text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2012 The Bitcoin developers
  // Distributed under the MIT/X11 software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  #include <boost/foreach.hpp>
  #include <boost/tuple/tuple.hpp>
  
  using namespace std;
  using namespace boost;
  
  #include "script.h"
  #include "core.h"
  #include "keystore.h"
  #include "bignum.h"
  #include "key.h"
  #include "sync.h"
  #include "util.h"
  
  bool CheckSig(vector<unsigned char> vchSig, const vector<unsigned char> &vchPubKey, const CScript &scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType, int flags);
  
  
  
  typedef vector<unsigned char> valtype;
  static const valtype vchFalse(0);
  static const valtype vchZero(0);
  static const valtype vchTrue(1, 1);
  static const CBigNum bnZero(0);
  static const CBigNum bnOne(1);
  static const CBigNum bnFalse(0);
  static const CBigNum bnTrue(1);
  static const size_t nMaxNumSize = 4;
  
  
  CBigNum CastToBigNum(const valtype& vch)
  {
      if (vch.size() > nMaxNumSize)
          throw runtime_error("CastToBigNum() : overflow");
      // Get rid of extra leading zeros
      return CBigNum(CBigNum(vch).getvch());
  }
  
  bool CastToBool(const valtype& vch)
  {
      for (unsigned int i = 0; i < vch.size(); i++)
      {
          if (vch[i] != 0)
          {
              // Can be negative zero
              if (i == vch.size()-1 && vch[i] == 0x80)
                  return false;
              return true;
          }
      }
      return false;
  }
  
  
  
  //
  // Script is a stack machine (like Forth) that evaluates a predicate
  // returning a bool indicating valid or not.  There are no loops.
  //
  #define stacktop(i)  (stack.at(stack.size()+(i)))
  #define altstacktop(i)  (altstack.at(altstack.size()+(i)))
  static inline void popstack(vector<valtype>& stack)
  {
      if (stack.empty())
          throw runtime_error("popstack() : stack empty");
      stack.pop_back();
  }
  
  
  const char* GetTxnOutputType(txnouttype t)
  {
      switch (t)
      {
      case TX_NONSTANDARD: return "nonstandard";
      case TX_PUBKEY: return "pubkey";
      case TX_PUBKEYHASH: return "pubkeyhash";
      case TX_SCRIPTHASH: return "scripthash";
      case TX_MULTISIG: return "multisig";
      }
      return NULL;
  }
  
  
  const char* GetOpName(opcodetype opcode)
  {
      switch (opcode)
      {
      // push value
      case OP_0                      : return "0";
      case OP_PUSHDATA1              : return "OP_PUSHDATA1";
      case OP_PUSHDATA2              : return "OP_PUSHDATA2";
      case OP_PUSHDATA4              : return "OP_PUSHDATA4";
      case OP_1NEGATE                : return "-1";
      case OP_RESERVED               : return "OP_RESERVED";
      case OP_1                      : return "1";
      case OP_2                      : return "2";
      case OP_3                      : return "3";
      case OP_4                      : return "4";
      case OP_5                      : return "5";
      case OP_6                      : return "6";
      case OP_7                      : return "7";
      case OP_8                      : return "8";
      case OP_9                      : return "9";
      case OP_10                     : return "10";
      case OP_11                     : return "11";
      case OP_12                     : return "12";
      case OP_13                     : return "13";
      case OP_14                     : return "14";
      case OP_15                     : return "15";
      case OP_16                     : return "16";
  
      // control
      case OP_NOP                    : return "OP_NOP";
      case OP_VER                    : return "OP_VER";
      case OP_IF                     : return "OP_IF";
      case OP_NOTIF                  : return "OP_NOTIF";
      case OP_VERIF                  : return "OP_VERIF";
      case OP_VERNOTIF               : return "OP_VERNOTIF";
      case OP_ELSE                   : return "OP_ELSE";
      case OP_ENDIF                  : return "OP_ENDIF";
      case OP_VERIFY                 : return "OP_VERIFY";
      case OP_RETURN                 : return "OP_RETURN";
  
      // stack ops
      case OP_TOALTSTACK             : return "OP_TOALTSTACK";
      case OP_FROMALTSTACK           : return "OP_FROMALTSTACK";
      case OP_2DROP                  : return "OP_2DROP";
      case OP_2DUP                   : return "OP_2DUP";
      case OP_3DUP                   : return "OP_3DUP";
      case OP_2OVER                  : return "OP_2OVER";
      case OP_2ROT                   : return "OP_2ROT";
      case OP_2SWAP                  : return "OP_2SWAP";
      case OP_IFDUP                  : return "OP_IFDUP";
      case OP_DEPTH                  : return "OP_DEPTH";
      case OP_DROP                   : return "OP_DROP";
      case OP_DUP                    : return "OP_DUP";
      case OP_NIP                    : return "OP_NIP";
      case OP_OVER                   : return "OP_OVER";
      case OP_PICK                   : return "OP_PICK";
      case OP_ROLL                   : return "OP_ROLL";
      case OP_ROT                    : return "OP_ROT";
      case OP_SWAP                   : return "OP_SWAP";
      case OP_TUCK                   : return "OP_TUCK";
  
      // splice ops
      case OP_CAT                    : return "OP_CAT";
      case OP_SUBSTR                 : return "OP_SUBSTR";
      case OP_LEFT                   : return "OP_LEFT";
      case OP_RIGHT                  : return "OP_RIGHT";
      case OP_SIZE                   : return "OP_SIZE";
  
      // bit logic
      case OP_INVERT                 : return "OP_INVERT";
      case OP_AND                    : return "OP_AND";
      case OP_OR                     : return "OP_OR";
      case OP_XOR                    : return "OP_XOR";
      case OP_EQUAL                  : return "OP_EQUAL";
      case OP_EQUALVERIFY            : return "OP_EQUALVERIFY";
      case OP_RESERVED1              : return "OP_RESERVED1";
      case OP_RESERVED2              : return "OP_RESERVED2";
  
      // numeric
      case OP_1ADD                   : return "OP_1ADD";
      case OP_1SUB                   : return "OP_1SUB";
      case OP_2MUL                   : return "OP_2MUL";
      case OP_2DIV                   : return "OP_2DIV";
      case OP_NEGATE                 : return "OP_NEGATE";
      case OP_ABS                    : return "OP_ABS";
      case OP_NOT                    : return "OP_NOT";
      case OP_0NOTEQUAL              : return "OP_0NOTEQUAL";
      case OP_ADD                    : return "OP_ADD";
      case OP_SUB                    : return "OP_SUB";
      case OP_MUL                    : return "OP_MUL";
      case OP_DIV                    : return "OP_DIV";
      case OP_MOD                    : return "OP_MOD";
      case OP_LSHIFT                 : return "OP_LSHIFT";
      case OP_RSHIFT                 : return "OP_RSHIFT";
      case OP_BOOLAND                : return "OP_BOOLAND";
      case OP_BOOLOR                 : return "OP_BOOLOR";
      case OP_NUMEQUAL               : return "OP_NUMEQUAL";
      case OP_NUMEQUALVERIFY         : return "OP_NUMEQUALVERIFY";
      case OP_NUMNOTEQUAL            : return "OP_NUMNOTEQUAL";
      case OP_LESSTHAN               : return "OP_LESSTHAN";
      case OP_GREATERTHAN            : return "OP_GREATERTHAN";
      case OP_LESSTHANOREQUAL        : return "OP_LESSTHANOREQUAL";
      case OP_GREATERTHANOREQUAL     : return "OP_GREATERTHANOREQUAL";
      case OP_MIN                    : return "OP_MIN";
      case OP_MAX                    : return "OP_MAX";
      case OP_WITHIN                 : return "OP_WITHIN";
  
      // crypto
      case OP_RIPEMD160              : return "OP_RIPEMD160";
      case OP_SHA1                   : return "OP_SHA1";
      case OP_SHA256                 : return "OP_SHA256";
      case OP_HASH160                : return "OP_HASH160";
      case OP_HASH256                : return "OP_HASH256";
      case OP_CODESEPARATOR          : return "OP_CODESEPARATOR";
      case OP_CHECKSIG               : return "OP_CHECKSIG";
      case OP_CHECKSIGVERIFY         : return "OP_CHECKSIGVERIFY";
      case OP_CHECKMULTISIG          : return "OP_CHECKMULTISIG";
      case OP_CHECKMULTISIGVERIFY    : return "OP_CHECKMULTISIGVERIFY";
  
