ConnectInputs + stubs for GetCoinAge, GetMinFee and GetProofOfStakeReward.
[NovacoinLibrary.git] / Novacoin / CBlockStore.cs
index 28706a5..97ce54e 100644 (file)
-\feffusing System;
+\feff/**
+*  Novacoin classes library
+*  Copyright (C) 2015 Alex D. (balthazar.ad@gmail.com)
+
+*  This program is free software: you can redistribute it and/or modify
+*  it under the terms of the GNU Affero General Public License as
+*  published by the Free Software Foundation, either version 3 of the
+*  License, or (at your option) any later version.
+
+*  This program is distributed in the hope that it will be useful,
+*  but WITHOUT ANY WARRANTY; without even the implied warranty of
+*  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*  GNU Affero General Public License for more details.
+
+*  You should have received a copy of the GNU Affero General Public License
+*  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+
+using System;
 using System.IO;
-using System.Linq;
 using System.Collections.Concurrent;
 
 using SQLite.Net;
-using SQLite.Net.Attributes;
 using SQLite.Net.Interop;
 using SQLite.Net.Platform.Generic;
-using SQLiteNetExtensions.Attributes;
 using System.Collections.Generic;
+using System.Text;
+using System.Diagnostics.Contracts;
+using System.Linq;
 
 namespace Novacoin
 {
-    /// <summary>
-    /// Block headers table
-    /// </summary>
-    [Table("BlockStorage")]
-    class CBlockStoreItem
+    public class CBlockStore : IDisposable
     {
-        /// <summary>
-        /// Item ID in the database
-        /// </summary>
-        [PrimaryKey, AutoIncrement]
-        public int ItemID { get; set; }
+        public const uint nMagicNumber = 0xe5e9e8e4;
 
-        /// <summary>
-        /// PBKDF2+Salsa20 of block hash
-        /// </summary>
-        [Unique]
-        public byte[] Hash { get; set; }
+        private bool disposed = false;
+        private object LockObj = new object();
 
         /// <summary>
-        /// Version of block schema
+        /// SQLite connection object.
         /// </summary>
-        public uint nVersion { get; set; }
+        private SQLiteConnection dbConn;
 
         /// <summary>
-        /// Previous block hash.
+        /// Current SQLite platform
         /// </summary>
-        public byte[] prevHash { get; set; }
+        private ISQLitePlatform dbPlatform;
 
         /// <summary>
-        /// Merkle root hash.
+        /// Block file.
         /// </summary>
-        public byte[] merkleRoot { get; set; }
+        private string strBlockFile;
 
         /// <summary>
-        /// Block timestamp.
+        /// Index database file.
         /// </summary>
-        public uint nTime { get; set; }
+        private string strDbFile;
 
         /// <summary>
-        /// Compressed difficulty representation.
+        /// Map of block tree nodes.
+        /// 
+        /// blockHash => CBlockStoreItem
         /// </summary>
-        public uint nBits { get; set; }
+        private ConcurrentDictionary<uint256, CBlockStoreItem> blockMap = new ConcurrentDictionary<uint256, CBlockStoreItem>();
 
         /// <summary>
-        /// Nonce counter.
+        /// Orphaned blocks map.
         /// </summary>
-        public uint nNonce { get; set; }
+        private ConcurrentDictionary<uint256, CBlock> orphanMap = new ConcurrentDictionary<uint256, CBlock>();
+        private ConcurrentDictionary<uint256, CBlock> orphanMapByPrev = new ConcurrentDictionary<uint256, CBlock>();
 
         /// <summary>
-        /// Block type flags
+        /// Unconfirmed transactions.
+        /// 
+        /// TxID => Transaction
         /// </summary>
-        public BlockType BlockTypeFlag { get; set; }
+        private ConcurrentDictionary<uint256, CTransaction> mapUnconfirmedTx = new ConcurrentDictionary<uint256, CTransaction>();
 
         /// <summary>
-        /// Stake modifier
+        /// Map of the proof-of-stake hashes. This is necessary for stake duplication checks.
         /// </summary>
-        public long nStakeModifier { get; set; }
+        private ConcurrentDictionary<uint256, uint256> mapProofOfStake = new ConcurrentDictionary<uint256, uint256>();
+
+
+        private ConcurrentDictionary<COutPoint, uint> mapStakeSeen = new ConcurrentDictionary<COutPoint, uint>();
+        private ConcurrentDictionary<COutPoint, uint> mapStakeSeenOrphan = new ConcurrentDictionary<COutPoint, uint>();
+
 
         /// <summary>
-        /// Stake entropy bit
+        /// Copy of chain state object.
         /// </summary>
-        public byte nEntropyBit { get; set; }
+        private ChainState ChainParams;
 
         /// <summary>
-        /// Next block hash
+        /// Cursor which is pointing us to the end of best chain.
         /// </summary>
-        public byte[] NextHash { get; set; }
+        private CBlockStoreItem bestBlockCursor = null;
 
         /// <summary>
-        /// Block height
+        /// Cursor which is always pointing us to genesis block.
         /// </summary>
-        public uint nHeight { get; set; }
+        private CBlockStoreItem genesisBlockCursor = null;
 
         /// <summary>
-        /// Block position in file
+        /// Current and the only instance of block storage manager. Should be a property with private setter though it's enough for the beginning.
         /// </summary>
-        public long nBlockPos { get; set; }
+        public static CBlockStore Instance = null;
 
         /// <summary>
-        /// Block size in bytes
+        /// Block file stream with read/write access
         /// </summary>
-        public int nBlockSize { get; set; }
+        private Stream fStreamReadWrite;
+        private uint nTimeBestReceived;
+        private int nTransactionsUpdated;
 
         /// <summary>
-        /// Fill database item with data from given block header.
+        /// Init the block storage manager.
         /// </summary>
-        /// <param name="header">Block header</param>
-        /// <returns>Header hash</returns>
-        public ScryptHash256 FillHeader(CBlockHeader header)
+        /// <param name="IndexDB">Path to index database</param>
+        /// <param name="BlockFile">Path to block file</param>
+        public CBlockStore(string IndexDB = "blockstore.dat", string BlockFile = "blk0001.dat")
         {
-            ScryptHash256 _hash;
-            Hash = _hash = header.Hash;
+            strDbFile = IndexDB;
+            strBlockFile = BlockFile;
 
-            nVersion = header.nVersion;
-            prevHash = header.prevHash;
-            merkleRoot = header.merkleRoot;
-            nTime = header.nTime;
-            nBits = header.nBits;
-            nNonce = header.nNonce;
+            bool firstInit = !File.Exists(strDbFile);
+            dbPlatform = new SQLitePlatformGeneric();
+            dbConn = new SQLiteConnection(dbPlatform, strDbFile);
 
-            return _hash;
-        }
+            fStreamReadWrite = File.Open(strBlockFile, FileMode.OpenOrCreate, FileAccess.ReadWrite);
 
