Have createNewBlock return BlockTemplate interface

An external program that uses the Mining interface may need quick access to some information in the block template, while it can wait a bit longer for the full raw transaction data.

This would be the case for a Stratum v2 Template Provider which needs to send a NewTemplate message (which doesn't include transactions) as quickly as possible.

src/interfaces/mining.h

@@ -5,26 +5,45 @@
 #ifndef BITCOIN_INTERFACES_MINING_H
 #define BITCOIN_INTERFACES_MINING_H
 
-#include <node/types.h>
+#include <consensus/amount.h>       // for CAmount
-#include <uint256.h>
+#include <node/types.h>             // for BlockCreateOptions
+#include <primitives/block.h>       // for CBlock, CBlockHeader
+#include <primitives/transaction.h> // for CTransactionRef
+#include <stdint.h>                 // for int64_t
+#include <uint256.h>                // for uint256
 
-#include <memory>
+#include <memory>   // for unique_ptr, shared_ptr
-#include <optional>
+#include <optional> // for optional
+#include <vector>   // for vector
 
 namespace node {
-struct CBlockTemplate;
 struct NodeContext;
 } // namespace node
 
 class BlockValidationState;
-class CBlock;
 class CScript;
 
 namespace interfaces {
 
+//! Block template interface
+class BlockTemplate
+{
+public:
+    virtual ~BlockTemplate() = default;
+
+    virtual CBlockHeader getBlockHeader() = 0;
+    virtual CBlock getBlock() = 0;
+
+    virtual std::vector<CAmount> getTxFees() = 0;
+    virtual std::vector<int64_t> getTxSigops() = 0;
+
+    virtual CTransactionRef getCoinbaseTx() = 0;
+    virtual std::vector<unsigned char> getCoinbaseCommitment() = 0;
+    virtual int getWitnessCommitmentIndex() = 0;
+};
+
 //! Interface giving clients (RPC, Stratum v2 Template Provider in the future)
 //! ability to create block templates.
-
 class Mining
 {
 public:
@@ -39,14 +58,14 @@ public:
     //! Returns the hash for the tip of this chain
     virtual std::optional<uint256> getTipHash() = 0;
 
-   /**
+    /**
      * Construct a new block template
      *
      * @param[in] script_pub_key the coinbase output
      * @param[in] options options for creating the block
      * @returns a block template
      */
-    virtual std::unique_ptr<node::CBlockTemplate> createNewBlock(const CScript& script_pub_key, const node::BlockCreateOptions& options={}) = 0;
+    virtual std::unique_ptr<BlockTemplate> createNewBlock(const CScript& script_pub_key, const node::BlockCreateOptions& options = {}) = 0;
 
     /**
      * Processes new block. A valid new block is automatically relayed to peers.

src/node/interfaces.cpp

@@ -67,6 +67,7 @@
 
 #include <boost/signals2/signal.hpp>
 
+using interfaces::BlockTemplate;
 using interfaces::BlockTip;
 using interfaces::Chain;
 using interfaces::FoundBlock;
@@ -863,6 +864,52 @@ public:
     NodeContext& m_node;
 };
 
+class BlockTemplateImpl : public BlockTemplate
+{
+public:
+    explicit BlockTemplateImpl(std::unique_ptr<CBlockTemplate> block_template) : m_block_template(std::move(block_template))
+    {
+        assert(m_block_template);
+    }
+
+    CBlockHeader getBlockHeader() override
+    {
+        return m_block_template->block;
+    }
+
+    CBlock getBlock() override
+    {
+        return m_block_template->block;
+    }
+
+    std::vector<CAmount> getTxFees() override
+    {
+        return m_block_template->vTxFees;
+    }
+
+    std::vector<int64_t> getTxSigops() override
+    {
+        return m_block_template->vTxSigOpsCost;
+    }
+
+    CTransactionRef getCoinbaseTx() override
+    {
+        return m_block_template->block.vtx[0];
+    }
+
+    std::vector<unsigned char> getCoinbaseCommitment() override
+    {
+        return m_block_template->vchCoinbaseCommitment;
+    }
+
+    int getWitnessCommitmentIndex() override
+    {
+        return GetWitnessCommitmentIndex(m_block_template->block);
+    }
+
+    const std::unique_ptr<CBlockTemplate> m_block_template;
+};
+
 class MinerImpl : public Mining
 {
 public:
@@ -909,11 +956,11 @@ public:
         return TestBlockValidity(state, chainman().GetParams(), chainman().ActiveChainstate(), block, tip, /*fCheckPOW=*/false, check_merkle_root);
     }
 
