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// Copyright (c) 2017-2021 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#ifndef BITCOIN_INDEX_BASE_H
#define BITCOIN_INDEX_BASE_H
#include <dbwrapper.h>
#include <threadinterrupt.h>
#include <validationinterface.h>
class CBlock;
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 index is in sync with.
bool ReadBestBlock(CBlockLocator& locator) const;
/// Write block locator of the chain that the index 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.
///
/// Note that this will latch to true *immediately* upon startup if
/// `m_chainstate->m_chain` is empty, which will be the case upon startup
/// with an empty datadir if, e.g., `-txindex=1` is specified.
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();
virtual bool AllowPrune() const = 0;
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;
/// Update the internal best block index as well as the prune lock.
void SetBestBlockIndex(const CBlockIndex* block);
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 // BITCOIN_INDEX_BASE_H
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