Method ComputeNextModifier

src/stake.cpp:234–335

Stake Modifier (hash modifier of proof-of-stake): The purpose of stake modifier is to prevent a txout (coin) owner from computing future proof-of-stake generated by this txout at the time of transaction confirmation. To meet kernel protocol, the txout must hash with a future stake modifier to generate the proof. Stake modifier consists of bits each of which is contributed from a selected block of

// additional bits in the stake modifier, even after generating a chain of
// blocks.
bool Stake::ComputeNextModifier(const CBlockIndex* pindexPrev, uint64_t& nStakeModifier, bool& fGeneratedStakeModifier) {
    nStakeModifier = 0;
    fGeneratedStakeModifier = false;

    if (!pindexPrev) {
        fGeneratedStakeModifier = true;
        return true; // genesis block's modifier is 0
    }

    if (pindexPrev->nHeight == 0) {
        //Give a stake modifier to the first block
        fGeneratedStakeModifier = true;
        nStakeModifier = uint64_t("stakemodifier");
        return true;
    }

    // First find current stake modifier and its generation block time
    // if it's not old enough, return the same stake modifier
    int64_t nModifierTime = 0;
    if (!GetLastStakeModifier(pindexPrev, nStakeModifier, nModifierTime))
        return error("%s: unable to get last modifier", __func__);

#   if defined(DEBUG_DUMP_STAKING_INFO) && false
    if (GetBoolArg("-printstakemodifier", false))
        LogPrintf("%s: last modifier=%d time=%d\n", __func__, nStakeModifier, nModifierTime); // DateTimeStrFormat("%Y-%m-%d %H:%M:%S", nModifierTime)
#   endif

    auto const nPrevRounds = pindexPrev->GetBlockTime() / GetInterval();
    if (nModifierTime / GetInterval() >= nPrevRounds)
        return true;

    // Sort candidate blocks by timestamp
    vector< pair<int64_t, uint256> > vSortedCandidates;
    vSortedCandidates.reserve(64 * GetInterval() / GetTargetSpacing(pindexPrev->nHeight));

    int64_t nSelectionTime = nPrevRounds * GetInterval() - GetSelectionTime();
    const CBlockIndex* pindex = pindexPrev;
    while (pindex && pindex->GetBlockTime() >= nSelectionTime) {
        if (pindex->IsProofOfStake() && pindex->hashProofOfStake == 0) {
            return error("%s: zero stake block %s", __func__, pindex->GetBlockHash().GetHex());
        }
        vSortedCandidates.push_back(make_pair(pindex->GetBlockTime(), pindex->GetBlockHash()));
        pindex = pindex->pprev;
    }

#   if defined(DEBUG_DUMP_STAKING_INFO) && false
    int nHeightFirstCandidate = pindex ? (pindex->nHeight + 1) : 0;
#   endif

    //reverse(vSortedCandidates.begin(), vSortedCandidates.end());
    sort(vSortedCandidates.begin(), vSortedCandidates.end());

    // Select 64 blocks from candidate blocks to generate stake modifier
    uint64_t nStakeModifierNew = 0;
    map<uint256, const CBlockIndex*> mSelectedBlocks;
    for (int nRound = 0; nRound < min(64, int(vSortedCandidates.size())); nRound++) {
        // add an interval section to the current selection round
        nSelectionTime += GetSelectionInterval(nRound);