-    std::unique_ptr<CBlockTemplate> createNewBlock(const CScript& script_pub_key, const BlockCreateOptions& options) override
+    std::unique_ptr<BlockTemplate> createNewBlock(const CScript& script_pub_key, const BlockCreateOptions& options) override
     {
         BlockAssembler::Options assemble_options{options};
         ApplyArgsManOptions(*Assert(m_node.args), assemble_options);
-        return BlockAssembler{chainman().ActiveChainstate(), context()->mempool.get(), assemble_options}.CreateNewBlock(script_pub_key);
+        return std::make_unique<BlockTemplateImpl>(BlockAssembler{chainman().ActiveChainstate(), context()->mempool.get(), assemble_options}.CreateNewBlock(script_pub_key));
     }
 
     NodeContext* context() override { return &m_node; }

src/rpc/mining.cpp

@@ -45,9 +45,9 @@
 #include <memory>
 #include <stdint.h>
 
-using node::BlockAssembler;
+using interfaces::BlockTemplate;
-using node::CBlockTemplate;
 using interfaces::Mining;
+using node::BlockAssembler;
 using node::NodeContext;
 using node::RegenerateCommitments;
 using node::UpdateTime;
@@ -130,7 +130,7 @@ static RPCHelpMan getnetworkhashps()
     };
 }
 
-static bool GenerateBlock(ChainstateManager& chainman, Mining& miner, CBlock& block, uint64_t& max_tries, std::shared_ptr<const CBlock>& block_out, bool process_new_block)
+static bool GenerateBlock(ChainstateManager& chainman, Mining& miner, CBlock&& block, uint64_t& max_tries, std::shared_ptr<const CBlock>& block_out, bool process_new_block)
 {
     block_out.reset();
     block.hashMerkleRoot = BlockMerkleRoot(block);
@@ -146,7 +146,7 @@ static bool GenerateBlock(ChainstateManager& chainman, Mining& miner, CBlock& bl
         return true;
     }
 
-    block_out = std::make_shared<const CBlock>(block);
+    block_out = std::make_shared<const CBlock>(std::move(block));
 
     if (!process_new_block) return true;
 
@@ -161,12 +161,11 @@ static UniValue generateBlocks(ChainstateManager& chainman, Mining& miner, const
 {
     UniValue blockHashes(UniValue::VARR);
     while (nGenerate > 0 && !chainman.m_interrupt) {
-        std::unique_ptr<CBlockTemplate> pblocktemplate(miner.createNewBlock(coinbase_script));
+        std::unique_ptr<BlockTemplate> block_template(miner.createNewBlock(coinbase_script));
-        if (!pblocktemplate.get())
+        CHECK_NONFATAL(block_template);
-            throw JSONRPCError(RPC_INTERNAL_ERROR, "Couldn't create new block");
 
         std::shared_ptr<const CBlock> block_out;
-        if (!GenerateBlock(chainman, miner, pblocktemplate->block, nMaxTries, block_out, /*process_new_block=*/true)) {
+        if (!GenerateBlock(chainman, miner, block_template->getBlock(), nMaxTries, block_out, /*process_new_block=*/true)) {
             break;
         }
 
@@ -371,11 +370,10 @@ static RPCHelpMan generateblock()
 
