dash/src/script.cpp

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2011 The Bitcoin developers
// Distributed under the MIT/X11 software license, see the accompanying
// file license.txt or http://www.opensource.org/licenses/mit-license.php.
#include "headers.h"

using namespace std;
using namespace boost;

bool CheckSig(vector<unsigned char> vchSig, vector<unsigned char> vchPubKey, CScript scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType);



typedef vector<unsigned char> valtype;
static const valtype vchFalse(0);
static const valtype vchZero(0);
static const valtype vchTrue(1, 1);
static const CBigNum bnZero(0);
static const CBigNum bnOne(1);
static const CBigNum bnFalse(0);
static const CBigNum bnTrue(1);
static const size_t nMaxNumSize = 4;


CBigNum CastToBigNum(const valtype& vch)
{
    if (vch.size() > nMaxNumSize)
        throw runtime_error("CastToBigNum() : overflow");
    // Get rid of extra leading zeros
    return CBigNum(CBigNum(vch).getvch());
}

bool CastToBool(const valtype& vch)
{
    for (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;
}

void MakeSameSize(valtype& vch1, valtype& vch2)
{
    // Lengthen the shorter one
    if (vch1.size() < vch2.size())
        vch1.resize(vch2.size(), 0);
    if (vch2.size() < vch1.size())
        vch2.resize(vch1.size(), 0);
}



//
// Script is a stack machine (like Forth) that evaluates a predicate
// returning a bool indicating valid or not.  There are no loops.
//
#define stacktop(i)  (stack.at(stack.size()+(i)))
#define altstacktop(i)  (altstack.at(altstack.size()+(i)))
static inline void popstack(vector<valtype>& stack)
{
    if (stack.empty())
        throw runtime_error("popstack() : stack empty");
    stack.pop_back();
}


const char* GetTxnTypeName(txntype t)
{
    switch (t)
    {
    case TX_NONSTANDARD: return "nonstandard";
    case TX_PUBKEY: return "pubkey";
    case TX_PUBKEYHASH: return "pubkeyhash";
    case TX_SCRIPTHASH: return "scripthash";
    case TX_MULTISIG: return "multisig";
    }
    return NULL;
}


const char* GetOpName(opcodetype opcode)
{
    switch (opcode)
    {
    // push value
    case OP_0                      : return "0";
    case OP_PUSHDATA1              : return "OP_PUSHDATA1";
    case OP_PUSHDATA2              : return "OP_PUSHDATA2";
    case OP_PUSHDATA4              : return "OP_PUSHDATA4";
    case OP_1NEGATE                : return "-1";
    case OP_RESERVED               : return "OP_RESERVED";
    case OP_1                      : return "1";
    case OP_2                      : return "2";
    case OP_3                      : return "3";
    case OP_4                      : return "4";
    case OP_5                      : return "5";
    case OP_6                      : return "6";
    case OP_7                      : return "7";
    case OP_8                      : return "8";
    case OP_9                      : return "9";
    case OP_10                     : return "10";
    case OP_11                     : return "11";
    case OP_12                     : return "12";
    case OP_13                     : return "13";
    case OP_14                     : return "14";
    case OP_15                     : return "15";
    case OP_16                     : return "16";

    // control
    case OP_NOP                    : return "OP_NOP";
    case OP_VER                    : return "OP_VER";
    case OP_IF                     : return "OP_IF";
    case OP_NOTIF                  : return "OP_NOTIF";
    case OP_VERIF                  : return "OP_VERIF";
    case OP_VERNOTIF               : return "OP_VERNOTIF";
    case OP_ELSE                   : return "OP_ELSE";
    case OP_ENDIF                  : return "OP_ENDIF";
    case OP_VERIFY                 : return "OP_VERIFY";
    case OP_RETURN                 : return "OP_RETURN";

    // stack ops
    case OP_TOALTSTACK             : return "OP_TOALTSTACK";
    case OP_FROMALTSTACK           : return "OP_FROMALTSTACK";
    case OP_2DROP                  : return "OP_2DROP";
    case OP_2DUP                   : return "OP_2DUP";
    case OP_3DUP                   : return "OP_3DUP";
    case OP_2OVER                  : return "OP_2OVER";
    case OP_2ROT                   : return "OP_2ROT";
    case OP_2SWAP                  : return "OP_2SWAP";
    case OP_IFDUP                  : return "OP_IFDUP";
    case OP_DEPTH                  : return "OP_DEPTH";
    case OP_DROP                   : return "OP_DROP";
    case OP_DUP                    : return "OP_DUP";
    case OP_NIP                    : return "OP_NIP";
    case OP_OVER                   : return "OP_OVER";
    case OP_PICK                   : return "OP_PICK";
    case OP_ROLL                   : return "OP_ROLL";
    case OP_ROT                    : return "OP_ROT";
    case OP_SWAP                   : return "OP_SWAP";
    case OP_TUCK                   : return "OP_TUCK";

    // splice ops
    case OP_CAT                    : return "OP_CAT";
    case OP_SUBSTR                 : return "OP_SUBSTR";
    case OP_LEFT                   : return "OP_LEFT";
    case OP_RIGHT                  : return "OP_RIGHT";
    case OP_SIZE                   : return "OP_SIZE";

    // bit logic
    case OP_INVERT                 : return "OP_INVERT";
    case OP_AND                    : return "OP_AND";
    case OP_OR                     : return "OP_OR";
    case OP_XOR                    : return "OP_XOR";
    case OP_EQUAL                  : return "OP_EQUAL";
    case OP_EQUALVERIFY            : return "OP_EQUALVERIFY";
    case OP_RESERVED1              : return "OP_RESERVED1";
    case OP_RESERVED2              : return "OP_RESERVED2";

