GetCoinAge
[NovacoinLibrary.git] / Novacoin / CTransaction.cs
index 091b442..e0630aa 100644 (file)
 using System;
 using System.Text;
 using System.Collections.Generic;
+using System.IO;
+using System.Diagnostics.Contracts;
+using System.Numerics;
 
 namespace Novacoin
 {
+    [Serializable]
+    public class TransactionConstructorException : Exception
+    {
+        public TransactionConstructorException()
+        {
+        }
+
+        public TransactionConstructorException(string message)
+                : base(message)
+        {
+        }
+
+        public TransactionConstructorException(string message, Exception inner)
+                : base(message, inner)
+        {
+        }
+    }
+
     /// <summary>
-    /// Represents the transaction. Any transaction must provide one input and one output at least.
+    /// Represents the transaction.
     /// </summary>
     public class CTransaction
     {
         /// <summary>
+        /// One cent = 10000 satoshis.
+        /// </summary>
+        public const ulong nCent = 10000;
+
+        /// <summary>
+        /// One coin = 1000000 satoshis.
+        /// </summary>
+        public const ulong nCoin = 1000000;
+        
+        /// <summary>
+        /// Sanity checking threshold.
+        /// </summary>
+        public const ulong nMaxMoney = 2000000000 * nCoin;
+
+        public const ulong nMinTxFee = nCent / 10;
+        public const ulong nMinRelayTxFee = nCent / 50;
+        public const ulong nMinTxoutAmount = nCent / 100;        
+
+        /// <summary>
+        /// Maximum transaction size is 250Kb
+        /// </summary>
+        public const uint nMaxTxSize = 250000;
+
+        public enum MinFeeMode
+        {
+            GMF_BLOCK,
+            GMF_RELAY,
+            GMF_SEND,
+        }
+
+        /// <summary>
         /// Version of transaction schema.
         /// </summary>
-        public uint nVersion = 1;
+        public uint nVersion;
 
         /// <summary>
         /// Transaction timestamp.
         /// </summary>
-        public uint nTime = 0;
+        public uint nTime;
 
         /// <summary>
         /// Array of transaction inputs
@@ -50,7 +102,7 @@ namespace Novacoin
         /// <summary>
         /// Block height or timestamp when transaction is final
         /// </summary>
-        public uint nLockTime = 0;
+        public uint nLockTime;
 
         /// <summary>
         /// Initialize an empty instance
@@ -60,8 +112,11 @@ namespace Novacoin
             // Initialize empty input and output arrays. Please note that such 
             // configuration is not valid for real transaction, you have to supply 
             // at least one input and one output.
+            nVersion = 1;
+            nTime = 0;
             vin = new CTxIn[0];
             vout = new CTxOut[0];
+            nLockTime = 0;
         }
 
         /// <summary>
@@ -90,48 +145,221 @@ namespace Novacoin
             nLockTime = tx.nLockTime;
         }
 
+        /// <summary>
+        /// Attempts to execute all transaction scripts and validate the results.
+        /// </summary>
+        /// <returns>Checking result.</returns>
+        public bool VerifyScripts()
+        {
+            if (IsCoinBase)
+            {
+                return true;
+            }
+
+            TxOutItem txOutCursor = null;
+            for (int i = 0; i < vin.Length; i++)
+            {
+                var outpoint = vin[i].prevout;
+
+                if (!CBlockStore.Instance.GetTxOutCursor(outpoint, ref txOutCursor))
+                    return false;
+
+                if (!ScriptCode.VerifyScript(vin[i].scriptSig, txOutCursor.scriptPubKey, this, i, (int)scriptflag.SCRIPT_VERIFY_P2SH, 0))
+                    return false;
+            }
+
+            return true;
+        }
 
         /// <summary>
-        /// Parse byte sequence and initialize new instance of CTransaction
+        /// Calculate amount of signature operations without trying to properly evaluate P2SH scripts.
         /// </summary>
-        /// <param name="txBytes">Byte sequence</param>
-               public CTransaction(IList<byte> txBytes)
+        public uint LegacySigOpCount
         {
-            var wBytes = new ByteQueue(txBytes);
+            get
+            {
+                uint nSigOps = 0;
+                foreach (var txin in vin)
+                {
+                    nSigOps += txin.scriptSig.GetSigOpCount(false);
+                }
+                foreach (var txout in vout)
+                {
+                    nSigOps += txout.scriptPubKey.GetSigOpCount(false);
+                }
 
