Added path_to_plain_ascii for use by driver-ssl

luprex/core/cpp/driver-mingw.cpp

@@ -8,13 +8,13 @@
 #include "driver-util.hpp"
 #include "driver-ssl.hpp"
 #include "drivenengine.hpp"
-#include "util.hpp"
 #include "source.hpp"
 
 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <cassert>
+#include <filesystem>
 
 #include <winsock2.h>
 #include <ws2tcpip.h>
@@ -29,6 +29,20 @@
 #include <openssl/bio.h>
 #include <openssl/pem.h>
 
+// OpenSSL requires plain ascii pathnames.  Returns empty string
+// if the path cannot be converted to plain ascii.
+std::string path_to_plain_ascii(const std::filesystem::path &path) {
+	std::wstring s = path.native();
+	for (wchar_t c : s) {
+		if ((c < 1) || (c > 127)) return "";
+	}
+	std::ostringstream oss;
+	for (wchar_t c : s) {
+		oss << ((char)c);
+	}
+	return oss.str();
+}
+	
 static void set_nonblocking(SOCKET sock) {
     u_long mode = 1;  // 1 to enable non-blocking socket
     int status = ioctlsocket(sock, FIONBIO, &mode);