text: // Copyright (c) 2011-2018 The DigiByte Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include <bench/bench.h>
  #include <chainparams.h>
  #include <coins.h>
  #include <consensus/merkle.h>
  #include <consensus/validation.h>
  #include <miner.h>
  #include <policy/policy.h>
  #include <pow.h>
  #include <scheduler.h>
  #include <txdb.h>
  #include <txmempool.h>
  #include <utiltime.h>
  #include <validation.h>
  #include <validationinterface.h>
  
  #include <boost/thread.hpp>
  
  #include <list>
  #include <vector>
  
  static std::shared_ptr<CBlock> PrepareBlock(const CScript& coinbase_scriptPubKey)
  {
      auto block = std::make_shared<CBlock>(
          BlockAssembler{Params()}
              .CreateNewBlock(coinbase_scriptPubKey, /* fMineWitnessTx */ true)
              ->block);
  
      block->nTime = ::chainActive.Tip()->GetMedianTimePast() + 1;
      block->hashMerkleRoot = BlockMerkleRoot(*block);
  
      return block;
  }
  
  
  static CTxIn MineBlock(const CScript& coinbase_scriptPubKey)
  {
      auto block = PrepareBlock(coinbase_scriptPubKey);
  
      while (!CheckProofOfWork(block->GetHash(), block->nBits, Params().GetConsensus())) {
          assert(++block->nNonce);
      }
  
      bool processed{ProcessNewBlock(Params(), block, true, nullptr)};
      assert(processed);
  
      return CTxIn{block->vtx[0]->GetHash(), 0};
  }
  
  
  static void AssembleBlock(benchmark::State& state)
  {
      const std::vector<unsigned char> op_true{OP_TRUE};
      CScriptWitness witness;
      witness.stack.push_back(op_true);
  
      uint256 witness_program;
      CSHA256().Write(&op_true[0], op_true.size()).Finalize(witness_program.begin());
  
      const CScript SCRIPT_PUB{CScript(OP_0) << std::vector<unsigned char>{witness_program.begin(), witness_program.end()}};
  
      // Switch to regtest so we can mine faster
      // Also segwit is active, so we can include witness transactions
      SelectParams(CBaseChainParams::REGTEST);
  
      InitScriptExecutionCache();
  
      boost::thread_group thread_group;
      CScheduler scheduler;
      {
          ::pblocktree.reset(new CBlockTreeDB(1 << 20, true));
          ::pcoinsdbview.reset(new CCoinsViewDB(1 << 23, true));
          ::pcoinsTip.reset(new CCoinsViewCache(pcoinsdbview.get()));
  
          const CChainParams& chainparams = Params();
          thread_group.create_thread(boost::bind(&CScheduler::serviceQueue, &scheduler));
          GetMainSignals().RegisterBackgroundSignalScheduler(scheduler);
          LoadGenesisBlock(chainparams);
          CValidationState state;
          ActivateBestChain(state, chainparams);
          assert(::chainActive.Tip() != nullptr);
          const bool witness_enabled{IsWitnessEnabled(::chainActive.Tip(), chainparams.GetConsensus())};
          assert(witness_enabled);
      }
  
      // Collect some loose transactions that spend the coinbases of our mined blocks
      constexpr size_t NUM_BLOCKS{200};
      std::array<CTransactionRef, NUM_BLOCKS - COINBASE_MATURITY + 1> txs;
      for (size_t b{0}; b < NUM_BLOCKS; ++b) {
          CMutableTransaction tx;
          tx.vin.push_back(MineBlock(SCRIPT_PUB));
          tx.vin.back().scriptWitness = witness;
          tx.vout.emplace_back(1337, SCRIPT_PUB);
          if (NUM_BLOCKS - b >= COINBASE_MATURITY)
              txs.at(b) = MakeTransactionRef(tx);
      }
      {
          LOCK(::cs_main); // Required for ::AcceptToMemoryPool.
  
          for (const auto& txr : txs) {
              CValidationState state;
              bool ret{::AcceptToMemoryPool(::mempool, state, txr, nullptr /* pfMissingInputs */, nullptr /* plTxnReplaced */, false /* bypass_limits */, /* nAbsurdFee */ 0)};
              assert(ret);
          }
      }
  
      while (state.KeepRunning()) {
          PrepareBlock(SCRIPT_PUB);
      }
  
      thread_group.interrupt_all();
      thread_group.join_all();
      GetMainSignals().FlushBackgroundCallbacks();
      GetMainSignals().UnregisterBackgroundSignalScheduler();
  }
  
  BENCHMARK(AssembleBlock, 700);
  