-            nVersion = BitConverter.ToUInt32(wBytes.Get(4), 0);
-            nTime = BitConverter.ToUInt32(wBytes.Get(4), 0);
+                return nSigOps;
+            }
+        }
 
-            int nInputs = (int)(int)wBytes.GetVarInt();
-            vin = new CTxIn[nInputs];
+        /// <summary>
+        /// Basic sanity checkings
+        /// </summary>
+        /// <returns>Checking result</returns>
+        public bool CheckTransaction()
+        {
+            if (Size > nMaxTxSize || vin.Length == 0 || vout.Length == 0)
+            {
+                return false;
+            }
 
-            for (int nCurrentInput = 0; nCurrentInput < nInputs; nCurrentInput++)
+            // Check for empty or overflow output values
+            ulong nValueOut = 0;
+            for (int i = 0; i < vout.Length; i++)
             {
-                // Fill inputs array
-                vin[nCurrentInput] = new CTxIn();
-                
-                vin[nCurrentInput].prevout = new COutPoint(wBytes.Get(36));
+                CTxOut txout = vout[i];
+                if (txout.IsEmpty && !IsCoinBase && !IsCoinStake)
+                {
+                    // Empty outputs aren't allowed for user transactions.
+                    return false;
+                }
 
-                int nScriptSigLen = (int)wBytes.GetVarInt();
-                vin[nCurrentInput].scriptSig = new CScript(wBytes.Get(nScriptSigLen));
+                nValueOut += txout.nValue;
+                if (!MoneyRange(nValueOut))
+                {
+                    return false;
+                }
+            }
+
+            // Check for duplicate inputs
+            var InOutPoints = new List<COutPoint>();
+            foreach (var txin in vin)
+            {
+                if (InOutPoints.IndexOf(txin.prevout) != -1)
+                {
+                    // Duplicate input.
+                    return false;
+                }
+                InOutPoints.Add(txin.prevout);
+            }
 
-                vin[nCurrentInput].nSequence = BitConverter.ToUInt32(wBytes.Get(4), 0);
+            if (IsCoinBase)
+            {
+                if (vin[0].scriptSig.Size < 2 || vin[0].scriptSig.Size > 100)
+                {
+                    // Script size is invalid
+                    return false;
+                }
+            }
+            else
+            {
+                foreach (var txin in vin)
+                {
+                    if (txin.prevout.IsNull)
+                    {
+                        // Null input in non-coinbase transaction.
+                        return false;
+                    }
+                }
             }
 
-            int nOutputs = (int)wBytes.GetVarInt();
-            vout = new CTxOut[nOutputs];
+            return true;
+        }
 
-            for (int nCurrentOutput = 0; nCurrentOutput < nOutputs; nCurrentOutput++)
+        public bool IsFinal(uint nBlockHeight = 0, uint nBlockTime = 0)
+        {
+            // Time based nLockTime
+            if (nLockTime == 0)
+            {
+                return true;
+            }
+            if (nBlockHeight == 0)
+            {
+                nBlockHeight = uint.MaxValue; // TODO: stupid stub here, should be best height instead.
+            }
+            if (nBlockTime == 0)
+            {
+                nBlockTime = NetInfo.GetAdjustedTime();
+            }
+            if (nLockTime < (nLockTime < NetInfo.nLockTimeThreshold ? nBlockHeight : nBlockTime))
+            {
+                return true;
+            }
+            foreach (var txin in vin)
+            {
+                if (!txin.IsFinal)
+                {
+                    return false;
+                }
+            }
+            return true;
+        }
+
+        /// <summary>
+        /// Parse byte sequence and initialize new instance of CTransaction
+        /// </summary>
+        /// <param name="txBytes">Byte sequence</param>
+        public CTransaction(byte[] txBytes)
+        {
+            try
             {
-                // Fill outputs array
-                vout[nCurrentOutput] = new CTxOut();
-                vout[nCurrentOutput].nValue = BitConverter.ToInt64(wBytes.Get(8), 0);
+                var stream = new MemoryStream(txBytes);
+                var reader = new BinaryReader(stream);
+
+                nVersion = reader.ReadUInt32();
+                nTime = reader.ReadUInt32();
+
+                int nInputs = (int)VarInt.ReadVarInt(ref reader);
+                vin = new CTxIn[nInputs];
+
+                for (int nCurrentInput = 0; nCurrentInput < nInputs; nCurrentInput++)
+                {
+                    // Fill inputs array
+                    vin[nCurrentInput] = new CTxIn();
+
+                    vin[nCurrentInput].prevout = new COutPoint(reader.ReadBytes(36));
+
+                    int nScriptSigLen = (int)VarInt.ReadVarInt(ref reader);
+                    vin[nCurrentInput].scriptSig = new CScript(reader.ReadBytes(nScriptSigLen));
+
+                    vin[nCurrentInput].nSequence = reader.ReadUInt32();
+                }
+
+                int nOutputs = (int)VarInt.ReadVarInt(ref reader);
+                vout = new CTxOut[nOutputs];
+
+                for (int nCurrentOutput = 0; nCurrentOutput < nOutputs; nCurrentOutput++)
+                {
+                    // Fill outputs array
+                    vout[nCurrentOutput] = new CTxOut();
+                    vout[nCurrentOutput].nValue = reader.ReadUInt64();
 
