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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_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/hasher.h>
17 : :
18 : : #include <assert.h>
19 : : #include <stdint.h>
20 : :
21 : : #include <functional>
22 : : #include <unordered_map>
23 : :
24 : : /**
25 : : * A UTXO entry.
26 : : *
27 : : * Serialized format:
28 : : * - VARINT((coinbase ? 1 : 0) | (height << 1))
29 : : * - the non-spent CTxOut (via TxOutCompression)
30 : : */
31 : 0 : class Coin
32 : : {
33 : : public:
34 : : //! unspent transaction output
35 : : CTxOut out;
36 : :
37 : : //! whether containing transaction was a coinbase
38 : : unsigned int fCoinBase : 1;
39 : :
40 : : //! at which height this containing transaction was included in the active block chain
41 : : uint32_t nHeight : 31;
42 : :
43 : : //! construct a Coin from a CTxOut and height/coinbase information.
44 : : Coin(CTxOut&& outIn, int nHeightIn, bool fCoinBaseIn) : out(std::move(outIn)), fCoinBase(fCoinBaseIn), nHeight(nHeightIn) {}
45 : 0 : Coin(const CTxOut& outIn, int nHeightIn, bool fCoinBaseIn) : out(outIn), fCoinBase(fCoinBaseIn),nHeight(nHeightIn) {}
46 : :
47 : 0 : void Clear() {
48 : 0 : out.SetNull();
49 : 0 : fCoinBase = false;
50 : 0 : nHeight = 0;
51 : 0 : }
52 : :
53 : : //! empty constructor
54 : 4 : Coin() : fCoinBase(false), nHeight(0) { }
55 : :
56 : 0 : bool IsCoinBase() const {
57 : 0 : return fCoinBase;
58 : : }
59 : :
60 : : template<typename Stream>
61 : 0 : void Serialize(Stream &s) const {
62 [ # # ]: 0 : assert(!IsSpent());
63 : 0 : uint32_t code = nHeight * uint32_t{2} + fCoinBase;
64 : 0 : ::Serialize(s, VARINT(code));
65 : 0 : ::Serialize(s, Using<TxOutCompression>(out));
66 : 0 : }
67 : :
68 : : template<typename Stream>
69 : 0 : void Unserialize(Stream &s) {
70 : 0 : uint32_t code = 0;
71 : 0 : ::Unserialize(s, VARINT(code));
72 : 0 : nHeight = code >> 1;
73 : 0 : fCoinBase = code & 1;
74 : 0 : ::Unserialize(s, Using<TxOutCompression>(out));
75 : 0 : }
76 : :
77 : : /** Either this coin never existed (see e.g. coinEmpty in coins.cpp), or it
78 : : * did exist and has been spent.
79 : : */
80 : 0 : bool IsSpent() const {
81 : 0 : return out.IsNull();
82 : : }
83 : :
84 : 0 : size_t DynamicMemoryUsage() const {
85 : 0 : return memusage::DynamicUsage(out.scriptPubKey);
86 : : }
87 : : };
88 : :
89 : : /**
90 : : * A Coin in one level of the coins database caching hierarchy.
91 : : *
92 : : * A coin can either be:
93 : : * - unspent or spent (in which case the Coin object will be nulled out - see Coin.Clear())
94 : : * - DIRTY or not DIRTY
95 : : * - FRESH or not FRESH
96 : : *
97 : : * Out of these 2^3 = 8 states, only some combinations are valid:
98 : : * - unspent, FRESH, DIRTY (e.g. a new coin created in the cache)
99 : : * - unspent, not FRESH, DIRTY (e.g. a coin changed in the cache during a reorg)
100 : : * - unspent, not FRESH, not DIRTY (e.g. an unspent coin fetched from the parent cache)
101 : : * - spent, FRESH, not DIRTY (e.g. a spent coin fetched from the parent cache)
102 : : * - spent, not FRESH, DIRTY (e.g. a coin is spent and spentness needs to be flushed to the parent)
103 : : */
104 : 0 : struct CCoinsCacheEntry
105 : : {
106 : : Coin coin; // The actual cached data.
107 : : unsigned char flags;
108 : :
109 : : enum Flags {
110 : : /**
111 : : * DIRTY means the CCoinsCacheEntry is potentially different from the
112 : : * version in the parent cache. Failure to mark a coin as DIRTY when
113 : : * it is potentially different from the parent cache will cause a
114 : : * consensus failure, since the coin's state won't get written to the
115 : : * parent when the cache is flushed.