      // expanson
      case OP_NOP1                   : return "OP_NOP1";
      case OP_NOP2                   : return "OP_NOP2";
      case OP_NOP3                   : return "OP_NOP3";
      case OP_NOP4                   : return "OP_NOP4";
      case OP_NOP5                   : return "OP_NOP5";
      case OP_NOP6                   : return "OP_NOP6";
      case OP_NOP7                   : return "OP_NOP7";
      case OP_NOP8                   : return "OP_NOP8";
      case OP_NOP9                   : return "OP_NOP9";
      case OP_NOP10                  : return "OP_NOP10";
  
  
  
      // template matching params
      case OP_PUBKEYHASH             : return "OP_PUBKEYHASH";
      case OP_PUBKEY                 : return "OP_PUBKEY";
  
      case OP_INVALIDOPCODE          : return "OP_INVALIDOPCODE";
      default:
          return "OP_UNKNOWN";
      }
  }
  
  bool IsCanonicalPubKey(const valtype &vchPubKey, unsigned int flags) {
      if (!(flags & SCRIPT_VERIFY_STRICTENC))
          return true;
  
      if (vchPubKey.size() < 33)
          return error("Non-canonical public key: too short");
      if (vchPubKey[0] == 0x04) {
          if (vchPubKey.size() != 65)
              return error("Non-canonical public key: invalid length for uncompressed key");
      } else if (vchPubKey[0] == 0x02 || vchPubKey[0] == 0x03) {
          if (vchPubKey.size() != 33)
              return error("Non-canonical public key: invalid length for compressed key");
      } else {
          return error("Non-canonical public key: compressed nor uncompressed");
      }
      return true;
  }
  
  bool IsCanonicalSignature(const valtype &vchSig, unsigned int flags) {
      if (!(flags & SCRIPT_VERIFY_STRICTENC))
          return true;
  
      // See https://bitcointalk.org/index.php?topic=8392.msg127623#msg127623
      // A canonical signature exists of: <30> <total len> <02> <len R> <R> <02> <len S> <S> <hashtype>
      // Where R and S are not negative (their first byte has its highest bit not set), and not
      // excessively padded (do not start with a 0 byte, unless an otherwise negative number follows,
      // in which case a single 0 byte is necessary and even required).
      if (vchSig.size() < 9)
          return error("Non-canonical signature: too short");
      if (vchSig.size() > 73)
          return error("Non-canonical signature: too long");
      unsigned char nHashType = vchSig[vchSig.size() - 1] & (~(SIGHASH_ANYONECANPAY));
      if (nHashType < SIGHASH_ALL || nHashType > SIGHASH_SINGLE)
          return error("Non-canonical signature: unknown hashtype byte");
      if (vchSig[0] != 0x30)
          return error("Non-canonical signature: wrong type");
      if (vchSig[1] != vchSig.size()-3)
          return error("Non-canonical signature: wrong length marker");
      unsigned int nLenR = vchSig[3];
      if (5 + nLenR >= vchSig.size())
          return error("Non-canonical signature: S length misplaced");
      unsigned int nLenS = vchSig[5+nLenR];
      if ((unsigned long)(nLenR+nLenS+7) != vchSig.size())
          return error("Non-canonical signature: R+S length mismatch");
  
      const unsigned char *R = &vchSig[4];
      if (R[-2] != 0x02)
          return error("Non-canonical signature: R value type mismatch");
      if (nLenR == 0)
          return error("Non-canonical signature: R length is zero");
      if (R[0] & 0x80)
          return error("Non-canonical signature: R value negative");
      if (nLenR > 1 && (R[0] == 0x00) && !(R[1] & 0x80))
          return error("Non-canonical signature: R value excessively padded");
  
      const unsigned char *S = &vchSig[6+nLenR];
      if (S[-2] != 0x02)
          return error("Non-canonical signature: S value type mismatch");
      if (nLenS == 0)
          return error("Non-canonical signature: S length is zero");
      if (S[0] & 0x80)
          return error("Non-canonical signature: S value negative");
      if (nLenS > 1 && (S[0] == 0x00) && !(S[1] & 0x80))
          return error("Non-canonical signature: S value excessively padded");
  
      if (flags & SCRIPT_VERIFY_EVEN_S) {
          if (S[nLenS-1] & 1)
              return error("Non-canonical signature: S value odd");
      }
  
      return true;
  }
  
  bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, const CTransaction& txTo, unsigned int nIn, unsigned int flags, int nHashType)
  {
      CAutoBN_CTX pctx;
      CScript::const_iterator pc = script.begin();
      CScript::const_iterator pend = script.end();
      CScript::const_iterator pbegincodehash = script.begin();
      opcodetype opcode;
      valtype vchPushValue;
      vector<bool> vfExec;
      vector<valtype> altstack;
      if (script.size() > 10000)
          return false;
      int nOpCount = 0;
  
      try
      {
          while (pc < pend)
          {
              bool fExec = !count(vfExec.begin(), vfExec.end(), false);
  
              //
              // Read instruction
              //
              if (!script.GetOp(pc, opcode, vchPushValue))
                  return false;
              if (vchPushValue.size() > MAX_SCRIPT_ELEMENT_SIZE)
                  return false;
              if (opcode > OP_16 && ++nOpCount > 201)
                  return false;
  
              if (opcode == OP_CAT ||
                  opcode == OP_SUBSTR ||
                  opcode == OP_LEFT ||
                  opcode == OP_RIGHT ||
                  opcode == OP_INVERT ||
                  opcode == OP_AND ||
                  opcode == OP_OR ||
                  opcode == OP_XOR ||
                  opcode == OP_2MUL ||
                  opcode == OP_2DIV ||
                  opcode == OP_MUL ||
                  opcode == OP_DIV ||
                  opcode == OP_MOD ||
                  opcode == OP_LSHIFT ||
                  opcode == OP_RSHIFT)
                  return false; // Disabled opcodes.
  
              if (fExec && 0 <= opcode && opcode <= OP_PUSHDATA4)
                  stack.push_back(vchPushValue);
              else if (fExec || (OP_IF <= opcode && opcode <= OP_ENDIF))
              switch (opcode)
              {
                  //
                  // Push value
                  //
                  case OP_1NEGATE:
                  case OP_1:
                  case OP_2:
                  case OP_3:
                  case OP_4:
                  case OP_5:
                  case OP_6:
                  case OP_7:
                  case OP_8:
                  case OP_9:
                  case OP_10:
                  case OP_11:
                  case OP_12:
                  case OP_13:
                  case OP_14:
                  case OP_15:
                  case OP_16:
                  {
                      // ( -- value)
                      CBigNum bn((int)opcode - (int)(OP_1 - 1));
                      stack.push_back(bn.getvch());
                  }
                  break;
  
  
                  //
                  // Control
                  //
                  case OP_NOP:
                  case OP_NOP1: case OP_NOP2: case OP_NOP3: case OP_NOP4: case OP_NOP5:
                  case OP_NOP6: case OP_NOP7: case OP_NOP8: case OP_NOP9: case OP_NOP10:
                  break;
  
                  case OP_IF:
                  case OP_NOTIF:
                  {
                      // <expression> if [statements] [else [statements]] endif
                      bool fValue = false;
                      if (fExec)
                      {
                          if (stack.size() < 1)
                              return false;
                          valtype& vch = stacktop(-1);
                          fValue = CastToBool(vch);
                          if (opcode == OP_NOTIF)
                              fValue = !fValue;
                          popstack(stack);
                      }
                      vfExec.push_back(fValue);
                  }
                  break;
  
                  case OP_ELSE:
                  {
                      if (vfExec.empty())
                          return false;
                      vfExec.back() = !vfExec.back();
                  }
                  break;
  
                  case OP_ENDIF:
                  {
                      if (vfExec.empty())
                          return false;
                      vfExec.pop_back();
                  }
                  break;
  
                  case OP_VERIFY:
                  {
                      // (true -- ) or
                      // (false -- false) and return
                      if (stack.size() < 1)
                          return false;
                      bool fValue = CastToBool(stacktop(-1));
                      if (fValue)
                          popstack(stack);
                      else
                          return false;
                  }
                  break;
  
                  case OP_RETURN:
                  {
                      return false;
                  }
                  break;
  
