Add a CBloomFilter class for use as a transaction filter.
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@ -155,6 +155,7 @@ HEADERS += src/qt/bitcoingui.h \
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src/script.h \
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src/init.h \
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src/irc.h \
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src/bloom.h \
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src/mruset.h \
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src/json/json_spirit_writer_template.h \
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src/json/json_spirit_writer.h \
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@ -223,6 +224,7 @@ SOURCES += src/qt/bitcoin.cpp src/qt/bitcoingui.cpp \
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src/init.cpp \
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src/net.cpp \
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src/irc.cpp \
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src/bloom.cpp \
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src/checkpoints.cpp \
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src/addrman.cpp \
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src/db.cpp \
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133
src/bloom.cpp
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133
src/bloom.cpp
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// 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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#include <math.h>
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#include <stdlib.h>
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#include "bloom.h"
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#include "main.h"
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#include "script.h"
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#define LN2SQUARED 0.4804530139182014246671025263266649717305529515945455
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#define LN2 0.6931471805599453094172321214581765680755001343602552
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using namespace std;
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static const unsigned char bit_mask[8] = {0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80};
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CBloomFilter::CBloomFilter(unsigned int nElements, double nFPRate) :
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// The ideal size for a bloom filter with a given number of elements and false positive rate is:
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// - nElements * log(fp rate) / ln(2)^2
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// We ignore filter parameters which will create a bloom filter larger than the protocol limits
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vData(min((unsigned int)(-1 / LN2SQUARED * nElements * log(nFPRate)), MAX_BLOOM_FILTER_SIZE * 8) / 8),
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// The ideal number of hash functions is filter size * ln(2) / number of elements
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// Again, we ignore filter parameters which will create a bloom filter with more hash functions than the protocol limits
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// See http://en.wikipedia.org/wiki/Bloom_filter for an explanation of these formulas
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nHashFuncs(min((unsigned int)(vData.size() * 8 / nElements * LN2), MAX_HASH_FUNCS))
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{
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}
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inline unsigned int CBloomFilter::Hash(unsigned int nHashNum, const std::vector<unsigned char>& vDataToHash) const
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{
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// 0xFBA4C795 chosen as it guarantees a reasonable bit difference between nHashNum values.
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return MurmurHash3(nHashNum * 0xFBA4C795, vDataToHash) % (vData.size() * 8);
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}
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void CBloomFilter::insert(const vector<unsigned char>& vKey)
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{
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for (unsigned int i = 0; i < nHashFuncs; i++)
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{
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unsigned int nIndex = Hash(i, vKey);
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// Sets bit nIndex of vData
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vData[nIndex >> 3] |= bit_mask[7 & nIndex];
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}
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}
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void CBloomFilter::insert(const COutPoint& outpoint)
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{
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CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
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stream << outpoint;
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vector<unsigned char> data(stream.begin(), stream.end());
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insert(data);
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}
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void CBloomFilter::insert(const uint256& hash)
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{
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vector<unsigned char> data(hash.begin(), hash.end());
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insert(data);
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}
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bool CBloomFilter::contains(const vector<unsigned char>& vKey) const
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{
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for (unsigned int i = 0; i < nHashFuncs; i++)
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{
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unsigned int nIndex = Hash(i, vKey);
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// Checks bit nIndex of vData
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if (!(vData[nIndex >> 3] & bit_mask[7 & nIndex]))
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return false;
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}
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return true;
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}
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bool CBloomFilter::contains(const COutPoint& outpoint) const
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{
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CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
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stream << outpoint;
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vector<unsigned char> data(stream.begin(), stream.end());
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return contains(data);
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}
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bool CBloomFilter::contains(const uint256& hash) const
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{
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vector<unsigned char> data(hash.begin(), hash.end());
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return contains(data);
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}
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bool CBloomFilter::IsWithinSizeConstraints() const
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{
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return vData.size() <= MAX_BLOOM_FILTER_SIZE && nHashFuncs <= MAX_HASH_FUNCS;
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}
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bool CBloomFilter::IsTransactionRelevantToFilter(const CTransaction& tx) const
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{
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// Match if the filter contains the hash of tx
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// for finding tx when they appear in a block
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if (contains(tx.GetHash()))
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return true;
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BOOST_FOREACH(const CTxOut& txout, tx.vout)
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{
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// Match if the filter contains any arbitrary script data element in any scriptPubKey in tx
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CScript::const_iterator pc = txout.scriptPubKey.begin();
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vector<unsigned char> data;
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while (pc < txout.scriptPubKey.end())
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{
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opcodetype opcode;
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if (!txout.scriptPubKey.GetOp(pc, opcode, data))
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break;
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if (data.size() != 0 && contains(data))
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return true;
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}
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}
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BOOST_FOREACH(const CTxIn& txin, tx.vin)
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{
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// Match if the filter contains an outpoint tx spends
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if (contains(txin.prevout))
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return true;
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// Match if the filter contains any arbitrary script data element in any scriptSig in tx
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CScript::const_iterator pc = txin.scriptSig.begin();
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vector<unsigned char> data;
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while (pc < txin.scriptSig.end())
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{
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opcodetype opcode;
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if (!txin.scriptSig.GetOp(pc, opcode, data))
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break;
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if (data.size() != 0 && contains(data))
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return true;
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}
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}
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return false;
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}
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70
src/bloom.h
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70
src/bloom.h
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@ -0,0 +1,70 @@
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// 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 <vector>
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#include "uint256.h"
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#include "serialize.h"
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class COutPoint;
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class CTransaction;
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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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/**
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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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unsigned int nHashFuncs;
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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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CBloomFilter(unsigned int nElements, double nFPRate);
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// Using a filter initialized with this results in undefined behavior
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// Should only be used for deserialization
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CBloomFilter() {}
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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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)
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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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bool IsTransactionRelevantToFilter(const CTransaction& tx) const;
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};
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#endif /* BITCOIN_BLOOM_H */
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@ -84,6 +84,7 @@ OBJS= \
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obj/walletdb.o \
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obj/noui.o \
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obj/hash.o \
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obj/bloom.o \
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obj/leveldb.o \
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obj/txdb.o
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@ -79,6 +79,7 @@ OBJS= \
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obj/wallet.o \
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obj/walletdb.o \
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obj/hash.o \
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obj/bloom.o \
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obj/noui.o \
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obj/leveldb.o \
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obj/txdb.o
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@ -97,6 +97,7 @@ OBJS= \
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obj/wallet.o \
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obj/walletdb.o \
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obj/hash.o \
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obj/bloom.o \
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obj/noui.o \
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obj/leveldb.o \
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obj/txdb.o
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@ -128,6 +128,7 @@ OBJS= \
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obj/wallet.o \
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obj/walletdb.o \
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obj/hash.o \
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obj/bloom.o \
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obj/noui.o \
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obj/leveldb.o \
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obj/txdb.o
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