src/script/script.h

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2016 The Bitcoin Core developers
   3 // Distributed under the MIT software license, see the accompanying
   4 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   5
   6 #ifndef BITCOIN_SCRIPT_SCRIPT_H
   7 #define BITCOIN_SCRIPT_SCRIPT_H
   8
   9 #include "crypto/common.h"
  10 #include "prevector.h"
  11
  12 #include <assert.h>
  13 #include <climits>
  14 #include <limits>
  15 #include <stdexcept>
  16 #include <stdint.h>
  17 #include <string.h>
  18 #include <string>
  19 #include <vector>
  20
  21 // Maximum number of bytes pushable to the stack
  22 static const unsigned int MAX_SCRIPT_ELEMENT_SIZE = 520;
  23
  24 // Maximum number of non-push operations per script
  25 static const int MAX_OPS_PER_SCRIPT = 201;
  26
  27 // Maximum number of public keys per multisig
  28 static const int MAX_PUBKEYS_PER_MULTISIG = 20;
  29
  30 // Maximum script length in bytes
  31 static const int MAX_SCRIPT_SIZE = 10000;
  32
  33 // Maximum number of values on script interpreter stack
  34 static const int MAX_STACK_SIZE = 1000;
  35
  36 // Threshold for nLockTime: below this value it is interpreted as block number,
  37 // otherwise as UNIX timestamp.
  38 static const unsigned int LOCKTIME_THRESHOLD = 500000000; // Tue Nov  5 00:53:20 1985 UTC
  39
  40 template <typename T>
  41 std::vector<unsigned char> ToByteVector(const T& in)
  42 {
  43     return std::vector<unsigned char>(in.begin(), in.end());
  44 }
  45
  46 /** Script opcodes */
  47 enum opcodetype
  48 {
  49     // push value
  50     OP_0 = 0x00,
  51     OP_FALSE = OP_0,
  52     OP_PUSHDATA1 = 0x4c,
  53     OP_PUSHDATA2 = 0x4d,
  54     OP_PUSHDATA4 = 0x4e,
  55     OP_1NEGATE = 0x4f,
  56     OP_RESERVED = 0x50,
  57     OP_1 = 0x51,
  58     OP_TRUE=OP_1,
  59     OP_2 = 0x52,
  60     OP_3 = 0x53,
  61     OP_4 = 0x54,
  62     OP_5 = 0x55,
  63     OP_6 = 0x56,
  64     OP_7 = 0x57,
  65     OP_8 = 0x58,
  66     OP_9 = 0x59,
  67     OP_10 = 0x5a,
  68     OP_11 = 0x5b,
  69     OP_12 = 0x5c,
  70     OP_13 = 0x5d,
  71     OP_14 = 0x5e,
  72     OP_15 = 0x5f,
  73     OP_16 = 0x60,
  74
  75     // control
  76     OP_NOP = 0x61,
  77     OP_VER = 0x62,
  78     OP_IF = 0x63,
  79     OP_NOTIF = 0x64,
  80     OP_VERIF = 0x65,
  81     OP_VERNOTIF = 0x66,
  82     OP_ELSE = 0x67,
  83     OP_ENDIF = 0x68,
  84     OP_VERIFY = 0x69,
  85     OP_RETURN = 0x6a,
  86
  87     // stack ops
  88     OP_TOALTSTACK = 0x6b,
  89     OP_FROMALTSTACK = 0x6c,
  90     OP_2DROP = 0x6d,
  91     OP_2DUP = 0x6e,
  92     OP_3DUP = 0x6f,
  93     OP_2OVER = 0x70,
  94     OP_2ROT = 0x71,
  95     OP_2SWAP = 0x72,
  96     OP_IFDUP = 0x73,
  97     OP_DEPTH = 0x74,
  98     OP_DROP = 0x75,
  99     OP_DUP = 0x76,
 100     OP_NIP = 0x77,
 101     OP_OVER = 0x78,
 102     OP_PICK = 0x79,
 103     OP_ROLL = 0x7a,
 104     OP_ROT = 0x7b,
 105     OP_SWAP = 0x7c,
