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1 : : // Copyright (c) 2009-2010 Satoshi Nakamoto
2 : : // Copyright (c) 2009-2022 The Bitcoin Core developers
3 : : // Distributed under the MIT software license, see the accompanying
4 : : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
5 : :
6 : : #ifndef BITCOIN_VALIDATIONINTERFACE_H
7 : : #define BITCOIN_VALIDATIONINTERFACE_H
8 : :
9 : : #include <kernel/chain.h>
10 : : #include <kernel/cs_main.h>
11 : : #include <primitives/transaction.h> // CTransaction(Ref)
12 : : #include <sync.h>
13 : :
14 : : #include <cstddef>
15 : : #include <cstdint>
16 : : #include <functional>
17 : : #include <memory>
18 : : #include <vector>
19 : :
20 : : namespace util {
21 : : class TaskRunnerInterface;
22 : : } // namespace util
23 : :
24 : : class BlockValidationState;
25 : : class CBlock;
26 : : class CBlockIndex;
27 : : struct CBlockLocator;
28 : : enum class MemPoolRemovalReason;
29 : : struct RemovedMempoolTransactionInfo;
30 : : struct NewMempoolTransactionInfo;
31 : :
32 : : /**
33 : : * Implement this to subscribe to events generated in validation and mempool
34 : : *
35 : : * Each CValidationInterface() subscriber will receive event callbacks
36 : : * in the order in which the events were generated by validation and mempool.
37 : : * Furthermore, each ValidationInterface() subscriber may assume that
38 : : * callbacks effectively run in a single thread with single-threaded
39 : : * memory consistency. That is, for a given ValidationInterface()
40 : : * instantiation, each callback will complete before the next one is
41 : : * invoked. This means, for example when a block is connected that the
42 : : * UpdatedBlockTip() callback may depend on an operation performed in
43 : : * the BlockConnected() callback without worrying about explicit
44 : : * synchronization. No ordering should be assumed across
45 : : * ValidationInterface() subscribers.
46 : : */
47 [ # # ]: 0 : class CValidationInterface {
48 : : protected:
49 : : /**
50 : : * Protected destructor so that instances can only be deleted by derived classes.
51 : : * If that restriction is no longer desired, this should be made public and virtual.
52 : : */
53 : : ~CValidationInterface() = default;
54 : : /**
55 : : * Notifies listeners when the block chain tip advances.
56 : : *
57 : : * When multiple blocks are connected at once, UpdatedBlockTip will be called on the final tip
58 : : * but may not be called on every intermediate tip. If the latter behavior is desired,
59 : : * subscribe to BlockConnected() instead.
60 : : *
61 : : * Called on a background thread. Only called for the active chainstate.
62 : : */
63 : 0 : virtual void UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlockIndex *pindexFork, bool fInitialDownload) {}
64 : : /**
65 : : * Notifies listeners any time the block chain tip changes, synchronously.
66 : : */
67 : 0 : virtual void ActiveTipChange(const CBlockIndex& new_tip, bool is_ibd) {};
68 : : /**
69 : : * Notifies listeners of a transaction having been added to mempool.
70 : : *
71 : : * Called on a background thread.
72 : : */
73 : 0 : virtual void TransactionAddedToMempool(const NewMempoolTransactionInfo& tx, uint64_t mempool_sequence) {}
74 : :
75 : : /**
76 : : * Notifies listeners of a transaction leaving mempool.
77 : : *
78 : : * This notification fires for transactions that are removed from the
79 : : * mempool for the following reasons:
80 : : *
81 : : * - EXPIRY (expired from mempool after -mempoolexpiry hours)
82 : : * - SIZELIMIT (removed in size limiting if the mempool exceeds -maxmempool megabytes)
83 : : * - REORG (removed during a reorg)
84 : : * - CONFLICT (removed because it conflicts with in-block transaction)
85 : : * - REPLACED (removed due to RBF replacement)
86 : : *
87 : : * This does not fire for transactions that are removed from the mempool
88 : : * because they have been included in a block. Any client that is interested
89 : : * in transactions removed from the mempool for inclusion in a block can learn
90 : : * about those transactions from the MempoolTransactionsRemovedForBlock notification.