    // numeric
    case OP_1ADD                   : return "OP_1ADD";
    case OP_1SUB                   : return "OP_1SUB";
    case OP_2MUL                   : return "OP_2MUL";
    case OP_2DIV                   : return "OP_2DIV";
    case OP_NEGATE                 : return "OP_NEGATE";
    case OP_ABS                    : return "OP_ABS";
    case OP_NOT                    : return "OP_NOT";
    case OP_0NOTEQUAL              : return "OP_0NOTEQUAL";
    case OP_ADD                    : return "OP_ADD";
    case OP_SUB                    : return "OP_SUB";
    case OP_MUL                    : return "OP_MUL";
    case OP_DIV                    : return "OP_DIV";
    case OP_MOD                    : return "OP_MOD";
    case OP_LSHIFT                 : return "OP_LSHIFT";
    case OP_RSHIFT                 : return "OP_RSHIFT";
    case OP_BOOLAND                : return "OP_BOOLAND";
    case OP_BOOLOR                 : return "OP_BOOLOR";
    case OP_NUMEQUAL               : return "OP_NUMEQUAL";
    case OP_NUMEQUALVERIFY         : return "OP_NUMEQUALVERIFY";
    case OP_NUMNOTEQUAL            : return "OP_NUMNOTEQUAL";
    case OP_LESSTHAN               : return "OP_LESSTHAN";
    case OP_GREATERTHAN            : return "OP_GREATERTHAN";
    case OP_LESSTHANOREQUAL        : return "OP_LESSTHANOREQUAL";
    case OP_GREATERTHANOREQUAL     : return "OP_GREATERTHANOREQUAL";
    case OP_MIN                    : return "OP_MIN";
    case OP_MAX                    : return "OP_MAX";
    case OP_WITHIN                 : return "OP_WITHIN";

    // crypto
    case OP_RIPEMD160              : return "OP_RIPEMD160";
    case OP_SHA1                   : return "OP_SHA1";
    case OP_SHA256                 : return "OP_SHA256";
    case OP_HASH160                : return "OP_HASH160";
    case OP_HASH256                : return "OP_HASH256";
    case OP_CODESEPARATOR          : return "OP_CODESEPARATOR";
    case OP_CHECKSIG               : return "OP_CHECKSIG";
    case OP_CHECKSIGVERIFY         : return "OP_CHECKSIGVERIFY";
    case OP_CHECKMULTISIG          : return "OP_CHECKMULTISIG";
    case OP_CHECKMULTISIGVERIFY    : return "OP_CHECKMULTISIGVERIFY";

    // meta
    case OP_EVAL                   : return "OP_EVAL";

    // expanson
    case OP_NOP2                   : return "OP_NOP2";
    case OP_NOP3                   : return "OP_NOP3";
    case OP_NOP4                   : return "OP_NOP4";
    case OP_NOP5                   : return "OP_NOP5";
    case OP_NOP6                   : return "OP_NOP6";
    case OP_NOP7                   : return "OP_NOP7";
    case OP_NOP8                   : return "OP_NOP8";
    case OP_NOP9                   : return "OP_NOP9";
    case OP_NOP10                  : return "OP_NOP10";



    // template matching params
    case OP_SCRIPTHASH             : return "OP_SCRIPTHASH";
    case OP_PUBKEYHASH             : return "OP_PUBKEYHASH";
    case OP_PUBKEY                 : return "OP_PUBKEY";

    case OP_INVALIDOPCODE          : return "OP_INVALIDOPCODE";
    default:
        return "OP_UNKNOWN";
    }
}


//
// Returns true if script is valid.
//
bool EvalScriptInner(vector<vector<unsigned char> >& stack, const CScript& script, const CTransaction& txTo, unsigned int nIn, int nHashType,
                     CScript::const_iterator pbegincodehash, CScript::const_iterator pendcodehash, int& nOpCount, int& nSigOpCount, int nRecurseDepth)
{
    CAutoBN_CTX pctx;
    CScript::const_iterator pc = script.begin();
    CScript::const_iterator pend = script.end();
    opcodetype opcode;
    valtype vchPushValue;
    vector<bool> vfExec;
    vector<valtype> altstack;
    if (script.size() > 10000)
        return false;

    // Limit OP_EVAL recursion
    if (nRecurseDepth > 2)
        return false;

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

            //
            // Read instruction
            //
            if (!script.GetOp(pc, opcode, vchPushValue))
                return false;
            if (vchPushValue.size() > 520)
                return false;
            if (opcode > OP_16 && ++nOpCount > 201)
                return false;

            if (opcode == OP_CAT ||
                opcode == OP_SUBSTR ||
                opcode == OP_LEFT ||
                opcode == OP_RIGHT ||
                opcode == OP_INVERT ||
                opcode == OP_AND ||
                opcode == OP_OR ||
                opcode == OP_XOR ||
                opcode == OP_2MUL ||
                opcode == OP_2DIV ||
                opcode == OP_MUL ||
                opcode == OP_DIV ||
                opcode == OP_MOD ||
                opcode == OP_LSHIFT ||
                opcode == OP_RSHIFT)
                return false;

            if (fExec && 0 <= opcode && opcode <= OP_PUSHDATA4)
                stack.push_back(vchPushValue);
            else if (fExec || (OP_IF <= opcode && opcode <= OP_ENDIF))
            switch (opcode)
            {
                //
                // Push value
                //
                case OP_1NEGATE:
                case OP_1:
                case OP_2:
                case OP_3:
                case OP_4:
                case OP_5:
                case OP_6:
                case OP_7:
                case OP_8:
                case OP_9:
                case OP_10:
                case OP_11:
                case OP_12:
                case OP_13:
                case OP_14:
                case OP_15:
                case OP_16:
                {
                    // ( -- value)
                    CBigNum bn((int)opcode - (int)(OP_1 - 1));
                    stack.push_back(bn.getvch());
                }
                break;


                //
                // Control
                //
                case OP_NOP:
                case OP_NOP2: case OP_NOP3: case OP_NOP4: case OP_NOP5:
                case OP_NOP6: case OP_NOP7: case OP_NOP8: case OP_NOP9: case OP_NOP10:
                break;

                case OP_IF:
                case OP_NOTIF:
                {
                    // <expression> if [statements] [else [statements]] endif
                    bool fValue = false;
                    if (fExec)
                    {
                        if (stack.size() < 1)
                            return false;
                        valtype& vch = stacktop(-1);
                        fValue = CastToBool(vch);
                        if (opcode == OP_NOTIF)
                            fValue = !fValue;
                        popstack(stack);
                    }
                    vfExec.push_back(fValue);
                }
                break;

                case OP_ELSE:
                {
                    if (vfExec.empty())
                        return false;
                    vfExec.back() = !vfExec.back();
                }
                break;

                case OP_ENDIF:
                {
                    if (vfExec.empty())
                        return false;
                    vfExec.pop_back();
                }
                break;