  
                  //
                  // Stack ops
                  //
                  case OP_TOALTSTACK:
                  {
                      if (stack.size() < 1)
                          return false;
                      altstack.push_back(stacktop(-1));
                      popstack(stack);
                  }
                  break;
  
                  case OP_FROMALTSTACK:
                  {
                      if (altstack.size() < 1)
                          return false;
                      stack.push_back(altstacktop(-1));
                      popstack(altstack);
                  }
                  break;
  
                  case OP_2DROP:
                  {
                      // (x1 x2 -- )
                      if (stack.size() < 2)
                          return false;
                      popstack(stack);
                      popstack(stack);
                  }
                  break;
  
                  case OP_2DUP:
                  {
                      // (x1 x2 -- x1 x2 x1 x2)
                      if (stack.size() < 2)
                          return false;
                      valtype vch1 = stacktop(-2);
                      valtype vch2 = stacktop(-1);
                      stack.push_back(vch1);
                      stack.push_back(vch2);
                  }
                  break;
  
                  case OP_3DUP:
                  {
                      // (x1 x2 x3 -- x1 x2 x3 x1 x2 x3)
                      if (stack.size() < 3)
                          return false;
                      valtype vch1 = stacktop(-3);
                      valtype vch2 = stacktop(-2);
                      valtype vch3 = stacktop(-1);
                      stack.push_back(vch1);
                      stack.push_back(vch2);
                      stack.push_back(vch3);
                  }
                  break;
  
                  case OP_2OVER:
                  {
                      // (x1 x2 x3 x4 -- x1 x2 x3 x4 x1 x2)
                      if (stack.size() < 4)
                          return false;
                      valtype vch1 = stacktop(-4);
                      valtype vch2 = stacktop(-3);
                      stack.push_back(vch1);
                      stack.push_back(vch2);
                  }
                  break;
  
                  case OP_2ROT:
                  {
                      // (x1 x2 x3 x4 x5 x6 -- x3 x4 x5 x6 x1 x2)
                      if (stack.size() < 6)
                          return false;
                      valtype vch1 = stacktop(-6);
                      valtype vch2 = stacktop(-5);
                      stack.erase(stack.end()-6, stack.end()-4);
                      stack.push_back(vch1);
                      stack.push_back(vch2);
                  }
                  break;
  
                  case OP_2SWAP:
                  {
                      // (x1 x2 x3 x4 -- x3 x4 x1 x2)
                      if (stack.size() < 4)
                          return false;
                      swap(stacktop(-4), stacktop(-2));
                      swap(stacktop(-3), stacktop(-1));
                  }
                  break;
  
                  case OP_IFDUP:
                  {
                      // (x - 0 | x x)
                      if (stack.size() < 1)
                          return false;
                      valtype vch = stacktop(-1);
                      if (CastToBool(vch))
                          stack.push_back(vch);
                  }
                  break;
  
                  case OP_DEPTH:
                  {
                      // -- stacksize
                      CBigNum bn(stack.size());
                      stack.push_back(bn.getvch());
                  }
                  break;
  
                  case OP_DROP:
                  {
                      // (x -- )
                      if (stack.size() < 1)
                          return false;
                      popstack(stack);
                  }
                  break;
  
                  case OP_DUP:
                  {
                      // (x -- x x)
                      if (stack.size() < 1)
                          return false;
                      valtype vch = stacktop(-1);
                      stack.push_back(vch);
                  }
                  break;
  
                  case OP_NIP:
                  {
                      // (x1 x2 -- x2)
                      if (stack.size() < 2)
                          return false;
                      stack.erase(stack.end() - 2);
                  }
                  break;
  
                  case OP_OVER:
                  {
                      // (x1 x2 -- x1 x2 x1)
                      if (stack.size() < 2)
                          return false;
                      valtype vch = stacktop(-2);
                      stack.push_back(vch);
                  }
                  break;
  
                  case OP_PICK:
                  case OP_ROLL:
                  {
                      // (xn ... x2 x1 x0 n - xn ... x2 x1 x0 xn)
                      // (xn ... x2 x1 x0 n - ... x2 x1 x0 xn)
                      if (stack.size() < 2)
                          return false;
                      int n = CastToBigNum(stacktop(-1)).getint();
                      popstack(stack);
                      if (n < 0 || n >= (int)stack.size())
                          return false;
                      valtype vch = stacktop(-n-1);
                      if (opcode == OP_ROLL)
                          stack.erase(stack.end()-n-1);
                      stack.push_back(vch);
                  }
                  break;
  
                  case OP_ROT:
                  {
                      // (x1 x2 x3 -- x2 x3 x1)
                      //  x2 x1 x3  after first swap
                      //  x2 x3 x1  after second swap
                      if (stack.size() < 3)
                          return false;
                      swap(stacktop(-3), stacktop(-2));
                      swap(stacktop(-2), stacktop(-1));
                  }
                  break;
  
                  case OP_SWAP:
                  {
                      // (x1 x2 -- x2 x1)
                      if (stack.size() < 2)
                          return false;
                      swap(stacktop(-2), stacktop(-1));
                  }
                  break;
  
                  case OP_TUCK:
                  {
                      // (x1 x2 -- x2 x1 x2)
                      if (stack.size() < 2)
                          return false;
                      valtype vch = stacktop(-1);
                      stack.insert(stack.end()-2, vch);
                  }
                  break;
  
  
                  case OP_SIZE:
                  {
                      // (in -- in size)
                      if (stack.size() < 1)
                          return false;
                      CBigNum bn(stacktop(-1).size());
                      stack.push_back(bn.getvch());
                  }
                  break;
  
  
                  //
                  // Bitwise logic
                  //
                  case OP_EQUAL:
                  case OP_EQUALVERIFY:
                  //case OP_NOTEQUAL: // use OP_NUMNOTEQUAL
                  {
                      // (x1 x2 - bool)
                      if (stack.size() < 2)
                          return false;
                      valtype& vch1 = stacktop(-2);
                      valtype& vch2 = stacktop(-1);
                      bool fEqual = (vch1 == vch2);
                      // OP_NOTEQUAL is disabled because it would be too easy to say
                      // something like n != 1 and have some wiseguy pass in 1 with extra
                      // zero bytes after it (numerically, 0x01 == 0x0001 == 0x000001)
                      //if (opcode == OP_NOTEQUAL)
                      //    fEqual = !fEqual;
                      popstack(stack);
                      popstack(stack);
                      stack.push_back(fEqual ? vchTrue : vchFalse);
                      if (opcode == OP_EQUALVERIFY)
                      {
                          if (fEqual)
                              popstack(stack);
                          else
                              return false;
                      }
                  }
                  break;
  
  
                  //
                  // Numeric
                  //
                  case OP_1ADD:
                  case OP_1SUB:
                  case OP_NEGATE:
                  case OP_ABS:
                  case OP_NOT:
                  case OP_0NOTEQUAL:
                  {
                      // (in -- out)
                      if (stack.size() < 1)
                          return false;
                      CBigNum bn = CastToBigNum(stacktop(-1));
                      switch (opcode)
                      {
                      case OP_1ADD:       bn += bnOne; break;
                      case OP_1SUB:       bn -= bnOne; break;
                      case OP_NEGATE:     bn = -bn; break;
                      case OP_ABS:        if (bn < bnZero) bn = -bn; break;
                      case OP_NOT:        bn = (bn == bnZero); break;
                      case OP_0NOTEQUAL:  bn = (bn != bnZero); break;
                      default:            assert(!"invalid opcode"); break;
                      }
                      popstack(stack);
                      stack.push_back(bn.getvch());
                  }
                  break;
  
                  case OP_ADD:
                  case OP_SUB:
                  case OP_BOOLAND:
                  case OP_BOOLOR:
                  case OP_NUMEQUAL:
                  case OP_NUMEQUALVERIFY:
                  case OP_NUMNOTEQUAL:
                  case OP_LESSTHAN:
                  case OP_GREATERTHAN:
                  case OP_LESSTHANOREQUAL:
                  case OP_GREATERTHANOREQUAL:
                  case OP_MIN:
                  case OP_MAX:
                  {
                      // (x1 x2 -- out)
                      if (stack.size() < 2)
                          return false;
                      CBigNum bn1 = CastToBigNum(stacktop(-2));
                      CBigNum bn2 = CastToBigNum(stacktop(-1));
                      CBigNum bn;
                      switch (opcode)
                      {
                      case OP_ADD:
                          bn = bn1 + bn2;
                          break;
  
