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1 : : // Copyright (c) 2009-2010 Satoshi Nakamoto
2 : : // Copyright (c) 2009-present 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_COINS_H
7 : : #define BITCOIN_COINS_H
8 : :
9 : : #include <compressor.h>
10 : : #include <core_memusage.h>
11 : : #include <memusage.h>
12 : : #include <primitives/transaction.h>
13 : : #include <serialize.h>
14 : : #include <support/allocators/pool.h>
15 : : #include <uint256.h>
16 : : #include <util/check.h>
17 : : #include <util/hasher.h>
18 : :
19 : : #include <cassert>
20 : : #include <cstdint>
21 : :
22 : : #include <functional>
23 : : #include <unordered_map>
24 : :
25 : : /**
26 : : * A UTXO entry.
27 : : *
28 : : * Serialized format:
29 : : * - VARINT((coinbase ? 1 : 0) | (height << 1))
30 : : * - the non-spent CTxOut (via TxOutCompression)
31 : : */
32 [ + + + + ]: 86629840 : class Coin
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33 : : {
34 : : public:
35 : : //! unspent transaction output
36 : : CTxOut out;
37 : :
38 : : //! whether containing transaction was a coinbase
39 : : unsigned int fCoinBase : 1;
40 : :
41 : : //! at which height this containing transaction was included in the active block chain
42 : : uint32_t nHeight : 31;
43 : :
44 : : //! construct a Coin from a CTxOut and height/coinbase information.
45 [ + + ]: 57 : Coin(CTxOut&& outIn, int nHeightIn, bool fCoinBaseIn) : out(std::move(outIn)), fCoinBase(fCoinBaseIn), nHeight(nHeightIn) {}
46 [ + - ]: 20170888 : Coin(const CTxOut& outIn, int nHeightIn, bool fCoinBaseIn) : out(outIn), fCoinBase(fCoinBaseIn),nHeight(nHeightIn) {}
[ + + + + ]
47 : :
48 : 12512711 : void Clear() {
49 : 12512711 : out.SetNull();
50 : 12512711 : fCoinBase = false;
51 [ - + + + : 12512711 : nHeight = 0;
+ - ]
52 : 12445026 : }
53 : :
54 : : //! empty constructor
55 [ + - # # : 75093547 : Coin() : fCoinBase(false), nHeight(0) { }
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56 : :
57 : 12809496 : bool IsCoinBase() const {
58 [ + + + + ]: 12809496 : return fCoinBase;
[ + + # # ]
59 : : }
60 : :
61 : : template<typename Stream>
62 : 296568 : void Serialize(Stream &s) const {
63 [ - + ]: 296568 : assert(!IsSpent());
64 : 296568 : uint32_t code = nHeight * uint32_t{2} + fCoinBase;
65 : 296568 : ::Serialize(s, VARINT(code));
66 : 296568 : ::Serialize(s, Using<TxOutCompression>(out));
67 : 296568 : }
68 : :
69 : : template<typename Stream>
70 : 304160 : void Unserialize(Stream &s) {
71 : 304160 : uint32_t code = 0;
72 : 304160 : ::Unserialize(s, VARINT(code));
73 : 304160 : nHeight = code >> 1;
74 : 304160 : fCoinBase = code & 1;
75 : 304160 : ::Unserialize(s, Using<TxOutCompression>(out));
76 : 304157 : }
77 : :
78 : : /** Either this coin never existed (see e.g. coinEmpty in coins.cpp), or it
79 : : * did exist and has been spent.
80 : : */
81 [ + - ]: 118909093 : bool IsSpent() const {
82 [ + + + + : 118168787 : return out.IsNull();
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83 : : }
84 : :
85 : 47398569 : size_t DynamicMemoryUsage() const {
86 [ + + + + : 48185764 : return memusage::DynamicUsage(out.scriptPubKey);
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87 : : }
88 : : };
89 : :
90 : : struct CCoinsCacheEntry;
91 : : using CoinsCachePair = std::pair<const COutPoint, CCoinsCacheEntry>;
92 : :
93 : : /**
94 : : * A Coin in one level of the coins database caching hierarchy.
