


// Copyright (c) 20122016 The Bitcoin Core developers




// Distributed under the MIT software license, see the accompanying




// file COPYING or http://www.opensource.org/licenses/mitlicense.php.








#include "bloom.h"








#include "primitives/transaction.h"




#include "hash.h"




#include "script/script.h"




#include "script/standard.h"




#include "random.h"




#include "streams.h"








#include <math.h>




#include <stdlib.h>








#include <boost/foreach.hpp>








#define LN2SQUARED 0.4804530139182014246671025263266649717305529515945455




#define LN2 0.6931471805599453094172321214581765680755001343602552








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




/**




* 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 limits




*/




vData(std::min((unsigned int)(1 / LN2SQUARED * nElements * log(nFPRate)), MAX_BLOOM_FILTER_SIZE * 8) / 8),




/**




* The 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




*/




isFull(false),




isEmpty(true),




nHashFuncs(std::min((unsigned int)(vData.size() * 8 / nElements * LN2), MAX_HASH_FUNCS)),




nTweak(nTweakIn),




nFlags(nFlagsIn)




{




}








// Private constructor used by CRollingBloomFilter




CBloomFilter::CBloomFilter(unsigned int nElements, double nFPRate, unsigned int nTweakIn) :




vData((unsigned int)(1 / LN2SQUARED * nElements * log(nFPRate)) / 8),




isFull(false),




isEmpty(true),




nHashFuncs((unsigned int)(vData.size() * 8 / nElements * LN2)),




nTweak(nTweakIn),




nFlags(BLOOM_UPDATE_NONE)




{




}








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




{




// 0xFBA4C795 chosen as it guarantees a reasonable bit difference between nHashNum values.




return MurmurHash3(nHashNum * 0xFBA4C795 + nTweak, vDataToHash) % (vData.size() * 8);




}








void CBloomFilter::insert(const std::vector<unsigned char>& vKey)




{




if (isFull)




return;




for (unsigned int i = 0; i < nHashFuncs; i++)




{




unsigned int nIndex = Hash(i, vKey);




// Sets bit nIndex of vData




vData[nIndex >> 3] = (1 << (7 & nIndex));




}




isEmpty = false;




}








void CBloomFilter::insert(const COutPoint& outpoint)




{




CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);




stream << outpoint;




std::vector<unsigned char> data(stream.begin(), stream.end());




insert(data);




}








void CBloomFilter::insert(const uint256& hash)




{




std::vector<unsigned char> data(hash.begin(), hash.end());




insert(data);




}








bool CBloomFilter::contains(const std::vector<unsigned char>& vKey) const




{




if (isFull)




return true;




if (isEmpty)




return false;




for (unsigned int i = 0; i < nHashFuncs; i++)




{




unsigned int nIndex = Hash(i, vKey);




// Checks bit nIndex of vData




if (!(vData[nIndex >> 3] & (1 << (7 & nIndex))))




return false;




}




return true;




}








bool CBloomFilter::contains(const COutPoint& outpoint) const




{




CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);




stream << outpoint;




std::vector<unsigned char> data(stream.begin(), stream.end());




return contains(data);




}








bool CBloomFilter::contains(const uint256& hash) const




{




std::vector<unsigned char> data(hash.begin(), hash.end());




return contains(data);




}








void CBloomFilter::clear()




{




vData.assign(vData.size(),0);




isFull = false;




isEmpty = true;




}








void CBloomFilter::reset(unsigned int nNewTweak)




{




clear();




nTweak = nNewTweak;




}








bool CBloomFilter::IsWithinSizeConstraints() const




{




return vData.size() <= MAX_BLOOM_FILTER_SIZE && nHashFuncs <= MAX_HASH_FUNCS;




}








bool CBloomFilter::IsRelevantAndUpdate(const CTransaction& tx)




{




bool fFound = false;




// Match if the filter contains the hash of tx




// for finding tx when they appear in a block




if (isFull)




return true;




if (isEmpty)




return false;




const uint256& hash = tx.GetHash();




if (contains(hash))




fFound = true;








for (unsigned int i = 0; i < tx.vout.size(); i++)




{




const CTxOut& txout = tx.vout[i];




// Match if the filter contains any arbitrary script data element in any scriptPubKey in tx




// If this matches, also add the specific output that was matched.




// This means clients don't have to update the filter themselves when a new relevant tx




// is discovered in order to find spending transactions, which avoids roundtripping and race conditions.




CScript::const_iterator pc = txout.scriptPubKey.begin();




std::vector<unsigned char> data;




while (pc < txout.scriptPubKey.end())




{




opcodetype opcode;




if (!txout.scriptPubKey.GetOp(pc, opcode, data))




break;




if (data.size() != 0 && contains(data))




{




fFound = true;




if ((nFlags & BLOOM_UPDATE_MASK) == BLOOM_UPDATE_ALL)




insert(COutPoint(hash, i));




else if ((nFlags & BLOOM_UPDATE_MASK) == BLOOM_UPDATE_P2PUBKEY_ONLY)




{




txnouttype type;




std::vector<std::vector<unsigned char> > vSolutions;




if (Solver(txout.scriptPubKey, type, vSolutions) &&




(type == TX_PUBKEY  type == TX_MULTISIG))




insert(COutPoint(hash, i));




}




break;




}




}




}








if (fFound)




return true;








BOOST_FOREACH(const CTxIn& txin, tx.vin)




{




// Match if the filter contains an outpoint tx spends




if (contains(txin.prevout))




return true;








// Match if the filter contains any arbitrary script data element in any scriptSig in tx