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

                case OP_RETURN:
                {
                    return false;
                }
                break;


                //
                // Stack ops
                //
                case OP_TOALTSTACK:
                {
                    if (stack.size() < 1)
                        return false;
                    altstack.push_back(stacktop(-1));
                    popstack(stack);
                }
                break;

                case OP_FROMALTSTACK:
                {
                    if (altstack.size() < 1)
                        return false;
                    stack.push_back(altstacktop(-1));
                    popstack(altstack);
                }
                break;

                case OP_2DROP:
                {
                    // (x1 x2 -- )
                    if (stack.size() < 2)
                        return false;
                    popstack(stack);
                    popstack(stack);
                }
                break;

                case OP_2DUP:
                {
                    // (x1 x2 -- x1 x2 x1 x2)
                    if (stack.size() < 2)
                        return false;
                    valtype vch1 = stacktop(-2);
                    valtype vch2 = stacktop(-1);
                    stack.push_back(vch1);
                    stack.push_back(vch2);
                }
                break;

                case OP_3DUP:
                {
                    // (x1 x2 x3 -- x1 x2 x3 x1 x2 x3)
                    if (stack.size() < 3)
                        return false;
                    valtype vch1 = stacktop(-3);
                    valtype vch2 = stacktop(-2);
                    valtype vch3 = stacktop(-1);
                    stack.push_back(vch1);
                    stack.push_back(vch2);
                    stack.push_back(vch3);
                }
                break;

                case OP_2OVER:
                {
                    // (x1 x2 x3 x4 -- x1 x2 x3 x4 x1 x2)
                    if (stack.size() < 4)
                        return false;
                    valtype vch1 = stacktop(-4);
                    valtype vch2 = stacktop(-3);
                    stack.push_back(vch1);
                    stack.push_back(vch2);
                }
                break;

                case OP_2ROT:
                {
                    // (x1 x2 x3 x4 x5 x6 -- x3 x4 x5 x6 x1 x2)
                    if (stack.size() < 6)
                        return false;
                    valtype vch1 = stacktop(-6);
                    valtype vch2 = stacktop(-5);
                    stack.erase(stack.end()-6, stack.end()-4);
                    stack.push_back(vch1);
                    stack.push_back(vch2);
                }
                break;

                case OP_2SWAP:
                {
                    // (x1 x2 x3 x4 -- x3 x4 x1 x2)
                    if (stack.size() < 4)
                        return false;
                    swap(stacktop(-4), stacktop(-2));
                    swap(stacktop(-3), stacktop(-1));
                }
                break;

                case OP_IFDUP:
                {
                    // (x - 0 | x x)
                    if (stack.size() < 1)
                        return false;
                    valtype vch = stacktop(-1);
                    if (CastToBool(vch))
                        stack.push_back(vch);
                }
                break;

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

                case OP_DROP:
                {
                    // (x -- )
                    if (stack.size() < 1)
                        return false;
                    popstack(stack);
                }
                break;

                case OP_DUP:
                {
                    // (x -- x x)
                    if (stack.size() < 1)
                        return false;
                    valtype vch = stacktop(-1);
                    stack.push_back(vch);
                }
                break;

                case OP_NIP:
                {
                    // (x1 x2 -- x2)
                    if (stack.size() < 2)
                        return false;
                    stack.erase(stack.end() - 2);
                }
                break;

                case OP_OVER:
                {
                    // (x1 x2 -- x1 x2 x1)
                    if (stack.size() < 2)
                        return false;
                    valtype vch = stacktop(-2);
                    stack.push_back(vch);
                }
                break;

                case OP_PICK:
                case OP_ROLL:
                {
                    // (xn ... x2 x1 x0 n - xn ... x2 x1 x0 xn)
                    // (xn ... x2 x1 x0 n - ... x2 x1 x0 xn)
                    if (stack.size() < 2)
                        return false;
                    int n = CastToBigNum(stacktop(-1)).getint();
                    popstack(stack);
                    if (n < 0 || n >= stack.size())
                        return false;
                    valtype vch = stacktop(-n-1);
                    if (opcode == OP_ROLL)
                        stack.erase(stack.end()-n-1);
                    stack.push_back(vch);
                }
                break;

                case OP_ROT:
                {
                    // (x1 x2 x3 -- x2 x3 x1)
                    //  x2 x1 x3  after first swap
                    //  x2 x3 x1  after second swap
                    if (stack.size() < 3)
                        return false;
                    swap(stacktop(-3), stacktop(-2));
                    swap(stacktop(-2), stacktop(-1));
                }
                break;

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

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


                //
                // Splice ops
                //
                case OP_CAT:
                {
                    // (x1 x2 -- out)
                    if (stack.size() < 2)
                        return false;
                    valtype& vch1 = stacktop(-2);
                    valtype& vch2 = stacktop(-1);
                    vch1.insert(vch1.end(), vch2.begin(), vch2.end());
                    popstack(stack);
                    if (stacktop(-1).size() > 520)
                        return false;
                }
                break;

                case OP_SUBSTR:
                {
                    // (in begin size -- out)
                    if (stack.size() < 3)
                        return false;
                    valtype& vch = stacktop(-3);
                    int nBegin = CastToBigNum(stacktop(-2)).getint();
                    int nEnd = nBegin + CastToBigNum(stacktop(-1)).getint();
                    if (nBegin < 0 || nEnd < nBegin)
                        return false;
                    if (nBegin > vch.size())
                        nBegin = vch.size();
                    if (nEnd > vch.size())
                        nEnd = vch.size();
                    vch.erase(vch.begin() + nEnd, vch.end());
                    vch.erase(vch.begin(), vch.begin() + nBegin);
                    popstack(stack);
                    popstack(stack);
                }
                break;

                case OP_LEFT:
                case OP_RIGHT:
                {
                    // (in size -- out)
                    if (stack.size() < 2)
                        return false;
                    valtype& vch = stacktop(-2);
                    int nSize = CastToBigNum(stacktop(-1)).getint();
                    if (nSize < 0)
                        return false;
                    if (nSize > vch.size())
                        nSize = vch.size();
                    if (opcode == OP_LEFT)
                        vch.erase(vch.begin() + nSize, vch.end());
                    else
                        vch.erase(vch.begin(), vch.end() - nSize);
                    popstack(stack);
                }
                break;

                case OP_SIZE:
                {
                    // (in -- in size)
                    if (stack.size() < 1)
                        return false;
                    CBigNum bn(stacktop(-1).size());
                    stack.push_back(bn.getvch());
                }
                break;


