Add 'subtractFeeFromOutputs' option to 'fundrawtransaction'.

3 files changed, 40 insertions, 11 deletions

diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 5a4fcc743c..7d9d6ce489 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -2464,7 +2464,8 @@ UniValue fundrawtransaction(const JSONRPCRequest& request)
         throw runtime_error(
                             "fundrawtransaction \"hexstring\" ( options )\n"
                             "\nAdd inputs to a transaction until it has enough in value to meet its out value.\n"
-                            "This will not modify existing inputs, and will add one change output to the outputs.\n"
+                            "This will not modify existing inputs, and will add at most one change output to the outputs.\n"
+                            "No existing outputs will be modified unless \"subtractFeeFromOutputs\" is specified.\n"
                             "Note that inputs which were signed may need to be resigned after completion since in/outputs have been added.\n"
                             "The inputs added will not be signed, use signrawtransaction for that.\n"
                             "Note that all existing inputs must have their previous output transaction be in the wallet.\n"
@@ -2476,11 +2477,17 @@ UniValue fundrawtransaction(const JSONRPCRequest& request)
                             "1. \"hexstring\"           (string, required) The hex string of the raw transaction\n"
                             "2. options               (object, optional)\n"
                             "   {\n"
-                            "     \"changeAddress\"     (string, optional, default pool address) The bitcoin address to receive the change\n"
-                            "     \"changePosition\"    (numeric, optional, default random) The index of the change output\n"
-                            "     \"includeWatching\"   (boolean, optional, default false) Also select inputs which are watch only\n"
-                            "     \"lockUnspents\"      (boolean, optional, default false) Lock selected unspent outputs\n"
-                            "     \"feeRate\"           (numeric, optional, default not set: makes wallet determine the fee) Set a specific feerate (" + CURRENCY_UNIT + " per KB)\n"
+                            "     \"changeAddress\"          (string, optional, default pool address) The bitcoin address to receive the change\n"
+                            "     \"changePosition\"         (numeric, optional, default random) The index of the change output\n"
+                            "     \"includeWatching\"        (boolean, optional, default false) Also select inputs which are watch only\n"
+                            "     \"lockUnspents\"           (boolean, optional, default false) Lock selected unspent outputs\n"
+                            "     \"feeRate\"                (numeric, optional, default not set: makes wallet determine the fee) Set a specific feerate (" + CURRENCY_UNIT + " per KB)\n"
+                            "     \"subtractFeeFromOutputs\" (array, optional) A json array of integers.\n"
+                            "                              The fee will be equally deducted from the amount of each specified output.\n"
+                            "                              The outputs are specified by their zero-based index, before any change output is added.\n"
+                            "                              Those recipients will receive less bitcoins than you enter in their corresponding amount field.\n"
+                            "                              If no outputs are specified here, the sender pays the fee.\n"
+                            "                                  [vout_index,...]\n"
                             "   }\n"
                             "                         for backward compatibility: passing in a true instead of an object will result in {\"includeWatching\":true}\n"
                             "\nResult:\n"
@@ -2509,6 +2516,8 @@ UniValue fundrawtransaction(const JSONRPCRequest& request)
     bool lockUnspents = false;
     CFeeRate feeRate = CFeeRate(0);
     bool overrideEstimatedFeerate = false;
+    UniValue subtractFeeFromOutputs;
+    set<int> setSubtractFeeFromOutputs;
 
     if (request.params.size() > 1) {
       if (request.params[1].type() == UniValue::VBOOL) {
@@ -2527,6 +2536,7 @@ UniValue fundrawtransaction(const JSONRPCRequest& request)
                 {"includeWatching", UniValueType(UniValue::VBOOL)},
                 {"lockUnspents", UniValueType(UniValue::VBOOL)},
                 {"feeRate", UniValueType()}, // will be checked below
+                {"subtractFeeFromOutputs", UniValueType(UniValue::VARR)},
             },
             true, true);
 
@@ -2553,6 +2563,9 @@ UniValue fundrawtransaction(const JSONRPCRequest& request)
             feeRate = CFeeRate(AmountFromValue(options["feeRate"]));
             overrideEstimatedFeerate = true;
         }
+
+        if (options.exists("subtractFeeFromOutputs"))
+            subtractFeeFromOutputs = options["subtractFeeFromOutputs"].get_array();
       }
     }
 
