vfs: add vfs_cached for romfs build

src/core/file_sys/vfs_cached.cpp

@@ -0,0 +1,63 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/vfs_cached.h"
+#include "core/file_sys/vfs_types.h"
+
+namespace FileSys {
+
+CachedVfsDirectory::CachedVfsDirectory(VirtualDir& source_dir)
+    : name(source_dir->GetName()), parent(source_dir->GetParentDirectory()) {
+    for (auto& dir : source_dir->GetSubdirectories()) {
+        dirs.emplace(dir->GetName(), std::make_shared<CachedVfsDirectory>(dir));
+    }
+    for (auto& file : source_dir->GetFiles()) {
+        files.emplace(file->GetName(), file);
+    }
+}
+
+CachedVfsDirectory::~CachedVfsDirectory() = default;
+
+VirtualFile CachedVfsDirectory::GetFile(std::string_view file_name) const {
+    auto it = files.find(file_name);
+    if (it != files.end()) {
+        return it->second;
+    }
+
+    return nullptr;
+}
+
+VirtualDir CachedVfsDirectory::GetSubdirectory(std::string_view dir_name) const {
+    auto it = dirs.find(dir_name);
+    if (it != dirs.end()) {
+        return it->second;
+    }
+
+    return nullptr;
+}
+
+std::vector<VirtualFile> CachedVfsDirectory::GetFiles() const {
+    std::vector<VirtualFile> out;
+    for (auto& [file_name, file] : files) {
+        out.push_back(file);
+    }
+    return out;
+}
+
+std::vector<VirtualDir> CachedVfsDirectory::GetSubdirectories() const {
+    std::vector<VirtualDir> out;
+    for (auto& [dir_name, dir] : dirs) {
+        out.push_back(dir);
+    }
+    return out;
+}
+
+std::string CachedVfsDirectory::GetName() const {
+    return name;
+}
+
+VirtualDir CachedVfsDirectory::GetParentDirectory() const {
+    return parent;
+}
+
+} // namespace FileSys