vfs: Add ConcatenatedVfsFile

src/core/file_sys/vfs_concat.h

@@ -0,0 +1,41 @@
+// Copyright 2018 yuzu emulator team
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include <string_view>
+#include <boost/container/flat_map.hpp>
+#include "core/file_sys/vfs.h"
+
+namespace FileSys {
+
+// Wrapper function to allow for more efficient handling of files.size() == 0, 1 cases.
+VirtualFile ConcatenateFiles(std::vector<VirtualFile> files, std::string_view name = "");
+
+// Class that wraps multiple vfs files and concatenates them, making reads seamless. Currently
+// read-only.
+class ConcatenatedVfsFile : public VfsFile {
+    friend VirtualFile ConcatenateFiles(std::vector<VirtualFile> files, std::string_view name);
+
+    ConcatenatedVfsFile(std::vector<VirtualFile> files, std::string_view name);
+
+public:
+    std::string GetName() const override;
+    size_t GetSize() const override;
+    bool Resize(size_t new_size) override;
+    std::shared_ptr<VfsDirectory> GetContainingDirectory() const override;
+    bool IsWritable() const override;
+    bool IsReadable() const override;
+    size_t Read(u8* data, size_t length, size_t offset) const override;
+    size_t Write(const u8* data, size_t length, size_t offset) override;
+    bool Rename(std::string_view name) override;
+
+private:
+    // Maps starting offset to file -- more efficient.
+    boost::container::flat_map<u64, VirtualFile> files;
+    std::string name;
+};
+
+} // namespace FileSys