 // Copyright (c) 20092010 Satoshi Nakamoto
 // Copyright (c) 20092017 The Starwels developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mitlicense.php.

 #include <script/interpreter.h>

 #include <crypto/ripemd160.h>
 #include <crypto/sha1.h>
 #include <crypto/sha256.h>
 #include <pubkey.h>
 #include <script/script.h>
 #include <uint256.h>

 typedef std::vector<unsigned char> valtype;

 namespace {

 inline bool set_success(ScriptError* ret)
 {
 if (ret)
 *ret = SCRIPT_ERR_OK;
 return true;
 }

 inline bool set_error(ScriptError* ret, const ScriptError serror)
 {
 if (ret)
 *ret = serror;
 return false;
 }

 } // namespace

 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(std::vector<valtype>& stack)
 {
 if (stack.empty())
 throw std::runtime_error("popstack(): stack empty");
 stack.pop_back();
 }

 bool static IsCompressedOrUncompressedPubKey(const valtype &vchPubKey) {
 if (vchPubKey.size() < 33) {
 // Noncanonical public key: too short
 return false;
 }
 if (vchPubKey[0] == 0x04) {
 if (vchPubKey.size() != 65) {
 // Noncanonical public key: invalid length for uncompressed key
 return false;
 }
 } else if (vchPubKey[0] == 0x02  vchPubKey[0] == 0x03) {
 if (vchPubKey.size() != 33) {
 // Noncanonical public key: invalid length for compressed key
 return false;
 }
 } else {
 // Noncanonical public key: neither compressed nor uncompressed
 return false;
 }
 return true;
 }

 bool static IsCompressedPubKey(const valtype &vchPubKey) {
 if (vchPubKey.size() != 33) {
 // Noncanonical public key: invalid length for compressed key
 return false;
 }
 if (vchPubKey[0] != 0x02 && vchPubKey[0] != 0x03) {
 // Noncanonical public key: invalid prefix for compressed key
 return false;
 }
 return true;
 }

 /**
 * 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).
 *
 * See https://bitcointalk.org/index.php?topic=8392.msg127623#msg127623
 *
 * This function is consensuscritical since BIP66.
 */
 bool static IsValidSignatureEncoding(const std::vector<unsigned char> &sig) {
 // Format: 0x30 [totallength] 0x02 [Rlength] [R] 0x02 [Slength] [S] [sighash]
 // * totallength: 1byte length descriptor of everything that follows,
 // excluding the sighash byte.
 // * Rlength: 1byte length descriptor of the R value that follows.
 // * R: arbitrarylength bigendian encoded R value. It must use the shortest
 // possible encoding for a positive integers (which means no null bytes at
 // the start, except a single one when the next byte has its highest bit set).
 // * Slength: 1byte length descriptor of the S value that follows.
 // * S: arbitrarylength bigendian encoded S value. The same rules apply.
 // * sighash: 1byte value indicating what data is hashed (not part of the DER
 // signature)

 // Minimum and maximum size constraints.
 if (sig.size() < 9) return false;
 if (sig.size() > 73) return false;

 // A signature is of type 0x30 (compound).
 if (sig[0] != 0x30) return false;

 // Make sure the length covers the entire signature.
 if (sig[1] != sig.size()  3) return false;

 // Extract the length of the R element.
 unsigned int lenR = sig[3];

 // Make sure the length of the S element is still inside the signature.
 if (5 + lenR >= sig.size()) return false;

 // Extract the length of the S element.
 unsigned int lenS = sig[5 + lenR];

 // Verify that the length of the signature matches the sum of the length
 // of the elements.
 if ((size_t)(lenR + lenS + 7) != sig.size()) return false;

 // Check whether the R element is an integer.
 if (sig[2] != 0x02) return false;

 // Zerolength integers are not allowed for R.
 if (lenR == 0) return false;

 // Negative numbers are not allowed for R.
 if (sig[4] & 0x80) return false;

 // Null bytes at the start of R are not allowed, unless R would
 // otherwise be interpreted as a negative number.
 if (lenR > 1 && (sig[4] == 0x00) && !(sig[5] & 0x80)) return false;

 // Check whether the S element is an integer.
 if (sig[lenR + 4] != 0x02) return false;

 // Zerolength integers are not allowed for S.
 if (lenS == 0) return false;

 // Negative numbers are not allowed for S.
 if (sig[lenR + 6] & 0x80) return false;

 // Null bytes at the start of S are not allowed, unless S would otherwise be
 // interpreted as a negative number.
 if (lenS > 1 && (sig[lenR + 6] == 0x00) && !(sig[lenR + 7] & 0x80)) return false;

 return true;
 }

 bool static IsLowDERSignature(const valtype &vchSig, ScriptError* serror) {
 if (!IsValidSignatureEncoding(vchSig)) {
 return set_error(serror, SCRIPT_ERR_SIG_DER);
 }
 // https://bitcoin.stackexchange.com/a/12556:
 // Also note that inside transaction signatures, an extra hashtype byte
 // follows the actual signature data.
 std::vector<unsigned char> vchSigCopy(vchSig.begin(), vchSig.begin() + vchSig.size()  1);
 // If the S value is above the order of the curve divided by two, its
 // complement modulo the order could have been used instead, which is
 // one byte shorter when encoded correctly.
 if (!CPubKey::CheckLowS(vchSigCopy)) {
 return set_error(serror, SCRIPT_ERR_SIG_HIGH_S);
 }
 return true;
 }

 bool static IsDefinedHashtypeSignature(const valtype &vchSig) {
 if (vchSig.size() == 0) {
 return false;
 }
 unsigned char nHashType = vchSig[vchSig.size()  1] & (~(SIGHASH_ANYONECANPAY));
 if (nHashType < SIGHASH_ALL  nHashType > SIGHASH_SINGLE)
 return false;