95 : : *
96 : : * A coin can either be:
97 : : * - unspent or spent (in which case the Coin object will be nulled out - see Coin.Clear())
98 : : * - DIRTY or not DIRTY
99 : : * - FRESH or not FRESH
100 : : *
101 : : * Out of these 2^3 = 8 states, only some combinations are valid:
102 : : * - unspent, FRESH, DIRTY (e.g. a new coin created in the cache)
103 : : * - unspent, not FRESH, DIRTY (e.g. a coin changed in the cache during a reorg)
104 : : * - unspent, not FRESH, not DIRTY (e.g. an unspent coin fetched from the parent cache)
105 : : * - spent, FRESH, not DIRTY (e.g. a spent coin fetched from the parent cache)
106 : : * - spent, not FRESH, DIRTY (e.g. a coin is spent and spentness needs to be flushed to the parent)
107 : : */
108 : : struct CCoinsCacheEntry
109 : : {
110 : : private:
111 : : /**
112 : : * These are used to create a doubly linked list of flagged entries.
113 : : * They are set in SetDirty, SetFresh, and unset in SetClean.
114 : : * A flagged entry is any entry that is either DIRTY, FRESH, or both.
115 : : *
116 : : * DIRTY entries are tracked so that only modified entries can be passed to
117 : : * the parent cache for batch writing. This is a performance optimization
118 : : * compared to giving all entries in the cache to the parent and having the
119 : : * parent scan for only modified entries.
120 : : *
121 : : * FRESH-but-not-DIRTY coins can not occur in practice, since that would
122 : : * mean a spent coin exists in the parent CCoinsView and not in the child
123 : : * CCoinsViewCache. Nevertheless, if a spent coin is retrieved from the
124 : : * parent cache, the FRESH-but-not-DIRTY coin will be tracked by the linked
125 : : * list and deleted when Sync or Flush is called on the CCoinsViewCache.
126 : : */
127 : : CoinsCachePair* m_prev{nullptr};
128 : : CoinsCachePair* m_next{nullptr};
129 : : uint8_t m_flags{0};
130 : :
131 : : //! Adding a flag requires a reference to the sentinel of the flagged pair linked list.
132 : 52822504 : static void AddFlags(uint8_t flags, CoinsCachePair& pair, CoinsCachePair& sentinel) noexcept
133 : : {
134 : 52822504 : Assume(flags & (DIRTY | FRESH));
135 : 52822504 : if (!pair.second.m_flags) {
136 : 32953280 : Assume(!pair.second.m_prev && !pair.second.m_next);
137 : 32953280 : pair.second.m_prev = sentinel.second.m_prev;
138 : 32953280 : pair.second.m_next = &sentinel;
139 : 32953280 : sentinel.second.m_prev = &pair;
140 : 32953280 : pair.second.m_prev->second.m_next = &pair;
141 : : }
142 : 52822504 : Assume(pair.second.m_prev && pair.second.m_next);
143 : 52822504 : pair.second.m_flags |= flags;
144 : : }
145 : :
146 : : public:
147 : : Coin coin; // The actual cached data.
148 : :
149 : : enum Flags {
150 : : /**
151 : : * DIRTY means the CCoinsCacheEntry is potentially different from the
152 : : * version in the parent cache. Failure to mark a coin as DIRTY when
153 : : * it is potentially different from the parent cache will cause a
154 : : * consensus failure, since the coin's state won't get written to the
155 : : * parent when the cache is flushed.
156 : : */
157 : : DIRTY = (1 << 0),
158 : : /**
159 : : * FRESH means the parent cache does not have this coin or that it is a
160 : : * spent coin in the parent cache. If a FRESH coin in the cache is
161 : : * later spent, it can be deleted entirely and doesn't ever need to be
162 : : * flushed to the parent. This is a performance optimization. Marking a
163 : : * coin as FRESH when it exists unspent in the parent cache will cause a
164 : : * consensus failure, since it might not be deleted from the parent
165 : : * when this cache is flushed.
