aboutsummaryrefslogtreecommitdiff
path: root/src/coins.h
blob: 077545a55bd61d78027ffacdc03467d885b0e765 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2016 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_COINS_H
#define BITCOIN_COINS_H

#include "primitives/transaction.h"
#include "compressor.h"
#include "core_memusage.h"
#include "hash.h"
#include "memusage.h"
#include "serialize.h"
#include "uint256.h"

#include <assert.h>
#include <stdint.h>

#include <unordered_map>

/**
 * A UTXO entry.
 *
 * Serialized format:
 * - VARINT((coinbase ? 1 : 0) | (height << 1))
 * - the non-spent CTxOut (via CTxOutCompressor)
 */
class Coin
{
public:
    //! unspent transaction output
    CTxOut out;

    //! whether containing transaction was a coinbase
    unsigned int fCoinBase : 1;

    //! at which height this containing transaction was included in the active block chain
    uint32_t nHeight : 31;

    //! construct a Coin from a CTxOut and height/coinbase information.
    Coin(CTxOut&& outIn, int nHeightIn, bool fCoinBaseIn) : out(std::move(outIn)), fCoinBase(fCoinBaseIn), nHeight(nHeightIn) {}
    Coin(const CTxOut& outIn, int nHeightIn, bool fCoinBaseIn) : out(outIn), fCoinBase(fCoinBaseIn),nHeight(nHeightIn) {}

    void Clear() {
        out.SetNull();
        fCoinBase = false;
        nHeight = 0;
    }

    //! empty constructor
    Coin() : fCoinBase(false), nHeight(0) { }

    bool IsCoinBase() const {
        return fCoinBase;
    }

    template<typename Stream>
    void Serialize(Stream &s) const {
        assert(!IsSpent());
        uint32_t code = nHeight * 2 + fCoinBase;
        ::Serialize(s, VARINT(code));
        ::Serialize(s, CTxOutCompressor(REF(out)));
    }

    template<typename Stream>
    void Unserialize(Stream &s) {
        uint32_t code = 0;
        ::Unserialize(s, VARINT(code));
        nHeight = code >> 1;
        fCoinBase = code & 1;
        ::Unserialize(s, REF(CTxOutCompressor(out)));
    }

    bool IsSpent() const {
        return out.IsNull();
    }

    size_t DynamicMemoryUsage() const {
        return memusage::DynamicUsage(out.scriptPubKey);
    }
};

class SaltedOutpointHasher
{
private:
    /** Salt */
    const uint64_t k0, k1;

public:
    SaltedOutpointHasher();

    /**
     * This *must* return size_t. With Boost 1.46 on 32-bit systems the
     * unordered_map will behave unpredictably if the custom hasher returns a
     * uint64_t, resulting in failures when syncing the chain (#4634).
     */
    size_t operator()(const COutPoint& id) const {
        return SipHashUint256Extra(k0, k1, id.hash, id.n);
    }
};

struct CCoinsCacheEntry
{
    Coin coin; // The actual cached data.
    unsigned char flags;

    enum Flags {
        DIRTY = (1 << 0), // This cache entry is potentially different from the version in the parent view.
        FRESH = (1 << 1), // The parent view does not have this entry (or it is pruned).
        /* Note that FRESH is a performance optimization with which we can
         * erase coins that are fully spent if we know we do not need to
         * flush the changes to the parent cache.  It is always safe to
         * not mark FRESH if that condition is not guaranteed.
         */
    };

    CCoinsCacheEntry() : flags(0) {}
    explicit CCoinsCacheEntry(Coin&& coin_) : coin(std::move(coin_)), flags(0) {}
};

typedef std::unordered_map<COutPoint, CCoinsCacheEntry, SaltedOutpointHasher> CCoinsMap;

/** Cursor for iterating over CoinsView state */
class CCoinsViewCursor
{
public:
    CCoinsViewCursor(const uint256 &hashBlockIn): hashBlock(hashBlockIn) {}
    virtual ~CCoinsViewCursor() {}

    virtual bool GetKey(COutPoint &key) const = 0;
    virtual bool GetValue(Coin &coin) const = 0;
    virtual unsigned int GetValueSize() const = 0;

    virtual bool Valid() const = 0;
    virtual void Next() = 0;

    //! Get best block at the time this cursor was created
    const uint256 &GetBestBlock() const { return hashBlock; }
private:
    uint256 hashBlock;
};

/** Abstract view on the open txout dataset. */
class CCoinsView
{
public:
    /** Retrieve the Coin (unspent transaction output) for a given outpoint.
     *  Returns true only when an unspent coin was found, which is returned in coin.
     *  When false is returned, coin's value is unspecified.
     */
    virtual bool GetCoin(const COutPoint &outpoint, Coin &coin) const;

    //! Just check whether a given outpoint is unspent.
    virtual bool HaveCoin(const COutPoint &outpoint) const;