     ChainstateManager& chainman = EnsureChainman(node);
     {
-        std::unique_ptr<CBlockTemplate> blocktemplate{miner.createNewBlock(coinbase_script, {.use_mempool = false})};
+        std::unique_ptr<BlockTemplate> block_template{miner.createNewBlock(coinbase_script, {.use_mempool = false})};
-        if (!blocktemplate) {
+        CHECK_NONFATAL(block_template);
-            throw JSONRPCError(RPC_INTERNAL_ERROR, "Couldn't create new block");
+
-        }
+        block = block_template->getBlock();
-        block = blocktemplate->block;
     }
 
     CHECK_NONFATAL(block.vtx.size() == 1);
@@ -394,7 +392,7 @@ static RPCHelpMan generateblock()
     std::shared_ptr<const CBlock> block_out;
     uint64_t max_tries{DEFAULT_MAX_TRIES};
 
-    if (!GenerateBlock(chainman, miner, block, max_tries, block_out, process_new_block) || !block_out) {
+    if (!GenerateBlock(chainman, miner, std::move(block), max_tries, block_out, process_new_block) || !block_out) {
         throw JSONRPCError(RPC_MISC_ERROR, "Failed to make block.");
     }
 
@@ -800,7 +798,7 @@ static RPCHelpMan getblocktemplate()
     // Update block
     static CBlockIndex* pindexPrev;
     static int64_t time_start;
-    static std::unique_ptr<CBlockTemplate> pblocktemplate;
+    static std::unique_ptr<BlockTemplate> block_template;
     if (!pindexPrev || pindexPrev->GetBlockHash() != tip ||
         (miner.getTransactionsUpdated() != nTransactionsUpdatedLast && GetTime() - time_start > 5))
     {
@@ -814,20 +812,19 @@ static RPCHelpMan getblocktemplate()
 
         // Create new block
         CScript scriptDummy = CScript() << OP_TRUE;
-        pblocktemplate = miner.createNewBlock(scriptDummy);
+        block_template = miner.createNewBlock(scriptDummy);
-        if (!pblocktemplate) {
+        CHECK_NONFATAL(block_template);
-            throw JSONRPCError(RPC_OUT_OF_MEMORY, "Out of memory");
+
-        }
 
         // Need to update only after we know createNewBlock succeeded
         pindexPrev = pindexPrevNew;
     }
     CHECK_NONFATAL(pindexPrev);
-    CBlock* pblock = &pblocktemplate->block; // pointer for convenience
+    CBlock block{block_template->getBlock()};
 
     // Update nTime
-    UpdateTime(pblock, consensusParams, pindexPrev);
+    UpdateTime(&block, consensusParams, pindexPrev);
-    pblock->nNonce = 0;
+    block.nNonce = 0;
 
     // NOTE: If at some point we support pre-segwit miners post-segwit-activation, this needs to take segwit support into consideration
     const bool fPreSegWit = !DeploymentActiveAfter(pindexPrev, chainman, Consensus::DEPLOYMENT_SEGWIT);
@@ -836,8 +833,11 @@ static RPCHelpMan getblocktemplate()
 
     UniValue transactions(UniValue::VARR);
     std::map<uint256, int64_t> setTxIndex;
+    std::vector<CAmount> tx_fees{block_template->getTxFees()};
+    std::vector<CAmount> tx_sigops{block_template->getTxSigops()};
+
     int i = 0;
-    for (const auto& it : pblock->vtx) {
+    for (const auto& it : block.vtx) {
         const CTransaction& tx = *it;
         uint256 txHash = tx.GetHash();
         setTxIndex[txHash] = i++;
@@ -860,8 +860,8 @@ static RPCHelpMan getblocktemplate()
         entry.pushKV("depends", std::move(deps));
 
         int index_in_template = i - 1;
-        entry.pushKV("fee", pblocktemplate->vTxFees[index_in_template]);
+        entry.pushKV("fee", tx_fees.at(index_in_template));
-        int64_t nTxSigOps = pblocktemplate->vTxSigOpsCost[index_in_template];
+        int64_t nTxSigOps{tx_sigops.at(index_in_template)};
         if (fPreSegWit) {
             CHECK_NONFATAL(nTxSigOps % WITNESS_SCALE_FACTOR == 0);
             nTxSigOps /= WITNESS_SCALE_FACTOR;
@@ -874,7 +874,7 @@ static RPCHelpMan getblocktemplate()
 
