remove support for C++ < 17 and add more convenience functions

src/nfc.cc

@@ -708,6 +708,40 @@ char* strdup_NFC(string_view s)
 	return ret;
 }
 
+pEp_identity *identity_dup_NFC(const ::pEp_identity* value)
+{
+    ::pEp_identity* result = (::pEp_identity*) malloc(sizeof(::pEp_identity));
+    if (!result)
+        throw std::bad_alloc();
+
+    memcpy(result, value, sizeof(::pEp_identity));
+
+    result->address = pEp::strdup_NFC(value->address);
+    result->fpr = pEp::strdup_NFC(value->fpr);
+    result->user_id = pEp::strdup_NFC(value->user_id);
+    result->username = pEp::strdup_NFC(value->username);
+
+    return result;
+}
+
+::identity_list* identity_list_dup_NFC(const ::identity_list* value)
+{
+    ::identity_list* result = ::new_identity_list(nullptr);
+    if (!result)
+        throw std::bad_alloc();
+    
+    const ::identity_list* il = value;
+    ::identity_list* ir = result;
+
+    for (; il && il->ident; il = il->next) {
+        ir = ::identity_list_add(ir, identity_dup_NFC(il->ident));
+        if (!ir)
+            throw std::bad_alloc();
+    }
+
+    return result;
+}
+
 
 template class UTF<char>;
 template class UTF<char16_t>;

src/nfc.hh

@@ -8,6 +8,7 @@
 #include <string>
 #include <stdexcept>
 #include <iosfwd>
+#include <pEp/identity_list.h>
 
 namespace pEp {
 
@@ -109,9 +110,11 @@ std::basic_string<CharT> toNFC(basic_string_view<CharT> s);
 // creates a UTF-8-encoded NFC string from s
 std::string toNFC_8(u16string_view s);
 
-// convenience function to avoid ::strdup(pEp::toNFC<char>(text).c_str());
+// convenience functions to avoid ::strdup(pEp::toNFC<char>(text).c_str());
 // and unecessary temporary std::string etc.
 char* strdup_NFC(string_view s);
+pEp_identity *identity_dup_NFC(const ::pEp_identity* value);
+::identity_list* identity_list_dup_NFC(const ::identity_list* value);
 
 
 } // end of namespace pEp

src/string_view.hh

@@ -4,8 +4,7 @@
 #ifndef PEP_DATATYPES_STRING_VIEW_HH
 #define PEP_DATATYPES_STRING_VIEW_HH
 
-#if (__cplusplus >= 201606)  // std::string_view is C++17.
-#   include <string_view>
+#include <string_view>
 
 namespace pEp
 {
@@ -17,42 +16,6 @@ namespace pEp
     typedef std::u32string_view u32string_view;
 }
 
-#else // in C++11 / C++14 use boost::string_view instead.
-#   include <boost/utility/string_view.hpp>
-
-namespace pEp
-{
-    template<class CharT>
-    using basic_string_view = boost::basic_string_view<CharT>;
-    
-    typedef boost::string_view       string_view;
-    typedef boost::u16string_view u16string_view;
-    typedef boost::u32string_view u32string_view;
-
-    // boost::string_view does not provide these operations, neither by boost nor by the stdlib. :-(
-    template<class CharT>
-    inline
-    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::basic_string<CharT> operator+(std::basic_string<CharT> s, const basic_string_view<CharT> v)
-    {
-        return s += v;
-    }
-
- 
-//    using ::std::operator+=;
-//    using ::boost::operator+=;
-} // end of namespace pEp
-
-#endif // C++17 switch
-
-
 namespace pEp
 {
     constexpr