91 : : *
92 : : * Transactions that are removed from the mempool because they conflict
93 : : * with a transaction in the new block will have
94 : : * TransactionRemovedFromMempool events fired *before* the BlockConnected
95 : : * event is fired. If multiple blocks are connected in one step, then the
96 : : * ordering could be:
97 : : *
98 : : * - TransactionRemovedFromMempool(tx1 from block A)
99 : : * - TransactionRemovedFromMempool(tx2 from block A)
100 : : * - TransactionRemovedFromMempool(tx1 from block B)
101 : : * - TransactionRemovedFromMempool(tx2 from block B)
102 : : * - BlockConnected(A)
103 : : * - BlockConnected(B)
104 : : *
105 : : * Called on a background thread.
106 : : */
107 : 0 : virtual void TransactionRemovedFromMempool(const CTransactionRef& tx, MemPoolRemovalReason reason, uint64_t mempool_sequence) {}
108 : : /*
109 : : * Notifies listeners of transactions removed from the mempool as
110 : : * as a result of new block being connected.
111 : : * MempoolTransactionsRemovedForBlock will be fired before BlockConnected.
112 : : *
113 : : * Called on a background thread.
114 : : */
115 : 0 : virtual void MempoolTransactionsRemovedForBlock(const std::vector<RemovedMempoolTransactionInfo>& txs_removed_for_block, unsigned int nBlockHeight) {}
116 : : /**
117 : : * Notifies listeners of a block being connected.
118 : : * Provides a vector of transactions evicted from the mempool as a result.
119 : : *
120 : : * Called on a background thread.
121 : : */
122 : 0 : virtual void BlockConnected(ChainstateRole role, const std::shared_ptr<const CBlock> &block, const CBlockIndex *pindex) {}
123 : : /**
124 : : * Notifies listeners of a block being disconnected
125 : : * Provides the block that was disconnected.
126 : : *
127 : : * Called on a background thread. Only called for the active chainstate, since
128 : : * background chainstates should never disconnect blocks.
129 : : */
130 : 0 : virtual void BlockDisconnected(const std::shared_ptr<const CBlock> &block, const CBlockIndex* pindex) {}
131 : : /**
132 : : * Notifies listeners of the new active block chain on-disk.
133 : : *
134 : : * Prior to this callback, any updates are not guaranteed to persist on disk
135 : : * (ie clients need to handle shutdown/restart safety by being able to
136 : : * understand when some updates were lost due to unclean shutdown).
137 : : *
138 : : * When this callback is invoked, the validation changes done by any prior
139 : : * callback are guaranteed to exist on disk and survive a restart, including
140 : : * an unclean shutdown.
141 : : *
142 : : * Provides a locator describing the best chain, which is likely useful for
143 : : * storing current state on disk in client DBs.
144 : : *
145 : : * Called on a background thread.
146 : : */
147 : 0 : virtual void ChainStateFlushed(ChainstateRole role, const CBlockLocator &locator) {}
148 : : /**
149 : : * Notifies listeners of a block validation result.
150 : : * If the provided BlockValidationState IsValid, the provided block
151 : : * is guaranteed to be the current best block at the time the
152 : : * callback was generated (not necessarily now).
153 : : */
154 : 0 : virtual void BlockChecked(const CBlock&, const BlockValidationState&) {}
155 : : /**
156 : : * Notifies listeners that a block which builds directly on our current tip
157 : : * has been received and connected to the headers tree, though not validated yet.
