Line data Source code
1 : // Copyright (c) 2009-2010 Satoshi Nakamoto
2 : // Copyright (c) 2009-2020 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 <crypto/siphash.h>
12 : #include <memusage.h>
13 : #include <primitives/transaction.h>
14 : #include <serialize.h>
15 : #include <uint256.h>
16 :
17 : #include <assert.h>
18 : #include <stdint.h>
19 :
20 : #include <functional>
21 : #include <unordered_map>
22 :
23 : /**
24 : * A UTXO entry.
25 : *
26 : * Serialized format:
27 : * - VARINT((coinbase ? 1 : 0) | (height << 1))
28 : * - the non-spent CTxOut (via TxOutCompression)
29 : */
30 192112691 : class Coin
31 : {
32 : public:
33 : //! unspent transaction output
34 : CTxOut out;
35 :
36 : //! whether containing transaction was a coinbase
37 : unsigned int fCoinBase : 1;
38 :
39 : //! at which height this containing transaction was included in the active block chain
40 : uint32_t nHeight : 31;
41 :
42 : //! construct a Coin from a CTxOut and height/coinbase information.
43 114 : Coin(CTxOut&& outIn, int nHeightIn, bool fCoinBaseIn) : out(std::move(outIn)), fCoinBase(fCoinBaseIn), nHeight(nHeightIn) {}
44 22194416 : Coin(const CTxOut& outIn, int nHeightIn, bool fCoinBaseIn) : out(outIn), fCoinBase(fCoinBaseIn),nHeight(nHeightIn) {}
45 :
46 6937810 : void Clear() {
47 6937810 : out.SetNull();
48 6937810 : fCoinBase = false;
49 6937810 : nHeight = 0;
50 6937810 : }
51 :
52 : //! empty constructor
53 111850718 : Coin() : fCoinBase(false), nHeight(0) { }
54 :
55 6905317 : bool IsCoinBase() const {
56 6905317 : return fCoinBase;
57 : }
58 :
59 : template<typename Stream>
60 139649 : void Serialize(Stream &s) const {
61 139649 : assert(!IsSpent());
62 139649 : uint32_t code = nHeight * uint32_t{2} + fCoinBase;
63 139649 : ::Serialize(s, VARINT(code));
64 139649 : ::Serialize(s, Using<TxOutCompression>(out));
65 139649 : }
66 :
67 : template<typename Stream>
68 96486 : void Unserialize(Stream &s) {
69 96486 : uint32_t code = 0;
70 96486 : ::Unserialize(s, VARINT(code));
71 96486 : nHeight = code >> 1;
72 96486 : fCoinBase = code & 1;
73 96486 : ::Unserialize(s, Using<TxOutCompression>(out));
74 96486 : }
75 :
76 74270532 : bool IsSpent() const {
77 74270532 : return out.IsNull();
78 : }
79 :
80 26394589 : size_t DynamicMemoryUsage() const {
81 26394589 : return memusage::DynamicUsage(out.scriptPubKey);
82 : }
83 : };
84 :
85 : class SaltedOutpointHasher
86 : {
87 : private:
88 : /** Salt */
89 : const uint64_t k0, k1;
90 :
91 : public:
92 : SaltedOutpointHasher();
93 :
94 : /**
95 : * This *must* return size_t. With Boost 1.46 on 32-bit systems the
96 : * unordered_map will behave unpredictably if the custom hasher returns a
97 : * uint64_t, resulting in failures when syncing the chain (#4634).
98 : *
99 : * Having the hash noexcept allows libstdc++'s unordered_map to recalculate
100 : * the hash during rehash, so it does not have to cache the value. This
101 : * reduces node's memory by sizeof(size_t). The required recalculation has
102 : * a slight performance penalty (around 1.6%), but this is compensated by
103 : * memory savings of about 9% which allow for a larger dbcache setting.