-        /// <summary>
-        /// Reconstruct block header from item data.
-        /// </summary>
-        public CBlockHeader BlockHeader
-        {
-            get
+            Instance = this;
+
+            if (firstInit)
+            {
+                lock (LockObj)
+                {
+                    // Create tables
+                    dbConn.CreateTable<CBlockStoreItem>(CreateFlags.AutoIncPK);
+                    dbConn.CreateTable<CMerkleNode>(CreateFlags.AutoIncPK);
+                    dbConn.CreateTable<TxOutItem>(CreateFlags.ImplicitPK);
+                    dbConn.CreateTable<ChainState>(CreateFlags.AutoIncPK);
+
+                    ChainParams = new ChainState()
+                    {
+                        nBestChainTrust = 0,
+                        nBestHeight = 0,
+                        nHashBestChain = 0
+                    };
+
+                    dbConn.Insert(ChainParams);
+
+                    var genesisBlock = new CBlock(
+                        Interop.HexToArray(
+                            "01000000" + // nVersion=1
+                            "0000000000000000000000000000000000000000000000000000000000000000" + // prevhash is zero
+                            "7b0502ad2f9f675528183f83d6385794fbcaa914e6d385c6cb1d866a3b3bb34c" + // merkle root
+                            "398e1151" + // nTime=1360105017
+                            "ffff0f1e" + // nBits=0x1e0fffff
+                            "d3091800" + // nNonce=1575379
+                            "01" +       // nTxCount=1
+                            "01000000" + // nVersion=1
+                            "398e1151" + // nTime=1360105017
+                            "01" +       // nInputs=1
+                            "0000000000000000000000000000000000000000000000000000000000000000" + // input txid is zero
+                            "ffffffff" + // n=uint.maxValue
+                            "4d" +       // scriptSigLen=77
+                            "04ffff001d020f274468747470733a2f2f626974636f696e74616c6b2e6f72672f696e6465782e7068703f746f7069633d3133343137392e6d736731353032313936236d736731353032313936" + // scriptSig
+                            "ffffffff" + // nSequence=uint.maxValue
+                            "01" +       // nOutputs=1
+                            "0000000000000000" + // nValue=0
+                            "00" +       // scriptPubkeyLen=0
+                            "00000000" + // nLockTime=0
+                            "00"         // sigLen=0
+                    ));
+
+                    // Write block to file.
+                    var itemTemplate = new CBlockStoreItem()
+                    {
+                        nHeight = 0
+                    };
+
+                    itemTemplate.FillHeader(genesisBlock.header);
+
+                    if (!AddItemToIndex(ref itemTemplate, ref genesisBlock))
+                    {
+                        throw new Exception("Unable to write genesis block");
+                    }
+                }
+            }
+            else
             {
-                CBlockHeader header = new CBlockHeader();
+                var blockTreeItems = dbConn.Query<CBlockStoreItem>("select * from [BlockStorage] order by [ItemId] asc");
+
+                // Init list of block items
+                foreach (var item in blockTreeItems)
+                {
+                    blockMap.TryAdd(item.Hash, item);
 
-                header.nVersion = nVersion;
-                header.prevHash = new ScryptHash256(prevHash);
-                header.merkleRoot = new Hash256(merkleRoot);
-                header.nTime = nTime;
-                header.nBits = nBits;
-                header.nNonce = nNonce;
+                    if (item.IsProofOfStake)
+                    {
+                        // build mapStakeSeen
+                        mapStakeSeen.TryAdd(item.prevoutStake, item.nStakeTime);
+                    }
+                }
 
-                return header;
+                // Load data about the top node.
+                ChainParams = dbConn.Table<ChainState>().First();
             }
         }
 
-        /// <summary>
-        /// Read block from file.
-        /// </summary>
-        /// <param name="reader">Stream with read access.</param>
-        /// <param name="reader">CBlock reference.</param>
-        /// <returns>Result</returns>
-        public bool ReadFromFile(ref Stream reader, out CBlock block)
+        public bool GetTxOutCursor(COutPoint outpoint, ref TxOutItem txOutCursor)
         {
-            var buffer = new byte[nBlockSize];
-            block = null;
+            var queryResults = dbConn.Query<TxOutItem>("select o.* from [Outputs] o left join [MerkleNodes] m on (m.nMerkleNodeID = o.nMerkleNodeID) where m.[TransactionHash] = ?", (byte[])outpoint.hash);
 
-            try
+            if (queryResults.Count == 1)
             {
-                reader.Seek(nBlockPos, SeekOrigin.Begin);
+                txOutCursor = queryResults[0];
 
-                if (nBlockSize != reader.Read(buffer, 0, nBlockSize))
-                {
-                    return false;
-                }
+                return true;
+            }
 
-                block = new CBlock(buffer);
+            // Tx not found
 
+            return false;
+        }
+        
+        public bool FetchInputs(CTransaction tx, ref Dictionary<COutPoint, TxOutItem> queued, ref Dictionary<COutPoint, TxOutItem> inputs, bool IsBlock, out bool Invalid)
+        {
+            Invalid = false;
+
+            if (tx.IsCoinBase)
+            {
+                // Coinbase transactions have no inputs to fetch.
                 return true;
             }
-            catch (IOException)
+
+            StringBuilder queryBuilder = new StringBuilder();
+
+            queryBuilder.Append("select o.*, m.[TransactionHash] from [Outputs] o left join [MerkleNodes] m on (m.[nMerkleNodeID] = o.[nMerkleNodeID]) where ");
+
+            for (var i = 0; i < tx.vin.Length; i++)
             {
-                // I/O error
-                return false;
+                queryBuilder.AppendFormat(" {0} (m.[TransactionHash] = x'{1}' and o.[OutputNumber] = x'{2}')",
+                    (i > 0 ? "or" : string.Empty), Interop.ToHex(tx.vin[i].prevout.hash),
+                    Interop.ToHex(VarInt.EncodeVarInt(tx.vin[i].prevout.n)
+                ));
             }
-            catch (BlockException)
+
+            var queryResults = dbConn.Query<InputsJoin>(queryBuilder.ToString());
+
+            foreach (var item in queryResults)
             {
-                // Constructor exception
-                return false;
+                if (item.IsSpent)
+                {
+                    return false; // Already spent
+                }
+
+                var inputsKey = new COutPoint(item.TransactionHash, item.nOut);
+
+                item.IsSpent = true;
+
+                // Add output data to dictionary
+                inputs.Add(inputsKey, (TxOutItem)item);
             }
+
+            if (queryResults.Count < tx.vin.Length)
+            {
+                if (IsBlock)
+                {
+                    // It seems that some transactions are being spent in the same block.
+
+                    foreach (var txin in tx.vin)
+                    {
+                        var outPoint = txin.prevout;
+
+                        if (!queued.ContainsKey(outPoint))
+                        {
+                            return false; // No such transaction
+                        }
+
+                        // Add output data to dictionary
+                        inputs.Add(outPoint, queued[outPoint]);
+
+                        // Mark output as spent
+                        queued[outPoint].IsSpent = true;
+                    }
+                }
+                else
+                {
+                    // Unconfirmed transaction
+
+                    foreach (var txin in tx.vin)
+                    {
+                        var outPoint = txin.prevout;
+                        CTransaction txPrev;
+
+                        if (!mapUnconfirmedTx.TryGetValue(outPoint.hash, out txPrev))
+                        {
+                            return false; // No such transaction
+                        }
+
+                        if (outPoint.n > txPrev.vout.Length)
+                        {
+                            Invalid = true;
+
+                            return false; // nOut is out of range
+                        }
+
+                        // TODO: return inputs from map 
+                        throw new NotImplementedException();
+
+                    }
+
+                    return false;
+                }
+            }
+
+            return true;
         }
 
