[FS] Proper 8.3 filename conversion hopefully

src/core/kernel/directory_operations.cpp

@@ -1,4 +1,8 @@
+#include <array>
+#include <cctype>
 #include <filesystem>
+#include <string>
+#include <utility>
 
 #include "kernel.hpp"
 
@@ -9,6 +13,79 @@ namespace DirectoryOps {
 	};
 }
 
+// Helper to convert std::string to an 8.3 filename to mimic how Directory::Read works
+using ShortFilename = std::array<char, 9>;
+using ShortExtension = std::array<char, 4>;
+using Filename83 = std::pair<ShortFilename, ShortExtension>;
+
+// The input string should be the stem and extension together, not separately
+// Eg something like "boop.png", "panda.txt", etc
+Filename83 convertTo83(const std::string& path) {
+	ShortFilename filename;
+	ShortExtension extension;
+
+	// Convert a character to add it to the 8.3 name
+	// "Characters such as + are changed to the underscore _, and letters are put in uppercase"
+	// For now we put letters in uppercase until we find out what is supposed to be converted to _ and so on
+	auto convertCharacter = [](char c) { return (char) std::toupper(c); };
+
+	// List of forbidden character for 8.3 filenames, from Citra
+	// TODO: Use constexpr when C++20 support is solid
+	const std::string forbiddenChars = ".\"/\\[]:;=, ";
+
+	// By default space-initialize the whole name, append null terminator in the end for both the filename and extension
+	filename.fill(' ');
+	extension.fill(' ');
+	filename[filename.size() - 1] = '\0';
+	extension[extension.size() - 1] = '\0';
+
+	// Find the position of the dot in the string
+	auto dotPos = path.rfind('.');
+	// Wikipedia: If a file name has no extension, a trailing . has no effect
+	// Thus check if the last character is a dot and ignore it, prefering the previous dot if it exists
+	if (dotPos == path.size() - 1) {
+		dotPos = path.rfind('.', dotPos);  // Get previous dot
+	}
+
+	// If pointPos is not npos we have a valid dot character, and as such an extension
+	bool haveExtension = dotPos != std::string::npos;
+	int validCharacterCount = 0;
+	bool filenameTooBig = false;
+
+	// Parse characters until we're done OR until we reach 9 characters, in which case according to Wikipedia we must truncate to 6 letters
+	// And append ~1 in the end
+	for (auto c : path.substr(0, dotPos)) {
+		// Character is forbidden, we must ignore it
+		if (forbiddenChars.find(c) != std::string::npos) {
+			continue;
+		}
+
+		// We already have capped the amount of characters, thus our filename is too big
+		if (validCharacterCount == filename.size()) {
+			filenameTooBig = true;
+			break;
+		}
+		filename[validCharacterCount++] = convertCharacter(c); // Append character to filename
+	}
+
+	// Truncate name to 6 characters and denote that it is too big
+	// TODO: Wikipedia says we should also do this if the filename contains an invalid character, including spaces. Must test
+	if (filenameTooBig) {
+		filename[6] = '~';
+		filename[7] = '1';
+	}
+
+	if (haveExtension) {
+		int extensionLen = 0;
+		// Copy up to 3 characters from the dot onwards to the extension
+		for (auto c : path.substr(dotPos + 1, 3)) {
+			extension[extensionLen++] = convertCharacter(c);
+		}
+	}
+
+	return {filename, extension};
+}
+
 void Kernel::handleDirectoryOperation(u32 messagePointer, Handle directory) {
 	const u32 cmd = mem.read32(messagePointer);
 	switch (cmd) {
@@ -30,7 +107,6 @@ void Kernel::closeDirectory(u32 messagePointer, Handle directory) {
 	mem.write32(messagePointer + 4, Result::Success);
 }
 
-
 void Kernel::readDirectory(u32 messagePointer, Handle directory) {
 	const u32 entryCount = mem.read32(messagePointer + 4);
 	const u32 outPointer = mem.read32(messagePointer + 12);
@@ -52,13 +128,12 @@ void Kernel::readDirectory(u32 messagePointer, Handle directory) {
 	while (count < entryCount && session->currentEntry < session->entries.size()) {
 		const auto& entry = session->entries[session->currentEntry];
 		std::filesystem::path path = entry.path;
-		std::filesystem::path extension = path.extension();
+		std::filesystem::path filename = path.filename();
+
 		std::filesystem::path relative = path.lexically_relative(dirPath);
 		bool isDirectory = std::filesystem::is_directory(relative);
 
 		std::u16string nameU16 = relative.u16string();
-		std::string nameString = relative.string();
-		std::string extensionString = extension.string();
 
 		const u32 entryPointer = outPointer + (count * 0x228); // 0x228 is the size of a single entry
 		u32 utfPointer = entryPointer;
@@ -67,27 +142,27 @@ void Kernel::readDirectory(u32 messagePointer, Handle directory) {
 		u32 attributePointer = entryPointer + 0x21C;
 		u32 sizePointer = entryPointer + 0x220;
 
+		std::string filenameString = filename.string();
+		auto [shortFilename, shortExtension] = convertTo83(filenameString);
+
 		for (auto c : nameU16) {
 			mem.write16(utfPointer, u16(c));
 			utfPointer += sizeof(u16);
 		}
 		mem.write16(utfPointer, 0); // Null terminate the UTF16 name
 
-		for (auto c : nameString) {
-			//if (c == '.') continue; // Ignore initial dot
-
+		// Write 8.3 filename-extension
+		for (auto c : shortFilename) {
 			mem.write8(namePointer, u8(c));
 			namePointer += sizeof(u8);
 		}
-		mem.write8(namePointer, 0); // Null terminate 8.3 name
 
-		for (auto c : extensionString) {
+		for (auto c : shortExtension) {
 			mem.write8(extensionPointer, u8(c));
 			extensionPointer += sizeof(u8);
 		}
-		mem.write8(extensionPointer, 0); // Null terminate 8.3 extension
-		mem.write8(outPointer + 0x21A, 1); // Always 1 according to 3DBrew
 
+		mem.write8(outPointer + 0x21A, 1); // Always 1 according to 3DBrew
 		mem.write8(attributePointer, entry.isDirectory ? 1 : 0); // "Is directory" attribute
 
 		count++;                  // Increment number of read directories