Merge bitcoin/bitcoin#23155: rpc: various fixups for dumptxoutset

ffd09281fe26446fcefa0627c220a52706e35227 rpc: various fixups for dumptxoutset (James O'Beirne)

Pull request description:

  This is part of the [assumeutxo project](https://github.com/bitcoin/bitcoin/projects/11) (parent PR: #15606)

  ---

  A few fixes to make this RPC actually useful when generating snapshots.

  - Generate an assumeutxo hash and display it (sort of a bugfix)
  - Add nchaintx to output (necessary for use in chainparams entry)
  - Add path of serialized UTXO file to output

ACKs for top commit:
  laanwj:
    Code review ACK ffd09281fe26446fcefa0627c220a52706e35227

Tree-SHA512: b0b5fd5138dea0e21258b1b18ab75bf3fd1628522cc1dbafa81af9cb9fa96562a1c39124fdb31057f256bfc560f462f907e9fe5e209b577b3f57afae2b7be826

2 files changed, 29 insertions, 5 deletions

diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 55048f6811..bd11d76866 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -15,10 +15,12 @@
 #include <core_io.h>
 #include <deploymentinfo.h>
 #include <deploymentstatus.h>
+#include <fs.h>
 #include <hash.h>
 #include <index/blockfilterindex.h>
 #include <index/coinstatsindex.h>
 #include <node/blockstorage.h>
+#include <logging/timer.h>
 #include <node/coinstats.h>
 #include <node/context.h>
 #include <node/utxo_snapshot.h>
@@ -2556,6 +2558,8 @@ static RPCHelpMan dumptxoutset()
                     {RPCResult::Type::STR_HEX, "base_hash", "the hash of the base of the snapshot"},
                     {RPCResult::Type::NUM, "base_height", "the height of the base of the snapshot"},
                     {RPCResult::Type::STR, "path", "the absolute path that the snapshot was written to"},
+                    {RPCResult::Type::STR_HEX, "txoutset_hash", "the hash of the UTXO set contents"},
+                    {RPCResult::Type::NUM, "nchaintx", "the number of transactions in the chain up to and including the base block"},
                 }
         },
         RPCExamples{
@@ -2578,7 +2582,8 @@ static RPCHelpMan dumptxoutset()
     FILE* file{fsbridge::fopen(temppath, "wb")};
     CAutoFile afile{file, SER_DISK, CLIENT_VERSION};
     NodeContext& node = EnsureAnyNodeContext(request.context);
-    UniValue result = CreateUTXOSnapshot(node, node.chainman->ActiveChainstate(), afile);
+    UniValue result = CreateUTXOSnapshot(
+        node, node.chainman->ActiveChainstate(), afile, path, temppath);
     fs::rename(temppath, path);
 
     result.pushKV("path", path.u8string());
@@ -2587,10 +2592,15 @@ static RPCHelpMan dumptxoutset()
     };
 }
 
-UniValue CreateUTXOSnapshot(NodeContext& node, CChainState& chainstate, CAutoFile& afile)
+UniValue CreateUTXOSnapshot(
+    NodeContext& node,
+    CChainState& chainstate,
+    CAutoFile& afile,
+    const fs::path& path,
+    const fs::path& temppath)
 {
     std::unique_ptr<CCoinsViewCursor> pcursor;
-    CCoinsStats stats{CoinStatsHashType::NONE};
+    CCoinsStats stats{CoinStatsHashType::HASH_SERIALIZED};
     CBlockIndex* tip;
 
     {
@@ -2619,6 +2629,10 @@ UniValue CreateUTXOSnapshot(NodeContext& node, CChainState& chainstate, CAutoFil
         CHECK_NONFATAL(tip);
     }
 
+    LOG_TIME_SECONDS(strprintf("writing UTXO snapshot at height %s (%s) to file %s (via %s)",
+        tip->nHeight, tip->GetBlockHash().ToString(),
+        fs::PathToString(path), fs::PathToString(temppath)));
+
     SnapshotMetadata metadata{tip->GetBlockHash(), stats.coins_count, tip->nChainTx};
 
     afile << metadata;
@@ -2644,7 +2658,11 @@ UniValue CreateUTXOSnapshot(NodeContext& node, CChainState& chainstate, CAutoFil
     result.pushKV("coins_written", stats.coins_count);
     result.pushKV("base_hash", tip->GetBlockHash().ToString());
     result.pushKV("base_height", tip->nHeight);
-
+    result.pushKV("path", path.u8string());
+    result.pushKV("txoutset_hash", stats.hashSerialized.ToString());
+    // Cast required because univalue doesn't have serialization specified for
+    // `unsigned int`, nChainTx's type.
+    result.pushKV("nchaintx", uint64_t{tip->nChainTx});
     return result;
 }
 
diff --git a/src/rpc/blockchain.h b/src/rpc/blockchain.h
index 65f6b1429e..0ad68a7fd6 100644
--- a/src/rpc/blockchain.h
+++ b/src/rpc/blockchain.h
@@ -7,6 +7,7 @@
 
 #include <consensus/amount.h>
 #include <core_io.h>
+#include <fs.h>
 #include <streams.h>
 #include <sync.h>
 
@@ -65,6 +66,11 @@ CBlockPolicyEstimator& EnsureAnyFeeEstimator(const std::any& 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);
+UniValue CreateUTXOSnapshot(
+    NodeContext& node,
+    CChainState& chainstate,
+    CAutoFile& afile,
+    const fs::path& path,
+    const fs::path& tmppath);
 
 #endif // BITCOIN_RPC_BLOCKCHAIN_H