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.
  
  #ifndef H_BITCOIN_SCRIPT
  #define H_BITCOIN_SCRIPT
  
  #include <string>
  #include <vector>
  
  #include <stdint.h>
  
  #include <boost/foreach.hpp>
  #include <boost/variant.hpp>
  
  #include "keystore.h"
  #include "bignum.h"
  #include "util.h"
  #include "stealth.h"
  
  typedef std::vector<unsigned char> valtype;
  
  class CKeyStore;
  class CTransaction;
  
  class BaseSignatureChecker;
  
  static const unsigned int MAX_SCRIPT_ELEMENT_SIZE = 520; // bytes
  static const unsigned int MAX_OP_RETURN_RELAY = 40;      // bytes
  
  template <typename T>
  std::vector<unsigned char> ToByteVector(const T& in)
  {
      return std::vector<unsigned char>(in.begin(), in.end());
  }
  
  typedef enum ScriptError_t
  {
      SCRIPT_ERR_OK = 0,
      SCRIPT_ERR_UNKNOWN_ERROR,
      SCRIPT_ERR_EVAL_FALSE,
      SCRIPT_ERR_OP_RETURN,
  
      /* Max sizes */
      SCRIPT_ERR_SCRIPT_SIZE,
      SCRIPT_ERR_PUSH_SIZE,
      SCRIPT_ERR_OP_COUNT,
      SCRIPT_ERR_STACK_SIZE,
      SCRIPT_ERR_SIG_COUNT,
      SCRIPT_ERR_PUBKEY_COUNT,
  
      /* Failed verify operations */
      SCRIPT_ERR_VERIFY,
      SCRIPT_ERR_EQUALVERIFY,
      SCRIPT_ERR_CHECKMULTISIGVERIFY,
      SCRIPT_ERR_CHECKSIGVERIFY,
      SCRIPT_ERR_NUMEQUALVERIFY,
  
      /* Logical/Format/Canonical errors */
      SCRIPT_ERR_BAD_OPCODE,
      SCRIPT_ERR_DISABLED_OPCODE,
      SCRIPT_ERR_INVALID_STACK_OPERATION,
      SCRIPT_ERR_INVALID_ALTSTACK_OPERATION,
      SCRIPT_ERR_UNBALANCED_CONDITIONAL,
  
      /* BIP62 */
      SCRIPT_ERR_SIG_HASHTYPE,
      SCRIPT_ERR_SIG_DER,
      SCRIPT_ERR_MINIMALDATA,
      SCRIPT_ERR_SIG_PUSHONLY,
      SCRIPT_ERR_SIG_HIGH_S,
      SCRIPT_ERR_SIG_NULLDUMMY,
      SCRIPT_ERR_PUBKEYTYPE,
  
      /* softfork safeness */
      SCRIPT_ERR_DISCOURAGE_UPGRADABLE_NOPS,
  
      SCRIPT_ERR_ERROR_COUNT
  } ScriptError;
  
  #define SCRIPT_ERR_LAST SCRIPT_ERR_ERROR_COUNT
  
  const char* ScriptErrorString(const ScriptError error);
  
  
  /** Signature hash types/flags */
  enum
  {
      SIGHASH_ALL = 1,
      SIGHASH_NONE = 2,
      SIGHASH_SINGLE = 3,
      SIGHASH_ANYONECANPAY = 0x80,
  };
  
  /** Script verification flags */
  enum
  {
      SCRIPT_VERIFY_NONE      = 0,
      SCRIPT_VERIFY_NOCACHE   = (1U << 0),
      // Evaluate P2SH subscripts (softfork safe, BIP16).
      SCRIPT_VERIFY_P2SH      = (1U << 0),
  
      // Passing a non-strict-DER signature or one with undefined hashtype to a checksig operation causes script failure.
      // Evaluating a pubkey that is not (0x04 + 64 bytes) or (0x02 or 0x03 + 32 bytes) by checksig causes script failure.
      // (softfork safe, but not used or intended as a consensus rule).
      SCRIPT_VERIFY_STRICTENC = (1U << 1),
  
      // Passing a non-strict-DER signature to a checksig operation causes script failure (softfork safe, BIP62 rule 1)
      SCRIPT_VERIFY_DERSIG    = (1U << 2),
  
      // Passing a non-strict-DER signature or one with S > order/2 to a checksig operation causes script failure
      // (softfork safe, BIP62 rule 5).
      SCRIPT_VERIFY_LOW_S     = (1U << 3),
  
      // verify dummy stack item consumed by CHECKMULTISIG is of zero-length (softfork safe, BIP62 rule 7).
      SCRIPT_VERIFY_NULLDUMMY = (1U << 4),
  
