move-only: make the CChainState interface public

along with DisconnectResult, and CBlockIndexWorkComparator.

The CChainState interface needs to be known to the rest of the system because
many global functions will move to CChainState methods. This is to allow
other parts of the system to be parameterized per chainstate instance
instead of assuming a single global.

1 files changed, 140 insertions, 0 deletions

diff --git a/src/validation.h b/src/validation.h
index 3cd64bc391..8114d42d37 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -44,6 +44,7 @@ class CTxMemPool;
 class CValidationState;
 struct ChainTxData;
 
+struct DisconnectedBlockTransactions;
 struct PrecomputedTransactionData;
 struct LockPoints;
 
@@ -422,6 +423,145 @@ inline CBlockIndex* LookupBlockIndex(const uint256& hash)
 /** Find the last common block between the parameter chain and a locator. */
 CBlockIndex* FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& locator) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
+enum DisconnectResult
+{
+    DISCONNECT_OK,      // All good.
+    DISCONNECT_UNCLEAN, // Rolled back, but UTXO set was inconsistent with block.
+    DISCONNECT_FAILED   // Something else went wrong.
+};
+
+class ConnectTrace;
+
+struct CBlockIndexWorkComparator
+{
+    bool operator()(const CBlockIndex *pa, const CBlockIndex *pb) const;
+};
+
+/**
+ * CChainState stores and provides an API to update our local knowledge of the
+ * current best chain and header tree.
+ *
+ * It generally provides access to the current block tree, as well as functions
+ * to provide new data, which it will appropriately validate and incorporate in
+ * its state as necessary.
+ *
+ * Eventually, the API here is targeted at being exposed externally as a
+ * consumable libconsensus library, so any functions added must only call
+ * other class member functions, pure functions in other parts of the consensus
+ * library, callbacks via the validation interface, or read/write-to-disk
+ * functions (eventually this will also be via callbacks).
+ */
+class CChainState {
+private:
+    /**
+     * The set of all CBlockIndex entries with BLOCK_VALID_TRANSACTIONS (for itself and all ancestors) and
+     * as good as our current tip or better. Entries may be failed, though, and pruning nodes may be
+     * missing the data for the block.
+     */
+    std::set<CBlockIndex*, CBlockIndexWorkComparator> setBlockIndexCandidates;
+
+    /**
+     * Every received block is assigned a unique and increasing identifier, so we
+     * know which one to give priority in case of a fork.
+     */
+    CCriticalSection cs_nBlockSequenceId;
+    /** Blocks loaded from disk are assigned id 0, so start the counter at 1. */
+    int32_t nBlockSequenceId = 1;
+    /** Decreasing counter (used by subsequent preciousblock calls). */
+    int32_t nBlockReverseSequenceId = -1;
+    /** chainwork for the last block that preciousblock has been applied to. */
+    arith_uint256 nLastPreciousChainwork = 0;
+
+    /** In order to efficiently track invalidity of headers, we keep the set of
+      * blocks which we tried to connect and found to be invalid here (ie which
+      * were set to BLOCK_FAILED_VALID since the last restart). We can then
+      * walk this set and check if a new header is a descendant of something in
+      * this set, preventing us from having to walk mapBlockIndex when we try
+      * to connect a bad block and fail.
+      *
+      * While this is more complicated than marking everything which descends
+      * from an invalid block as invalid at the time we discover it to be
+      * invalid, doing so would require walking all of mapBlockIndex to find all
+      * descendants. Since this case should be very rare, keeping track of all
+      * BLOCK_FAILED_VALID blocks in a set should be just fine and work just as
+      * well.
+      *
+      * Because we already walk mapBlockIndex in height-order at startup, we go
+      * ahead and mark descendants of invalid blocks as FAILED_CHILD at that time,
+      * instead of putting things in this set.
+      */
+    std::set<CBlockIndex*> m_failed_blocks;
+
+    /**
+     * the ChainState CriticalSection
+     * A lock that must be held when modifying this ChainState - held in ActivateBestChain()
+     */
+    CCriticalSection m_cs_chainstate;
+
