1 files changed, 31 insertions, 48 deletions

diff --git a/src/pow.cpp b/src/pow.cpp
index b84e4602f..b0deab393 100644
--- a/src/pow.cpp
+++ b/src/pow.cpp
@@ -1,11 +1,11 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
-// Copyright (c) 2009-2014 The Bitcoin Core developers
-// Copyright (c) 2014-2015 The Dogecoin Core developers
+// Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include "pow.h"
 
+#include "auxpow.h"
 #include "arith_uint256.h"
 #include "chain.h"
 #include "dogecoin.h"
@@ -13,6 +13,22 @@
 #include "uint256.h"
 #include "util.h"
 
+// Determine if the for the given block, a min difficulty setting applies
+bool AllowMinDifficultyForBlock(const CBlockIndex* pindexLast, const CBlockHeader *pblock, const Consensus::Params& params)
+{
+    // check if the chain allows minimum difficulty blocks
+    if (!params.fPowAllowMinDifficultyBlocks)
+        return false;
+
+    // Dogecoin: Magic number at which reset protocol switches
+    // check if we allow minimum difficulty at this block-height
+    if (pindexLast->nHeight < 157500)
+        return false;
+
+    // Allow for a minimum block time if the elapsed time > 2*nTargetSpacing
+    return (pblock->GetBlockTime() > pindexLast->GetBlockTime() + params.nPowTargetSpacing*2);
+}
+
 unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHeader *pblock, const Consensus::Params& params)
 {
     unsigned int nProofOfWorkLimit = UintToArith256(params.powLimit).GetCompact();
@@ -31,7 +47,11 @@ unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHead
     }
 
     // Only change once per difficulty adjustment interval
-    if ((pindexLast->nHeight+1) % params.DifficultyAdjustmentInterval() != 0)
+    bool fNewDifficultyProtocol = (pindexLast->nHeight >= 145000);
+    const int64_t difficultyAdjustmentInterval = fNewDifficultyProtocol
+                                                 ? 1
+                                                 : params.DifficultyAdjustmentInterval();
+    if ((pindexLast->nHeight+1) % difficultyAdjustmentInterval != 0)
     {
         if (params.fPowAllowMinDifficultyBlocks)
         {
@@ -54,9 +74,9 @@ unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHead
 
     // Litecoin: This fixes an issue where a 51% attack can change difficulty at will.
     // Go back the full period unless it's the first retarget after genesis. Code courtesy of Art Forz
-    int blockstogoback = params.DifficultyAdjustmentInterval()-1;
-    if ((pindexLast->nHeight+1) != params.DifficultyAdjustmentInterval())
-        blockstogoback = params.DifficultyAdjustmentInterval();
+    int blockstogoback = difficultyAdjustmentInterval-1;
+    if ((pindexLast->nHeight+1) != difficultyAdjustmentInterval)
+        blockstogoback = difficultyAdjustmentInterval;
 
     // Go back by what we want to be 14 days worth of blocks
     int nHeightFirst = pindexLast->nHeight - blockstogoback;
@@ -69,6 +89,9 @@ unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHead
 
 unsigned int CalculateNextWorkRequired(const CBlockIndex* pindexLast, int64_t nFirstBlockTime, const Consensus::Params& params)
 {
+    if (params.fPowNoRetargeting)
+        return pindexLast->nBits;
+
     // Limit adjustment step
     int64_t nActualTimespan = pindexLast->GetBlockTime() - nFirstBlockTime;
     if (nActualTimespan < params.nPowTargetTimespan/4)
@@ -79,21 +102,13 @@ unsigned int CalculateNextWorkRequired(const CBlockIndex* pindexLast, int64_t nF
     // Retarget
     const arith_uint256 bnPowLimit = UintToArith256(params.powLimit);
     arith_uint256 bnNew;
-    arith_uint256 bnOld;
     bnNew.SetCompact(pindexLast->nBits);
-    bnOld = bnNew;
     bnNew *= nActualTimespan;
     bnNew /= params.nPowTargetTimespan;
 
     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();
 }
 
@@ -107,43 +122,11 @@ bool CheckProofOfWork(uint256 hash, unsigned int nBits, const Consensus::Params&
 
     // Check range
     if (fNegative || bnTarget == 0 || fOverflow || bnTarget > UintToArith256(params.powLimit))
-        return error("CheckProofOfWork(): nBits below minimum work");
+        return false;
 
     // Check proof of work matches claimed amount
     if (UintToArith256(hash) > bnTarget)
-        return error("CheckProofOfWork(): hash doesn't match nBits");
+        return false;
 
     return true;
 }
-
-arith_uint256 GetBlockProof(const CBlockIndex& block)
-{
-    arith_uint256 bnTarget;
-    bool fNegative;
-    bool fOverflow;
-    bnTarget.SetCompact(block.nBits, &fNegative, &fOverflow);
-    if (fNegative || fOverflow || bnTarget == 0)
-        return 0;
-    // We need to compute 2**256 / (bnTarget+1), but we can't represent 2**256
-    // as it's too large for a arith_uint256. However, as 2**256 is at least as large
-    // as bnTarget+1, it is equal to ((2**256 - bnTarget - 1) / (bnTarget+1)) + 1,
-    // or ~bnTarget / (nTarget+1) + 1.
-    return (~bnTarget / (bnTarget + 1)) + 1;
-}
-
-int64_t GetBlockProofEquivalentTime(const CBlockIndex& to, const CBlockIndex& from, const CBlockIndex& tip, const Consensus::Params& params)
-{
-    arith_uint256 r;
-    int sign = 1;
-    if (to.nChainWork > from.nChainWork) {
-        r = to.nChainWork - from.nChainWork;
-    } else {
-        r = from.nChainWork - to.nChainWork;
-        sign = -1;
-    }
-    r = r * arith_uint256(params.nPowTargetSpacing) / GetBlockProof(tip);
-    if (r.bits() > 63) {
-        return sign * std::numeric_limits<int64_t>::max();
-    }
-    return sign * r.GetLow64();
-}