 return true;
 }

 bool CheckSignatureEncoding(const std::vector<unsigned char> &vchSig, unsigned int flags, ScriptError* serror) {
 // Empty signature. Not strictly DER encoded, but allowed to provide a
 // compact way to provide an invalid signature for use with CHECK(MULTI)SIG
 if (vchSig.size() == 0) {
 return true;
 }
 if ((flags & (SCRIPT_VERIFY_DERSIG  SCRIPT_VERIFY_LOW_S  SCRIPT_VERIFY_STRICTENC)) != 0 && !IsValidSignatureEncoding(vchSig)) {
 return set_error(serror, SCRIPT_ERR_SIG_DER);
 } else if ((flags & SCRIPT_VERIFY_LOW_S) != 0 && !IsLowDERSignature(vchSig, serror)) {
 // serror is set
 return false;
 } else if ((flags & SCRIPT_VERIFY_STRICTENC) != 0 && !IsDefinedHashtypeSignature(vchSig)) {
 return set_error(serror, SCRIPT_ERR_SIG_HASHTYPE);
 }
 return true;
 }

 bool static CheckPubKeyEncoding(const valtype &vchPubKey, unsigned int flags, const SigVersion &sigversion, ScriptError* serror) {
 if ((flags & SCRIPT_VERIFY_STRICTENC) != 0 && !IsCompressedOrUncompressedPubKey(vchPubKey)) {
 return set_error(serror, SCRIPT_ERR_PUBKEYTYPE);
 }
 // Only compressed keys are accepted in segwit
 if ((flags & SCRIPT_VERIFY_WITNESS_PUBKEYTYPE) != 0 && sigversion == SIGVERSION_WITNESS_V0 && !IsCompressedPubKey(vchPubKey)) {
 return set_error(serror, SCRIPT_ERR_WITNESS_PUBKEYTYPE);
 }
 return true;
 }

 bool static CheckMinimalPush(const valtype& data, opcodetype opcode) {
 if (data.size() == 0) {
 // Could have used OP_0.
 return opcode == OP_0;
 } else if (data.size() == 1 && data[0] >= 1 && data[0] <= 16) {
 // Could have used OP_1 .. OP_16.
 return opcode == OP_1 + (data[0]  1);
 } else if (data.size() == 1 && data[0] == 0x81) {
 // Could have used OP_1NEGATE.
 return opcode == OP_1NEGATE;
 } else if (data.size() <= 75) {
 // Could have used a direct push (opcode indicating number of bytes pushed + those bytes).
 return opcode == data.size();
 } else if (data.size() <= 255) {
 // Could have used OP_PUSHDATA.
 return opcode == OP_PUSHDATA1;
 } else if (data.size() <= 65535) {
 // Could have used OP_PUSHDATA2.
 return opcode == OP_PUSHDATA2;
 }
 return true;
 }

 bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const BaseSignatureChecker& checker, SigVersion sigversion, ScriptError* serror)
 {
 static const CScriptNum bnZero(0);
 static const CScriptNum bnOne(1);
 // static const CScriptNum bnFalse(0);
 // static const CScriptNum bnTrue(1);
 static const valtype vchFalse(0);
 // static const valtype vchZero(0);
 static const valtype vchTrue(1, 1);

 CScript::const_iterator pc = script.begin();
 CScript::const_iterator pend = script.end();
 CScript::const_iterator pbegincodehash = script.begin();
 opcodetype opcode;
 valtype vchPushValue;
 std::vector<bool> vfExec;
 std::vector<valtype> altstack;
 set_error(serror, SCRIPT_ERR_UNKNOWN_ERROR);
 if (script.size() > MAX_SCRIPT_SIZE)
 return set_error(serror, SCRIPT_ERR_SCRIPT_SIZE);
 int nOpCount = 0;
 bool fRequireMinimal = (flags & SCRIPT_VERIFY_MINIMALDATA) != 0;

 try
 {
 while (pc < pend)
 {
 bool fExec = !count(vfExec.begin(), vfExec.end(), false);

 //
 // Read instruction
 //
 if (!script.GetOp(pc, opcode, vchPushValue))
 return set_error(serror, SCRIPT_ERR_BAD_OPCODE);
 if (vchPushValue.size() > MAX_SCRIPT_ELEMENT_SIZE)
 return set_error(serror, SCRIPT_ERR_PUSH_SIZE);

 // Note how OP_RESERVED does not count towards the opcode limit.
 if (opcode > OP_16 && ++nOpCount > MAX_OPS_PER_SCRIPT)
 return set_error(serror, SCRIPT_ERR_OP_COUNT);

 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 set_error(serror, SCRIPT_ERR_DISABLED_OPCODE); // Disabled opcodes.

 // With SCRIPT_VERIFY_CONST_SCRIPTCODE, OP_CODESEPARATOR in nonsegwit script is rejected even in an unexecuted branch
 if (opcode == OP_CODESEPARATOR && sigversion == SIGVERSION_BASE && (flags & SCRIPT_VERIFY_CONST_SCRIPTCODE))
 return set_error(serror, SCRIPT_ERR_OP_CODESEPARATOR);

 if (fExec && 0 <= opcode && opcode <= OP_PUSHDATA4) {
 if (fRequireMinimal && !CheckMinimalPush(vchPushValue, opcode)) {
 return set_error(serror, SCRIPT_ERR_MINIMALDATA);
 }
 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)
 CScriptNum bn((int)opcode  (int)(OP_1  1));
 stack.push_back(bn.getvch());
 // The result of these opcodes should always be the minimal way to push the data
 // they push, so no need for a CheckMinimalPush here.
 }
 break;


 //
 // Control
 //
 case OP_NOP:
 break;

 case OP_CHECKLOCKTIMEVERIFY:
 {
 if (!(flags & SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY)) {
 // not enabled; treat as a NOP2
 break;
 }

 if (stack.size() < 1)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);

 // Note that elsewhere numeric opcodes are limited to
 // operands in the range 2**31+1 to 2**311, however it is
 // legal for opcodes to produce results exceeding that
 // range. This limitation is implemented by CScriptNum's
 // default 4byte limit.
 //
 // If we kept to that limit we'd have a year 2038 problem,
 // even though the nLockTime field in transactions
 // themselves is uint32 which only becomes meaningless
 // after the year 2106.
 //
 // Thus as a special case we tell CScriptNum to accept up
 // to 5byte bignums, which are good until 2**391, well
 // beyond the 2**321 limit of the nLockTime field itself.
 const CScriptNum nLockTime(stacktop(1), fRequireMinimal, 5);

