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// Copyright (c) 2012-2016 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_BLOOM_H
#define BITCOIN_BLOOM_H
#include "serialize.h"
#include <vector>
class COutPoint;
class CTransaction;
class uint256;
//! 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 send them.
*
* This allows for significantly more efficient transaction and block downloads.
*
* Because bloom filters are probabilistic, a SPV node can increase the
* false-positive rate, making us send it transactions which aren't actually
* its, allowing clients to trade more bandwidth for more privacy by obfuscating
* which keys are controlled by them.
*/
class CBloomFilter {
private:
std::vector<uint8_t> vData;
bool isFull;
bool isEmpty;
unsigned int nHashFuncs;
unsigned int nTweak;
uint8_t nFlags;
unsigned int Hash(unsigned int nHashNum,
const std::vector<uint8_t> &vDataToHash) const;
// Private constructor for CRollingBloomFilter, no restrictions on size
CBloomFilter(unsigned int nElements, double nFPRate, unsigned int nTweak);
friend class CRollingBloomFilter;
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,
uint8_t nFlagsIn);
CBloomFilter()
: isFull(true), isEmpty(false), nHashFuncs(0), nTweak(0), nFlags(0) {}
ADD_SERIALIZE_METHODS;
template <typename Stream, typename Operation>
inline void SerializationOp(Stream &s, Operation ser_action) {
READWRITE(vData);
READWRITE(nHashFuncs);
READWRITE(nTweak);
READWRITE(nFlags);
}
void insert(const std::vector<uint8_t> &vKey);
void insert(const COutPoint &outpoint);
void insert(const uint256 &hash);
bool contains(const std::vector<uint8_t> &vKey) const;
bool contains(const COutPoint &outpoint) const;
bool contains(const uint256 &hash) const;
void clear();
void reset(unsigned int nNewTweak);
//! 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);
//! Checks for empty and full filters to avoid wasting cpu
void UpdateEmptyFull();
};
/**
* RollingBloomFilter is a probabilistic "keep track of most recently inserted"
* set. Construct it with the number of items to keep track of, and a
* false-positive rate. Unlike CBloomFilter, by default nTweak is set to a
* cryptographically secure random value for you. Similarly rather than clear()
* the method reset() is provided, which also changes nTweak to decrease the
* impact of false-positives.
*
* contains(item) will always return true if item was one of the last N to 1.5*N
* insert()'ed ... but may also return true for items that were not inserted.
*
* It needs around 1.8 bytes per element per factor 0.1 of false positive rate.
* (More accurately: 3/(log(256)*log(2)) * log(1/fpRate) * nElements bytes)
*/
class CRollingBloomFilter {
public:
// A random bloom filter calls GetRand() at creation time. Don't create
// global CRollingBloomFilter objects, as they may be constructed before the
// randomizer is properly initialized.
CRollingBloomFilter(unsigned int nElements, double nFPRate);
void insert(const std::vector<uint8_t> &vKey);
void insert(const uint256 &hash);
bool contains(const std::vector<uint8_t> &vKey) const;
bool contains(const uint256 &hash) const;
void reset();
private:
int nEntriesPerGeneration;
int nEntriesThisGeneration;
int nGeneration;
std::vector<uint64_t> data;
unsigned int nTweak;
int nHashFuncs;
};
#endif // BITCOIN_BLOOM_H

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