                      case OP_SUB:
                          bn = bn1 - bn2;
                          break;
  
                      case OP_BOOLAND:             bn = (bn1 != bnZero && bn2 != bnZero); break;
                      case OP_BOOLOR:              bn = (bn1 != bnZero || bn2 != bnZero); break;
                      case OP_NUMEQUAL:            bn = (bn1 == bn2); break;
                      case OP_NUMEQUALVERIFY:      bn = (bn1 == bn2); break;
                      case OP_NUMNOTEQUAL:         bn = (bn1 != bn2); break;
                      case OP_LESSTHAN:            bn = (bn1 < bn2); break;
                      case OP_GREATERTHAN:         bn = (bn1 > bn2); break;
                      case OP_LESSTHANOREQUAL:     bn = (bn1 <= bn2); break;
                      case OP_GREATERTHANOREQUAL:  bn = (bn1 >= bn2); break;
                      case OP_MIN:                 bn = (bn1 < bn2 ? bn1 : bn2); break;
                      case OP_MAX:                 bn = (bn1 > bn2 ? bn1 : bn2); break;
                      default:                     assert(!"invalid opcode"); break;
                      }
                      popstack(stack);
                      popstack(stack);
                      stack.push_back(bn.getvch());
  
                      if (opcode == OP_NUMEQUALVERIFY)
                      {
                          if (CastToBool(stacktop(-1)))
                              popstack(stack);
                          else
                              return false;
                      }
                  }
                  break;
  
                  case OP_WITHIN:
                  {
                      // (x min max -- out)
                      if (stack.size() < 3)
                          return false;
                      CBigNum bn1 = CastToBigNum(stacktop(-3));
                      CBigNum bn2 = CastToBigNum(stacktop(-2));
                      CBigNum bn3 = CastToBigNum(stacktop(-1));
                      bool fValue = (bn2 <= bn1 && bn1 < bn3);
                      popstack(stack);
                      popstack(stack);
                      popstack(stack);
                      stack.push_back(fValue ? vchTrue : vchFalse);
                  }
                  break;
  
  
                  //
                  // Crypto
                  //
                  case OP_RIPEMD160:
                  case OP_SHA1:
                  case OP_SHA256:
                  case OP_HASH160:
                  case OP_HASH256:
                  {
                      // (in -- hash)
                      if (stack.size() < 1)
                          return false;
                      valtype& vch = stacktop(-1);
                      valtype vchHash((opcode == OP_RIPEMD160 || opcode == OP_SHA1 || opcode == OP_HASH160) ? 20 : 32);
                      if (opcode == OP_RIPEMD160)
                          RIPEMD160(&vch[0], vch.size(), &vchHash[0]);
                      else if (opcode == OP_SHA1)
                          SHA1(&vch[0], vch.size(), &vchHash[0]);
                      else if (opcode == OP_SHA256)
                          SHA256(&vch[0], vch.size(), &vchHash[0]);
                      else if (opcode == OP_HASH160)
                      {
                          uint160 hash160 = Hash160(vch);
                          memcpy(&vchHash[0], &hash160, sizeof(hash160));
                      }
                      else if (opcode == OP_HASH256)
                      {
                          uint256 hash = Hash(vch.begin(), vch.end());
                          memcpy(&vchHash[0], &hash, sizeof(hash));
                      }
                      popstack(stack);
                      stack.push_back(vchHash);
                  }
                  break;
  
                  case OP_CODESEPARATOR:
                  {
                      // Hash starts after the code separator
                      pbegincodehash = pc;
                  }
                  break;
  
                  case OP_CHECKSIG:
                  case OP_CHECKSIGVERIFY:
                  {
                      // (sig pubkey -- bool)
                      if (stack.size() < 2)
                          return false;
  
                      valtype& vchSig    = stacktop(-2);
                      valtype& vchPubKey = stacktop(-1);
  
                      ////// debug print
                      //PrintHex(vchSig.begin(), vchSig.end(), "sig: %s\n");
                      //PrintHex(vchPubKey.begin(), vchPubKey.end(), "pubkey: %s\n");
  
                      // Subset of script starting at the most recent codeseparator
                      CScript scriptCode(pbegincodehash, pend);
  
                      // Drop the signature, since there's no way for a signature to sign itself
                      scriptCode.FindAndDelete(CScript(vchSig));
  
                      bool fSuccess = IsCanonicalSignature(vchSig, flags) && IsCanonicalPubKey(vchPubKey, flags) &&
                          CheckSig(vchSig, vchPubKey, scriptCode, txTo, nIn, nHashType, flags);
  
                      popstack(stack);
                      popstack(stack);
                      stack.push_back(fSuccess ? vchTrue : vchFalse);
                      if (opcode == OP_CHECKSIGVERIFY)
                      {
                          if (fSuccess)
                              popstack(stack);
                          else
                              return false;
                      }
                  }
                  break;
  
                  case OP_CHECKMULTISIG:
                  case OP_CHECKMULTISIGVERIFY:
                  {
                      // ([sig ...] num_of_signatures [pubkey ...] num_of_pubkeys -- bool)
  
                      int i = 1;
                      if ((int)stack.size() < i)
                          return false;
  
                      int nKeysCount = CastToBigNum(stacktop(-i)).getint();
                      if (nKeysCount < 0 || nKeysCount > 20)
                          return false;
                      nOpCount += nKeysCount;
                      if (nOpCount > 201)
                          return false;
                      int ikey = ++i;
                      i += nKeysCount;
                      if ((int)stack.size() < i)
                          return false;
  
                      int nSigsCount = CastToBigNum(stacktop(-i)).getint();
                      if (nSigsCount < 0 || nSigsCount > nKeysCount)
                          return false;
                      int isig = ++i;
                      i += nSigsCount;
                      if ((int)stack.size() < i)
                          return false;
  
                      // Subset of script starting at the most recent codeseparator
                      CScript scriptCode(pbegincodehash, pend);
  
                      // Drop the signatures, since there's no way for a signature to sign itself
                      for (int k = 0; k < nSigsCount; k++)
                      {
                          valtype& vchSig = stacktop(-isig-k);
                          scriptCode.FindAndDelete(CScript(vchSig));
                      }
  
                      bool fSuccess = true;
                      while (fSuccess && nSigsCount > 0)
                      {
                          valtype& vchSig    = stacktop(-isig);
                          valtype& vchPubKey = stacktop(-ikey);
  
                          // Check signature
                          bool fOk = IsCanonicalSignature(vchSig, flags) && IsCanonicalPubKey(vchPubKey, flags) &&
                              CheckSig(vchSig, vchPubKey, scriptCode, txTo, nIn, nHashType, flags);
  
                          if (fOk) {
                              isig++;
                              nSigsCount--;
                          }
                          ikey++;
                          nKeysCount--;
  
                          // If there are more signatures left than keys left,
                          // then too many signatures have failed
                          if (nSigsCount > nKeysCount)
                              fSuccess = false;
                      }
  
                      while (i-- > 0)
                          popstack(stack);
                      stack.push_back(fSuccess ? vchTrue : vchFalse);
  
                      if (opcode == OP_CHECKMULTISIGVERIFY)
                      {
                          if (fSuccess)
                              popstack(stack);
                          else
                              return false;
                      }
                  }
                  break;
  
                  default:
                      return false;
              }
  
              // Size limits
              if (stack.size() + altstack.size() > 1000)
                  return false;
          }
      }
      catch (...)
      {
          return false;
      }
  
  
      if (!vfExec.empty())
          return false;
  
      return true;
  }
  
  
  
  
  
  
  
  
  
  uint256 SignatureHash(CScript scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType)
  {
      if (nIn >= txTo.vin.size())
      {
          printf("ERROR: SignatureHash() : nIn=%d out of range\n", nIn);
          return 1;
      }
      CTransaction txTmp(txTo);
  
