2 files changed, 178 insertions, 0 deletions

diff --git a/src/core/file_sys/vfs_layered.cpp b/src/core/file_sys/vfs_layered.cpp
new file mode 100644
index 000000000..802f49384
--- /dev/null
+++ b/src/core/file_sys/vfs_layered.cpp
@@ -0,0 +1,128 @@
+// Copyright 2018 yuzu emulator team
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <algorithm>
+#include <utility>
+#include "core/file_sys/vfs_layered.h"
+
+namespace FileSys {
+
+VirtualDir LayerDirectories(std::vector<VirtualDir> dirs, std::string name) {
+    if (dirs.empty())
+        return nullptr;
+    if (dirs.size() == 1)
+        return dirs[0];
+
+    return std::shared_ptr<VfsDirectory>(new LayeredVfsDirectory(std::move(dirs), std::move(name)));
+}
+
+LayeredVfsDirectory::LayeredVfsDirectory(std::vector<VirtualDir> dirs, std::string name)
+    : dirs(std::move(dirs)), name(std::move(name)) {}
+
+std::shared_ptr<VfsFile> LayeredVfsDirectory::GetFileRelative(std::string_view path) const {
+    VirtualFile file;
+    for (const auto& layer : dirs) {
+        file = layer->GetFileRelative(path);
+        if (file != nullptr)
+            return file;
+    }
+
+    return nullptr;
+}
+
+std::shared_ptr<VfsDirectory> LayeredVfsDirectory::GetDirectoryRelative(
+    std::string_view path) const {
+    std::vector<VirtualDir> out;
+    for (const auto& layer : dirs) {
+        const auto dir = layer->GetDirectoryRelative(path);
+        if (dir != nullptr)
+            out.push_back(dir);
+    }
+
+    return LayerDirectories(out);
+}
+
+std::shared_ptr<VfsFile> LayeredVfsDirectory::GetFile(std::string_view name) const {
+    return GetFileRelative(name);
+}
+
+std::shared_ptr<VfsDirectory> LayeredVfsDirectory::GetSubdirectory(std::string_view name) const {
+    return GetDirectoryRelative(name);
+}
+
+std::string LayeredVfsDirectory::GetFullPath() const {
+    return dirs[0]->GetFullPath();
+}
+
+std::vector<std::shared_ptr<VfsFile>> LayeredVfsDirectory::GetFiles() const {
+    std::vector<VirtualFile> out;
+    for (const auto& layer : dirs) {
+        for (const auto& file : layer->GetFiles()) {
+            if (std::find_if(out.begin(), out.end(), [&file](const VirtualFile& comp) {
+                    return comp->GetName() == file->GetName();
+                }) == out.end())
+                out.push_back(file);
+        }
+    }
+
+    return out;
+}
+
+std::vector<std::shared_ptr<VfsDirectory>> LayeredVfsDirectory::GetSubdirectories() const {
+    std::vector<std::string> names;
+    for (const auto& layer : dirs) {
+        for (const auto& sd : layer->GetSubdirectories()) {
+            if (std::find(names.begin(), names.end(), sd->GetName()) == names.end())
+                names.push_back(sd->GetName());
+        }
+    }
+
+    std::vector<VirtualDir> out;
+    for (const auto& subdir : names)
+        out.push_back(GetSubdirectory(subdir));
+
+    return out;
+}
+
+bool LayeredVfsDirectory::IsWritable() const {
+    return false;
+}
+
+bool LayeredVfsDirectory::IsReadable() const {
+    return true;
+}
+
+std::string LayeredVfsDirectory::GetName() const {
+    return name.empty() ? dirs[0]->GetName() : name;
+}
+
+std::shared_ptr<VfsDirectory> LayeredVfsDirectory::GetParentDirectory() const {
+    return dirs[0]->GetParentDirectory();
+}
+
+std::shared_ptr<VfsDirectory> LayeredVfsDirectory::CreateSubdirectory(std::string_view name) {
+    return nullptr;
+}
+
+std::shared_ptr<VfsFile> LayeredVfsDirectory::CreateFile(std::string_view name) {
+    return nullptr;
+}
+
+bool LayeredVfsDirectory::DeleteSubdirectory(std::string_view name) {
+    return false;
+}
+
+bool LayeredVfsDirectory::DeleteFile(std::string_view name) {
+    return false;
+}
+
+bool LayeredVfsDirectory::Rename(std::string_view name_) {
+    name = name_;
+    return true;
+}
+
+bool LayeredVfsDirectory::ReplaceFileWithSubdirectory(VirtualFile file, VirtualDir dir) {
+    return false;
+}
+} // namespace FileSys
diff --git a/src/core/file_sys/vfs_layered.h b/src/core/file_sys/vfs_layered.h
new file mode 100644
index 000000000..f345c2fb6
--- /dev/null
+++ b/src/core/file_sys/vfs_layered.h
@@ -0,0 +1,50 @@
+// Copyright 2018 yuzu emulator team
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include "core/file_sys/vfs.h"
+
+namespace FileSys {
+
+// Wrapper function to allow for more efficient handling of dirs.size() == 0, 1 cases.
+VirtualDir LayerDirectories(std::vector<VirtualDir> dirs, std::string name = "");
+
+// Class that stacks multiple VfsDirectories on top of each other, attempting to read from the first
+// one and falling back to the one after. The highest priority directory (overwrites all others)
+// should be element 0 in the dirs vector.
+class LayeredVfsDirectory : public VfsDirectory {
+    friend VirtualDir LayerDirectories(std::vector<VirtualDir> dirs, std::string name);
+
+    LayeredVfsDirectory(std::vector<VirtualDir> dirs, std::string name);
+
+public:
+    std::shared_ptr<VfsFile> GetFileRelative(std::string_view path) const override;
+    std::shared_ptr<VfsDirectory> GetDirectoryRelative(std::string_view path) const override;
+    std::shared_ptr<VfsFile> GetFile(std::string_view name) const override;
+    std::shared_ptr<VfsDirectory> GetSubdirectory(std::string_view name) const override;
+    std::string GetFullPath() const override;
+
+    std::vector<std::shared_ptr<VfsFile>> GetFiles() const override;
+    std::vector<std::shared_ptr<VfsDirectory>> GetSubdirectories() const override;
+    bool IsWritable() const override;
+    bool IsReadable() const override;
+    std::string GetName() const override;
+    std::shared_ptr<VfsDirectory> GetParentDirectory() const override;
+    std::shared_ptr<VfsDirectory> CreateSubdirectory(std::string_view name) override;
+    std::shared_ptr<VfsFile> CreateFile(std::string_view name) override;
+    bool DeleteSubdirectory(std::string_view name) override;
+    bool DeleteFile(std::string_view name) override;
+    bool Rename(std::string_view name) override;
+
+protected:
+    bool ReplaceFileWithSubdirectory(VirtualFile file, VirtualDir dir) override;
+
+private:
+    std::vector<VirtualDir> dirs;
+    std::string name;
+};
+
+} // namespace FileSys