[Wallet] Combine change to output when possible & provide it in autoc…

…ombine

-When a change address is specified through coincontrol and this adress
is already receiving an output, we now add the change to this output
-Change of autocombinedust goes to the adress being combined instead of
a change address

src/wallet.cpp

@@ -2713,11 +2713,25 @@ bool CWallet::CreateTransaction(const vector<pair<CScript, CAmount> >& vecSend,
  // TODO: pass in scriptChange instead of reservekey so
  // change transaction isn't always pay-to-pivx-address
  CScript scriptChange;
+ bool combineChange = false;
 
  // coin control: send change to custom address
- if (coinControl && !boost::get<CNoDestination>(&coinControl->destChange))
+ if (coinControl && !boost::get<CNoDestination>(&coinControl->destChange)) {
  scriptChange = GetScriptForDestination(coinControl->destChange);
 
+ vector<CTxOut>::iterator it = txNew.vout.begin();
+ for (; it != txNew.vout.end();) {
+ if (scriptChange == it->scriptPubKey) {
+ it->nValue += nChange;
+ nChange = 0;
+ reservekey.ReturnKey();
+ combineChange = true;
+ break;
+ }
+ ++it;
+ }
+ }
+
  // no coin control: send change to newly generated address
  else {
  // Note: We use a new key here to keep it from being obvious which side is the change.
@@ -2736,18 +2750,20 @@ bool CWallet::CreateTransaction(const vector<pair<CScript, CAmount> >& vecSend,
  scriptChange = GetScriptForDestination(vchPubKey.GetID());
  }
 
- CTxOut newTxOut(nChange, scriptChange);
-
- // Never create dust outputs; if we would, just
- // add the dust to the fee.
- if (newTxOut.IsDust(::minRelayTxFee)) {
- nFeeRet += nChange;
- nChange = 0;
- reservekey.ReturnKey();
- } else {
- // Insert change txn at random position:
- vector<CTxOut>::iterator position = txNew.vout.begin() + GetRandInt(txNew.vout.size() + 1);
- txNew.vout.insert(position, newTxOut);
+ if (!combineChange) {
+ CTxOut newTxOut(nChange, scriptChange);
+
+ // Never create dust outputs; if we would, just
+ // add the dust to the fee.
+ if (newTxOut.IsDust(::minRelayTxFee)) {
+ nFeeRet += nChange;
+ nChange = 0;
+ reservekey.ReturnKey();
+ } else {
+ // Insert change txn at random position:
+ vector<CTxOut>::iterator position = txNew.vout.begin() + GetRandInt(txNew.vout.size() + 1);
+ txNew.vout.insert(position, newTxOut);
+ }
  }
  } else
  reservekey.ReturnKey();
@@ -4036,6 +4052,14 @@ void CWallet::AutoCombineDust()
  CScript scriptPubKey = GetScriptForDestination(it->first.Get());
  vecSend.push_back(make_pair(scriptPubKey, nTotalRewardsValue));
 
+ //Send change to same address
+ CTxDestination destMyAddress;
+ if (!ExtractDestination(scriptPubKey, destMyAddress)) {
+ LogPrintf("AutoCombineDust: failed to extract destination\n");
+ continue;
+ }
+ coinControl->destChange = destMyAddress;
+
  // Create the transaction and commit it to the network
  CWalletTx wtx;
  CReserveKey keyChange(this); // this change address does not end up being used, because change is returned with coin control switch