segwit: fix gui wallet send transaction size calculation assertion fa…

…iled
bitcoin · May 30, 2016 · c1c38a2 · c1c38a2
1 parent 059d4d1
commit c1c38a2
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Showing 2 changed files with 19 additions and 2 deletions.
diff --git a/src/qt/coincontroldialog.cpp b/src/qt/coincontroldialog.cpp
@@ -485,6 +485,7 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
     unsigned int nQuantity      = 0;
     int nQuantityUncompressed   = 0;
     bool fAllowFree             = false;
+    bool fWitness               = false;
 
     std::vector<COutPoint> vCoinControl;
     std::vector<COutput>   vOutputs;
@@ -513,7 +514,14 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
 
         // Bytes
         CTxDestination address;
-        if(ExtractDestination(out.tx->vout[out.i].scriptPubKey, address))
+        int witnessversion = 0;
+        std::vector<unsigned char> witnessprogram;
+        if (out.tx->vout[out.i].scriptPubKey.IsWitnessProgram(witnessversion, witnessprogram))
+        {
+            nBytesInputs += (32 + 4 + 1 + (107 / WITNESS_SCALE_FACTOR) + 4);
+            fWitness = true;
+        }
+        else if(ExtractDestination(out.tx->vout[out.i].scriptPubKey, address))
         {
             CPubKey pubkey;
             CKeyID *keyid = boost::get<CKeyID>(&address);
@@ -534,6 +542,14 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
     {
         // Bytes
         nBytes = nBytesInputs + ((CoinControlDialog::payAmounts.size() > 0 ? CoinControlDialog::payAmounts.size() + 1 : 2) * 34) + 10; // always assume +1 output for change here
+        if (fWitness)
+        {
+            // there is some fudging in these numbers related to the actual virtual transaction size calculation that will keep this estimate from being exact.
+            // usually, the result will be an overestimate within a couple of satoshis so that the confirmation dialog ends up displaying a slightly smaller fee.
+            // also, the witness stack size value value is a variable sized integer. usually, the number of stack items will be well under the single byte var int limit.
+            nBytes += 2; // account for the serialized marker and flag bytes
+            nBytes += nQuantity; // account for the witness byte that holds the number of stack items for each input.
+        }
 
         // Priority
         double mempoolEstimatePriority = mempool.estimateSmartPriority(nTxConfirmTarget);

diff --git a/src/qt/walletmodeltransaction.cpp b/src/qt/walletmodeltransaction.cpp
@@ -4,6 +4,7 @@
 
 #include "walletmodeltransaction.h"
 
+#include "policy/policy.h"
 #include "wallet/wallet.h"
 
 WalletModelTransaction::WalletModelTransaction(const QList<SendCoinsRecipient> &recipients) :
@@ -33,7 +34,7 @@ CWalletTx *WalletModelTransaction::getTransaction()
 
 unsigned int WalletModelTransaction::getTransactionSize()
 {
-    return (!walletTransaction ? 0 : (::GetSerializeSize(*(CTransaction*)walletTransaction, SER_NETWORK, PROTOCOL_VERSION)));
+    return (!walletTransaction ? 0 : ::GetVirtualTransactionSize(*walletTransaction));
 }
 
 CAmount WalletModelTransaction::getTransactionFee()