      // Using a non-push operator in the scriptSig causes script failure (softfork safe, BIP62 rule 2).
      SCRIPT_VERIFY_SIGPUSHONLY = (1U << 5),
  
      // Require minimal encodings for all push operations (OP_0... OP_16, OP_1NEGATE where possible, direct
      // pushes up to 75 bytes, OP_PUSHDATA up to 255 bytes, OP_PUSHDATA2 for anything larger). Evaluating
      // any other push causes the script to fail (BIP62 rule 3).
      // In addition, whenever a stack element is interpreted as a number, it must be of minimal length (BIP62 rule 4).
      // (softfork safe)
      SCRIPT_VERIFY_MINIMALDATA = (1U << 6),
  
      // Discourage use of NOPs reserved for upgrades (NOP1-10)
      //
      // Provided so that nodes can avoid accepting or mining transactions
      // containing executed NOP's whose meaning may change after a soft-fork,
      // thus rendering the script invalid; with this flag set executing
      // discouraged NOPs fails the script. This verification flag will never be
      // a mandatory flag applied to scripts in a block. NOPs that are not
      // executed, e.g.  within an unexecuted IF ENDIF block, are *not* rejected.
      SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS  = (1U << 7)
  
  };
  
  /** IsMine() return codes */
  enum isminetype
  {
      ISMINE_NO = 0,
      ISMINE_WATCH_ONLY = 1,
      ISMINE_SPENDABLE = 2,
      ISMINE_ALL = ISMINE_WATCH_ONLY | ISMINE_SPENDABLE
  };
  /** used for bitflags of isminetype */
  typedef uint8_t isminefilter;
  
  
  // Mandatory script verification flags that all new blocks must comply with for
  // them to be valid. (but old blocks may not comply with)
  //
  // Failing one of these tests may trigger a DoS ban - see ConnectInputs() for
  // details.
  static const unsigned int MANDATORY_SCRIPT_VERIFY_FLAGS = SCRIPT_VERIFY_NONE;
  
  // Standard script verification flags that standard transactions will comply
  // with. However scripts violating these flags may still be present in valid
  // blocks and we must accept those blocks.
  static const unsigned int STANDARD_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VERIFY_FLAGS |
                                                           SCRIPT_VERIFY_STRICTENC |
                                                           SCRIPT_VERIFY_NULLDUMMY |
                                                           SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS;
  
  // For convenience, standard but not mandatory verify flags.
  static const unsigned int STANDARD_NOT_MANDATORY_VERIFY_FLAGS = STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SCRIPT_VERIFY_FLAGS;
  
  enum txnouttype
  {
      TX_NONSTANDARD,
      // 'standard' transaction types:
      TX_PUBKEY,
      TX_PUBKEYHASH,
      TX_SCRIPTHASH,
      TX_MULTISIG,
      TX_NULL_DATA,
  };
  
  class CNoDestination {
  public:
      friend bool operator==(const CNoDestination &a, const CNoDestination &b) { return true; }
      friend bool operator<(const CNoDestination &a, const CNoDestination &b) { return true; }
  };
  
  /** A txout script template with a specific destination. It is either:
   *  * CNoDestination: no destination set
   *  * CKeyID: TX_PUBKEYHASH destination
   *  * CScriptID: TX_SCRIPTHASH destination
   *  A CTxDestination is the internal data type encoded in a CBuysellAddress
   */
  typedef boost::variant<CNoDestination, CKeyID, CScriptID, CStealthAddress> CTxDestination;
  
  const char* GetTxnOutputType(txnouttype t);
  
  /** Script opcodes */
  enum opcodetype
  {
      // push value
      OP_0 = 0x00,
      OP_FALSE = OP_0,
      OP_PUSHDATA1 = 0x4c,
      OP_PUSHDATA2 = 0x4d,
      OP_PUSHDATA4 = 0x4e,
      OP_1NEGATE = 0x4f,
      OP_RESERVED = 0x50,
      OP_1 = 0x51,
      OP_TRUE=OP_1,
      OP_2 = 0x52,
      OP_3 = 0x53,
      OP_4 = 0x54,
      OP_5 = 0x55,
      OP_6 = 0x56,
      OP_7 = 0x57,
      OP_8 = 0x58,
      OP_9 = 0x59,
      OP_10 = 0x5a,
      OP_11 = 0x5b,
      OP_12 = 0x5c,
      OP_13 = 0x5d,
      OP_14 = 0x5e,
      OP_15 = 0x5f,
      OP_16 = 0x60,
  
      // control
      OP_NOP = 0x61,
      OP_VER = 0x62,
      OP_IF = 0x63,
      OP_NOTIF = 0x64,
      OP_VERIF = 0x65,
      OP_VERNOTIF = 0x66,
      OP_ELSE = 0x67,
      OP_ENDIF = 0x68,
      OP_VERIFY = 0x69,
      OP_RETURN = 0x6a,
  
