refactoring: FlushStateToDisk -> CChainState

Also renames global methods for clarity:

- ::FlushStateToDisk() -> CChainState::ForceFlushStateToDisk()
  - This performs an unconditional flush.

- ::PruneAndFlush() -> CChainState::PruneAndFlush()

4 files changed, 52 insertions, 35 deletions

diff --git a/src/init.cpp b/src/init.cpp
index 8095105cce..58cba5b665 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -259,7 +259,7 @@ void Shutdown(InitInterfaces& interfaces)
 
     // FlushStateToDisk generates a ChainStateFlushed callback, which we should avoid missing
     if (pcoinsTip != nullptr) {
-        FlushStateToDisk();
+        ::ChainstateActive().ForceFlushStateToDisk();
     }
 
     // After there are no more peers/RPC left to give us new data which may generate
@@ -275,7 +275,7 @@ void Shutdown(InitInterfaces& interfaces)
     {
         LOCK(cs_main);
         if (pcoinsTip != nullptr) {
-            FlushStateToDisk();
+            ::ChainstateActive().ForceFlushStateToDisk();
         }
         pcoinsTip.reset();
         pcoinscatcher.reset();
@@ -1692,7 +1692,7 @@ bool AppInitMain(InitInterfaces& interfaces)
         nLocalServices = ServiceFlags(nLocalServices & ~NODE_NETWORK);
         if (!fReindex) {
             uiInterface.InitMessage(_("Pruning blockstore..."));
-            PruneAndFlush();
+            ::ChainstateActive().PruneAndFlush();
         }
     }
 
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 3d0fa8eb2b..fef51bd709 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -1077,7 +1077,7 @@ static UniValue gettxoutsetinfo(const JSONRPCRequest& request)
     UniValue ret(UniValue::VOBJ);
 
     CCoinsStats stats;
-    FlushStateToDisk();
+    ::ChainstateActive().ForceFlushStateToDisk();
     if (GetUTXOStats(pcoinsdbview.get(), stats)) {
         ret.pushKV("height", (int64_t)stats.nHeight);
         ret.pushKV("bestblock", stats.hashBlock.GetHex());
@@ -2283,7 +2283,7 @@ UniValue scantxoutset(const JSONRPCRequest& request)
         std::unique_ptr<CCoinsViewCursor> pcursor;
         {
             LOCK(cs_main);
-            FlushStateToDisk();
+            ::ChainstateActive().ForceFlushStateToDisk();
             pcursor = std::unique_ptr<CCoinsViewCursor>(pcoinsdbview->Cursor());
             assert(pcursor);
         }
diff --git a/src/validation.cpp b/src/validation.cpp
index 279a7d0e09..6087260c6b 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -173,15 +173,7 @@ std::unique_ptr<CCoinsViewDB> pcoinsdbview;
 std::unique_ptr<CCoinsViewCache> pcoinsTip;
 std::unique_ptr<CBlockTreeDB> pblocktree;
 
-enum class FlushStateMode {
-    NONE,
-    IF_NEEDED,
-    PERIODIC,
-    ALWAYS
-};
-
 // See definition for documentation
-static bool FlushStateToDisk(const CChainParams& chainParams, CValidationState &state, FlushStateMode mode, int nManualPruneHeight=0);
 static void FindFilesToPruneManual(std::set<int>& setFilesToPrune, int nManualPruneHeight);
 static void FindFilesToPrune(std::set<int>& setFilesToPrune, uint64_t nPruneAfterHeight);
 bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks = nullptr);
@@ -854,7 +846,7 @@ static bool AcceptToMemoryPoolWithTime(const CChainParams& chainparams, CTxMemPo
     }
     // After we've (potentially) uncached entries, ensure our coins cache is still within its size limits
     CValidationState stateDummy;
-    FlushStateToDisk(chainparams, stateDummy, FlushStateMode::PERIODIC);
+    ::ChainstateActive().FlushStateToDisk(chainparams, stateDummy, FlushStateMode::PERIODIC);
     return res;
 }
 
@@ -1951,16 +1943,12 @@ bool CChainState::ConnectBlock(const CBlock& block, CValidationState& state, CBl
     return true;
 }
 
-/**
- * Update the on-disk chain state.
- * The caches and indexes are flushed depending on the mode we're called with
- * if they're too large, if it's been a while since the last write,
- * or always and in all cases if we're in prune mode and are deleting files.
- *
- * If FlushStateMode::NONE is used, then FlushStateToDisk(...) won't do anything
- * besides checking if we need to prune.
- */
-bool static FlushStateToDisk(const CChainParams& chainparams, CValidationState &state, FlushStateMode mode, int nManualPruneHeight) {
+bool CChainState::FlushStateToDisk(
+    const CChainParams& chainparams,
+    CValidationState &state,
+    FlushStateMode mode,
+    int nManualPruneHeight)
+{
     int64_t nMempoolUsage = mempool.DynamicMemoryUsage();
     LOCK(cs_main);
     static int64_t nLastWrite = 0;
@@ -2058,7 +2046,7 @@ bool static FlushStateToDisk(const CChainParams& chainparams, CValidationState &
     }
     if (full_flush_completed) {
         // Update best block in wallet (so we can detect restored wallets).
-        GetMainSignals().ChainStateFlushed(::ChainActive().GetLocator());
+        GetMainSignals().ChainStateFlushed(m_chain.GetLocator());
     }
     } catch (const std::runtime_error& e) {
         return AbortNode(state, std::string("System error while flushing: ") + e.what());
@@ -2066,19 +2054,20 @@ bool static FlushStateToDisk(const CChainParams& chainparams, CValidationState &
     return true;
 }
 
