Add FundTransaction method to wallet

Some code stolen from Jonas Schnelli <jonas.schnelli@include7.ch>

src/wallet/wallet.cpp

@@ -1509,7 +1509,7 @@ void CWallet::AvailableCoins(vector<COutput>& vCoins, bool fOnlyConfirmed, const
                 isminetype mine = IsMine(pcoin->vout[i]);
                 if (!(IsSpent(wtxid, i)) && mine != ISMINE_NO &&
                     !IsLockedCoin((*it).first, i) && (pcoin->vout[i].nValue > 0 || fIncludeZeroValue) &&
-                    (!coinControl || !coinControl->HasSelected() || coinControl->IsSelected((*it).first, i)))
+                    (!coinControl || !coinControl->HasSelected() || coinControl->fAllowOtherInputs || coinControl->IsSelected((*it).first, i)))
                         vCoins.push_back(COutput(pcoin, i, nDepth, (mine & ISMINE_SPENDABLE) != ISMINE_NO));
             }
         }
@@ -1669,7 +1669,7 @@ bool CWallet::SelectCoins(const CAmount& nTargetValue, set<pair<const CWalletTx*
     AvailableCoins(vCoins, true, coinControl);
 
     // coin control -> return all selected outputs (we want all selected to go into the transaction for sure)
-    if (coinControl && coinControl->HasSelected())
+    if (coinControl && coinControl->HasSelected() && !coinControl->fAllowOtherInputs)
     {
         BOOST_FOREACH(const COutput& out, vCoins)
         {
@@ -1681,13 +1681,96 @@ bool CWallet::SelectCoins(const CAmount& nTargetValue, set<pair<const CWalletTx*
         return (nValueRet >= nTargetValue);
     }
 
-    return (SelectCoinsMinConf(nTargetValue, 1, 6, vCoins, setCoinsRet, nValueRet) ||
+    // calculate value from preset inputs and store them
-            SelectCoinsMinConf(nTargetValue, 1, 1, vCoins, setCoinsRet, nValueRet) ||
+    set<pair<const CWalletTx*, uint32_t> > setPresetCoins;
-            (bSpendZeroConfChange && SelectCoinsMinConf(nTargetValue, 0, 1, vCoins, setCoinsRet, nValueRet)));
+    CAmount nValueFromPresetInputs = 0;
+
+    std::vector<COutPoint> vPresetInputs;
+    if (coinControl)
+        coinControl->ListSelected(vPresetInputs);
+    BOOST_FOREACH(const COutPoint& outpoint, vPresetInputs)
+    {
+        map<uint256, CWalletTx>::const_iterator it = mapWallet.find(outpoint.hash);
+        if (it != mapWallet.end())
+        {
+            const CWalletTx* pcoin = &it->second;
+            // Clearly invalid input, fail
+            if (pcoin->vout.size() <= outpoint.n)
+                return false;
+            nValueFromPresetInputs += pcoin->vout[outpoint.n].nValue;
+            setPresetCoins.insert(make_pair(pcoin, outpoint.n));
+        } else
+            return false; // TODO: Allow non-wallet inputs
     }
 
