1 files changed, 57 insertions, 0 deletions

diff --git a/src/core/file_sys/vfs/vfs_concat.h b/src/core/file_sys/vfs/vfs_concat.h
new file mode 100644
index 000000000..6d12af762
--- /dev/null
+++ b/src/core/file_sys/vfs/vfs_concat.h
@@ -0,0 +1,57 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <compare>
+#include <map>
+#include <memory>
+#include "core/file_sys/vfs/vfs.h"
+
+namespace FileSys {
+
+// Class that wraps multiple vfs files and concatenates them, making reads seamless. Currently
+// read-only.
+class ConcatenatedVfsFile : public VfsFile {
+private:
+    struct ConcatenationEntry {
+        u64 offset;
+        VirtualFile file;
+
+        auto operator<=>(const ConcatenationEntry& other) const {
+            return this->offset <=> other.offset;
+        }
+    };
+    using ConcatenationMap = std::vector<ConcatenationEntry>;
+
+    explicit ConcatenatedVfsFile(std::string&& name,
+                                 std::vector<ConcatenationEntry>&& concatenation_map);
+    bool VerifyContinuity() const;
+
+public:
+    ~ConcatenatedVfsFile() override;
+
+    /// Wrapper function to allow for more efficient handling of files.size() == 0, 1 cases.
+    static VirtualFile MakeConcatenatedFile(std::string&& name, std::vector<VirtualFile>&& files);
+
+    /// Convenience function that turns a map of offsets to files into a concatenated file, filling
+    /// gaps with a given filler byte.
+    static VirtualFile MakeConcatenatedFile(u8 filler_byte, std::string&& name,
+                                            std::vector<std::pair<u64, VirtualFile>>&& files);
+
+    std::string GetName() const override;
+    std::size_t GetSize() const override;
+    bool Resize(std::size_t new_size) override;
+    VirtualDir GetContainingDirectory() const override;
+    bool IsWritable() const override;
+    bool IsReadable() const override;
+    std::size_t Read(u8* data, std::size_t length, std::size_t offset) const override;
+    std::size_t Write(const u8* data, std::size_t length, std::size_t offset) override;
+    bool Rename(std::string_view new_name) override;
+
+private:
+    ConcatenationMap concatenation_map;
+    std::string name;
+};
+
+} // namespace FileSys