CBloomFilter Class Reference

#include <bloom.h>

Public Member Functions
	CBloomFilter (const unsigned int nElements, const double nFPRate, const unsigned int nTweak, unsigned char nFlagsIn)
	CBloomFilter ()
template<typename Stream , typename Operation >
void	SerializationOp (Stream &s, Operation ser_action)
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
void	clear ()
void	reset (const unsigned int nNewTweak)
bool	IsWithinSizeConstraints () const
bool	IsRelevantAndUpdate (const CTransaction &tx)
	Also adds any outputs which match the filter to the filter (to match their spending txes) More...
void	UpdateEmptyFull ()
	Checks for empty and full filters to avoid wasting cpu. More...

Public Attributes
	ADD_SERIALIZE_METHODS

Private Member Functions
unsigned int	Hash (unsigned int nHashNum, const std::vector< unsigned char > &vDataToHash) const

Private Attributes
std::vector< unsigned char >	vData
bool	isFull
bool	isEmpty
unsigned int	nHashFuncs
unsigned int	nTweak
unsigned char	nFlags

Detailed Description

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.

Constructor & Destructor Documentation

CBloomFilter() [1/2]

CBloomFilter::CBloomFilter	(	const unsigned int	nElements,
		const double	nFPRate,
		const unsigned int	nTweakIn,
		unsigned char	nFlagsIn
	)

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)

The ideal size for a bloom filter with a given number of elements and false positive rate is:

• nElements * log(fp rate) / ln(2)^2 We ignore filter parameters which will create a bloom filter larger than the protocol limitsThe ideal number of hash functions is filter size * ln(2) / number of elements Again, we ignore filter parameters which will create a bloom filter with more hash functions than the protocol limits See https://en.wikipedia.org/wiki/Bloom_filter for an explanation of these formulas

CBloomFilter() [2/2]

CBloomFilter::CBloomFilter ( )

inline

Member Function Documentation

clear()

void CBloomFilter::clear

(

)

contains() [1/3]

bool CBloomFilter::contains

(

const std::vector< unsigned char > &

vKey

)

const

contains() [2/3]

bool CBloomFilter::contains

(

const COutPoint &

outpoint

)

const

contains() [3/3]

bool CBloomFilter::contains

(

const uint256 &

hash

)

const

Hash()

unsigned int CBloomFilter::Hash ( unsigned int  nHashNum, const std::vector< unsigned char > &  vDataToHash  ) const

inlineprivate

insert() [1/3]

void CBloomFilter::insert

(

const std::vector< unsigned char > &

vKey

)

insert() [2/3]

void CBloomFilter::insert

(

const COutPoint &

outpoint

)

insert() [3/3]

void CBloomFilter::insert

(

const uint256 &

hash

)

IsRelevantAndUpdate()

bool CBloomFilter::IsRelevantAndUpdate

(

const CTransaction &

tx

)

Also adds any outputs which match the filter to the filter (to match their spending txes)

IsWithinSizeConstraints()

bool CBloomFilter::IsWithinSizeConstraints

(

)

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)

reset()

void CBloomFilter::reset

(

const unsigned int

nNewTweak

)

SerializationOp()

template<typename Stream , typename Operation >

void CBloomFilter::SerializationOp ( Stream &  s, Operation  ser_action  )

inline

UpdateEmptyFull()

void CBloomFilter::UpdateEmptyFull

(

)

Checks for empty and full filters to avoid wasting cpu.

Member Data Documentation

ADD_SERIALIZE_METHODS

CBloomFilter::ADD_SERIALIZE_METHODS

isEmpty

bool CBloomFilter::isEmpty

private

isFull

bool CBloomFilter::isFull

private

nFlags

unsigned char CBloomFilter::nFlags

private

nHashFuncs

unsigned int CBloomFilter::nHashFuncs

private

nTweak

unsigned int CBloomFilter::nTweak

private

vData

std::vector<unsigned char> CBloomFilter::vData

private

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The documentation for this class was generated from the following files:

• src/bloom.h
• src/bloom.cpp