Merge pull request #4377

654871d replace ComputeMinWork with CheckMinWork (jtimon)
b343c1a Move CBlockIndex::GetBlockWork() to pow::GetProofIncrement(nBits) (jtimon)
c2c02f3 Move UpdateTime to pow (jtimon)

7 files changed, 53 insertions, 65 deletions

diff --git a/src/main.cpp b/src/main.cpp
index c7ba15ef13..ddc37ea534 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1420,25 +1420,6 @@ void static InvalidBlockFound(CBlockIndex *pindex, const CValidationState &state
     }
 }
 
-void UpdateTime(CBlockHeader& block, const CBlockIndex* pindexPrev)
-{
-    block.nTime = max(pindexPrev->GetMedianTimePast()+1, GetAdjustedTime());
-
-    // Updating time can change work required on testnet:
-    if (Params().AllowMinDifficultyBlocks())
-        block.nBits = GetNextWorkRequired(pindexPrev, &block);
-}
-
-
-
-
-
-
-
-
-
-
-
 void UpdateCoins(const CTransaction& tx, CValidationState &state, CCoinsViewCache &inputs, CTxUndo &txundo, int nHeight)
 {
     bool ret;
@@ -2435,12 +2416,7 @@ bool AcceptBlockHeader(CBlockHeader& block, CValidationState& state, CBlockIndex
             return state.DoS(100, error("CheckBlockHeader() : block with timestamp before last checkpoint"),
                              REJECT_CHECKPOINT, "time-too-old");
         }
-        bool fOverflow = false;
-        uint256 bnNewBlock;
-        bnNewBlock.SetCompact(block.nBits, NULL, &fOverflow);
-        uint256 bnRequired;
-        bnRequired.SetCompact(ComputeMinWork(pcheckpoint->nBits, deltaTime));
-        if (fOverflow || bnNewBlock > bnRequired)
+        if (!CheckMinWork(block.nBits, pcheckpoint->nBits, deltaTime))
         {
             return state.DoS(100, error("CheckBlockHeader() : block with too little proof-of-work"),
                              REJECT_INVALID, "bad-diffbits");
@@ -3297,15 +3273,6 @@ bool LoadExternalBlockFile(FILE* fileIn, CDiskBlockPos *dbp)
     return nLoaded > 0;
 }
 
-
-
-
-
-
-
-
-
-
 //////////////////////////////////////////////////////////////////////////////
 //
 // CAlert
diff --git a/src/main.h b/src/main.h
index 142c41444e..0a1ff45460 100644
--- a/src/main.h
+++ b/src/main.h
@@ -14,6 +14,7 @@
 #include "coins.h"
 #include "core.h"
 #include "net.h"
+#include "pow.h"
 #include "script.h"
 #include "sync.h"
 #include "txmempool.h"
@@ -163,8 +164,6 @@ bool GetTransaction(const uint256 &hash, CTransaction &tx, uint256 &hashBlock, b
 bool ActivateBestChain(CValidationState &state, CBlock *pblock = NULL);
 int64_t GetBlockValue(int nHeight, int64_t nFees);
 
-void UpdateTime(CBlockHeader& block, const CBlockIndex* pindexPrev);
-
 /** Create a new block index entry for a given block hash */
 CBlockIndex * InsertBlockIndex(uint256 hash);
 /** Verify a signature */
@@ -736,17 +735,7 @@ public:
 
     uint256 GetBlockWork() const
     {
-        uint256 bnTarget;
-        bool fNegative;
-        bool fOverflow;
-        bnTarget.SetCompact(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 bnTarget+1, it is equal to ((2**256 - bnTarget - 1) / (bnTarget+1)) + 1,
-        // or ~bnTarget / (nTarget+1) + 1.
-        return (~bnTarget / (bnTarget + 1)) + 1;
+        return GetProofIncrement(nBits);
     }
 
     enum { nMedianTimeSpan=11 };
diff --git a/src/miner.cpp b/src/miner.cpp
index 8696edcf6e..96dc80a26d 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -307,7 +307,7 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
 
         // Fill in header
         pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
-        UpdateTime(*pblock, pindexPrev);
+        UpdateTime(pblock, pindexPrev);
         pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock);
         pblock->nNonce         = 0;
         pblocktemplate->vTxSigOps[0] = GetLegacySigOpCount(pblock->vtx[0]);
@@ -540,7 +540,7 @@ void static BitcoinMiner(CWallet *pwallet)
                     break;
 
                 // Update nTime every few seconds
-                UpdateTime(*pblock, pindexPrev);
+                UpdateTime(pblock, pindexPrev);
                 if (Params().AllowMinDifficultyBlocks())
                 {
                     // Changing pblock->nTime can change work required on testnet:
diff --git a/src/pow.cpp b/src/pow.cpp
index b091cbec3d..893f6c18be 100644
--- a/src/pow.cpp
+++ b/src/pow.cpp
@@ -8,6 +8,7 @@
 #include "chainparams.h"
 #include "core.h"
 #include "main.h"
+#include "timedata.h"
 #include "uint256.h"
 #include "util.h"
 