+public:
+    //! The current chain of blockheaders we consult and build on.
+    //! @see CChain, CBlockIndex.
+    CChain m_chain;
+    BlockMap mapBlockIndex GUARDED_BY(cs_main);
+    std::multimap<CBlockIndex*, CBlockIndex*> mapBlocksUnlinked;
+    CBlockIndex *pindexBestInvalid = nullptr;
+
+    bool LoadBlockIndex(const Consensus::Params& consensus_params, CBlockTreeDB& blocktree) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
+    bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams, std::shared_ptr<const CBlock> pblock) LOCKS_EXCLUDED(cs_main);
+
+    /**
+     * If a block header hasn't already been seen, call CheckBlockHeader on it, ensure
+     * that it doesn't descend from an invalid block, and then add it to mapBlockIndex.
+     */
+    bool AcceptBlockHeader(const CBlockHeader& block, CValidationState& state, const CChainParams& chainparams, CBlockIndex** ppindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+    bool AcceptBlock(const std::shared_ptr<const CBlock>& pblock, CValidationState& state, const CChainParams& chainparams, CBlockIndex** ppindex, bool fRequested, const FlatFilePos* dbp, bool* fNewBlock) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
+    // Block (dis)connection on a given view:
+    DisconnectResult DisconnectBlock(const CBlock& block, const CBlockIndex* pindex, CCoinsViewCache& view);
+    bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pindex,
+                      CCoinsViewCache& view, const CChainParams& chainparams, bool fJustCheck = false) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
+    // Block disconnection on our pcoinsTip:
+    bool DisconnectTip(CValidationState& state, const CChainParams& chainparams, DisconnectedBlockTransactions* disconnectpool) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
+    // Manual block validity manipulation:
+    bool PreciousBlock(CValidationState& state, const CChainParams& params, CBlockIndex* pindex) LOCKS_EXCLUDED(cs_main);
+    bool InvalidateBlock(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindex) LOCKS_EXCLUDED(cs_main);
+    void ResetBlockFailureFlags(CBlockIndex* pindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
+    bool ReplayBlocks(const CChainParams& params, CCoinsView* view);
+    bool RewindBlockIndex(const CChainParams& params) LOCKS_EXCLUDED(cs_main);
+    bool LoadGenesisBlock(const CChainParams& chainparams);
+
+    void PruneBlockIndexCandidates();
+
+    void UnloadBlockIndex();
+
+private:
+    bool ActivateBestChainStep(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexMostWork, const std::shared_ptr<const CBlock>& pblock, bool& fInvalidFound, ConnectTrace& connectTrace) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+    bool ConnectTip(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexNew, const std::shared_ptr<const CBlock>& pblock, ConnectTrace& connectTrace, DisconnectedBlockTransactions &disconnectpool) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
+    CBlockIndex* AddToBlockIndex(const CBlockHeader& block) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+    /** Create a new block index entry for a given block hash */
+    CBlockIndex* InsertBlockIndex(const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+    /**
+     * Make various assertions about the state of the block index.
+     *
+     * By default this only executes fully when using the Regtest chain; see: fCheckBlockIndex.
+     */
+    void CheckBlockIndex(const Consensus::Params& consensusParams);
+
+    void InvalidBlockFound(CBlockIndex *pindex, const CValidationState &state) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+    CBlockIndex* FindMostWorkChain() EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+    void ReceivedBlockTransactions(const CBlock& block, CBlockIndex* pindexNew, const FlatFilePos& pos, const Consensus::Params& consensusParams) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
+    bool RollforwardBlock(const CBlockIndex* pindex, CCoinsViewCache& inputs, const CChainParams& params) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
+    //! Mark a block as not having block data
+    void EraseBlockData(CBlockIndex* index) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+};
+
 /** Mark a block as precious and reorganize.
  *
  * May not be called in a