-        /// <summary>
-        /// Writes given block to file and prepares cursor object for insertion into the database.
-        /// </summary>
-        /// <param name="writer">Stream with write access.</param>
-        /// <param name="block">CBlock reference.</param>
-        /// <returns>Result</returns>
-        public bool WriteToFile(ref Stream writer, ref CBlock block)
+        private bool AddItemToIndex(ref CBlockStoreItem itemTemplate, ref CBlock block)
         {
-            try
+            uint256 blockHash = itemTemplate.Hash;
+
+            if (blockMap.ContainsKey(blockHash))
             {
-                byte[] blockBytes = block;
+                // Already have this block.
+                return false;
+            }
 
-                var magicBytes = BitConverter.GetBytes(CBlockStore.nMagicNumber);
-                var blkLenBytes = BitConverter.GetBytes(blockBytes.Length);
+            // Begin transaction
+            dbConn.BeginTransaction();
 
-                // Seek to the end and then append magic bytes there.
-                writer.Seek(0, SeekOrigin.End);
-                writer.Write(magicBytes, 0, magicBytes.Length);
+            // Compute chain trust score
+            itemTemplate.nChainTrust = (itemTemplate.prev != null ? itemTemplate.prev.nChainTrust : 0) + itemTemplate.nBlockTrust;
 
-                // Save block size and current position in the block cursor fields.
-                nBlockPos = writer.Position;
-                nBlockSize = blockBytes.Length;                
+            if (!itemTemplate.SetStakeEntropyBit(Entropy.GetStakeEntropyBit(itemTemplate.nHeight, blockHash)))
+            {
+                return false; // SetStakeEntropyBit() failed
+            }
 
-                // Write block and flush the stream.
-                writer.Write(blkLenBytes, 0, blkLenBytes.Length);
-                writer.Write(blockBytes, 0, blockBytes.Length);
-                writer.Flush();
+            // Save proof-of-stake hash value
+            if (itemTemplate.IsProofOfStake)
+            {
+                uint256 hashProofOfStake;
+                if (!GetProofOfStakeHash(blockHash, out hashProofOfStake))
+                {
+                    return false;  // hashProofOfStake not found 
+                }
+                itemTemplate.hashProofOfStake = hashProofOfStake;
+            }
 
-                return true;
+            // compute stake modifier
+            long nStakeModifier = 0;
+            bool fGeneratedStakeModifier = false;
+            if (!StakeModifier.ComputeNextStakeModifier(itemTemplate, ref nStakeModifier, ref fGeneratedStakeModifier))
+            {
+                return false;  // ComputeNextStakeModifier() failed
             }
-            catch (IOException)
+
+            itemTemplate.SetStakeModifier(nStakeModifier, fGeneratedStakeModifier);
+            itemTemplate.nStakeModifierChecksum = StakeModifier.GetStakeModifierChecksum(itemTemplate);
+
+            // TODO: verify stake modifier checkpoints
+
+            // Add to index
+            if (block.IsProofOfStake)
             {
-                // I/O error
-                return false;
+                itemTemplate.SetProofOfStake();
+
+                itemTemplate.prevoutStake = block.vtx[1].vin[0].prevout;
+                itemTemplate.nStakeTime = block.vtx[1].nTime;
             }
-            catch (Exception)
+
+            if (!itemTemplate.WriteToFile(ref fStreamReadWrite, ref block))
             {
-                // Some serialization error
                 return false;
             }
+
+            if (dbConn.Insert(itemTemplate) == 0)
+            {
+                return false; // Insert failed
+            }
+
+            // Get last RowID.
+            itemTemplate.ItemID = dbPlatform.SQLiteApi.LastInsertRowid(dbConn.Handle);
+
+            if (!blockMap.TryAdd(blockHash, itemTemplate))
+            {
+                return false; // blockMap add failed
+            }
+
+            if (itemTemplate.nChainTrust > ChainParams.nBestChainTrust)
+            {
+                // New best chain
+
+                if (!SetBestChain(ref itemTemplate))
+                {
+                    return false; // SetBestChain failed.
+                }
+            }
+
+            // Commit transaction
+            dbConn.Commit();
+
+            return true;
         }
-    }
 
-    /// <summary>
-    /// Block type.
-    /// </summary>
-    public enum BlockType
-    {
-        PROOF_OF_WORK,
-        PROOF_OF_WORK_MODIFIER,
-        PROOF_OF_STAKE,
-        PROOF_OF_STAKE_MODIFIER
-    };
-
-    /// <summary>
-    /// Transaction type.
-    /// </summary>
-    public enum TxType
-    {
-        TX_COINBASE,
-        TX_COINSTAKE,
-        TX_USER
-    }
+        private bool SetBestChain(ref CBlockStoreItem cursor)
+        {
+            uint256 hashBlock = cursor.Hash;
 
-    [Table("TransactionStorage")]
-    public class CTransactionStoreItem
-    {
-        /// <summary>
-        /// Transaction hash
-        /// </summary>
-        [PrimaryKey]
-        public byte[] TransactionHash { get; set; }
+            if (genesisBlockCursor == null && hashBlock == NetInfo.nHashGenesisBlock)
+            {
+                genesisBlockCursor = cursor;
+            }
+            else if (ChainParams.nHashBestChain == (uint256)cursor.prevHash)
+            {
+                if (!SetBestChainInner(cursor))
+                {
+                    return false;
+                }
+            }
+            else
+            {
+                // the first block in the new chain that will cause it to become the new best chain
+                var cursorIntermediate = cursor;
 
-        /// <summary>
-        /// Block hash
-        /// </summary>
-        [ForeignKey(typeof(CBlockStoreItem), Name = "Hash")]
-        public byte[] BlockHash { get; set; }
+                // list of blocks that need to be connected afterwards
+                var secondary = new List<CBlockStoreItem>();
 
-        /// <summary>
-        /// Transaction type flag
-        /// </summary>
-        public TxType txType { get; set; }
+                // Reorganize is costly in terms of db load, as it works in a single db transaction.
+                // Try to limit how much needs to be done inside
+                while (cursorIntermediate.prev != null && cursorIntermediate.prev.nChainTrust > bestBlockCursor.nChainTrust)
+                {
+                    secondary.Add(cursorIntermediate);
+                    cursorIntermediate = cursorIntermediate.prev;
+                }
 
-        /// <summary>
-        /// Tx position in file
-        /// </summary>
-        public long nTxPos { get; set; }
+                // Switch to new best branch
+                if (!Reorganize(cursorIntermediate))
+                {
+                    InvalidChainFound(cursor);
+                    return false; // reorganize failed
+                }
 
-        /// <summary>
-        /// Transaction size
-        /// </summary>
-        public int nTxSize { get; set; }
+                // Connect further blocks
+                foreach (var currentCursor in secondary)
+                {
+                    CBlock block;
+                    if (!currentCursor.ReadFromFile(ref fStreamReadWrite, out block))
+                    {
+                        // ReadFromDisk failed
+                        break;
+                    }
 
