DiscIO: Add support for CleanRip-style split ISOs.

Source/Core/DiscIO/SplitFileBlob.h

@@ -0,0 +1,50 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <memory>
+#include <optional>
+#include <string>
+#include <string_view>
+#include <vector>
+
+#include "Common/CommonTypes.h"
+#include "Common/IOFile.h"
+#include "DiscIO/Blob.h"
+
+namespace DiscIO
+{
+class SplitPlainFileReader final : public BlobReader
+{
+public:
+  static std::unique_ptr<SplitPlainFileReader> Create(std::string_view first_file_path);
+
+  BlobType GetBlobType() const override { return BlobType::SPLIT_PLAIN; }
+
+  u64 GetRawSize() const override { return m_size; }
+  u64 GetDataSize() const override { return m_size; }
+  DataSizeType GetDataSizeType() const override { return DataSizeType::Accurate; }
+
+  u64 GetBlockSize() const override { return 0; }
+  bool HasFastRandomAccessInBlock() const override { return true; }
+  std::string GetCompressionMethod() const override { return {}; }
+  std::optional<int> GetCompressionLevel() const override { return std::nullopt; }
+
+  bool Read(u64 offset, u64 nbytes, u8* out_ptr) override;
+
+private:
+  struct SingleFile
+  {
+    File::IOFile file;
+    u64 offset;
+    u64 size;
+  };
+
+  SplitPlainFileReader(std::vector<SingleFile> m_files);
+
+  std::vector<SingleFile> m_files;
+  u64 m_size;
+};
+
+}  // namespace DiscIO