// select a block from the candidate blocks in vSortedByTimestamp, excluding
// already selected blocks in vSelectedBlocks, and with timestamp up to
// nSelectionIntervalStop.
private static bool SelectBlockFromCandidates(ChainBase chainIndex, SortedDictionary <uint, uint256> sortedByTimestamp,
Dictionary <uint256, ChainedBlock> mapSelectedBlocks,
long nSelectionIntervalStop, ulong nStakeModifierPrev, out ChainedBlock pindexSelected)
{
bool fSelected = false;
uint256 hashBest = 0;
pindexSelected = null;
foreach (var item in sortedByTimestamp)
{
var pindex = chainIndex.GetBlock(item.Value);
if (pindex == null)
{
return(false); // error("SelectBlockFromCandidates: failed to find block index for candidate block %s", item.second.ToString());
}
if (fSelected && pindex.Header.Time > nSelectionIntervalStop)
{
break;
}
if (mapSelectedBlocks.Keys.Any(key => key == pindex.HashBlock))
{
continue;
}
// compute the selection hash by hashing its proof-hash and the
// previous proof-of-stake modifier
uint256 hashSelection;
using (var ms = new MemoryStream())
{
var serializer = new BitcoinStream(ms, true);
serializer.ReadWrite(pindex.Header.PosParameters.HashProof);
serializer.ReadWrite(nStakeModifierPrev);
hashSelection = Hashes.Hash256(ms.ToArray());
}
// 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.Header.PosParameters.IsProofOfStake())
{
hashSelection >>= 32;
}
if (fSelected && hashSelection < hashBest)
{
hashBest = hashSelection;
pindexSelected = pindex;
}
else if (!fSelected)
{
fSelected = true;
hashBest = hashSelection;
pindexSelected = pindex;
}
}
//LogPrint("stakemodifier", "SelectBlockFromCandidates: selection hash=%s\n", hashBest.ToString());
return(fSelected);
}