 106     OP_TUCK = 0x7d,
 107
 108     // splice ops
 109     OP_CAT = 0x7e,
 110     OP_SUBSTR = 0x7f,
 111     OP_LEFT = 0x80,
 112     OP_RIGHT = 0x81,
 113     OP_SIZE = 0x82,
 114
 115     // bit logic
 116     OP_INVERT = 0x83,
 117     OP_AND = 0x84,
 118     OP_OR = 0x85,
 119     OP_XOR = 0x86,
 120     OP_EQUAL = 0x87,
 121     OP_EQUALVERIFY = 0x88,
 122     OP_RESERVED1 = 0x89,
 123     OP_RESERVED2 = 0x8a,
 124
 125     // numeric
 126     OP_1ADD = 0x8b,
 127     OP_1SUB = 0x8c,
 128     OP_2MUL = 0x8d,
 129     OP_2DIV = 0x8e,
 130     OP_NEGATE = 0x8f,
 131     OP_ABS = 0x90,
 132     OP_NOT = 0x91,
 133     OP_0NOTEQUAL = 0x92,
 134
 135     OP_ADD = 0x93,
 136     OP_SUB = 0x94,
 137     OP_MUL = 0x95,
 138     OP_DIV = 0x96,
 139     OP_MOD = 0x97,
 140     OP_LSHIFT = 0x98,
 141     OP_RSHIFT = 0x99,
 142
 143     OP_BOOLAND = 0x9a,
 144     OP_BOOLOR = 0x9b,
 145     OP_NUMEQUAL = 0x9c,
 146     OP_NUMEQUALVERIFY = 0x9d,
 147     OP_NUMNOTEQUAL = 0x9e,
 148     OP_LESSTHAN = 0x9f,
 149     OP_GREATERTHAN = 0xa0,
 150     OP_LESSTHANOREQUAL = 0xa1,
 151     OP_GREATERTHANOREQUAL = 0xa2,
 152     OP_MIN = 0xa3,
 153     OP_MAX = 0xa4,
 154
 155     OP_WITHIN = 0xa5,
 156
 157     // crypto
 158     OP_RIPEMD160 = 0xa6,
 159     OP_SHA1 = 0xa7,
 160     OP_SHA256 = 0xa8,
 161     OP_HASH160 = 0xa9,
 162     OP_HASH256 = 0xaa,
 163     OP_CODESEPARATOR = 0xab,
 164     OP_CHECKSIG = 0xac,
 165     OP_CHECKSIGVERIFY = 0xad,
 166     OP_CHECKMULTISIG = 0xae,
 167     OP_CHECKMULTISIGVERIFY = 0xaf,
 168
 169     // expansion
 170     OP_NOP1 = 0xb0,
 171     OP_CHECKLOCKTIMEVERIFY = 0xb1,
 172     OP_NOP2 = OP_CHECKLOCKTIMEVERIFY,
 173     OP_CHECKSEQUENCEVERIFY = 0xb2,
 174     OP_NOP3 = OP_CHECKSEQUENCEVERIFY,
 175     OP_NOP4 = 0xb3,
 176     OP_NOP5 = 0xb4,
 177     OP_NOP6 = 0xb5,
 178     OP_NOP7 = 0xb6,
 179     OP_NOP8 = 0xb7,
 180     OP_NOP9 = 0xb8,
 181     OP_NOP10 = 0xb9,
 182
 183
 184     // template matching params
 185     OP_SMALLINTEGER = 0xfa,
 186     OP_PUBKEYS = 0xfb,
 187     OP_PUBKEYHASH = 0xfd,
 188     OP_PUBKEY = 0xfe,
 189
 190     OP_INVALIDOPCODE = 0xff,
 191 };
 192
 193 const char* GetOpName(opcodetype opcode);
 194
 195 class scriptnum_error : public std::runtime_error
 196 {
 197 public:
 198     explicit scriptnum_error(const std::string& str) : std::runtime_error(str) {}
 199 };
 200
 201 class CScriptNum
 202 {
 203 /**
 204  * Numeric opcodes (OP_1ADD, etc) are restricted to operating on 4-byte integers.
 205  * The semantics are subtle, though: operands must be in the range [-2^31 +1...2^31 -1],
 206  * but results may overflow (and are valid as long as they are not used in a subsequent
 207  * numeric operation). CScriptNum enforces those semantics by storing results as
 208  * an int64 and allowing out-of-range values to be returned as a vector of bytes but
 209  * throwing an exception if arithmetic is done or the result is interpreted as an integer.