CScript::const_iterator pc = txin.scriptSig.begin();




std::vector<unsigned char> data;




while (pc < txin.scriptSig.end())




{




opcodetype opcode;




if (!txin.scriptSig.GetOp(pc, opcode, data))




break;




if (data.size() != 0 && contains(data))




return true;




}




}








return false;




}








void CBloomFilter::UpdateEmptyFull()




{




bool full = true;




bool empty = true;




for (unsigned int i = 0; i < vData.size(); i++)




{




full &= vData[i] == 0xff;




empty &= vData[i] == 0;




}




isFull = full;




isEmpty = empty;




}








CRollingBloomFilter::CRollingBloomFilter(unsigned int nElements, double fpRate)




{




double logFpRate = log(fpRate);




/* The optimal number of hash functions is log(fpRate) / log(0.5), but




* restrict it to the range 150. */




nHashFuncs = std::max(1, std::min((int)round(logFpRate / log(0.5)), 50));




/* In this rolling bloom filter, we'll store between 2 and 3 generations of nElements / 2 entries. */




nEntriesPerGeneration = (nElements + 1) / 2;




uint32_t nMaxElements = nEntriesPerGeneration * 3;




/* The maximum fpRate = pow(1.0  exp(nHashFuncs * nMaxElements / nFilterBits), nHashFuncs)




* => pow(fpRate, 1.0 / nHashFuncs) = 1.0  exp(nHashFuncs * nMaxElements / nFilterBits)




* => 1.0  pow(fpRate, 1.0 / nHashFuncs) = exp(nHashFuncs * nMaxElements / nFilterBits)




* => log(1.0  pow(fpRate, 1.0 / nHashFuncs)) = nHashFuncs * nMaxElements / nFilterBits




* => nFilterBits = nHashFuncs * nMaxElements / log(1.0  pow(fpRate, 1.0 / nHashFuncs))




* => nFilterBits = nHashFuncs * nMaxElements / log(1.0  exp(logFpRate / nHashFuncs))




*/




uint32_t nFilterBits = (uint32_t)ceil(1.0 * nHashFuncs * nMaxElements / log(1.0  exp(logFpRate / nHashFuncs)));




data.clear();




/* For each data element we need to store 2 bits. If both bits are 0, the




* bit is treated as unset. If the bits are (01), (10), or (11), the bit is




* treated as set in generation 1, 2, or 3 respectively.




* These bits are stored in separate integers: position P corresponds to bit




* (P & 63) of the integers data[(P >> 6) * 2] and data[(P >> 6) * 2 + 1]. */




data.resize(((nFilterBits + 63) / 64) << 1);




reset();




}








/* Similar to CBloomFilter::Hash */




static inline uint32_t RollingBloomHash(unsigned int nHashNum, uint32_t nTweak, const std::vector<unsigned char>& vDataToHash) {




return MurmurHash3(nHashNum * 0xFBA4C795 + nTweak, vDataToHash);




}








void CRollingBloomFilter::insert(const std::vector<unsigned char>& vKey)




{




if (nEntriesThisGeneration == nEntriesPerGeneration) {




nEntriesThisGeneration = 0;




nGeneration++;




if (nGeneration == 4) {




nGeneration = 1;




}




uint64_t nGenerationMask1 = 0  (uint64_t)(nGeneration & 1);




uint64_t nGenerationMask2 = 0  (uint64_t)(nGeneration >> 1);




/* Wipe old entries that used this generation number. */




for (uint32_t p = 0; p < data.size(); p += 2) {




uint64_t p1 = data[p], p2 = data[p + 1];




uint64_t mask = (p1 ^ nGenerationMask1)  (p2 ^ nGenerationMask2);




data[p] = p1 & mask;




data[p + 1] = p2 & mask;




}




}




nEntriesThisGeneration++;








for (int n = 0; n < nHashFuncs; n++) {




uint32_t h = RollingBloomHash(n, nTweak, vKey);




int bit = h & 0x3F;




uint32_t pos = (h >> 6) % data.size();




/* The lowest bit of pos is ignored, and set to zero for the first bit, and to one for the second. */




data[pos & ~1] = (data[pos & ~1] & ~(((uint64_t)1) << bit))  ((uint64_t)(nGeneration & 1)) << bit;




data[pos  1] = (data[pos  1] & ~(((uint64_t)1) << bit))  ((uint64_t)(nGeneration >> 1)) << bit;




}




}








void CRollingBloomFilter::insert(const uint256& hash)




{




std::vector<unsigned char> vData(hash.begin(), hash.end());




insert(vData);




}








bool CRollingBloomFilter::contains(const std::vector<unsigned char>& vKey) const




{




for (int n = 0; n < nHashFuncs; n++) {




uint32_t h = RollingBloomHash(n, nTweak, vKey);




int bit = h & 0x3F;




uint32_t pos = (h >> 6) % data.size();




/* If the relevant bit is not set in either data[pos & ~1] or data[pos  1], the filter does not contain vKey */




if (!(((data[pos & ~1]  data[pos  1]) >> bit) & 1)) {




return false;




}




}




return true;




}








bool CRollingBloomFilter::contains(const uint256& hash) const




{




std::vector<unsigned char> vData(hash.begin(), hash.end());




return contains(vData);




}








void CRollingBloomFilter::reset()




{




nTweak = GetRand(std::numeric_limits<unsigned int>::max());




nEntriesThisGeneration = 0;




nGeneration = 1;




for (std::vector<uint64_t>::iterator it = data.begin(); it != data.end(); it++) {




*it = 0;




}




}
