rpc: Add "getburnreport" RPC function

src/rpc/blockchain.cpp

@@ -2108,3 +2108,66 @@ UniValue rpc_reorganize(const UniValue& params, bool fHelp)
     results.pushKV("RollbackChain",fResult);
     return results;
 }
+
+UniValue getburnreport(const UniValue& params, bool fHelp)
+{
+    if (fHelp || params.size() != 0)
+        throw runtime_error(
+                "getburnreport\n"
+                "Scan for and aggregate network-wide amounts for provably-destroyed outputs.\n");
+
+    CBlock block;
+    CAmount total_amount = 0;
+    CAmount voluntary_amount = 0;
+    std::map<GRC::ContractType, CAmount> contract_amounts;
+
+    LOCK(cs_main);
+
+    // For now, we only consider transaction outputs with scripts that a node
+    // will immediately refuse to evaluate:
+    //
+    //  - The script begins with the OP_RETURN op code
+    //  - The script exceeds the maximum size
+    //
+    // We can try additional heuristics in the future, but many of these will
+    // be very difficult or expensive to recognize.
+    //
+    for (const CBlockIndex* pindex = pindexGenesisBlock; pindex; pindex = pindex->pnext) {
+        if (!block.ReadFromDisk(pindex)) {
+            continue;
+        }
+
+        for (size_t i = pindex->IsProofOfStake() ? 2 : 1; i < block.vtx.size(); ++i) {
+            const CTransaction& tx = block.vtx[i];
+
+            for (const auto& output : tx.vout) {
+                if (output.scriptPubKey.IsUnspendable()) {
+                    total_amount += output.nValue;
+
+                    if (!tx.GetContracts().empty()) {
+                        contract_amounts[tx.vContracts[0].m_type.Value()] += output.nValue;
+                    } else {
+                        voluntary_amount += output.nValue;
+                    }
+                }
+            }
+        }
+    }
+
+    UniValue json(UniValue::VOBJ);
+
+    json.pushKV("total", ValueFromAmount(total_amount));
+    json.pushKV("voluntary", ValueFromAmount(voluntary_amount));
+
+    UniValue contracts(UniValue::VOBJ);
+
+    for (const auto& amount_pair : contract_amounts) {
+        contracts.pushKV(
+            GRC::Contract::Type(amount_pair.first).ToString(),
+            ValueFromAmount(amount_pair.second));
+    }
+
+    json.pushKV("contracts", contracts);
+
+    return json;
+}

src/rpc/server.cpp

@@ -417,6 +417,7 @@ static const CRPCCommand vRPCCommands[] =
     { "getblockbynumber",        &getblockbynumber,        cat_network       },
     { "getblockcount",           &getblockcount,           cat_network       },
     { "getblockhash",            &getblockhash,            cat_network       },
+    { "getburnreport",           &getburnreport,           cat_network       },
     { "getcheckpoint",           &getcheckpoint,           cat_network       },
     { "getconnectioncount",      &getconnectioncount,      cat_network       },
     { "getdifficulty",           &getdifficulty,           cat_network       },

src/rpc/server.h

@@ -236,6 +236,7 @@ extern UniValue getblockbynumber(const UniValue& params, bool fHelp);
 extern UniValue getblockchaininfo(const UniValue& params, bool fHelp);
 extern UniValue getblockcount(const UniValue& params, bool fHelp);
 extern UniValue getblockhash(const UniValue& params, bool fHelp);
+extern UniValue getburnreport(const UniValue& params, bool fHelp);
 extern UniValue getcheckpoint(const UniValue& params, bool fHelp);
 extern UniValue getconnectioncount(const UniValue& params, bool fHelp);
 extern UniValue getdifficulty(const UniValue& params, bool fHelp);

src/script.cpp

@@ -332,7 +332,7 @@ bool EvalScript(vector<vector<unsigned char> >& stack, const CScript& script, co
     valtype vchPushValue;
     vector<bool> vfExec;
     vector<valtype> altstack;
-    if (script.size() > 10000)
+    if (script.size() > MAX_SCRIPT_SIZE)
         return false;
     int nOpCount = 0;
 

src/script.h

@@ -25,6 +25,9 @@ class CTransaction;
 static const unsigned int MAX_SCRIPT_ELEMENT_SIZE = 520; // bytes
 static const unsigned int MAX_OP_RETURN_RELAY = 80;      // bytes
 
+// Maximum script length in bytes
+static const int MAX_SCRIPT_SIZE = 10000;
+
 /** Signature hash types/flags */
 enum
 {
@@ -581,6 +584,16 @@ class CScript : public CScriptBase
     {
         return CScriptID(Hash160(*this));
     }
+
+    /**
+     * Returns whether the script is guaranteed to fail at execution,
+     * regardless of the initial stack. This allows outputs to be pruned
+     * instantly when entering the UTXO set.
+     */
+    bool IsUnspendable() const
+    {
+        return (size() > 0 && *begin() == OP_RETURN) || (size() > MAX_SCRIPT_SIZE);
+    }
 };
 
 /**

src/wallet/wallet.cpp

@@ -847,7 +847,7 @@ void CWalletTx::GetAmounts(list<COutputEntry>& listReceived, list<COutputEntry>&
         {
             if (!ExtractDestination(txout.scriptPubKey, address))
             {
-                if (txout.scriptPubKey[0] != OP_RETURN)
+                if (!txout.scriptPubKey.IsUnspendable())
                 {
                     LogPrintf("CWalletTx::GetAmounts: Unknown transaction type found, txid %s",
                               this->GetHash().ToString().c_str());
@@ -891,7 +891,7 @@ void CWalletTx::GetAmounts(list<COutputEntry>& listReceived, list<COutputEntry>&
         // If this is my output AND the transaction is not from me, then record the output as received.
         if (fIsMine != ISMINE_NO && !fIsFromMe)
         {
-            if (!ExtractDestination(txout.scriptPubKey, address) && txout.scriptPubKey[0] != OP_RETURN)
+            if (!ExtractDestination(txout.scriptPubKey, address) && !txout.scriptPubKey.IsUnspendable())
             {
                 LogPrintf("CWalletTx::GetAmounts: Unknown transaction type found, txid %s",
                           this->GetHash().ToString().c_str());
@@ -908,7 +908,7 @@ void CWalletTx::GetAmounts(list<COutputEntry>& listReceived, list<COutputEntry>&
         {
             if (!ExtractDestination(txout.scriptPubKey, address))
             {
-                if (txout.scriptPubKey[0] != OP_RETURN)
+                if (!txout.scriptPubKey.IsUnspendable())
                 {
                     LogPrintf("CWalletTx::GetAmounts: Unknown transaction type found, txid %s",
                               this->GetHash().ToString().c_str());