 210  */
 211 public:
 212
 213     explicit CScriptNum(const int64_t& n)
 214     {
 215         m_value = n;
 216     }
 217
 218     static const size_t nDefaultMaxNumSize = 4;
 219
 220     explicit CScriptNum(const std::vector<unsigned char>& vch, bool fRequireMinimal,
 221                         const size_t nMaxNumSize = nDefaultMaxNumSize)
 222     {
 223         if (vch.size() > nMaxNumSize) {
 224             throw scriptnum_error("script number overflow");
 225         }
 226         if (fRequireMinimal && vch.size() > 0) {
 227             // Check that the number is encoded with the minimum possible
 228             // number of bytes.
 229             //
 230             // If the most-significant-byte - excluding the sign bit - is zero
 231             // then we're not minimal. Note how this test also rejects the
 232             // negative-zero encoding, 0x80.
 233             if ((vch.back() & 0x7f) == 0) {
 234                 // One exception: if there's more than one byte and the most
 235                 // significant bit of the second-most-significant-byte is set
 236                 // it would conflict with the sign bit. An example of this case
 237                 // is +-255, which encode to 0xff00 and 0xff80 respectively.
 238                 // (big-endian).
 239                 if (vch.size() <= 1 || (vch[vch.size() - 2] & 0x80) == 0) {
 240                     throw scriptnum_error("non-minimally encoded script number");
 241                 }
 242             }
 243         }
 244         m_value = set_vch(vch);
 245     }
 246
 247     inline bool operator==(const int64_t& rhs) const    { return m_value == rhs; }
 248     inline bool operator!=(const int64_t& rhs) const    { return m_value != rhs; }
 249     inline bool operator<=(const int64_t& rhs) const    { return m_value <= rhs; }
 250     inline bool operator< (const int64_t& rhs) const    { return m_value <  rhs; }
 251     inline bool operator>=(const int64_t& rhs) const    { return m_value >= rhs; }
 252     inline bool operator> (const int64_t& rhs) const    { return m_value >  rhs; }
 253
 254     inline bool operator==(const CScriptNum& rhs) const { return operator==(rhs.m_value); }
 255     inline bool operator!=(const CScriptNum& rhs) const { return operator!=(rhs.m_value); }
 256     inline bool operator<=(const CScriptNum& rhs) const { return operator<=(rhs.m_value); }
 257     inline bool operator< (const CScriptNum& rhs) const { return operator< (rhs.m_value); }
 258     inline bool operator>=(const CScriptNum& rhs) const { return operator>=(rhs.m_value); }
 259     inline bool operator> (const CScriptNum& rhs) const { return operator> (rhs.m_value); }
 260
 261     inline CScriptNum operator+(   const int64_t& rhs)    const { return CScriptNum(m_value + rhs);}
 262     inline CScriptNum operator-(   const int64_t& rhs)    const { return CScriptNum(m_value - rhs);}
 263     inline CScriptNum operator+(   const CScriptNum& rhs) const { return operator+(rhs.m_value);   }
 264     inline CScriptNum operator-(   const CScriptNum& rhs) const { return operator-(rhs.m_value);   }
 265
 266     inline CScriptNum& operator+=( const CScriptNum& rhs)       { return operator+=(rhs.m_value);  }
 267     inline CScriptNum& operator-=( const CScriptNum& rhs)       { return operator-=(rhs.m_value);  }
 268
 269     inline CScriptNum operator&(   const int64_t& rhs)    const { return CScriptNum(m_value & rhs);}
 270     inline CScriptNum operator&(   const CScriptNum& rhs) const { return operator&(rhs.m_value);   }
 271
 272     inline CScriptNum& operator&=( const CScriptNum& rhs)       { return operator&=(rhs.m_value);  }
 273
 274     inline CScriptNum operator-()                         const
 275     {
 276         assert(m_value != std::numeric_limits<int64_t>::min());
 277         return CScriptNum(-m_value);
 278     }
 279
 280     inline CScriptNum& operator=( const int64_t& rhs)
 281     {
 282         m_value = rhs;
 283         return *this;
 284     }
 285
 286     inline CScriptNum& operator+=( const int64_t& rhs)
 287     {
 288         assert(rhs == 0 || (rhs > 0 && m_value <= std::numeric_limits<int64_t>::max() - rhs) ||
 289                            (rhs < 0 && m_value >= std::numeric_limits<int64_t>::min() - rhs));