166 : : */
167 : : FRESH = (1 << 1),
168 : : };
169 : :
170 : 58688142 : CCoinsCacheEntry() noexcept = default;
171 : 6048 : explicit CCoinsCacheEntry(Coin&& coin_) noexcept : coin(std::move(coin_)) {}
172 : 58694510 : ~CCoinsCacheEntry()
173 : : {
174 : 117389020 : SetClean();
175 : 58694510 : }
176 : :
177 [ + - + + : 65608273 : static void SetDirty(CoinsCachePair& pair, CoinsCachePair& sentinel) noexcept { AddFlags(DIRTY, pair, sentinel); }
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178 [ + + ][ + - : 20167511 : static void SetFresh(CoinsCachePair& pair, CoinsCachePair& sentinel) noexcept { AddFlags(FRESH, pair, sentinel); }
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179 : :
180 : 58749577 : void SetClean() noexcept
181 : : {
182 [ + + ][ + - : 58694516 : if (!m_flags) return;
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183 : 33480739 : m_next->second.m_prev = m_prev;
184 : 33480739 : m_prev->second.m_next = m_next;
185 : 33480739 : m_flags = 0;
186 : 33480739 : m_prev = m_next = nullptr;
187 : : }
188 [ + + + + : 21356235 : bool IsDirty() const noexcept { return m_flags & DIRTY; }
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189 [ + + + + : 13624551 : bool IsFresh() const noexcept { return m_flags & FRESH; }
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190 : :
191 : : //! Only call Next when this entry is DIRTY, FRESH, or both
192 : 1412731 : CoinsCachePair* Next() const noexcept
193 : : {
194 : 1412732 : Assume(m_flags);
195 [ - + ][ + - : 1089786 : return m_next;
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196 : : }
197 : :
198 : : //! Only call Prev when this entry is DIRTY, FRESH, or both
199 : 179075 : CoinsCachePair* Prev() const noexcept
200 : : {
201 : 179075 : Assume(m_flags);
202 [ - + - + ]: 89557 : return m_prev;
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203 : : }
204 : :
205 : : //! Only use this for initializing the linked list sentinel
206 : 527459 : void SelfRef(CoinsCachePair& pair) noexcept
207 : : {
208 : 527459 : Assume(&pair.second == this);
209 : 527459 : m_prev = &pair;
210 : 527459 : m_next = &pair;
211 : : // Set sentinel to DIRTY so we can call Next on it
212 [ + - ][ + - : 527459 : m_flags = DIRTY;
+ - + - ]
213 : : }
214 : : };
215 : :
216 : : /**
217 : : * PoolAllocator's MAX_BLOCK_SIZE_BYTES parameter here uses sizeof the data, and adds the size
218 : : * of 4 pointers. We do not know the exact node size used in the std::unordered_node implementation
219 : : * because it is implementation defined. Most implementations have an overhead of 1 or 2 pointers,
220 : : * so nodes can be connected in a linked list, and in some cases the hash value is stored as well.
221 : : * Using an additional sizeof(void*)*4 for MAX_BLOCK_SIZE_BYTES should thus be sufficient so that
222 : : * all implementations can allocate the nodes from the PoolAllocator.
223 : : */
224 : : using CCoinsMap = std::unordered_map<COutPoint,
225 : : CCoinsCacheEntry,
226 : : SaltedOutpointHasher,
227 : : std::equal_to<COutPoint>,
228 : : PoolAllocator<CoinsCachePair,
229 : : sizeof(CoinsCachePair) + sizeof(void*) * 4>>;
230 : :
231 : : using CCoinsMapMemoryResource = CCoinsMap::allocator_type::ResourceType;
232 : :
233 : : /** Cursor for iterating over CoinsView state */
234 : : class CCoinsViewCursor
235 : : {
236 : : public:
237 : 1196 : CCoinsViewCursor(const uint256 &hashBlockIn): hashBlock(hashBlockIn) {}
238 : 1196 : virtual ~CCoinsViewCursor() = default;
239 : :
240 : : virtual bool GetKey(COutPoint &key) const = 0;
241 : : virtual bool GetValue(Coin &coin) const = 0;
242 : :
243 : : virtual bool Valid() const = 0;
244 : : virtual void Next() = 0;
245 : :
246 : : //! Get best block at the time this cursor was created
247 : : const uint256 &GetBestBlock() const { return hashBlock; }
248 : : private:
249 : : uint256 hashBlock;
250 : : };
251 : :
252 : : /**
253 : : * Cursor for iterating over the linked list of flagged entries in CCoinsViewCache.
254 : : *
255 : : * This is a helper struct to encapsulate the diverging logic between a non-erasing
256 : : * CCoinsViewCache::Sync and an erasing CCoinsViewCache::Flush. This allows the receiver
257 : : * of CCoinsView::BatchWrite to iterate through the flagged entries without knowing
258 : : * the caller's intent.
259 : : *
260 : : * However, the receiver can still call CoinsViewCacheCursor::WillErase to see if the
261 : : * caller will erase the entry after BatchWrite returns. If so, the receiver can
262 : : * perform optimizations such as moving the coin out of the CCoinsCachEntry instead
263 : : * of copying it.