    //! Retrieve the block hash whose state this CCoinsView currently represents
    virtual uint256 GetBestBlock() const;

    //! Do a bulk modification (multiple Coin changes + BestBlock change).
    //! The passed mapCoins can be modified.
    virtual bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);

    //! Get a cursor to iterate over the whole state
    virtual CCoinsViewCursor *Cursor() const;

    //! As we use CCoinsViews polymorphically, have a virtual destructor
    virtual ~CCoinsView() {}

    //! Estimate database size (0 if not implemented)
    virtual size_t EstimateSize() const { return 0; }
};


/** CCoinsView backed by another CCoinsView */
class CCoinsViewBacked : public CCoinsView
{
protected:
    CCoinsView *base;

public:
    CCoinsViewBacked(CCoinsView *viewIn);
    bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
    bool HaveCoin(const COutPoint &outpoint) const override;
    uint256 GetBestBlock() const override;
    void SetBackend(CCoinsView &viewIn);
    bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
    CCoinsViewCursor *Cursor() const override;
    size_t EstimateSize() const override;
};


/** CCoinsView that adds a memory cache for transactions to another CCoinsView */
class CCoinsViewCache : public CCoinsViewBacked
{
protected:
    /**
     * Make mutable so that we can "fill the cache" even from Get-methods
     * declared as "const".  
     */
    mutable uint256 hashBlock;
    mutable CCoinsMap cacheCoins;

    /* Cached dynamic memory usage for the inner Coin objects. */
    mutable size_t cachedCoinsUsage;

public:
    CCoinsViewCache(CCoinsView *baseIn);

    // Standard CCoinsView methods
    bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
    bool HaveCoin(const COutPoint &outpoint) const override;
    uint256 GetBestBlock() const override;
    void SetBestBlock(const uint256 &hashBlock);
    bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
    CCoinsViewCursor* Cursor() const override {
        throw std::logic_error("CCoinsViewCache cursor iteration not supported.");
    }

    /**
     * Check if we have the given utxo already loaded in this cache.
     * The semantics are the same as HaveCoin(), but no calls to
     * the backing CCoinsView are made.
     */
    bool HaveCoinInCache(const COutPoint &outpoint) const;

    /**
     * Return a reference to Coin in the cache, or a pruned one if not found. This is
     * more efficient than GetCoin.
     *
     * Generally, do not hold the reference returned for more than a short scope.
     * While the current implementation allows for modifications to the contents
     * of the cache while holding the reference, this behavior should not be relied
     * on! To be safe, best to not hold the returned reference through any other
     * calls to this cache.
     */
    const Coin& AccessCoin(const COutPoint &output) const;

    /**
     * Add a coin. Set potential_overwrite to true if a non-pruned version may
     * already exist.
     */
    void AddCoin(const COutPoint& outpoint, Coin&& coin, bool potential_overwrite);

    /**
     * Spend a coin. Pass moveto in order to get the deleted data.
     * If no unspent output exists for the passed outpoint, this call
     * has no effect.
     */
    bool SpendCoin(const COutPoint &outpoint, Coin* moveto = nullptr);

    /**
     * Push the modifications applied to this cache to its base.
     * Failure to call this method before destruction will cause the changes to be forgotten.
     * If false is returned, the state of this cache (and its backing view) will be undefined.
     */
    bool Flush();

    /**
     * Removes the UTXO with the given outpoint from the cache, if it is
     * not modified.
     */
    void Uncache(const COutPoint &outpoint);

    //! Calculate the size of the cache (in number of transaction outputs)
    unsigned int GetCacheSize() const;

    //! Calculate the size of the cache (in bytes)
    size_t DynamicMemoryUsage() const;

    /** 
     * Amount of bitcoins coming in to a transaction
     * Note that lightweight clients may not know anything besides the hash of previous transactions,
     * so may not be able to calculate this.
     *
     * @param[in] tx	transaction for which we are checking input total
     * @return	Sum of value of all inputs (scriptSigs)
     */
    CAmount GetValueIn(const CTransaction& tx) const;

    //! Check whether all prevouts of the transaction are present in the UTXO set represented by this view
    bool HaveInputs(const CTransaction& tx) const;

private:
    CCoinsMap::iterator FetchCoin(const COutPoint &outpoint) const;

    /**
     * By making the copy constructor private, we prevent accidentally using it when one intends to create a cache on top of a base cache.
     */
    CCoinsViewCache(const CCoinsViewCache &);
};

//! Utility function to add all of a transaction's outputs to a cache.
// It assumes that overwrites are only possible for coinbase transactions,
// TODO: pass in a boolean to limit these possible overwrites to known
// (pre-BIP34) cases.
void AddCoins(CCoinsViewCache& cache, const CTransaction& tx, int nHeight);

//! Utility function to find any unspent output with a given txid.
const Coin& AccessByTxid(const CCoinsViewCache& cache, const uint256& txid);

#endif // BITCOIN_COINS_H