text: // Copyright (c) 2014 The Bitcoin Core developers
  // Copyright (c) 2017 The PIVX developers
  // Copyright (c) 2018 The socialcoin developers
  // Distributed under the MIT/X11 software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include "main.h"
  #include "random.h"
  #include "util.h"
  
  #include <vector>
  
  #include <boost/test/unit_test.hpp>
  
  #define SKIPLIST_LENGTH 300000
  
  BOOST_AUTO_TEST_SUITE(skiplist_tests)
  
  BOOST_AUTO_TEST_CASE(skiplist_test)
  {
      std::vector<CBlockIndex> vIndex(SKIPLIST_LENGTH);
  
      for (int i=0; i<SKIPLIST_LENGTH; i++) {
          vIndex[i].nHeight = i;
          vIndex[i].pprev = (i == 0) ? NULL : &vIndex[i - 1];
          vIndex[i].BuildSkip();
      }
  
      for (int i=0; i<SKIPLIST_LENGTH; i++) {
          if (i > 0) {
              BOOST_CHECK(vIndex[i].pskip == &vIndex[vIndex[i].pskip->nHeight]);
              BOOST_CHECK(vIndex[i].pskip->nHeight < i);
          } else {
              BOOST_CHECK(vIndex[i].pskip == NULL);
          }
      }
  
      for (int i=0; i < 1000; i++) {
          int from = insecure_rand() % (SKIPLIST_LENGTH - 1);
          int to = insecure_rand() % (from + 1);
  
          BOOST_CHECK(vIndex[SKIPLIST_LENGTH - 1].GetAncestor(from) == &vIndex[from]);
          BOOST_CHECK(vIndex[from].GetAncestor(to) == &vIndex[to]);
          BOOST_CHECK(vIndex[from].GetAncestor(0) == &vIndex[0]);
      }
  }
  
  BOOST_AUTO_TEST_CASE(getlocator_test)
  {
      // Build a main chain 100000 blocks long.
      std::vector<uint256> vHashMain(100000);
      std::vector<CBlockIndex> vBlocksMain(100000);
      for (unsigned int i=0; i<vBlocksMain.size(); i++) {
          vHashMain[i] = i; // Set the hash equal to the height, so we can quickly check the distances.
          vBlocksMain[i].nHeight = i;
          vBlocksMain[i].pprev = i ? &vBlocksMain[i - 1] : NULL;
          vBlocksMain[i].phashBlock = &vHashMain[i];
          vBlocksMain[i].BuildSkip();
          BOOST_CHECK_EQUAL((int)vBlocksMain[i].GetBlockHash().GetLow64(), vBlocksMain[i].nHeight);
          BOOST_CHECK(vBlocksMain[i].pprev == NULL || vBlocksMain[i].nHeight == vBlocksMain[i].pprev->nHeight + 1);
      }
  
      // Build a branch that splits off at block 49999, 50000 blocks long.
      std::vector<uint256> vHashSide(50000);
      std::vector<CBlockIndex> vBlocksSide(50000);
      for (unsigned int i=0; i<vBlocksSide.size(); i++) {
          vHashSide[i] = i + 50000 + (uint256(1) << 128); // Add 1<<128 to the hashes, so GetLow64() still returns the height.
          vBlocksSide[i].nHeight = i + 50000;
          vBlocksSide[i].pprev = i ? &vBlocksSide[i - 1] : &vBlocksMain[49999];
          vBlocksSide[i].phashBlock = &vHashSide[i];
          vBlocksSide[i].BuildSkip();
          BOOST_CHECK_EQUAL((int)vBlocksSide[i].GetBlockHash().GetLow64(), vBlocksSide[i].nHeight);
          BOOST_CHECK(vBlocksSide[i].pprev == NULL || vBlocksSide[i].nHeight == vBlocksSide[i].pprev->nHeight + 1);
      }
  
      // Build a CChain for the main branch.
      CChain chain;
      chain.SetTip(&vBlocksMain.back());
  
      // Test 100 random starting points for locators.
      for (int n=0; n<100; n++) {
          int r = insecure_rand() % 150000;
          CBlockIndex* tip = (r < 100000) ? &vBlocksMain[r] : &vBlocksSide[r - 100000];
          CBlockLocator locator = chain.GetLocator(tip);
  
          // The first result must be the block itself, the last one must be genesis.
          BOOST_CHECK(locator.vHave.front() == tip->GetBlockHash());
          BOOST_CHECK(locator.vHave.back() == vBlocksMain[0].GetBlockHash());
  
          // Entries 1 through 11 (inclusive) go back one step each.
          for (unsigned int i = 1; i < 12 && i < locator.vHave.size() - 1; i++) {
              BOOST_CHECK_EQUAL(locator.vHave[i].GetLow64(), tip->nHeight - i);
          }
  
          // The further ones (excluding the last one) go back with exponential steps.
          unsigned int dist = 2;
          for (unsigned int i = 12; i < locator.vHave.size() - 1; i++) {
              BOOST_CHECK_EQUAL(locator.vHave[i - 1].GetLow64() - locator.vHave[i].GetLow64(), dist);
              dist *= 2;
          }
      }
  }
  
  BOOST_AUTO_TEST_SUITE_END()
  