      // stack ops
      OP_TOALTSTACK = 0x6b,
      OP_FROMALTSTACK = 0x6c,
      OP_2DROP = 0x6d,
      OP_2DUP = 0x6e,
      OP_3DUP = 0x6f,
      OP_2OVER = 0x70,
      OP_2ROT = 0x71,
      OP_2SWAP = 0x72,
      OP_IFDUP = 0x73,
      OP_DEPTH = 0x74,
      OP_DROP = 0x75,
      OP_DUP = 0x76,
      OP_NIP = 0x77,
      OP_OVER = 0x78,
      OP_PICK = 0x79,
      OP_ROLL = 0x7a,
      OP_ROT = 0x7b,
      OP_SWAP = 0x7c,
      OP_TUCK = 0x7d,
  
      // splice ops
      OP_CAT = 0x7e,
      OP_SUBSTR = 0x7f,
      OP_LEFT = 0x80,
      OP_RIGHT = 0x81,
      OP_SIZE = 0x82,
  
      // bit logic
      OP_INVERT = 0x83,
      OP_AND = 0x84,
      OP_OR = 0x85,
      OP_XOR = 0x86,
      OP_EQUAL = 0x87,
      OP_EQUALVERIFY = 0x88,
      OP_RESERVED1 = 0x89,
      OP_RESERVED2 = 0x8a,
  
      // numeric
      OP_1ADD = 0x8b,
      OP_1SUB = 0x8c,
      OP_2MUL = 0x8d,
      OP_2DIV = 0x8e,
      OP_NEGATE = 0x8f,
      OP_ABS = 0x90,
      OP_NOT = 0x91,
      OP_0NOTEQUAL = 0x92,
  
      OP_ADD = 0x93,
      OP_SUB = 0x94,
      OP_MUL = 0x95,
      OP_DIV = 0x96,
      OP_MOD = 0x97,
      OP_LSHIFT = 0x98,
      OP_RSHIFT = 0x99,
  
      OP_BOOLAND = 0x9a,
      OP_BOOLOR = 0x9b,
      OP_NUMEQUAL = 0x9c,
      OP_NUMEQUALVERIFY = 0x9d,
      OP_NUMNOTEQUAL = 0x9e,
      OP_LESSTHAN = 0x9f,
      OP_GREATERTHAN = 0xa0,
      OP_LESSTHANOREQUAL = 0xa1,
      OP_GREATERTHANOREQUAL = 0xa2,
      OP_MIN = 0xa3,
      OP_MAX = 0xa4,
  
      OP_WITHIN = 0xa5,
  
      // crypto
      OP_RIPEMD160 = 0xa6,
      OP_SHA1 = 0xa7,
      OP_SHA256 = 0xa8,
      OP_HASH160 = 0xa9,
      OP_HASH256 = 0xaa,
      OP_CODESEPARATOR = 0xab,
      OP_CHECKSIG = 0xac,
      OP_CHECKSIGVERIFY = 0xad,
      OP_CHECKMULTISIG = 0xae,
      OP_CHECKMULTISIGVERIFY = 0xaf,
  
      // expansion
      OP_NOP1 = 0xb0,
      OP_NOP2 = 0xb1,
      OP_NOP3 = 0xb2,
      OP_NOP4 = 0xb3,
      OP_NOP5 = 0xb4,
      OP_NOP6 = 0xb5,
      OP_NOP7 = 0xb6,
      OP_NOP8 = 0xb7,
      OP_NOP9 = 0xb8,
      OP_NOP10 = 0xb9,
  
  
  
      // template matching params
      OP_SMALLDATA = 0xf9,
      OP_SMALLINTEGER = 0xfa,
      OP_PUBKEYS = 0xfb,
      OP_PUBKEYHASH = 0xfd,
      OP_PUBKEY = 0xfe,
  
      OP_INVALIDOPCODE = 0xff,
  };
  
  const char* GetOpName(opcodetype opcode);
  
  
  
  inline std::string ValueString(const std::vector<unsigned char>& vch)
  {
      if (vch.size() <= 4)
          return strprintf("%d", CBigNum(vch).getint());
      else
          return HexStr(vch);
  }
  
  inline std::string StackString(const std::vector<std::vector<unsigned char> >& vStack)
  {
      std::string str;
      BOOST_FOREACH(const std::vector<unsigned char>& vch, vStack)
      {
          if (!str.empty())
              str += " ";
          str += ValueString(vch);
      }
      return str;
  }
  
  class scriptnum_error : public std::runtime_error
  {
  public:
      explicit scriptnum_error(const std::string& str) : std::runtime_error(str) {}
  };
  
