Line data Source code
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 : 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 89676 : Coin(const CTxOut& outIn, int nHeightIn, bool fCoinBaseIn) : out(outIn), fCoinBase(fCoinBaseIn),nHeight(nHeightIn) {}
46 :
47 4665 : void Clear() {
48 4665 : out.SetNull();
49 4665 : fCoinBase = false;
50 4665 : nHeight = 0;
51 4665 : }
52 :
53 : //! empty constructor
54 241538 : Coin() : fCoinBase(false), nHeight(0) { }
55 :
56 41948 : bool IsCoinBase() const {
57 41948 : 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 551922 : bool IsSpent() const {
81 551922 : return out.IsNull();
82 : }
83 :
84 147995 : size_t DynamicMemoryUsage() const {
85 147995 : 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 : 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 44458 : CCoinsCacheEntry() : flags(0) {}
131 80225 : 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 : alignof(void*)>>;
150 :
151 : using CCoinsMapMemoryResource = CCoinsMap::allocator_type::ResourceType;
152 :
153 : /** Cursor for iterating over CoinsView state */
154 : class CCoinsViewCursor
155 : {
156 : public:
157 0 : CCoinsViewCursor(const uint256 &hashBlockIn): hashBlock(hashBlockIn) {}
158 0 : virtual ~CCoinsViewCursor() {}
159 :
160 : virtual bool GetKey(COutPoint &key) const = 0;
161 : virtual bool GetValue(Coin &coin) const = 0;
162 :
163 : virtual bool Valid() const = 0;
164 : virtual void Next() = 0;
165 :
166 : //! Get best block at the time this cursor was created
167 : const uint256 &GetBestBlock() const { return hashBlock; }
168 : private:
169 : uint256 hashBlock;
170 : };
171 :
172 : /** Abstract view on the open txout dataset. */
173 : class CCoinsView
174 : {
175 : public:
176 : /** Retrieve the Coin (unspent transaction output) for a given outpoint.
177 : * Returns true only when an unspent coin was found, which is returned in coin.
178 : * When false is returned, coin's value is unspecified.
179 : */
180 : virtual bool GetCoin(const COutPoint &outpoint, Coin &coin) const;
181 :
182 : //! Just check whether a given outpoint is unspent.
183 : virtual bool HaveCoin(const COutPoint &outpoint) const;
184 :
185 : //! Retrieve the block hash whose state this CCoinsView currently represents
186 : virtual uint256 GetBestBlock() const;
187 :
188 : //! Retrieve the range of blocks that may have been only partially written.
189 : //! If the database is in a consistent state, the result is the empty vector.
190 : //! Otherwise, a two-element vector is returned consisting of the new and
191 : //! the old block hash, in that order.
192 : virtual std::vector<uint256> GetHeadBlocks() const;
193 :
194 : //! Do a bulk modification (multiple Coin changes + BestBlock change).
195 : //! The passed mapCoins can be modified.
196 : virtual bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock, bool erase = true);
197 :
198 : //! Get a cursor to iterate over the whole state
199 : virtual std::unique_ptr<CCoinsViewCursor> Cursor() const;
200 :
201 : //! As we use CCoinsViews polymorphically, have a virtual destructor
202 57924 : virtual ~CCoinsView() {}
203 :
204 : //! Estimate database size (0 if not implemented)
205 0 : virtual size_t EstimateSize() const { return 0; }
206 : };
207 :
208 :
209 : /** CCoinsView backed by another CCoinsView */
210 : class CCoinsViewBacked : public CCoinsView
211 : {
212 : protected:
213 : CCoinsView *base;
214 :
215 : public:
216 : CCoinsViewBacked(CCoinsView *viewIn);
217 : bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
218 : bool HaveCoin(const COutPoint &outpoint) const override;
219 : uint256 GetBestBlock() const override;
220 : std::vector<uint256> GetHeadBlocks() const override;
221 : void SetBackend(CCoinsView &viewIn);
222 : bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock, bool erase = true) override;
223 : std::unique_ptr<CCoinsViewCursor> Cursor() const override;
224 : size_t EstimateSize() const override;
225 : };
226 :
227 :
228 : /** CCoinsView that adds a memory cache for transactions to another CCoinsView */
229 : class CCoinsViewCache : public CCoinsViewBacked
230 : {
231 : private:
232 : const bool m_deterministic;
233 :
234 : protected:
235 : /**
236 : * Make mutable so that we can "fill the cache" even from Get-methods
237 : * declared as "const".
238 : */
239 : mutable uint256 hashBlock;
240 : mutable CCoinsMapMemoryResource m_cache_coins_memory_resource{};
241 : mutable CCoinsMap cacheCoins;
242 :
243 : /* Cached dynamic memory usage for the inner Coin objects. */
244 : mutable size_t cachedCoinsUsage{0};
245 :
246 : public:
247 : CCoinsViewCache(CCoinsView *baseIn, bool deterministic = false);
248 :
249 : /**
250 : * By deleting the copy constructor, we prevent accidentally using it when one intends to create a cache on top of a base cache.
251 : */
252 : CCoinsViewCache(const CCoinsViewCache &) = delete;
253 :
254 : // Standard CCoinsView methods
255 : bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
256 : bool HaveCoin(const COutPoint &outpoint) const override;
257 : uint256 GetBestBlock() const override;
258 : void SetBestBlock(const uint256 &hashBlock);
259 : bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock, bool erase = true) override;
260 0 : std::unique_ptr<CCoinsViewCursor> Cursor() const override {
261 0 : throw std::logic_error("CCoinsViewCache cursor iteration not supported.");
262 0 : }
263 :
264 : /**
265 : * Check if we have the given utxo already loaded in this cache.
