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92 lines
3.3 KiB
92 lines
3.3 KiB
// 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 "serialize.h" |
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#include <vector> |
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class COutPoint; |
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class CTransaction; |
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class uint256; |
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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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// First two bits of nFlags control how much IsRelevantAndUpdate actually updates |
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// The remaining bits are reserved |
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enum bloomflags |
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{ |
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BLOOM_UPDATE_NONE = 0, |
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BLOOM_UPDATE_ALL = 1, |
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// Only adds outpoints to the filter if the output is a pay-to-pubkey/pay-to-multisig script |
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BLOOM_UPDATE_P2PUBKEY_ONLY = 2, |
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BLOOM_UPDATE_MASK = 3, |
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}; |
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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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bool isFull; |
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bool isEmpty; |
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unsigned int nHashFuncs; |
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unsigned int nTweak; |
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unsigned char nFlags; |
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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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// nTweak is a constant which is added to the seed value passed to the hash function |
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// It should generally always be a random value (and is largely only exposed for unit testing) |
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// nFlags should be one of the BLOOM_UPDATE_* enums (not _MASK) |
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CBloomFilter(unsigned int nElements, double nFPRate, unsigned int nTweak, unsigned char nFlagsIn); |
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CBloomFilter() : isFull(true) {} |
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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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READWRITE(nTweak); |
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READWRITE(nFlags); |
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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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// Also adds any outputs which match the filter to the filter (to match their spending txes) |
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bool IsRelevantAndUpdate(const CTransaction& tx, const uint256& hash); |
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// Checks for empty and full filters to avoid wasting cpu |
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void UpdateEmptyFull(); |
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}; |
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#endif /* BITCOIN_BLOOM_H */
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