                //
                // Bitwise logic
                //
                case OP_INVERT:
                {
                    // (in - out)
                    if (stack.size() < 1)
                        return false;
                    valtype& vch = stacktop(-1);
                    for (int i = 0; i < vch.size(); i++)
                        vch[i] = ~vch[i];
                }
                break;

                case OP_AND:
                case OP_OR:
                case OP_XOR:
                {
                    // (x1 x2 - out)
                    if (stack.size() < 2)
                        return false;
                    valtype& vch1 = stacktop(-2);
                    valtype& vch2 = stacktop(-1);
                    MakeSameSize(vch1, vch2);
                    if (opcode == OP_AND)
                    {
                        for (int i = 0; i < vch1.size(); i++)
                            vch1[i] &= vch2[i];
                    }
                    else if (opcode == OP_OR)
                    {
                        for (int i = 0; i < vch1.size(); i++)
                            vch1[i] |= vch2[i];
                    }
                    else if (opcode == OP_XOR)
                    {
                        for (int i = 0; i < vch1.size(); i++)
                            vch1[i] ^= vch2[i];
                    }
                    popstack(stack);
                }
                break;

                case OP_EQUAL:
                case OP_EQUALVERIFY:
                //case OP_NOTEQUAL: // use OP_NUMNOTEQUAL
                {
                    // (x1 x2 - bool)
                    if (stack.size() < 2)
                        return false;
                    valtype& vch1 = stacktop(-2);
                    valtype& vch2 = stacktop(-1);
                    bool fEqual = (vch1 == vch2);
                    // OP_NOTEQUAL is disabled because it would be too easy to say
                    // something like n != 1 and have some wiseguy pass in 1 with extra
                    // zero bytes after it (numerically, 0x01 == 0x0001 == 0x000001)
                    //if (opcode == OP_NOTEQUAL)
                    //    fEqual = !fEqual;
                    popstack(stack);
                    popstack(stack);
                    stack.push_back(fEqual ? vchTrue : vchFalse);
                    if (opcode == OP_EQUALVERIFY)
                    {
                        if (fEqual)
                            popstack(stack);
                        else
                            return false;
                    }
                }
                break;


                //
                // Numeric
                //
                case OP_1ADD:
                case OP_1SUB:
                case OP_2MUL:
                case OP_2DIV:
                case OP_NEGATE:
                case OP_ABS:
                case OP_NOT:
                case OP_0NOTEQUAL:
                {
                    // (in -- out)
                    if (stack.size() < 1)
                        return false;
                    CBigNum bn = CastToBigNum(stacktop(-1));
                    switch (opcode)
                    {
                    case OP_1ADD:       bn += bnOne; break;
                    case OP_1SUB:       bn -= bnOne; break;
                    case OP_2MUL:       bn <<= 1; break;
                    case OP_2DIV:       bn >>= 1; 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_MUL:
                case OP_DIV:
                case OP_MOD:
                case OP_LSHIFT:
                case OP_RSHIFT:
                case OP_BOOLAND:
                case OP_BOOLOR:
                case OP_NUMEQUAL:
                case OP_NUMEQUALVERIFY:
                case OP_NUMNOTEQUAL:
                case OP_LESSTHAN:
                case OP_GREATERTHAN:
                case OP_LESSTHANOREQUAL:
                case OP_GREATERTHANOREQUAL:
                case OP_MIN:
                case OP_MAX:
                {
                    // (x1 x2 -- out)
                    if (stack.size() < 2)
                        return false;
                    CBigNum bn1 = CastToBigNum(stacktop(-2));
                    CBigNum bn2 = CastToBigNum(stacktop(-1));
                    CBigNum bn;
                    switch (opcode)
                    {
                    case OP_ADD:
                        bn = bn1 + bn2;
                        break;

                    case OP_SUB:
                        bn = bn1 - bn2;
                        break;

                    case OP_MUL:
                        if (!BN_mul(&bn, &bn1, &bn2, pctx))
                            return false;
                        break;

                    case OP_DIV:
                        if (!BN_div(&bn, NULL, &bn1, &bn2, pctx))
                            return false;
                        break;

                    case OP_MOD:
                        if (!BN_mod(&bn, &bn1, &bn2, pctx))
                            return false;
                        break;

                    case OP_LSHIFT:
                        if (bn2 < bnZero || bn2 > CBigNum(2048))
                            return false;
                        bn = bn1 << bn2.getulong();
                        break;

                    case OP_RSHIFT:
                        if (bn2 < bnZero || bn2 > CBigNum(2048))
                            return false;
                        bn = bn1 >> bn2.getulong();
                        break;

                    case OP_BOOLAND:             bn = (bn1 != bnZero && bn2 != bnZero); break;
                    case OP_BOOLOR:              bn = (bn1 != bnZero || bn2 != bnZero); break;
                    case OP_NUMEQUAL:            bn = (bn1 == bn2); break;
                    case OP_NUMEQUALVERIFY:      bn = (bn1 == bn2); break;
                    case OP_NUMNOTEQUAL:         bn = (bn1 != bn2); break;
                    case OP_LESSTHAN:            bn = (bn1 < bn2); break;
                    case OP_GREATERTHAN:         bn = (bn1 > bn2); break;
                    case OP_LESSTHANOREQUAL:     bn = (bn1 <= bn2); break;
                    case OP_GREATERTHANOREQUAL:  bn = (bn1 >= bn2); break;
                    case OP_MIN:                 bn = (bn1 < bn2 ? bn1 : bn2); break;
                    case OP_MAX:                 bn = (bn1 > bn2 ? bn1 : bn2); break;
                    default:                     assert(!"invalid opcode"); break;
                    }
                    popstack(stack);
                    popstack(stack);
                    stack.push_back(bn.getvch());

                    if (opcode == OP_NUMEQUALVERIFY)
                    {
                        if (CastToBool(stacktop(-1)))
                            popstack(stack);
                        else
                            return false;
                    }
                }
                break;

                case OP_WITHIN:
                {
                    // (x min max -- out)
                    if (stack.size() < 3)
                        return false;
                    CBigNum bn1 = CastToBigNum(stacktop(-3));
                    CBigNum bn2 = CastToBigNum(stacktop(-2));
                    CBigNum bn3 = CastToBigNum(stacktop(-1));
                    bool fValue = (bn2 <= bn1 && bn1 < bn3);
                    popstack(stack);
                    popstack(stack);
                    popstack(stack);
                    stack.push_back(fValue ? vchTrue : vchFalse);
                }
                break;


