serialize: string_view serialization

Allows `stream << sv` to serialize from a string_view directly, without
converting to a string or similar first.

src/serialize.h

@@ -24,6 +24,7 @@
 #include <set>
 #include <span>
 #include <string>
+#include <string_view>
 #include <utility>
 #include <vector>
 
@@ -705,6 +706,12 @@ struct VectorFormatter
 template<typename Stream, typename C> void Serialize(Stream& os, const std::basic_string<C>& str);
 template<typename Stream, typename C> void Unserialize(Stream& is, std::basic_string<C>& str);
 
+/**
+ *  string_view
+ */
+template<typename Stream, typename C> void Serialize(Stream& os, const std::basic_string_view<C>& str);
+template<typename Stream, typename C> void Unserialize(Stream& is, std::basic_string_view<C>& str) = delete;
+
 /**
  * prevector
  */
@@ -807,7 +814,17 @@ void Unserialize(Stream& is, std::basic_string<C>& str)
         is.read(MakeWritableByteSpan(str));
 }
 
-
+/**
+ * string_view
+ */
+template<typename Stream, typename C>
+void Serialize(Stream& os, const std::basic_string_view<C>& str)
+{
+    WriteCompactSize(os, str.size());
+    if (!str.empty()) {
+        os.write(MakeByteSpan(str));
+    }
+}
 
 /**
  * prevector

src/test/serialize_tests.cpp

@@ -241,6 +241,16 @@ BOOST_AUTO_TEST_CASE(noncanonical)
     BOOST_CHECK_EXCEPTION(ReadCompactSize(ss), std::ios_base::failure, isCanonicalException);
 }
 
+BOOST_AUTO_TEST_CASE(string_view)
+{
+    const std::string_view sv{"hello, world"};
+    DataStream ss;
+    ss << sv;
+    std::string s;
+    ss >> s;
+    BOOST_CHECK_EQUAL(sv, s);
+}
+
 BOOST_AUTO_TEST_CASE(class_methods)
 {
     int intval(100);