158 : : */
159 : 0 : virtual void NewPoWValidBlock(const CBlockIndex *pindex, const std::shared_ptr<const CBlock>& block) {};
160 : : friend class ValidationSignals;
161 : : friend class ValidationInterfaceTest;
162 : : };
163 : :
164 : : class ValidationSignalsImpl;
165 : : class ValidationSignals {
166 : : private:
167 : : std::unique_ptr<ValidationSignalsImpl> m_internals;
168 : :
169 : : public:
170 : : // The task runner will block validation if it calls its insert method's
171 : : // func argument synchronously. In this class func contains a loop that
172 : : // dispatches a single validation event to all subscribers sequentially.
173 : : explicit ValidationSignals(std::unique_ptr<util::TaskRunnerInterface> task_runner);
174 : :
175 : : ~ValidationSignals();
176 : :
177 : : /** Call any remaining callbacks on the calling thread */
178 : : void FlushBackgroundCallbacks();
179 : :
180 : : size_t CallbacksPending();
181 : :
182 : : /** Register subscriber */
183 : : void RegisterValidationInterface(CValidationInterface* callbacks);
184 : : /** Unregister subscriber. DEPRECATED. This is not safe to use when the RPC server or main message handler thread is running. */
185 : : void UnregisterValidationInterface(CValidationInterface* callbacks);
186 : : /** Unregister all subscribers */
187 : : void UnregisterAllValidationInterfaces();
188 : :
189 : : // Alternate registration functions that release a shared_ptr after the last
190 : : // notification is sent. These are useful for race-free cleanup, since
191 : : // unregistration is nonblocking and can return before the last notification is
192 : : // processed.
193 : : /** Register subscriber */
194 : : void RegisterSharedValidationInterface(std::shared_ptr<CValidationInterface> callbacks);
195 : : /** Unregister subscriber */
196 : : void UnregisterSharedValidationInterface(std::shared_ptr<CValidationInterface> callbacks);
197 : :
198 : : /**
199 : : * Pushes a function to callback onto the notification queue, guaranteeing any
200 : : * callbacks generated prior to now are finished when the function is called.
201 : : *
202 : : * Be very careful blocking on func to be called if any locks are held -
203 : : * validation interface clients may not be able to make progress as they often
204 : : * wait for things like cs_main, so blocking until func is called with cs_main
205 : : * will result in a deadlock (that DEBUG_LOCKORDER will miss).
206 : : */
207 : : void CallFunctionInValidationInterfaceQueue(std::function<void ()> func);
208 : :
209 : : /**
210 : : * This is a synonym for the following, which asserts certain locks are not
211 : : * held:
212 : : * std::promise<void> promise;
213 : : * CallFunctionInValidationInterfaceQueue([&promise] {
214 : : * promise.set_value();
215 : : * });
216 : : * promise.get_future().wait();
217 : : */
218 : : void SyncWithValidationInterfaceQueue() LOCKS_EXCLUDED(cs_main);
219 : :
220 : : void UpdatedBlockTip(const CBlockIndex *, const CBlockIndex *, bool fInitialDownload);
221 : : void ActiveTipChange(const CBlockIndex&, bool);
222 : : void TransactionAddedToMempool(const NewMempoolTransactionInfo&, uint64_t mempool_sequence);
223 : : void TransactionRemovedFromMempool(const CTransactionRef&, MemPoolRemovalReason, uint64_t mempool_sequence);
224 : : void MempoolTransactionsRemovedForBlock(const std::vector<RemovedMempoolTransactionInfo>&, unsigned int nBlockHeight);
225 : : void BlockConnected(ChainstateRole, const std::shared_ptr<const CBlock> &, const CBlockIndex *pindex);
226 : : void BlockDisconnected(const std::shared_ptr<const CBlock> &, const CBlockIndex* pindex);
227 : : void ChainStateFlushed(ChainstateRole, const CBlockLocator &);
228 : : void BlockChecked(const CBlock&, const BlockValidationState&);
229 : : void NewPoWValidBlock(const CBlockIndex *, const std::shared_ptr<const CBlock>&);
230 : : };
231 : :
232 : : #endif // BITCOIN_VALIDATIONINTERFACE_H
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