      // In case concatenating two scripts ends up with two codeseparators,
      // or an extra one at the end, this prevents all those possible incompatibilities.
      scriptCode.FindAndDelete(CScript(OP_CODESEPARATOR));
  
      // Blank out other inputs' signatures
      for (unsigned int i = 0; i < txTmp.vin.size(); i++)
          txTmp.vin[i].scriptSig = CScript();
      txTmp.vin[nIn].scriptSig = scriptCode;
  
      // Blank out some of the outputs
      if ((nHashType & 0x1f) == SIGHASH_NONE)
      {
          // Wildcard payee
          txTmp.vout.clear();
  
          // Let the others update at will
          for (unsigned int i = 0; i < txTmp.vin.size(); i++)
              if (i != nIn)
                  txTmp.vin[i].nSequence = 0;
      }
      else if ((nHashType & 0x1f) == SIGHASH_SINGLE)
      {
          // Only lock-in the txout payee at same index as txin
          unsigned int nOut = nIn;
          if (nOut >= txTmp.vout.size())
          {
              printf("ERROR: SignatureHash() : nOut=%d out of range\n", nOut);
              return 1;
          }
          txTmp.vout.resize(nOut+1);
          for (unsigned int i = 0; i < nOut; i++)
              txTmp.vout[i].SetNull();
  
          // Let the others update at will
          for (unsigned int i = 0; i < txTmp.vin.size(); i++)
              if (i != nIn)
                  txTmp.vin[i].nSequence = 0;
      }
  
      // Blank out other inputs completely, not recommended for open transactions
      if (nHashType & SIGHASH_ANYONECANPAY)
      {
          txTmp.vin[0] = txTmp.vin[nIn];
          txTmp.vin.resize(1);
      }
  
      // Serialize and hash
      CHashWriter ss(SER_GETHASH, 0);
      ss << txTmp << nHashType;
      return ss.GetHash();
  }
  
  
  // Valid signature cache, to avoid doing expensive ECDSA signature checking
  // twice for every transaction (once when accepted into memory pool, and
  // again when accepted into the block chain)
  
  class CSignatureCache
  {
  private:
       // sigdata_type is (signature hash, signature, public key):
      typedef boost::tuple<uint256, std::vector<unsigned char>, CPubKey> sigdata_type;
      std::set< sigdata_type> setValid;
      boost::shared_mutex cs_sigcache;
  
  public:
      bool
      Get(const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& pubKey)
      {
          boost::shared_lock<boost::shared_mutex> lock(cs_sigcache);
  
          sigdata_type k(hash, vchSig, pubKey);
          std::set<sigdata_type>::iterator mi = setValid.find(k);
          if (mi != setValid.end())
              return true;
          return false;
      }
  
      void Set(const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& pubKey)
      {
          // DoS prevention: limit cache size to less than 10MB
          // (~200 bytes per cache entry times 50,000 entries)
          // Since there are a maximum of 20,000 signature operations per block
          // 50,000 is a reasonable default.
          int64 nMaxCacheSize = GetArg("-maxsigcachesize", 50000);
          if (nMaxCacheSize <= 0) return;
  
          boost::unique_lock<boost::shared_mutex> lock(cs_sigcache);
  
          while (static_cast<int64>(setValid.size()) > nMaxCacheSize)
          {
              // Evict a random entry. Random because that helps
              // foil would-be DoS attackers who might try to pre-generate
              // and re-use a set of valid signatures just-slightly-greater
              // than our cache size.
              uint256 randomHash = GetRandHash();
              std::vector<unsigned char> unused;
              std::set<sigdata_type>::iterator it =
                  setValid.lower_bound(sigdata_type(randomHash, unused, unused));
              if (it == setValid.end())
                  it = setValid.begin();
              setValid.erase(*it);
          }
  
          sigdata_type k(hash, vchSig, pubKey);
          setValid.insert(k);
      }
  };
  
  bool CheckSig(vector<unsigned char> vchSig, const vector<unsigned char> &vchPubKey, const CScript &scriptCode,
                const CTransaction& txTo, unsigned int nIn, int nHashType, int flags)
  {
      static CSignatureCache signatureCache;
  
      CPubKey pubkey(vchPubKey);
      if (!pubkey.IsValid())
          return false;
  
      // Hash type is one byte tacked on to the end of the signature
      if (vchSig.empty())
          return false;
      if (nHashType == 0)
          nHashType = vchSig.back();
      else if (nHashType != vchSig.back())
          return false;
      vchSig.pop_back();
  
      uint256 sighash = SignatureHash(scriptCode, txTo, nIn, nHashType);
  
      if (signatureCache.Get(sighash, vchSig, pubkey))
          return true;
  
      if (!pubkey.Verify(sighash, vchSig))
          return false;
  
      if (!(flags & SCRIPT_VERIFY_NOCACHE))
          signatureCache.Set(sighash, vchSig, pubkey);
  
      return true;
  }
  
  
  
  
  
  
  
  
  
  //
  // Return public keys or hashes from scriptPubKey, for 'standard' transaction types.
  //
  bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, vector<vector<unsigned char> >& vSolutionsRet)
  {
      // Templates
      static map<txnouttype, CScript> mTemplates;
      if (mTemplates.empty())
      {
          // Standard tx, sender provides pubkey, receiver adds signature
          mTemplates.insert(make_pair(TX_PUBKEY, CScript() << OP_PUBKEY << OP_CHECKSIG));
  
          // Bitcoin address tx, sender provides hash of pubkey, receiver provides signature and pubkey
          mTemplates.insert(make_pair(TX_PUBKEYHASH, CScript() << OP_DUP << OP_HASH160 << OP_PUBKEYHASH << OP_EQUALVERIFY << OP_CHECKSIG));
  
          // Sender provides N pubkeys, receivers provides M signatures
          mTemplates.insert(make_pair(TX_MULTISIG, CScript() << OP_SMALLINTEGER << OP_PUBKEYS << OP_SMALLINTEGER << OP_CHECKMULTISIG));
      }
  
      // Shortcut for pay-to-script-hash, which are more constrained than the other types:
      // it is always OP_HASH160 20 [20 byte hash] OP_EQUAL
      if (scriptPubKey.IsPayToScriptHash())
      {
          typeRet = TX_SCRIPTHASH;
          vector<unsigned char> hashBytes(scriptPubKey.begin()+2, scriptPubKey.begin()+22);
          vSolutionsRet.push_back(hashBytes);
          return true;
      }
  
      // Scan templates
      const CScript& script1 = scriptPubKey;
      BOOST_FOREACH(const PAIRTYPE(txnouttype, CScript)& tplate, mTemplates)
      {
          const CScript& script2 = tplate.second;
          vSolutionsRet.clear();
  
          opcodetype opcode1, opcode2;
          vector<unsigned char> vch1, vch2;
  
          // Compare
          CScript::const_iterator pc1 = script1.begin();
          CScript::const_iterator pc2 = script2.begin();
          while (true)
          {
              if (pc1 == script1.end() && pc2 == script2.end())
              {
                  // Found a match
                  typeRet = tplate.first;
                  if (typeRet == TX_MULTISIG)
                  {
                      // Additional checks for TX_MULTISIG:
                      unsigned char m = vSolutionsRet.front()[0];
                      unsigned char n = vSolutionsRet.back()[0];
                      if (m < 1 || n < 1 || m > n || vSolutionsRet.size()-2 != n)
                          return false;
                  }
                  return true;
              }
              if (!script1.GetOp(pc1, opcode1, vch1))
                  break;
              if (!script2.GetOp(pc2, opcode2, vch2))
                  break;
  
