CompressedFileAdapter.hh

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#ifndef COMPRESSEDFILEADAPTER_HH
#define COMPRESSEDFILEADAPTER_HH
 
#include "FileBase.hh"
#include "MemBuffer.hh"
#include <memory>
 
namespace openmsx {
 
class CompressedFileAdapter : public FileBase
{
public:
        struct Decompressed {
                MemBuffer<uint8_t> buf;
                std::string originalName;
                std::string cachedURL;
                time_t cachedModificationDate;
                unsigned useCount = 0;
        };
 
        void read(std::span<uint8_t> buffer) final;
        void write(std::span<const uint8_t> buffer) final;
        [[nodiscard]] std::span<const uint8_t> mmap() final;
        void munmap() final;
        [[nodiscard]] size_t getSize() final;
        void seek(size_t pos) final;
        [[nodiscard]] size_t getPos() final;
        void truncate(size_t size) final;
        void flush() final;
        [[nodiscard]] const std::string& getURL() const final;
        [[nodiscard]] std::string_view getOriginalName() final;
        [[nodiscard]] bool isReadOnly() const final;
        [[nodiscard]] time_t getModificationDate() final;
 
protected:
        explicit CompressedFileAdapter(std::unique_ptr<FileBase> file);
        ~CompressedFileAdapter() override;
        virtual void decompress(FileBase& file, Decompressed& decompressed) = 0;
 
private:
        void decompress();
 
private:
        // invariant: exactly one of 'file' and 'decompressed' is '!= nullptr'
        std::unique_ptr<FileBase> file;
        const Decompressed* decompressed = nullptr;
        size_t pos = 0;
};
 
} // namespace openmsx
 
#endif