Initial Vexta Core v0.1.0 release

src/index/base.h

@@ -0,0 +1,132 @@
+// Copyright (c) 2017-2020 The Bitcoin Core developers
+// Copyright (c) 2017-2020 The DigiByte Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef DIGIBYTE_INDEX_BASE_H
+#define DIGIBYTE_INDEX_BASE_H
+
+#include <dbwrapper.h>
+#include <primitives/block.h>
+#include <primitives/transaction.h>
+#include <threadinterrupt.h>
+#include <validationinterface.h>
+
+class CBlockIndex;
+class CChainState;
+
+struct IndexSummary {
+    std::string name;
+    bool synced{false};
+    int best_block_height{0};
+};
+
+/**
+ * Base class for indices of blockchain data. This implements
+ * CValidationInterface and ensures blocks are indexed sequentially according
+ * to their position in the active chain.
+ */
+class BaseIndex : public CValidationInterface
+{
+protected:
+    /**
+     * The database stores a block locator of the chain the database is synced to
+     * so that the index can efficiently determine the point it last stopped at.
+     * A locator is used instead of a simple hash of the chain tip because blocks
+     * and block index entries may not be flushed to disk until after this database
+     * is updated.
+    */
+    class DB : public CDBWrapper
+    {
+    public:
+        DB(const fs::path& path, size_t n_cache_size,
+           bool f_memory = false, bool f_wipe = false, bool f_obfuscate = false);
+
+        /// Read block locator of the chain that the txindex is in sync with.
+        bool ReadBestBlock(CBlockLocator& locator) const;
+
+        /// Write block locator of the chain that the txindex is in sync with.
+        void WriteBestBlock(CDBBatch& batch, const CBlockLocator& locator);
+    };
+
+private:
+    /// Whether the index is in sync with the main chain. The flag is flipped
+    /// from false to true once, after which point this starts processing
+    /// ValidationInterface notifications to stay in sync.
+    std::atomic<bool> m_synced{false};
+
+    /// The last block in the chain that the index is in sync with.
+    std::atomic<const CBlockIndex*> m_best_block_index{nullptr};
+
+    std::thread m_thread_sync;
+    CThreadInterrupt m_interrupt;
+
+    /// Sync the index with the block index starting from the current best block.
+    /// Intended to be run in its own thread, m_thread_sync, and can be
+    /// interrupted with m_interrupt. Once the index gets in sync, the m_synced
+    /// flag is set and the BlockConnected ValidationInterface callback takes
+    /// over and the sync thread exits.
+    void ThreadSync();
+
+    /// Write the current index state (eg. chain block locator and subclass-specific items) to disk.
+    ///
+    /// Recommendations for error handling:
+    /// If called on a successor of the previous committed best block in the index, the index can
+    /// continue processing without risk of corruption, though the index state will need to catch up
+    /// from further behind on reboot. If the new state is not a successor of the previous state (due
+    /// to a chain reorganization), the index must halt until Commit succeeds or else it could end up
+    /// getting corrupted.
+    bool Commit();
+protected:
+    CChainState* m_chainstate{nullptr};
+
+    void BlockConnected(const std::shared_ptr<const CBlock>& block, const CBlockIndex* pindex) override;
+
+    void ChainStateFlushed(const CBlockLocator& locator) override;
+
+    const CBlockIndex* CurrentIndex() { return m_best_block_index.load(); };
+
+    /// Initialize internal state from the database and block index.
+    [[nodiscard]] virtual bool Init();
+
+    /// Write update index entries for a newly connected block.
+    virtual bool WriteBlock(const CBlock& block, const CBlockIndex* pindex) { return true; }
+
+    /// Virtual method called internally by Commit that can be overridden to atomically
+    /// commit more index state.
+    virtual bool CommitInternal(CDBBatch& batch);
+
+    /// Rewind index to an earlier chain tip during a chain reorg. The tip must
+    /// be an ancestor of the current best block.
+    virtual bool Rewind(const CBlockIndex* current_tip, const CBlockIndex* new_tip);
+
+    virtual DB& GetDB() const = 0;
+
+    /// Get the name of the index for display in logs.
+    virtual const char* GetName() const = 0;
+
+public:
+    /// Destructor interrupts sync thread if running and blocks until it exits.
+    virtual ~BaseIndex();
+
+    /// Blocks the current thread until the index is caught up to the current
+    /// state of the block chain. This only blocks if the index has gotten in
+    /// sync once and only needs to process blocks in the ValidationInterface
+    /// queue. If the index is catching up from far behind, this method does
+    /// not block and immediately returns false.
+    bool BlockUntilSyncedToCurrentChain() const LOCKS_EXCLUDED(::cs_main);
+
+    void Interrupt();
+
+    /// Start initializes the sync state and registers the instance as a
+    /// ValidationInterface so that it stays in sync with blockchain updates.
+    [[nodiscard]] bool Start(CChainState& active_chainstate);
+
+    /// Stops the instance from staying in sync with blockchain updates.
+    void Stop();
+
+    /// Get a summary of the index and its state.
+    IndexSummary GetSummary() const;
+};
+
+#endif // DIGIBYTE_INDEX_BASE_H