state_migration.hpp

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#pragma once
 
#include <cstdint>
#include <functional>
#include <optional>
#include <span>
#include <vector>
 
namespace pulp::state {

class StateMigrationRegistry {
public:
    using MigrationFn =
        std::function<bool(std::span<const uint8_t> source,
                           std::vector<uint8_t>& destination)>;
 
    bool register_migration(uint32_t from_version,
                            uint32_t to_version,
                            MigrationFn migration);
 
    [[nodiscard]] bool has_migration_from(uint32_t from_version) const;
 
    [[nodiscard]] std::optional<std::vector<uint8_t>>
    migrate(std::span<const uint8_t> source, uint32_t target_version) const;
 
private:
    struct Entry {
        uint32_t from_version = 0;
        uint32_t to_version = 0;
        MigrationFn migration;
    };
 
    const Entry* find(uint32_t from_version) const;
 
    std::vector<Entry> migrations_;
};
 
[[nodiscard]] std::optional<uint32_t>
serialized_state_version(std::span<const uint8_t> source);
 
} // namespace pulp::state