116 : : */
117 : : DIRTY = (1 << 0),
118 : : /**
119 : : * FRESH means the parent cache does not have this coin or that it is a
120 : : * spent coin in the parent cache. If a FRESH coin in the cache is
121 : : * later spent, it can be deleted entirely and doesn't ever need to be
122 : : * flushed to the parent. This is a performance optimization. Marking a
123 : : * coin as FRESH when it exists unspent in the parent cache will cause a
124 : : * consensus failure, since it might not be deleted from the parent
125 : : * when this cache is flushed.
126 : : */
127 : : FRESH = (1 << 1),
128 : : };
129 : :
130 : 0 : CCoinsCacheEntry() : flags(0) {}
131 : 0 : explicit CCoinsCacheEntry(Coin&& coin_) : coin(std::move(coin_)), flags(0) {}
132 : 0 : CCoinsCacheEntry(Coin&& coin_, unsigned char flag) : coin(std::move(coin_)), flags(flag) {}
133 : : };
134 : :
135 : : /**
136 : : * PoolAllocator's MAX_BLOCK_SIZE_BYTES parameter here uses sizeof the data, and adds the size
137 : : * of 4 pointers. We do not know the exact node size used in the std::unordered_node implementation
138 : : * because it is implementation defined. Most implementations have an overhead of 1 or 2 pointers,
139 : : * so nodes can be connected in a linked list, and in some cases the hash value is stored as well.
140 : : * Using an additional sizeof(void*)*4 for MAX_BLOCK_SIZE_BYTES should thus be sufficient so that
141 : : * all implementations can allocate the nodes from the PoolAllocator.
142 : : */
143 : : using CCoinsMap = std::unordered_map<COutPoint,
144 : : CCoinsCacheEntry,
145 : : SaltedOutpointHasher,
146 : : std::equal_to<COutPoint>,
147 : : PoolAllocator<std::pair<const COutPoint, CCoinsCacheEntry>,
148 : : sizeof(std::pair<const COutPoint, CCoinsCacheEntry>) + sizeof(void*) * 4>>;
149 : :
150 : : using CCoinsMapMemoryResource = CCoinsMap::allocator_type::ResourceType;
151 : :
152 : : /** Cursor for iterating over CoinsView state */
153 : : class CCoinsViewCursor
154 : : {
155 : : public:
156 : 0 : CCoinsViewCursor(const uint256 &hashBlockIn): hashBlock(hashBlockIn) {}
157 : 0 : virtual ~CCoinsViewCursor() {}
158 : :
159 : : virtual bool GetKey(COutPoint &key) const = 0;
160 : : virtual bool GetValue(Coin &coin) const = 0;
161 : :
162 : : virtual bool Valid() const = 0;
163 : : virtual void Next() = 0;
164 : :
165 : : //! Get best block at the time this cursor was created
166 : : const uint256 &GetBestBlock() const { return hashBlock; }
167 : : private:
168 : : uint256 hashBlock;
169 : : };
170 : :
171 : : /** Abstract view on the open txout dataset. */
172 : 0 : class CCoinsView
173 : : {
174 : : public:
175 : : /** Retrieve the Coin (unspent transaction output) for a given outpoint.
176 : : * Returns true only when an unspent coin was found, which is returned in coin.
177 : : * When false is returned, coin's value is unspecified.
178 : : */
179 : : virtual bool GetCoin(const COutPoint &outpoint, Coin &coin) const;
180 : :
181 : : //! Just check whether a given outpoint is unspent.
182 : : virtual bool HaveCoin(const COutPoint &outpoint) const;
183 : :
184 : : //! Retrieve the block hash whose state this CCoinsView currently represents
185 : : virtual uint256 GetBestBlock() const;
186 : :
187 : : //! Retrieve the range of blocks that may have been only partially written.
188 : : //! If the database is in a consistent state, the result is the empty vector.
189 : : //! Otherwise, a two-element vector is returned consisting of the new and
190 : : //! the old block hash, in that order.
191 : : virtual std::vector<uint256> GetHeadBlocks() const;
192 : :
193 : : //! Do a bulk modification (multiple Coin changes + BestBlock change).
194 : : //! The passed mapCoins can be modified.