 // In the rare event that the argument may be < 0 due to
 // some arithmetic being done first, you can always use
 // 0 MAX CHECKLOCKTIMEVERIFY.
 if (nLockTime < 0)
 return set_error(serror, SCRIPT_ERR_NEGATIVE_LOCKTIME);

 // Actually compare the specified lock time with the transaction.
 if (!checker.CheckLockTime(nLockTime))
 return set_error(serror, SCRIPT_ERR_UNSATISFIED_LOCKTIME);

 break;
 }

 case OP_CHECKSEQUENCEVERIFY:
 {
 if (!(flags & SCRIPT_VERIFY_CHECKSEQUENCEVERIFY)) {
 // not enabled; treat as a NOP3
 break;
 }

 if (stack.size() < 1)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);

 // nSequence, like nLockTime, is a 32bit unsigned integer
 // field. See the comment in CHECKLOCKTIMEVERIFY regarding
 // 5byte numeric operands.
 const CScriptNum nSequence(stacktop(1), fRequireMinimal, 5);

 // In the rare event that the argument may be < 0 due to
 // some arithmetic being done first, you can always use
 // 0 MAX CHECKSEQUENCEVERIFY.
 if (nSequence < 0)
 return set_error(serror, SCRIPT_ERR_NEGATIVE_LOCKTIME);

 // To provide for future softfork extensibility, if the
 // operand has the disabled locktime flag set,
 // CHECKSEQUENCEVERIFY behaves as a NOP.
 if ((nSequence & CTxIn::SEQUENCE_LOCKTIME_DISABLE_FLAG) != 0)
 break;

 // Compare the specified sequence number with the input.
 if (!checker.CheckSequence(nSequence))
 return set_error(serror, SCRIPT_ERR_UNSATISFIED_LOCKTIME);

 break;
 }

 case OP_NOP1: case OP_NOP4: case OP_NOP5:
 case OP_NOP6: case OP_NOP7: case OP_NOP8: case OP_NOP9: case OP_NOP10:
 {
 if (flags & SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS)
 return set_error(serror, SCRIPT_ERR_DISCOURAGE_UPGRADABLE_NOPS);
 }
 break;

 case OP_IF:
 case OP_NOTIF:
 {
 // <expression> if [statements] [else [statements]] endif
 bool fValue = false;
 if (fExec)
 {
 if (stack.size() < 1)
 return set_error(serror, SCRIPT_ERR_UNBALANCED_CONDITIONAL);
 valtype& vch = stacktop(1);
 if (sigversion == SIGVERSION_WITNESS_V0 && (flags & SCRIPT_VERIFY_MINIMALIF)) {
 if (vch.size() > 1)
 return set_error(serror, SCRIPT_ERR_MINIMALIF);
 if (vch.size() == 1 && vch[0] != 1)
 return set_error(serror, SCRIPT_ERR_MINIMALIF);
 }
 fValue = CastToBool(vch);
 if (opcode == OP_NOTIF)
 fValue = !fValue;
 popstack(stack);
 }
 vfExec.push_back(fValue);
 }
 break;

 case OP_ELSE:
 {
 if (vfExec.empty())
 return set_error(serror, SCRIPT_ERR_UNBALANCED_CONDITIONAL);
 vfExec.back() = !vfExec.back();
 }
 break;

 case OP_ENDIF:
 {
 if (vfExec.empty())
 return set_error(serror, SCRIPT_ERR_UNBALANCED_CONDITIONAL);
 vfExec.pop_back();
 }
 break;

 case OP_VERIFY:
 {
 // (true  ) or
 // (false  false) and return
 if (stack.size() < 1)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 bool fValue = CastToBool(stacktop(1));
 if (fValue)
 popstack(stack);
 else
 return set_error(serror, SCRIPT_ERR_VERIFY);
 }
 break;

 case OP_RETURN:
 {
 return set_error(serror, SCRIPT_ERR_OP_RETURN);
 }
 break;


 //
 // Stack ops
 //
 case OP_TOALTSTACK:
 {
 if (stack.size() < 1)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 altstack.push_back(stacktop(1));
 popstack(stack);
 }
 break;

 case OP_FROMALTSTACK:
 {
 if (altstack.size() < 1)
 return set_error(serror, SCRIPT_ERR_INVALID_ALTSTACK_OPERATION);
 stack.push_back(altstacktop(1));
 popstack(altstack);
 }
 break;

 case OP_2DROP:
 {
 // (x1 x2  )
 if (stack.size() < 2)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 popstack(stack);
 popstack(stack);
 }
 break;

 case OP_2DUP:
 {
 // (x1 x2  x1 x2 x1 x2)
 if (stack.size() < 2)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 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 set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 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 set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 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 set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 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 set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 swap(stacktop(4), stacktop(2));
 swap(stacktop(3), stacktop(1));
 }
 break;

 case OP_IFDUP:
 {
 // (x  0  x x)
 if (stack.size() < 1)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 valtype vch = stacktop(1);
 if (CastToBool(vch))
 stack.push_back(vch);
 }
 break;

 case OP_DEPTH:
 {
 //  stacksize
 CScriptNum bn(stack.size());
 stack.push_back(bn.getvch());
 }
 break;

 case OP_DROP:
 {
 // (x  )
 if (stack.size() < 1)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 popstack(stack);
 }
 break;

 case OP_DUP:
 {
 // (x  x x)
 if (stack.size() < 1)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 valtype vch = stacktop(1);
 stack.push_back(vch);
 }
 break;

 case OP_NIP:
 {
 // (x1 x2  x2)
 if (stack.size() < 2)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 stack.erase(stack.end()  2);
 }
 break;