104 : *
105 : * @see https://gcc.gnu.org/onlinedocs/gcc-9.2.0/libstdc++/manual/manual/unordered_associative.html
106 : */
107 104860878 : size_t operator()(const COutPoint& id) const noexcept {
108 104860878 : return SipHashUint256Extra(k0, k1, id.hash, id.n);
109 : }
110 : };
111 :
112 : /**
113 : * A Coin in one level of the coins database caching hierarchy.
114 : *
115 : * A coin can either be:
116 : * - unspent or spent (in which case the Coin object will be nulled out - see Coin.Clear())
117 : * - DIRTY or not DIRTY
118 : * - FRESH or not FRESH
119 : *
120 : * Out of these 2^3 = 8 states, only some combinations are valid:
121 : * - unspent, FRESH, DIRTY (e.g. a new coin created in the cache)
122 : * - unspent, not FRESH, DIRTY (e.g. a coin changed in the cache during a reorg)
123 : * - unspent, not FRESH, not DIRTY (e.g. an unspent coin fetched from the parent cache)
124 : * - spent, FRESH, not DIRTY (e.g. a spent coin fetched from the parent cache)
125 : * - spent, not FRESH, DIRTY (e.g. a coin is spent and spentness needs to be flushed to the parent)
126 : */
127 37460712 : struct CCoinsCacheEntry
128 : {
129 : Coin coin; // The actual cached data.
130 : unsigned char flags;
131 :
132 : enum Flags {
133 : /**
134 : * DIRTY means the CCoinsCacheEntry is potentially different from the
135 : * version in the parent cache. Failure to mark a coin as DIRTY when
136 : * it is potentially different from the parent cache will cause a
137 : * consensus failure, since the coin's state won't get written to the
138 : * parent when the cache is flushed.
139 : */
140 : DIRTY = (1 << 0),
141 : /**
142 : * FRESH means the parent cache does not have this coin or that it is a
143 : * spent coin in the parent cache. If a FRESH coin in the cache is
144 : * later spent, it can be deleted entirely and doesn't ever need to be
145 : * flushed to the parent. This is a performance optimization. Marking a
146 : * coin as FRESH when it exists unspent in the parent cache will cause a
147 : * consensus failure, since it might not be deleted from the parent
148 : * when this cache is flushed.
149 : */
150 : FRESH = (1 << 1),
151 : };
152 :
153 21839330 : CCoinsCacheEntry() : flags(0) {}
154 15620102 : explicit CCoinsCacheEntry(Coin&& coin_) : coin(std::move(coin_)), flags(0) {}
155 : };
156 :
157 : typedef std::unordered_map<COutPoint, CCoinsCacheEntry, SaltedOutpointHasher> CCoinsMap;
158 :
159 : /** Cursor for iterating over CoinsView state */
160 : class CCoinsViewCursor
161 : {
162 : public:
163 44 : CCoinsViewCursor(const uint256 &hashBlockIn): hashBlock(hashBlockIn) {}
164 44 : virtual ~CCoinsViewCursor() {}
165 :
166 : virtual bool GetKey(COutPoint &key) const = 0;
167 : virtual bool GetValue(Coin &coin) const = 0;
168 : virtual unsigned int GetValueSize() const = 0;
169 :
170 : virtual bool Valid() const = 0;
171 : virtual void Next() = 0;
172 :
173 : //! Get best block at the time this cursor was created
174 7 : const uint256 &GetBestBlock() const { return hashBlock; }
175 : private:
176 : uint256 hashBlock;
177 : };
178 :
179 : /** Abstract view on the open txout dataset. */
180 506004 : class CCoinsView
181 : {
182 : public:
183 : /** Retrieve the Coin (unspent transaction output) for a given outpoint.
184 : * Returns true only when an unspent coin was found, which is returned in coin.
185 : * When false is returned, coin's value is unspecified.
186 : */
187 : virtual bool GetCoin(const COutPoint &outpoint, Coin &coin) const;
188 :
189 : //! Just check whether a given outpoint is unspent.
