1 files changed, 119 insertions, 1 deletions
diff --git a/src/dogecoin.cpp b/src/dogecoin.cpp
index 77a8a0093..396c4cbc4 100644
--- a/src/dogecoin.cpp
+++ b/src/dogecoin.cpp
@@ -5,7 +5,10 @@
 #include <boost/random/uniform_int.hpp>
 #include <boost/random/mersenne_twister.hpp>
 
-#include "dogecoin.h"
+#include <arith_uint256.h>
+#include <dogecoin.h>
+#include <pow.h>
+#include <util.h>
 
 int static generateMTRandom(unsigned int s, int range)
 {
@@ -14,6 +17,121 @@ int static generateMTRandom(unsigned int s, int range)
     return dist(gen);
 }
 
+// Dogecoin: Normally minimum difficulty blocks can only occur in between
+// retarget blocks. However, once we introduce Digishield every block is
+// a retarget, so we need to handle minimum difficulty on all blocks.
+bool AllowDigishieldMinDifficultyForBlock(const CBlockIndex* pindexLast, const CBlockHeader *pblock, const Consensus::Params& params)
+{
+    // check if the chain allows minimum difficulty blocks
+    if (!params.fPowAllowMinDifficultyBlocks)
+        return false;
+
+    // check if the chain allows minimum difficulty blocks on recalc blocks
+    if (pindexLast->nHeight < 157500)
+    // if (!params.fPowAllowDigishieldMinDifficultyBlocks)
+        return false;
+
+    // Allow for a minimum block time if the elapsed time > 2*nTargetSpacing
+    return (pblock->GetBlockTime() > pindexLast->GetBlockTime() + params.nPowTargetSpacing*2);
+}
+
+unsigned int CalculateDogecoinNextWorkRequired(const CBlockIndex* pindexLast, int64_t nFirstBlockTime, const Consensus::Params& params)
+{
+    int nHeight = pindexLast->nHeight + 1;
+    bool fNewDifficultyProtocol = (nHeight >= 145000);
+    // bool fNewDifficultyProtocol = (nHeight >= params.GetDigiShieldForkBlock());
+    const int64_t retargetTimespan = fNewDifficultyProtocol ? 60 // params.DigiShieldTargetTimespan()
+                                                              :
+                                                              params.nPowTargetTimespan;
+
+    const int64_t nActualTimespan = pindexLast->GetBlockTime() - nFirstBlockTime;
+    int64_t nModulatedTimespan = nActualTimespan;
+    int64_t nMaxTimespan;
+    int64_t nMinTimespan;
+
+    if (fNewDifficultyProtocol) //DigiShield implementation - thanks to RealSolid & WDC for this code
+    {
+        // amplitude filter - thanks to daft27 for this code
+        nModulatedTimespan = retargetTimespan + (nModulatedTimespan - retargetTimespan) / 8;
+
+        nMinTimespan = retargetTimespan - (retargetTimespan / 4);
+        nMaxTimespan = retargetTimespan + (retargetTimespan / 2);
+    } else if (nHeight > 10000) {
+        nMinTimespan = retargetTimespan / 4;
+        nMaxTimespan = retargetTimespan * 4;
+    } else if (nHeight > 5000) {
+        nMinTimespan = retargetTimespan / 8;
+        nMaxTimespan = retargetTimespan * 4;
+    } else {
+        nMinTimespan = retargetTimespan / 16;
+        nMaxTimespan = retargetTimespan * 4;
+    }
+
+    // Limit adjustment step
+    if (nModulatedTimespan < nMinTimespan)
+        nModulatedTimespan = nMinTimespan;
+    else if (nModulatedTimespan > nMaxTimespan)
+        nModulatedTimespan = nMaxTimespan;
+
+    // Retarget
+    const arith_uint256 bnPowLimit = UintToArith256(params.powLimit);
+    arith_uint256 bnNew;
+    arith_uint256 bnOld;
+    bnNew.SetCompact(pindexLast->nBits);
+    bnOld = bnNew;
+    bnNew *= nModulatedTimespan;
+    bnNew /= retargetTimespan;
+
+    if (bnNew > bnPowLimit)
+        bnNew = bnPowLimit;
+
+    /// debug print
+    LogPrintf("GetNextWorkRequired RETARGET\n");
+    LogPrintf("params.nPowTargetTimespan = %d    nActualTimespan = %d\n", params.nPowTargetTimespan, nActualTimespan);
+    LogPrintf("Before: %08x  %s\n", pindexLast->nBits, bnOld.ToString());
+    LogPrintf("After:  %08x  %s\n", bnNew.GetCompact(), bnNew.ToString());
+
+    return bnNew.GetCompact();
+}
+
+bool CheckAuxPowProofOfWork(const CBlockHeader& block, const Consensus::Params& params)
+{
+    /* Except for legacy blocks with full version 1, ensure that
+       the chain ID is correct.  Legacy blocks are not allowed since
+       the merge-mining start, which is checked in AcceptBlockHeader
+       where the height is known.  */
+    if (!block.IsLegacy() && params.fStrictChainId
+        && block.GetChainId() != params.nAuxpowChainId)
+        return error("%s : block does not have our chain ID"
+                     " (got %d, expected %d, full nVersion %d)",
+                     __func__, block.GetChainId(),
+                     params.nAuxpowChainId, block.nVersion);
+
+    /* If there is no auxpow, just check the block hash.  */
+    if (!block.auxpow) {
+        if (block.IsAuxpow())
+            return error("%s : no auxpow on block with auxpow version",
+                         __func__);
+
+        if (!CheckProofOfWork(block.GetPoWHash(), block.nBits, params))
+            return error("%s : non-AUX proof of work failed", __func__);
+
+        return true;
+    }
+
+    /* We have auxpow.  Check it.  */
+
+    if (!block.IsAuxpow())
+        return error("%s : auxpow on block with non-auxpow version", __func__);
+
+    if (!block.auxpow->check(block.GetHash(), block.GetChainId(), params))
+        return error("%s : AUX POW is not valid", __func__);
+    if (!CheckProofOfWork(block.auxpow->getParentBlockPoWHash(), block.nBits, params))
+        return error("%s : AUX proof of work failed", __func__);
+
+    return true;
+}
+
 CAmount GetDogecoinBlockSubsidy(int nHeight, const Consensus::Params& consensusParams, uint256 prevHash)
 {
     int halvings = nHeight / consensusParams.nSubsidyHalvingInterval;