-        /// <summary>
-        /// Read transaction from file.
-        /// </summary>
-        /// <param name="reader">Stream with read access.</param>
-        /// <param name="tx">CTransaction reference.</param>
-        /// <returns>Result</returns>
-        public bool ReadFromFile(ref Stream reader, out CTransaction tx)
+                    // errors now are not fatal, we still did a reorganisation to a new chain in a valid way
+                    if (!SetBestChainInner(currentCursor))
+                    {
+                        break;
+                    }
+                }
+            }
+
+            bestBlockCursor = cursor;
+            nTimeBestReceived = Interop.GetTime();
+            nTransactionsUpdated++;
+
+            return true;
+        }
+
+        private void InvalidChainFound(CBlockStoreItem cursor)
+        {
+            throw new NotImplementedException();
+        }
+
+        private bool Reorganize(CBlockStoreItem cursorIntermediate)
         {
-            var buffer = new byte[250000]; // Max transaction size is 250kB
-            tx = null;
+            // Find the fork
+            var fork = bestBlockCursor;
+            var longer = cursorIntermediate;
 
-            try
+            while (fork.ItemID != longer.ItemID)
             {
-                reader.Seek(nTxPos, SeekOrigin.Begin); // Seek to transaction offset
+                while (longer.nHeight > fork.nHeight)
+                {
+                    if ((longer = longer.prev) == null)
+                    {
+                        return false; // longer.prev is null
+                    }
+                }
 
-                if (nTxSize != reader.Read(buffer, 0, nTxSize))
+                if (fork.ItemID == longer.ItemID)
                 {
-                    return false;
+                    break;
                 }
 
-                tx = new CTransaction(buffer);
+                if ((fork = fork.prev) == null)
+                {
+                    return false; // fork.prev is null
+                }
+            }
 
-                return true;
+            // List of what to disconnect
+            var disconnect = new List<CBlockStoreItem>();
+            for (var cursor = bestBlockCursor; cursor.ItemID != fork.ItemID; cursor = cursor.prev)
+            {
+                disconnect.Add(cursor);
             }
-            catch (IOException)
+
+            // List of what to connect
+            var connect = new List<CBlockStoreItem>();
+            for (var cursor = cursorIntermediate; cursor.ItemID != fork.ItemID; cursor = cursor.prev)
             {
-                // I/O error
-                return false;
+                connect.Add(cursor);
             }
-            catch (TransactionConstructorException)
+            connect.Reverse();
+
+            // Disconnect shorter branch
+            var txResurrect = new List<CTransaction>();
+            foreach (var blockCursor in disconnect)
             {
-                // Constructor error
-                return false;
+                CBlock block;
+                if (!blockCursor.ReadFromFile(ref fStreamReadWrite, out block))
+                {
+                    return false; // ReadFromFile for disconnect failed.
+                }
+                if (!DisconnectBlock(blockCursor, ref block))
+                {
+                    return false; // DisconnectBlock failed.
+                }
+
+                // Queue memory transactions to resurrect
+                foreach (var tx in block.vtx)
+                {
+                    if (!tx.IsCoinBase && !tx.IsCoinStake)
+                    {
+                        txResurrect.Add(tx);
+                    }
+                }
             }
-        }
-    }
 
-    public class CBlockStore : IDisposable
-    {
-        public const uint nMagicNumber = 0xe5e9e8e4;
 
-        private bool disposed = false;
-        private object LockObj = new object();
+            // Connect longer branch
+            var txDelete = new List<CTransaction>();
+            foreach (var cursor in connect)
+            {
+                CBlock block;
+                if (!cursor.ReadFromFile(ref fStreamReadWrite, out block))
+                {
+                    return false; // ReadFromDisk for connect failed
+                }
 
-        /// <summary>
-        /// SQLite connection object.
-        /// </summary>
-        private SQLiteConnection dbConn;
+                if (!ConnectBlock(cursor, ref block))
+                {
+                    // Invalid block
+                    return false; // ConnectBlock failed
+                }
 
-        /// <summary>
-        /// Block file.
-        /// </summary>
-        private string strBlockFile;
+                // Queue memory transactions to delete
+                foreach (var tx in block.vtx)
+                {
+                    txDelete.Add(tx);
+                }
+            }
 
-        /// <summary>
-        /// Index database file.
-        /// </summary>
-        private string strDbFile;
+            if (!UpdateTopChain(cursorIntermediate))
+            {
+                return false; // UpdateTopChain failed
+            }
 
-        /// <summary>
-        /// Map of block tree nodes.
-        /// </summary>
-        private ConcurrentDictionary<ScryptHash256, CBlockStoreItem> blockMap = new ConcurrentDictionary<ScryptHash256, CBlockStoreItem>();
+            // Resurrect memory transactions that were in the disconnected branch
+            foreach (var tx in txResurrect)
+            {
+                mapUnconfirmedTx.TryAdd(tx.Hash, tx);
+            }
 
-        /// <summary>
-        /// Orphaned blocks map.
-        /// </summary>
-        private ConcurrentDictionary<ScryptHash256, CBlock> orphanMap = new ConcurrentDictionary<ScryptHash256, CBlock>();
-        private ConcurrentDictionary<ScryptHash256, CBlock> orphanMapByPrev = new ConcurrentDictionary<ScryptHash256, CBlock>();
+            // Delete redundant memory transactions that are in the connected branch
+            foreach (var tx in txDelete)
+            {
+                CTransaction dummy;
+                mapUnconfirmedTx.TryRemove(tx.Hash, out dummy);
+            }
 
-        /// <summary>
-        /// Map of unspent items.
-        /// </summary>
-        private ConcurrentDictionary<Hash256, CTransactionStoreItem> txMap = new ConcurrentDictionary<Hash256, CTransactionStoreItem>();
-
-        private CBlock genesisBlock = new CBlock(
-            Interop.HexToArray(
-                "01000000" + // nVersion=1
-                "0000000000000000000000000000000000000000000000000000000000000000" + // prevhash is zero
-                "7b0502ad2f9f675528183f83d6385794fbcaa914e6d385c6cb1d866a3b3bb34c" + // merkle root
-                "398e1151" + // nTime=1360105017
-                "ffff0f1e" + // nBits=0x1e0fffff
-                "d3091800" + // nNonce=1575379
-                "01" +       // nTxCount=1
-                "01000000" + // nVersion=1
-                "398e1151" + // nTime=1360105017
-                "01" +       // nInputs=1
-                "0000000000000000000000000000000000000000000000000000000000000000" + // input txid is zero
-                "ffffffff" + // n=uint.maxValue
-                "4d" +       // scriptSigLen=77
-                "04ffff001d020f274468747470733a2f2f626974636f696e74616c6b2e6f72672f696e6465782e7068703f746f7069633d3133343137392e6d736731353032313936236d736731353032313936" + // scriptSig
-                "ffffffff" + // nSequence=uint.maxValue
-                "01" +       // nOutputs=1
-                "0000000000000000" + // nValue=0
-                "00" +       // scriptPubkeyLen=0
-                "00000000" + // nLockTime=0
-                "00"         // sigLen=0
-        ));
-
-        public static CBlockStore Instance;
+            return true; // Done
+        }
 