 case OP_OVER:
 {
 // (x1 x2  x1 x2 x1)
 if (stack.size() < 2)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 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 set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 int n = CScriptNum(stacktop(1), fRequireMinimal).getint();
 popstack(stack);
 if (n < 0  n >= (int)stack.size())
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 valtype vch = stacktop(n1);
 if (opcode == OP_ROLL)
 stack.erase(stack.end()n1);
 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 set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 swap(stacktop(3), stacktop(2));
 swap(stacktop(2), stacktop(1));
 }
 break;

 case OP_SWAP:
 {
 // (x1 x2  x2 x1)
 if (stack.size() < 2)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 swap(stacktop(2), stacktop(1));
 }
 break;

 case OP_TUCK:
 {
 // (x1 x2  x2 x1 x2)
 if (stack.size() < 2)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 valtype vch = stacktop(1);
 stack.insert(stack.end()2, vch);
 }
 break;


 case OP_SIZE:
 {
 // (in  in size)
 if (stack.size() < 1)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 CScriptNum 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 set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 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 set_error(serror, SCRIPT_ERR_EQUALVERIFY);
 }
 }
 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 set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 CScriptNum bn(stacktop(1), fRequireMinimal);
 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 set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 CScriptNum bn1(stacktop(2), fRequireMinimal);
 CScriptNum bn2(stacktop(1), fRequireMinimal);
 CScriptNum bn(0);
 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 set_error(serror, SCRIPT_ERR_NUMEQUALVERIFY);
 }
 }
 break;

 case OP_WITHIN:
 {
 // (x min max  out)
 if (stack.size() < 3)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 CScriptNum bn1(stacktop(3), fRequireMinimal);
 CScriptNum bn2(stacktop(2), fRequireMinimal);
 CScriptNum bn3(stacktop(1), fRequireMinimal);
 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 set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 valtype& vch = stacktop(1);
 valtype vchHash((opcode == OP_RIPEMD160  opcode == OP_SHA1  opcode == OP_HASH160) ? 20 : 32);
 if (opcode == OP_RIPEMD160)
 CRIPEMD160().Write(vch.data(), vch.size()).Finalize(vchHash.data());
 else if (opcode == OP_SHA1)
 CSHA1().Write(vch.data(), vch.size()).Finalize(vchHash.data());
 else if (opcode == OP_SHA256)
 CSHA256().Write(vch.data(), vch.size()).Finalize(vchHash.data());
 else if (opcode == OP_HASH160)
 CHash160().Write(vch.data(), vch.size()).Finalize(vchHash.data());
 else if (opcode == OP_HASH256)
 CHash256().Write(vch.data(), vch.size()).Finalize(vchHash.data());
 popstack(stack);
 stack.push_back(vchHash);
 }
 break;

 case OP_CODESEPARATOR:
 {
 // If SCRIPT_VERIFY_CONST_SCRIPTCODE flag is set, use of OP_CODESEPARATOR is rejected in presegwit
 // script, even in an unexecuted branch (this is checked above the opcode case statement).

 // Hash starts after the code separator
 pbegincodehash = pc;
 }
 break;

 case OP_CHECKSIG:
 case OP_CHECKSIGVERIFY:
 {
 // (sig pubkey  bool)
 if (stack.size() < 2)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);

 valtype& vchSig = stacktop(2);
 valtype& vchPubKey = stacktop(1);

 // Subset of script starting at the most recent codeseparator
 CScript scriptCode(pbegincodehash, pend);

 // Drop the signature in presegwit scripts but not segwit scripts
 if (sigversion == SIGVERSION_BASE) {
 int found = scriptCode.FindAndDelete(CScript(vchSig));
 if (found > 0 && (flags & SCRIPT_VERIFY_CONST_SCRIPTCODE))
 return set_error(serror, SCRIPT_ERR_SIG_FINDANDDELETE);
 }

 if (!CheckSignatureEncoding(vchSig, flags, serror)  !CheckPubKeyEncoding(vchPubKey, flags, sigversion, serror)) {
 //serror is set
 return false;
 }
 bool fSuccess = checker.CheckSig(vchSig, vchPubKey, scriptCode, sigversion);

 if (!fSuccess && (flags & SCRIPT_VERIFY_NULLFAIL) && vchSig.size())
 return set_error(serror, SCRIPT_ERR_SIG_NULLFAIL);

 popstack(stack);
 popstack(stack);
 stack.push_back(fSuccess ? vchTrue : vchFalse);
 if (opcode == OP_CHECKSIGVERIFY)
 {
 if (fSuccess)
 popstack(stack);
 else
 return set_error(serror, SCRIPT_ERR_CHECKSIGVERIFY);
 }
 }
 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 set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);

 int nKeysCount = CScriptNum(stacktop(i), fRequireMinimal).getint();
 if (nKeysCount < 0  nKeysCount > MAX_PUBKEYS_PER_MULTISIG)
 return set_error(serror, SCRIPT_ERR_PUBKEY_COUNT);
 nOpCount += nKeysCount;
 if (nOpCount > MAX_OPS_PER_SCRIPT)
 return set_error(serror, SCRIPT_ERR_OP_COUNT);
 int ikey = ++i;
 // ikey2 is the position of last nonsignature item in the stack. Top stack item = 1.
 // With SCRIPT_VERIFY_NULLFAIL, this is used for cleanup if operation fails.
 int ikey2 = nKeysCount + 2;
 i += nKeysCount;
 if ((int)stack.size() < i)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);

 int nSigsCount = CScriptNum(stacktop(i), fRequireMinimal).getint();
 if (nSigsCount < 0  nSigsCount > nKeysCount)
 return set_error(serror, SCRIPT_ERR_SIG_COUNT);
 int isig = ++i;
 i += nSigsCount;
 if ((int)stack.size() < i)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);

 // Subset of script starting at the most recent codeseparator
 CScript scriptCode(pbegincodehash, pend);