              // Template matching opcodes:
              if (opcode2 == OP_PUBKEYS)
              {
                  while (vch1.size() >= 33 && vch1.size() <= 120)
                  {
                      vSolutionsRet.push_back(vch1);
                      if (!script1.GetOp(pc1, opcode1, vch1))
                          break;
                  }
                  if (!script2.GetOp(pc2, opcode2, vch2))
                      break;
                  // Normal situation is to fall through
                  // to other if/else statements
              }
  
              if (opcode2 == OP_PUBKEY)
              {
                  if (vch1.size() < 33 || vch1.size() > 120)
                      break;
                  vSolutionsRet.push_back(vch1);
              }
              else if (opcode2 == OP_PUBKEYHASH)
              {
                  if (vch1.size() != sizeof(uint160))
                      break;
                  vSolutionsRet.push_back(vch1);
              }
              else if (opcode2 == OP_SMALLINTEGER)
              {   // Single-byte small integer pushed onto vSolutions
                  if (opcode1 == OP_0 ||
                      (opcode1 >= OP_1 && opcode1 <= OP_16))
                  {
                      char n = (char)CScript::DecodeOP_N(opcode1);
                      vSolutionsRet.push_back(valtype(1, n));
                  }
                  else
                      break;
              }
              else if (opcode1 != opcode2 || vch1 != vch2)
              {
                  // Others must match exactly
                  break;
              }
          }
      }
  
      vSolutionsRet.clear();
      typeRet = TX_NONSTANDARD;
      return false;
  }
  
  
  bool Sign1(const CKeyID& address, const CKeyStore& keystore, uint256 hash, int nHashType, CScript& scriptSigRet)
  {
      CKey key;
      if (!keystore.GetKey(address, key))
          return false;
  
      vector<unsigned char> vchSig;
      if (!key.Sign(hash, vchSig))
          return false;
      vchSig.push_back((unsigned char)nHashType);
      scriptSigRet << vchSig;
  
      return true;
  }
  
  bool SignN(const vector<valtype>& multisigdata, const CKeyStore& keystore, uint256 hash, int nHashType, CScript& scriptSigRet)
  {
      int nSigned = 0;
      int nRequired = multisigdata.front()[0];
      for (unsigned int i = 1; i < multisigdata.size()-1 && nSigned < nRequired; i++)
      {
          const valtype& pubkey = multisigdata[i];
          CKeyID keyID = CPubKey(pubkey).GetID();
          if (Sign1(keyID, keystore, hash, nHashType, scriptSigRet))
              ++nSigned;
      }
      return nSigned==nRequired;
  }
  
  //
  // Sign scriptPubKey with private keys stored in keystore, given transaction hash and hash type.
  // Signatures are returned in scriptSigRet (or returns false if scriptPubKey can't be signed),
  // unless whichTypeRet is TX_SCRIPTHASH, in which case scriptSigRet is the redemption script.
  // Returns false if scriptPubKey could not be completely satisfied.
  //
  bool Solver(const CKeyStore& keystore, const CScript& scriptPubKey, uint256 hash, int nHashType,
                    CScript& scriptSigRet, txnouttype& whichTypeRet)
  {
      scriptSigRet.clear();
  
      vector<valtype> vSolutions;
      if (!Solver(scriptPubKey, whichTypeRet, vSolutions))
          return false;
  
      CKeyID keyID;
      switch (whichTypeRet)
      {
      case TX_NONSTANDARD:
          return false;
      case TX_PUBKEY:
          keyID = CPubKey(vSolutions[0]).GetID();
          return Sign1(keyID, keystore, hash, nHashType, scriptSigRet);
      case TX_PUBKEYHASH:
          keyID = CKeyID(uint160(vSolutions[0]));
          if (!Sign1(keyID, keystore, hash, nHashType, scriptSigRet))
              return false;
          else
          {
              CPubKey vch;
              keystore.GetPubKey(keyID, vch);
              scriptSigRet << vch;
          }
          return true;
      case TX_SCRIPTHASH:
          return keystore.GetCScript(uint160(vSolutions[0]), scriptSigRet);
  
      case TX_MULTISIG:
          scriptSigRet << OP_0; // workaround CHECKMULTISIG bug
          return (SignN(vSolutions, keystore, hash, nHashType, scriptSigRet));
      }
      return false;
  }
  
  int ScriptSigArgsExpected(txnouttype t, const std::vector<std::vector<unsigned char> >& vSolutions)
  {
      switch (t)
      {
      case TX_NONSTANDARD:
          return -1;
      case TX_PUBKEY:
          return 1;
      case TX_PUBKEYHASH:
          return 2;
      case TX_MULTISIG:
          if (vSolutions.size() < 1 || vSolutions[0].size() < 1)
              return -1;
          return vSolutions[0][0] + 1;
      case TX_SCRIPTHASH:
          return 1; // doesn't include args needed by the script
      }
      return -1;
  }
  
  bool IsStandard(const CScript& scriptPubKey)
  {
      vector<valtype> vSolutions;
      txnouttype whichType;
      if (!Solver(scriptPubKey, whichType, vSolutions))
          return false;
  
      if (whichType == TX_MULTISIG)
      {
          unsigned char m = vSolutions.front()[0];
          unsigned char n = vSolutions.back()[0];
          // Support up to x-of-3 multisig txns as standard
          if (n < 1 || n > 3)
              return false;
          if (m < 1 || m > n)
              return false;
      }
  
      return whichType != TX_NONSTANDARD;
  }
  
  
  unsigned int HaveKeys(const vector<valtype>& pubkeys, const CKeyStore& keystore)
  {
      unsigned int nResult = 0;
      BOOST_FOREACH(const valtype& pubkey, pubkeys)
      {
          CKeyID keyID = CPubKey(pubkey).GetID();
          if (keystore.HaveKey(keyID))
              ++nResult;
      }
      return nResult;
  }
  
  
  class CKeyStoreIsMineVisitor : public boost::static_visitor<bool>
  {
  private:
      const CKeyStore *keystore;
  public:
      CKeyStoreIsMineVisitor(const CKeyStore *keystoreIn) : keystore(keystoreIn) { }
      bool operator()(const CNoDestination &dest) const { return false; }
      bool operator()(const CKeyID &keyID) const { return keystore->HaveKey(keyID); }
      bool operator()(const CScriptID &scriptID) const { return keystore->HaveCScript(scriptID); }
  };
  
  bool IsMine(const CKeyStore &keystore, const CTxDestination &dest)
  {
      return boost::apply_visitor(CKeyStoreIsMineVisitor(&keystore), dest);
  }
  
  bool IsMine(const CKeyStore &keystore, const CScript& scriptPubKey)
  {
      vector<valtype> vSolutions;
      txnouttype whichType;
      if (!Solver(scriptPubKey, whichType, vSolutions))
          return false;
  
      CKeyID keyID;
      switch (whichType)
      {
      case TX_NONSTANDARD:
          return false;
      case TX_PUBKEY:
          keyID = CPubKey(vSolutions[0]).GetID();
          return keystore.HaveKey(keyID);
      case TX_PUBKEYHASH:
          keyID = CKeyID(uint160(vSolutions[0]));
          return keystore.HaveKey(keyID);
      case TX_SCRIPTHASH:
      {
          CScript subscript;
          if (!keystore.GetCScript(CScriptID(uint160(vSolutions[0])), subscript))
              return false;
          return IsMine(keystore, subscript);
      }
      case TX_MULTISIG:
      {
          // Only consider transactions "mine" if we own ALL the
          // keys involved. multi-signature transactions that are
          // partially owned (somebody else has a key that can spend
          // them) enable spend-out-from-under-you attacks, especially
          // in shared-wallet situations.
          vector<valtype> keys(vSolutions.begin()+1, vSolutions.begin()+vSolutions.size()-1);
          return HaveKeys(keys, keystore) == keys.size();
      }
      }
      return false;
  }
  
  bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet)
  {
      vector<valtype> vSolutions;
      txnouttype whichType;
      if (!Solver(scriptPubKey, whichType, vSolutions))
          return false;
  
      if (whichType == TX_PUBKEY)
      {
          addressRet = CPubKey(vSolutions[0]).GetID();
          return true;
      }
      else if (whichType == TX_PUBKEYHASH)
      {
          addressRet = CKeyID(uint160(vSolutions[0]));
          return true;
      }
      else if (whichType == TX_SCRIPTHASH)
      {
          addressRet = CScriptID(uint160(vSolutions[0]));
          return true;
      }
      // Multisig txns have more than one address...
      return false;
  }
  
  bool ExtractDestinations(const CScript& scriptPubKey, txnouttype& typeRet, vector<CTxDestination>& addressRet, int& nRequiredRet)
  {
      addressRet.clear();
      typeRet = TX_NONSTANDARD;
      vector<valtype> vSolutions;
      if (!Solver(scriptPubKey, typeRet, vSolutions))
          return false;
  
