1 files changed, 54 insertions, 34 deletions

diff --git a/src/pow.cpp b/src/pow.cpp
index e91e3d893..bb53ad204 100644
--- a/src/pow.cpp
+++ b/src/pow.cpp
@@ -5,35 +5,35 @@
 
 #include "pow.h"
 
+#include "arith_uint256.h"
 #include "chain.h"
-#include "chainparams.h"
 #include "primitives/block.h"
 #include "uint256.h"
 #include "util.h"
 
-unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHeader *pblock)
+unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHeader *pblock, const Consensus::Params& params)
 {
-    unsigned int nProofOfWorkLimit = Params().ProofOfWorkLimit().GetCompact();
+    unsigned int nProofOfWorkLimit = UintToArith256(params.powLimit).GetCompact();
 
     // Genesis block
     if (pindexLast == NULL)
         return nProofOfWorkLimit;
 
-    // Only change once per interval
-    if ((pindexLast->nHeight+1) % Params().Interval() != 0)
+    // Only change once per difficulty adjustment interval
+    if ((pindexLast->nHeight+1) % params.DifficultyAdjustmentInterval() != 0)
     {
-        if (Params().AllowMinDifficultyBlocks())
+        if (params.fPowAllowMinDifficultyBlocks)
         {
             // Special difficulty rule for testnet:
             // If the new block's timestamp is more than 2* 10 minutes
             // then allow mining of a min-difficulty block.
-            if (pblock->GetBlockTime() > pindexLast->GetBlockTime() + Params().TargetSpacing()*2)
+            if (pblock->GetBlockTime() > pindexLast->GetBlockTime() + params.nPowTargetSpacing*2)
                 return nProofOfWorkLimit;
             else
             {
                 // Return the last non-special-min-difficulty-rules-block
                 const CBlockIndex* pindex = pindexLast;
-                while (pindex->pprev && pindex->nHeight % Params().Interval() != 0 && pindex->nBits == nProofOfWorkLimit)
+                while (pindex->pprev && pindex->nHeight % params.DifficultyAdjustmentInterval() != 0 && pindex->nBits == nProofOfWorkLimit)
                     pindex = pindex->pprev;
                 return pindex->nBits;
             }
@@ -42,72 +42,92 @@ unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHead
     }
 
     // Go back by what we want to be 14 days worth of blocks
-    const CBlockIndex* pindexFirst = pindexLast;
-    for (int i = 0; pindexFirst && i < Params().Interval()-1; i++)
-        pindexFirst = pindexFirst->pprev;
+    int nHeightFirst = pindexLast->nHeight - (params.DifficultyAdjustmentInterval()-1);
+    assert(nHeightFirst >= 0);
+    const CBlockIndex* pindexFirst = pindexLast->GetAncestor(nHeightFirst);
     assert(pindexFirst);
 
+    return CalculateNextWorkRequired(pindexLast, pindexFirst->GetBlockTime(), params);
+}
+
+unsigned int CalculateNextWorkRequired(const CBlockIndex* pindexLast, int64_t nFirstBlockTime, const Consensus::Params& params)
+{
     // Limit adjustment step
-    int64_t nActualTimespan = pindexLast->GetBlockTime() - pindexFirst->GetBlockTime();
+    int64_t nActualTimespan = pindexLast->GetBlockTime() - nFirstBlockTime;
     LogPrintf("  nActualTimespan = %d  before bounds\n", nActualTimespan);
-    if (nActualTimespan < Params().TargetTimespan()/4)
-        nActualTimespan = Params().TargetTimespan()/4;
-    if (nActualTimespan > Params().TargetTimespan()*4)
-        nActualTimespan = Params().TargetTimespan()*4;
+    if (nActualTimespan < params.nPowTargetTimespan/4)
+        nActualTimespan = params.nPowTargetTimespan/4;
+    if (nActualTimespan > params.nPowTargetTimespan*4)
+        nActualTimespan = params.nPowTargetTimespan*4;
 
     // Retarget
-    uint256 bnNew;
-    uint256 bnOld;
+    const arith_uint256 bnPowLimit = UintToArith256(params.powLimit);
+    arith_uint256 bnNew;
+    arith_uint256 bnOld;
     bnNew.SetCompact(pindexLast->nBits);
     bnOld = bnNew;
     bnNew *= nActualTimespan;
-    bnNew /= Params().TargetTimespan();
+    bnNew /= params.nPowTargetTimespan;
 
-    if (bnNew > Params().ProofOfWorkLimit())
-        bnNew = Params().ProofOfWorkLimit();
+    if (bnNew > bnPowLimit)
+        bnNew = bnPowLimit;
 
     /// debug print
     LogPrintf("GetNextWorkRequired RETARGET\n");
-    LogPrintf("Params().TargetTimespan() = %d    nActualTimespan = %d\n", Params().TargetTimespan(), nActualTimespan);
+    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 CheckProofOfWork(uint256 hash, unsigned int nBits)
+bool CheckProofOfWork(uint256 hash, unsigned int nBits, const Consensus::Params& params)
 {
     bool fNegative;
     bool fOverflow;
-    uint256 bnTarget;
-
-    if (Params().SkipProofOfWorkCheck())
-       return true;
+    arith_uint256 bnTarget;
 
     bnTarget.SetCompact(nBits, &fNegative, &fOverflow);
 
     // Check range
-    if (fNegative || bnTarget == 0 || fOverflow || bnTarget > Params().ProofOfWorkLimit())
-        return error("CheckProofOfWork() : nBits below minimum work");
+    if (fNegative || bnTarget == 0 || fOverflow || bnTarget > UintToArith256(params.powLimit))
+        return error("CheckProofOfWork(): nBits below minimum work");
 
     // Check proof of work matches claimed amount
-    if (hash > bnTarget)
-        return error("CheckProofOfWork() : hash doesn't match nBits");
+    if (UintToArith256(hash) > bnTarget)
+        return error("CheckProofOfWork(): hash doesn't match nBits");
 
     return true;
 }
 
-uint256 GetBlockProof(const CBlockIndex& block)
+arith_uint256 GetBlockProof(const CBlockIndex& block)
 {
-    uint256 bnTarget;
+    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 uint256. However, as 2**256 is at least as large
+    // 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();
+}