Line data Source code
1 : // Copyright (c) 2012-2014 The Bitcoin Core developers
2 : // Distributed under the MIT software license, see the accompanying
3 : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
4 :
5 : #ifndef BITCOIN_BLOOM_H
6 : #define BITCOIN_BLOOM_H
7 :
8 : #include "serialize.h"
9 :
10 : #include <vector>
11 :
12 : class COutPoint;
13 : class CTransaction;
14 : class uint256;
15 :
16 : //! 20,000 items with fp rate < 0.1% or 10,000 items and <0.0001%
17 : static const unsigned int MAX_BLOOM_FILTER_SIZE = 36000; // bytes
18 : static const unsigned int MAX_HASH_FUNCS = 50;
19 :
20 : /**
21 : * First two bits of nFlags control how much IsRelevantAndUpdate actually updates
22 : * The remaining bits are reserved
23 : */
24 : enum bloomflags
25 : {
26 : BLOOM_UPDATE_NONE = 0,
27 : BLOOM_UPDATE_ALL = 1,
28 : // Only adds outpoints to the filter if the output is a pay-to-pubkey/pay-to-multisig script
29 : BLOOM_UPDATE_P2PUBKEY_ONLY = 2,
30 : BLOOM_UPDATE_MASK = 3,
31 : };
32 :
33 : /**
34 : * BloomFilter is a probabilistic filter which SPV clients provide
35 : * so that we can filter the transactions we send them.
36 : *
37 : * This allows for significantly more efficient transaction and block downloads.
38 : *
39 : * Because bloom filters are probabilistic, a SPV node can increase the false-
40 : * positive rate, making us send it transactions which aren't actually its,
41 : * allowing clients to trade more bandwidth for more privacy by obfuscating which
42 : * keys are controlled by them.
43 : */
44 2710 : class CBloomFilter
45 : {
46 : private:
47 : std::vector<unsigned char> vData;
48 : bool isFull;
49 : bool isEmpty;
50 : unsigned int nHashFuncs;
51 : unsigned int nTweak;
52 : unsigned char nFlags;
53 :
54 : unsigned int Hash(unsigned int nHashNum, const std::vector<unsigned char>& vDataToHash) const;
55 :
56 : // Private constructor for CRollingBloomFilter, no restrictions on size
57 : CBloomFilter(unsigned int nElements, double nFPRate, unsigned int nTweak);
58 : friend class CRollingBloomFilter;
59 :
60 : public:
61 : /**
62 : * Creates a new bloom filter which will provide the given fp rate when filled with the given number of elements
63 : * Note that if the given parameters will result in a filter outside the bounds of the protocol limits,
64 : * the filter created will be as close to the given parameters as possible within the protocol limits.
65 : * This will apply if nFPRate is very low or nElements is unreasonably high.
66 : * nTweak is a constant which is added to the seed value passed to the hash function
67 : * It should generally always be a random value (and is largely only exposed for unit testing)
68 : * nFlags should be one of the BLOOM_UPDATE_* enums (not _MASK)
69 : */
70 : CBloomFilter(unsigned int nElements, double nFPRate, unsigned int nTweak, unsigned char nFlagsIn);
71 726 : CBloomFilter() : isFull(true), isEmpty(false), nHashFuncs(0), nTweak(0), nFlags(0) {}
72 :
73 3 : ADD_SERIALIZE_METHODS;
74 :
75 : template <typename Stream, typename Operation>
76 3 : inline void SerializationOp(Stream& s, Operation ser_action, int nType, int nVersion) {
77 3 : READWRITE(vData);
78 3 : READWRITE(nHashFuncs);
79 3 : READWRITE(nTweak);
80 3 : READWRITE(nFlags);
81 3 : }
82 :
83 : void insert(const std::vector<unsigned char>& vKey);
84 : void insert(const COutPoint& outpoint);
85 : void insert(const uint256& hash);
86 :
87 : bool contains(const std::vector<unsigned char>& vKey) const;
88 : bool contains(const COutPoint& outpoint) const;
89 : bool contains(const uint256& hash) const;
90 :
91 : void clear();
92 : void reset(unsigned int nNewTweak);
93 :
94 : //! True if the size is <= MAX_BLOOM_FILTER_SIZE and the number of hash functions is <= MAX_HASH_FUNCS
95 : //! (catch a filter which was just deserialized which was too big)
96 : bool IsWithinSizeConstraints() const;
97 :
98 : //! Also adds any outputs which match the filter to the filter (to match their spending txes)
99 : bool IsRelevantAndUpdate(const CTransaction& tx);
100 :
101 : //! Checks for empty and full filters to avoid wasting cpu
102 : void UpdateEmptyFull();
103 : };
104 :
105 : /**
106 : * RollingBloomFilter is a probabilistic "keep track of most recently inserted" set.
107 : * Construct it with the number of items to keep track of, and a false-positive
108 : * rate. Unlike CBloomFilter, by default nTweak is set to a cryptographically
109 : * secure random value for you. Similarly rather than clear() the method
110 : * reset() is provided, which also changes nTweak to decrease the impact of
111 : * false-positives.
112 : *
113 : * contains(item) will always return true if item was one of the last N things
114 : * insert()'ed ... but may also return true for items that were not inserted.
115 : */
116 1455 : class CRollingBloomFilter
117 : {
118 : public:
119 : // A random bloom filter calls GetRand() at creation time.
120 : // Don't create global CRollingBloomFilter objects, as they may be
121 : // constructed before the randomizer is properly initialized.
122 : CRollingBloomFilter(unsigned int nElements, double nFPRate);
123 :
124 : void insert(const std::vector<unsigned char>& vKey);
125 : void insert(const uint256& hash);
126 : bool contains(const std::vector<unsigned char>& vKey) const;
127 : bool contains(const uint256& hash) const;
128 :
129 : void reset();
130 :
131 : private:
132 : unsigned int nBloomSize;
133 : unsigned int nInsertions;
134 : CBloomFilter b1, b2;
135 : };
136 :
137 :
138 : #endif // BITCOIN_BLOOM_H
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