>;
+
+        using Na = BOOST_DESCRIBE_MAKE_NAME( a );
+        using Da = boost::describe::descriptor_by_name<L, Na>;
+        BOOST_TEST_CSTR_EQ( Da::name, "a" );
+
+        using Nb = BOOST_DESCRIBE_MAKE_NAME( b );
+        using Db = boost::describe::descriptor_by_name<L, Nb>;
+        BOOST_TEST_CSTR_EQ( Db::name, "b" );
+    }
+
+    {
+        using L = boost::describe::describe_members<Y, boost::describe::mod_any_access>;
+
+        using Na = BOOST_DESCRIBE_MAKE_NAME( a );
+        using Da = boost::describe::descriptor_by_name<L, Na>;
+        BOOST_TEST_CSTR_EQ( Da::name, "a" );
+
+        using Nc = BOOST_DESCRIBE_MAKE_NAME( c );
+        using Dc = boost::describe::descriptor_by_name<L, Nc>;
+        BOOST_TEST_CSTR_EQ( Dc::name, "c" );
+    }
+
+    return boost::report_errors();
+}
+
+#endif // !defined(BOOST_DESCRIBE_CXX14)