                //
                // Crypto
                //
                case OP_RIPEMD160:
                case OP_SHA1:
                case OP_SHA256:
                case OP_HASH160:
                case OP_HASH256:
                {
                    // (in -- hash)
                    if (stack.size() < 1)
                        return false;
                    valtype& vch = stacktop(-1);
                    valtype vchHash((opcode == OP_RIPEMD160 || opcode == OP_SHA1 || opcode == OP_HASH160) ? 20 : 32);
                    if (opcode == OP_RIPEMD160)
                        RIPEMD160(&vch[0], vch.size(), &vchHash[0]);
                    else if (opcode == OP_SHA1)
                        SHA1(&vch[0], vch.size(), &vchHash[0]);
                    else if (opcode == OP_SHA256)
                        SHA256(&vch[0], vch.size(), &vchHash[0]);
                    else if (opcode == OP_HASH160)
                    {
                        uint160 hash160 = Hash160(vch);
                        memcpy(&vchHash[0], &hash160, sizeof(hash160));
                    }
                    else if (opcode == OP_HASH256)
                    {
                        uint256 hash = Hash(vch.begin(), vch.end());
                        memcpy(&vchHash[0], &hash, sizeof(hash));
                    }
                    popstack(stack);
                    stack.push_back(vchHash);
                }
                break;

                case OP_CODESEPARATOR:
                {
                    // Hash starts after the code separator
                    pbegincodehash = pc;
                }
                break;

                case OP_CHECKSIG:
                case OP_CHECKSIGVERIFY:
                {
                    // (sig pubkey -- bool)
                    if (stack.size() < 2)
                        return false;

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

                    ////// debug print
                    //PrintHex(vchSig.begin(), vchSig.end(), "sig: %s\n");
                    //PrintHex(vchPubKey.begin(), vchPubKey.end(), "pubkey: %s\n");

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

                    // Drop the signature, since there's no way for a signature to sign itself
                    scriptCode.FindAndDelete(CScript(vchSig));

                    bool fSuccess = CheckSig(vchSig, vchPubKey, scriptCode, txTo, nIn, nHashType);
                    nSigOpCount++;

                    popstack(stack);
                    popstack(stack);
                    stack.push_back(fSuccess ? vchTrue : vchFalse);
                    if (opcode == OP_CHECKSIGVERIFY)
                    {
                        if (fSuccess)
                            popstack(stack);
                        else
                            return false;
                    }
                }
                break;

                case OP_CHECKMULTISIG:
                case OP_CHECKMULTISIGVERIFY:
                {
                    // ([sig ...] num_of_signatures [pubkey ...] num_of_pubkeys -- bool)

                    int i = 1;
                    if (stack.size() < i)
                        return false;

                    int nKeysCount = CastToBigNum(stacktop(-i)).getint();
                    if (nKeysCount < 0 || nKeysCount > 20)
                        return false;
                    nOpCount += nKeysCount;
                    if (nOpCount > 201)
                        return false;
                    int ikey = ++i;
                    i += nKeysCount;
                    if (stack.size() < i)
                        return false;

                    int nSigsCount = CastToBigNum(stacktop(-i)).getint();
                    if (nSigsCount < 0 || nSigsCount > nKeysCount)
                        return false;
                    int isig = ++i;
                    i += nSigsCount;
                    if (stack.size() < i)
                        return false;

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

                    // Drop the signatures, since there's no way for a signature to sign itself
                    for (int k = 0; k < nSigsCount; k++)
                    {
                        valtype& vchSig = stacktop(-isig-k);
                        scriptCode.FindAndDelete(CScript(vchSig));
                    }

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

                        // Check signature
                        if (CheckSig(vchSig, vchPubKey, scriptCode, txTo, nIn, nHashType))
                        {
                            isig++;
                            nSigsCount--;
                        }
                        ikey++;
                        nKeysCount--;
                        nSigOpCount++;

                        // If there are more signatures left than keys left,
                        // then too many signatures have failed
                        if (nSigsCount > nKeysCount)
                            fSuccess = false;
                    }

                    while (i-- > 0)
                        popstack(stack);
                    stack.push_back(fSuccess ? vchTrue : vchFalse);

                    if (opcode == OP_CHECKMULTISIGVERIFY)
                    {
                        if (fSuccess)
                            popstack(stack);
                        else
                            return false;
                    }
                }
                break;

                case OP_EVAL:
                {
                    // This code should be removed when OP_EVAL has
                    // a majority of hashing power on the network.
                    // OP_EVAL behaves just like OP_NOP until
                    // opevaltime :
                    if (!fTestNet || fDebug)
                    {
                        // 1328054400 is Feb 1, 2012
                        int64 nEvalSwitchTime = GetArg("opevaltime", 1328054400);
                        if (GetTime() < nEvalSwitchTime)
                            break;
                    }

                    // Evaluate the top item on the stack as a Script
                    // [serialized script ] -- [result(s) of executing script]
                    if (stack.size() < 1)
                        return false;
                    valtype& vchScript = stacktop(-1);
                    CScript subscript(vchScript.begin(), vchScript.end());
                    popstack(stack);
                    