 // Drop the signature in presegwit scripts but not segwit scripts
 for (int k = 0; k < nSigsCount; k++)
 {
 valtype& vchSig = stacktop(isigk);
 if (sigversion == SIGVERSION_BASE) {
 int found = scriptCode.FindAndDelete(CScript(vchSig));
 if (found > 0 && (flags & SCRIPT_VERIFY_CONST_SCRIPTCODE))
 return set_error(serror, SCRIPT_ERR_SIG_FINDANDDELETE);
 }
 }

 bool fSuccess = true;
 while (fSuccess && nSigsCount > 0)
 {
 valtype& vchSig = stacktop(isig);
 valtype& vchPubKey = stacktop(ikey);

 // Note how this makes the exact order of pubkey/signature evaluation
 // distinguishable by CHECKMULTISIG NOT if the STRICTENC flag is set.
 // See the script_(in)valid tests for details.
 if (!CheckSignatureEncoding(vchSig, flags, serror)  !CheckPubKeyEncoding(vchPubKey, flags, sigversion, serror)) {
 // serror is set
 return false;
 }

 // Check signature
 bool fOk = checker.CheckSig(vchSig, vchPubKey, scriptCode, sigversion);

 if (fOk) {
 isig++;
 nSigsCount;
 }
 ikey++;
 nKeysCount;

 // If there are more signatures left than keys left,
 // then too many signatures have failed. Exit early,
 // without checking any further signatures.
 if (nSigsCount > nKeysCount)
 fSuccess = false;
 }

 // Clean up stack of actual arguments
 while (i > 1) {
 // If the operation failed, we require that all signatures must be empty vector
 if (!fSuccess && (flags & SCRIPT_VERIFY_NULLFAIL) && !ikey2 && stacktop(1).size())
 return set_error(serror, SCRIPT_ERR_SIG_NULLFAIL);
 if (ikey2 > 0)
 ikey2;
 popstack(stack);
 }

 // A bug causes CHECKMULTISIG to consume one extra argument
 // whose contents were not checked in any way.
 //
 // Unfortunately this is a potential source of mutability,
 // so optionally verify it is exactly equal to zero prior
 // to removing it from the stack.
 if (stack.size() < 1)
 return set_error(serror, SCRIPT_ERR_INVALID_STACK_OPERATION);
 if ((flags & SCRIPT_VERIFY_NULLDUMMY) && stacktop(1).size())
 return set_error(serror, SCRIPT_ERR_SIG_NULLDUMMY);
 popstack(stack);

 stack.push_back(fSuccess ? vchTrue : vchFalse);

 if (opcode == OP_CHECKMULTISIGVERIFY)
 {
 if (fSuccess)
 popstack(stack);
 else
 return set_error(serror, SCRIPT_ERR_CHECKMULTISIGVERIFY);
 }
 }
 break;

 default:
 return set_error(serror, SCRIPT_ERR_BAD_OPCODE);
 }

 // Size limits
 if (stack.size() + altstack.size() > MAX_STACK_SIZE)
 return set_error(serror, SCRIPT_ERR_STACK_SIZE);
 }
 }
 catch (...)
 {
 return set_error(serror, SCRIPT_ERR_UNKNOWN_ERROR);
 }

 if (!vfExec.empty())
 return set_error(serror, SCRIPT_ERR_UNBALANCED_CONDITIONAL);

 return set_success(serror);
 }

 namespace {

 /**
 * Wrapper that serializes like CTransaction, but with the modifications
 * required for the signature hash done inplace
 */
 class CTransactionSignatureSerializer {
 private:
 const CTransaction& txTo; //!< reference to the spending transaction (the one being serialized)
 const CScript& scriptCode; //!< output script being consumed
 const unsigned int nIn; //!< input index of txTo being signed
 const bool fAnyoneCanPay; //!< whether the hashtype has the SIGHASH_ANYONECANPAY flag set
 const bool fHashSingle; //!< whether the hashtype is SIGHASH_SINGLE
 const bool fHashNone; //!< whether the hashtype is SIGHASH_NONE

 public:
 CTransactionSignatureSerializer(const CTransaction &txToIn, const CScript &scriptCodeIn, unsigned int nInIn, int nHashTypeIn) :
 txTo(txToIn), scriptCode(scriptCodeIn), nIn(nInIn),
 fAnyoneCanPay(!!(nHashTypeIn & SIGHASH_ANYONECANPAY)),
 fHashSingle((nHashTypeIn & 0x1f) == SIGHASH_SINGLE),
 fHashNone((nHashTypeIn & 0x1f) == SIGHASH_NONE) {}

 /** Serialize the passed scriptCode, skipping OP_CODESEPARATORs */
 template<typename S>
 void SerializeScriptCode(S &s) const {
 CScript::const_iterator it = scriptCode.begin();
 CScript::const_iterator itBegin = it;
 opcodetype opcode;
 unsigned int nCodeSeparators = 0;
 while (scriptCode.GetOp(it, opcode)) {
 if (opcode == OP_CODESEPARATOR)
 nCodeSeparators++;
 }
 ::WriteCompactSize(s, scriptCode.size()  nCodeSeparators);
 it = itBegin;
 while (scriptCode.GetOp(it, opcode)) {
 if (opcode == OP_CODESEPARATOR) {
 s.write((char*)&itBegin[0], ititBegin1);
 itBegin = it;
 }
 }
 if (itBegin != scriptCode.end())
 s.write((char*)&itBegin[0], ititBegin);
 }

 /** Serialize an input of txTo */
 template<typename S>
 void SerializeInput(S &s, unsigned int nInput) const {
 // In case of SIGHASH_ANYONECANPAY, only the input being signed is serialized
 if (fAnyoneCanPay)
 nInput = nIn;
 // Serialize the prevout
 ::Serialize(s, txTo.vin[nInput].prevout);
 // Serialize the script
 if (nInput != nIn)
 // Blank out other inputs' signatures
 ::Serialize(s, CScript());
 else
 SerializeScriptCode(s);
 // Serialize the nSequence
 if (nInput != nIn && (fHashSingle  fHashNone))
 // let the others update at will
 ::Serialize(s, (int)0);
 else
 ::Serialize(s, txTo.vin[nInput].nSequence);
 }