      if (typeRet == TX_MULTISIG)
      {
          nRequiredRet = vSolutions.front()[0];
          for (unsigned int i = 1; i < vSolutions.size()-1; i++)
          {
              CTxDestination address = CPubKey(vSolutions[i]).GetID();
              addressRet.push_back(address);
          }
      }
      else
      {
          nRequiredRet = 1;
          CTxDestination address;
          if (!ExtractDestination(scriptPubKey, address))
             return false;
          addressRet.push_back(address);
      }
  
      return true;
  }
  
  class CAffectedKeysVisitor : public boost::static_visitor<void> {
  private:
      const CKeyStore &keystore;
      std::vector<CKeyID> &vKeys;
  
  public:
      CAffectedKeysVisitor(const CKeyStore &keystoreIn, std::vector<CKeyID> &vKeysIn) : keystore(keystoreIn), vKeys(vKeysIn) {}
  
      void Process(const CScript &script) {
          txnouttype type;
          std::vector<CTxDestination> vDest;
          int nRequired;
          if (ExtractDestinations(script, type, vDest, nRequired)) {
              BOOST_FOREACH(const CTxDestination &dest, vDest)
                  boost::apply_visitor(*this, dest);
          }
      }
  
      void operator()(const CKeyID &keyId) {
          if (keystore.HaveKey(keyId))
              vKeys.push_back(keyId);
      }
  
      void operator()(const CScriptID &scriptId) {
          CScript script;
          if (keystore.GetCScript(scriptId, script))
              Process(script);
      }
  
      void operator()(const CNoDestination &none) {}
  };
  
  void ExtractAffectedKeys(const CKeyStore &keystore, const CScript& scriptPubKey, std::vector<CKeyID> &vKeys) {
      CAffectedKeysVisitor(keystore, vKeys).Process(scriptPubKey);
  }
  
  bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, const CTransaction& txTo, unsigned int nIn,
                    unsigned int flags, int nHashType)
  {
      vector<vector<unsigned char> > stack, stackCopy;
      if (!EvalScript(stack, scriptSig, txTo, nIn, flags, nHashType))
          return false;
      if (flags & SCRIPT_VERIFY_P2SH)
          stackCopy = stack;
      if (!EvalScript(stack, scriptPubKey, txTo, nIn, flags, nHashType))
          return false;
      if (stack.empty())
          return false;
  
      if (CastToBool(stack.back()) == false)
          return false;
  
      // Additional validation for spend-to-script-hash transactions:
      if ((flags & SCRIPT_VERIFY_P2SH) && scriptPubKey.IsPayToScriptHash())
      {
          if (!scriptSig.IsPushOnly()) // scriptSig must be literals-only
              return false;            // or validation fails
  
          // stackCopy cannot be empty here, because if it was the
          // P2SH  HASH <> EQUAL  scriptPubKey would be evaluated with
          // an empty stack and the EvalScript above would return false.
          assert(!stackCopy.empty());
  
          const valtype& pubKeySerialized = stackCopy.back();
          CScript pubKey2(pubKeySerialized.begin(), pubKeySerialized.end());
          popstack(stackCopy);
  
          if (!EvalScript(stackCopy, pubKey2, txTo, nIn, flags, nHashType))
              return false;
          if (stackCopy.empty())
              return false;
          return CastToBool(stackCopy.back());
      }
  
      return true;
  }
  
  
  bool SignSignature(const CKeyStore &keystore, const CScript& fromPubKey, CTransaction& txTo, unsigned int nIn, int nHashType)
  {
      assert(nIn < txTo.vin.size());
      CTxIn& txin = txTo.vin[nIn];
  
      // Leave out the signature from the hash, since a signature can't sign itself.
      // The checksig op will also drop the signatures from its hash.
      uint256 hash = SignatureHash(fromPubKey, txTo, nIn, nHashType);
  
      txnouttype whichType;
      if (!Solver(keystore, fromPubKey, hash, nHashType, txin.scriptSig, whichType))
          return false;
  
      if (whichType == TX_SCRIPTHASH)
      {
          // Solver returns the subscript that need to be evaluated;
          // the final scriptSig is the signatures from that
          // and then the serialized subscript:
          CScript subscript = txin.scriptSig;
  
          // Recompute txn hash using subscript in place of scriptPubKey:
          uint256 hash2 = SignatureHash(subscript, txTo, nIn, nHashType);
  
          txnouttype subType;
          bool fSolved =
              Solver(keystore, subscript, hash2, nHashType, txin.scriptSig, subType) && subType != TX_SCRIPTHASH;
          // Append serialized subscript whether or not it is completely signed:
          txin.scriptSig << static_cast<valtype>(subscript);
          if (!fSolved) return false;
      }
  
      // Test solution
      return VerifyScript(txin.scriptSig, fromPubKey, txTo, nIn, SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_STRICTENC, 0);
  }
  
  bool SignSignature(const CKeyStore &keystore, const CTransaction& txFrom, CTransaction& txTo, unsigned int nIn, int nHashType)
  {
      assert(nIn < txTo.vin.size());
      CTxIn& txin = txTo.vin[nIn];
      assert(txin.prevout.n < txFrom.vout.size());
      const CTxOut& txout = txFrom.vout[txin.prevout.n];
  
      return SignSignature(keystore, txout.scriptPubKey, txTo, nIn, nHashType);
  }
  
  static CScript PushAll(const vector<valtype>& values)
  {
      CScript result;
      BOOST_FOREACH(const valtype& v, values)
          result << v;
      return result;
  }
  
  static CScript CombineMultisig(CScript scriptPubKey, const CTransaction& txTo, unsigned int nIn,
                                 const vector<valtype>& vSolutions,
                                 vector<valtype>& sigs1, vector<valtype>& sigs2)
  {
      // Combine all the signatures we've got:
      set<valtype> allsigs;
      BOOST_FOREACH(const valtype& v, sigs1)
      {
          if (!v.empty())
              allsigs.insert(v);
      }
      BOOST_FOREACH(const valtype& v, sigs2)
      {
          if (!v.empty())
              allsigs.insert(v);
      }
  
      // Build a map of pubkey -> signature by matching sigs to pubkeys:
      assert(vSolutions.size() > 1);
      unsigned int nSigsRequired = vSolutions.front()[0];
      unsigned int nPubKeys = vSolutions.size()-2;
      map<valtype, valtype> sigs;
      BOOST_FOREACH(const valtype& sig, allsigs)
      {
          for (unsigned int i = 0; i < nPubKeys; i++)
          {
              const valtype& pubkey = vSolutions[i+1];
              if (sigs.count(pubkey))
                  continue; // Already got a sig for this pubkey
  
              if (CheckSig(sig, pubkey, scriptPubKey, txTo, nIn, 0, 0))
              {
                  sigs[pubkey] = sig;
                  break;
              }
          }
      }
      // Now build a merged CScript:
      unsigned int nSigsHave = 0;
      CScript result; result << OP_0; // pop-one-too-many workaround
      for (unsigned int i = 0; i < nPubKeys && nSigsHave < nSigsRequired; i++)
      {
          if (sigs.count(vSolutions[i+1]))
          {
              result << sigs[vSolutions[i+1]];
              ++nSigsHave;
          }
      }
      // Fill any missing with OP_0:
      for (unsigned int i = nSigsHave; i < nSigsRequired; i++)
          result << OP_0;
  
      return result;
  }
  
  static CScript CombineSignatures(CScript scriptPubKey, const CTransaction& txTo, unsigned int nIn,
                                   const txnouttype txType, const vector<valtype>& vSolutions,
                                   vector<valtype>& sigs1, vector<valtype>& sigs2)
  {
      switch (txType)
      {
      case TX_NONSTANDARD:
          // Don't know anything about this, assume bigger one is correct:
          if (sigs1.size() >= sigs2.size())
              return PushAll(sigs1);
          return PushAll(sigs2);
      case TX_PUBKEY:
      case TX_PUBKEYHASH:
          // Signatures are bigger than placeholders or empty scripts:
          if (sigs1.empty() || sigs1[0].empty())
              return PushAll(sigs2);
          return PushAll(sigs1);
      case TX_SCRIPTHASH:
          if (sigs1.empty() || sigs1.back().empty())
              return PushAll(sigs2);
          else if (sigs2.empty() || sigs2.back().empty())
              return PushAll(sigs1);
          else
          {
              // Recur to combine:
              valtype spk = sigs1.back();
              CScript pubKey2(spk.begin(), spk.end());
  
