Line data Source code
1 : // Copyright (c) 2009-2010 Satoshi Nakamoto
2 : // Copyright (c) 2009-2021 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.
44 114 : Coin(CTxOut&& outIn, int nHeightIn, bool fCoinBaseIn) : out(std::move(outIn)), fCoinBase(fCoinBaseIn), nHeight(nHeightIn) {}
45 290558 : Coin(const CTxOut& outIn, int nHeightIn, bool fCoinBaseIn) : out(outIn), fCoinBase(fCoinBaseIn),nHeight(nHeightIn) {}
46 :
47 128626 : void Clear() {
48 128626 : out.SetNull();
49 128626 : fCoinBase = false;
50 128626 : nHeight = 0;
51 128626 : }
52 :
53 : //! empty constructor
54 116948078 : Coin() : fCoinBase(false), nHeight(0) { }
55 :
56 2137 : bool IsCoinBase() const {
57 2137 : return fCoinBase;
58 : }
59 :
60 : template<typename Stream>
61 21407 : void Serialize(Stream &s) const {
62 21407 : assert(!IsSpent());
63 21407 : uint32_t code = nHeight * uint32_t{2} + fCoinBase;
64 21407 : ::Serialize(s, VARINT(code));
65 21407 : ::Serialize(s, Using<TxOutCompression>(out));
66 21407 : }
67 :
68 : template<typename Stream>
69 62293 : void Unserialize(Stream &s) {
70 62293 : uint32_t code = 0;
71 62293 : ::Unserialize(s, VARINT(code));
72 62293 : nHeight = code >> 1;
73 62293 : fCoinBase = code & 1;
74 62293 : ::Unserialize(s, Using<TxOutCompression>(out));
75 62293 : }
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 28023007 : bool IsSpent() const {
81 28023007 : return out.IsNull();
82 : }
83 :
84 1931061 : size_t DynamicMemoryUsage() const {
85 1931061 : 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 608096 : CCoinsCacheEntry() : flags(0) {}
131 1686448 : explicit CCoinsCacheEntry(Coin&& coin_) : coin(std::move(coin_)), flags(0) {}
132 1096 : 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 21 : CCoinsViewCursor(const uint256 &hashBlockIn): hashBlock(hashBlockIn) {}
157 21 : 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 : 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 156572 : 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 : 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 : 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 uint256& 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 : class CCoinsViewErrorCatcher final : public CCoinsViewBacked
376 : {
377 : public:
378 382 : 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 :
386 : private:
387 : /** A list of callbacks to execute upon leveldb read error. */
388 : std::vector<std::function<void()>> m_err_callbacks;
389 :
390 : };
391 :
392 : #endif // BITCOIN_COINS_H
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