move-onlyish: break out CreateUTXOSnapshot from dumptxoutset

This move/refactor is needed to set up a decent unittest for UTXO snapshot activation.

Author: jamesob

src/rpc/blockchain.cpp

@@ -2411,10 +2411,21 @@ static RPCHelpMan dumptxoutset()
 
     FILE* file{fsbridge::fopen(temppath, "wb")};
     CAutoFile afile{file, SER_DISK, CLIENT_VERSION};
+    NodeContext& node = EnsureNodeContext(request.context);
+    UniValue result = CreateUTXOSnapshot(node, node.chainman->ActiveChainstate(), afile);
+    fs::rename(temppath, path);
+
+    result.pushKV("path", path.string());
+    return result;
+},
+    };
+}
+
+UniValue CreateUTXOSnapshot(NodeContext& node, CChainState& chainstate, CAutoFile& afile)
+{
     std::unique_ptr<CCoinsViewCursor> pcursor;
     CCoinsStats stats;
     CBlockIndex* tip;
-    NodeContext& node = EnsureNodeContext(request.context);
 
     {
         // We need to lock cs_main to ensure that the coinsdb isn't written to
@@ -2431,13 +2442,13 @@ static RPCHelpMan dumptxoutset()
         //
         LOCK(::cs_main);
 
-        ::ChainstateActive().ForceFlushStateToDisk();
+        chainstate.ForceFlushStateToDisk();
 
-        if (!GetUTXOStats(&::ChainstateActive().CoinsDB(), stats, CoinStatsHashType::NONE, node.rpc_interruption_point)) {
+        if (!GetUTXOStats(&chainstate.CoinsDB(), stats, CoinStatsHashType::NONE, node.rpc_interruption_point)) {
             throw JSONRPCError(RPC_INTERNAL_ERROR, "Unable to read UTXO set");
         }
 
-        pcursor = std::unique_ptr<CCoinsViewCursor>(::ChainstateActive().CoinsDB().Cursor());
+        pcursor = std::unique_ptr<CCoinsViewCursor>(chainstate.CoinsDB().Cursor());
         tip = g_chainman.m_blockman.LookupBlockIndex(stats.hashBlock);
         CHECK_NONFATAL(tip);
     }
@@ -2462,16 +2473,13 @@ static RPCHelpMan dumptxoutset()
     }
 
     afile.fclose();
-    fs::rename(temppath, path);
 
     UniValue result(UniValue::VOBJ);
     result.pushKV("coins_written", stats.coins_count);
     result.pushKV("base_hash", tip->GetBlockHash().ToString());
     result.pushKV("base_height", tip->nHeight);
-    result.pushKV("path", path.string());
+
     return result;
-},
-    };
 }
 
 void RegisterBlockchainRPCCommands(CRPCTable &t)

src/rpc/blockchain.h

@@ -6,6 +6,7 @@
 #define BITCOIN_RPC_BLOCKCHAIN_H
 
 #include <amount.h>
+#include <streams.h>
 #include <sync.h>
 
 #include <stdint.h>
@@ -16,6 +17,7 @@ extern RecursiveMutex cs_main;
 class CBlock;
 class CBlockIndex;
 class CBlockPolicyEstimator;
+class CChainState;
 class CTxMemPool;
 class ChainstateManager;
 class UniValue;
@@ -57,4 +59,10 @@ CTxMemPool& EnsureMemPool(const util::Ref& context);
 ChainstateManager& EnsureChainman(const util::Ref& context);
 CBlockPolicyEstimator& EnsureFeeEstimator(const util::Ref& context);
 
+/**
+ * Helper to create UTXO snapshots given a chainstate and a file handle.
+ * @return a UniValue map containing metadata about the snapshot.
+ */
+UniValue CreateUTXOSnapshot(NodeContext& node, CChainState& chainstate, CAutoFile& afile);
+
 #endif