policy: Add CalculateExtraTxWeight to increase weight for datacarrier bytes

Author: luke-jr

src/policy/policy.cpp

@@ -435,3 +435,26 @@ size_t DatacarrierBytes(const CTransaction& tx, const CCoinsViewCache& view)
 
     return ret;
 }
+
+int32_t CalculateExtraTxWeight(const CTransaction& tx, const CCoinsViewCache& view, const unsigned int weight_per_data_byte)
+{
+    int32_t mod_weight{0};
+
+    // Add in any extra weight for data bytes
+    if (weight_per_data_byte > 1) {
+        for (const CTxIn& txin : tx.vin) {
+            const CTxOut &utxo = view.AccessCoin(txin.prevout).out;
+            auto[script, consensus_weight_per_byte] = GetScriptForTransactionInput(utxo.scriptPubKey, txin);
+            if (weight_per_data_byte > consensus_weight_per_byte) {
+                mod_weight += script.DatacarrierBytes() * (weight_per_data_byte - consensus_weight_per_byte);
+            }
+        }
+        if (weight_per_data_byte > WITNESS_SCALE_FACTOR) {
+            for (const CTxOut& txout : tx.vout) {
+                mod_weight += txout.scriptPubKey.DatacarrierBytes() * (weight_per_data_byte - WITNESS_SCALE_FACTOR);
+            }
+        }
+    }
+
+    return mod_weight;
+}

src/policy/policy.h

@@ -198,4 +198,6 @@ std::pair<CScript, unsigned int> GetScriptForTransactionInput(CScript prevScript
 
 size_t DatacarrierBytes(const CTransaction& tx, const CCoinsViewCache& view);
 
+int32_t CalculateExtraTxWeight(const CTransaction& tx, const CCoinsViewCache& view, const unsigned int weight_per_data_byte);
+
 #endif // BITCOIN_POLICY_POLICY_H