              txnouttype txType2;
              vector<vector<unsigned char> > vSolutions2;
              Solver(pubKey2, txType2, vSolutions2);
              sigs1.pop_back();
              sigs2.pop_back();
              CScript result = CombineSignatures(pubKey2, txTo, nIn, txType2, vSolutions2, sigs1, sigs2);
              result << spk;
              return result;
          }
      case TX_MULTISIG:
          return CombineMultisig(scriptPubKey, txTo, nIn, vSolutions, sigs1, sigs2);
      }
  
      return CScript();
  }
  
  CScript CombineSignatures(CScript scriptPubKey, const CTransaction& txTo, unsigned int nIn,
                            const CScript& scriptSig1, const CScript& scriptSig2)
  {
      txnouttype txType;
      vector<vector<unsigned char> > vSolutions;
      Solver(scriptPubKey, txType, vSolutions);
  
      vector<valtype> stack1;
      EvalScript(stack1, scriptSig1, CTransaction(), 0, SCRIPT_VERIFY_STRICTENC, 0);
      vector<valtype> stack2;
      EvalScript(stack2, scriptSig2, CTransaction(), 0, SCRIPT_VERIFY_STRICTENC, 0);
  
      return CombineSignatures(scriptPubKey, txTo, nIn, txType, vSolutions, stack1, stack2);
  }
  
  unsigned int CScript::GetSigOpCount(bool fAccurate) const
  {
      unsigned int n = 0;
      const_iterator pc = begin();
      opcodetype lastOpcode = OP_INVALIDOPCODE;
      while (pc < end())
      {
          opcodetype opcode;
          if (!GetOp(pc, opcode))
              break;
          if (opcode == OP_CHECKSIG || opcode == OP_CHECKSIGVERIFY)
              n++;
          else if (opcode == OP_CHECKMULTISIG || opcode == OP_CHECKMULTISIGVERIFY)
          {
              if (fAccurate && lastOpcode >= OP_1 && lastOpcode <= OP_16)
                  n += DecodeOP_N(lastOpcode);
              else
                  n += 20;
          }
          lastOpcode = opcode;
      }
      return n;
  }
  
  unsigned int CScript::GetSigOpCount(const CScript& scriptSig) const
  {
      if (!IsPayToScriptHash())
          return GetSigOpCount(true);
  
      // This is a pay-to-script-hash scriptPubKey;
      // get the last item that the scriptSig
      // pushes onto the stack:
      const_iterator pc = scriptSig.begin();
      vector<unsigned char> data;
      while (pc < scriptSig.end())
      {
          opcodetype opcode;
          if (!scriptSig.GetOp(pc, opcode, data))
              return 0;
          if (opcode > OP_16)
              return 0;
      }
  
      /// ... and return its opcount:
      CScript subscript(data.begin(), data.end());
      return subscript.GetSigOpCount(true);
  }
  
  bool CScript::IsPayToScriptHash() const
  {
      // Extra-fast test for pay-to-script-hash CScripts:
      return (this->size() == 23 &&
              this->at(0) == OP_HASH160 &&
              this->at(1) == 0x14 &&
              this->at(22) == OP_EQUAL);
  }
  
  class CScriptVisitor : public boost::static_visitor<bool>
  {
  private:
      CScript *script;
  public:
      CScriptVisitor(CScript *scriptin) { script = scriptin; }
  
      bool operator()(const CNoDestination &dest) const {
          script->clear();
          return false;
      }
  
      bool operator()(const CKeyID &keyID) const {
          script->clear();
          *script << OP_DUP << OP_HASH160 << keyID << OP_EQUALVERIFY << OP_CHECKSIG;
          return true;
      }
  
      bool operator()(const CScriptID &scriptID) const {
          script->clear();
          *script << OP_HASH160 << scriptID << OP_EQUAL;
          return true;
      }
  };
  
  void CScript::SetDestination(const CTxDestination& dest)
  {
      boost::apply_visitor(CScriptVisitor(this), dest);
  }
  
  void CScript::SetMultisig(int nRequired, const std::vector<CPubKey>& keys)
  {
      this->clear();
  
      *this << EncodeOP_N(nRequired);
      BOOST_FOREACH(const CPubKey& key, keys)
          *this << key;
      *this << EncodeOP_N(keys.size()) << OP_CHECKMULTISIG;
  }
  
  bool CScriptCompressor::IsToKeyID(CKeyID &hash) const
  {
      if (script.size() == 25 && script[0] == OP_DUP && script[1] == OP_HASH160 
                              && script[2] == 20 && script[23] == OP_EQUALVERIFY
                              && script[24] == OP_CHECKSIG) {
          memcpy(&hash, &script[3], 20);
          return true;
      }
      return false;
  }
  
  bool CScriptCompressor::IsToScriptID(CScriptID &hash) const
  {
      if (script.size() == 23 && script[0] == OP_HASH160 && script[1] == 20
                              && script[22] == OP_EQUAL) {
          memcpy(&hash, &script[2], 20);
          return true;
      }
      return false;
  }
  
  bool CScriptCompressor::IsToPubKey(CPubKey &pubkey) const
  {
      if (script.size() == 35 && script[0] == 33 && script[34] == OP_CHECKSIG
                              && (script[1] == 0x02 || script[1] == 0x03)) {
          pubkey.Set(&script[1], &script[34]);
          return true;
      }
      if (script.size() == 67 && script[0] == 65 && script[66] == OP_CHECKSIG
                              && script[1] == 0x04) {
          pubkey.Set(&script[1], &script[66]);
          return pubkey.IsFullyValid(); // if not fully valid, a case that would not be compressible
      }
      return false;
  }
  
  bool CScriptCompressor::Compress(std::vector<unsigned char> &out) const
  {
      CKeyID keyID;
      if (IsToKeyID(keyID)) {
          out.resize(21);
          out[0] = 0x00;
          memcpy(&out[1], &keyID, 20);
          return true;
      }
      CScriptID scriptID;
      if (IsToScriptID(scriptID)) {
          out.resize(21);
          out[0] = 0x01;
          memcpy(&out[1], &scriptID, 20);
          return true;
      }
      CPubKey pubkey;
      if (IsToPubKey(pubkey)) {
          out.resize(33);
          memcpy(&out[1], &pubkey[1], 32);
          if (pubkey[0] == 0x02 || pubkey[0] == 0x03) {
              out[0] = pubkey[0];
              return true;
          } else if (pubkey[0] == 0x04) {
              out[0] = 0x04 | (pubkey[64] & 0x01);
              return true;
          }
      }
      return false;
  }
  
  unsigned int CScriptCompressor::GetSpecialSize(unsigned int nSize) const
  {
      if (nSize == 0 || nSize == 1)
          return 20;
      if (nSize == 2 || nSize == 3 || nSize == 4 || nSize == 5)
          return 32;
      return 0;
  }
  
  bool CScriptCompressor::Decompress(unsigned int nSize, const std::vector<unsigned char> &in)
  {
      switch(nSize) {
      case 0x00:
          script.resize(25);
          script[0] = OP_DUP;
          script[1] = OP_HASH160;
          script[2] = 20;
          memcpy(&script[3], &in[0], 20);
          script[23] = OP_EQUALVERIFY;
          script[24] = OP_CHECKSIG;
          return true;
      case 0x01:
          script.resize(23);
          script[0] = OP_HASH160;
          script[1] = 20;
          memcpy(&script[2], &in[0], 20);
          script[22] = OP_EQUAL;
          return true;
      case 0x02:
      case 0x03:
          script.resize(35);
          script[0] = 33;
          script[1] = nSize;
          memcpy(&script[2], &in[0], 32);
          script[34] = OP_CHECKSIG;
          return true;
      case 0x04:
      case 0x05:
          unsigned char vch[33] = {};
          vch[0] = nSize - 2;
          memcpy(&vch[1], &in[0], 32);
          CPubKey pubkey(&vch[0], &vch[33]);
          if (!pubkey.Decompress())
              return false;
          assert(pubkey.size() == 65);
          script.resize(67);
          script[0] = 65;
          memcpy(&script[1], pubkey.begin(), 65);
          script[66] = OP_CHECKSIG;
          return true;
      }
      return false;
  }
  