195 : : virtual bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock, bool erase = true);
196 : :
197 : : //! Get a cursor to iterate over the whole state
198 : : virtual std::unique_ptr<CCoinsViewCursor> Cursor() const;
199 : :
200 : : //! As we use CCoinsViews polymorphically, have a virtual destructor
201 : 0 : virtual ~CCoinsView() {}
202 : :
203 : : //! Estimate database size (0 if not implemented)
204 : 0 : virtual size_t EstimateSize() const { return 0; }
205 : : };
206 : :
207 : :
208 : : /** CCoinsView backed by another CCoinsView */
209 : 0 : class CCoinsViewBacked : public CCoinsView
210 : : {
211 : : protected:
212 : : CCoinsView *base;
213 : :
214 : : public:
215 : : CCoinsViewBacked(CCoinsView *viewIn);
216 : : bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
217 : : bool HaveCoin(const COutPoint &outpoint) const override;
218 : : uint256 GetBestBlock() const override;
219 : : std::vector<uint256> GetHeadBlocks() const override;
220 : : void SetBackend(CCoinsView &viewIn);
221 : : bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock, bool erase = true) override;
222 : : std::unique_ptr<CCoinsViewCursor> Cursor() const override;
223 : : size_t EstimateSize() const override;
224 : : };
225 : :
226 : :
227 : : /** CCoinsView that adds a memory cache for transactions to another CCoinsView */
228 : 0 : class CCoinsViewCache : public CCoinsViewBacked
229 : : {
230 : : private:
231 : : const bool m_deterministic;
232 : :
233 : : protected:
234 : : /**
235 : : * Make mutable so that we can "fill the cache" even from Get-methods
236 : : * declared as "const".
237 : : */
238 : : mutable uint256 hashBlock;
239 : : mutable CCoinsMapMemoryResource m_cache_coins_memory_resource{};
240 : : mutable CCoinsMap cacheCoins;
241 : :
242 : : /* Cached dynamic memory usage for the inner Coin objects. */
243 : : mutable size_t cachedCoinsUsage{0};
244 : :
245 : : public:
246 : : CCoinsViewCache(CCoinsView *baseIn, bool deterministic = false);
247 : :
248 : : /**
249 : : * By deleting the copy constructor, we prevent accidentally using it when one intends to create a cache on top of a base cache.
250 : : */
251 : : CCoinsViewCache(const CCoinsViewCache &) = delete;
252 : :
253 : : // Standard CCoinsView methods
254 : : bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
255 : : bool HaveCoin(const COutPoint &outpoint) const override;
256 : : uint256 GetBestBlock() const override;
257 : : void SetBestBlock(const uint256 &hashBlock);
258 : : bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock, bool erase = true) override;
259 : 0 : std::unique_ptr<CCoinsViewCursor> Cursor() const override {
260 [ # # ]: 0 : throw std::logic_error("CCoinsViewCache cursor iteration not supported.");
261 : 0 : }
262 : :
263 : : /**
264 : : * Check if we have the given utxo already loaded in this cache.
265 : : * The semantics are the same as HaveCoin(), but no calls to
266 : : * the backing CCoinsView are made.
267 : : */
268 : : bool HaveCoinInCache(const COutPoint &outpoint) const;
269 : :
270 : : /**
271 : : * Return a reference to Coin in the cache, or coinEmpty if not found. This is
272 : : * more efficient than GetCoin.
273 : : *
274 : : * Generally, do not hold the reference returned for more than a short scope.
275 : : * While the current implementation allows for modifications to the contents
276 : : * of the cache while holding the reference, this behavior should not be relied
277 : : * on! To be safe, best to not hold the returned reference through any other
278 : : * calls to this cache.
279 : : */
280 : : const Coin& AccessCoin(const COutPoint &output) const;
281 : :
282 : : /**
283 : : * Add a coin. Set possible_overwrite to true if an unspent version may
284 : : * already exist in the cache.
285 : : */
286 : : void AddCoin(const COutPoint& outpoint, Coin&& coin, bool possible_overwrite);
287 : :
288 : : /**
289 : : * Emplace a coin into cacheCoins without performing any checks, marking
290 : : * the emplaced coin as dirty.
291 : : *
292 : : * NOT FOR GENERAL USE. Used only when loading coins from a UTXO snapshot.
293 : : * @sa ChainstateManager::PopulateAndValidateSnapshot()
294 : : */
295 : : void EmplaceCoinInternalDANGER(COutPoint&& outpoint, Coin&& coin);
296 : :
297 : : /**
298 : : * Spend a coin. Pass moveto in order to get the deleted data.