  class CScriptNum
  {
  /**
   * Numeric opcodes (OP_1ADD, etc) are restricted to operating on 4-byte integers.
   * The semantics are subtle, though: operands must be in the range [-2^31 +1...2^31 -1],
   * but results may overflow (and are valid as long as they are not used in a subsequent
   * numeric operation). CScriptNum enforces those semantics by storing results as
   * an int64 and allowing out-of-range values to be returned as a vector of bytes but
   * throwing an exception if arithmetic is done or the result is interpreted as an integer.
   */
  public:
  
      explicit CScriptNum(const int64_t& n)
      {
          m_value = n;
      }
  
      explicit CScriptNum(const std::vector<unsigned char>& vch, bool fRequireMinimal)
      {
          if (vch.size() > nMaxNumSize) {
              throw scriptnum_error("script number overflow");
          }
          if (fRequireMinimal && vch.size() > 0) {
              // Check that the number is encoded with the minimum possible
              // number of bytes.
              //
              // If the most-significant-byte - excluding the sign bit - is zero
              // then we're not minimal. Note how this test also rejects the
              // negative-zero encoding, 0x80.
              if ((vch.back() & 0x7f) == 0) {
                  // One exception: if there's more than one byte and the most
                  // significant bit of the second-most-significant-byte is set
                  // it would conflict with the sign bit. An example of this case
                  // is +-255, which encode to 0xff00 and 0xff80 respectively.
                  // (big-endian).
                  if (vch.size() <= 1 || (vch[vch.size() - 2] & 0x80) == 0) {
                      throw scriptnum_error("non-minimally encoded script number");
                  }
              }
          }
          m_value = set_vch(vch);
      }
  
      inline bool operator==(const int64_t& rhs) const    { return m_value == rhs; }
      inline bool operator!=(const int64_t& rhs) const    { return m_value != rhs; }
      inline bool operator<=(const int64_t& rhs) const    { return m_value <= rhs; }
      inline bool operator< (const int64_t& rhs) const    { return m_value <  rhs; }
      inline bool operator>=(const int64_t& rhs) const    { return m_value >= rhs; }
      inline bool operator> (const int64_t& rhs) const    { return m_value >  rhs; }
  
      inline bool operator==(const CScriptNum& rhs) const { return operator==(rhs.m_value); }
      inline bool operator!=(const CScriptNum& rhs) const { return operator!=(rhs.m_value); }
      inline bool operator<=(const CScriptNum& rhs) const { return operator<=(rhs.m_value); }
      inline bool operator< (const CScriptNum& rhs) const { return operator< (rhs.m_value); }
      inline bool operator>=(const CScriptNum& rhs) const { return operator>=(rhs.m_value); }
      inline bool operator> (const CScriptNum& rhs) const { return operator> (rhs.m_value); }
  
      inline CScriptNum operator+(   const int64_t& rhs)    const { return CScriptNum(m_value + rhs);}
      inline CScriptNum operator-(   const int64_t& rhs)    const { return CScriptNum(m_value - rhs);}
      inline CScriptNum operator+(   const CScriptNum& rhs) const { return operator+(rhs.m_value);   }
      inline CScriptNum operator-(   const CScriptNum& rhs) const { return operator-(rhs.m_value);   }
  
      inline CScriptNum& operator+=( const CScriptNum& rhs)       { return operator+=(rhs.m_value);  }
      inline CScriptNum& operator-=( const CScriptNum& rhs)       { return operator-=(rhs.m_value);  }
  
      inline CScriptNum operator-()                         const
      {
          assert(m_value != std::numeric_limits<int64_t>::min());
          return CScriptNum(-m_value);
      }
  
      inline CScriptNum& operator=( const int64_t& rhs)
      {
          m_value = rhs;
          return *this;
      }
  
      inline CScriptNum& operator+=( const int64_t& rhs)
      {
          assert(rhs == 0 || (rhs > 0 && m_value <= std::numeric_limits<int64_t>::max() - rhs) ||
                             (rhs < 0 && m_value >= std::numeric_limits<int64_t>::min() - rhs));
          m_value += rhs;
          return *this;
      }
  
      inline CScriptNum& operator-=( const int64_t& rhs)
      {
          assert(rhs == 0 || (rhs > 0 && m_value >= std::numeric_limits<int64_t>::min() + rhs) ||
                             (rhs < 0 && m_value <= std::numeric_limits<int64_t>::max() + rhs));
          m_value -= rhs;
          return *this;
      }
  
      int getint() const
      {
          if (m_value > std::numeric_limits<int>::max())
              return std::numeric_limits<int>::max();
          else if (m_value < std::numeric_limits<int>::min())
              return std::numeric_limits<int>::min();
          return m_value;
      }
  
      std::vector<unsigned char> getvch() const
      {
          return serialize(m_value);
      }
  
      static std::vector<unsigned char> serialize(const int64_t& value)
      {
          if(value == 0)
              return std::vector<unsigned char>();
  
          std::vector<unsigned char> result;
          const bool neg = value < 0;
          uint64_t absvalue = neg ? -value : value;
  
          while(absvalue)
          {
              result.push_back(absvalue & 0xff);
              absvalue >>= 8;
          }
  
  //    - If the most significant byte is >= 0x80 and the value is positive, push a
  //    new zero-byte to make the significant byte < 0x80 again.
  
