text: // Copyright (c) 2012 Pieter Wuille
  // Distributed under the MIT/X11 software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include "addrman.h"
  
  using namespace std;
  
  int CAddrInfo::GetTriedBucket(const std::vector<unsigned char> &nKey) const
  {
      CDataStream ss1(SER_GETHASH, 0);
      std::vector<unsigned char> vchKey = GetKey();
      ss1 << nKey << vchKey;
      uint64 hash1 = Hash(ss1.begin(), ss1.end()).Get64();
  
      CDataStream ss2(SER_GETHASH, 0);
      std::vector<unsigned char> vchGroupKey = GetGroup();
      ss2 << nKey << vchGroupKey << (hash1 % ADDRMAN_TRIED_BUCKETS_PER_GROUP);
      uint64 hash2 = Hash(ss2.begin(), ss2.end()).Get64();
      return hash2 % ADDRMAN_TRIED_BUCKET_COUNT;
  }
  
  int CAddrInfo::GetNewBucket(const std::vector<unsigned char> &nKey, const CNetAddr& src) const
  {
      CDataStream ss1(SER_GETHASH, 0);
      std::vector<unsigned char> vchGroupKey = GetGroup();
      std::vector<unsigned char> vchSourceGroupKey = src.GetGroup();
      ss1 << nKey << vchGroupKey << vchSourceGroupKey;
      uint64 hash1 = Hash(ss1.begin(), ss1.end()).Get64();
  
      CDataStream ss2(SER_GETHASH, 0);
      ss2 << nKey << vchSourceGroupKey << (hash1 % ADDRMAN_NEW_BUCKETS_PER_SOURCE_GROUP);
      uint64 hash2 = Hash(ss2.begin(), ss2.end()).Get64();
      return hash2 % ADDRMAN_NEW_BUCKET_COUNT;
  }
  
  bool CAddrInfo::IsTerrible(int64 nNow) const
  {
      if (nLastTry && nLastTry >= nNow-60) // never remove things tried the last minute
          return false;
  
      if (nTime > nNow + 10*60) // came in a flying DeLorean
          return true;
  
      if (nTime==0 || nNow-nTime > ADDRMAN_HORIZON_DAYS*86400) // not seen in over a month
          return true;
  
      if (nLastSuccess==0 && nAttempts>=ADDRMAN_RETRIES) // tried three times and never a success
          return true;
  
      if (nNow-nLastSuccess > ADDRMAN_MIN_FAIL_DAYS*86400 && nAttempts>=ADDRMAN_MAX_FAILURES) // 10 successive failures in the last week
          return true;
  
      return false;
  }
  
  double CAddrInfo::GetChance(int64 nNow) const
  {
      double fChance = 1.0;
  
      int64 nSinceLastSeen = nNow - nTime;
      int64 nSinceLastTry = nNow - nLastTry;
  
      if (nSinceLastSeen < 0) nSinceLastSeen = 0;
      if (nSinceLastTry < 0) nSinceLastTry = 0;
  
      fChance *= 600.0 / (600.0 + nSinceLastSeen);
  
      // deprioritize very recent attempts away
      if (nSinceLastTry < 60*10)
          fChance *= 0.01;
  
      // deprioritize 50% after each failed attempt
      for (int n=0; n<nAttempts; n++)
          fChance /= 1.5;
  
      return fChance;
  }
  
  CAddrInfo* CAddrMan::Find(const CNetAddr& addr, int *pnId)
  {
      std::map<CNetAddr, int>::iterator it = mapAddr.find(addr);
      if (it == mapAddr.end())
          return NULL;
      if (pnId)
          *pnId = (*it).second;
      std::map<int, CAddrInfo>::iterator it2 = mapInfo.find((*it).second);
      if (it2 != mapInfo.end())
          return &(*it2).second;
      return NULL;
  }
  
  CAddrInfo* CAddrMan::Create(const CAddress &addr, const CNetAddr &addrSource, int *pnId)
  {
      int nId = nIdCount++;
      mapInfo[nId] = CAddrInfo(addr, addrSource);
      mapAddr[addr] = nId;
      mapInfo[nId].nRandomPos = vRandom.size();
      vRandom.push_back(nId);
      if (pnId)
          *pnId = nId;
      return &mapInfo[nId];
  }
  
  void CAddrMan::SwapRandom(unsigned int nRndPos1, unsigned int nRndPos2)
  {
      if (nRndPos1 == nRndPos2)
          return;
  
      assert(nRndPos1 < vRandom.size() && nRndPos2 < vRandom.size());
  
      int nId1 = vRandom[nRndPos1];
      int nId2 = vRandom[nRndPos2];
  
      assert(mapInfo.count(nId1) == 1);
      assert(mapInfo.count(nId2) == 1);
  
      mapInfo[nId1].nRandomPos = nRndPos2;
      mapInfo[nId2].nRandomPos = nRndPos1;
  
      vRandom[nRndPos1] = nId2;
      vRandom[nRndPos2] = nId1;
  }
  
  int CAddrMan::SelectTried(int nKBucket)
  {
      std::vector<int> &vTried = vvTried[nKBucket];
  