-        /// <summary>
-        /// Block file stream with read access
-        /// </summary>
-        private Stream reader;
+        private bool DisconnectBlock(CBlockStoreItem blockCursor, ref CBlock block)
+        {
+            throw new NotImplementedException();
+        }
 
-        /// <summary>
-        /// Block file stream with write access
-        /// </summary>
-        private Stream writer;
+        private bool SetBestChainInner(CBlockStoreItem cursor)
+        {
+            uint256 hash = cursor.Hash;
+            CBlock block;
+            if (!cursor.ReadFromFile(ref fStreamReadWrite, out block))
+            {
+                return false; // Unable to read block from file.
+            }
 
-        /// <summary>
-        /// Init the block storage manager.
-        /// </summary>
-        /// <param name="IndexDB">Path to index database</param>
-        /// <param name="BlockFile">Path to block file</param>
-        public CBlockStore(string IndexDB = "blockstore.dat", string BlockFile = "blk0001.dat")
+            // Adding to current best branch
+            if (!ConnectBlock(cursor, ref block) || !UpdateTopChain(cursor))
+            {
+                InvalidChainFound(cursor);
+                return false;
+            }
+
+            // Add to current best branch
+            cursor.prev.next = cursor;
+
+            // Delete redundant memory transactions
+            foreach (var tx in block.vtx)
+            {
+                CTransaction dummy;
+                mapUnconfirmedTx.TryRemove(tx.Hash, out dummy);
+            }
+
+            return true;
+        }
+
+        private bool ConnectBlock(CBlockStoreItem cursor, ref CBlock block, bool fJustCheck = false)
         {
-            strDbFile = IndexDB;
-            strBlockFile = BlockFile;
+            // Check it again in case a previous version let a bad block in, but skip BlockSig checking
+            if (!block.CheckBlock(!fJustCheck, !fJustCheck, false))
+            {
+                return false; // Invalid block found.
+            }
 
-            bool firstInit = !File.Exists(strDbFile);
-            dbConn = new SQLiteConnection(new SQLitePlatformGeneric(), strDbFile);
+            bool fScriptChecks = cursor.nHeight >= Checkpoints.TotalBlocksEstimate;
+            var scriptFlags = scriptflag.SCRIPT_VERIFY_NOCACHE | scriptflag.SCRIPT_VERIFY_P2SH;
 
-            var fStreamReadWrite = File.Open(strBlockFile, FileMode.OpenOrCreate, FileAccess.ReadWrite);
-            writer = new BinaryWriter(fStreamReadWrite).BaseStream;
-            reader = new BinaryReader(fStreamReadWrite).BaseStream;
+            ulong nFees = 0;
+            ulong nValueIn = 0;
+            ulong nValueOut = 0;
+            uint nSigOps = 0;
 
-            if (firstInit)
+            var queuedMerkleNodes = new Dictionary<uint256, CMerkleNode>();
+            var queued = new Dictionary<COutPoint, TxOutItem>();
+
+            for (var nTx = 0; nTx < block.vtx.Length; nTx++)
             {
-                lock (LockObj)
+                var tx = block.vtx[nTx];
+                var hashTx = tx.Hash;
+                var nTxPos = cursor.nBlockPos + block.GetTxOffset(nTx);
+
+                Dictionary<COutPoint, TxOutItem> txouts;
+                if (GetOutputs(hashTx, out txouts))
                 {
-                    // Create tables
-                    dbConn.CreateTable<CBlockStoreItem>(CreateFlags.AutoIncPK);
-                    dbConn.CreateTable<CTransactionStoreItem>(CreateFlags.ImplicitPK);
+                    // Do not allow blocks that contain transactions which 'overwrite' older transactions,
+                    // unless those are already completely spent.
+                    return false;
+                }
 
-                    // Write block to file.
-                    var itemTemplate = new CBlockStoreItem()
+                nSigOps += tx.LegacySigOpCount;
+                if (nSigOps > CBlock.nMaxSigOps)
+                {
+                    return false; // too many sigops
+                }
+
+                var inputs = new Dictionary<COutPoint, TxOutItem>();
+
+                if (tx.IsCoinBase)
+                {
+                    nValueOut += tx.nValueOut;
+                }
+                else
+                {
+                    bool Invalid;
+                    if (!FetchInputs(tx, ref queued, ref inputs, true, out Invalid))
                     {
-                        nHeight = 0
-                    };
+                        return false; // Unable to fetch some inputs.
+                    }
 
-                    itemTemplate.FillHeader(genesisBlock.header);
+                    // Add in sigops done by pay-to-script-hash inputs;
+                    // this is to prevent a "rogue miner" from creating
+                    // an incredibly-expensive-to-validate block.
+                    nSigOps += tx.GetP2SHSigOpCount(ref inputs);
+                    if (nSigOps > CBlock.nMaxSigOps)
+                    {
+                        return false; // too many sigops
+                    }
 
-                    if (!AddItemToIndex(ref itemTemplate, ref genesisBlock))
+                    ulong nTxValueIn = tx.GetValueIn(ref inputs);
+                    ulong nTxValueOut = tx.nValueOut;
+
+                    nValueIn += nTxValueIn;
+                    nValueOut += nTxValueOut;
+
+                    if (!tx.IsCoinStake)
                     {
-                        throw new Exception("Unable to write genesis block");
+                        nFees += nTxValueIn - nTxValueOut;
+                    }
+
+                    if (!ConnectInputs(tx, ref inputs, ref queued, ref cursor, true, fScriptChecks, scriptFlags))
+                    {
+                        return false;
                     }
                 }
+
+                for (var i = 0u; i < tx.vout.Length; i++)
+                {
+                    var mNode = new CMerkleNode(cursor.ItemID, nTxPos, tx);
+                    queuedMerkleNodes.Add(hashTx, mNode);
+
+                    var outKey = new COutPoint(hashTx, i);
+                    var outData = new TxOutItem();
+
+                    outData.nValue = tx.vout[i].nValue;
+                    outData.scriptPubKey = tx.vout[i].scriptPubKey;
+                    outData.nOut = i;
+
+
+                    outData.IsSpent = false;
+
+                    queued.Add(outKey, outData);
+                }
             }
-            else
+
+            if (!block.IsProofOfStake)
             {
-                var blockTreeItems = dbConn.Query<CBlockStoreItem>("select * from [BlockStorage] order by [ItemId] asc");
+                ulong nBlockReward = CBlock.GetProofOfWorkReward(cursor.nBits, nFees);
 
-                // Init list of block items
-                foreach (var item in blockTreeItems)
+                // Check coinbase reward
+                if (block.vtx[0].nValueOut > nBlockReward)
                 {
-                    blockMap.TryAdd(new ScryptHash256(item.Hash), item);
+                    return false; // coinbase reward exceeded
                 }
             }
 
-            Instance = this;
-        }
+            cursor.nMint = (long)(nValueOut - nValueIn + nFees);
+            cursor.nMoneySupply = (cursor.prev != null ? cursor.prev.nMoneySupply : 0) + (long)nValueOut - (long)nValueIn;
 
-        public bool GetTransaction(Hash256 TxID, ref CTransaction tx)
-        {
-            var QueryTx = dbConn.Query<CTransactionStoreItem>("select * from [TransactionStorage] where [TransactionHash] = ?", (byte[])TxID);
+            if (!UpdateDBCursor(ref cursor))
+            {
+                return false; // Unable to commit changes
+            }
 