  //    - If the most significant byte is >= 0x80 and the value is negative, push a
  //    new 0x80 byte that will be popped off when converting to an integral.
  
  //    - If the most significant byte is < 0x80 and the value is negative, add
  //    0x80 to it, since it will be subtracted and interpreted as a negative when
  //    converting to an integral.
  
          if (result.back() & 0x80)
              result.push_back(neg ? 0x80 : 0);
          else if (neg)
              result.back() |= 0x80;
  
          return result;
      }
  
      static const size_t nMaxNumSize = 4;
  
  private:
      static int64_t set_vch(const std::vector<unsigned char>& vch)
      {
        if (vch.empty())
            return 0;
  
        int64_t result = 0;
        for (size_t i = 0; i != vch.size(); ++i)
            result |= static_cast<int64_t>(vch[i]) << 8*i;
  
        // If the input vector's most significant byte is 0x80, remove it from
        // the result's msb and return a negative.
        if (vch.back() & 0x80)
            return -((int64_t)(result & ~(0x80ULL << (8 * (vch.size() - 1)))));
  
        return result;
      }
  
      int64_t m_value;
  };
  
  
  
  
  /** Serialized script, used inside transaction inputs and outputs */
  class CScript : public std::vector<unsigned char>
  {
  protected:
      CScript& push_int64(int64_t n)
      {
          if (n == -1 || (n >= 1 && n <= 16))
          {
              push_back(n + (OP_1 - 1));
          }
          else
          {
              CBigNum bn(n);
              *this << bn.getvch();
          }
          return *this;
      }
  
      CScript& push_uint64(uint64_t n)
      {
          if (n >= 1 && n <= 16)
          {
              push_back(n + (OP_1 - 1));
          }
          else
          {
              CBigNum bn(n);
              *this << bn.getvch();
          }
          return *this;
      }
  
  public:
      CScript() { }
      CScript(const CScript& b) : std::vector<unsigned char>(b.begin(), b.end()) { }
      CScript(const_iterator pbegin, const_iterator pend) : std::vector<unsigned char>(pbegin, pend) { }
  #ifndef _MSC_VER
      CScript(const unsigned char* pbegin, const unsigned char* pend) : std::vector<unsigned char>(pbegin, pend) { }
  #endif
  
      CScript& operator+=(const CScript& b)
      {
          insert(end(), b.begin(), b.end());
          return *this;
      }
  
      friend CScript operator+(const CScript& a, const CScript& b)
      {
          CScript ret = a;
          ret += b;
          return ret;
      }
  
  
      //explicit CScript(char b) is not portable.  Use 'signed char' or 'unsigned char'.
      explicit CScript(signed char b)        { operator<<(b); }
      explicit CScript(short b)              { operator<<(b); }
      explicit CScript(int b)                { operator<<(b); }
      explicit CScript(long b)               { operator<<(b); }
      explicit CScript(long long b)          { operator<<(b); }
      explicit CScript(unsigned char b)      { operator<<(b); }
      explicit CScript(unsigned int b)       { operator<<(b); }
      explicit CScript(unsigned short b)     { operator<<(b); }
      explicit CScript(unsigned long b)      { operator<<(b); }
      explicit CScript(unsigned long long b) { operator<<(b); }
  
      explicit CScript(opcodetype b)     { operator<<(b); }
      explicit CScript(const uint256& b) { operator<<(b); }
      explicit CScript(const CBigNum& b) { operator<<(b); }
      explicit CScript(const std::vector<unsigned char>& b) { operator<<(b); }
  
  
      //CScript& operator<<(char b) is not portable.  Use 'signed char' or 'unsigned char'.
      CScript& operator<<(signed char b)        { return push_int64(b); }
      CScript& operator<<(short b)              { return push_int64(b); }
      CScript& operator<<(int b)                { return push_int64(b); }
      CScript& operator<<(long b)               { return push_int64(b); }
      CScript& operator<<(long long b)          { return push_int64(b); }
      CScript& operator<<(unsigned char b)      { return push_uint64(b); }
      CScript& operator<<(unsigned int b)       { return push_uint64(b); }
      CScript& operator<<(unsigned short b)     { return push_uint64(b); }
      CScript& operator<<(unsigned long b)      { return push_uint64(b); }
      CScript& operator<<(unsigned long long b) { return push_uint64(b); }
  