 /** Serialize an output of txTo */
 template<typename S>
 void SerializeOutput(S &s, unsigned int nOutput) const {
 if (fHashSingle && nOutput != nIn)
 // Do not lockin the txout payee at other indices as txin
 ::Serialize(s, CTxOut());
 else
 ::Serialize(s, txTo.vout[nOutput]);
 }

 /** Serialize txTo */
 template<typename S>
 void Serialize(S &s) const {
 // Serialize nVersion
 ::Serialize(s, txTo.nVersion);
 // Serialize vin
 unsigned int nInputs = fAnyoneCanPay ? 1 : txTo.vin.size();
 ::WriteCompactSize(s, nInputs);
 for (unsigned int nInput = 0; nInput < nInputs; nInput++)
 SerializeInput(s, nInput);
 // Serialize vout
 unsigned int nOutputs = fHashNone ? 0 : (fHashSingle ? nIn+1 : txTo.vout.size());
 ::WriteCompactSize(s, nOutputs);
 for (unsigned int nOutput = 0; nOutput < nOutputs; nOutput++)
 SerializeOutput(s, nOutput);
 // Serialize nLockTime
 ::Serialize(s, txTo.nLockTime);
 }
 };

 uint256 GetPrevoutHash(const CTransaction& txTo) {
 CHashWriter ss(SER_GETHASH, 0);
 for (const auto& txin : txTo.vin) {
 ss << txin.prevout;
 }
 return ss.GetHash();
 }

 uint256 GetSequenceHash(const CTransaction& txTo) {
 CHashWriter ss(SER_GETHASH, 0);
 for (const auto& txin : txTo.vin) {
 ss << txin.nSequence;
 }
 return ss.GetHash();
 }

 uint256 GetOutputsHash(const CTransaction& txTo) {
 CHashWriter ss(SER_GETHASH, 0);
 for (const auto& txout : txTo.vout) {
 ss << txout;
 }
 return ss.GetHash();
 }

 } // namespace

 PrecomputedTransactionData::PrecomputedTransactionData(const CTransaction& txTo)
 {
 // Cache is calculated only for transactions with witness
 if (txTo.HasWitness()) {
 hashPrevouts = GetPrevoutHash(txTo);
 hashSequence = GetSequenceHash(txTo);
 hashOutputs = GetOutputsHash(txTo);
 ready = true;
 }
 }

 uint256 SignatureHash(const CScript& scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion, const PrecomputedTransactionData* cache)
 {
 assert(nIn < txTo.vin.size());

 if (sigversion == SIGVERSION_WITNESS_V0) {
 uint256 hashPrevouts;
 uint256 hashSequence;
 uint256 hashOutputs;
 const bool cacheready = cache && cache>ready;

 if (!(nHashType & SIGHASH_ANYONECANPAY)) {
 hashPrevouts = cacheready ? cache>hashPrevouts : GetPrevoutHash(txTo);
 }

 if (!(nHashType & SIGHASH_ANYONECANPAY) && (nHashType & 0x1f) != SIGHASH_SINGLE && (nHashType & 0x1f) != SIGHASH_NONE) {
 hashSequence = cacheready ? cache>hashSequence : GetSequenceHash(txTo);
 }


 if ((nHashType & 0x1f) != SIGHASH_SINGLE && (nHashType & 0x1f) != SIGHASH_NONE) {
 hashOutputs = cacheready ? cache>hashOutputs : GetOutputsHash(txTo);
 } else if ((nHashType & 0x1f) == SIGHASH_SINGLE && nIn < txTo.vout.size()) {
 CHashWriter ss(SER_GETHASH, 0);
 ss << txTo.vout[nIn];
 hashOutputs = ss.GetHash();
 }

 CHashWriter ss(SER_GETHASH, 0);
 // Version
 ss << txTo.nVersion;
 // Input prevouts/nSequence (none/all, depending on flags)
 ss << hashPrevouts;
 ss << hashSequence;
 // The input being signed (replacing the scriptSig with scriptCode + amount)
 // The prevout may already be contained in hashPrevout, and the nSequence
 // may already be contain in hashSequence.
 ss << txTo.vin[nIn].prevout;
 ss << scriptCode;
 ss << amount;
 ss << txTo.vin[nIn].nSequence;
 // Outputs (none/one/all, depending on flags)
 ss << hashOutputs;
 // Locktime
 ss << txTo.nLockTime;
 // Sighash type
 ss << nHashType;

 return ss.GetHash();
 }

 static const uint256 one(uint256S("0000000000000000000000000000000000000000000000000000000000000001"));

 // Check for invalid use of SIGHASH_SINGLE
 if ((nHashType & 0x1f) == SIGHASH_SINGLE) {
 if (nIn >= txTo.vout.size()) {
 // nOut out of range
 return one;
 }
 }

 // Wrapper to serialize only the necessary parts of the transaction being signed
 CTransactionSignatureSerializer txTmp(txTo, scriptCode, nIn, nHashType);

 // Serialize and hash
 CHashWriter ss(SER_GETHASH, 0);
 ss << txTmp << nHashType;
 return ss.GetHash();
 }

 bool TransactionSignatureChecker::VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& pubkey, const uint256& sighash) const
 {
 return pubkey.Verify(sighash, vchSig);
 }

 bool TransactionSignatureChecker::CheckSig(const std::vector<unsigned char>& vchSigIn, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const
 {
 CPubKey pubkey(vchPubKey);
 if (!pubkey.IsValid())
 return false;

 // Hash type is one byte tacked on to the end of the signature
 std::vector<unsigned char> vchSig(vchSigIn);
 if (vchSig.empty())
 return false;
 int nHashType = vchSig.back();
 vchSig.pop_back();

 uint256 sighash = SignatureHash(scriptCode, *txTo, nIn, nHashType, amount, sigversion, this>txdata);

 if (!VerifySignature(vchSig, pubkey, sighash))
 return false;

 return true;
 }

 bool TransactionSignatureChecker::CheckLockTime(const CScriptNum& nLockTime) const
 {
 // There are two kinds of nLockTime: lockbyblockheight
 // and lockbyblocktime, distinguished by whether
 // nLockTime < LOCKTIME_THRESHOLD.
 //
 // We want to compare apples to apples, so fail the script
 // unless the type of nLockTime being tested is the same as
 // the nLockTime in the transaction.
 if (!(
 (txTo>nLockTime < LOCKTIME_THRESHOLD && nLockTime < LOCKTIME_THRESHOLD) 
 (txTo>nLockTime >= LOCKTIME_THRESHOLD && nLockTime >= LOCKTIME_THRESHOLD)
 ))
 return false;