-            if (QueryTx.Count == 1)
+            if (fJustCheck)
             {
-                return QueryTx[0].ReadFromFile(ref reader, out tx);
+                return true;
             }
 
-            // Tx not found
+            // Write queued transaction changes
+            var actualMerkleNodes = new Dictionary<uint256, CMerkleNode>();
+            var queuedOutpointItems = new List<TxOutItem>();
+            foreach (KeyValuePair<COutPoint, TxOutItem> outPair in queued)
+            {
+                uint256 txID = outPair.Key.hash;
+                CMerkleNode merkleNode;
 
-            return false;
+                if (actualMerkleNodes.ContainsKey(txID))
+                {
+                    merkleNode = actualMerkleNodes[txID];
+                }
+                else
+                {
+                    merkleNode = queuedMerkleNodes[txID];
+                    if (!SaveMerkleNode(ref merkleNode))
+                    {
+                        // Unable to save merkle tree cursor.
+                        return false;
+                    }
+                    actualMerkleNodes.Add(txID, merkleNode);
+                }
+
+                var outItem = outPair.Value;
+                outItem.nMerkleNodeID = merkleNode.nMerkleNodeID;
+
+                queuedOutpointItems.Add(outItem);
+            }
+
+            if (!SaveOutpoints(ref queuedOutpointItems))
+            {
+                return false; // Unable to save outpoints
+            }
+
+            return true;
         }
 
-        private bool AddItemToIndex(ref CBlockStoreItem itemTemplate, ref CBlock block)
+        /// <summary>
+        /// Insert set of outpoints
+        /// </summary>
+        /// <param name="queuedOutpointItems">List of TxOutItem objects.</param>
+        /// <returns>Result</returns>
+        private bool SaveOutpoints(ref List<TxOutItem> queuedOutpointItems)
         {
-            var blockHash = new ScryptHash256(itemTemplate.Hash);
+            return dbConn.InsertAll(queuedOutpointItems, false) != 0;
+        }
 
-            if (blockMap.ContainsKey(blockHash))
+        /// <summary>
+        /// Insert merkle node into db and set actual record id value.
+        /// </summary>
+        /// <param name="merkleNode">Merkle node object reference.</param>
+        /// <returns>Result</returns>
+        private bool SaveMerkleNode(ref CMerkleNode merkleNode)
+        {
+            if (dbConn.Insert(merkleNode) == 0)
             {
-                // Already have this block.
                 return false;
             }
 
-            // TODO: compute chain trust, set stake entropy bit, record proof-of-stake hash value
+            merkleNode.nMerkleNodeID = dbPlatform.SQLiteApi.LastInsertRowid(dbConn.Handle);
 
-            // TODO: compute stake modifier
+            return true;
+        }
 
-            // Add to index
-            itemTemplate.BlockTypeFlag = block.IsProofOfStake ? BlockType.PROOF_OF_STAKE : BlockType.PROOF_OF_WORK;
+        private bool ConnectInputs(CTransaction tx, ref Dictionary<COutPoint, TxOutItem> inputs, ref Dictionary<COutPoint, TxOutItem> queued, ref CBlockStoreItem cursorBlock, bool fBlock, bool fScriptChecks, scriptflag scriptFlags)
+        {
+            // Take over previous transactions' spent pointers
+            // fBlock is true when this is called from AcceptBlock when a new best-block is added to the blockchain
+            // fMiner is true when called from the internal bitcoin miner
+            // ... both are false when called from CTransaction::AcceptToMemoryPool
 
-            if (!itemTemplate.WriteToFile(ref writer, ref block))
+            if (!tx.IsCoinBase)
             {
-                return false;
-            }
+                ulong nValueIn = 0;
+                ulong nFees = 0;
+                for (uint i = 0; i < tx.vin.Length; i++)
+                {
+                    var prevout = tx.vin[i].prevout;
+                    Contract.Assert(inputs.ContainsKey(prevout));
+                    var input = inputs[prevout];
 
-            dbConn.Insert(itemTemplate);
+                    CBlockStoreItem parentBlockCursor;
+                    var merkleItem = GetMerkleCursor(input, out parentBlockCursor);
 
-            // We have no SetBestChain and ConnectBlock/Disconnect block yet, so adding these transactions manually.
-            for (int i = 0; i < block.vtx.Length; i++)
-            {
-                // Handle trasactions
+                    if (merkleItem == null)
+                    {
+                        return false; // Unable to find merkle node
+                    }
 
-                var nTxOffset = itemTemplate.nBlockPos + block.GetTxOffset(i);
-                TxType txnType = TxType.TX_USER;
+                    // If prev is coinbase or coinstake, check that it's matured
+                    if (merkleItem.IsCoinBase || merkleItem.IsCoinStake)
+                    {
+                        if (cursorBlock.nHeight - parentBlockCursor.nHeight < NetInfo.nGeneratedMaturity)
+                        {
+                            return false; // tried to spend non-matured generation input.
+                        }
+                    }
+
+                    // check transaction timestamp
+                    if (merkleItem.nTime > tx.nTime)
+                    {
+                        return false; // transaction timestamp earlier than input transaction
+                    }
+
+                    // Check for negative or overflow input values
+                    nValueIn += input.nValue;
+                    if (!CTransaction.MoneyRange(input.nValue) || !CTransaction.MoneyRange(nValueIn))
+                    {
+                        return false; // txin values out of range
+                    }
 
-                if (block.vtx[i].IsCoinBase)
-                {
-                    txnType = TxType.TX_COINBASE;
                 }
-                else if (block.vtx[i].IsCoinStake)
+
+                // The first loop above does all the inexpensive checks.
+                // Only if ALL inputs pass do we perform expensive ECDSA signature checks.
+                // Helps prevent CPU exhaustion attacks.
+                for (int i = 0; i < tx.vin.Length; i++)
                 {
-                    txnType = TxType.TX_COINSTAKE;
+                    var prevout = tx.vin[i].prevout;
+                    Contract.Assert(inputs.ContainsKey(prevout));
+                    var input = inputs[prevout];
+
+                    // Check for conflicts (double-spend)
+                    if (input.IsSpent)
+                    {
+                        return false;
+                    }
+
+                    // Skip ECDSA signature verification when connecting blocks (fBlock=true)
+                    // before the last blockchain checkpoint. This is safe because block merkle hashes are
+                    // still computed and checked, and any change will be caught at the next checkpoint.
+                    if (fScriptChecks)
+                    {
+                        // Verify signature
+                        if (!ScriptCode.VerifyScript(tx.vin[i].scriptSig, input.scriptPubKey, tx, i, (int)scriptflag.SCRIPT_VERIFY_P2SH, 0))
+                        {
+                            return false; // VerifyScript failed.
+                        }
+                    }
+
+                    // Mark outpoint as spent
+                    input.IsSpent = true;
+                    inputs[prevout] = input;
+
+                    // Write back
+                    if (fBlock)
+                    {
+                        queued.Add(prevout, input);
+                    }
                 }
 
