text: // Copyright (c) 2012-2016 The Babycoin 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 "memusage.h"
  #include "random.h"
  
  #include <assert.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 0; }
  
  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("Adding new coin that replaces non-pruned entry");
          }
          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) {
      bool fCoinbase = tx.IsCoinBase();
      const uint256& txid = tx.GetHash();
      for (size_t i = 0; i < tx.vout.size(); ++i) {
          bool overwrite = check ? cache.HaveCoin(COutPoint(txid, i)) : fCoinbase;
          // Always set the possible_overwrite flag to AddCoin for coinbase txn, 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) {
      hashBlock = hashBlockIn;
  }
  
  bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn) {
      for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end();) {
          if (it->second.flags & CCoinsCacheEntry::DIRTY) { // Ignore non-dirty entries (optimization).
              CCoinsMap::iterator itUs = cacheCoins.find(it->first);
              if (itUs == cacheCoins.end()) {
                  // The parent cache does not have an entry, while the child does
                  // We can ignore it if it's both FRESH and pruned in the child
                  if (!(it->second.flags & CCoinsCacheEntry::FRESH && it->second.coin.IsSpent())) {
                      // Otherwise we will need to create it in the parent
                      // and 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 {
                  // Assert that the child cache entry was not marked FRESH if the
                  // parent cache entry has unspent outputs. If this ever happens,
                  // it means the FRESH flag was misapplied and there is a logic
                  // error in the calling code.
                  if ((it->second.flags & CCoinsCacheEntry::FRESH) && !itUs->second.coin.IsSpent())
                      throw std::logic_error("FRESH flag misapplied to cache entry for base transaction with spendable outputs");
  
                  // Found the entry in the parent cache
                  if ((itUs->second.flags & CCoinsCacheEntry::FRESH) && it->second.coin.IsSpent()) {
                      // The grandparent does not have an entry, and the child is
                      // modified and being pruned. This means we can just delete
                      // it from the parent.
                      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 is possible the child has a FRESH flag here in
                      // the event the entry we found in the parent is pruned. But
                      // we must not copy that FRESH flag to the parent as that
                      // pruned state likely still needs to be communicated to the
                      // grandparent.
                  }
              }
          }
          CCoinsMap::iterator itOld = it++;
          mapCoins.erase(itOld);
      }
      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();
  }
  
  CAmount CCoinsViewCache::GetValueIn(const CTransaction& tx) const
  {
      if (tx.IsCoinBase())
          return 0;
  
      CAmount nResult = 0;
      for (unsigned int i = 0; i < tx.vin.size(); i++)
          nResult += AccessCoin(tx.vin[i].prevout).out.nValue;
  
      return nResult;
  }
  
  bool CCoinsViewCache::HaveInputs(const CTransaction& tx) const
  {
      if (!tx.IsCoinBase()) {
          for (unsigned int i = 0; i < tx.vin.size(); i++) {
              if (!HaveCoin(tx.vin[i].prevout)) {
                  return false;
              }
          }
      }
      return true;
  }
  
  static const size_t MIN_TRANSACTION_OUTPUT_WEIGHT = WITNESS_SCALE_FACTOR * ::GetSerializeSize(CTxOut(), SER_NETWORK, 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;
  }
  