-bool CWallet::CreateTransaction(const vector<CRecipient>& vecSend,
+    // remove preset inputs from vCoins
-                                CWalletTx& wtxNew, CReserveKey& reservekey, CAmount& nFeeRet, int& nChangePosRet, std::string& strFailReason, const CCoinControl* coinControl)
+    for (vector<COutput>::iterator it = vCoins.begin(); it != vCoins.end() && coinControl && coinControl->HasSelected();)
+    {
+        if (setPresetCoins.count(make_pair(it->tx, it->i)))
+            it = vCoins.erase(it);
+        else
+            ++it;
+    }
+
+    bool res = nTargetValue <= nValueFromPresetInputs ||
+        SelectCoinsMinConf(nTargetValue - nValueFromPresetInputs, 1, 6, vCoins, setCoinsRet, nValueRet) ||
+        SelectCoinsMinConf(nTargetValue - nValueFromPresetInputs, 1, 1, vCoins, setCoinsRet, nValueRet) ||
+        (bSpendZeroConfChange && SelectCoinsMinConf(nTargetValue - nValueFromPresetInputs, 0, 1, vCoins, setCoinsRet, nValueRet));
+
+    // because SelectCoinsMinConf clears the setCoinsRet, we now add the possible inputs to the coinset
+    setCoinsRet.insert(setPresetCoins.begin(), setPresetCoins.end());
+
+    // add preset inputs to the total value selected
+    nValueRet += nValueFromPresetInputs;
+
+    return res;
+}
+
+bool CWallet::FundTransaction(CMutableTransaction& tx, CAmount &nFeeRet, int& nChangePosRet, std::string& strFailReason)
+{
+    vector<CRecipient> vecSend;
+
+    // Turn the txout set into a CRecipient vector
+    BOOST_FOREACH(const CTxOut& txOut, tx.vout)
+    {
+        CRecipient recipient = {txOut.scriptPubKey, txOut.nValue, false};
+        vecSend.push_back(recipient);
+    }
+
+    CCoinControl coinControl;
+    coinControl.fAllowOtherInputs = true;
+    BOOST_FOREACH(const CTxIn& txin, tx.vin)
+        coinControl.Select(txin.prevout);
+
+    CReserveKey reservekey(this);
+    CWalletTx wtx;
+    if (!CreateTransaction(vecSend, wtx, reservekey, nFeeRet, nChangePosRet, strFailReason, &coinControl, false))
+        return false;
+
+    if (nChangePosRet != -1)
+        tx.vout.insert(tx.vout.begin() + nChangePosRet, wtx.vout[nChangePosRet]);
+
+    // Add new txins (keeping original txin scriptSig/order)
+    BOOST_FOREACH(const CTxIn& txin, wtx.vin)
+    {
+        bool found = false;
+        BOOST_FOREACH(const CTxIn& origTxIn, tx.vin)
+        {
+            if (txin.prevout.hash == origTxIn.prevout.hash && txin.prevout.n == origTxIn.prevout.n)
+            {
+                found = true;
+                break;
+            }
+        }
+        if (!found)
+            tx.vin.push_back(txin);
+    }
+
+    return true;
+}
+
+bool CWallet::CreateTransaction(const vector<CRecipient>& vecSend, CWalletTx& wtxNew, CReserveKey& reservekey, CAmount& nFeeRet,
+                                int& nChangePosRet, std::string& strFailReason, const CCoinControl* coinControl, bool sign)
 {
     CAmount nValue = 0;
     unsigned int nSubtractFeeFromAmount = 0;
@@ -1890,23 +1973,43 @@ bool CWallet::CreateTransaction(const vector<CRecipient>& vecSend,
 
                 // Sign
                 int nIn = 0;
+                CTransaction txNewConst(txNew);
                 BOOST_FOREACH(const PAIRTYPE(const CWalletTx*,unsigned int)& coin, setCoins)
-                    if (!SignSignature(*this, *coin.first, txNew, nIn++))
+                {
+                    bool signSuccess;
+                    const CScript& scriptPubKey = coin.first->vout[coin.second].scriptPubKey;
+                    CScript& scriptSigRes = txNew.vin[nIn].scriptSig;
+                    if (sign)
+                        signSuccess = ProduceSignature(TransactionSignatureCreator(this, &txNewConst, nIn, SIGHASH_ALL), scriptPubKey, scriptSigRes);
+                    else
+                        signSuccess = ProduceSignature(DummySignatureCreator(this), scriptPubKey, scriptSigRes);
+
+                    if (!signSuccess)
                     {
                         strFailReason = _("Signing transaction failed");
                         return false;
                     }
+                    nIn++;
+                }
+
+                unsigned int nBytes = ::GetSerializeSize(txNew, SER_NETWORK, PROTOCOL_VERSION);
+
+                // Remove scriptSigs if we used dummy signatures for fee calculation
+                if (!sign) {
+                    BOOST_FOREACH (CTxIn& vin, txNew.vin)
+                        vin.scriptSig = CScript();
+                }
 
                 // Embed the constructed transaction data in wtxNew.
                 *static_cast<CTransaction*>(&wtxNew) = CTransaction(txNew);
 
                 // Limit size
-                unsigned int nBytes = ::GetSerializeSize(*(CTransaction*)&wtxNew, SER_NETWORK, PROTOCOL_VERSION);
                 if (nBytes >= MAX_STANDARD_TX_SIZE)
                 {
                     strFailReason = _("Transaction too large");
                     return false;
                 }
+
                 dPriority = wtxNew.ComputePriority(dPriority, nBytes);
 
                 // Can we complete this as a free transaction?

src/wallet/wallet.h

@@ -625,8 +625,9 @@ public:
     CAmount GetWatchOnlyBalance() const;
     CAmount GetUnconfirmedWatchOnlyBalance() const;
     CAmount GetImmatureWatchOnlyBalance() const;
-    bool CreateTransaction(const std::vector<CRecipient>& vecSend,
+    bool FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, int& nChangePosRet, std::string& strFailReason);
-                           CWalletTx& wtxNew, CReserveKey& reservekey, CAmount& nFeeRet, int& nChangePosRet, std::string& strFailReason, const CCoinControl *coinControl = NULL);
+    bool CreateTransaction(const std::vector<CRecipient>& vecSend, CWalletTx& wtxNew, CReserveKey& reservekey, CAmount& nFeeRet, int& nChangePosRet,
+                           std::string& strFailReason, const CCoinControl *coinControl = NULL, bool sign = true);
     bool CommitTransaction(CWalletTx& wtxNew, CReserveKey& reservekey);
 
     static CFeeRate minTxFee;