                    // Codeseparators not allowed
                    if (subscript.Find(OP_CODESEPARATOR))
                        return false;

                    if (!EvalScriptInner(stack, subscript, txTo, nIn, nHashType,
                                         pbegincodehash, pendcodehash, nOpCount, nSigOpCount, nRecurseDepth++))
                        return false;
                }
                break;

                default:
                    return false;
            }

            // Size limits
            if (stack.size() + altstack.size() > 1000)
                return false;
        }
    }
    catch (...)
    {
        return false;
    }


    if (!vfExec.empty())
        return false;

    return true;
}

bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script,
                const CTransaction& txTo, unsigned int nIn, int nHashType, int& nSigOpCountRet)
{
    CScript::const_iterator pbegincodehash = script.begin();
    CScript::const_iterator pendcodehash = script.end();

    int nOpCount = 0;
    return EvalScriptInner(stack, script, txTo, nIn, nHashType, pbegincodehash, pendcodehash,
                           nOpCount, nSigOpCountRet, 0);
}









uint256 SignatureHash(CScript scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType)
{
    if (nIn >= txTo.vin.size())
    {
        printf("ERROR: SignatureHash() : nIn=%d out of range\n", nIn);
        return 1;
    }
    CTransaction txTmp(txTo);

    // In case concatenating two scripts ends up with two codeseparators,
    // or an extra one at the end, this prevents all those possible incompatibilities.
    scriptCode.FindAndDelete(CScript(OP_CODESEPARATOR));

    // Blank out other inputs' signatures
    for (int i = 0; i < txTmp.vin.size(); i++)
        txTmp.vin[i].scriptSig = CScript();
    txTmp.vin[nIn].scriptSig = scriptCode;

    // Blank out some of the outputs
    if ((nHashType & 0x1f) == SIGHASH_NONE)
    {
        // Wildcard payee
        txTmp.vout.clear();

        // Let the others update at will
        for (int i = 0; i < txTmp.vin.size(); i++)
            if (i != nIn)
                txTmp.vin[i].nSequence = 0;
    }
    else if ((nHashType & 0x1f) == SIGHASH_SINGLE)
    {
        // Only lockin the txout payee at same index as txin
        unsigned int nOut = nIn;
        if (nOut >= txTmp.vout.size())
        {
            printf("ERROR: SignatureHash() : nOut=%d out of range\n", nOut);
            return 1;
        }
        txTmp.vout.resize(nOut+1);
        for (int i = 0; i < nOut; i++)
            txTmp.vout[i].SetNull();

        // Let the others update at will
        for (int i = 0; i < txTmp.vin.size(); i++)
            if (i != nIn)
                txTmp.vin[i].nSequence = 0;
    }

    // Blank out other inputs completely, not recommended for open transactions
    if (nHashType & SIGHASH_ANYONECANPAY)
    {
        txTmp.vin[0] = txTmp.vin[nIn];
        txTmp.vin.resize(1);
    }

    // Serialize and hash
    CDataStream ss(SER_GETHASH);
    ss.reserve(10000);
    ss << txTmp << nHashType;
    return Hash(ss.begin(), ss.end());
}


bool CheckSig(vector<unsigned char> vchSig, vector<unsigned char> vchPubKey, CScript scriptCode,
              const CTransaction& txTo, unsigned int nIn, int nHashType)
{
    CKey key;
    if (!key.SetPubKey(vchPubKey))
        return false;

    // Hash type is one byte tacked on to the end of the signature
    if (vchSig.empty())
        return false;
    if (nHashType == 0)
        nHashType = vchSig.back();
    else if (nHashType != vchSig.back())
        return false;
    vchSig.pop_back();

    return key.Verify(SignatureHash(scriptCode, txTo, nIn, nHashType), vchSig);
}









//
// Return public keys or hashes from scriptPubKey, for 'standard' transaction types.
//
bool Solver(const CScript& scriptPubKey, txntype& typeRet, vector<vector<unsigned char> >& vSolutionsRet)
{
    // Templates
    static map<txntype, CScript> mTemplates;
    if (mTemplates.empty())
    {
        // Standard tx, sender provides pubkey, receiver adds signature
        mTemplates.insert(make_pair(TX_PUBKEY, CScript() << OP_PUBKEY << OP_CHECKSIG));

        // Bitcoin address tx, sender provides hash of pubkey, receiver provides signature and pubkey
        mTemplates.insert(make_pair(TX_PUBKEYHASH, CScript() << OP_DUP << OP_HASH160 << OP_PUBKEYHASH << OP_EQUALVERIFY << OP_CHECKSIG));

        // Sender provides N pubkeys, receivers provides M signatures
        mTemplates.insert(make_pair(TX_MULTISIG, CScript() << OP_SMALLINTEGER << OP_PUBKEYS << OP_SMALLINTEGER << OP_CHECKMULTISIG));

        // Sender provides script hash, receiver provides script and
        // as many signatures as required to satisfy script
        mTemplates.insert(make_pair(TX_SCRIPTHASH, CScript() << OP_DUP << OP_HASH160 << OP_SCRIPTHASH << OP_EQUALVERIFY << OP_EVAL));
    }

    // Scan templates
    const CScript& script1 = scriptPubKey;
    BOOST_FOREACH(const PAIRTYPE(txntype, CScript)& tplate, mTemplates)
    {
        const CScript& script2 = tplate.second;
        vSolutionsRet.clear();

        opcodetype opcode1, opcode2;
        vector<unsigned char> vch1, vch2;

        // Compare
        CScript::const_iterator pc1 = script1.begin();
        CScript::const_iterator pc2 = script2.begin();
        loop
        {
            if (pc1 == script1.end() && pc2 == script2.end())
            {
                // Found a match
                typeRet = tplate.first;
                if (typeRet == TX_MULTISIG)
                {
                    // Additional checks for TX_MULTISIG:
                    unsigned char m = vSolutionsRet.front()[0];
                    unsigned char n = vSolutionsRet.back()[0];
                    if (m < 1 || n < 1 || m > n || vSolutionsRet.size()-2 != n)
                        return false;
                }
                return true;
            }
            if (!script1.GetOp(pc1, opcode1, vch1))
                break;
            if (!script2.GetOp(pc2, opcode2, vch2))
                break;

