text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2013 The Bitcoin developers
  // Distributed under the MIT/X11 software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  #ifndef BITCOIN_COINS_H
  #define BITCOIN_COINS_H
  
  #include "core.h"
  #include "serialize.h"
  #include "uint256.h"
  
  #include <assert.h>
  #include <stdint.h>
  
  #include <boost/foreach.hpp>
  
  /** pruned version of CTransaction: only retains metadata and unspent transaction outputs
   *
   * Serialized format:
   * - VARINT(nVersion)
   * - VARINT(nCode)
   * - unspentness bitvector, for vout[2] and further; least significant byte first
   * - the non-spent CTxOuts (via CTxOutCompressor)
   * - VARINT(nHeight)
   *
   * The nCode value consists of:
   * - bit 1: IsCoinBase()
   * - bit 2: vout[0] is not spent
   * - bit 4: vout[1] is not spent
   * - The higher bits encode N, the number of non-zero bytes in the following bitvector.
   *   - In case both bit 2 and bit 4 are unset, they encode N-1, as there must be at
   *     least one non-spent output).
   *
   * Example: 0104835800816115944e077fe7c803cfa57f29b36bf87c1d358bb85e
   *          <><><--------------------------------------------><---->
   *          |  \                  |                             /
   *    version   code             vout[1]                  height
   *
   *    - version = 1
   *    - code = 4 (vout[1] is not spent, and 0 non-zero bytes of bitvector follow)
   *    - unspentness bitvector: as 0 non-zero bytes follow, it has length 0
   *    - vout[1]: 835800816115944e077fe7c803cfa57f29b36bf87c1d35
   *               * 8358: compact amount representation for 60000000000 (600 BTC)
   *               * 00: special txout type pay-to-pubkey-hash
   *               * 816115944e077fe7c803cfa57f29b36bf87c1d35: address uint160
   *    - height = 203998
   *
   *
   * Example: 0109044086ef97d5790061b01caab50f1b8e9c50a5057eb43c2d9563a4eebbd123008c988f1a4a4de2161e0f50aac7f17e7f9555caa486af3b
   *          <><><--><--------------------------------------------------><----------------------------------------------><---->
   *         /  \   \                     |                                                           |                     /
   *  version  code  unspentness       vout[4]                                                     vout[16]           height
   *
   *  - version = 1
   *  - code = 9 (coinbase, neither vout[0] or vout[1] are unspent,
   *                2 (1, +1 because both bit 2 and bit 4 are unset) non-zero bitvector bytes follow)
   *  - unspentness bitvector: bits 2 (0x04) and 14 (0x4000) are set, so vout[2+2] and vout[14+2] are unspent
   *  - vout[4]: 86ef97d5790061b01caab50f1b8e9c50a5057eb43c2d9563a4ee
   *             * 86ef97d579: compact amount representation for 234925952 (2.35 BTC)
   *             * 00: special txout type pay-to-pubkey-hash
   *             * 61b01caab50f1b8e9c50a5057eb43c2d9563a4ee: address uint160
   *  - vout[16]: bbd123008c988f1a4a4de2161e0f50aac7f17e7f9555caa4
   *              * bbd123: compact amount representation for 110397 (0.001 BTC)
   *              * 00: special txout type pay-to-pubkey-hash
   *              * 8c988f1a4a4de2161e0f50aac7f17e7f9555caa4: address uint160
   *  - height = 120891
   */
  class CCoins
  {
  public:
      // whether transaction is a coinbase
      bool fCoinBase;
  
      // unspent transaction outputs; spent outputs are .IsNull(); spent outputs at the end of the array are dropped
      std::vector<CTxOut> vout;
  
      // at which height this transaction was included in the active block chain
      int nHeight;
  
      // version of the CTransaction; accesses to this value should probably check for nHeight as well,
      // as new tx version will probably only be introduced at certain heights
      int nVersion;
  
      // construct a CCoins from a CTransaction, at a given height
      CCoins(const CTransaction &tx, int nHeightIn) : fCoinBase(tx.IsCoinBase()), vout(tx.vout), nHeight(nHeightIn), nVersion(tx.nVersion) {
          ClearUnspendable();
      }
  
      // empty constructor
      CCoins() : fCoinBase(false), vout(0), nHeight(0), nVersion(0) { }
  
      // remove spent outputs at the end of vout
      void Cleanup() {
          while (vout.size() > 0 && vout.back().IsNull())
              vout.pop_back();
          if (vout.empty())
              std::vector<CTxOut>().swap(vout);
      }
  
      void ClearUnspendable() {
          BOOST_FOREACH(CTxOut &txout, vout) {
              if (txout.scriptPubKey.IsUnspendable())
                  txout.SetNull();
          }
          Cleanup();
      }
  
      void swap(CCoins &to) {
          std::swap(to.fCoinBase, fCoinBase);
          to.vout.swap(vout);
          std::swap(to.nHeight, nHeight);
          std::swap(to.nVersion, nVersion);
      }
  
