1 files changed, 80 insertions, 0 deletions
diff --git a/src/core/file_sys/fssystem/fssystem_switch_storage.h b/src/core/file_sys/fssystem/fssystem_switch_storage.h
new file mode 100644
index 000000000..2b43927cb
--- /dev/null
+++ b/src/core/file_sys/fssystem/fssystem_switch_storage.h
@@ -0,0 +1,80 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fs_i_storage.h"
+
+namespace FileSys {
+
+class RegionSwitchStorage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(RegionSwitchStorage);
+    YUZU_NON_MOVEABLE(RegionSwitchStorage);
+
+public:
+    struct Region {
+        s64 offset;
+        s64 size;
+    };
+
+public:
+    RegionSwitchStorage(VirtualFile&& i, VirtualFile&& o, Region r)
+        : m_inside_region_storage(std::move(i)), m_outside_region_storage(std::move(o)),
+          m_region(r) {}
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override {
+        // Process until we're done.
+        size_t processed = 0;
+        while (processed < size) {
+            // Process on the appropriate storage.
+            s64 cur_size = 0;
+            if (this->CheckRegions(std::addressof(cur_size), offset + processed,
+                                   size - processed)) {
+                m_inside_region_storage->Read(buffer + processed, cur_size, offset + processed);
+            } else {
+                m_outside_region_storage->Read(buffer + processed, cur_size, offset + processed);
+            }
+
+            // Advance.
+            processed += cur_size;
+        }
+
+        return size;
+    }
+
+    virtual size_t GetSize() const override {
+        return m_inside_region_storage->GetSize();
+    }
+
+private:
+    bool CheckRegions(s64* out_current_size, s64 offset, s64 size) const {
+        // Check if our region contains the access.
+        if (m_region.offset <= offset) {
+            if (offset < m_region.offset + m_region.size) {
+                if (m_region.offset + m_region.size <= offset + size) {
+                    *out_current_size = m_region.offset + m_region.size - offset;
+                } else {
+                    *out_current_size = size;
+                }
+                return true;
+            } else {
+                *out_current_size = size;
+                return false;
+            }
+        } else {
+            if (m_region.offset <= offset + size) {
+                *out_current_size = m_region.offset - offset;
+            } else {
+                *out_current_size = size;
+            }
+            return false;
+        }
+    }
+
+private:
+    VirtualFile m_inside_region_storage;
+    VirtualFile m_outside_region_storage;
+    Region m_region;
+};
+
+} // namespace FileSys