Repository: bitcoin/bitcoin
File: src/node/utxo_snapshot.h (C/C++)

Code before:
//! The file in the snapshot chainstate dir which stores the base blockhash. This is
//! needed to reconstruct snapshot chainstates on init.
//!
//! Because we only allow loading a single snapshot at a time, there will only be one
//! chainstate directory with this filename present within it.
const fs::path SNAPSHOT_BLOCKHASH_FILENAME{"base_blockhash"};

//! Write out the blockhash of the snapshot base block that was used to construct
//! this chainstate. This value is read in during subsequent initializations and
//! used to reconstruct snapshot-based chainstates.
bool WriteSnapshotBaseBlockhash(Chainstate& snapshot_chainstate)
    EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

//! Read the blockhash of the snapshot base block that was used to construct the
//! chainstate.
std::optional<uint256> ReadSnapshotBaseBlockhash(fs::path chaindir)
    EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

//! Suffix appended to the chainstate (leveldb) dir when created based upon
//! a snapshot.
constexpr std::string_view SNAPSHOT_CHAINSTATE_SUFFIX = "_snapshot";


//! Return a path to the snapshot-based chainstate dir, if one exists.
std::optional<fs::path> FindSnapshotChainstateDir(const fs::path& data_dir);

} // namespace node

#endif // BITCOIN_NODE_UTXO_SNAPSHOT_H


Review comment (bug):
nit: seems like the second parameter (`std::error_code{}`) isn't needed (here and in all other instances below)
```suggestion
            throw std::ios_base::failure("Invalid UTXO set snapshot magic bytes. Please check if this is indeed a snapshot file or if you are using an outdated snapshot format.");
```

Code after:
    SnapshotMetadata() { }
    SnapshotMetadata(
        const uint256& base_blockhash,
        const int base_blockheight,
        uint64_t coins_count) :
            m_base_blockhash(base_blockhash),
            m_base_blockheight(base_blockheight),
            m_coins_count(coins_count) { }

    template <typename Stream>
    inline void Serialize(Stream& s) const {
        s << SNAPSHOT_MAGIC_BYTES;
        s << m_version;
        s << Params().MessageStart();
        s << m_base_blockheight;
        s << m_base_blockhash;
        s << m_coins_count;
    }

    template <typename Stream>
    inline void Unserialize(Stream& s) {
        // Read the snapshot magic bytes
        std::array<uint8_t, SNAPSHOT_MAGIC_BYTES.size()> snapshot_magic;
        s >> snapshot_magic;
        if (snapshot_magic != SNAPSHOT_MAGIC_BYTES) {
            throw std::ios_base::failure("Invalid UTXO set snapshot magic bytes. Please check if this is indeed a snapshot file or if you are using an outdated snapshot format.");
        }

        // Read the version
        uint16_t version;
        s >> version;
        if (m_supported_versions.find(version) == m_supported_versions.end()) {
            throw std::ios_base::failure(strprintf("Version of snapshot %s does not match any of the supported versions.", version));
        }

        // Read the network magic (pchMessageStart)
        MessageStartChars message;
        s >> message;
        if (!std::equal(message.begin(), message.end(), Params().MessageStart().data())) {
            auto metadata_network = GetNetworkForMagic(message);
            if (metadata_network) {
                std::string network_string{ChainTypeToString(metadata_network.value())};
                throw std::ios_base::failure(strprintf("The network of the snapshot (%s) does not match the network of this node (%s).", network_string, Params().GetChainTypeString()));
            } else {
                throw std::ios_base::failure("This snapshot has been created for an unrecognized network. This could be a custom signet, a new testnet or possibly caused by data corruption.");
            }
        }

        s >> m_base_blockheight;
        s >> m_base_blockhash;
        s >> m_coins_count;