src/checkpoints.cpp

   1 // Copyright (c) 2011 The Bitcoin developers
   2 // Copyright (c) 2011-2012 The PPCoin developers
   3 // Distributed under the MIT/X11 software license, see the accompanying
   4 // file license.txt or http://www.opensource.org/licenses/mit-license.php.
   5
   6 #include <boost/assign/list_of.hpp> // for 'map_list_of()'
   7 #include <boost/foreach.hpp>
   8
   9 #include "headers.h"
  10 #include "checkpoints.h"
  11
  12 namespace Checkpoints
  13 {
  14     typedef std::map<int, uint256> MapCheckpoints;   // hardened checkpoints
  15
  16     //
  17     // What makes a good checkpoint block?
  18     // + Is surrounded by blocks with reasonable timestamps
  19     //   (no blocks before with a timestamp after, none after with
  20     //    timestamp before)
  21     // + Contains no strange transactions
  22     //
  23     static MapCheckpoints mapCheckpoints =
  24         boost::assign::map_list_of
  25         ( 0, hashGenesisBlock )
  26         ; // ppcoin: no checkpoint yet; to be created in future releases
  27
  28     bool CheckHardened(int nHeight, const uint256& hash)
  29     {
  30         if (fTestNet) return true; // Testnet has no checkpoints
  31
  32         MapCheckpoints::const_iterator i = mapCheckpoints.find(nHeight);
  33         if (i == mapCheckpoints.end()) return true;
  34         return hash == i->second;
  35     }
  36
  37     int GetTotalBlocksEstimate()
  38     {
  39         if (fTestNet) return 0;
  40
  41         return mapCheckpoints.rbegin()->first;
  42     }
  43
  44     CBlockIndex* GetLastCheckpoint(const std::map<uint256, CBlockIndex*>& mapBlockIndex)
  45     {
  46         if (fTestNet) return NULL;
  47
  48         int64 nResult;
  49         BOOST_REVERSE_FOREACH(const MapCheckpoints::value_type& i, mapCheckpoints)
  50         {
  51             const uint256& hash = i.second;
  52             std::map<uint256, CBlockIndex*>::const_iterator t = mapBlockIndex.find(hash);
  53             if (t != mapBlockIndex.end())
  54                 return t->second;
  55         }
  56         return NULL;
  57     }
  58
  59     // ppcoin: synchronized checkpoint (centrally broadcasted)
  60     uint256 hashSyncCheckpoint;
  61     CCriticalSection cs_hashSyncCheckpoint;
  62
  63     bool AcceptNewSyncCheckpoint(uint256 hashCheckpoint)
  64     {
  65     }
  66
  67     bool CSyncCheckpoint::ProcessSyncCheckpoint()
  68     {
  69         if (!CheckSignature())
  70             return false;
  71
  72         CRITICAL_BLOCK(cs_hashSyncCheckpoint)
  73             hashSyncCheckpoint = this->hashCheckpoint;
  74     }
  75
  76     // ppcoin: automatic checkpoint (represented by height of checkpoint)
  77     int nAutoCheckpoint = 0;
  78     int nBranchPoint = 0;    // branch point to alternative branch
  79
  80     // ppcoin: check automatic checkpoint
  81     // To pass the check:
  82     //   - All ancestors (including the block itself) have block index already
  83     //   - The immediate ancestor in main chain must not have height less than
  84     //     checkpoint height
  85     bool CheckAuto(const CBlockIndex *pindex)
  86     {
  87         while (pindex)
  88         {
  89             if (pindex->IsInMainChain())
  90             {
  91                 if (pindex->nHeight >= nAutoCheckpoint)
  92                     return true;
  93                 else
  94                 {
  95                     nBranchPoint = pindex->nHeight;
  96                     return error("Checkpoints: new block on alternative branch at height=%d before auto checkpoint at height=%d", pindex->nHeight, nAutoCheckpoint);
  97                 }
  98             }
  99             else
 100                 pindex = pindex->pprev;
 101         }
 102         return error("Checkpoints: failed to find any ancestor on main chain for the new block - internal error");
 103     }
 104
 105     // ppcoin: get next chain checkpoint