      CScript& operator<<(opcodetype opcode)
      {
          if (opcode < 0 || opcode > 0xff)
              throw std::runtime_error("CScript::operator<<() : invalid opcode");
          insert(end(), (unsigned char)opcode);
          return *this;
      }
  
      CScript& operator<<(const uint160& b)
      {
          insert(end(), sizeof(b));
          insert(end(), (unsigned char*)&b, (unsigned char*)&b + sizeof(b));
          return *this;
      }
  
      CScript& operator<<(const uint256& b)
      {
          insert(end(), sizeof(b));
          insert(end(), (unsigned char*)&b, (unsigned char*)&b + sizeof(b));
          return *this;
      }
  
      CScript& operator<<(const CPubKey& key)
      {
          assert(key.size() < OP_PUSHDATA1);
          insert(end(), (unsigned char)key.size());
          insert(end(), key.begin(), key.end());
          return *this;
      }
  
      CScript& operator<<(const CBigNum& b)
      {
          *this << b.getvch();
          return *this;
      }
  
      CScript& operator<<(const std::vector<unsigned char>& b)
      {
          if (b.size() < OP_PUSHDATA1)
          {
              insert(end(), (unsigned char)b.size());
          }
          else if (b.size() <= 0xff)
          {
              insert(end(), OP_PUSHDATA1);
              insert(end(), (unsigned char)b.size());
          }
          else if (b.size() <= 0xffff)
          {
              insert(end(), OP_PUSHDATA2);
              unsigned short nSize = b.size();
              insert(end(), (unsigned char*)&nSize, (unsigned char*)&nSize + sizeof(nSize));
          }
          else
          {
              insert(end(), OP_PUSHDATA4);
              unsigned int nSize = b.size();
              insert(end(), (unsigned char*)&nSize, (unsigned char*)&nSize + sizeof(nSize));
          }
          insert(end(), b.begin(), b.end());
          return *this;
      }
  
      CScript& operator<<(const CScript& b)
      {
          // I'm not sure if this should push the script or concatenate scripts.
          // If there's ever a use for pushing a script onto a script, delete this member fn
          assert(!"Warning: Pushing a CScript onto a CScript with << is probably not intended, use + to concatenate!");
          return *this;
      }
  
  
      bool GetOp(iterator& pc, opcodetype& opcodeRet, std::vector<unsigned char>& vchRet)
      {
           // Wrapper so it can be called with either iterator or const_iterator
           const_iterator pc2 = pc;
           bool fRet = GetOp2(pc2, opcodeRet, &vchRet);
           pc = begin() + (pc2 - begin());
           return fRet;
      }
  
      bool GetOp(iterator& pc, opcodetype& opcodeRet)
      {
           const_iterator pc2 = pc;
           bool fRet = GetOp2(pc2, opcodeRet, NULL);
           pc = begin() + (pc2 - begin());
           return fRet;
      }
  
      bool GetOp(const_iterator& pc, opcodetype& opcodeRet, std::vector<unsigned char>& vchRet) const
      {
          return GetOp2(pc, opcodeRet, &vchRet);
      }
  
      bool GetOp(const_iterator& pc, opcodetype& opcodeRet) const
      {
          return GetOp2(pc, opcodeRet, NULL);
      }
  
      bool GetOp2(const_iterator& pc, opcodetype& opcodeRet, std::vector<unsigned char>* pvchRet) const
      {
          opcodeRet = OP_INVALIDOPCODE;
          if (pvchRet)
              pvchRet->clear();
          if (pc >= end())
              return false;
  
          // Read instruction
          if (end() - pc < 1)
              return false;
          unsigned int opcode = *pc++;
  
          // Immediate operand
          if (opcode <= OP_PUSHDATA4)
          {
              unsigned int nSize;
              if (opcode < OP_PUSHDATA1)
              {
                  nSize = opcode;
              }
              else if (opcode == OP_PUSHDATA1)
              {
                  if (end() - pc < 1)
                      return false;
                  nSize = *pc++;
              }
              else if (opcode == OP_PUSHDATA2)
              {
                  if (end() - pc < 2)
                      return false;
                  nSize = 0;
                  memcpy(&nSize, &pc[0], 2);
                  pc += 2;
              }
              else if (opcode == OP_PUSHDATA4)
              {
                  if (end() - pc < 4)
                      return false;
                  memcpy(&nSize, &pc[0], 4);
                  pc += 4;
              }
              if (end() - pc < 0 || (unsigned int)(end() - pc) < nSize)
                  return false;
              if (pvchRet)
                  pvchRet->assign(pc, pc + nSize);
              pc += nSize;
          }
  