264 : : */
265 : : struct CoinsViewCacheCursor
266 : : {
267 : : //! If will_erase is not set, iterating through the cursor will erase spent coins from the map,
268 : : //! and other coins will be unflagged (removing them from the linked list).
269 : : //! If will_erase is set, the underlying map and linked list will not be modified,
270 : : //! as the caller is expected to wipe the entire map anyway.
271 : : //! This is an optimization compared to erasing all entries as the cursor iterates them when will_erase is set.
272 : : //! Calling CCoinsMap::clear() afterwards is faster because a CoinsCachePair cannot be coerced back into a
273 : : //! CCoinsMap::iterator to be erased, and must therefore be looked up again by key in the CCoinsMap before being erased.
274 : 147703 : CoinsViewCacheCursor(size_t& usage LIFETIMEBOUND,
275 : : CoinsCachePair& sentinel LIFETIMEBOUND,
276 : : CCoinsMap& map LIFETIMEBOUND,
277 : : bool will_erase) noexcept
278 [ + - ]: 147703 : : m_usage(usage), m_sentinel(sentinel), m_map(map), m_will_erase(will_erase) {}
279 : :
280 : 147703 : inline CoinsCachePair* Begin() const noexcept { return m_sentinel.second.Next(); }
281 [ + + ]: 1233034 : inline CoinsCachePair* End() const noexcept { return &m_sentinel; }
282 : :
283 : : //! Return the next entry after current, possibly erasing current
284 : 1085331 : inline CoinsCachePair* NextAndMaybeErase(CoinsCachePair& current) noexcept
285 : : {
286 : 1085331 : const auto next_entry{current.second.Next()};
287 : : // If we are not going to erase the cache, we must still erase spent entries.
288 : : // Otherwise, clear the state of the entry.
289 [ + + ]: 1085331 : if (!m_will_erase) {
290 [ + + ]: 80096 : if (current.second.coin.IsSpent()) {
291 [ - + ]: 25035 : m_usage -= current.second.coin.DynamicMemoryUsage();
292 : 25035 : m_map.erase(current.first);
293 : : } else {
294 [ + - ]: 55061 : current.second.SetClean();
295 : : }
296 : : }
297 : 1085331 : return next_entry;
298 : : }
299 : :
300 [ + + + + : 490069 : inline bool WillErase(CoinsCachePair& current) const noexcept { return m_will_erase || current.second.coin.IsSpent(); }
+ + + + ]
301 : : private:
302 : : size_t& m_usage;
303 : : CoinsCachePair& m_sentinel;
304 : : CCoinsMap& m_map;
305 : : bool m_will_erase;
306 : : };
307 : :
308 : : /** Abstract view on the open txout dataset. */
309 [ + - + - : 607123 : class CCoinsView
+ - ]
310 : : {
311 : : public:
312 : : //! Retrieve the Coin (unspent transaction output) for a given outpoint.
313 : : virtual std::optional<Coin> GetCoin(const COutPoint& outpoint) const;
314 : :
315 : : //! Just check whether a given outpoint is unspent.
316 : : virtual bool HaveCoin(const COutPoint &outpoint) const;
317 : :
318 : : //! Retrieve the block hash whose state this CCoinsView currently represents
319 : : virtual uint256 GetBestBlock() const;
320 : :
321 : : //! Retrieve the range of blocks that may have been only partially written.
322 : : //! If the database is in a consistent state, the result is the empty vector.
323 : : //! Otherwise, a two-element vector is returned consisting of the new and
324 : : //! the old block hash, in that order.
325 : : virtual std::vector<uint256> GetHeadBlocks() const;
326 : :
327 : : //! Do a bulk modification (multiple Coin changes + BestBlock change).
328 : : //! The passed cursor is used to iterate through the coins.