299 : : * If no unspent output exists for the passed outpoint, this call
300 : : * has no effect.
301 : : */
302 : : bool SpendCoin(const COutPoint &outpoint, Coin* moveto = nullptr);
303 : :
304 : : /**
305 : : * Push the modifications applied to this cache to its base and wipe local state.
306 : : * Failure to call this method or Sync() before destruction will cause the changes
307 : : * to be forgotten.
308 : : * If false is returned, the state of this cache (and its backing view) will be undefined.
309 : : */
310 : : bool Flush();
311 : :
312 : : /**
313 : : * Push the modifications applied to this cache to its base while retaining
314 : : * the contents of this cache (except for spent coins, which we erase).
315 : : * Failure to call this method or Flush() before destruction will cause the changes
316 : : * to be forgotten.
317 : : * If false is returned, the state of this cache (and its backing view) will be undefined.
318 : : */
319 : : bool Sync();
320 : :
321 : : /**
322 : : * Removes the UTXO with the given outpoint from the cache, if it is
323 : : * not modified.
324 : : */
325 : : void Uncache(const COutPoint &outpoint);
326 : :
327 : : //! Calculate the size of the cache (in number of transaction outputs)
328 : : unsigned int GetCacheSize() const;
329 : :
330 : : //! Calculate the size of the cache (in bytes)
331 : : size_t DynamicMemoryUsage() const;
332 : :
333 : : //! Check whether all prevouts of the transaction are present in the UTXO set represented by this view
334 : : bool HaveInputs(const CTransaction& tx) const;
335 : :
336 : : //! Force a reallocation of the cache map. This is required when downsizing
337 : : //! the cache because the map's allocator may be hanging onto a lot of
338 : : //! memory despite having called .clear().
339 : : //!
340 : : //! See: https://stackoverflow.com/questions/42114044/how-to-release-unordered-map-memory
341 : : void ReallocateCache();
342 : :
343 : : //! Run an internal sanity check on the cache data structure. */
344 : : void SanityCheck() const;
345 : :
346 : : private:
347 : : /**
348 : : * @note this is marked const, but may actually append to `cacheCoins`, increasing
349 : : * memory usage.
350 : : */
351 : : CCoinsMap::iterator FetchCoin(const COutPoint &outpoint) const;
352 : : };
353 : :
354 : : //! Utility function to add all of a transaction's outputs to a cache.
355 : : //! When check is false, this assumes that overwrites are only possible for coinbase transactions.
356 : : //! When check is true, the underlying view may be queried to determine whether an addition is
357 : : //! an overwrite.
358 : : // TODO: pass in a boolean to limit these possible overwrites to known
359 : : // (pre-BIP34) cases.
360 : : void AddCoins(CCoinsViewCache& cache, const CTransaction& tx, int nHeight, bool check = false);
361 : :
362 : : //! Utility function to find any unspent output with a given txid.
363 : : //! This function can be quite expensive because in the event of a transaction
364 : : //! which is not found in the cache, it can cause up to MAX_OUTPUTS_PER_BLOCK
365 : : //! lookups to database, so it should be used with care.
366 : : const Coin& AccessByTxid(const CCoinsViewCache& cache, const Txid& txid);
367 : :
368 : : /**
369 : : * This is a minimally invasive approach to shutdown on LevelDB read errors from the
370 : : * chainstate, while keeping user interface out of the common library, which is shared
371 : : * between bitcoind, and bitcoin-qt and non-server tools.
372 : : *
373 : : * Writes do not need similar protection, as failure to write is handled by the caller.
374 : : */
375 : 0 : class CCoinsViewErrorCatcher final : public CCoinsViewBacked
376 : : {
377 : : public:
378 : 0 : explicit CCoinsViewErrorCatcher(CCoinsView* view) : CCoinsViewBacked(view) {}
379 : :
380 : 0 : void AddReadErrCallback(std::function<void()> f) {
381 : 0 : m_err_callbacks.emplace_back(std::move(f));
382 : 0 : }
383 : :
384 : : bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
385 : : bool HaveCoin(const COutPoint &outpoint) const override;
386 : :
387 : : private:
388 : : /** A list of callbacks to execute upon leveldb read error. */
389 : : std::vector<std::function<void()>> m_err_callbacks;
390 : :
391 : : };
392 : :
393 : : #endif // BITCOIN_COINS_H
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