CTxOut: add IsConfidential method

Author: delta1

src/policy/discount.h

@@ -24,8 +24,9 @@ static inline int64_t GetDiscountVirtualTransactionSize(const CTransaction& tx,
     // for each confidential output
     for (size_t i = 0; i < tx.vout.size(); ++i) {
         const CTxOut& output = tx.vout[i];
-        if (output.IsFee()) continue;
-        if (output.nAsset.IsCommitment() && output.nValue.IsCommitment()) {
+        if (output.IsFee()) {
+            continue;
+        } else if (output.IsConfidential()) {
             // subtract the weight of the output witness
             weight -= ::GetSerializeSize(tx.witness.vtxoutwit[i], PROTOCOL_VERSION);
             // subtract the weight difference of amount commitment (33) vs explicit amount (9)

src/primitives/transaction.h

@@ -345,6 +345,12 @@ class CTxOut
     {
         return a.scriptPubKey < b.scriptPubKey;
     }
+
+    // ELEMENTS: a "confidential" output has commitments instead of explicit values
+    bool IsConfidential() const
+    {
+        return nValue.IsCommitment() && nAsset.IsCommitment() && nNonce.IsCommitment();
+    }
 };
 
 struct CMutableTransaction;