-void FlushStateToDisk() {
+void CChainState::ForceFlushStateToDisk() {
     CValidationState state;
     const CChainParams& chainparams = Params();
-    if (!FlushStateToDisk(chainparams, state, FlushStateMode::ALWAYS)) {
+    if (!this->FlushStateToDisk(chainparams, state, FlushStateMode::ALWAYS)) {
         LogPrintf("%s: failed to flush state (%s)\n", __func__, FormatStateMessage(state));
     }
 }
 
-void PruneAndFlush() {
+void CChainState::PruneAndFlush() {
     CValidationState state;
     fCheckForPruning = true;
     const CChainParams& chainparams = Params();
-    if (!FlushStateToDisk(chainparams, state, FlushStateMode::NONE)) {
+
+    if (!this->FlushStateToDisk(chainparams, state, FlushStateMode::NONE)) {
         LogPrintf("%s: failed to flush state (%s)\n", __func__, FormatStateMessage(state));
     }
 }
@@ -3587,7 +3576,8 @@ void PruneBlockFilesManual(int nManualPruneHeight)
 {
     CValidationState state;
     const CChainParams& chainparams = Params();
-    if (!FlushStateToDisk(chainparams, state, FlushStateMode::NONE, nManualPruneHeight)) {
+    if (!::ChainstateActive().FlushStateToDisk(
+            chainparams, state, FlushStateMode::NONE, nManualPruneHeight)) {
         LogPrintf("%s: failed to flush state (%s)\n", __func__, FormatStateMessage(state));
     }
 }
@@ -4183,7 +4173,7 @@ bool RewindBlockIndex(const CChainParams& params) {
         // and skip it here, we're about to -reindex-chainstate anyway, so
         // it'll get called a bunch real soon.
         CValidationState state;
-        if (!FlushStateToDisk(params, state, FlushStateMode::ALWAYS)) {
+        if (!::ChainstateActive().FlushStateToDisk(params, state, FlushStateMode::ALWAYS)) {
             LogPrintf("RewindBlockIndex: unable to flush state to disk (%s)\n", FormatStateMessage(state));
             return false;
         }
diff --git a/src/validation.h b/src/validation.h
index 34217b3454..3eece8d2b9 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -31,6 +31,7 @@
 #include <utility>
 #include <vector>
 
+class CChainState;
 class CBlockIndex;
 class CBlockTreeDB;
 class CBlockUndo;
@@ -277,10 +278,6 @@ void PruneOneBlockFile(const int fileNumber) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  */
 void UnlinkPrunedFiles(const std::set<int>& setFilesToPrune);
 
-/** Flush all state, indexes and buffers to disk. */
-void FlushStateToDisk();
-/** Prune block files and flush state to disk. */
-void PruneAndFlush();
 /** Prune block files up to a given height */
 void PruneBlockFilesManual(int nManualPruneHeight);
 
@@ -432,6 +429,14 @@ enum DisconnectResult
 
 class ConnectTrace;
 
+/** @see CChainState::FlushStateToDisk */
+enum class FlushStateMode {
+    NONE,
+    IF_NEEDED,
+    PERIODIC,
+    ALWAYS
+};
+
 struct CBlockIndexWorkComparator
 {
     bool operator()(const CBlockIndex *pa, const CBlockIndex *pb) const;
@@ -508,6 +513,28 @@ public:
 
     bool LoadBlockIndex(const Consensus::Params& consensus_params, CBlockTreeDB& blocktree) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
+    /**
+     * Update the on-disk chain state.
+     * The caches and indexes are flushed depending on the mode we're called with
+     * if they're too large, if it's been a while since the last write,
+     * or always and in all cases if we're in prune mode and are deleting files.
+     *
+     * If FlushStateMode::NONE is used, then FlushStateToDisk(...) won't do anything
+     * besides checking if we need to prune.
+     */
+    bool FlushStateToDisk(
+        const CChainParams& chainparams,
+        CValidationState &state,
+        FlushStateMode mode,
+        int nManualPruneHeight = 0);
+
+    //! Unconditionally flush all changes to disk.
+    void ForceFlushStateToDisk();
+
+    //! Prune blockfiles from the disk if necessary and then flush chainstate changes
+    //! if we pruned.
+    void PruneAndFlush();
+
     bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams, std::shared_ptr<const CBlock> pblock) LOCKS_EXCLUDED(cs_main);
 
     /**