            // Template matching opcodes:
            if (opcode2 == OP_PUBKEYS)
            {
                while (vch1.size() >= 33 && vch1.size() <= 120)
                {
                    vSolutionsRet.push_back(vch1);
                    if (!script1.GetOp(pc1, opcode1, vch1))
                        break;
                }
                if (!script2.GetOp(pc2, opcode2, vch2))
                    break;
                // Normal situation is to fall through
                // to other if/else statments
            }

            if (opcode2 == OP_PUBKEY)
            {
                if (vch1.size() < 33 || vch1.size() > 120)
                    break;
                vSolutionsRet.push_back(vch1);
            }
            else if (opcode2 == OP_PUBKEYHASH)
            {
                if (vch1.size() != sizeof(uint160))
                    break;
                vSolutionsRet.push_back(vch1);
            }
            else if (opcode2 == OP_SCRIPTHASH)
            {
                if (vch1.size() != sizeof(uint160))
                    break;
                vSolutionsRet.push_back(vch1);
            }
            else if (opcode2 == OP_SMALLINTEGER)
            {   // Single-byte small integer pushed onto vSolutions
                if (opcode1 == OP_0 ||
                    (opcode1 >= OP_1 && opcode1 <= OP_16))
                {
                    char n = (char)CScript::DecodeOP_N(opcode1);
                    vSolutionsRet.push_back(valtype(1, n));
                }
                else
                    break;
            }
            else if (opcode1 != opcode2 || vch1 != vch2)
            {
                // Others must match exactly
                break;
            }
        }
    }

    vSolutionsRet.clear();
    typeRet = TX_NONSTANDARD;
    return false;
}


bool Sign1(const CBitcoinAddress& address, const CKeyStore& keystore, uint256 hash, int nHashType, CScript& scriptSigRet)
{
    CKey key;
    if (!keystore.GetKey(address, key))
        return false;

    vector<unsigned char> vchSig;
    if (!key.Sign(hash, vchSig))
        return false;
    vchSig.push_back((unsigned char)nHashType);
    scriptSigRet << vchSig;

    return true;
}

bool SignN(const vector<valtype>& multisigdata, const CKeyStore& keystore, uint256 hash, int nHashType, CScript& scriptSigRet)
{
    int nSigned = 0;
    int nRequired = multisigdata.front()[0];
    for (vector<valtype>::const_iterator it = multisigdata.begin()+1; it != multisigdata.begin()+multisigdata.size()-1; it++)
    {
        const valtype& pubkey = *it;
        CBitcoinAddress address;
        address.SetPubKey(pubkey);
        if (Sign1(address, keystore, hash, nHashType, scriptSigRet))
        {
            ++nSigned;
            if (nSigned == nRequired) break;
        }
    }
    return nSigned==nRequired;
}

//
// Sign scriptPubKey with private keys stored in keystore, given transaction hash and hash type.
// Signatures are returned in scriptSigRet (or returns false if scriptPubKey can't be signed).
// Returns true if scriptPubKey could be completely satisified.
//
bool Solver(const CKeyStore& keystore, const CScript& scriptPubKey, uint256 hash, int nHashType, CScript& scriptSigRet)
{
    scriptSigRet.clear();

    txntype whichType;
    vector<valtype> vSolutions;
    if (!Solver(scriptPubKey, whichType, vSolutions))
        return false;

    CBitcoinAddress address;
    valtype subscript;
    switch (whichType)
    {
    case TX_NONSTANDARD:
        return false;
    case TX_PUBKEY:
        address.SetPubKey(vSolutions[0]);
        return Sign1(address, keystore, hash, nHashType, scriptSigRet);
    case TX_PUBKEYHASH:
        address.SetHash160(uint160(vSolutions[0]));
        if (!Sign1(address, keystore, hash, nHashType, scriptSigRet))
            return false;
        else
        {
            valtype vch;
            keystore.GetPubKey(address, vch);
            scriptSigRet << vch;
        }
        break;
    case TX_SCRIPTHASH:
        if (!keystore.GetCScript(uint160(vSolutions[0]), subscript))
            return false;
        if (!Solver(keystore, CScript(subscript.begin(), subscript.end()), hash, nHashType, scriptSigRet))
            return false;
        if (hash != 0)
            scriptSigRet << subscript; // signatures AND serialized script
        break;
    case TX_MULTISIG:
        scriptSigRet << OP_0; // workaround CHECKMULTISIG bug
        return (SignN(vSolutions, keystore, hash, nHashType, scriptSigRet));
    }
    return true;
}


bool IsStandard(const CScript& scriptPubKey)
{
    vector<valtype> vSolutions;
    txntype whichType;
    if (!Solver(scriptPubKey, whichType, vSolutions))
        return false;

    if (whichType == TX_MULTISIG)
    {
        unsigned char m = vSolutions.front()[0];
        unsigned char n = vSolutions.back()[0];
        // Support up to x-of-3 multisig txns as standard
        if (n < 1 || n > 3)
            return false;
        if (m < 1 || m > n)
            return false;
    }

    return whichType != TX_NONSTANDARD;
}


int HaveKeys(const vector<valtype>& pubkeys, const CKeyStore& keystore)
{
    int nResult = 0;
    BOOST_FOREACH(const valtype& pubkey, pubkeys)
    {
        CBitcoinAddress address;
        address.SetPubKey(pubkey);
        if (keystore.HaveKey(address))
            ++nResult;
    }
    return nResult;
}

bool IsMine(const CKeyStore &keystore, const CScript& scriptPubKey)
{
    vector<valtype> vSolutions;
    txntype whichType;
    if (!Solver(scriptPubKey, whichType, vSolutions))
        return false;

    CBitcoinAddress address;
    switch (whichType)
    {
    case TX_NONSTANDARD:
        return false;
    case TX_PUBKEY:
        address.SetPubKey(vSolutions[0]);
        return keystore.HaveKey(address);
    case TX_PUBKEYHASH:
        address.SetHash160(uint160(vSolutions[0]));
        return keystore.HaveKey(address);
    case TX_SCRIPTHASH:
    {
        valtype subscript;
        if (!keystore.GetCScript(uint160(vSolutions[0]), subscript))
            return false;
        return IsMine(keystore, CScript(subscript.begin(), subscript.end()));
    }
    case TX_MULTISIG:
    {
        // Only consider transactions "mine" if we own ALL the
        // keys involved. multi-signature transactions that are
        // partially owned (somebody else has a key that can spend
        // them) enable spend-out-from-under-you attacks, especially
        // in shared-wallet situations.
        vector<valtype> keys(vSolutions.begin()+1, vSolutions.begin()+vSolutions.size()-1);
        return HaveKeys(vSolutions, keystore);
    }
    }
    return false;
}

