Revert mining changes in #5957

This reverts commit e2edf95cd3f43331843676e49a82830128a95050 6b04508e37c5dd18cec1cd61cc4356bd208aa991 0df67f1f7ab4adfe9f0b3ba6276e737b37826464,
except the changes to the RPC tests.

A `generate` RPC call is introduced based on the old code.

4 files changed, 97 insertions, 91 deletions

diff --git a/src/miner.cpp b/src/miner.cpp
index 7f01918eef..cf08b78229 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -87,7 +87,7 @@ void UpdateTime(CBlockHeader* pblock, const CBlockIndex* pindexPrev)
         pblock->nBits = GetNextWorkRequired(pindexPrev, pblock, Params().GetConsensus());
 }
 
-CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn, CBlockIndex*& pindexPrev)
+CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
 {
     // Create new block
     auto_ptr<CBlockTemplate> pblocktemplate(new CBlockTemplate());
@@ -132,7 +132,7 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn, CBlockIndex*& pind
 
     {
         LOCK2(cs_main, mempool.cs);
-        pindexPrev = chainActive.Tip();
+        CBlockIndex* pindexPrev = chainActive.Tip();
         const int nHeight = pindexPrev->nHeight + 1;
         CCoinsViewCache view(pcoinsTip);
 
@@ -365,34 +365,45 @@ void IncrementExtraNonce(CBlock* pblock, CBlockIndex* pindexPrev, unsigned int&
 
 //
 // ScanHash scans nonces looking for a hash with at least some zero bits.
-// The nonce is usually preserved between calls, but periodically the block is
-// rebuilt and nNonce starts over at zero.
+// The nonce is usually preserved between calls, but periodically or if the
+// nonce is 0xffff0000 or above, the block is rebuilt and nNonce starts over at
+// zero.
 //
-bool static ScanHash(CBlockHeader *pblock, uint256 *phash)
+bool static ScanHash(const CBlockHeader *pblock, uint32_t& nNonce, uint256 *phash)
 {
+    // Write the first 76 bytes of the block header to a double-SHA256 state.
+    CHash256 hasher;
+    CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
+    ss << *pblock;
+    assert(ss.size() == 80);
+    hasher.Write((unsigned char*)&ss[0], 76);
+
     while (true) {
-        pblock->nNonce++;
-        *phash = pblock->GetHash();
+        nNonce++;
+
+        // Write the last 4 bytes of the block header (the nonce) to a copy of
+        // the double-SHA256 state, and compute the result.
+        CHash256(hasher).Write((unsigned char*)&nNonce, 4).Finalize((unsigned char*)phash);
 
         // Return the nonce if the hash has at least some zero bits,
         // caller will check if it has enough to reach the target
         if (((uint16_t*)phash)[15] == 0)
             return true;
 
-        // If nothing found after trying for a while, return false.
-        if ((pblock->nNonce & 0xfff) == 0)
+        // If nothing found after trying for a while, return -1
+        if ((nNonce & 0xfff) == 0)
             return false;
     }
 }
 
-CBlockTemplate* CreateNewBlockWithKey(CReserveKey& reservekey, CBlockIndex*& pindexPrev)
+CBlockTemplate* CreateNewBlockWithKey(CReserveKey& reservekey)
 {
     CPubKey pubkey;
     if (!reservekey.GetReservedKey(pubkey))
         return NULL;
 
     CScript scriptPubKey = CScript() << ToByteVector(pubkey) << OP_CHECKSIG;
-    return CreateNewBlock(scriptPubKey, pindexPrev);
+    return CreateNewBlock(scriptPubKey);
 }
 
 static bool ProcessBlockFound(CBlock* pblock, CWallet& wallet, CReserveKey& reservekey)
@@ -424,56 +435,6 @@ static bool ProcessBlockFound(CBlock* pblock, CWallet& wallet, CReserveKey& rese
     return true;
 }
 