329 : : virtual bool BatchWrite(CoinsViewCacheCursor& cursor, const uint256& hashBlock);
330 : :
331 : : //! Get a cursor to iterate over the whole state
332 : : virtual std::unique_ptr<CCoinsViewCursor> Cursor() const;
333 : :
334 : : //! As we use CCoinsViews polymorphically, have a virtual destructor
335 : 189 : virtual ~CCoinsView() = default;
336 : :
337 : : //! Estimate database size (0 if not implemented)
338 : 0 : virtual size_t EstimateSize() const { return 0; }
339 : : };
340 : :
341 : :
342 : : /** CCoinsView backed by another CCoinsView */
343 : 0 : class CCoinsViewBacked : public CCoinsView
344 : : {
345 : : protected:
346 : : CCoinsView *base;
347 : :
348 : : public:
349 : : CCoinsViewBacked(CCoinsView *viewIn);
350 : : std::optional<Coin> GetCoin(const COutPoint& outpoint) const override;
351 : : bool HaveCoin(const COutPoint &outpoint) const override;
352 : : uint256 GetBestBlock() const override;
353 : : std::vector<uint256> GetHeadBlocks() const override;
354 : : void SetBackend(CCoinsView &viewIn);
355 : : bool BatchWrite(CoinsViewCacheCursor& cursor, const uint256 &hashBlock) override;
356 : : std::unique_ptr<CCoinsViewCursor> Cursor() const override;
357 : : size_t EstimateSize() const override;
358 : : };
359 : :
360 : :
361 : : /** CCoinsView that adds a memory cache for transactions to another CCoinsView */
362 : : class CCoinsViewCache : public CCoinsViewBacked
363 : : {
364 : : private:
365 : : const bool m_deterministic;
366 : :
367 : : protected:
368 : : /**
369 : : * Make mutable so that we can "fill the cache" even from Get-methods
370 : : * declared as "const".
371 : : */
372 : : mutable uint256 hashBlock;
373 : : mutable CCoinsMapMemoryResource m_cache_coins_memory_resource{};
374 : : /* The starting sentinel of the flagged entry circular doubly linked list. */
375 : : mutable CoinsCachePair m_sentinel;
376 : : mutable CCoinsMap cacheCoins;
377 : :
378 : : /* Cached dynamic memory usage for the inner Coin objects. */
379 : : mutable size_t cachedCoinsUsage{0};
380 : :
381 : : public:
382 : : CCoinsViewCache(CCoinsView *baseIn, bool deterministic = false);
383 : :
384 : : /**
385 : : * By deleting the copy constructor, we prevent accidentally using it when one intends to create a cache on top of a base cache.
386 : : */
387 : : CCoinsViewCache(const CCoinsViewCache &) = delete;
388 : :
389 : : // Standard CCoinsView methods
390 : : std::optional<Coin> GetCoin(const COutPoint& outpoint) const override;
391 : : bool HaveCoin(const COutPoint &outpoint) const override;
392 : : uint256 GetBestBlock() const override;
393 : : void SetBestBlock(const uint256 &hashBlock);
394 : : bool BatchWrite(CoinsViewCacheCursor& cursor, const uint256 &hashBlock) override;
395 : 0 : std::unique_ptr<CCoinsViewCursor> Cursor() const override {
396 [ # # ]: 0 : throw std::logic_error("CCoinsViewCache cursor iteration not supported.");
397 : : }
398 : :
399 : : /**
400 : : * Check if we have the given utxo already loaded in this cache.
401 : : * The semantics are the same as HaveCoin(), but no calls to
402 : : * the backing CCoinsView are made.
403 : : */
404 : : bool HaveCoinInCache(const COutPoint &outpoint) const;
405 : :
406 : : /**
407 : : * Return a reference to Coin in the cache, or coinEmpty if not found. This is
408 : : * more efficient than GetCoin.
409 : : *
410 : : * Generally, do not hold the reference returned for more than a short scope.
411 : : * While the current implementation allows for modifications to the contents
412 : : * of the cache while holding the reference, this behavior should not be relied
413 : : * on! To be safe, best to not hold the returned reference through any other
414 : : * calls to this cache.
415 : : */
416 : : const Coin& AccessCoin(const COutPoint &output) const;
417 : :
418 : : /**
419 : : * Add a coin. Set possible_overwrite to true if an unspent version may
420 : : * already exist in the cache.
421 : : */
422 : : void AddCoin(const COutPoint& outpoint, Coin&& coin, bool possible_overwrite);
423 : :
424 : : /**
425 : : * Emplace a coin into cacheCoins without performing any checks, marking
426 : : * the emplaced coin as dirty.
427 : : *
428 : : * NOT FOR GENERAL USE. Used only when loading coins from a UTXO snapshot.
429 : : * @sa ChainstateManager::PopulateAndValidateSnapshot()
430 : : */
431 : : void EmplaceCoinInternalDANGER(COutPoint&& outpoint, Coin&& coin);
432 : :
433 : : /**
434 : : * Spend a coin. Pass moveto in order to get the deleted data.