          opcodeRet = (opcodetype)opcode;
          return true;
      }
  
      // Encode/decode small integers:
      static int DecodeOP_N(opcodetype opcode)
      {
          if (opcode == OP_0)
              return 0;
          assert(opcode >= OP_1 && opcode <= OP_16);
          return (int)opcode - (int)(OP_1 - 1);
      }
      static opcodetype EncodeOP_N(int n)
      {
          assert(n >= 0 && n <= 16);
          if (n == 0)
              return OP_0;
          return (opcodetype)(OP_1+n-1);
      }
  
      int FindAndDelete(const CScript& b)
      {
          int nFound = 0;
          if (b.empty())
              return nFound;
          iterator pc = begin();
          opcodetype opcode;
          do
          {
              while (end() - pc >= (long)b.size() && memcmp(&pc[0], &b[0], b.size()) == 0)
              {
                  erase(pc, pc + b.size());
                  ++nFound;
              }
          }
          while (GetOp(pc, opcode));
          return nFound;
      }
      int Find(opcodetype op) const
      {
          int nFound = 0;
          opcodetype opcode;
          for (const_iterator pc = begin(); pc != end() && GetOp(pc, opcode);)
              if (opcode == op)
                  ++nFound;
          return nFound;
      }
  
      // Pre-version-0.6, Bitcoin always counted CHECKMULTISIGs
      // as 20 sigops. With pay-to-script-hash, that changed:
      // CHECKMULTISIGs serialized in scriptSigs are
      // counted more accurately, assuming they are of the form
      //  ... OP_N CHECKMULTISIG ...
      unsigned int GetSigOpCount(bool fAccurate) const;
  
      // Accurately count sigOps, including sigOps in
      // pay-to-script-hash transactions:
      unsigned int GetSigOpCount(const CScript& scriptSig) const;
      bool IsNormalPaymentScript() const;
      bool IsPayToScriptHash() const;
  
      // Called by IsStandardTx and P2SH VerifyScript (which makes it consensus-critical).
      bool IsPushOnly() const
      {
          const_iterator pc = begin();
          while (pc < end())
          {
              opcodetype opcode;
              if (!GetOp(pc, opcode))
                  return false;
              if (opcode > OP_16)
                  return false;
          }
          return true;
      }
  
      /**
      * Returns whether the script is guaranteed to fail at execution,
      * regardless of the initial stack. This allows outputs to be pruned
      * instantly when entering the UTXO set.
      */
      bool IsUnspendable() const
      {
          return (size() > 0 && *begin() == OP_RETURN);
      }
  
      // Called by IsStandardTx.
      bool HasCanonicalPushes() const;
  
      void SetDestination(const CTxDestination& address);
      void SetMultisig(int nRequired, const std::vector<CPubKey>& keys);
  
      std::string ToString(bool fShort=false) const
      {
          std::string str;
          opcodetype opcode;
          std::vector<unsigned char> vch;
          const_iterator pc = begin();
          while (pc < end())
          {
              if (!str.empty())
                  str += " ";
              if (!GetOp(pc, opcode, vch))
              {
                  str += "[error]";
                  return str;
              }
              if (0 <= opcode && opcode <= OP_PUSHDATA4)
                  str += fShort? ValueString(vch).substr(0, 10) : ValueString(vch);
              else
                  str += GetOpName(opcode);
          }
          return str;
      }
  
      CScriptID GetID() const
      {
          return CScriptID(Hash160(*this));
      }
  
      void clear()
      {
          // The default std::vector::clear() does not release memory.
          std::vector<unsigned char>().swap(*this);
      }
  };
  
  /** Compact serializer for scripts.
   *
   *  It detects common cases and encodes them much more efficiently.
   *  3 special cases are defined:
   *  * Pay to pubkey hash (encoded as 21 bytes)
   *  * Pay to script hash (encoded as 21 bytes)
   *  * Pay to pubkey starting with 0x02, 0x03 or 0x04 (encoded as 33 bytes)
   *
   *  Other scripts up to 121 bytes require 1 byte + script length. Above
   *  that, scripts up to 16505 bytes require 2 bytes + script length.
   */
  class CScriptCompressor
  {
  private:
      // make this static for now (there are only 6 special scripts defined)
      // this can potentially be extended together with a new nVersion for
      // transactions, in which case this value becomes dependent on nVersion
      // and nHeight of the enclosing transaction.
      static const unsigned int nSpecialScripts = 6;
  
