71 lines
2.5 KiB
C++
71 lines
2.5 KiB
C++
// Copyright (c) 2012 The Bitcoin developers
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// Distributed under the MIT/X11 software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#ifndef BITCOIN_BLOOM_H
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#define BITCOIN_BLOOM_H
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#include <vector>
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#include "uint256.h"
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#include "serialize.h"
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class COutPoint;
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class CTransaction;
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// 20,000 items with fp rate < 0.1% or 10,000 items and <0.0001%
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static const unsigned int MAX_BLOOM_FILTER_SIZE = 36000; // bytes
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static const unsigned int MAX_HASH_FUNCS = 50;
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/**
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* BloomFilter is a probabilistic filter which SPV clients provide
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* so that we can filter the transactions we sends them.
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*
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* This allows for significantly more efficient transaction and block downloads.
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*
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* Because bloom filters are probabilistic, an SPV node can increase the false-
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* positive rate, making us send them transactions which aren't actually theirs,
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* allowing clients to trade more bandwidth for more privacy by obfuscating which
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* keys are owned by them.
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*/
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class CBloomFilter
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{
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private:
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std::vector<unsigned char> vData;
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unsigned int nHashFuncs;
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unsigned int Hash(unsigned int nHashNum, const std::vector<unsigned char>& vDataToHash) const;
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public:
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// Creates a new bloom filter which will provide the given fp rate when filled with the given number of elements
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// Note that if the given parameters will result in a filter outside the bounds of the protocol limits,
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// the filter created will be as close to the given parameters as possible within the protocol limits.
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// This will apply if nFPRate is very low or nElements is unreasonably high.
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CBloomFilter(unsigned int nElements, double nFPRate);
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// Using a filter initialized with this results in undefined behavior
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// Should only be used for deserialization
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CBloomFilter() {}
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IMPLEMENT_SERIALIZE
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(
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READWRITE(vData);
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READWRITE(nHashFuncs);
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)
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void insert(const std::vector<unsigned char>& vKey);
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void insert(const COutPoint& outpoint);
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void insert(const uint256& hash);
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bool contains(const std::vector<unsigned char>& vKey) const;
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bool contains(const COutPoint& outpoint) const;
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bool contains(const uint256& hash) const;
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// True if the size is <= MAX_BLOOM_FILTER_SIZE and the number of hash functions is <= MAX_HASH_FUNCS
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// (catch a filter which was just deserialized which was too big)
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bool IsWithinSizeConstraints() const;
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bool IsTransactionRelevantToFilter(const CTransaction& tx, const uint256& hash) const;
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};
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#endif /* BITCOIN_BLOOM_H */
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