bool ExtractAddress(const CScript& scriptPubKey, const CKeyStore* keystore, CBitcoinAddress& addressRet)
{
    vector<valtype> vSolutions;
    txntype whichType;
    if (!Solver(scriptPubKey, whichType, vSolutions))
        return false;

    if (whichType == TX_PUBKEY)
    {
        addressRet.SetPubKey(vSolutions[0]);
        return true;
    }
    else if (whichType == TX_PUBKEYHASH)
    {
        addressRet.SetHash160(uint160(vSolutions[0]));
        return true;
    }
    else if (whichType == TX_SCRIPTHASH)
    {
        addressRet.SetScriptHash160(uint160(vSolutions[0]));
        return true;
    }
    // Multisig txns have more than one address...
    return false;
}

bool ExtractAddresses(const CScript& scriptPubKey, const CKeyStore* keystore, txntype& typeRet, vector<CBitcoinAddress>& addressRet, int& nRequiredRet)
{
    addressRet.clear();
    typeRet = TX_NONSTANDARD;
    vector<valtype> vSolutions;
    if (!Solver(scriptPubKey, typeRet, vSolutions))
        return false;

    if (typeRet == TX_MULTISIG)
    {
        nRequiredRet = vSolutions.front()[0];
        int n = vSolutions.back()[0];
        for (vector<valtype>::const_iterator it = vSolutions.begin()+1; it != vSolutions.begin()+vSolutions.size()-1; it++)
        {
            CBitcoinAddress address;
            address.SetPubKey(*it);
            addressRet.push_back(address);
        }
    }
    else
    {
        nRequiredRet = 1;
        CBitcoinAddress address;
        if (typeRet == TX_PUBKEYHASH)
            address.SetHash160(uint160(vSolutions.front()));
        else if (typeRet == TX_SCRIPTHASH)
            address.SetScriptHash160(uint160(vSolutions.front()));
        else if (typeRet == TX_PUBKEY)
            address.SetPubKey(vSolutions.front());
        addressRet.push_back(address);
    }

    return true;
}

bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, const CTransaction& txTo, unsigned int nIn, int& nSigOpCountRet, int nHashType)
{
    vector<vector<unsigned char> > stack;
    if (!EvalScript(stack, scriptSig, txTo, nIn, nHashType, nSigOpCountRet))
        return false;
    if (!EvalScript(stack, scriptPubKey, txTo, nIn, nHashType, nSigOpCountRet))
        return false;
    if (stack.empty())
        return false;
    bool fResult = CastToBool(stack.back());

    // This code should be removed when a compatibility-breaking block chain split has passed.
    // Special check for OP_EVAL backwards-compatibility: if scriptPubKey or scriptSig contains
    // OP_EVAL, then result must be identical if OP_EVAL is treated as a no-op:
    if (scriptSig.Find(OP_EVAL)+scriptPubKey.Find(OP_EVAL) > 0)
    {
        int nUnused = 0;
        stack.clear();
        CScript sigCopy = scriptSig;
        sigCopy.FindAndDelete(CScript(OP_EVAL));
        CScript pubKeyCopy = scriptPubKey;
        pubKeyCopy.FindAndDelete(CScript(OP_EVAL));

        if (!EvalScript(stack, sigCopy, txTo, nIn, nHashType, nUnused))
            return false;
        if (!EvalScript(stack, pubKeyCopy, txTo, nIn, nHashType, nUnused))
            return false;
        if (stack.empty())
            return false;
        if (fResult != CastToBool(stack.back()))
            return false;
    }

    return fResult;
}


bool SignSignature(const CKeyStore &keystore, const CTransaction& txFrom, CTransaction& txTo, unsigned int nIn, int nHashType, CScript scriptPrereq)
{
    assert(nIn < txTo.vin.size());
    CTxIn& txin = txTo.vin[nIn];
    assert(txin.prevout.n < txFrom.vout.size());
    const CTxOut& txout = txFrom.vout[txin.prevout.n];

    // Leave out the signature from the hash, since a signature can't sign itself.
    // The checksig op will also drop the signatures from its hash.
    uint256 hash = SignatureHash(scriptPrereq + txout.scriptPubKey, txTo, nIn, nHashType);

    if (!Solver(keystore, txout.scriptPubKey, hash, nHashType, txin.scriptSig))
        return false;

    txin.scriptSig = scriptPrereq + txin.scriptSig;

    // Test solution
    int nUnused = 0;
    if (scriptPrereq.empty())
        if (!VerifyScript(txin.scriptSig, txout.scriptPubKey, txTo, nIn, nUnused, 0))
            return false;

    return true;
}


bool VerifySignature(const CTransaction& txFrom, const CTransaction& txTo, unsigned int nIn, int& nSigOpCountRet, int nHashType)
{
    assert(nIn < txTo.vin.size());
    const CTxIn& txin = txTo.vin[nIn];
    if (txin.prevout.n >= txFrom.vout.size())
        return false;
    const CTxOut& txout = txFrom.vout[txin.prevout.n];

    if (txin.prevout.hash != txFrom.GetHash())
        return false;

    if (!VerifyScript(txin.scriptSig, txout.scriptPubKey, txTo, nIn, nSigOpCountRet, nHashType))
        return false;

    return true;
}

void CScript::SetBitcoinAddress(const CBitcoinAddress& address)
{
    this->clear();
    if (address.IsScript())
        *this << OP_DUP << OP_HASH160 << address.GetHash160() << OP_EQUALVERIFY << OP_EVAL;
    else
        *this << OP_DUP << OP_HASH160 << address.GetHash160() << OP_EQUALVERIFY << OP_CHECKSIG;
}

void CScript::SetMultisig(int nRequired, const std::vector<CKey>& keys)
{
    this->clear();

    *this << EncodeOP_N(nRequired);
    BOOST_FOREACH(const CKey& key, keys)
        *this << key.GetPubKey();
    *this << EncodeOP_N(keys.size()) << OP_CHECKMULTISIG;
}

void CScript::SetEval(const CScript& subscript)
{
    assert(!subscript.empty());
    uint160 subscriptHash = Hash160(subscript);
    this->clear();
    *this << OP_DUP << OP_HASH160 << subscriptHash << OP_EQUALVERIFY << OP_EVAL;
}