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

Code before:
#include <uint256.h>
#include <util/fs.h>

#include <cstdint>
#include <optional>
#include <string_view>

class Chainstate;

namespace node {
//! Metadata describing a serialized version of a UTXO set from which an
//! assumeutxo Chainstate can be constructed.
class SnapshotMetadata
{
public:
    //! The hash of the block that reflects the tip of the chain for the
    //! UTXO set contained in this snapshot.
    uint256 m_base_blockhash;

    //! The number of coins in the UTXO set contained in this snapshot. Used
    //! during snapshot load to estimate progress of UTXO set reconstruction.
    uint64_t m_coins_count = 0;

    SnapshotMetadata() { }
    SnapshotMetadata(
        const uint256& base_blockhash,
        uint64_t coins_count) :
            m_base_blockhash(base_blockhash),
            m_coins_count(coins_count) { }

    SERIALIZE_METHODS(SnapshotMetadata, obj) { READWRITE(obj.m_base_blockhash, obj.m_coins_count); }
};

//! 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);


Review comment (suggestion):
nit: for variables that are (de)serialized, it's imho preferred if the data type size is explicit
```suggestion
    uint32_t m_base_blockheight;
```

Code after:
#include <serialize.h>
#include <sync.h>
#include <uint256.h>
#include <util/chaintype.h>
#include <util/fs.h>

#include <cstdint>
#include <optional>
#include <string_view>

// UTXO set snapshot magic bytes
static constexpr std::array<uint8_t, 5> SNAPSHOT_MAGIC_BYTES = {'u', 't', 'x', 'o', 0xff};

class Chainstate;

namespace node {
//! Metadata describing a serialized version of a UTXO set from which an
//! assumeutxo Chainstate can be constructed.
class SnapshotMetadata
{
    const uint16_t m_version{1};
    const std::set<uint16_t> m_supported_versions{1};
public:
    //! The hash of the block that reflects the tip of the chain for the
    //! UTXO set contained in this snapshot.
    uint256 m_base_blockhash;
    uint32_t m_base_blockheight;


    //! The number of coins in the UTXO set contained in this snapshot. Used
    //! during snapshot load to estimate progress of UTXO set reconstruction.
    uint64_t m_coins_count = 0;

    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;
    }