-                var NewTxItem = new CTransactionStoreItem()
+                if (tx.IsCoinStake)
                 {
-                    TransactionHash = block.vtx[i].Hash,
-                    BlockHash = blockHash,
-                    nTxPos = nTxOffset,
-                    nTxSize = block.vtx[i].Size,
-                    txType = txnType
-                };
+                    // ppcoin: coin stake tx earns reward instead of paying fee
+                    ulong nCoinAge;
+                    if (!tx.GetCoinAge(ref inputs, out nCoinAge))
+                    {
+                        return false; // unable to get coin age for coinstake
+                    }
 
-                dbConn.Insert(NewTxItem);
+                    int nTxSize = (tx.nTime > NetInfo.nStakeValidationSwitchTime) ? tx.Size : 0;
+                    ulong nReward = tx.nValueOut - nValueIn;
+
+                    ulong nCalculatedReward = CBlock.GetProofOfStakeReward(nCoinAge, cursorBlock.nBits, tx.nTime) - CTransaction.GetMinFee(1, false, CTransaction.MinFeeMode.GMF_BLOCK, nTxSize) + CTransaction.nCent;
+
+                    if (nReward > nCalculatedReward)
+                    {
+                        return false; // coinstake pays too much
+                    }
+                }
+                else
+                {
+                    if (nValueIn < tx.nValueOut)
+                    {
+                        return false; // value in < value out
+                    }
+
+                    // Tally transaction fees
+                    ulong nTxFee = nValueIn - tx.nValueOut;
+                    if (nTxFee < 0)
+                    {
+                        return false; // nTxFee < 0
+                    }
+
+                    nFees += nTxFee;
+
+                    if (!CTransaction.MoneyRange(nFees))
+                    {
+                        return false; // nFees out of range
+                    }
+                }
+                
             }
 
-            return blockMap.TryAdd(blockHash, itemTemplate);
+            return true;
+        }
+
+
+        /// <summary>
+        /// Set new top node or current best chain.
+        /// </summary>
+        /// <param name="cursor"></param>
+        /// <returns></returns>
+        private bool UpdateTopChain(CBlockStoreItem cursor)
+        {
+            ChainParams.HashBestChain = cursor.Hash;
+            ChainParams.nBestChainTrust = cursor.nChainTrust;
+            ChainParams.nBestHeight = cursor.nHeight;
+
+            return dbConn.Update(ChainParams) != 0;
+        }
+
+        /// <summary>
+        /// Try to find proof-of-stake hash in the map.
+        /// </summary>
+        /// <param name="blockHash">Block hash</param>
+        /// <param name="hashProofOfStake">Proof-of-stake hash</param>
+        /// <returns>Proof-of-Stake hash value</returns>
+        private bool GetProofOfStakeHash(uint256 blockHash, out uint256 hashProofOfStake)
+        {
+            return mapProofOfStake.TryGetValue(blockHash, out hashProofOfStake);
         }
 
         public bool AcceptBlock(ref CBlock block)
         {
-            ScryptHash256 hash = block.header.Hash;
+            uint256 nHash = block.header.Hash;
 
-            if (blockMap.ContainsKey(hash))
+            if (blockMap.ContainsKey(nHash))
             {
                 // Already have this block.
                 return false;
@@ -522,7 +990,7 @@ namespace Novacoin
             uint nHeight = prevBlockCursor.nHeight + 1;
 
             // Check timestamp against prev
-            if (NetUtils.FutureDrift(block.header.nTime) < prevBlockHeader.nTime)
+            if (NetInfo.FutureDrift(block.header.nTime) < prevBlockHeader.nTime)
             {
                 // block's timestamp is too early
                 return false;
@@ -542,36 +1010,180 @@ namespace Novacoin
             // Write block to file.
             var itemTemplate = new CBlockStoreItem()
             {
-                nHeight = nHeight
+                nHeight = nHeight,
             };
 
             itemTemplate.FillHeader(block.header);
 
             if (!AddItemToIndex(ref itemTemplate, ref block))
             {
+                dbConn.Rollback();
+
                 return false;
             }
 
             return true;
         }
 
-        public bool GetBlock(ScryptHash256 blockHash, ref CBlock block)
+        /// <summary>
+        /// GEt block by hash.
+        /// </summary>
+        /// <param name="blockHash">Block hash</param>
+        /// <param name="block">Block object reference</param>
+        /// <param name="nBlockPos">Block position reference</param>
+        /// <returns>Result</returns>
+        public bool GetBlock(uint256 blockHash, ref CBlock block, ref long nBlockPos)
+        {
+            CBlockStoreItem cursor;
+
+            if (!blockMap.TryGetValue(blockHash, out cursor))
+            {
+                return false; // Unable to fetch block cursor
+            }
+
+            nBlockPos = cursor.nBlockPos;
+
+            return cursor.ReadFromFile(ref fStreamReadWrite, out block);
+        }
+
+        /// <summary>
+        /// Get block and transaction by transaction hash.
+        /// </summary>
+        /// <param name="TxID">Transaction hash</param>
+        /// <param name="block">Block reference</param>
+        /// <param name="nBlockPos">Block position reference</param>
+        /// <returns>Result of operation</returns>
+        public bool GetBlockByTransactionID(uint256 TxID, ref CBlock block, ref long nBlockPos)
         {
-            var QueryBlock = dbConn.Query<CBlockStoreItem>("select * from [BlockStorage] where [Hash] = ?", (byte[])blockHash);
+            var queryResult = dbConn.Query<CBlockStoreItem>("select b.* from [BlockStorage] b left join [MerkleNodes] m on (b.[ItemID] = m.[nParentBlockID]) where m.[TransactionHash] = ?", (byte[])TxID);
 
-            if (QueryBlock.Count == 1)
+            if (queryResult.Count == 1)
             {
-                return QueryBlock[0].ReadFromFile(ref reader, out block);
+                CBlockStoreItem blockCursor = queryResult[0];
+
+                return blockCursor.ReadFromFile(ref fStreamReadWrite, out block);
             }
 
