text: // Copyright (c) 2012-2019 The Bitcoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include <coins.h>
  
  #include <consensus/consensus.h>
  #include <logging.h>
  #include <random.h>
  #include <version.h>
  
  bool CCoinsView::GetCoin(const COutPoint &outpoint, Coin &coin) const { return false; }
  
  uint256 CCoinsView::GetBestBlock() const { return uint256(); }
  std::vector<uint256> CCoinsView::GetHeadBlocks() const { return std::vector<uint256>(); }
  bool CCoinsView::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) { return false; }
  CCoinsViewCursor *CCoinsView::Cursor() const { return nullptr; }
  
  bool CCoinsView::HaveCoin(const COutPoint &outpoint) const
  {
      Coin coin;
      return GetCoin(outpoint, coin);
  }
  
  CCoinsViewBacked::CCoinsViewBacked(CCoinsView *viewIn) : base(viewIn) { }
  bool CCoinsViewBacked::GetCoin(const COutPoint &outpoint, Coin &coin) const { return base->GetCoin(outpoint, coin); }
  bool CCoinsViewBacked::HaveCoin(const COutPoint &outpoint) const { return base->HaveCoin(outpoint); }
  uint256 CCoinsViewBacked::GetBestBlock() const { return base->GetBestBlock(); }
  std::vector<uint256> CCoinsViewBacked::GetHeadBlocks() const { return base->GetHeadBlocks(); }
  void CCoinsViewBacked::SetBackend(CCoinsView &viewIn) { base = &viewIn; }
  bool CCoinsViewBacked::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) { return base->BatchWrite(mapCoins, hashBlock); }
  CCoinsViewCursor *CCoinsViewBacked::Cursor() const { return base->Cursor(); }
  size_t CCoinsViewBacked::EstimateSize() const { return base->EstimateSize(); }
  
  SaltedOutpointHasher::SaltedOutpointHasher() : k0(GetRand(std::numeric_limits<uint64_t>::max())), k1(GetRand(std::numeric_limits<uint64_t>::max())) {}
  
  CCoinsViewCache::CCoinsViewCache(CCoinsView *baseIn) : CCoinsViewBacked(baseIn), cachedCoinsUsage(0) { }
  
  size_t CCoinsViewCache::DynamicMemoryUsage() const {
      return memusage::DynamicUsage(cacheCoins) + cachedCoinsUsage;
  }
  
  CCoinsMap::iterator CCoinsViewCache::FetchCoin(const COutPoint &outpoint) const {
      CCoinsMap::iterator it = cacheCoins.find(outpoint);
      if (it != cacheCoins.end())
          return it;
      Coin tmp;
      if (!base->GetCoin(outpoint, tmp))
          return cacheCoins.end();
      CCoinsMap::iterator ret = cacheCoins.emplace(std::piecewise_construct, std::forward_as_tuple(outpoint), std::forward_as_tuple(std::move(tmp))).first;
      if (ret->second.coin.IsSpent()) {
          // The parent only has an empty entry for this outpoint; we can consider our
          // version as fresh.
          ret->second.flags = CCoinsCacheEntry::FRESH;
      }
      cachedCoinsUsage += ret->second.coin.DynamicMemoryUsage();
      return ret;
  }
  
  bool CCoinsViewCache::GetCoin(const COutPoint &outpoint, Coin &coin) const {
      CCoinsMap::const_iterator it = FetchCoin(outpoint);
      if (it != cacheCoins.end()) {
          coin = it->second.coin;
          return !coin.IsSpent();
      }
      return false;
  }
  
  void CCoinsViewCache::AddCoin(const COutPoint &outpoint, Coin&& coin, bool possible_overwrite) {
      assert(!coin.IsSpent());
      if (coin.out.scriptPubKey.IsUnspendable()) return;
      CCoinsMap::iterator it;
      bool inserted;
      std::tie(it, inserted) = cacheCoins.emplace(std::piecewise_construct, std::forward_as_tuple(outpoint), std::tuple<>());
      bool fresh = false;
      if (!inserted) {
          cachedCoinsUsage -= it->second.coin.DynamicMemoryUsage();
      }
      if (!possible_overwrite) {
          if (!it->second.coin.IsSpent()) {
              throw std::logic_error("Attempted to overwrite an unspent coin (when possible_overwrite is false)");
          }
          // If the coin exists in this cache as a spent coin and is DIRTY, then
          // its spentness hasn't been flushed to the parent cache. We're
          // re-adding the coin to this cache now but we can't mark it as FRESH.
          // If we mark it FRESH and then spend it before the cache is flushed
          // we would remove it from this cache and would never flush spentness
          // to the parent cache.
          //
          // Re-adding a spent coin can happen in the case of a re-org (the coin
          // is 'spent' when the block adding it is disconnected and then
          // re-added when it is also added in a newly connected block).
          //
          // If the coin doesn't exist in the current cache, or is spent but not
          // DIRTY, then it can be marked FRESH.
          fresh = !(it->second.flags & CCoinsCacheEntry::DIRTY);
      }
      it->second.coin = std::move(coin);
      it->second.flags |= CCoinsCacheEntry::DIRTY | (fresh ? CCoinsCacheEntry::FRESH : 0);
      cachedCoinsUsage += it->second.coin.DynamicMemoryUsage();
  
