add u16string_view.

src/string_view.hh

@@ -9,7 +9,11 @@
 
 namespace pEp
 {
-    typedef std::string_view string_view;
+    template<class CharT>
+    using basic_string_view = std::basic_string_view<CharT>;
+    
+    typedef std::string_view       string_view;
+    typedef std::u16string_view u16string_view;
 }
 
 #else // in C++11 / C++14 use boost::string_view instead.
@@ -17,18 +21,24 @@ namespace pEp
 
 namespace pEp
 {
-    typedef boost::string_view string_view;
+    template<class CharT>
+    using basic_string_view = boost::basic_string_view<CharT>;
+    
+    typedef boost::string_view       string_view;
+    typedef boost::u16string_view u16string_view;
 
     // boost::string_view does not provide these operations, neither by boost nor by the stdlib. :-(
+    template<class CharT>
     inline
-    std::string& operator+=(std::string& s, const string_view v)
+    std::basic_string<CharT>& operator+=(std::basic_string<CharT>& s, const basic_string_view<CharT> v)
     {
         s.append(v.data(), v.size());
         return s;
     }
 
+    template<class CharT>
     inline
-    std::string operator+(std::string s, const string_view v)
+    std::basic_string<CharT> operator+(std::basic_string<CharT> s, const basic_string_view<CharT> v)
     {
         return s += v;
     }