update CopyString & CopyWideString (#2884)

gframe/bufferio.h

@@ -82,14 +82,18 @@ public:
 		return CopyWStr(src, dst, N);
 	}
 	template<size_t N>
-	static void CopyString(const char* src, char(&dst)[N]) {
-		std::strncpy(dst, src, N - 1);
-		dst[N - 1] = 0;
+	static void CopyString(const char* src, char(&dst)[N], size_t len = N - 1) {
+		if(len >= N)
+			len = N - 1;
+		std::strncpy(dst, src, len);
+		dst[len] = 0;
 	}
 	template<size_t N>
-	static void CopyWideString(const wchar_t* src, wchar_t(&dst)[N]) {
-		std::wcsncpy(dst, src, N - 1);
-		dst[N - 1] = 0;
+	static void CopyWideString(const wchar_t* src, wchar_t(&dst)[N], size_t len = N - 1) {
+		if(len >= N)
+			len = N - 1;
+		std::wcsncpy(dst, src, len);
+		dst[len] = 0;
 	}
 	static bool IsHighSurrogate(unsigned int c) {
 		return (c >= 0xd800U && c <= 0xdbffU);

gframe/game.cpp

@@ -1234,11 +1234,8 @@ void Game::RefreshDeck(const wchar_t* deckpath, const std::function<void(const w
 	}
 	FileSystem::TraversalDir(deckpath, [additem](const wchar_t* name, bool isdir) {
 		if (!isdir && IsExtension(name, L".ydk")) {
-			size_t len = std::wcslen(name);
 			wchar_t deckname[256]{};
-			size_t count = std::min(len - 4, sizeof deckname / sizeof deckname[0] - 1);
-			std::wcsncpy(deckname, name, count);
-			deckname[count] = 0;
+			BufferIO::CopyWideString(name, deckname, std::wcslen(name) - 4);
 			additem(deckname);
 		}
 	});

gframe/menu_handler.cpp

@@ -428,8 +428,7 @@ bool MenuHandler::OnEvent(const irr::SEvent& event) {
 					wchar_t *dot = std::wcsrchr(open_file_name, L'.');
 					if(dash && dot && !mywcsncasecmp(dot, L".ydk", 4)) { // full path
 						wchar_t deck_name[256];
-						std::wcsncpy(deck_name, dash + 1, dot - dash - 1);
-						deck_name[dot - dash - 1] = L'\0';
+						BufferIO::CopyWideString(dash + 1, deck_name, dot - dash - 1);
 						mainGame->ebDeckname->setText(deck_name);
 						mainGame->cbDBCategory->setSelected(-1);
 						mainGame->cbDBDecks->setSelected(-1);
@@ -438,7 +437,7 @@ bool MenuHandler::OnEvent(const irr::SEvent& event) {
 						mainGame->cbDBDecks->setEnabled(false);
 					} else if(dash) { // has category
 						wchar_t deck_name[256];
-						std::wcsncpy(deck_name, dash + 1, 256);
+						BufferIO::CopyWideString(dash + 1, deck_name);
 						for(size_t i = 0; i < mainGame->cbDBDecks->getItemCount(); ++i) {
 							if(!std::wcscmp(mainGame->cbDBDecks->getItem(i), deck_name)) {
 								BufferIO::CopyWideString(deck_name, mainGame->gameConf.lastdeck);