Add code to node/miner.cpp to get custom block

Co-authored-by: Pieter Wuille <bitcoin-dev@wuille.net>

src/node/miner.cpp

@@ -59,8 +59,10 @@ void RegenerateCommitments(CBlock& block, ChainstateManager& chainman)
 
 static BlockAssembler::Options ClampOptions(BlockAssembler::Options options)
 {
-    // Limit weight to between 4K and DEFAULT_BLOCK_MAX_WEIGHT for sanity:
-    options.nBlockMaxWeight = std::clamp<size_t>(options.nBlockMaxWeight, 4000, DEFAULT_BLOCK_MAX_WEIGHT);
+    if (options.sanity_check_block_weight) {
+        // Limit weight to between 4K and DEFAULT_BLOCK_MAX_WEIGHT for sanity:
+        options.nBlockMaxWeight = std::clamp<size_t>(options.nBlockMaxWeight, 4000, DEFAULT_BLOCK_MAX_WEIGHT);
+    }
     return options;
 }
 
@@ -423,9 +425,23 @@ void BlockAssembler::addPackageTxs(const CTxMemPool& mempool, int& nPackagesSele
         }
 
         ++nPackagesSelected;
+        size_per_feerate[CFeeRate{packageFees, packageSize}] += packageSize;
 
         // Update transactions that depend on each of these
         nDescendantsUpdated += UpdatePackagesForAdded(mempool, ancestors, mapModifiedTx);
     }
 }
+
+std::map<CFeeRate, uint64_t> BlockAssembler::GetFeeRateStats()
+{
+    return std::move(size_per_feerate);
+}
+
+std::map<CFeeRate, uint64_t> GetCustomBlockFeeRateHistogram(Chainstate& chainstate, const CTxMemPool* mempool, size_t block_weight)
+{
+    BlockAssembler::Options options = {.nBlockMaxWeight = block_weight, .sanity_check_block_weight = false};
+    BlockAssembler assembler(chainstate, mempool, options);
+    assembler.CreateNewBlock(CScript{});
+    return assembler.GetFeeRateStats();
+}
 } // namespace node

src/node/miner.h

@@ -143,6 +143,7 @@ class BlockAssembler
     uint64_t nBlockSigOpsCost;
     CAmount nFees;
     std::unordered_set<Txid, SaltedTxidHasher> inBlock;
+    std::map<CFeeRate, uint64_t> size_per_feerate;
 
     // Chain context for the block
     int nHeight;
@@ -159,6 +160,8 @@ class BlockAssembler
         CFeeRate blockMinFeeRate{DEFAULT_BLOCK_MIN_TX_FEE};
         // Whether to call TestBlockValidity() at the end of CreateNewBlock().
         bool test_block_validity{true};
+        // Whether we limit nBlockMaxWeight between 4k and DEFAULT_BLOCK_MAX_WEIGHT.
+        bool sanity_check_block_weight{true};
     };
 
     explicit BlockAssembler(Chainstate& chainstate, const CTxMemPool* mempool);
@@ -170,6 +173,10 @@ class BlockAssembler
     inline static std::optional<int64_t> m_last_block_num_txs{};
     inline static std::optional<int64_t> m_last_block_weight{};
 
+    /** Return a map from feerates to vbyte, indicating how many vbytes were
+     *  included in the block at which feerate. This can only be called once. */
+    std::map<CFeeRate, uint64_t> GetFeeRateStats();
+
 private:
     const Options m_options;
 
@@ -204,6 +211,9 @@ int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParam
 /** Update an old GenerateCoinbaseCommitment from CreateNewBlock after the block txs have changed */
 void RegenerateCommitments(CBlock& block, ChainstateManager& chainman);
 
+/** Get feerate statistics of a block weight from the mempool. */
+std::map<CFeeRate, uint64_t> GetCustomBlockFeeRateHistogram(Chainstate& chainstate, const CTxMemPool* mempool, size_t block_weight);
+
 /** Apply -blockmintxfee and -blockmaxweight options from ArgsManager to BlockAssembler options. */
 void ApplyArgsManOptions(const ArgsManager& gArgs, BlockAssembler::Options& options);
 } // namespace node