     UniValue aux(UniValue::VOBJ);
 
-    arith_uint256 hashTarget = arith_uint256().SetCompact(pblock->nBits);
+    arith_uint256 hashTarget = arith_uint256().SetCompact(block.nBits);
 
     UniValue aMutable(UniValue::VARR);
     aMutable.push_back("time");
@@ -904,7 +904,7 @@ static RPCHelpMan getblocktemplate()
                 break;
             case ThresholdState::LOCKED_IN:
                 // Ensure bit is set in block version
-                pblock->nVersion |= chainman.m_versionbitscache.Mask(consensusParams, pos);
+                block.nVersion |= chainman.m_versionbitscache.Mask(consensusParams, pos);
                 [[fallthrough]];
             case ThresholdState::STARTED:
             {
@@ -913,7 +913,7 @@ static RPCHelpMan getblocktemplate()
                 if (setClientRules.find(vbinfo.name) == setClientRules.end()) {
                     if (!vbinfo.gbt_force) {
                         // If the client doesn't support this, don't indicate it in the [default] version
-                        pblock->nVersion &= ~chainman.m_versionbitscache.Mask(consensusParams, pos);
+                        block.nVersion &= ~chainman.m_versionbitscache.Mask(consensusParams, pos);
                     }
                 }
                 break;
@@ -933,15 +933,15 @@ static RPCHelpMan getblocktemplate()
             }
         }
     }
-    result.pushKV("version", pblock->nVersion);
+    result.pushKV("version", block.nVersion);
     result.pushKV("rules", std::move(aRules));
     result.pushKV("vbavailable", std::move(vbavailable));
     result.pushKV("vbrequired", int(0));
 
-    result.pushKV("previousblockhash", pblock->hashPrevBlock.GetHex());
+    result.pushKV("previousblockhash", block.hashPrevBlock.GetHex());
     result.pushKV("transactions", std::move(transactions));
     result.pushKV("coinbaseaux", std::move(aux));
-    result.pushKV("coinbasevalue", (int64_t)pblock->vtx[0]->vout[0].nValue);
+    result.pushKV("coinbasevalue", (int64_t)block.vtx[0]->vout[0].nValue);
     result.pushKV("longpollid", tip.GetHex() + ToString(nTransactionsUpdatedLast));
     result.pushKV("target", hashTarget.GetHex());
     result.pushKV("mintime", (int64_t)pindexPrev->GetMedianTimePast()+1);
@@ -960,16 +960,16 @@ static RPCHelpMan getblocktemplate()
     if (!fPreSegWit) {
         result.pushKV("weightlimit", (int64_t)MAX_BLOCK_WEIGHT);
     }
-    result.pushKV("curtime", pblock->GetBlockTime());
+    result.pushKV("curtime", block.GetBlockTime());
-    result.pushKV("bits", strprintf("%08x", pblock->nBits));
+    result.pushKV("bits", strprintf("%08x", block.nBits));
     result.pushKV("height", (int64_t)(pindexPrev->nHeight+1));
 
     if (consensusParams.signet_blocks) {
         result.pushKV("signet_challenge", HexStr(consensusParams.signet_challenge));
     }
 
-    if (!pblocktemplate->vchCoinbaseCommitment.empty()) {
+    if (!block_template->getCoinbaseCommitment().empty()) {
-        result.pushKV("default_witness_commitment", HexStr(pblocktemplate->vchCoinbaseCommitment));
+        result.pushKV("default_witness_commitment", HexStr(block_template->getCoinbaseCommitment()));
     }
 
     return result;