text: // Copyright (c) 2015 The Bitcoin Core developers
  // Copyright (c) 2019 The PIVX developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include "consensus/merkle.h"
  #include "test/test_sovranocoin.h"
  
  #include <boost/test/unit_test.hpp>
  
  BOOST_FIXTURE_TEST_SUITE(merkle_tests, TestingSetup)
  
  // Older version of the merkle root computation code, for comparison.
  static uint256 BlockBuildMerkleTree(const CBlock& block, bool* fMutated, std::vector<uint256>& vMerkleTree)
  {
      vMerkleTree.clear();
      vMerkleTree.reserve(block.vtx.size() * 2 + 16); // Safe upper bound for the number of total nodes.
      for (std::vector<CTransaction>::const_iterator it(block.vtx.begin()); it != block.vtx.end(); ++it)
          vMerkleTree.push_back(it->GetHash());
      int j = 0;
      bool mutated = false;
      for (int nSize = block.vtx.size(); nSize > 1; nSize = (nSize + 1) / 2)
      {
          for (int i = 0; i < nSize; i += 2)
          {
              int i2 = std::min(i+1, nSize-1);
              if (i2 == i + 1 && i2 + 1 == nSize && vMerkleTree[j+i] == vMerkleTree[j+i2]) {
                  // Two identical hashes at the end of the list at a particular level.
                  mutated = true;
              }
              vMerkleTree.push_back(Hash(vMerkleTree[j+i].begin(), vMerkleTree[j+i].end(),
                                         vMerkleTree[j+i2].begin(), vMerkleTree[j+i2].end()));
          }
          j += nSize;
      }
      if (fMutated) {
          *fMutated = mutated;
      }
      return (vMerkleTree.empty() ? uint256() : vMerkleTree.back());
  }
  
  // Older version of the merkle branch computation code, for comparison.
  static std::vector<uint256> BlockGetMerkleBranch(const CBlock& block, const std::vector<uint256>& vMerkleTree, int nIndex)
  {
      std::vector<uint256> vMerkleBranch;
      int j = 0;
      for (int nSize = block.vtx.size(); nSize > 1; nSize = (nSize + 1) / 2)
      {
          int i = std::min(nIndex^1, nSize-1);
          vMerkleBranch.push_back(vMerkleTree[j+i]);
          nIndex >>= 1;
          j += nSize;
      }
      return vMerkleBranch;
  }
  
  static inline int ctz(uint32_t i) {
      if (i == 0) return 0;
      int j = 0;
      while (!(i & 1)) {
          j++;
          i >>= 1;
      }
      return j;
  }
  
  BOOST_AUTO_TEST_CASE(merkle_test)
  {
      for (int i = 0; i < 32; i++) {
          // Try 32 block sizes: all sizes from 0 to 16 inclusive, and then 15 random sizes.
          int ntx = (i <= 16) ? i : 17 + (InsecureRandRange(4000));
          // Try up to 3 mutations.
          for (int mutate = 0; mutate <= 3; mutate++) {
              int duplicate1 = mutate >= 1 ? 1 << ctz(ntx) : 0; // The last how many transactions to duplicate first.
              if (duplicate1 >= ntx) break; // Duplication of the entire tree results in a different root (it adds a level).
              int ntx1 = ntx + duplicate1; // The resulting number of transactions after the first duplication.
              int duplicate2 = mutate >= 2 ? 1 << ctz(ntx1) : 0; // Likewise for the second mutation.
              if (duplicate2 >= ntx1) break;
              int ntx2 = ntx1 + duplicate2;
              int duplicate3 = mutate >= 3 ? 1 << ctz(ntx2) : 0; // And for the the third mutation.
              if (duplicate3 >= ntx2) break;
              int ntx3 = ntx2 + duplicate3;
              // Build a block with ntx different transactions.
              CBlock block;
              block.vtx.resize(ntx);
              for (int j = 0; j < ntx; j++) {
                  CMutableTransaction mtx;
                  mtx.nLockTime = j;
                  block.vtx[j] = mtx;
              }
              // Compute the root of the block before mutating it.
              bool unmutatedMutated = false;
              uint256 unmutatedRoot = BlockMerkleRoot(block, &unmutatedMutated);
              BOOST_CHECK(unmutatedMutated == false);
              // Optionally mutate by duplicating the last transactions, resulting in the same merkle root.
              block.vtx.resize(ntx3);
              for (int j = 0; j < duplicate1; j++) {
                  block.vtx[ntx + j] = block.vtx[ntx + j - duplicate1];
              }
              for (int j = 0; j < duplicate2; j++) {
                  block.vtx[ntx1 + j] = block.vtx[ntx1 + j - duplicate2];
              }
              for (int j = 0; j < duplicate3; j++) {
                  block.vtx[ntx2 + j] = block.vtx[ntx2 + j - duplicate3];
              }
              // Compute the merkle root and merkle tree using the old mechanism.
              bool oldMutated = false;
              std::vector<uint256> merkleTree;
              uint256 oldRoot = BlockBuildMerkleTree(block, &oldMutated, merkleTree);
              // Compute the merkle root using the new mechanism.
              bool newMutated = false;
              uint256 newRoot = BlockMerkleRoot(block, &newMutated);
              BOOST_CHECK(oldRoot == newRoot);
              BOOST_CHECK(newRoot == unmutatedRoot);
              BOOST_CHECK((newRoot == uint256()) == (ntx == 0));
              BOOST_CHECK(oldMutated == newMutated);
              BOOST_CHECK(newMutated == !!mutate);
              // If no mutation was done (once for every ntx value), try up to 16 branches.
              if (mutate == 0) {
                  for (int loop = 0; loop < std::min(ntx, 16); loop++) {
                      // If ntx <= 16, try all branches. Otherise, try 16 random ones.
                      int mtx = loop;
                      if (ntx > 16) {
                          mtx = InsecureRandRange(ntx);
                      }
                      std::vector<uint256> newBranch = BlockMerkleBranch(block, mtx);
                      std::vector<uint256> oldBranch = BlockGetMerkleBranch(block, merkleTree, mtx);
                      BOOST_CHECK(oldBranch == newBranch);
                      BOOST_CHECK(ComputeMerkleRootFromBranch(block.vtx[mtx].GetHash(), newBranch, mtx) == oldRoot);
                  }
              }
          }
      }
  }
  
  BOOST_AUTO_TEST_SUITE_END()