Lots of work on unicode support

luprex/cpp/drv/drvutil.hpp

@@ -46,6 +46,23 @@ std::string package_lua_source(const std::filesystem::path &base, std::ostream *
 //
 void split_target(std::string_view target, std::string &cert, std::string &host, std::string &port);
 
+// Return true if the unicode codepoint can be converted to a single 16-bit wchar_t.
+//
+bool is_single_wchar_t(char32_t c);
+
+// Convert a codepoint string into a UTF8-string.
+// If the codepoint string contains invalid codepoints, they're silently dropped.
+//
+std::string to_utf8(const std::u32string &cps);
+
+// Convert a UTF8 string to a codepoint 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
+// utf-8 sequence.  Returns the Codepoint string and the number of bytes consumed.
+//
+std::u32string from_utf8(std::string_view source, int *consumed);
+
 // Get a system error message, in an OS-independent manner.
 //
 // These versions of strerror is thread-safe, and it never fails