-bool static ScanLoop(CBlock *pblock, CBlockIndex *pindexPrev, CWallet *pwallet, CReserveKey& reservekey)
-{
-    UpdateTime(pblock, pindexPrev);
-    arith_uint256 hashTarget = arith_uint256().SetCompact(pblock->nBits);
-
-    uint256 hash;
-    if (ScanHash(pblock, &hash)) {
-        if (UintToArith256(hash) <= hashTarget) {
-            // Found a solution
-            SetThreadPriority(THREAD_PRIORITY_NORMAL);
-            LogPrintf("BitcoinMiner:\n");
-            LogPrintf("proof-of-work found  \n  hash: %s  \ntarget: %s\n", hash.GetHex(), hashTarget.GetHex());
-            ProcessBlockFound(pblock, *pwallet, reservekey);
-            SetThreadPriority(THREAD_PRIORITY_LOWEST);
-
-            return true;
-        }
-    }
-
-    return false;
-}
-
-bool MineBlock(CWallet *pwallet, uint256& hash)
-{
-    CReserveKey reservekey(pwallet);
-    unsigned int nExtraNonce = 0;
-
-    while (true) {
-        CBlockIndex *pindexPrev;
-
-        auto_ptr<CBlockTemplate> pblocktemplate(CreateNewBlockWithKey(reservekey, pindexPrev));
-        if (!pblocktemplate.get()) {
-            return false;
-        }
-
-        CBlock *pblock = &pblocktemplate->block;
-        IncrementExtraNonce(pblock, pindexPrev, nExtraNonce);
-
-        while (true) {
-            if (ScanLoop(pblock, pindexPrev, pwallet, reservekey)) {
-                hash = pblock->GetHash();
-                return true;
-            }
-            boost::this_thread::interruption_point();
-            if (pblock->nNonce >= 0xffff0000)
-                break;
-        }
-    }
-}
-
 void static BitcoinMiner(CWallet *pwallet)
 {
     LogPrintf("BitcoinMiner started\n");
@@ -497,9 +458,9 @@ void static BitcoinMiner(CWallet *pwallet)
             // Create new block
             //
             unsigned int nTransactionsUpdatedLast = mempool.GetTransactionsUpdated();
-            CBlockIndex* pindexPrev;
+            CBlockIndex* pindexPrev = chainActive.Tip();
 
-            auto_ptr<CBlockTemplate> pblocktemplate(CreateNewBlockWithKey(reservekey, pindexPrev));
+            auto_ptr<CBlockTemplate> pblocktemplate(CreateNewBlockWithKey(reservekey));
             if (!pblocktemplate.get())
             {
                 LogPrintf("Error in BitcoinMiner: Keypool ran out, please call keypoolrefill before restarting the mining thread\n");
@@ -515,23 +476,52 @@ void static BitcoinMiner(CWallet *pwallet)
             // Search
             //
             int64_t nStart = GetTime();
+            arith_uint256 hashTarget = arith_uint256().SetCompact(pblock->nBits);
+            uint256 hash;
+            uint32_t nNonce = 0;
             while (true) {
                 // Check if something found
-                if (ScanLoop(pblock, pindexPrev, pwallet, reservekey))
-                    break;
+                if (ScanHash(pblock, nNonce, &hash))
+                {
+                    if (UintToArith256(hash) <= hashTarget)
+                    {
+                        // Found a solution
+                        pblock->nNonce = nNonce;
+                        assert(hash == pblock->GetHash());
+
+                        SetThreadPriority(THREAD_PRIORITY_NORMAL);
+                        LogPrintf("BitcoinMiner:\n");
+                        LogPrintf("proof-of-work found  \n  hash: %s  \ntarget: %s\n", hash.GetHex(), hashTarget.GetHex());
+                        ProcessBlockFound(pblock, *pwallet, reservekey);
+                        SetThreadPriority(THREAD_PRIORITY_LOWEST);
+
+                        // In regression test mode, stop mining after a block is found.
+                        if (Params().MineBlocksOnDemand())
+                            throw boost::thread_interrupted();
+
+                        break;
+                    }
+                }
 
                 // Check for stop or if block needs to be rebuilt
                 boost::this_thread::interruption_point();
                 // Regtest mode doesn't require peers
                 if (vNodes.empty() && Params().MiningRequiresPeers())
                     break;
-                if (pblock->nNonce >= 0xffff0000)
+                if (nNonce >= 0xffff0000)
                     break;
                 if (mempool.GetTransactionsUpdated() != nTransactionsUpdatedLast && GetTime() - nStart > 60)
                     break;
                 if (pindexPrev != chainActive.Tip())
                     break;
 
+                // Update nTime every few seconds
+                UpdateTime(pblock, pindexPrev);
+                if (Params().AllowMinDifficultyBlocks())
+                {
+                    // Changing pblock->nTime can change work required on testnet:
+                    hashTarget.SetCompact(pblock->nBits);
+                }
             }
         }
     }
diff --git a/src/miner.h b/src/miner.h
index 00ad299512..5d5c9c86c7 100644
--- a/src/miner.h
+++ b/src/miner.h
@@ -24,11 +24,9 @@ struct CBlockTemplate
 