190 : virtual bool HaveCoin(const COutPoint &outpoint) const;
191 :
192 : //! Retrieve the block hash whose state this CCoinsView currently represents
193 : virtual uint256 GetBestBlock() const;
194 :
195 : //! Retrieve the range of blocks that may have been only partially written.
196 : //! If the database is in a consistent state, the result is the empty vector.
197 : //! Otherwise, a two-element vector is returned consisting of the new and
198 : //! the old block hash, in that order.
199 : virtual std::vector<uint256> GetHeadBlocks() const;
200 :
201 : //! Do a bulk modification (multiple Coin changes + BestBlock change).
202 : //! The passed mapCoins can be modified.
203 : virtual bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
204 :
205 : //! Get a cursor to iterate over the whole state
206 : virtual CCoinsViewCursor *Cursor() const;
207 :
208 : //! As we use CCoinsViews polymorphically, have a virtual destructor
209 506004 : virtual ~CCoinsView() {}
210 :
211 : //! Estimate database size (0 if not implemented)
212 0 : virtual size_t EstimateSize() const { return 0; }
213 : };
214 :
215 :
216 : /** CCoinsView backed by another CCoinsView */
217 458314 : class CCoinsViewBacked : public CCoinsView
218 : {
219 : protected:
220 : CCoinsView *base;
221 :
222 : public:
223 : CCoinsViewBacked(CCoinsView *viewIn);
224 : bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
225 : bool HaveCoin(const COutPoint &outpoint) const override;
226 : uint256 GetBestBlock() const override;
227 : std::vector<uint256> GetHeadBlocks() const override;
228 : void SetBackend(CCoinsView &viewIn);
229 : bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
230 : CCoinsViewCursor *Cursor() const override;
231 : size_t EstimateSize() const override;
232 : };
233 :
234 :
235 : /** CCoinsView that adds a memory cache for transactions to another CCoinsView */
236 815953 : class CCoinsViewCache : public CCoinsViewBacked
237 : {
238 : protected:
239 : /**
240 : * Make mutable so that we can "fill the cache" even from Get-methods
241 : * declared as "const".
242 : */
243 : mutable uint256 hashBlock;
244 : mutable CCoinsMap cacheCoins;
245 :
246 : /* Cached dynamic memory usage for the inner Coin objects. */
247 : mutable size_t cachedCoinsUsage;
248 :
249 : public:
250 : CCoinsViewCache(CCoinsView *baseIn);
251 :
252 : /**
253 : * By deleting the copy constructor, we prevent accidentally using it when one intends to create a cache on top of a base cache.
254 : */
255 : CCoinsViewCache(const CCoinsViewCache &) = delete;
256 :
257 : // Standard CCoinsView methods
258 : bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
259 : bool HaveCoin(const COutPoint &outpoint) const override;
260 : uint256 GetBestBlock() const override;
261 : void SetBestBlock(const uint256 &hashBlock);
262 : bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
263 0 : CCoinsViewCursor* Cursor() const override {
264 0 : throw std::logic_error("CCoinsViewCache cursor iteration not supported.");
265 0 : }
266 :
267 : /**
268 : * Check if we have the given utxo already loaded in this cache.
269 : * The semantics are the same as HaveCoin(), but no calls to
270 : * the backing CCoinsView are made.
271 : */
272 : bool HaveCoinInCache(const COutPoint &outpoint) const;
273 :
274 : /**
275 : * Return a reference to Coin in the cache, or coinEmpty if not found. This is
276 : * more efficient than GetCoin.
277 : *
278 : * Generally, do not hold the reference returned for more than a short scope.
279 : * While the current implementation allows for modifications to the contents
280 : * of the cache while holding the reference, this behavior should not be relied
281 : * on! To be safe, best to not hold the returned reference through any other
282 : * calls to this cache.
