headerssync.h

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// Copyright (c) 2022-present The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_HEADERSSYNC_H
#define BITCOIN_HEADERSSYNC_H

#include <arith_uint256.h>
#include <chain.h>
#include <consensus/params.h>
#include <net.h>
#include <primitives/block.h>
#include <uint256.h>
#include <util/bitdeque.h>
#include <util/hasher.h>

#include <deque>
#include <vector>

// A compressed CBlockHeader, which leaves out the prevhash
struct CompressedHeader {
    // header
    int32_t nVersion{0};
    uint256 hashMerkleRoot;
    uint32_t nTime{0};
    uint32_t nBits{0};
    uint32_t nNonce{0};

    CompressedHeader()
    {
        hashMerkleRoot.SetNull();
    }

    explicit CompressedHeader(const CBlockHeader& header)
        : nVersion{header.nVersion},
          hashMerkleRoot{header.hashMerkleRoot},
          nTime{header.nTime},
          nBits{header.nBits},
          nNonce{header.nNonce}
    {
    }

    CBlockHeader GetFullHeader(const uint256& hash_prev_block) const
    {
        CBlockHeader ret;
        ret.nVersion = nVersion;
        ret.hashPrevBlock = hash_prev_block;
        ret.hashMerkleRoot = hashMerkleRoot;
        ret.nTime = nTime;
        ret.nBits = nBits;
        ret.nNonce = nNonce;
        return ret;
    };
};

class HeadersSyncState {
public:
    ~HeadersSyncState() = default;

    enum class State {
        PRESYNC,
        REDOWNLOAD,
        FINAL
    };

    State GetState() const { return m_download_state; }

    int64_t GetPresyncHeight() const { return m_current_height; }

    uint32_t GetPresyncTime() const { return m_last_header_received.nTime; }

    arith_uint256 GetPresyncWork() const { return m_current_chain_work; }

    HeadersSyncState(NodeId id, const Consensus::Params& consensus_params,
                     const HeadersSyncParams& params, const CBlockIndex& chain_start,
                     const arith_uint256& minimum_required_work);

    struct ProcessingResult {
        std::vector<CBlockHeader> pow_validated_headers;
        bool success{false};
        bool request_more{false};
    };

    ProcessingResult ProcessNextHeaders(std::span<const CBlockHeader>
            received_headers, bool full_headers_message);

    CBlockLocator NextHeadersRequestLocator() const;

protected:
    const size_t m_commit_offset;

private:
    void Finalize();

    bool ValidateAndStoreHeadersCommitments(std::span<const CBlockHeader> headers);

    bool ValidateAndProcessSingleHeader(const CBlockHeader& current);

    bool ValidateAndStoreRedownloadedHeader(const CBlockHeader& header);

    std::vector<CBlockHeader> PopHeadersReadyForAcceptance();

private:
    const NodeId m_id;

    const Consensus::Params& m_consensus_params;

    const HeadersSyncParams m_params;

    const CBlockIndex& m_chain_start;

    const arith_uint256 m_minimum_required_work;

    arith_uint256 m_current_chain_work;

    const SaltedUint256Hasher m_hasher;

    bitdeque<> m_header_commitments;

    uint64_t m_max_commitments{0};

    CBlockHeader m_last_header_received;

    int64_t m_current_height{0};

    std::deque<CompressedHeader> m_redownloaded_headers;

    int64_t m_redownload_buffer_last_height{0};

    uint256 m_redownload_buffer_last_hash;

    uint256 m_redownload_buffer_first_prev_hash;

    arith_uint256 m_redownload_chain_work;

    bool m_process_all_remaining_headers{false};

    State m_download_state{State::PRESYNC};
};

#endif // BITCOIN_HEADERSSYNC_H