 290         m_value += rhs;
 291         return *this;
 292     }
 293
 294     inline CScriptNum& operator-=( const int64_t& rhs)
 295     {
 296         assert(rhs == 0 || (rhs > 0 && m_value >= std::numeric_limits<int64_t>::min() + rhs) ||
 297                            (rhs < 0 && m_value <= std::numeric_limits<int64_t>::max() + rhs));
 298         m_value -= rhs;
 299         return *this;
 300     }
 301
 302     inline CScriptNum& operator&=( const int64_t& rhs)
 303     {
 304         m_value &= rhs;
 305         return *this;
 306     }
 307
 308     int getint() const
 309     {
 310         if (m_value > std::numeric_limits<int>::max())
 311             return std::numeric_limits<int>::max();
 312         else if (m_value < std::numeric_limits<int>::min())
 313             return std::numeric_limits<int>::min();
 314         return m_value;
 315     }
 316
 317     std::vector<unsigned char> getvch() const
 318     {
 319         return serialize(m_value);
 320     }
 321
 322     static std::vector<unsigned char> serialize(const int64_t& value)
 323     {
 324         if(value == 0)
 325             return std::vector<unsigned char>();
 326
 327         std::vector<unsigned char> result;
 328         const bool neg = value < 0;
 329         uint64_t absvalue = neg ? -value : value;
 330
 331         while(absvalue)
 332         {
 333             result.push_back(absvalue & 0xff);
 334             absvalue >>= 8;
 335         }
 336
 337 //    - If the most significant byte is >= 0x80 and the value is positive, push a
 338 //    new zero-byte to make the significant byte < 0x80 again.
 339
 340 //    - If the most significant byte is >= 0x80 and the value is negative, push a
 341 //    new 0x80 byte that will be popped off when converting to an integral.
 342
 343 //    - If the most significant byte is < 0x80 and the value is negative, add
 344 //    0x80 to it, since it will be subtracted and interpreted as a negative when
 345 //    converting to an integral.
 346
 347         if (result.back() & 0x80)
 348             result.push_back(neg ? 0x80 : 0);
 349         else if (neg)
 350             result.back() |= 0x80;
 351
 352         return result;
 353     }
 354
 355 private:
 356     static int64_t set_vch(const std::vector<unsigned char>& vch)
 357     {
 358       if (vch.empty())
 359           return 0;
 360
 361       int64_t result = 0;
 362       for (size_t i = 0; i != vch.size(); ++i)
 363           result |= static_cast<int64_t>(vch[i]) << 8*i;
 364
 365       // If the input vector's most significant byte is 0x80, remove it from
 366       // the result's msb and return a negative.
 367       if (vch.back() & 0x80)
 368           return -((int64_t)(result & ~(0x80ULL << (8 * (vch.size() - 1)))));
 369
 370       return result;
 371     }
 372
 373     int64_t m_value;
 374 };
 375
 376 typedef prevector<28, unsigned char> CScriptBase;
 377
 378 /** Serialized script, used inside transaction inputs and outputs */
 379 class CScript : public CScriptBase
 380 {
 381 protected:
 382     CScript& push_int64(int64_t n)
 383     {
 384         if (n == -1 || (n >= 1 && n <= 16))
 385         {
 386             push_back(n + (OP_1 - 1));
 387         }
 388         else if (n == 0)
 389         {
 390             push_back(OP_0);
 391         }
 392         else
 393         {
 394             *this << CScriptNum::serialize(n);
 395         }
 396         return *this;
 397     }
 398 public:
 399     CScript() { }
 400     CScript(const_iterator pbegin, const_iterator pend) : CScriptBase(pbegin, pend) { }
 401     CScript(std::vector<unsigned char>::const_iterator pbegin, std::vector<unsigned char>::const_iterator pend) : CScriptBase(pbegin, pend) { }
 402     CScript(const unsigned char* pbegin, const unsigned char* pend) : CScriptBase(pbegin, pend) { }
 403
 404     CScript& operator+=(const CScript& b)
 405     {
 406         insert(end(), b.begin(), b.end());
 407         return *this;
 408     }
 409
 410     friend CScript operator+(const CScript& a, const CScript& b)
 411     {
 412         CScript ret = a;
 413         ret += b;
 414         return ret;
 415     }
 416
 417     CScript(int64_t b)        { operator<<(b); }
 418
 419     explicit CScript(opcodetype b)     { operator<<(b); }
