Topic: Slimcoin | First Proof of Burn currency | Decentralized Web - page 86. (Read 137076 times)

    {
        const CBigNum bnTargetLimit = bnProofOfBurnLimit;

        if (pindexLast == NULL)
            return bnTargetLimit.GetCompact(); // genesis block

        //go backwards and find the last PoB block in the blockchain
        // once it exits, pindex is the last PoB block in the blockchain
        // and nPoW is the number of PoW blocks between pindexLast (inclusive) and the final pindex
        u32int nPoW = 0;
        const CBlockIndex *pindex = pindexLast;
        for (; pindex && !pindex->IsProofOfBurn(); pindex = pindex->pprev)
            if (pindex->IsProofOfWork())
                nPoW++;

        //if pindex is NULL, that means that there were no PoB blocks found and it got to the genesis block
        if (!pindex)
            return bnTargetLimit.GetCompact();

        //if there were no PoW blocks between, return the pindexLast's nBurnBits
        if (!nPoW)
            return pindexLast->nBurnBits;

        // slimcoin: target change every block
        // slimcoin: retarget with exponential moving toward target spacing

        //use the last PoB block's target as a seed
        CBigNum bnNew;
        bnNew.SetCompact(pindex->nBurnBits);

        //target spacing is 3 PoW blocks inbetween each PoB block
        const int64 nTargetSpacing = POB_TARGET_SPACING;
        const int64 nInterval = nPoBTargetTimespan / nTargetSpacing;

        bnNew *= ((nInterval - 1) * nTargetSpacing + nPoW + nPoW);
        bnNew /= ((nInterval + 1) * nTargetSpacing);

        //we can't make it too easy
        if (bnNew > bnTargetLimit)
            bnNew = bnTargetLimit;

        return bnNew.GetCompact();    

    }