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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2022 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_VALIDATIONINTERFACE_H
#define BITCOIN_VALIDATIONINTERFACE_H
#include <kernel/cs_main.h>
#include <kernel/chain.h>
#include <primitives/transaction.h> // CTransaction(Ref)
#include <sync.h>
#include <functional>
#include <memory>
class BlockValidationState;
class CBlock;
class CBlockIndex;
struct CBlockLocator;
class CValidationInterface;
class CScheduler;
enum class MemPoolRemovalReason;
/** Register subscriber */
void RegisterValidationInterface(CValidationInterface* callbacks);
/** Unregister subscriber. DEPRECATED. This is not safe to use when the RPC server or main message handler thread is running. */
void UnregisterValidationInterface(CValidationInterface* callbacks);
/** Unregister all subscribers */
void UnregisterAllValidationInterfaces();
// Alternate registration functions that release a shared_ptr after the last
// notification is sent. These are useful for race-free cleanup, since
// unregistration is nonblocking and can return before the last notification is
// processed.
/** Register subscriber */
void RegisterSharedValidationInterface(std::shared_ptr<CValidationInterface> callbacks);
/** Unregister subscriber */
void UnregisterSharedValidationInterface(std::shared_ptr<CValidationInterface> callbacks);
/**
* Pushes a function to callback onto the notification queue, guaranteeing any
* callbacks generated prior to now are finished when the function is called.
*
* Be very careful blocking on func to be called if any locks are held -
* validation interface clients may not be able to make progress as they often
* wait for things like cs_main, so blocking until func is called with cs_main
* will result in a deadlock (that DEBUG_LOCKORDER will miss).
*/
void CallFunctionInValidationInterfaceQueue(std::function<void ()> func);
/**
* This is a synonym for the following, which asserts certain locks are not
* held:
* std::promise<void> promise;
* CallFunctionInValidationInterfaceQueue([&promise] {
* promise.set_value();
* });
* promise.get_future().wait();
*/
void SyncWithValidationInterfaceQueue() LOCKS_EXCLUDED(cs_main);
/**
* Implement this to subscribe to events generated in validation
*
* Each CValidationInterface() subscriber will receive event callbacks
* in the order in which the events were generated by validation.
* Furthermore, each ValidationInterface() subscriber may assume that
* callbacks effectively run in a single thread with single-threaded
* memory consistency. That is, for a given ValidationInterface()
* instantiation, each callback will complete before the next one is
* invoked. This means, for example when a block is connected that the
* UpdatedBlockTip() callback may depend on an operation performed in
* the BlockConnected() callback without worrying about explicit
* synchronization. No ordering should be assumed across
* ValidationInterface() subscribers.
*/
class CValidationInterface {
protected:
/**
* Protected destructor so that instances can only be deleted by derived classes.
* If that restriction is no longer desired, this should be made public and virtual.
*/
~CValidationInterface() = default;
/**
* Notifies listeners when the block chain tip advances.
*
* When multiple blocks are connected at once, UpdatedBlockTip will be called on the final tip
* but may not be called on every intermediate tip. If the latter behavior is desired,
* subscribe to BlockConnected() instead.
*
* Called on a background thread. Only called for the active chainstate.
*/
virtual void UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlockIndex *pindexFork, bool fInitialDownload) {}
/**
* Notifies listeners of a transaction having been added to mempool.
*
* Called on a background thread.
*/
virtual void TransactionAddedToMempool(const CTransactionRef& tx, uint64_t mempool_sequence) {}
/**
* Notifies listeners of a transaction leaving mempool.
*
* This notification fires for transactions that are removed from the
* mempool for the following reasons:
*
* - EXPIRY (expired from mempool after -mempoolexpiry hours)
* - SIZELIMIT (removed in size limiting if the mempool exceeds -maxmempool megabytes)
* - REORG (removed during a reorg)
* - CONFLICT (removed because it conflicts with in-block transaction)
* - REPLACED (removed due to RBF replacement)
*
* This does not fire for transactions that are removed from the mempool
* because they have been included in a block. Any client that is interested
* in transactions removed from the mempool for inclusion in a block can learn
* about those transactions from the BlockConnected notification.
