text: // Copyright (c) 2012-2014 The Bitcoin developers
  // Copyright (c) 2017 The PIVX developers
  // Copyright (c) 2018 The amaterasu developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include "bloom.h"
  
  #include "hash.h"
  #include "primitives/transaction.h"
  #include "script/script.h"
  #include "script/standard.h"
  #include "streams.h"
  
  #include <math.h>
  #include <stdlib.h>
  
  #include <boost/foreach.hpp>
  
  #define LN2SQUARED 0.4804530139182014246671025263266649717305529515945455
  #define LN2 0.6931471805599453094172321214581765680755001343602552
  
  using namespace std;
  
  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(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(false),
    nHashFuncs(min((unsigned int)(vData.size() * 8 / nElements * LN2), MAX_HASH_FUNCS)),
    nTweak(nTweakIn),
    nFlags(nFlagsIn)
  {
  }
  
  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 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;
      vector<unsigned char> data(stream.begin(), stream.end());
      insert(data);
  }
  
  void CBloomFilter::insert(const uint256& hash)
  {
      vector<unsigned char> data(hash.begin(), hash.end());
      insert(data);
  }
  
  bool CBloomFilter::contains(const 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;
      vector<unsigned char> data(stream.begin(), stream.end());
      return contains(data);
  }
  
  bool CBloomFilter::contains(const uint256& hash) const
  {
      vector<unsigned char> data(hash.begin(), hash.end());
      return contains(data);
  }
  
  void CBloomFilter::clear()
  {
      vData.assign(vData.size(), 0);
      isFull = false;
      isEmpty = true;
  }
  
  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 round-tripping and race conditions.
          CScript::const_iterator pc = txout.scriptPubKey.begin();
          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;
                      vector<vector<unsigned char> > vSolutions;
                      if (Solver(txout.scriptPubKey, type, vSolutions) &&
                          (type == TX_PUBKEY || type == TX_MULTISIG || type == TX_MULTISIG_DATA))
                          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();
          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;
  }
  