@@ -2567,10 +2580,21 @@ UniValue fundrawtransaction(const JSONRPCRequest& request)
     if (changePosition != -1 && (changePosition < 0 || (unsigned int)changePosition > tx.vout.size()))
         throw JSONRPCError(RPC_INVALID_PARAMETER, "changePosition out of bounds");
 
+    for (unsigned int idx = 0; idx < subtractFeeFromOutputs.size(); idx++) {
+        int pos = subtractFeeFromOutputs[idx].get_int();
+        if (setSubtractFeeFromOutputs.count(pos))
+            throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Invalid parameter, duplicated position: %d", pos));
+        if (pos < 0)
+            throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Invalid parameter, negative position: %d", pos));
+        if (pos >= int(tx.vout.size()))
+            throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Invalid parameter, position too large: %d", pos));
+        setSubtractFeeFromOutputs.insert(pos);
+    }
+
     CAmount nFeeOut;
     string strFailReason;
 
-    if(!pwalletMain->FundTransaction(tx, nFeeOut, overrideEstimatedFeerate, feeRate, changePosition, strFailReason, includeWatching, lockUnspents, changeAddress))
+    if(!pwalletMain->FundTransaction(tx, nFeeOut, overrideEstimatedFeerate, feeRate, changePosition, strFailReason, includeWatching, lockUnspents, setSubtractFeeFromOutputs, changeAddress))
         throw JSONRPCError(RPC_INTERNAL_ERROR, strFailReason);
 
     UniValue result(UniValue::VOBJ);
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 6269b4521b..b243ee19bf 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -2181,14 +2181,15 @@ bool CWallet::SelectCoins(const vector<COutput>& vAvailableCoins, const CAmount&
     return res;
 }
 
-bool CWallet::FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, bool overrideEstimatedFeeRate, const CFeeRate& specificFeeRate, int& nChangePosInOut, std::string& strFailReason, bool includeWatching, bool lockUnspents, const CTxDestination& destChange)
+bool CWallet::FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, bool overrideEstimatedFeeRate, const CFeeRate& specificFeeRate, int& nChangePosInOut, std::string& strFailReason, bool includeWatching, bool lockUnspents, const std::set<int>& setSubtractFeeFromOutputs, const CTxDestination& destChange)
 {
     vector<CRecipient> vecSend;
 
     // Turn the txout set into a CRecipient vector
-    BOOST_FOREACH(const CTxOut& txOut, tx.vout)
+    for (size_t idx = 0; idx < tx.vout.size(); idx++)
     {
-        CRecipient recipient = {txOut.scriptPubKey, txOut.nValue, false};
+        const CTxOut& txOut = tx.vout[idx];
+        CRecipient recipient = {txOut.scriptPubKey, txOut.nValue, setSubtractFeeFromOutputs.count(idx) == 1};
         vecSend.push_back(recipient);
     }
 
@@ -2210,6 +2211,10 @@ bool CWallet::FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, bool ov
     if (nChangePosInOut != -1)
         tx.vout.insert(tx.vout.begin() + nChangePosInOut, wtx.tx->vout[nChangePosInOut]);
 
+    // Copy output sizes from new transaction; they may have had the fee subtracted from them
+    for (unsigned int idx = 0; idx < tx.vout.size(); idx++)
+        tx.vout[idx].nValue = wtx.tx->vout[idx].nValue;
+
     // Add new txins (keeping original txin scriptSig/order)
     BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
     {
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index f7103b6a80..3a809174f3 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -772,7 +772,7 @@ public:
      * Insert additional inputs into the transaction by
      * calling CreateTransaction();
      */
-    bool FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, bool overrideEstimatedFeeRate, const CFeeRate& specificFeeRate, int& nChangePosInOut, std::string& strFailReason, bool includeWatching, bool lockUnspents, const CTxDestination& destChange = CNoDestination());
+    bool FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, bool overrideEstimatedFeeRate, const CFeeRate& specificFeeRate, int& nChangePosInOut, std::string& strFailReason, bool includeWatching, bool lockUnspents, const std::set<int>& setSubtractFeeFromOutputs, const CTxDestination& destChange = CNoDestination());
 
     /**
      * Create a new transaction paying the recipients with a set of coins