DeltaBlock.hh

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#ifndef DELTA_BLOCK_HH
#define DELTA_BLOCK_HH
 
#define STATISTICS 0
 
#include "MemBuffer.hh"
 
#include <cstdint>
#include <memory>
#include <span>
#include <vector>
#ifdef DEBUG
#include "sha1.hh"
#endif
 
namespace openmsx {
 
class DeltaBlock
{
public:
#if STATISTICS
        virtual ~DeltaBlock();
#else
        virtual ~DeltaBlock() = default;
#endif
        virtual void apply(std::span<uint8_t> dst) const = 0;
 
protected:
        DeltaBlock() = default;
 
#ifdef DEBUG
public:
        Sha1Sum sha1;
#endif
 
#if STATISTICS
protected:
        static inline size_t globalAllocSize = 0;
        size_t allocSize;
#endif
};
 
 
class DeltaBlockCopy final : public DeltaBlock
{
public:
        explicit DeltaBlockCopy(std::span<const uint8_t> data);
        void apply(std::span<uint8_t> dst) const override;
        void compress(size_t size);
        [[nodiscard]] const uint8_t* getData();
 
private:
        [[nodiscard]] bool compressed() const { return compressedSize != 0; }
 
        MemBuffer<uint8_t> block;
        size_t compressedSize = 0;
};
 
 
class DeltaBlockDiff final : public DeltaBlock
{
public:
        DeltaBlockDiff(std::shared_ptr<DeltaBlockCopy> prev_,
                       std::span<const uint8_t> data);
        void apply(std::span<uint8_t> dst) const override;
        [[nodiscard]] size_t getDeltaSize() const;
 
private:
        const std::shared_ptr<DeltaBlockCopy> prev;
        const std::vector<uint8_t> delta; // TODO could be tweaked to use OutputBuffer
};
 
 
class LastDeltaBlocks
{
public:
        [[nodiscard]] std::shared_ptr<DeltaBlock> createNew(
                const void* id, std::span<const uint8_t> data);
        [[nodiscard]] std::shared_ptr<DeltaBlock> createNullDiff(
                const void* id, std::span<const uint8_t> data);
        void clear();
 
private:
        struct Info {
                Info(const void* id_, size_t size_)
                        : id(id_), size(size_) {}
 
                const void* id;
                size_t size;
                std::weak_ptr<DeltaBlockCopy> ref;
                std::weak_ptr<DeltaBlock> last;
                size_t accSize = 0;
        };
 
        std::vector<Info> infos;
};
 
} // namespace openmsx
 
#endif