      CScript &script;
  protected:
      // These check for scripts for which a special case with a shorter encoding is defined.
      // They are implemented separately from the CScript test, as these test for exact byte
      // sequence correspondences, and are more strict. For example, IsToPubKey also verifies
      // whether the public key is valid (as invalid ones cannot be represented in compressed
      // form).
      bool IsToKeyID(CKeyID &hash) const;
      bool IsToScriptID(CScriptID &hash) const;
      bool IsToPubKey(CPubKey &pubkey) const;
  
      bool Compress(std::vector<unsigned char> &out) const;
      unsigned int GetSpecialSize(unsigned int nSize) const;
      bool Decompress(unsigned int nSize, const std::vector<unsigned char> &out);
  public:
      CScriptCompressor(CScript &scriptIn) : script(scriptIn) { }
  
      unsigned int GetSerializeSize(int nType, int nVersion) const {
          std::vector<unsigned char> compr;
          if (Compress(compr))
              return compr.size();
          unsigned int nSize = script.size() + nSpecialScripts;
          return script.size() + VARINT(nSize).GetSerializeSize(nType, nVersion);
      }
  
      template<typename Stream>
      void Serialize(Stream &s, int nType, int nVersion) const {
          std::vector<unsigned char> compr;
          if (Compress(compr)) {
              s << CFlatData(&compr[0], &compr[compr.size()]);
              return;
          }
          unsigned int nSize = script.size() + nSpecialScripts;
          s << VARINT(nSize);
          s << CFlatData(&script[0], &script[script.size()]);
      }
  
      template<typename Stream>
      void Unserialize(Stream &s, int nType, int nVersion) {
          unsigned int nSize;
          s >> VARINT(nSize);
          if (nSize < nSpecialScripts) {
              std::vector<unsigned char> vch(GetSpecialSize(nSize), 0x00);
              s >> REF(CFlatData(&vch[0], &vch[vch.size()]));
              Decompress(nSize, vch);
              return;
          }
          nSize -= nSpecialScripts;
          script.resize(nSize);
          s >> REF(CFlatData(&script[0], &script[script.size()]));
      }
  };
  
  
  bool IsDERSignature(const valtype &vchSig, bool haveHashType = true);
  bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, const CTransaction& txTo, unsigned int nIn, unsigned int flags, int nHashType);
  bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* error = NULL);
  bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<std::vector<unsigned char> >& vSolutionsRet);
  int ScriptSigArgsExpected(txnouttype t, const std::vector<std::vector<unsigned char> >& vSolutions);
  bool IsStandard(const CScript& scriptPubKey, txnouttype& whichType);
  isminetype IsMine(const CKeyStore& keystore, const CScript& scriptPubKey);
  isminetype IsMine(const CKeyStore& keystore, const CTxDestination& dest);
  void ExtractAffectedKeys(const CKeyStore &keystore, const CScript& scriptPubKey, std::vector<CKeyID> &vKeys);
  bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet);
  bool ExtractDestinations(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<CTxDestination>& addressRet, int& nRequiredRet);
  bool SignSignature(const CKeyStore& keystore, const CScript& fromPubKey, CTransaction& txTo, unsigned int nIn, int nHashType=SIGHASH_ALL);
  bool SignSignature(const CKeyStore& keystore, const CTransaction& txFrom, CTransaction& txTo, unsigned int nIn, int nHashType=SIGHASH_ALL);
  bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, const CTransaction& txTo, unsigned int nIn, unsigned int flags, int nHashType);
  bool VerifySignature(const CTransaction& txFrom, const CTransaction& txTo, unsigned int nIn, unsigned int flags, int nHashType);
  
  bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* error = NULL);
  
  // Given two sets of signatures for scriptPubKey, possibly with OP_0 placeholders,
  // combine them intelligently and return the result.
  CScript CombineSignatures(CScript scriptPubKey, const CTransaction& txTo, unsigned int nIn, const CScript& scriptSig1, const CScript& scriptSig2);
  
  CScript GetScriptForDestination(const CTxDestination& dest);
  CScript GetScriptForMultisig(int nRequired, const std::vector<CPubKey>& keys);
  
  bool Solver(const CKeyStore& keystore, const CScript& scriptPubKey, uint256 hash, int nHashType,
                    CScript& scriptSigRet, txnouttype& whichTypeRet);
  //uint256 SignatureHash(const CScript &scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType);
  
  
  class BaseSignatureChecker
  {
  public:
      virtual bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode) const
      {
          return false;
      }
  
      virtual ~BaseSignatureChecker() {}
  };
  
  class SignatureChecker : public BaseSignatureChecker
  {
  private:
      const CTransaction& txTo;
      unsigned int nIn;
  
  protected:
      virtual bool VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& vchPubKey, const uint256& sighash) const;
  
  public:
      SignatureChecker(const CTransaction& txToIn, unsigned int nInIn) : txTo(txToIn), nIn(nInIn) {}
      bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode) const;
  };
  
  #endif
  