update boost

linx64/include/boost/json/string_view.hpp

@@ -0,0 +1,53 @@
+//
+// Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+// Official repository: https://github.com/boostorg/json
+//
+
+#ifndef BOOST_JSON_STRING_VIEW_HPP
+#define BOOST_JSON_STRING_VIEW_HPP
+
+#include <boost/json/detail/config.hpp>
+#include <boost/core/detail/string_view.hpp>
+#include <type_traits>
+#ifndef BOOST_NO_CXX17_HDR_STRING_VIEW
+# include <string_view>
+#endif
+
+namespace boost {
+namespace json {
+
+#ifdef BOOST_JSON_DOCS
+
+/** The type of string view used by the library.
+
+    The type has API equivalent to that of `std::string_view` and is
+    convertible to/from it.
+*/
+using string_view = __see_below__;
+
+#else
+
+using string_view = boost::core::string_view;
+
+#endif
+
+namespace detail {
+
+template<class T>
+using is_string_viewish = typename std::enable_if<
+    std::is_convertible<
+        T const&, string_view>::value &&
+    ! std::is_convertible<
+        T const&, char const*>::value
+            >::type;
+
+} // detail
+
+} // namespace json
+} // namespace boost
+
+#endif