 /** Run the miner threads */
 void GenerateBitcoins(bool fGenerate, CWallet* pwallet, int nThreads);
-/** Create a single block */
-bool MineBlock(CWallet *pwallet, uint256& hash);
 /** Generate a new block, without valid proof-of-work */
-CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn, CBlockIndex*& pindexPrev);
-CBlockTemplate* CreateNewBlockWithKey(CReserveKey& reservekey, CBlockIndex*& pindexPrev);
+CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn);
+CBlockTemplate* CreateNewBlockWithKey(CReserveKey& reservekey);
 /** Modify the extranonce in a block */
 void IncrementExtraNonce(CBlock* pblock, CBlockIndex* pindexPrev, unsigned int& nExtraNonce);
 void UpdateTime(CBlockHeader* block, const CBlockIndex* pindexPrev);
diff --git a/src/rpcmining.cpp b/src/rpcmining.cpp
index 6f165028d5..1e6531f68a 100644
--- a/src/rpcmining.cpp
+++ b/src/rpcmining.cpp
@@ -119,6 +119,7 @@ Value generate(const Array& params, bool fHelp)
         throw runtime_error(
             "generate numblocks\n"
             "\nMine blocks immediately (before the RPC call returns)\n"
+            "\nNote: this function can only be used on the regtest network\n"
             "1. numblocks    (numeric) How many blocks are generated immediately.\n"
             "\nResult\n"
             "[ blockhashes ]     (array) hashes of blocks generated\n"
@@ -129,11 +130,14 @@ Value generate(const Array& params, bool fHelp)
 
     if (pwalletMain == NULL)
         throw JSONRPCError(RPC_METHOD_NOT_FOUND, "Method not found (disabled)");
+    if (!Params().MineBlocksOnDemand())
+        throw JSONRPCError(RPC_METHOD_NOT_FOUND, "This method can only be used on regtest");
 
     int nHeightStart = 0;
     int nHeightEnd = 0;
     int nHeight = 0;
     int nGenerate = params[0].get_int();
+    CReserveKey reservekey(pwalletMain);
 
     {   // Don't keep cs_main locked
         LOCK(cs_main);
@@ -141,18 +145,33 @@ Value generate(const Array& params, bool fHelp)
         nHeight = nHeightStart;
         nHeightEnd = nHeightStart+nGenerate;
     }
+    unsigned int nExtraNonce = 0;
     Array blockHashes;
-    while (nHeight < nHeightEnd) {
-        uint256 hash;
-        if (!MineBlock(pwalletMain, hash))
+    while (nHeight < nHeightEnd)
+    {
+        auto_ptr<CBlockTemplate> pblocktemplate(CreateNewBlockWithKey(reservekey));
+        if (!pblocktemplate.get())
             throw JSONRPCError(RPC_INTERNAL_ERROR, "Wallet keypool empty");
-
+        CBlock *pblock = &pblocktemplate->block;
+        {
+            LOCK(cs_main);
+            IncrementExtraNonce(pblock, chainActive.Tip(), nExtraNonce);
+        }
+        while (!CheckProofOfWork(pblock->GetHash(), pblock->nBits, Params().GetConsensus())) {
+            // Yes, there is a chance every nonce could fail to satisfy the -regtest
+            // target -- 1 in 2^(2^32). That ain't gonna happen.
+            ++pblock->nNonce;
+        }
+        CValidationState state;
+        if (!ProcessNewBlock(state, NULL, pblock))
+            throw JSONRPCError(RPC_INTERNAL_ERROR, "ProcessNewBlock, block not accepted");
         ++nHeight;
-        blockHashes.push_back(hash.GetHex());
+        blockHashes.push_back(pblock->GetHash().GetHex());
     }
     return blockHashes;
 }
 
+
 Value setgenerate(const Array& params, bool fHelp)
 {
     if (fHelp || params.size() < 1 || params.size() > 2)
@@ -475,7 +494,7 @@ Value getblocktemplate(const Array& params, bool fHelp)
 
         // Store the pindexBest used before CreateNewBlock, to avoid races
         nTransactionsUpdatedLast = mempool.GetTransactionsUpdated();
-        CBlockIndex* pindexPrevNew;
+        CBlockIndex* pindexPrevNew = chainActive.Tip();
         nStart = GetTime();
 