283 : */
284 : const Coin& AccessCoin(const COutPoint &output) const;
285 :
286 : /**
287 : * Add a coin. Set possible_overwrite to true if an unspent version may
288 : * already exist in the cache.
289 : */
290 : void AddCoin(const COutPoint& outpoint, Coin&& coin, bool possible_overwrite);
291 :
292 : /**
293 : * Spend a coin. Pass moveto in order to get the deleted data.
294 : * If no unspent output exists for the passed outpoint, this call
295 : * has no effect.
296 : */
297 : bool SpendCoin(const COutPoint &outpoint, Coin* moveto = nullptr);
298 :
299 : /**
300 : * Push the modifications applied to this cache to its base.
301 : * Failure to call this method before destruction will cause the changes to be forgotten.
302 : * If false is returned, the state of this cache (and its backing view) will be undefined.
303 : */
304 : bool Flush();
305 :
306 : /**
307 : * Removes the UTXO with the given outpoint from the cache, if it is
308 : * not modified.
309 : */
310 : void Uncache(const COutPoint &outpoint);
311 :
312 : //! Calculate the size of the cache (in number of transaction outputs)
313 : unsigned int GetCacheSize() const;
314 :
315 : //! Calculate the size of the cache (in bytes)
316 : size_t DynamicMemoryUsage() const;
317 :
318 : //! Check whether all prevouts of the transaction are present in the UTXO set represented by this view
319 : bool HaveInputs(const CTransaction& tx) const;
320 :
321 : //! Force a reallocation of the cache map. This is required when downsizing
322 : //! the cache because the map's allocator may be hanging onto a lot of
323 : //! memory despite having called .clear().
324 : //!
325 : //! See: https://stackoverflow.com/questions/42114044/how-to-release-unordered-map-memory
326 : void ReallocateCache();
327 :
328 : private:
329 : /**
330 : * @note this is marked const, but may actually append to `cacheCoins`, increasing
331 : * memory usage.
332 : */
333 : CCoinsMap::iterator FetchCoin(const COutPoint &outpoint) const;
334 : };
335 :
336 : //! Utility function to add all of a transaction's outputs to a cache.
337 : //! When check is false, this assumes that overwrites are only possible for coinbase transactions.
338 : //! When check is true, the underlying view may be queried to determine whether an addition is
339 : //! an overwrite.
340 : // TODO: pass in a boolean to limit these possible overwrites to known
341 : // (pre-BIP34) cases.
342 : void AddCoins(CCoinsViewCache& cache, const CTransaction& tx, int nHeight, bool check = false);
343 :
344 : //! Utility function to find any unspent output with a given txid.
345 : //! This function can be quite expensive because in the event of a transaction
346 : //! which is not found in the cache, it can cause up to MAX_OUTPUTS_PER_BLOCK
347 : //! lookups to database, so it should be used with care.
348 : const Coin& AccessByTxid(const CCoinsViewCache& cache, const uint256& txid);
349 :
350 : /**
351 : * This is a minimally invasive approach to shutdown on LevelDB read errors from the
352 : * chainstate, while keeping user interface out of the common library, which is shared
353 : * between bitcoind, and bitcoin-qt and non-server tools.
354 : *
355 : * Writes do not need similar protection, as failure to write is handled by the caller.
356 : */
357 1206 : class CCoinsViewErrorCatcher final : public CCoinsViewBacked
358 : {
359 : public:
360 1206 : explicit CCoinsViewErrorCatcher(CCoinsView* view) : CCoinsViewBacked(view) {}
361 :
362 498 : void AddReadErrCallback(std::function<void()> f) {
363 498 : m_err_callbacks.emplace_back(std::move(f));
364 498 : }
365 :
366 : bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
367 :
368 : private:
369 : /** A list of callbacks to execute upon leveldb read error. */
370 : std::vector<std::function<void()>> m_err_callbacks;
371 :
372 : };
373 :
374 : #endif // BITCOIN_COINS_H
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