Energi stake

energistakefunc.cpp

// select a block from the candidate blocks in vSortedByTimestamp, excluding
// already selected blocks in vSelectedBlocks, and with timestamp up to
// nSelectionIntervalStop.
static bool SelectBlockFromCandidates(
    vector<pair<int64_t, uint256> >& vSortedByTimestamp,
    map<uint256, const CBlockIndex*>& mapSelectedBlocks,
    int64_t nSelectionIntervalStop,
    uint64_t nStakeModifierPrev,
    const CBlockIndex** pindexSelected)
{
    bool fSelected = false;
    arith_uint256 hashBest{0};
    *pindexSelected = nullptr;

    for (auto iter = vSortedByTimestamp.begin(); ; ++iter) {
        if (iter == vSortedByTimestamp.end()) {
            vSortedByTimestamp.clear();
            break;
        }

        if (!mapBlockIndex.count(iter->second))
            return error("SelectBlockFromCandidates: failed to find block index for candidate block %s", iter->second.ToString().c_str());

        const CBlockIndex* pindex = mapBlockIndex[iter->second];
        if (fSelected && pindex->GetBlockTime() > nSelectionIntervalStop) {
            // No point to re-consider the blocks
            vSortedByTimestamp.erase(vSortedByTimestamp.begin(), iter+1);
            break;
        }

        if (mapSelectedBlocks.count(pindex->GetBlockHash()) > 0)
            continue;

        // compute the selection hash by hashing an input that is unique to that block
        uint256 hashProof = pindex->GetBlockHash();

        CDataStream ss(SER_GETHASH, 0);
        ss << hashProof << nStakeModifierPrev;
        arith_uint256 hashSelection = UintToArith256(Hash(ss.begin(), ss.end()));

        // the selection hash is divided by 2**32 so that proof-of-stake block
        // is always favored over proof-of-work block. this is to preserve
        // the energy efficiency property
        if (pindex->IsProofOfStake())
            hashSelection >>= 32;

        if (fSelected && hashSelection < hashBest) {
            hashBest = hashSelection;
            *pindexSelected = (const CBlockIndex*)pindex;
        } else if (!fSelected) {
            iter = vSortedByTimestamp.begin();
            fSelected = true;
            hashBest = hashSelection;
            *pindexSelected = (const CBlockIndex*)pindex;
        }
    }

    LogPrint("stake", "%s: selection hash=%s\n", __func__, hashBest.ToString().c_str());

    return fSelected;
}