@@ -94,27 +95,58 @@ bool CheckProofOfWork(uint256 hash, unsigned int nBits)
 }
 
 //
-// minimum amount of work that could possibly be required nTime after
-// minimum work required was nBase
+// true if nBits is greater than the minimum amount of work that could
+// possibly be required deltaTime after minimum work required was nBase
 //
-unsigned int ComputeMinWork(unsigned int nBase, int64_t nTime)
+bool CheckMinWork(unsigned int nBits, unsigned int nBase, int64_t deltaTime)
 {
+    bool fOverflow = false;
+    uint256 bnNewBlock;
+    bnNewBlock.SetCompact(nBits, NULL, &fOverflow);
+    if (fOverflow)
+        return false;
+
     const uint256 &bnLimit = Params().ProofOfWorkLimit();
     // Testnet has min-difficulty blocks
     // after Params().TargetSpacing()*2 time between blocks:
-    if (Params().AllowMinDifficultyBlocks() && nTime > Params().TargetSpacing()*2)
-        return bnLimit.GetCompact();
+    if (Params().AllowMinDifficultyBlocks() && deltaTime > Params().TargetSpacing()*2)
+        return bnNewBlock <= bnLimit;
 
     uint256 bnResult;
     bnResult.SetCompact(nBase);
-    while (nTime > 0 && bnResult < bnLimit)
+    while (deltaTime > 0 && bnResult < bnLimit)
     {
         // Maximum 400% adjustment...
         bnResult *= 4;
         // ... in best-case exactly 4-times-normal target time
-        nTime -= Params().TargetTimespan()*4;
+        deltaTime -= Params().TargetTimespan()*4;
     }
     if (bnResult > bnLimit)
         bnResult = bnLimit;
-    return bnResult.GetCompact();
+
+    return bnNewBlock <= bnResult;
+}
+
+void UpdateTime(CBlockHeader* pblock, const CBlockIndex* pindexPrev)
+{
+    pblock->nTime = std::max(pindexPrev->GetMedianTimePast()+1, GetAdjustedTime());
+
+    // Updating time can change work required on testnet:
+    if (Params().AllowMinDifficultyBlocks())
+        pblock->nBits = GetNextWorkRequired(pindexPrev, pblock);
+}
+
+uint256 GetProofIncrement(unsigned int nBits)
+{
+    uint256 bnTarget;
+    bool fNegative;
+    bool fOverflow;
+    bnTarget.SetCompact(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 bnTarget+1, it is equal to ((2**256 - bnTarget - 1) / (bnTarget+1)) + 1,
+    // or ~bnTarget / (nTarget+1) + 1.
+    return (~bnTarget / (bnTarget + 1)) + 1;
 }
diff --git a/src/pow.h b/src/pow.h
index 0ce5b48766..f350d763f4 100644
--- a/src/pow.h
+++ b/src/pow.h
@@ -17,7 +17,11 @@ unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHead
 
 /** Check whether a block hash satisfies the proof-of-work requirement specified by nBits */
 bool CheckProofOfWork(uint256 hash, unsigned int nBits);
-/** Calculate the minimum amount of work a received block needs, without knowing its direct parent */
-unsigned int ComputeMinWork(unsigned int nBase, int64_t nTime);
+/** Check the work is more than the minimum a received block needs, without knowing its direct parent */
+bool CheckMinWork(unsigned int nBits, unsigned int nBase, int64_t deltaTime);
+
+void UpdateTime(CBlockHeader* block, const CBlockIndex* pindexPrev);
+
+uint256 GetProofIncrement(unsigned int nBits);
 
 #endif
diff --git a/src/rpcmining.cpp b/src/rpcmining.cpp
index 6e508abcda..e4a5bc4162 100644
--- a/src/rpcmining.cpp
+++ b/src/rpcmining.cpp
@@ -458,7 +458,7 @@ Value getblocktemplate(const Array& params, bool fHelp)
     CBlock* pblock = &pblocktemplate->block; // pointer for convenience
 
     // Update nTime
-    UpdateTime(*pblock, pindexPrev);
+    UpdateTime(pblock, pindexPrev);
     pblock->nNonce = 0;
 
     Array transactions;
diff --git a/src/test/DoS_tests.cpp b/src/test/DoS_tests.cpp
index 4ecf6e2535..8fa38c3605 100644
--- a/src/test/DoS_tests.cpp
+++ b/src/test/DoS_tests.cpp
@@ -107,11 +107,7 @@ static bool CheckNBits(unsigned int nbits1, int64_t time1, unsigned int nbits2,
         return CheckNBits(nbits2, time2, nbits1, time1);
     int64_t deltaTime = time2-time1;
 
-    uint256 required;
-    required.SetCompact(ComputeMinWork(nbits1, deltaTime));
-    uint256 have;
-    have.SetCompact(nbits2);
-    return (have <= required);
+    return CheckMinWork(nbits2, nbits1, deltaTime);
 }
 
 BOOST_AUTO_TEST_CASE(DoS_checknbits)