 420     explicit CScript(const CScriptNum& b) { operator<<(b); }
 421     explicit CScript(const std::vector<unsigned char>& b) { operator<<(b); }
 422
 423
 424     CScript& operator<<(int64_t b) { return push_int64(b); }
 425
 426     CScript& operator<<(opcodetype opcode)
 427     {
 428         if (opcode < 0 || opcode > 0xff)
 429             throw std::runtime_error("CScript::operator<<(): invalid opcode");
 430         insert(end(), (unsigned char)opcode);
 431         return *this;
 432     }
 433
 434     CScript& operator<<(const CScriptNum& b)
 435     {
 436         *this << b.getvch();
 437         return *this;
 438     }
 439
 440     CScript& operator<<(const std::vector<unsigned char>& b)
 441     {
 442         if (b.size() < OP_PUSHDATA1)
 443         {
 444             insert(end(), (unsigned char)b.size());
 445         }
 446         else if (b.size() <= 0xff)
 447         {
 448             insert(end(), OP_PUSHDATA1);
 449             insert(end(), (unsigned char)b.size());
 450         }
 451         else if (b.size() <= 0xffff)
 452         {
 453             insert(end(), OP_PUSHDATA2);
 454             uint8_t _data[2];
 455             WriteLE16(_data, b.size());
 456             insert(end(), _data, _data + sizeof(_data));
 457         }
 458         else
 459         {
 460             insert(end(), OP_PUSHDATA4);
 461             uint8_t _data[4];
 462             WriteLE32(_data, b.size());
 463             insert(end(), _data, _data + sizeof(_data));
 464         }
 465         insert(end(), b.begin(), b.end());
 466         return *this;
 467     }
 468
 469     CScript& operator<<(const CScript& b)
 470     {
 471         // I'm not sure if this should push the script or concatenate scripts.
 472         // If there's ever a use for pushing a script onto a script, delete this member fn
 473         assert(!"Warning: Pushing a CScript onto a CScript with << is probably not intended, use + to concatenate!");
 474         return *this;
 475     }
 476
 477
 478     bool GetOp(iterator& pc, opcodetype& opcodeRet, std::vector<unsigned char>& vchRet)
 479     {
 480          // Wrapper so it can be called with either iterator or const_iterator
 481          const_iterator pc2 = pc;
 482          bool fRet = GetOp2(pc2, opcodeRet, &vchRet);
 483          pc = begin() + (pc2 - begin());
 484          return fRet;
 485     }
 486
 487     bool GetOp(iterator& pc, opcodetype& opcodeRet)
 488     {
 489          const_iterator pc2 = pc;
 490          bool fRet = GetOp2(pc2, opcodeRet, NULL);
 491          pc = begin() + (pc2 - begin());
 492          return fRet;
 493     }
 494
 495     bool GetOp(const_iterator& pc, opcodetype& opcodeRet, std::vector<unsigned char>& vchRet) const
 496     {
 497         return GetOp2(pc, opcodeRet, &vchRet);
 498     }
 499
 500     bool GetOp(const_iterator& pc, opcodetype& opcodeRet) const
 501     {
 502         return GetOp2(pc, opcodeRet, NULL);
 503     }
 504
 505     bool GetOp2(const_iterator& pc, opcodetype& opcodeRet, std::vector<unsigned char>* pvchRet) const
 506     {
 507         opcodeRet = OP_INVALIDOPCODE;
 508         if (pvchRet)
 509             pvchRet->clear();
 510         if (pc >= end())
 511             return false;
 512
 513         // Read instruction
 514         if (end() - pc < 1)
 515             return false;
 516         unsigned int opcode = *pc++;
 517
 518         // Immediate operand
 519         if (opcode <= OP_PUSHDATA4)
 520         {
 521             unsigned int nSize = 0;
 522             if (opcode < OP_PUSHDATA1)
 523             {
 524                 nSize = opcode;
 525             }
 526             else if (opcode == OP_PUSHDATA1)
 527             {
 528                 if (end() - pc < 1)
 529                     return false;
 530                 nSize = *pc++;
 531             }
 532             else if (opcode == OP_PUSHDATA2)
 533             {
 534                 if (end() - pc < 2)
 535                     return false;
 536                 nSize = ReadLE16(&pc[0]);
 537                 pc += 2;
 538             }
 539             else if (opcode == OP_PUSHDATA4)
 540             {
 541                 if (end() - pc < 4)
 542                     return false;