      // random shuffle the first few elements (using the entire list)
      // find the least recently tried among them
      int64 nOldest = -1;
      int nOldestPos = -1;
      for (unsigned int i = 0; i < ADDRMAN_TRIED_ENTRIES_INSPECT_ON_EVICT && i < vTried.size(); i++)
      {
          int nPos = GetRandInt(vTried.size() - i) + i;
          int nTemp = vTried[nPos];
          vTried[nPos] = vTried[i];
          vTried[i] = nTemp;
          assert(nOldest == -1 || mapInfo.count(nTemp) == 1);
          if (nOldest == -1 || mapInfo[nTemp].nLastSuccess < mapInfo[nOldest].nLastSuccess) {
             nOldest = nTemp;
             nOldestPos = nPos;
          }
      }
  
      return nOldestPos;
  }
  
  int CAddrMan::ShrinkNew(int nUBucket)
  {
      assert(nUBucket >= 0 && (unsigned int)nUBucket < vvNew.size());
      std::set<int> &vNew = vvNew[nUBucket];
  
      // first look for deletable items
      for (std::set<int>::iterator it = vNew.begin(); it != vNew.end(); it++)
      {
          assert(mapInfo.count(*it));
          CAddrInfo &info = mapInfo[*it];
          if (info.IsTerrible())
          {
              if (--info.nRefCount == 0)
              {
                  SwapRandom(info.nRandomPos, vRandom.size()-1);
                  vRandom.pop_back();
                  mapAddr.erase(info);
                  mapInfo.erase(*it);
                  nNew--;
              }
              vNew.erase(it);
              return 0;
          }
      }
  
      // otherwise, select four randomly, and pick the oldest of those to replace
      int n[4] = {GetRandInt(vNew.size()), GetRandInt(vNew.size()), GetRandInt(vNew.size()), GetRandInt(vNew.size())};
      int nI = 0;
      int nOldest = -1;
      for (std::set<int>::iterator it = vNew.begin(); it != vNew.end(); it++)
      {
          if (nI == n[0] || nI == n[1] || nI == n[2] || nI == n[3])
          {
              assert(nOldest == -1 || mapInfo.count(*it) == 1);
              if (nOldest == -1 || mapInfo[*it].nTime < mapInfo[nOldest].nTime)
                  nOldest = *it;
          }
          nI++;
      }
      assert(mapInfo.count(nOldest) == 1);
      CAddrInfo &info = mapInfo[nOldest];
      if (--info.nRefCount == 0) 
      {
          SwapRandom(info.nRandomPos, vRandom.size()-1);
          vRandom.pop_back();
          mapAddr.erase(info);
          mapInfo.erase(nOldest);
          nNew--;
      }
      vNew.erase(nOldest);
  
      return 1;
  }
  
  void CAddrMan::MakeTried(CAddrInfo& info, int nId, int nOrigin)
  {
      assert(vvNew[nOrigin].count(nId) == 1);
  
      // remove the entry from all new buckets
      for (std::vector<std::set<int> >::iterator it = vvNew.begin(); it != vvNew.end(); it++)
      {
          if ((*it).erase(nId))
              info.nRefCount--;
      }
      nNew--;
  
      assert(info.nRefCount == 0);
  
      // what tried bucket to move the entry to
      int nKBucket = info.GetTriedBucket(nKey);
      std::vector<int> &vTried = vvTried[nKBucket];
  
      // first check whether there is place to just add it
      if (vTried.size() < ADDRMAN_TRIED_BUCKET_SIZE)
      {
          vTried.push_back(nId);
          nTried++;
          info.fInTried = true;
          return;
      }
  
      // otherwise, find an item to evict
      int nPos = SelectTried(nKBucket);
  
      // find which new bucket it belongs to
      assert(mapInfo.count(vTried[nPos]) == 1);
      int nUBucket = mapInfo[vTried[nPos]].GetNewBucket(nKey);
      std::set<int> &vNew = vvNew[nUBucket];
  
      // remove the to-be-replaced tried entry from the tried set
      CAddrInfo& inNDCld = mapInfo[vTried[nPos]];
      inNDCld.fInTried = false;
      inNDCld.nRefCount = 1;
      // do not update nTried, as we are going to move something else there immediately
  