435 : : * If no unspent output exists for the passed outpoint, this call
436 : : * has no effect.
437 : : */
438 : : bool SpendCoin(const COutPoint &outpoint, Coin* moveto = nullptr);
439 : :
440 : : /**
441 : : * Push the modifications applied to this cache to its base and wipe local state.
442 : : * Failure to call this method or Sync() before destruction will cause the changes
443 : : * to be forgotten.
444 : : * If false is returned, the state of this cache (and its backing view) will be undefined.
445 : : */
446 : : bool Flush();
447 : :
448 : : /**
449 : : * Push the modifications applied to this cache to its base while retaining
450 : : * the contents of this cache (except for spent coins, which we erase).
451 : : * Failure to call this method or Flush() before destruction will cause the changes
452 : : * to be forgotten.
453 : : * If false is returned, the state of this cache (and its backing view) will be undefined.
454 : : */
455 : : bool Sync();
456 : :
457 : : /**
458 : : * Removes the UTXO with the given outpoint from the cache, if it is
459 : : * not modified.
460 : : */
461 : : void Uncache(const COutPoint &outpoint);
462 : :
463 : : //! Calculate the size of the cache (in number of transaction outputs)
464 : : unsigned int GetCacheSize() const;
465 : :
466 : : //! Calculate the size of the cache (in bytes)
467 : : size_t DynamicMemoryUsage() const;
468 : :
469 : : //! Check whether all prevouts of the transaction are present in the UTXO set represented by this view
470 : : bool HaveInputs(const CTransaction& tx) const;
471 : :
472 : : //! Force a reallocation of the cache map. This is required when downsizing
473 : : //! the cache because the map's allocator may be hanging onto a lot of
474 : : //! memory despite having called .clear().
475 : : //!
476 : : //! See: https://stackoverflow.com/questions/42114044/how-to-release-unordered-map-memory
477 : : void ReallocateCache();
478 : :
479 : : //! Run an internal sanity check on the cache data structure. */
480 : : void SanityCheck() const;
481 : :
482 : : private:
483 : : /**
484 : : * @note this is marked const, but may actually append to `cacheCoins`, increasing
485 : : * memory usage.
486 : : */
487 : : CCoinsMap::iterator FetchCoin(const COutPoint &outpoint) const;
488 : : };
489 : :
490 : : //! Utility function to add all of a transaction's outputs to a cache.
491 : : //! When check is false, this assumes that overwrites are only possible for coinbase transactions.
492 : : //! When check is true, the underlying view may be queried to determine whether an addition is
493 : : //! an overwrite.
494 : : // TODO: pass in a boolean to limit these possible overwrites to known
495 : : // (pre-BIP34) cases.
496 : : void AddCoins(CCoinsViewCache& cache, const CTransaction& tx, int nHeight, bool check = false);
497 : :
498 : : //! Utility function to find any unspent output with a given txid.
499 : : //! This function can be quite expensive because in the event of a transaction
500 : : //! which is not found in the cache, it can cause up to MAX_OUTPUTS_PER_BLOCK
501 : : //! lookups to database, so it should be used with care.
502 : : const Coin& AccessByTxid(const CCoinsViewCache& cache, const Txid& txid);
503 : :
504 : : /**
505 : : * This is a minimally invasive approach to shutdown on LevelDB read errors from the
506 : : * chainstate, while keeping user interface out of the common library, which is shared
507 : : * between bitcoind, and bitcoin-qt and non-server tools.
508 : : *
509 : : * Writes do not need similar protection, as failure to write is handled by the caller.
510 : : */
511 : : class CCoinsViewErrorCatcher final : public CCoinsViewBacked
512 : : {
513 : : public:
514 [ + - ]: 1240 : explicit CCoinsViewErrorCatcher(CCoinsView* view) : CCoinsViewBacked(view) {}
515 : :
516 : 1020 : void AddReadErrCallback(std::function<void()> f) {
517 [ + - ]: 1020 : m_err_callbacks.emplace_back(std::move(f));
518 : 1020 : }
519 : :
520 : : std::optional<Coin> GetCoin(const COutPoint& outpoint) const override;
521 : : bool HaveCoin(const COutPoint &outpoint) const override;
522 : :
523 : : private:
524 : : /** A list of callbacks to execute upon leveldb read error. */
525 : : std::vector<std::function<void()>> m_err_callbacks;
526 : :
527 : : };
528 : :
529 : : #endif // BITCOIN_COINS_H
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