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
  62     bool AcceptNewSyncCheckpoint(uint256 hashCheckpoint)
  63     {
  64     }
  65
  66     // ppcoin: automatic checkpoint (represented by height of checkpoint)
  67     int nAutoCheckpoint = 0;
  68     int nBranchPoint = 0;    // branch point to alternative branch
  69
  70     // ppcoin: check automatic checkpoint
  71     // To pass the check:
  72     //   - All ancestors (including the block itself) have block index already
  73     //   - The immediate ancestor in main chain must not have height less than
  74     //     checkpoint height
  75     bool CheckAuto(const CBlockIndex *pindex)
  76     {
  77         while (pindex)
  78         {
  79             if (pindex->IsInMainChain())
  80             {
  81                 if (pindex->nHeight >= nAutoCheckpoint)
  82                     return true;
  83                 else
  84                 {
  85                     nBranchPoint = pindex->nHeight;
  86                     return error("Checkpoints: new block on alternative branch at height=%d before auto checkpoint at height=%d", pindex->nHeight, nAutoCheckpoint);
  87                 }
  88             }
  89             else
  90                 pindex = pindex->pprev;
  91         }
  92         return error("Checkpoints: failed to find any ancestor on main chain for the new block - internal error");
  93     }
  94
  95     // ppcoin: get next chain checkpoint
  96     int GetNextChainCheckpoint(const CBlockIndex *pindexLast)
  97     {
  98         CBigNum bnTarget;
  99         CBigNum bnTargetMax = 0;  // max target of all blocks since checkpoint
 100         CBigNum bnTargetMin = 0;  // min target of all candidate checkpoints
 101         int nMinTargetHeight = 0; // min target height of candidate checkpoints
 102         int nCheckpointMin = 0;   // minimum candidate checkpoint
 103         int nCheckpointMax = 0;   // maximum candidate checkpoint
 104         int nDepth = pindexLast->nHeight - pindexLast->nCheckpoint;
 105         const CBlockIndex *pindex = pindexLast;
 106         while (nDepth >= 0 && pindex)
 107         {
 108             bnTarget.SetCompact(pindex->nBits);
 109             if (bnTarget > bnTargetMax)
 110                 bnTargetMax = bnTarget;
 111             if (nCheckpointMax > 0 && bnTarget < bnTargetMin)
 112             {
 113                 bnTargetMin = bnTarget;
 114                 nMinTargetHeight = pindex->nHeight;
 115             }
 116             if (nCheckpointMax == 0 && pindexLast->GetBlockTime() - pindex->GetBlockTime() > AUTO_CHECKPOINT_MIN_SPAN)
 117             {
 118                 nCheckpointMax = pindex->nHeight;
 119                 bnTargetMin.SetCompact(pindex->nBits);
 120                 nMinTargetHeight = pindex->nHeight;
 121             }
 122             if (pindexLast->GetBlockTime() - pindex->GetBlockTime() < AUTO_CHECKPOINT_MAX_SPAN)
 123                 nCheckpointMin = pindex->nHeight;
 124             pindex = pindex->pprev;
 125             nDepth--;
 126         }
 127
 128         assert (nDepth == -1);  // arrive at chain checkpoint now
 129
 130         printf("Checkpoints: min=%d max=%d tminheight=%d tmin=0x%08x tmax=0x%08x\n",
 131             nCheckpointMin, nCheckpointMax, nMinTargetHeight,
 132             bnTargetMin.GetCompact(), bnTargetMax.GetCompact());
 133         if (nCheckpointMax == 0) // checkpoint stays if max candidate not found
 134             return pindexLast->nCheckpoint;
 135
 136         if (bnTargetMin * 100 > bnTargetMax * 90)
 137             return nCheckpointMax;
 138         if (bnTarget * 100 > bnTargetMax * 90)
 139             return nMinTargetHeight;
 140         else
 141             return nCheckpointMin;
 142     }
 143
 144     // ppcoin: get next auto checkpoint from the new chain checkpoint
 145     int GetNextAutoCheckpoint(int nCheckpoint)
 146     {
 147         return (std::max(nAutoCheckpoint, nCheckpoint));
 148     }
 149
 150     // ppcoin: advance to next automatic checkpoint
 151     void AdvanceAutoCheckpoint(int nCheckpoint)
 152     {
 153         nAutoCheckpoint = GetNextAutoCheckpoint(nCheckpoint);
 154         printf("Checkpoints: auto checkpoint now at height=%d\n", nAutoCheckpoint);
 155     }
 156
 157     // ppcoin: reset auto checkpoint
 158     bool ResetAutoCheckpoint(int nCheckpoint)
 159     {
 160         if (nCheckpoint <= 0 || nCheckpoint > nBestHeight)
 161             return error("ResetAutoCheckpoint() : new checkpoint invalid");
 162         if (nCheckpoint >= nAutoCheckpoint)
 163             return error("ResetAutoCheckpoint() : new checkpoint not earlier than current auto checkpoint");
 164         CTxDB txdb;
 165         txdb.TxnBegin();
 166         if (!txdb.WriteAutoCheckpoint(nCheckpoint, true))
 167             return error("ResetAutoCheckpoint() : database write failed");
 168         if (!txdb.TxnCommit())
 169             return error("ResetAutoCheckpoint() : database commit failed");
 170         nAutoCheckpoint = nCheckpoint;
 171         nBranchPoint = 0;  // clear branch point
 172
 173         // clear ban list to accept alternative branches
 174         CRITICAL_BLOCK(cs_vNodes)
 175         {
 176             BOOST_FOREACH(CNode* pnode, vNodes)
 177                 pnode->ClearBanned();
 178         }
 179
 180         return true;
 181     }
 182 }