      // check whether there is place in that one, 
      if (vNew.size() < ADDRMAN_NEW_BUCKET_SIZE)
      {
          // if so, move it back there
          vNew.insert(vTried[nPos]);
      } else {
          // otherwise, move it to the new bucket nId came from (there is certainly place there)
          vvNew[nOrigin].insert(vTried[nPos]);
      }
      nNew++;
  
      vTried[nPos] = nId;
      // we just overwrote an entry in vTried; no need to update nTried
      info.fInTried = true;
      return;
  }
  
  void CAddrMan::Good_(const CService &addr, int64 nTime)
  {
  //    printf("Good: addr=%s\n", addr.ToString().c_str());
  
      int nId;
      CAddrInfo *pinfo = Find(addr, &nId);
  
      // if not found, bail out
      if (!pinfo)
          return;
  
      CAddrInfo &info = *pinfo;
  
      // check whether we are talking about the exact same CService (including same port)
      if (info != addr)
          return;
  
      // update info
      info.nLastSuccess = nTime;
      info.nLastTry = nTime;
      info.nTime = nTime;
      info.nAttempts = 0;
  
      // if it is already in the tried set, don't do anything else
      if (info.fInTried)
          return;
  
      // find a bucket it is in now
      int nRnd = GetRandInt(vvNew.size());
      int nUBucket = -1;
      for (unsigned int n = 0; n < vvNew.size(); n++)
      {
          int nB = (n+nRnd) % vvNew.size();
          std::set<int> &vNew = vvNew[nB];
          if (vNew.count(nId))
          {
              nUBucket = nB;
              break;
          }
      }
  
      // if no bucket is found, something bad happened;
      // TODO: maybe re-add the node, but for now, just bail out
      if (nUBucket == -1) return;
  
      printf("Moving %s to tried\n", addr.ToString().c_str());
  
      // move nId to the tried tables
      MakeTried(info, nId, nUBucket);
  }
  
  bool CAddrMan::Add_(const CAddress &addr, const CNetAddr& source, int64 nTimePenalty)
  {
      if (!addr.IsRoutable())
          return false;
  
      bool fNew = false;
      int nId;
      CAddrInfo *pinfo = Find(addr, &nId);
  
      if (pinfo)
      {
          // periodically update nTime
          bool fCurrentlyOnline = (GetAdjustedTime() - addr.nTime < 24 * 60 * 60);
          int64 nUpdateInterval = (fCurrentlyOnline ? 60 * 60 : 24 * 60 * 60);
          if (addr.nTime && (!pinfo->nTime || pinfo->nTime < addr.nTime - nUpdateInterval - nTimePenalty))
              pinfo->nTime = max((int64)0, addr.nTime - nTimePenalty);
  
          // add services
          pinfo->nServices |= addr.nServices;
  
          // do not update if no new information is present
          if (!addr.nTime || (pinfo->nTime && addr.nTime <= pinfo->nTime))
              return false;
  
          // do not update if the entry was already in the "tried" table
          if (pinfo->fInTried)
              return false;
  
          // do not update if the max reference count is reached
          if (pinfo->nRefCount == ADDRMAN_NEW_BUCKETS_PER_ADDRESS)
              return false;
  
          // stochastic test: previous nRefCount == N: 2^N times harder to increase it
          int nFactor = 1;
          for (int n=0; n<pinfo->nRefCount; n++)
              nFactor *= 2;
          if (nFactor > 1 && (GetRandInt(nFactor) != 0))
              return false;
      } else {
          pinfo = Create(addr, source, &nId);
          pinfo->nTime = max((int64)0, (int64)pinfo->nTime - nTimePenalty);
  //        printf("Added %s [nTime=%fhr]\n", pinfo->ToString().c_str(), (GetAdjustedTime() - pinfo->nTime) / 3600.0);
          nNew++;
          fNew = true;
      }
  
      int nUBucket = pinfo->GetNewBucket(nKey, source);
      std::set<int> &vNew = vvNew[nUBucket];
      if (!vNew.count(nId))
      {
          pinfo->nRefCount++;
          if (vNew.size() == ADDRMAN_NEW_BUCKET_SIZE)
              ShrinkNew(nUBucket);
          vvNew[nUBucket].insert(nId);
      }
      return fNew;
  }
  
  void CAddrMan::Attempt_(const CService &addr, int64 nTime)
  {
      CAddrInfo *pinfo = Find(addr);
  
      // if not found, bail out
      if (!pinfo)
          return;
  
      CAddrInfo &info = *pinfo;
  
      // check whether we are talking about the exact same CService (including same port)
      if (info != addr)
          return;
  