 106     int GetNextChainCheckpoint(const CBlockIndex *pindexLast)
 107     {
 108         CBigNum bnTarget;
 109         CBigNum bnTargetMax = 0;  // max target of all blocks since checkpoint
 110         CBigNum bnTargetMin = 0;  // min target of all candidate checkpoints
 111         int nMinTargetHeight = 0; // min target height of candidate checkpoints
 112         int nCheckpointMin = 0;   // minimum candidate checkpoint
 113         int nCheckpointMax = 0;   // maximum candidate checkpoint
 114         int nDepth = pindexLast->nHeight - pindexLast->nCheckpoint;
 115         const CBlockIndex *pindex = pindexLast;
 116         while (nDepth >= 0 && pindex)
 117         {
 118             bnTarget.SetCompact(pindex->nBits);
 119             if (bnTarget > bnTargetMax)
 120                 bnTargetMax = bnTarget;
 121             if (nCheckpointMax > 0 && bnTarget < bnTargetMin)
 122             {
 123                 bnTargetMin = bnTarget;
 124                 nMinTargetHeight = pindex->nHeight;
 125             }
 126             if (nCheckpointMax == 0 && pindexLast->GetBlockTime() - pindex->GetBlockTime() > AUTO_CHECKPOINT_MIN_SPAN)
 127             {
 128                 nCheckpointMax = pindex->nHeight;
 129                 bnTargetMin.SetCompact(pindex->nBits);
 130                 nMinTargetHeight = pindex->nHeight;
 131             }
 132             if (pindexLast->GetBlockTime() - pindex->GetBlockTime() < AUTO_CHECKPOINT_MAX_SPAN)
 133                 nCheckpointMin = pindex->nHeight;
 134             pindex = pindex->pprev;
 135             nDepth--;
 136         }
 137
 138         assert (nDepth == -1);  // arrive at chain checkpoint now
 139
 140         printf("Checkpoints: min=%d max=%d tminheight=%d tmin=0x%08x tmax=0x%08x\n",
 141             nCheckpointMin, nCheckpointMax, nMinTargetHeight,
 142             bnTargetMin.GetCompact(), bnTargetMax.GetCompact());
 143         if (nCheckpointMax == 0) // checkpoint stays if max candidate not found
 144             return pindexLast->nCheckpoint;
 145
 146         if (bnTargetMin * 100 > bnTargetMax * 90)
 147             return nCheckpointMax;
 148         if (bnTarget * 100 > bnTargetMax * 90)
 149             return nMinTargetHeight;
 150         else
 151             return nCheckpointMin;
 152     }
 153
 154     // ppcoin: get next auto checkpoint from the new chain checkpoint
 155     int GetNextAutoCheckpoint(int nCheckpoint)
 156     {
 157         return (std::max(nAutoCheckpoint, nCheckpoint));
 158     }
 159
 160     // ppcoin: advance to next automatic checkpoint
 161     void AdvanceAutoCheckpoint(int nCheckpoint)
 162     {
 163         nAutoCheckpoint = GetNextAutoCheckpoint(nCheckpoint);
 164         printf("Checkpoints: auto checkpoint now at height=%d\n", nAutoCheckpoint);
 165     }
 166
 167     // ppcoin: reset auto checkpoint
 168     bool ResetAutoCheckpoint(int nCheckpoint)
 169     {
 170         if (nCheckpoint <= 0 || nCheckpoint > nBestHeight)
 171             return error("ResetAutoCheckpoint() : new checkpoint invalid");
 172         if (nCheckpoint >= nAutoCheckpoint)
 173             return error("ResetAutoCheckpoint() : new checkpoint not earlier than current auto checkpoint");
 174         CTxDB txdb;
 175         txdb.TxnBegin();
 176         if (!txdb.WriteAutoCheckpoint(nCheckpoint, true))
 177             return error("ResetAutoCheckpoint() : database write failed");
 178         if (!txdb.TxnCommit())
 179             return error("ResetAutoCheckpoint() : database commit failed");
 180         nAutoCheckpoint = nCheckpoint;
 181         nBranchPoint = 0;  // clear branch point
 182
 183         // clear ban list to accept alternative branches
 184         CRITICAL_BLOCK(cs_vNodes)
 185         {
 186             BOOST_FOREACH(CNode* pnode, vNodes)
 187                 pnode->ClearBanned();
 188         }
 189
 190         return true;
 191     }
 192 }