      // equality test
      friend bool operator==(const CCoins &a, const CCoins &b) {
           // Empty CCoins objects are always equal.
           if (a.IsPruned() && b.IsPruned())
               return true;
           return a.fCoinBase == b.fCoinBase &&
                  a.nHeight == b.nHeight &&
                  a.nVersion == b.nVersion &&
                  a.vout == b.vout;
      }
      friend bool operator!=(const CCoins &a, const CCoins &b) {
          return !(a == b);
      }
  
      void CalcMaskSize(unsigned int &nBytes, unsigned int &nNonzeroBytes) const;
  
      bool IsCoinBase() const {
          return fCoinBase;
      }
  
      unsigned int GetSerializeSize(int nType, int nVersion) const {
          unsigned int nSize = 0;
          unsigned int nMaskSize = 0, nMaskCode = 0;
          CalcMaskSize(nMaskSize, nMaskCode);
          bool fFirst = vout.size() > 0 && !vout[0].IsNull();
          bool fSecond = vout.size() > 1 && !vout[1].IsNull();
          assert(fFirst || fSecond || nMaskCode);
          unsigned int nCode = 8*(nMaskCode - (fFirst || fSecond ? 0 : 1)) + (fCoinBase ? 1 : 0) + (fFirst ? 2 : 0) + (fSecond ? 4 : 0);
          // version
          nSize += ::GetSerializeSize(VARINT(this->nVersion), nType, nVersion);
          // size of header code
          nSize += ::GetSerializeSize(VARINT(nCode), nType, nVersion);
          // spentness bitmask
          nSize += nMaskSize;
          // txouts themself
          for (unsigned int i = 0; i < vout.size(); i++)
              if (!vout[i].IsNull())
                  nSize += ::GetSerializeSize(CTxOutCompressor(REF(vout[i])), nType, nVersion);
          // height
          nSize += ::GetSerializeSize(VARINT(nHeight), nType, nVersion);
          return nSize;
      }
  
      template<typename Stream>
      void Serialize(Stream &s, int nType, int nVersion) const {
          unsigned int nMaskSize = 0, nMaskCode = 0;
          CalcMaskSize(nMaskSize, nMaskCode);
          bool fFirst = vout.size() > 0 && !vout[0].IsNull();
          bool fSecond = vout.size() > 1 && !vout[1].IsNull();
          assert(fFirst || fSecond || nMaskCode);
          unsigned int nCode = 8*(nMaskCode - (fFirst || fSecond ? 0 : 1)) + (fCoinBase ? 1 : 0) + (fFirst ? 2 : 0) + (fSecond ? 4 : 0);
          // version
          ::Serialize(s, VARINT(this->nVersion), nType, nVersion);
          // header code
          ::Serialize(s, VARINT(nCode), nType, nVersion);
          // spentness bitmask
          for (unsigned int b = 0; b<nMaskSize; b++) {
              unsigned char chAvail = 0;
              for (unsigned int i = 0; i < 8 && 2+b*8+i < vout.size(); i++)
                  if (!vout[2+b*8+i].IsNull())
                      chAvail |= (1 << i);
              ::Serialize(s, chAvail, nType, nVersion);
          }
          // txouts themself
          for (unsigned int i = 0; i < vout.size(); i++) {
              if (!vout[i].IsNull())
                  ::Serialize(s, CTxOutCompressor(REF(vout[i])), nType, nVersion);
          }
          // coinbase height
          ::Serialize(s, VARINT(nHeight), nType, nVersion);
      }
  
      template<typename Stream>
      void Unserialize(Stream &s, int nType, int nVersion) {
          unsigned int nCode = 0;
          // version
          ::Unserialize(s, VARINT(this->nVersion), nType, nVersion);
          // header code
          ::Unserialize(s, VARINT(nCode), nType, nVersion);
          fCoinBase = nCode & 1;
          std::vector<bool> vAvail(2, false);
          vAvail[0] = nCode & 2;
          vAvail[1] = nCode & 4;
          unsigned int nMaskCode = (nCode / 8) + ((nCode & 6) != 0 ? 0 : 1);
          // spentness bitmask
          while (nMaskCode > 0) {
              unsigned char chAvail = 0;
              ::Unserialize(s, chAvail, nType, nVersion);
              for (unsigned int p = 0; p < 8; p++) {
                  bool f = (chAvail & (1 << p)) != 0;
                  vAvail.push_back(f);
              }
              if (chAvail != 0)
                  nMaskCode--;
          }
          // txouts themself
          vout.assign(vAvail.size(), CTxOut());
          for (unsigned int i = 0; i < vAvail.size(); i++) {
              if (vAvail[i])
                  ::Unserialize(s, REF(CTxOutCompressor(vout[i])), nType, nVersion);
          }
          // coinbase height
          ::Unserialize(s, VARINT(nHeight), nType, nVersion);
          Cleanup();
      }
  
      // mark an outpoint spent, and construct undo information
      bool Spend(const COutPoint &out, CTxInUndo &undo);
  
