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#pragma once
#include <cstdint>
#include <optional>
#include <string>
#include <vector>
/**
* @file IStorageBackend.h
* @brief Abstract KV storage backend consumed by CursorManager and Merkle.
*
* Storage is strictly content-addressed: every value is stored under its
* SHA256 hex digest. Relation membership (which tuple hashes belong to a
* given relation) is now tracked via the Merkle B-tree maintained by the
* Merkle class, not by this interface. Only Put and Get are required.
*/
namespace nt
{
/**
* @interface IStorageBackend
* @brief Contract between CursorManager / Merkle and a physical storage engine.
*
* Two primitives are sufficient:
* - Put: store bytes, get back the content-address (SHA256 hex).
* - Get: retrieve bytes by content-address.
*
* Both are idempotent. The Merkle class stores node blobs via Put/Get and
* maintains insertion-order-independent relation membership on top of these
* two primitives.
*/
class IStorageBackend
{
public:
virtual ~IStorageBackend() = default;
/**
* @brief Stores a serialized value and returns its SHA256 hex hash.
*
* Idempotent: storing the same bytes twice does not create a duplicate.
* The returned hash is the only valid key for subsequent Get calls.
*/
virtual std::string Put(std::vector<uint8_t> value) = 0;
/**
* @brief Retrieves bytes by their SHA256 hex hash.
* @return The stored bytes, or std::nullopt when the hash is unknown.
*/
virtual std::optional<std::vector<uint8_t>> Get(const std::string& hash) = 0;
};
}
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