 543                 nSize = ReadLE32(&pc[0]);
 544                 pc += 4;
 545             }
 546             if (end() - pc < 0 || (unsigned int)(end() - pc) < nSize)
 547                 return false;
 548             if (pvchRet)
 549                 pvchRet->assign(pc, pc + nSize);
 550             pc += nSize;
 551         }
 552
 553         opcodeRet = (opcodetype)opcode;
 554         return true;
 555     }
 556
 557     /** Encode/decode small integers: */
 558     static int DecodeOP_N(opcodetype opcode)
 559     {
 560         if (opcode == OP_0)
 561             return 0;
 562         assert(opcode >= OP_1 && opcode <= OP_16);
 563         return (int)opcode - (int)(OP_1 - 1);
 564     }
 565     static opcodetype EncodeOP_N(int n)
 566     {
 567         assert(n >= 0 && n <= 16);
 568         if (n == 0)
 569             return OP_0;
 570         return (opcodetype)(OP_1+n-1);
 571     }
 572
 573     int FindAndDelete(const CScript& b)
 574     {
 575         int nFound = 0;
 576         if (b.empty())
 577             return nFound;
 578         CScript result;
 579         iterator pc = begin(), pc2 = begin();
 580         opcodetype opcode;
 581         do
 582         {
 583             result.insert(result.end(), pc2, pc);
 584             while (static_cast<size_t>(end() - pc) >= b.size() && std::equal(b.begin(), b.end(), pc))
 585             {
 586                 pc = pc + b.size();
 587                 ++nFound;
 588             }
 589             pc2 = pc;
 590         }
 591         while (GetOp(pc, opcode));
 592
 593         if (nFound > 0) {
 594             result.insert(result.end(), pc2, end());
 595             *this = result;
 596         }
 597
 598         return nFound;
 599     }
 600     int Find(opcodetype op) const
 601     {
 602         int nFound = 0;
 603         opcodetype opcode;
 604         for (const_iterator pc = begin(); pc != end() && GetOp(pc, opcode);)
 605             if (opcode == op)
 606                 ++nFound;
 607         return nFound;
 608     }
 609
 610     /**
 611      * Pre-version-0.6, Bitcoin always counted CHECKMULTISIGs
 612      * as 20 sigops. With pay-to-script-hash, that changed:
 613      * CHECKMULTISIGs serialized in scriptSigs are
 614      * counted more accurately, assuming they are of the form
 615      *  ... OP_N CHECKMULTISIG ...
 616      */
 617     unsigned int GetSigOpCount(bool fAccurate) const;
 618
 619     /**
 620      * Accurately count sigOps, including sigOps in
 621      * pay-to-script-hash transactions:
 622      */
 623     unsigned int GetSigOpCount(const CScript& scriptSig) const;
 624
 625     bool IsPayToScriptHash() const;
 626     bool IsPayToWitnessScriptHash() const;
 627     bool IsWitnessProgram(int& version, std::vector<unsigned char>& program) const;
 628
 629     /** Called by IsStandardTx and P2SH/BIP62 VerifyScript (which makes it consensus-critical). */
 630     bool IsPushOnly(const_iterator pc) const;
 631     bool IsPushOnly() const;
 632
 633     /**
 634      * Returns whether the script is guaranteed to fail at execution,
 635      * regardless of the initial stack. This allows outputs to be pruned
 636      * instantly when entering the UTXO set.
 637      */
 638     bool IsUnspendable() const
 639     {
 640         return (size() > 0 && *begin() == OP_RETURN) || (size() > MAX_SCRIPT_SIZE);
 641     }
 642
 643     void clear()
 644     {
 645         // The default std::vector::clear() does not release memory.
 646         CScriptBase().swap(*this);
 647     }
 648 };
 649
 650 struct CScriptWitness
 651 {
 652     // Note that this encodes the data elements being pushed, rather than
 653     // encoding them as a CScript that pushes them.
 654     std::vector<std::vector<unsigned char> > stack;
 655
 656     // Some compilers complain without a default constructor
 657     CScriptWitness() { }
 658
 659     bool IsNull() const { return stack.empty(); }
 660
 661     void SetNull() { stack.clear(); stack.shrink_to_fit(); }
 662
 663     std::string ToString() const;
 664 };
 665
 666 class CReserveScript
 667 {
 668 public:
 669     CScript reserveScript;
 670     virtual void KeepScript() {}
 671     CReserveScript() {}
 672     virtual ~CReserveScript() {}
 673 };
 674
 675 #endif // BITCOIN_SCRIPT_SCRIPT_H