 // Now that we know we're comparing applestoapples, the
 // comparison is a simple numeric one.
 if (nLockTime > (int64_t)txTo>nLockTime)
 return false;

 // Finally the nLockTime feature can be disabled and thus
 // CHECKLOCKTIMEVERIFY bypassed if every txin has been
 // finalized by setting nSequence to maxint. The
 // transaction would be allowed into the blockchain, making
 // the opcode ineffective.
 //
 // Testing if this vin is not final is sufficient to
 // prevent this condition. Alternatively we could test all
 // inputs, but testing just this input minimizes the data
 // required to prove correct CHECKLOCKTIMEVERIFY execution.
 if (CTxIn::SEQUENCE_FINAL == txTo>vin[nIn].nSequence)
 return false;

 return true;
 }

 bool TransactionSignatureChecker::CheckSequence(const CScriptNum& nSequence) const
 {
 // Relative lock times are supported by comparing the passed
 // in operand to the sequence number of the input.
 const int64_t txToSequence = (int64_t)txTo>vin[nIn].nSequence;

 // Fail if the transaction's version number is not set high
 // enough to trigger BIP 68 rules.
 if (static_cast<uint32_t>(txTo>nVersion) < 2)
 return false;

 // Sequence numbers with their most significant bit set are not
 // consensus constrained. Testing that the transaction's sequence
 // number do not have this bit set prevents using this property
 // to get around a CHECKSEQUENCEVERIFY check.
 if (txToSequence & CTxIn::SEQUENCE_LOCKTIME_DISABLE_FLAG)
 return false;

 // Mask off any bits that do not have consensusenforced meaning
 // before doing the integer comparisons
 const uint32_t nLockTimeMask = CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG  CTxIn::SEQUENCE_LOCKTIME_MASK;
 const int64_t txToSequenceMasked = txToSequence & nLockTimeMask;
 const CScriptNum nSequenceMasked = nSequence & nLockTimeMask;

 // There are two kinds of nSequence: lockbyblockheight
 // and lockbyblocktime, distinguished by whether
 // nSequenceMasked < CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG.
 //
 // We want to compare apples to apples, so fail the script
 // unless the type of nSequenceMasked being tested is the same as
 // the nSequenceMasked in the transaction.
 if (!(
 (txToSequenceMasked < CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG && nSequenceMasked < CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG) 
 (txToSequenceMasked >= CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG && nSequenceMasked >= CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG)
 )) {
 return false;
 }

 // Now that we know we're comparing applestoapples, the
 // comparison is a simple numeric one.
 if (nSequenceMasked > txToSequenceMasked)
 return false;

 return true;
 }

 static bool VerifyWitnessProgram(const CScriptWitness& witness, int witversion, const std::vector<unsigned char>& program, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* serror)
 {
 std::vector<std::vector<unsigned char> > stack;
 CScript scriptPubKey;

 if (witversion == 0) {
 if (program.size() == 32) {
 // Version 0 segregated witness program: SHA256(CScript) inside the program, CScript + inputs in witness
 if (witness.stack.size() == 0) {
 return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_WITNESS_EMPTY);
 }
 scriptPubKey = CScript(witness.stack.back().begin(), witness.stack.back().end());
 stack = std::vector<std::vector<unsigned char> >(witness.stack.begin(), witness.stack.end()  1);
 uint256 hashScriptPubKey;
 CSHA256().Write(&scriptPubKey[0], scriptPubKey.size()).Finalize(hashScriptPubKey.begin());
 if (memcmp(hashScriptPubKey.begin(), program.data(), 32)) {
 return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_MISMATCH);
 }
 } else if (program.size() == 20) {
 // Special case for paytopubkeyhash; signature + pubkey in witness
 if (witness.stack.size() != 2) {
 return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_MISMATCH); // 2 items in witness
 }
 scriptPubKey << OP_DUP << OP_HASH160 << program << OP_EQUALVERIFY << OP_CHECKSIG;
 stack = witness.stack;
 } else {
 return set_error(serror, SCRIPT_ERR_WITNESS_PROGRAM_WRONG_LENGTH);
 }
 } else if (flags & SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM) {
 return set_error(serror, SCRIPT_ERR_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM);
 } else {
 // Higher version witness scripts return true for future softfork compatibility
 return set_success(serror);
 }

 // Disallow stack item size > MAX_SCRIPT_ELEMENT_SIZE in witness stack
 for (unsigned int i = 0; i < stack.size(); i++) {
 if (stack.at(i).size() > MAX_SCRIPT_ELEMENT_SIZE)
 return set_error(serror, SCRIPT_ERR_PUSH_SIZE);
 }

 if (!EvalScript(stack, scriptPubKey, flags, checker, SIGVERSION_WITNESS_V0, serror)) {
 return false;
 }

 // Scripts inside witness implicitly require cleanstack behaviour
 if (stack.size() != 1)
 return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
 if (!CastToBool(stack.back()))
 return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
 return true;
 }

 bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, const CScriptWitness* witness, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* serror)
 {
 static const CScriptWitness emptyWitness;
 if (witness == nullptr) {
 witness = &emptyWitness;
 }
 bool hadWitness = false;

 set_error(serror, SCRIPT_ERR_UNKNOWN_ERROR);

 if ((flags & SCRIPT_VERIFY_SIGPUSHONLY) != 0 && !scriptSig.IsPushOnly()) {
 return set_error(serror, SCRIPT_ERR_SIG_PUSHONLY);
 }

 std::vector<std::vector<unsigned char> > stack, stackCopy;
 if (!EvalScript(stack, scriptSig, flags, checker, SIGVERSION_BASE, serror))
 // serror is set
 return false;
 if (flags & SCRIPT_VERIFY_P2SH)
 stackCopy = stack;
 if (!EvalScript(stack, scriptPubKey, flags, checker, SIGVERSION_BASE, serror))
 // serror is set
 return false;
 if (stack.empty())
 return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
 if (CastToBool(stack.back()) == false)
 return set_error(serror, SCRIPT_ERR_EVAL_FALSE);

