src/bloom.cpp

   1 // Copyright (c) 2012-2014 The Bitcoin Core developers
   2 // Distributed under the MIT software license, see the accompanying
   3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   4
   5 #include "bloom.h"
   6
   7 #include "primitives/transaction.h"
   8 #include "hash.h"
   9 #include "script/script.h"
  10 #include "script/standard.h"
  11 #include "streams.h"
  12
  13 #include <math.h>
  14 #include <stdlib.h>
  15
  16 #include <boost/foreach.hpp>
  17
  18 #define LN2SQUARED 0.4804530139182014246671025263266649717305529515945455
  19 #define LN2 0.6931471805599453094172321214581765680755001343602552
  20
  21 using namespace std;
  22
  23 CBloomFilter::CBloomFilter(unsigned int nElements, double nFPRate, unsigned int nTweakIn, unsigned char nFlagsIn) :
  24 /**
  25  * The ideal size for a bloom filter with a given number of elements and false positive rate is:
  26  * - nElements * log(fp rate) / ln(2)^2
  27  * We ignore filter parameters which will create a bloom filter larger than the protocol limits
  28  */
  29 vData(min((unsigned int)(-1  / LN2SQUARED * nElements * log(nFPRate)), MAX_BLOOM_FILTER_SIZE * 8) / 8),
  30 /**
  31  * The ideal number of hash functions is filter size * ln(2) / number of elements
  32  * Again, we ignore filter parameters which will create a bloom filter with more hash functions than the protocol limits
  33  * See https://en.wikipedia.org/wiki/Bloom_filter for an explanation of these formulas
  34  */
  35 isFull(false),
  36 isEmpty(false),
  37 nHashFuncs(min((unsigned int)(vData.size() * 8 / nElements * LN2), MAX_HASH_FUNCS)),
  38 nTweak(nTweakIn),
  39 nFlags(nFlagsIn)
  40 {
  41 }
  42
  43 inline unsigned int CBloomFilter::Hash(unsigned int nHashNum, const std::vector<unsigned char>& vDataToHash) const
  44 {
  45     // 0xFBA4C795 chosen as it guarantees a reasonable bit difference between nHashNum values.
  46     return MurmurHash3(nHashNum * 0xFBA4C795 + nTweak, vDataToHash) % (vData.size() * 8);
  47 }
  48
  49 void CBloomFilter::insert(const vector<unsigned char>& vKey)
  50 {
  51     if (isFull)
  52         return;
  53     for (unsigned int i = 0; i < nHashFuncs; i++)
  54     {
  55         unsigned int nIndex = Hash(i, vKey);
  56         // Sets bit nIndex of vData
  57         vData[nIndex >> 3] |= (1 << (7 & nIndex));
  58     }
  59     isEmpty = false;
  60 }
  61
  62 void CBloomFilter::insert(const COutPoint& outpoint)
  63 {
  64     CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
  65     stream << outpoint;
  66     vector<unsigned char> data(stream.begin(), stream.end());
  67     insert(data);
  68 }
  69
  70 void CBloomFilter::insert(const uint256& hash)
  71 {
  72     vector<unsigned char> data(hash.begin(), hash.end());
  73     insert(data);
  74 }
  75
  76 bool CBloomFilter::contains(const vector<unsigned char>& vKey) const
  77 {
  78     if (isFull)
  79         return true;
  80     if (isEmpty)
  81         return false;
  82     for (unsigned int i = 0; i < nHashFuncs; i++)
  83     {
  84         unsigned int nIndex = Hash(i, vKey);
  85         // Checks bit nIndex of vData
  86         if (!(vData[nIndex >> 3] & (1 << (7 & nIndex))))
  87             return false;
  88     }
  89     return true;
  90 }
  91
  92 bool CBloomFilter::contains(const COutPoint& outpoint) const
  93 {
  94     CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
  95     stream << outpoint;
  96     vector<unsigned char> data(stream.begin(), stream.end());
  97     return contains(data);
  98 }
  99
 100 bool CBloomFilter::contains(const uint256& hash) const
 101 {
 102     vector<unsigned char> data(hash.begin(), hash.end());
 103     return contains(data);
 104 }
 105
 106 void CBloomFilter::clear()
 107 {
 108     vData.assign(vData.size(),0);
 109     isFull = false;
 110     isEmpty = true;
 111 }
 112
 113 bool CBloomFilter::IsWithinSizeConstraints() const
 114 {
 115     return vData.size() <= MAX_BLOOM_FILTER_SIZE && nHashFuncs <= MAX_HASH_FUNCS;
 116 }
 117
 118 bool CBloomFilter::IsRelevantAndUpdate(const CTransaction& tx)
 119 {
 120     bool fFound = false;
 121     // Match if the filter contains the hash of tx
 122     //  for finding tx when they appear in a block
 123     if (isFull)
 124         return true;
 125     if (isEmpty)
 126         return false;
 127     const uint256& hash = tx.GetHash();
 128     if (contains(hash))
 129         fFound = true;
 130
 131     for (unsigned int i = 0; i < tx.vout.size(); i++)
 132     {
 133         const CTxOut& txout = tx.vout[i];
 134         // Match if the filter contains any arbitrary script data element in any scriptPubKey in tx
 135         // If this matches, also add the specific output that was matched.
 136         // This means clients don't have to update the filter themselves when a new relevant tx
 137         // is discovered in order to find spending transactions, which avoids round-tripping and race conditions.
 138         CScript::const_iterator pc = txout.scriptPubKey.begin();
 139         vector<unsigned char> data;
 140         while (pc < txout.scriptPubKey.end())
 141         {
 142             opcodetype opcode;
 143             if (!txout.scriptPubKey.GetOp(pc, opcode, data))
 144                 break;
 145             if (data.size() != 0 && contains(data))
 146             {
 147                 fFound = true;
 148                 if ((nFlags & BLOOM_UPDATE_MASK) == BLOOM_UPDATE_ALL)
 149                     insert(COutPoint(hash, i));
 150                 else if ((nFlags & BLOOM_UPDATE_MASK) == BLOOM_UPDATE_P2PUBKEY_ONLY)
 151                 {
 152                     txnouttype type;
 153                     vector<vector<unsigned char> > vSolutions;
 154                     if (Solver(txout.scriptPubKey, type, vSolutions) &&
 155                             (type == TX_PUBKEY || type == TX_MULTISIG))
 156                         insert(COutPoint(hash, i));
 157                 }
 158                 break;
 159             }
 160         }
 161     }
 162
 163     if (fFound)
 164         return true;
 165
 166     BOOST_FOREACH(const CTxIn& txin, tx.vin)
 167     {
 168         // Match if the filter contains an outpoint tx spends
 169         if (contains(txin.prevout))
 170             return true;
 171
 172         // Match if the filter contains any arbitrary script data element in any scriptSig in tx
 173         CScript::const_iterator pc = txin.scriptSig.begin();
 174         vector<unsigned char> data;
 175         while (pc < txin.scriptSig.end())
 176         {
 177             opcodetype opcode;
 178             if (!txin.scriptSig.GetOp(pc, opcode, data))
 179                 break;
 180             if (data.size() != 0 && contains(data))
 181                 return true;
 182         }
 183     }
 184
 185     return false;
 186 }
 187
 188 void CBloomFilter::UpdateEmptyFull()
 189 {
 190     bool full = true;
 191     bool empty = true;
 192     for (unsigned int i = 0; i < vData.size(); i++)
 193     {
 194         full &= vData[i] == 0xff;
 195         empty &= vData[i] == 0;
 196     }
 197     isFull = full;
 198     isEmpty = empty;
 199 }