  }
  
  void AddCoins(CCoinsViewCache& cache, const CTransaction &tx, int nHeight, bool check_for_overwrite) {
      bool fCoinbase = tx.IsCoinBase() || tx.IsCoinStake();
      const uint256& txid = tx.GetHash();
  
      if (tx.IsParticlVersion()) {
          for (size_t i = 0; i < tx.vpout.size(); ++i) {
              const CTxOutBase *out = tx.vpout[i].get();
              bool overwrite = check_for_overwrite ? cache.HaveCoin(COutPoint(txid, i)) : fCoinbase;
              Coin coin;
              if (out->IsType(OUTPUT_STANDARD)) {
                  CTxOut txout(out->GetValue(), *out->GetPScriptPubKey());
                  coin = Coin(txout, nHeight, fCoinbase);
              } else
              if (out->IsType(OUTPUT_CT)) {
                  CAmount nV = 0;
                  CTxOut txout(nV, *out->GetPScriptPubKey());
                  coin = Coin(txout, nHeight, fCoinbase);
                  coin.nType = OUTPUT_CT;
                  coin.commitment = ((CTxOutCT*)out)->commitment;
              } else {
                  continue; // Data or anon
              }
  
              cache.AddCoin(COutPoint(txid, i), std::move(coin), overwrite);
          }
          return;
      }
  
      for (size_t i = 0; i < tx.vout.size(); ++i) {
          bool overwrite = check_for_overwrite ? cache.HaveCoin(COutPoint(txid, i)) : fCoinbase;
          // Coinbase transactions can always be overwritten, in order to correctly
          // deal with the pre-BIP30 occurrences of duplicate coinbase transactions.
          cache.AddCoin(COutPoint(txid, i), Coin(tx.vout[i], nHeight, fCoinbase), overwrite);
      }
  }
  
  bool CCoinsViewCache::SpendCoin(const COutPoint &outpoint, Coin* moveout) {
      CCoinsMap::iterator it = FetchCoin(outpoint);
      if (it == cacheCoins.end()) return false;
      cachedCoinsUsage -= it->second.coin.DynamicMemoryUsage();
      if (moveout) {
          *moveout = std::move(it->second.coin);
      }
      if (it->second.flags & CCoinsCacheEntry::FRESH) {
          cacheCoins.erase(it);
      } else {
          it->second.flags |= CCoinsCacheEntry::DIRTY;
          it->second.coin.Clear();
      }
      return true;
  }
  
  static const Coin coinEmpty;
  
  const Coin& CCoinsViewCache::AccessCoin(const COutPoint &outpoint) const {
      CCoinsMap::const_iterator it = FetchCoin(outpoint);
      if (it == cacheCoins.end()) {
          return coinEmpty;
      } else {
          return it->second.coin;
      }
  }
  
  bool CCoinsViewCache::HaveCoin(const COutPoint &outpoint) const {
      CCoinsMap::const_iterator it = FetchCoin(outpoint);
      return (it != cacheCoins.end() && !it->second.coin.IsSpent());
  }
  
  bool CCoinsViewCache::HaveCoinInCache(const COutPoint &outpoint) const {
      CCoinsMap::const_iterator it = cacheCoins.find(outpoint);
      return (it != cacheCoins.end() && !it->second.coin.IsSpent());
  }
  
  uint256 CCoinsViewCache::GetBestBlock() const {
      if (hashBlock.IsNull())
          hashBlock = base->GetBestBlock();
      return hashBlock;
  }
  
  void CCoinsViewCache::SetBestBlock(const uint256 &hashBlockIn, int height) {
      hashBlock = hashBlockIn;
      nBlockHeight = height;
  }
  
  bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn) {
      for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end(); it = mapCoins.erase(it)) {
          // Ignore non-dirty entries (optimization).
          if (!(it->second.flags & CCoinsCacheEntry::DIRTY)) {
              continue;
          }
          CCoinsMap::iterator itUs = cacheCoins.find(it->first);
          if (itUs == cacheCoins.end()) {
              // The parent cache does not have an entry, while the child cache does.
              // We can ignore it if it's both spent and FRESH in the child
              if (!(it->second.flags & CCoinsCacheEntry::FRESH && it->second.coin.IsSpent())) {
                  // Create the coin in the parent cache, move the data up
                  // and mark it as dirty.
                  CCoinsCacheEntry& entry = cacheCoins[it->first];
                  entry.coin = std::move(it->second.coin);
                  cachedCoinsUsage += entry.coin.DynamicMemoryUsage();
                  entry.flags = CCoinsCacheEntry::DIRTY;
                  // We can mark it FRESH in the parent if it was FRESH in the child
                  // Otherwise it might have just been flushed from the parent's cache
                  // and already exist in the grandparent
                  if (it->second.flags & CCoinsCacheEntry::FRESH) {
                      entry.flags |= CCoinsCacheEntry::FRESH;
                  }
              }
          } else {
              // Found the entry in the parent cache
              if ((it->second.flags & CCoinsCacheEntry::FRESH) && !itUs->second.coin.IsSpent()) {
                  // The coin was marked FRESH in the child cache, but the coin
                  // exists in the parent cache. If this ever happens, it means
                  // the FRESH flag was misapplied and there is a logic error in
                  // the calling code.
                  throw std::logic_error("FRESH flag misapplied to coin that exists in parent cache");
              }
  
              if ((itUs->second.flags & CCoinsCacheEntry::FRESH) && it->second.coin.IsSpent()) {
                  // The grandparent cache does not have an entry, and the coin
                  // has been spent. We can just delete it from the parent cache.
                  cachedCoinsUsage -= itUs->second.coin.DynamicMemoryUsage();
                  cacheCoins.erase(itUs);
              } else {
                  // A normal modification.
                  cachedCoinsUsage -= itUs->second.coin.DynamicMemoryUsage();
                  itUs->second.coin = std::move(it->second.coin);
                  cachedCoinsUsage += itUs->second.coin.DynamicMemoryUsage();
                  itUs->second.flags |= CCoinsCacheEntry::DIRTY;
                  // NOTE: It isn't safe to mark the coin as FRESH in the parent
                  // cache. If it already existed and was spent in the parent
                  // cache then marking it FRESH would prevent that spentness
                  // from being flushed to the grandparent.
              }
          }
      }
      hashBlock = hashBlockIn;
      return true;
  }
  
  bool CCoinsViewCache::Flush() {
      bool fOk = base->BatchWrite(cacheCoins, hashBlock);
      cacheCoins.clear();
      cachedCoinsUsage = 0;
      return fOk;
  }
  
  void CCoinsViewCache::Uncache(const COutPoint& hash)
  {
      CCoinsMap::iterator it = cacheCoins.find(hash);
      if (it != cacheCoins.end() && it->second.flags == 0) {
          cachedCoinsUsage -= it->second.coin.DynamicMemoryUsage();
          cacheCoins.erase(it);
      }
  }
  
  unsigned int CCoinsViewCache::GetCacheSize() const {
      return cacheCoins.size();
  }
  
  bool CCoinsViewCache::HaveInputs(const CTransaction& tx) const
  {
      if (!tx.IsCoinBase()) {
          for (unsigned int i = 0; i < tx.vin.size(); i++) {
              if (tx.vin[i].IsAnonInput()) {
                  continue;
              }
              if (!HaveCoin(tx.vin[i].prevout)) {
                  return false;
              }
          }
      }
      return true;
  }
  
  void CCoinsViewCache::ReallocateCache()
  {
      // Cache should be empty when we're calling this.
      assert(cacheCoins.size() == 0);
      cacheCoins.~CCoinsMap();
      ::new (&cacheCoins) CCoinsMap();
  }
  
  static const size_t MIN_TRANSACTION_OUTPUT_WEIGHT = WITNESS_SCALE_FACTOR * ::GetSerializeSize(CTxOut(), PROTOCOL_VERSION);
  static const size_t MAX_OUTPUTS_PER_BLOCK = MAX_BLOCK_WEIGHT / MIN_TRANSACTION_OUTPUT_WEIGHT;
  
  const Coin& AccessByTxid(const CCoinsViewCache& view, const uint256& txid)
  {
      COutPoint iter(txid, 0);
      while (iter.n < MAX_OUTPUTS_PER_BLOCK) {
          const Coin& alternate = view.AccessCoin(iter);
          if (!alternate.IsSpent()) return alternate;
          ++iter.n;
      }
      return coinEmpty;
  }
  
  bool CCoinsViewErrorCatcher::GetCoin(const COutPoint &outpoint, Coin &coin) const {
      try {
          return CCoinsViewBacked::GetCoin(outpoint, coin);
      } catch(const std::runtime_error& e) {
          for (auto f : m_err_callbacks) {
              f();
          }
          LogPrintf("Error reading from database: %s\n", e.what());
          // Starting the shutdown sequence and returning false to the caller would be
          // interpreted as 'entry not found' (as opposed to unable to read data), and
          // could lead to invalid interpretation. Just exit immediately, as we can't
          // continue anyway, and all writes should be atomic.
          std::abort();
      }
  }
  