      // mark a vout spent
      bool Spend(int nPos);
  
      // check whether a particular output is still available
      bool IsAvailable(unsigned int nPos) const {
          return (nPos < vout.size() && !vout[nPos].IsNull());
      }
  
      // check whether the entire CCoins is spent
      // note that only !IsPruned() CCoins can be serialized
      bool IsPruned() const {
          BOOST_FOREACH(const CTxOut &out, vout)
              if (!out.IsNull())
                  return false;
          return true;
      }
  };
  
  
  struct CCoinsStats
  {
      int nHeight;
      uint256 hashBlock;
      uint64_t nTransactions;
      uint64_t nTransactionOutputs;
      uint64_t nSerializedSize;
      uint256 hashSerialized;
      int64_t nTotalAmount;
  
      CCoinsStats() : nHeight(0), hashBlock(0), nTransactions(0), nTransactionOutputs(0), nSerializedSize(0), hashSerialized(0), nTotalAmount(0) {}
  };
  
  
  /** Abstract view on the open txout dataset. */
  class CCoinsView
  {
  public:
      // Retrieve the CCoins (unspent transaction outputs) for a given txid
      virtual bool GetCoins(const uint256 &txid, CCoins &coins);
  
      // Modify the CCoins for a given txid
      virtual bool SetCoins(const uint256 &txid, const CCoins &coins);
  
      // Just check whether we have data for a given txid.
      // This may (but cannot always) return true for fully spent transactions
      virtual bool HaveCoins(const uint256 &txid);
  
      // Retrieve the block hash whose state this CCoinsView currently represents
      virtual uint256 GetBestBlock();
  
      // Modify the currently active block hash
      virtual bool SetBestBlock(const uint256 &hashBlock);
  
      // Do a bulk modification (multiple SetCoins + one SetBestBlock)
      virtual bool BatchWrite(const std::map<uint256, CCoins> &mapCoins, const uint256 &hashBlock);
  
      // Calculate statistics about the unspent transaction output set
      virtual bool GetStats(CCoinsStats &stats);
  
      // As we use CCoinsViews polymorphically, have a virtual destructor
      virtual ~CCoinsView() {}
  };
  
  
  /** CCoinsView backed by another CCoinsView */
  class CCoinsViewBacked : public CCoinsView
  {
  protected:
      CCoinsView *base;
  
  public:
      CCoinsViewBacked(CCoinsView &viewIn);
      bool GetCoins(const uint256 &txid, CCoins &coins);
      bool SetCoins(const uint256 &txid, const CCoins &coins);
      bool HaveCoins(const uint256 &txid);
      uint256 GetBestBlock();
      bool SetBestBlock(const uint256 &hashBlock);
      void SetBackend(CCoinsView &viewIn);
      bool BatchWrite(const std::map<uint256, CCoins> &mapCoins, const uint256 &hashBlock);
      bool GetStats(CCoinsStats &stats);
  };
  
  
  /** CCoinsView that adds a memory cache for transactions to another CCoinsView */
  class CCoinsViewCache : public CCoinsViewBacked
  {
  protected:
      uint256 hashBlock;
      std::map<uint256,CCoins> cacheCoins;
  
  public:
      CCoinsViewCache(CCoinsView &baseIn, bool fDummy = false);
  
      // Standard CCoinsView methods
      bool GetCoins(const uint256 &txid, CCoins &coins);
      bool SetCoins(const uint256 &txid, const CCoins &coins);
      bool HaveCoins(const uint256 &txid);
      uint256 GetBestBlock();
      bool SetBestBlock(const uint256 &hashBlock);
      bool BatchWrite(const std::map<uint256, CCoins> &mapCoins, const uint256 &hashBlock);
  
      // Return a modifiable reference to a CCoins. Check HaveCoins first.
      // Many methods explicitly require a CCoinsViewCache because of this method, to reduce
      // copying.
      CCoins &GetCoins(const uint256 &txid);
  
      // Push the modifications applied to this cache to its base.
      // Failure to call this method before destruction will cause the changes to be forgotten.
      bool Flush();
  
      // Calculate the size of the cache (in number of transactions)
      unsigned int GetCacheSize();
  
      /** Amount of testinterzones coming in to a transaction
          Note that lightweight clients may not know anything besides the hash of previous transactions,
          so may not be able to calculate this.
  
          @param[in] tx	transaction for which we are checking input total
          @return	Sum of value of all inputs (scriptSigs)
       */
      int64_t GetValueIn(const CTransaction& tx);
  
      // Check whether all prevouts of the transaction are present in the UTXO set represented by this view
      bool HaveInputs(const CTransaction& tx);
  
      // Return priority of tx at height nHeight
      double GetPriority(const CTransaction &tx, int nHeight);
  
      const CTxOut &GetOutputFor(const CTxIn& input);
  
  private:
      std::map<uint256,CCoins>::iterator FetchCoins(const uint256 &txid);
  };
  
  #endif
  