         // Create new block
@@ -485,7 +504,7 @@ Value getblocktemplate(const Array& params, bool fHelp)
             pblocktemplate = NULL;
         }
         CScript scriptDummy = CScript() << OP_TRUE;
-        pblocktemplate = CreateNewBlock(scriptDummy, pindexPrevNew);
+        pblocktemplate = CreateNewBlock(scriptDummy);
         if (!pblocktemplate)
             throw JSONRPCError(RPC_OUT_OF_MEMORY, "Out of memory");
 
diff --git a/src/test/miner_tests.cpp b/src/test/miner_tests.cpp
index 27c0a08de9..6ab9cb8a44 100644
--- a/src/test/miner_tests.cpp
+++ b/src/test/miner_tests.cpp
@@ -62,8 +62,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     Checkpoints::fEnabled = false;
 
     // Simple block creation, nothing special yet:
-    CBlockIndex* pindexPrev;
-    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey, pindexPrev));
+    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey));
 
     // We can't make transactions until we have inputs
     // Therefore, load 100 blocks :)
@@ -91,7 +90,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     delete pblocktemplate;
 
     // Just to make sure we can still make simple blocks
-    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey, pindexPrev));
+    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey));
     delete pblocktemplate;
 
     // block sigops > limit: 1000 CHECKMULTISIG + 1
@@ -109,7 +108,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
         mempool.addUnchecked(hash, CTxMemPoolEntry(tx, 11, GetTime(), 111.0, 11));
         tx.vin[0].prevout.hash = hash;
     }
-    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey, pindexPrev));
+    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey));
     delete pblocktemplate;
     mempool.clear();
 
@@ -129,14 +128,14 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
         mempool.addUnchecked(hash, CTxMemPoolEntry(tx, 11, GetTime(), 111.0, 11));
         tx.vin[0].prevout.hash = hash;
     }
-    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey, pindexPrev));
+    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey));
     delete pblocktemplate;
     mempool.clear();
 
     // orphan in mempool
     hash = tx.GetHash();
     mempool.addUnchecked(hash, CTxMemPoolEntry(tx, 11, GetTime(), 111.0, 11));
-    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey, pindexPrev));
+    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey));
     delete pblocktemplate;
     mempool.clear();
 
@@ -154,7 +153,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     tx.vout[0].nValue = 5900000000LL;
     hash = tx.GetHash();
     mempool.addUnchecked(hash, CTxMemPoolEntry(tx, 11, GetTime(), 111.0, 11));
-    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey, pindexPrev));
+    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey));
     delete pblocktemplate;
     mempool.clear();
 
@@ -165,7 +164,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     tx.vout[0].nValue = 0;
     hash = tx.GetHash();
     mempool.addUnchecked(hash, CTxMemPoolEntry(tx, 11, GetTime(), 111.0, 11));
-    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey, pindexPrev));
+    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey));
     delete pblocktemplate;
     mempool.clear();
 
@@ -183,7 +182,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     tx.vout[0].nValue -= 1000000;
     hash = tx.GetHash();
     mempool.addUnchecked(hash, CTxMemPoolEntry(tx, 11, GetTime(), 111.0, 11));
-    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey, pindexPrev));
+    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey));
     delete pblocktemplate;
     mempool.clear();
 
@@ -197,17 +196,17 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     tx.vout[0].scriptPubKey = CScript() << OP_2;
     hash = tx.GetHash();
     mempool.addUnchecked(hash, CTxMemPoolEntry(tx, 11, GetTime(), 111.0, 11));
-    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey, pindexPrev));
+    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey));
     delete pblocktemplate;
     mempool.clear();
 
     // subsidy changing
     int nHeight = chainActive.Height();
     chainActive.Tip()->nHeight = 209999;
-    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey, pindexPrev));
+    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey));
     delete pblocktemplate;
     chainActive.Tip()->nHeight = 210000;
-    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey, pindexPrev));
+    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey));
     delete pblocktemplate;
     chainActive.Tip()->nHeight = nHeight;
 
@@ -239,7 +238,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     mempool.addUnchecked(hash, CTxMemPoolEntry(tx2, 11, GetTime(), 111.0, 11));
     BOOST_CHECK(!IsFinalTx(tx2));
 
-    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey, pindexPrev));
+    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey));
 
     // Neither tx should have make it into the template.
     BOOST_CHECK_EQUAL(pblocktemplate->block.vtx.size(), 1);
@@ -252,7 +251,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     BOOST_CHECK(IsFinalTx(tx, chainActive.Tip()->nHeight + 1));
     BOOST_CHECK(IsFinalTx(tx2));
 
-    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey, pindexPrev));
+    BOOST_CHECK(pblocktemplate = CreateNewBlock(scriptPubKey));
     BOOST_CHECK_EQUAL(pblocktemplate->block.vtx.size(), 3);
     delete pblocktemplate;