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Diffstat (limited to 'src/bloom.h')
-rw-r--r-- | src/bloom.h | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/src/bloom.h b/src/bloom.h new file mode 100644 index 0000000000..389ae748e6 --- /dev/null +++ b/src/bloom.h @@ -0,0 +1,88 @@ +// Copyright (c) 2012 The Bitcoin developers +// Distributed under the MIT/X11 software license, see the accompanying +// file COPYING or http://www.opensource.org/licenses/mit-license.php. +#ifndef BITCOIN_BLOOM_H +#define BITCOIN_BLOOM_H + +#include <vector> + +#include "uint256.h" +#include "serialize.h" + +class COutPoint; +class CTransaction; + +// 20,000 items with fp rate < 0.1% or 10,000 items and <0.0001% +static const unsigned int MAX_BLOOM_FILTER_SIZE = 36000; // bytes +static const unsigned int MAX_HASH_FUNCS = 50; + +// First two bits of nFlags control how much IsRelevantAndUpdate actually updates +// The remaining bits are reserved +enum bloomflags +{ + BLOOM_UPDATE_NONE = 0, + BLOOM_UPDATE_ALL = 1, + // Only adds outpoints to the filter if the output is a pay-to-pubkey/pay-to-multisig script + BLOOM_UPDATE_P2PUBKEY_ONLY = 2, + BLOOM_UPDATE_MASK = 3, +}; + +/** + * BloomFilter is a probabilistic filter which SPV clients provide + * so that we can filter the transactions we sends them. + * + * This allows for significantly more efficient transaction and block downloads. + * + * Because bloom filters are probabilistic, an SPV node can increase the false- + * positive rate, making us send them transactions which aren't actually theirs, + * allowing clients to trade more bandwidth for more privacy by obfuscating which + * keys are owned by them. + */ +class CBloomFilter +{ +private: + std::vector<unsigned char> vData; + unsigned int nHashFuncs; + unsigned int nTweak; + unsigned char nFlags; + + unsigned int Hash(unsigned int nHashNum, const std::vector<unsigned char>& vDataToHash) const; + +public: + // Creates a new bloom filter which will provide the given fp rate when filled with the given number of elements + // Note that if the given parameters will result in a filter outside the bounds of the protocol limits, + // the filter created will be as close to the given parameters as possible within the protocol limits. + // This will apply if nFPRate is very low or nElements is unreasonably high. + // nTweak is a constant which is added to the seed value passed to the hash function + // It should generally always be a random value (and is largely only exposed for unit testing) + // nFlags should be one of the BLOOM_UPDATE_* enums (not _MASK) + CBloomFilter(unsigned int nElements, double nFPRate, unsigned int nTweak, unsigned char nFlagsIn); + // Using a filter initialized with this results in undefined behavior + // Should only be used for deserialization + CBloomFilter() {} + + IMPLEMENT_SERIALIZE + ( + READWRITE(vData); + READWRITE(nHashFuncs); + READWRITE(nTweak); + READWRITE(nFlags); + ) + + void insert(const std::vector<unsigned char>& vKey); + void insert(const COutPoint& outpoint); + void insert(const uint256& hash); + + bool contains(const std::vector<unsigned char>& vKey) const; + bool contains(const COutPoint& outpoint) const; + bool contains(const uint256& hash) const; + + // True if the size is <= MAX_BLOOM_FILTER_SIZE and the number of hash functions is <= MAX_HASH_FUNCS + // (catch a filter which was just deserialized which was too big) + bool IsWithinSizeConstraints() const; + + // Also adds any outputs which match the filter to the filter (to match their spending txes) + bool IsRelevantAndUpdate(const CTransaction& tx, const uint256& hash); +}; + +#endif /* BITCOIN_BLOOM_H */ |