More UTF-16 stuff

luprex/cpp/drv/drvutil.hpp

@@ -55,7 +55,7 @@ bool is_single_wchar_t(char32_t c);
 //
 std::string utf32_to_utf8(const std::u32string &cps);
 
-// Convert a UTF8 string to a codepoint string.
+// Convert a UTF8 string to a UTF32 string.
 // 
 // If the UTF8 string contains invalid sequences, they're silently dropped.
 // Some of the bytes may not be consumed, if the source ends with an unfinished
@@ -73,6 +73,12 @@ std::u32string utf8_to_utf32(std::string_view source, int *consumed);
 //
 std::u16string utf8_to_ucs2(std::string_view source, int *consumed);
 
+// Convert a UTF16 string to a UTF8 string.
+//
+// If the UTF16 string contains invalid sequences, they're silently dropped.
+//
+std::string utf16_to_utf8(std::u16string_view source);
+
 // Get a system error message, in an OS-independent manner.
 //
 // These versions of strerror is thread-safe, and it never fails