266 : * The semantics are the same as HaveCoin(), but no calls to
267 : * the backing CCoinsView are made.
268 : */
269 : bool HaveCoinInCache(const COutPoint &outpoint) const;
270 :
271 : /**
272 : * Return a reference to Coin in the cache, or coinEmpty if not found. This is
273 : * more efficient than GetCoin.
274 : *
275 : * Generally, do not hold the reference returned for more than a short scope.
276 : * While the current implementation allows for modifications to the contents
277 : * of the cache while holding the reference, this behavior should not be relied
278 : * on! To be safe, best to not hold the returned reference through any other
279 : * calls to this cache.
280 : */
281 : const Coin& AccessCoin(const COutPoint &output) const;
282 :
283 : /**
284 : * Add a coin. Set possible_overwrite to true if an unspent version may
285 : * already exist in the cache.
286 : */
287 : void AddCoin(const COutPoint& outpoint, Coin&& coin, bool possible_overwrite);
288 :
289 : /**
290 : * Emplace a coin into cacheCoins without performing any checks, marking
291 : * the emplaced coin as dirty.
292 : *
293 : * NOT FOR GENERAL USE. Used only when loading coins from a UTXO snapshot.
294 : * @sa ChainstateManager::PopulateAndValidateSnapshot()
295 : */
296 : void EmplaceCoinInternalDANGER(COutPoint&& outpoint, Coin&& coin);
297 :
298 : /**
299 : * Spend a coin. Pass moveto in order to get the deleted data.
300 : * If no unspent output exists for the passed outpoint, this call
301 : * has no effect.
302 : */
303 : bool SpendCoin(const COutPoint &outpoint, Coin* moveto = nullptr);
304 :
305 : /**
306 : * Push the modifications applied to this cache to its base and wipe local state.
307 : * Failure to call this method or Sync() before destruction will cause the changes
308 : * to be forgotten.
309 : * If false is returned, the state of this cache (and its backing view) will be undefined.
310 : */
311 : bool Flush();
312 :
313 : /**
314 : * Push the modifications applied to this cache to its base while retaining
315 : * the contents of this cache (except for spent coins, which we erase).
316 : * Failure to call this method or Flush() before destruction will cause the changes
317 : * to be forgotten.
318 : * If false is returned, the state of this cache (and its backing view) will be undefined.
319 : */
320 : bool Sync();
321 :
322 : /**
323 : * Removes the UTXO with the given outpoint from the cache, if it is
324 : * not modified.
325 : */
326 : void Uncache(const COutPoint &outpoint);
327 :
328 : //! Calculate the size of the cache (in number of transaction outputs)
329 : unsigned int GetCacheSize() const;
330 :
331 : //! Calculate the size of the cache (in bytes)
332 : size_t DynamicMemoryUsage() const;
333 :
334 : //! Check whether all prevouts of the transaction are present in the UTXO set represented by this view
335 : bool HaveInputs(const CTransaction& tx) const;
336 :
337 : //! Force a reallocation of the cache map. This is required when downsizing
338 : //! the cache because the map's allocator may be hanging onto a lot of
339 : //! memory despite having called .clear().
340 : //!
341 : //! See: https://stackoverflow.com/questions/42114044/how-to-release-unordered-map-memory
342 : void ReallocateCache();
343 :
344 : //! Run an internal sanity check on the cache data structure. */
345 : void SanityCheck() const;
346 :
347 : private:
348 : /**
349 : * @note this is marked const, but may actually append to `cacheCoins`, increasing
350 : * memory usage.
351 : */
352 : CCoinsMap::iterator FetchCoin(const COutPoint &outpoint) const;
353 : };
354 :
355 : //! Utility function to add all of a transaction's outputs to a cache.
356 : //! When check is false, this assumes that overwrites are only possible for coinbase transactions.
357 : //! When check is true, the underlying view may be queried to determine whether an addition is
358 : //! an overwrite.
359 : // TODO: pass in a boolean to limit these possible overwrites to known
360 : // (pre-BIP34) cases.
361 : void AddCoins(CCoinsViewCache& cache, const CTransaction& tx, int nHeight, bool check = false);
362 :
363 : //! Utility function to find any unspent output with a given txid.
364 : //! This function can be quite expensive because in the event of a transaction
365 : //! which is not found in the cache, it can cause up to MAX_OUTPUTS_PER_BLOCK
366 : //! lookups to database, so it should be used with care.
367 : const Coin& AccessByTxid(const CCoinsViewCache& cache, const uint256& txid);
368 :
369 : /**
370 : * This is a minimally invasive approach to shutdown on LevelDB read errors from the
371 : * chainstate, while keeping user interface out of the common library, which is shared
372 : * between bitcoind, and bitcoin-qt and non-server tools.
373 : *
374 : * Writes do not need similar protection, as failure to write is handled by the caller.
375 : */
376 : class CCoinsViewErrorCatcher final : public CCoinsViewBacked
377 : {
378 : public:
379 1 : explicit CCoinsViewErrorCatcher(CCoinsView* view) : CCoinsViewBacked(view) {}
380 :
381 0 : void AddReadErrCallback(std::function<void()> f) {
382 0 : m_err_callbacks.emplace_back(std::move(f));
383 0 : }
384 :
385 : bool GetCoin(const COutPoint &outpoint, Coin &coin) 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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