 // Bare witness programs
 int witnessversion;
 std::vector<unsigned char> witnessprogram;
 if (flags & SCRIPT_VERIFY_WITNESS) {
 if (scriptPubKey.IsWitnessProgram(witnessversion, witnessprogram)) {
 hadWitness = true;
 if (scriptSig.size() != 0) {
 // The scriptSig must be _exactly_ CScript(), otherwise we reintroduce malleability.
 return set_error(serror, SCRIPT_ERR_WITNESS_MALLEATED);
 }
 if (!VerifyWitnessProgram(*witness, witnessversion, witnessprogram, flags, checker, serror)) {
 return false;
 }
 // Bypass the cleanstack check at the end. The actual stack is obviously not clean
 // for witness programs.
 stack.resize(1);
 }
 }

 // Additional validation for spendtoscripthash transactions:
 if ((flags & SCRIPT_VERIFY_P2SH) && scriptPubKey.IsPayToScriptHash())
 {
 // scriptSig must be literalsonly or validation fails
 if (!scriptSig.IsPushOnly())
 return set_error(serror, SCRIPT_ERR_SIG_PUSHONLY);

 // Restore stack.
 swap(stack, stackCopy);

 // stack 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(!stack.empty());

 const valtype& pubKeySerialized = stack.back();
 CScript pubKey2(pubKeySerialized.begin(), pubKeySerialized.end());
 popstack(stack);

 if (!EvalScript(stack, pubKey2, flags, checker, SIGVERSION_BASE, serror))
 // serror is set
 return false;
 if (stack.empty())
 return set_error(serror, SCRIPT_ERR_EVAL_FALSE);
 if (!CastToBool(stack.back()))
 return set_error(serror, SCRIPT_ERR_EVAL_FALSE);

 // P2SH witness program
 if (flags & SCRIPT_VERIFY_WITNESS) {
 if (pubKey2.IsWitnessProgram(witnessversion, witnessprogram)) {
 hadWitness = true;
 if (scriptSig != CScript() << std::vector<unsigned char>(pubKey2.begin(), pubKey2.end())) {
 // The scriptSig must be _exactly_ a single push of the redeemScript. Otherwise we
 // reintroduce malleability.
 return set_error(serror, SCRIPT_ERR_WITNESS_MALLEATED_P2SH);
 }
 if (!VerifyWitnessProgram(*witness, witnessversion, witnessprogram, flags, checker, serror)) {
 return false;
 }
 // Bypass the cleanstack check at the end. The actual stack is obviously not clean
 // for witness programs.
 stack.resize(1);
 }
 }
 }

 // The CLEANSTACK check is only performed after potential P2SH evaluation,
 // as the nonP2SH evaluation of a P2SH script will obviously not result in
 // a clean stack (the P2SH inputs remain). The same holds for witness evaluation.
 if ((flags & SCRIPT_VERIFY_CLEANSTACK) != 0) {
 // Disallow CLEANSTACK without P2SH, as otherwise a switch CLEANSTACK>P2SH+CLEANSTACK
 // would be possible, which is not a softfork (and P2SH should be one).
 assert((flags & SCRIPT_VERIFY_P2SH) != 0);
 assert((flags & SCRIPT_VERIFY_WITNESS) != 0);
 if (stack.size() != 1) {
 return set_error(serror, SCRIPT_ERR_CLEANSTACK);
 }
 }

 if (flags & SCRIPT_VERIFY_WITNESS) {
 // We can't check for correct unexpected witness data if P2SH was off, so require
 // that WITNESS implies P2SH. Otherwise, going from WITNESS>P2SH+WITNESS would be
 // possible, which is not a softfork.

 // assert((flags & SCRIPT_VERIFY_P2SH) != 0);
 if (!hadWitness && !witness>IsNull()) {
 return set_error(serror, SCRIPT_ERR_WITNESS_UNEXPECTED);
 }
 }

 return set_success(serror);
 }

 size_t static WitnessSigOps(int witversion, const std::vector<unsigned char>& witprogram, const CScriptWitness& witness, int flags)
 {
 if (witversion == 0) {
 if (witprogram.size() == 20)
 return 1;

 if (witprogram.size() == 32 && witness.stack.size() > 0) {
 CScript subscript(witness.stack.back().begin(), witness.stack.back().end());
 return subscript.GetSigOpCount(true);
 }
 }

 // Future flags may be implemented here.
 return 0;
 }

 size_t CountWitnessSigOps(const CScript& scriptSig, const CScript& scriptPubKey, const CScriptWitness* witness, unsigned int flags)
 {
 static const CScriptWitness witnessEmpty;

 if ((flags & SCRIPT_VERIFY_WITNESS) == 0) {
 return 0;
 }
 // assert((flags & SCRIPT_VERIFY_P2SH) != 0);

 int witnessversion;
 std::vector<unsigned char> witnessprogram;
 if (scriptPubKey.IsWitnessProgram(witnessversion, witnessprogram)) {
 return WitnessSigOps(witnessversion, witnessprogram, witness ? *witness : witnessEmpty, flags);
 }

 if (scriptPubKey.IsPayToScriptHash() && scriptSig.IsPushOnly()) {
 CScript::const_iterator pc = scriptSig.begin();
 std::vector<unsigned char> data;
 while (pc < scriptSig.end()) {
 opcodetype opcode;
 scriptSig.GetOp(pc, opcode, data);
 }
 CScript subscript(data.begin(), data.end());
 if (subscript.IsWitnessProgram(witnessversion, witnessprogram)) {
 return WitnessSigOps(witnessversion, witnessprogram, witness ? *witness : witnessEmpty, flags);
 }
 }

 return 0;
 }