      // update info
      info.nLastTry = nTime;
      info.nAttempts++;
  }
  
  CAddress CAddrMan::Select_(int nUnkBias)
  {
      if (size() == 0)
          return CAddress();
  
      double nCorTried = sqrt(nTried) * (100.0 - nUnkBias);
      double nCorNew = sqrt(nNew) * nUnkBias;
      if ((nCorTried + nCorNew)*GetRandInt(1<<30)/(1<<30) < nCorTried)
      {
          // use a tried node
          double fChanceFactor = 1.0;
          while(1)
          {
              int nKBucket = GetRandInt(vvTried.size());
              std::vector<int> &vTried = vvTried[nKBucket];
              if (vTried.size() == 0) continue;
              int nPos = GetRandInt(vTried.size());
              assert(mapInfo.count(vTried[nPos]) == 1);
              CAddrInfo &info = mapInfo[vTried[nPos]];
              if (GetRandInt(1<<30) < fChanceFactor*info.GetChance()*(1<<30))
                  return info;
              fChanceFactor *= 1.2;
          }
      } else {
          // use an new node
          double fChanceFactor = 1.0;
          while(1)
          {
              int nUBucket = GetRandInt(vvNew.size());
              std::set<int> &vNew = vvNew[nUBucket];
              if (vNew.size() == 0) continue;
              int nPos = GetRandInt(vNew.size());
              std::set<int>::iterator it = vNew.begin();
              while (nPos--)
                  it++;
              assert(mapInfo.count(*it) == 1);
              CAddrInfo &info = mapInfo[*it];
              if (GetRandInt(1<<30) < fChanceFactor*info.GetChance()*(1<<30))
                  return info;
              fChanceFactor *= 1.2;
          }
      }
  }
  
  #ifdef DEBUG_ADDRMAN
  int CAddrMan::Check_()
  {
      std::set<int> setTried;
      std::map<int, int> mapNew;
  
      if (vRandom.size() != nTried + nNew) return -7;
  
      for (std::map<int, CAddrInfo>::iterator it = mapInfo.begin(); it != mapInfo.end(); it++)
      {
          int n = (*it).first;
          CAddrInfo &info = (*it).second;
          if (info.fInTried)
          {
  
              if (!info.nLastSuccess) return -1;
              if (info.nRefCount) return -2;
              setTried.insert(n);
          } else {
              if (info.nRefCount < 0 || info.nRefCount > ADDRMAN_NEW_BUCKETS_PER_ADDRESS) return -3;
              if (!info.nRefCount) return -4;
              mapNew[n] = info.nRefCount;
          }
          if (mapAddr[info] != n) return -5;
          if (info.nRandomPos<0 || info.nRandomPos>=vRandom.size() || vRandom[info.nRandomPos] != n) return -14;
          if (info.nLastTry < 0) return -6;
          if (info.nLastSuccess < 0) return -8;
      }
  
      if (setTried.size() != nTried) return -9;
      if (mapNew.size() != nNew) return -10;
  
      for (int n=0; n<vvTried.size(); n++)
      {
          std::vector<int> &vTried = vvTried[n];
          for (std::vector<int>::iterator it = vTried.begin(); it != vTried.end(); it++)
          {
              if (!setTried.count(*it)) return -11;
              setTried.erase(*it);
          }
      }
  
      for (int n=0; n<vvNew.size(); n++)
      {
          std::set<int> &vNew = vvNew[n];
          for (std::set<int>::iterator it = vNew.begin(); it != vNew.end(); it++)
          {
              if (!mapNew.count(*it)) return -12;
              if (--mapNew[*it] == 0)
                  mapNew.erase(*it);
          }
      }
  
      if (setTried.size()) return -13;
      if (mapNew.size()) return -15;
  
      return 0;
  }
  #endif
  
  void CAddrMan::GetAddr_(std::vector<CAddress> &vAddr)
  {
      int nNodes = ADDRMAN_GETADDR_MAX_PCT*vRandom.size()/100;
      if (nNodes > ADDRMAN_GETADDR_MAX)
          nNodes = ADDRMAN_GETADDR_MAX;
  
      // perform a random shuffle over the first nNodes elements of vRandom (selecting from all)
      for (int n = 0; n<nNodes; n++)
      {
          int nRndPos = GetRandInt(vRandom.size() - n) + n;
          SwapRandom(n, nRndPos);
          assert(mapInfo.count(vRandom[n]) == 1);
          vAddr.push_back(mapInfo[vRandom[n]]);
      }
  }
  
  void CAddrMan::Connected_(const CService &addr, int64 nTime)
  {
      CAddrInfo *pinfo = Find(addr);
  
      // if not found, bail out
      if (!pinfo)
          return;
  
      CAddrInfo &info = *pinfo;
  
      // check whether we are talking about the exact same CService (including same port)
      if (info != addr)
          return;
  
      // update info
      int64 nUpdateInterval = 20 * 60;
      if (nTime - info.nTime > nUpdateInterval)
          info.nTime = nTime;
  }
  