HLE/FS: Always use 0x48000 as the high dword when opening the SharedExtData archive

The FS module overrides whatever value was in the saveid high dword with 0x48000 when trying to open the archive.

This fixes the problem where the Home Menu would create a few SharedExtData archives with 0x48000 as the saveid high, but then try to open them with 0 as the high value and fail.

src/core/file_sys/archive_extsavedata.cpp

@@ -131,6 +131,14 @@ public:
     }
 };
 
+struct ExtSaveDataArchivePath {
+    u32_le media_type;
+    u32_le save_low;
+    u32_le save_high;
+};
+
+static_assert(sizeof(ExtSaveDataArchivePath) == 12, "Incorrect path size");
+
 std::string GetExtSaveDataPath(const std::string& mount_point, const Path& path) {
     std::vector<u8> vec_data = path.AsBinary();
     const u32* data = reinterpret_cast<const u32*>(vec_data.data());
@@ -183,8 +191,27 @@ bool ArchiveFactory_ExtSaveData::Initialize() {
     return true;
 }
 
+Path ArchiveFactory_ExtSaveData::GetCorrectedPath(const Path& path) {
+    if (!shared)
+        return path;
+
+    static constexpr u32 SharedExtDataHigh = 0x48000;
+
+    ExtSaveDataArchivePath new_path;
+    std::memcpy(&new_path, path.AsBinary().data(), sizeof(new_path));
+
+    // The FS module overwrites the high value of the saveid when dealing with the SharedExtSaveData
+    // archive.
+    new_path.save_high = SharedExtDataHigh;
+
+    std::vector<u8> binary_data(sizeof(new_path));
+    std::memcpy(binary_data.data(), &new_path, binary_data.size());
+
+    return {binary_data};
+}
+
 ResultVal<std::unique_ptr<ArchiveBackend>> ArchiveFactory_ExtSaveData::Open(const Path& path) {
-    std::string fullpath = GetExtSaveDataPath(mount_point, path) + "user/";
+    std::string fullpath = GetExtSaveDataPath(mount_point, GetCorrectedPath(path)) + "user/";
     if (!FileUtil::Exists(fullpath)) {
         // TODO(Subv): Verify the archive behavior of SharedExtSaveData compared to ExtSaveData.
         // ExtSaveData seems to return FS_NotFound (120) when the archive doesn't exist.
@@ -200,14 +227,16 @@ ResultVal<std::unique_ptr<ArchiveBackend>> ArchiveFactory_ExtSaveData::Open(cons
 
 ResultCode ArchiveFactory_ExtSaveData::Format(const Path& path,
                                               const FileSys::ArchiveFormatInfo& format_info) {
+    auto corrected_path = GetCorrectedPath(path);
+
     // These folders are always created with the ExtSaveData
-    std::string user_path = GetExtSaveDataPath(mount_point, path) + "user/";
+    std::string user_path = GetExtSaveDataPath(mount_point, corrected_path) + "user/";
-    std::string boss_path = GetExtSaveDataPath(mount_point, path) + "boss/";
+    std::string boss_path = GetExtSaveDataPath(mount_point, corrected_path) + "boss/";
     FileUtil::CreateFullPath(user_path);
     FileUtil::CreateFullPath(boss_path);
 
     // Write the format metadata
-    std::string metadata_path = GetExtSaveDataPath(mount_point, path) + "metadata";
+    std::string metadata_path = GetExtSaveDataPath(mount_point, corrected_path) + "metadata";
     FileUtil::IOFile file(metadata_path, "wb");
 
     if (!file.IsOpen()) {

src/core/file_sys/archive_extsavedata.h

@@ -56,6 +56,9 @@ private:
      * See GetExtSaveDataPath for the code that extracts this data from an archive path.
      */
     std::string mount_point;
+
+    /// Returns a path with the correct SaveIdHigh value for Shared extdata paths.
+    Path GetCorrectedPath(const Path& path);
 };
 
 /**