*
* Transactions that are removed from the mempool because they conflict
* with a transaction in the new block will have
* TransactionRemovedFromMempool events fired *before* the BlockConnected
* event is fired. If multiple blocks are connected in one step, then the
* ordering could be:
*
* - TransactionRemovedFromMempool(tx1 from block A)
* - TransactionRemovedFromMempool(tx2 from block A)
* - TransactionRemovedFromMempool(tx1 from block B)
* - TransactionRemovedFromMempool(tx2 from block B)
* - BlockConnected(A)
* - BlockConnected(B)
*
* Called on a background thread.
*/
virtual void TransactionRemovedFromMempool(const CTransactionRef& tx, MemPoolRemovalReason reason, uint64_t mempool_sequence) {}
/**
* Notifies listeners of a block being connected.
* Provides a vector of transactions evicted from the mempool as a result.
*
* Called on a background thread.
*/
virtual void BlockConnected(ChainstateRole role, const std::shared_ptr<const CBlock> &block, const CBlockIndex *pindex) {}
/**
* Notifies listeners of a block being disconnected
*
* Called on a background thread. Only called for the active chainstate, since
* background chainstates should never disconnect blocks.
*/
virtual void BlockDisconnected(const std::shared_ptr<const CBlock> &block, const CBlockIndex* pindex) {}
/**
* Notifies listeners of the new active block chain on-disk.
*
* Prior to this callback, any updates are not guaranteed to persist on disk
* (ie clients need to handle shutdown/restart safety by being able to
* understand when some updates were lost due to unclean shutdown).
*
* When this callback is invoked, the validation changes done by any prior
* callback are guaranteed to exist on disk and survive a restart, including
* an unclean shutdown.
*
* Provides a locator describing the best chain, which is likely useful for
* storing current state on disk in client DBs.
*
* Called on a background thread.
*/
virtual void ChainStateFlushed(ChainstateRole role, const CBlockLocator &locator) {}
/**
* Notifies listeners of a block validation result.
* If the provided BlockValidationState IsValid, the provided block
* is guaranteed to be the current best block at the time the
* callback was generated (not necessarily now).
*/
virtual void BlockChecked(const CBlock&, const BlockValidationState&) {}
/**
* Notifies listeners that a block which builds directly on our current tip
* has been received and connected to the headers tree, though not validated yet.
*/
virtual void NewPoWValidBlock(const CBlockIndex *pindex, const std::shared_ptr<const CBlock>& block) {};
friend class CMainSignals;
friend class ValidationInterfaceTest;
};
class MainSignalsImpl;
class CMainSignals {
private:
std::unique_ptr<MainSignalsImpl> m_internals;
friend void ::RegisterSharedValidationInterface(std::shared_ptr<CValidationInterface>);
friend void ::UnregisterValidationInterface(CValidationInterface*);
friend void ::UnregisterAllValidationInterfaces();
friend void ::CallFunctionInValidationInterfaceQueue(std::function<void ()> func);
public:
/** Register a CScheduler to give callbacks which should run in the background (may only be called once) */
void RegisterBackgroundSignalScheduler(CScheduler& scheduler);
/** Unregister a CScheduler to give callbacks which should run in the background - these callbacks will now be dropped! */
void UnregisterBackgroundSignalScheduler();
/** Call any remaining callbacks on the calling thread */
void FlushBackgroundCallbacks();
size_t CallbacksPending();
void UpdatedBlockTip(const CBlockIndex *, const CBlockIndex *, bool fInitialDownload);
void TransactionAddedToMempool(const CTransactionRef&, uint64_t mempool_sequence);
void TransactionRemovedFromMempool(const CTransactionRef&, MemPoolRemovalReason, uint64_t mempool_sequence);
void BlockConnected(ChainstateRole, const std::shared_ptr<const CBlock> &, const CBlockIndex *pindex);
void BlockDisconnected(const std::shared_ptr<const CBlock> &, const CBlockIndex* pindex);
void ChainStateFlushed(ChainstateRole, const CBlockLocator &);
void BlockChecked(const CBlock&, const BlockValidationState&);
void NewPoWValidBlock(const CBlockIndex *, const std::shared_ptr<const CBlock>&);
};
CMainSignals& GetMainSignals();
#endif // BITCOIN_VALIDATIONINTERFACE_H
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