-            // Block not found
+            // Tx not found
 
             return false;
         }
 
+        public bool GetOutputs(uint256 transactionHash, out Dictionary<COutPoint, TxOutItem> txouts, bool fUnspentOnly=true)
+        {
+            txouts = null;
+
+            var queryParams = new object[] { (byte[])transactionHash, fUnspentOnly ? OutputFlags.AVAILABLE : (OutputFlags.AVAILABLE | OutputFlags.SPENT) };
+            var queryResult = dbConn.Query<TxOutItem>("select o.* from [Outputs] o left join [MerkleNodes] m on m.[nMerkleNodeID] = o.[nMerkleNodeID] where m.[TransactionHash] = ? and outputFlags = ?", queryParams);
+
+            if (queryResult.Count != 0)
+            {
+                txouts = new Dictionary<COutPoint, TxOutItem>();
+
+                foreach (var o in queryResult)
+                {
+                    var outpointKey = new COutPoint(transactionHash, o.nOut);
+                    var outpointData = o;
+
+                    txouts.Add(outpointKey, outpointData);
+                }
+
+                // There are some unspent inputs.
+                return true;
+            }
+
+            // This transaction has been spent completely.
+            return false;
+        }
+
+        /// <summary>
+        /// Get block cursor from map.
+        /// </summary>
+        /// <param name="blockHash">block hash</param>
+        /// <returns>Cursor or null</returns>
+        public CBlockStoreItem GetMapCursor(uint256 blockHash)
+        {
+            if (blockHash == 0)
+            {
+                // Genesis block has zero prevHash and no parent.
+                return null;
+            }
+
+            CBlockStoreItem cursor = null;
+            blockMap.TryGetValue(blockHash, out cursor);
+
+            return cursor;
+        }
+
+        /// <summary>
+        /// Get merkle node cursor by output metadata.
+        /// </summary>
+        /// <param name="item">Output metadata object</param>
+        /// <returns>Merkle node cursor or null</returns>
+        public CMerkleNode GetMerkleCursor(TxOutItem item, out CBlockStoreItem blockCursor)
+        {
+            blockCursor = null;
+
+            // Trying to get cursor from the database.
+            var QueryMerkleCursor = dbConn.Query<CMerkleNode>("select * from [MerkleNodes] where [nMerkleNodeID] = ?", item.nMerkleNodeID);
+
+            if (QueryMerkleCursor.Count == 1)
+            {
+                var merkleNode = QueryMerkleCursor[0];
+
+                // Search for block
+                var results = blockMap.Where(x => x.Value.ItemID == merkleNode.nParentBlockID).Select(x => x.Value).ToArray();
+
+                blockCursor = results[0];
+            }
+
+            // Nothing found.
+            return null;
+        }
+
+        /// <summary>
+        /// Load cursor from database.
+        /// </summary>
+        /// <param name="blockHash">Block hash</param>
+        /// <returns>Block cursor object</returns>
+        public CBlockStoreItem GetDBCursor(uint256 blockHash)
+        {
+            // Trying to get cursor from the database.
+            var QueryBlockCursor = dbConn.Query<CBlockStoreItem>("select * from [BlockStorage] where [Hash] = ?", (byte[])blockHash);
+
+            if (QueryBlockCursor.Count == 1)
+            {
+                return QueryBlockCursor[0];
+            }
+
+            // Nothing found.
+            return null;
+        }
+
+        /// <summary>
+        /// Update cursor in memory and on disk.
+        /// </summary>
+        /// <param name="cursor">Block cursor</param>
+        /// <returns>Result</returns>
+        public bool UpdateMapCursor(CBlockStoreItem cursor)
+        {
+            var original = blockMap[cursor.Hash];
+            return blockMap.TryUpdate(cursor.Hash, cursor, original);
+        }
+
+        /// <summary>
+        /// Update cursor record in database.
+        /// </summary>
+        /// <param name="cursor">Block cursor object</param>
+        /// <returns>Result</returns>
+        public bool UpdateDBCursor(ref CBlockStoreItem cursor)
+        {
+            return dbConn.Update(cursor) != 0;
+        }
+
         public bool ProcessBlock(ref CBlock block)
         {
-            ScryptHash256 blockHash = block.header.Hash;
+            var blockHash = block.header.Hash;
 
             if (blockMap.ContainsKey(blockHash))
             {
@@ -587,15 +1199,33 @@ namespace Novacoin
 
             // TODO: Limited duplicity on stake and reserialization of block signature
 
-            // Preliminary checks
             if (!block.CheckBlock(true, true, true))
             {
-                return true;
+                // Preliminary checks failure.
+                return false;
             }
 
             if (block.IsProofOfStake)
             {
+                if (!block.SignatureOK)
+                {
+                    // Proof-of-Stake signature validation failure.
+                    return false;
+                }
+
                 // TODO: proof-of-stake validation
+
+                uint256 hashProofOfStake = 0, targetProofOfStake = 0;
+                if (!StakeModifier.CheckProofOfStake(block.vtx[1], block.header.nBits, ref hashProofOfStake, ref targetProofOfStake))
+                {
+                    return false; // do not error here as we expect this during initial block download
+                }
+                if (!mapProofOfStake.ContainsKey(blockHash)) 
+                {
+                    // add to mapProofOfStake
+                    mapProofOfStake.TryAdd(blockHash, hashProofOfStake);
+                }
+
             }
 
             // TODO: difficulty verification
@@ -623,12 +1253,12 @@ namespace Novacoin
             }
 
             // Recursively process any orphan blocks that depended on this one
-            var orphansQueue = new List<ScryptHash256>();
+            var orphansQueue = new List<uint256>();
             orphansQueue.Add(blockHash);
 
             for (int i = 0; i < orphansQueue.Count; i++)
             {
-                ScryptHash256 hashPrev = orphansQueue[i];
+                var hashPrev = orphansQueue[i];
 
                 foreach (var pair in orphanMap)
                 {
@@ -659,17 +1289,14 @@ namespace Novacoin
 
             var nOffset = 0L;
 
-            var buffer = new byte[1000000]; // Max block size is 1Mb
+            var buffer = new byte[CBlock.nMaxBlockSize]; // Max block size is 1Mb
             var intBuffer = new byte[4];
 
             var fStream2 = File.OpenRead(BlockFile);
-            var readerForBlocks = new BinaryReader(fStream2).BaseStream;
-
-            readerForBlocks.Seek(nOffset, SeekOrigin.Begin); // Seek to previous offset + previous block length
 
-            dbConn.BeginTransaction();
+            fStream2.Seek(nOffset, SeekOrigin.Begin); // Seek to previous offset + previous block length
 
-            while (readerForBlocks.Read(buffer, 0, 4) == 4) // Read magic number
+            while (fStream2.Read(buffer, 0, 4) == 4) // Read magic number
             {
                 var nMagic = BitConverter.ToUInt32(buffer, 0);
                 if (nMagic != 0xe5e9e8e4)
@@ -677,7 +1304,7 @@ namespace Novacoin
                     throw new Exception("Incorrect magic number.");
                 }
 
-                var nBytesRead = readerForBlocks.Read(buffer, 0, 4);
+                var nBytesRead = fStream2.Read(buffer, 0, 4);
                 if (nBytesRead != 4)
                 {
                     throw new Exception("BLKSZ EOF");
@@ -685,9 +1312,9 @@ namespace Novacoin
 
                 var nBlockSize = BitConverter.ToInt32(buffer, 0);
 
-                nOffset = readerForBlocks.Position;
+                nOffset = fStream2.Position;
 
-                nBytesRead = readerForBlocks.Read(buffer, 0, nBlockSize);
+                nBytesRead = fStream2.Read(buffer, 0, nBlockSize);
 
                 if (nBytesRead == 0 || nBytesRead != nBlockSize)
                 {
@@ -710,16 +1337,15 @@ namespace Novacoin
                 int nCount = blockMap.Count;
                 Console.WriteLine("nCount={0}, Hash={1}, Time={2}", nCount, block.header.Hash, DateTime.Now); // Commit on each 100th block
 
+                /*
                 if (nCount % 100 == 0 && nCount != 0)
                 {
                     Console.WriteLine("Commit...");
                     dbConn.Commit();
                     dbConn.BeginTransaction();
-                }
+                }*/
             }
 
-            dbConn.Commit();
-
             return true;
         }
 
@@ -742,8 +1368,7 @@ namespace Novacoin
                 {
                     // Free other state (managed objects).
 
-                    reader.Dispose();
-                    writer.Dispose();
+                    fStreamReadWrite.Dispose();
                 }
 
                 if (dbConn != null)