Memcard: Add ECC bytes when converting an ECC-less file card to a folder

MMCE cards such as MemCard PRO and SD2PSX store pages without ECC, so the
source is expanded to raw pages and rejected if it is not a whole number.

pcsx2-qt/Settings/MemoryCardConvertWorker.cpp

@@ -118,6 +118,16 @@ bool MemoryCardConvertWorker::ConvertToFolder(const std::string& srcFileName, co
 	}
 
 	std::vector<u8> sourceBuffer = sourceBufferOpt.value();
+
+	// MemCard PRO, SD2PSX and other MMCE cards have no ECC bytes
+	FileMcd_InsertECC(sourceBuffer);
+
+	if ((sourceBuffer.size() % FolderMemoryCard::PageSizeRaw) != 0)
+	{
+		Console.Error("%s(%s, %s, %d) File Memory Card is not a whole number of pages!", __FUNCTION__, srcFileName.c_str(), destFolderName.c_str(), type);
+		return false;
+	}
+
 	// Set progress bar to the literal number of bytes in the memcard.
 	// Plus two because there is a lag period after the Save calls complete
 	// where the progress bar stalls out; this lets us stop the progress bar

pcsx2/SIO/Memcard/MemoryCardFile.cpp

@@ -40,7 +40,7 @@ bool FileMcd_Open = false;
 // https://sourceforge.net/p/mymc-opl/code/ci/master/tree/ps2mc_ecc.py
 // Public domain license
 
-static u32 CalculateECC(u8* buf)
+static u32 CalculateECC(const u8* buf)
 {
 	const u8 parity_table[256] = {0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 1, 0, 0, 1, 0, 1, 1,
 		0, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0,
@@ -889,6 +889,36 @@ bool FileMcd_IsMemoryCardFormatted(std::FILE* fp)
 			std::memcmp(data, formatted_psx, sizeof(formatted_psx) - 1) == 0);
 }
 
+static bool IsNoECCSize(s64 size)
+{
+	return (size == _8mb || size == _16mb || size == _32mb || size == _64mb);
+}
+
+bool FileMcd_InsertECC(std::vector<u8>& buffer)
+{
+	if (!IsNoECCSize(static_cast<s64>(buffer.size())))
+		return false;
+
+	const size_t pages = buffer.size() / FolderMemoryCard::PageSize;
+	std::vector<u8> raw(pages * FolderMemoryCard::PageSizeRaw, 0xff);
+
+	for (size_t page = 0; page < pages; page++)
+	{
+		const u8* src = &buffer[page * FolderMemoryCard::PageSize];
+		u8* dst = &raw[page * FolderMemoryCard::PageSizeRaw];
+		std::memcpy(dst, src, FolderMemoryCard::PageSize);
+
+		for (int j = 0; j < 4; j++)
+		{
+			const u32 checksum = CalculateECC(&src[j * 128]);
+			std::memcpy(&dst[FolderMemoryCard::PageSize + (j * 3)], &checksum, 3);
+		}
+	}
+
+	buffer = std::move(raw);
+	return true;
+}
+
 std::vector<AvailableMcdInfo> FileMcd_GetAvailableCards(bool include_in_use_cards)
 {
 	std::vector<FILESYSTEM_FIND_DATA> files;

pcsx2/SIO/Memcard/MemoryCardFile.h

@@ -57,6 +57,7 @@ std::vector<AvailableMcdInfo> FileMcd_GetAvailableCards(bool include_in_use_card
 std::optional<AvailableMcdInfo> FileMcd_GetCardInfo(const std::string_view name);
 bool FileMcd_IsMemoryCardFormatted(const std::string& path);
 bool FileMcd_IsMemoryCardFormatted(std::FILE* fp);
+bool FileMcd_InsertECC(std::vector<u8>& buffer);
 bool FileMcd_CreateNewCard(const std::string_view name, MemoryCardType type, MemoryCardFileType file_type);
 bool FileMcd_RenameCard(const std::string_view name, const std::string_view new_name);
 bool FileMcd_DeleteCard(const std::string_view name);