-                int nScriptPKLen = (int)wBytes.GetVarInt();
-                vout[nCurrentOutput].scriptPubKey = new CScript(wBytes.Get(nScriptPKLen));
+                    int nScriptPKLen = (int)VarInt.ReadVarInt(ref reader);
+                    vout[nCurrentOutput].scriptPubKey = new CScript(reader.ReadBytes(nScriptPKLen));
+                }
+
+                nLockTime = reader.ReadUInt32();
+            }
+            catch (Exception e)
+            {
+                throw new TransactionConstructorException("Deserialization failed", e);
             }
+        }
+
+        /// <summary>
+        /// Serialized size
+        /// </summary>
+        public uint Size
+        {
+            get
+            {
+                uint nSize = 12; // nVersion, nTime, nLockLime
+
+                nSize += VarInt.GetEncodedSize(vin.Length);
+                nSize += VarInt.GetEncodedSize(vout.Length);
 
-            nLockTime = BitConverter.ToUInt32(wBytes.Get(4), 0);
+                foreach (var input in vin)
+                {
+                    nSize += input.Size;
+                }
+
+                foreach (var output in vout)
+                {
+                    nSize += output.Size;
+                }
+
+                return nSize;
+            }
         }
 
         /// <summary>
@@ -139,30 +367,38 @@ namespace Novacoin
         /// </summary>
         /// <param name="wTxBytes">Bytes sequence</param>
         /// <returns>Transactions array</returns>
-        public static CTransaction[] ReadTransactionsList(ref ByteQueue wTxBytes)
+        internal static CTransaction[] ReadTransactionsList(ref BinaryReader reader)
         {
-            // Read amount of transactions
-            int nTransactions = (int)wTxBytes.GetVarInt();
-            var tx = new CTransaction[nTransactions];
-
-            for (int nTx = 0; nTx < nTransactions; nTx++)
+            try
             {
-                // Fill the transactions array
-                tx[nTx] = new CTransaction();
+                // Read amount of transactions
+                int nTransactions = (int)VarInt.ReadVarInt(ref reader);
+                var tx = new CTransaction[nTransactions];
+
+                for (int nTx = 0; nTx < nTransactions; nTx++)
+                {
+                    // Fill the transactions array
+                    tx[nTx] = new CTransaction();
 
-                tx[nTx].nVersion = BitConverter.ToUInt32(wTxBytes.Get(4), 0);
-                tx[nTx].nTime = BitConverter.ToUInt32(wTxBytes.Get(4), 0);
+                    tx[nTx].nVersion = reader.ReadUInt32();
+                    tx[nTx].nTime = reader.ReadUInt32();
 
-                // Inputs array
-                tx[nTx].vin = CTxIn.ReadTxInList(ref wTxBytes);
+                    // Inputs array
+                    tx[nTx].vin = CTxIn.ReadTxInList(ref reader);
 
-                // outputs array
-                tx[nTx].vout = CTxOut.ReadTxOutList(ref wTxBytes);
+                    // outputs array
+                    tx[nTx].vout = CTxOut.ReadTxOutList(ref reader);
 
-                tx[nTx].nLockTime = BitConverter.ToUInt32(wTxBytes.Get(4), 0);
-            }
+                    tx[nTx].nLockTime = reader.ReadUInt32();
+                }
+
+                return tx;
 
-            return tx;
+            }
+            catch (Exception e)
+            {
+                throw new TransactionConstructorException("Deserialization failed", e);
+            }
         }
 
         public bool IsCoinBase
@@ -181,84 +417,57 @@ namespace Novacoin
         /// <summary>
         /// Transaction hash
         /// </summary>
-        public Hash256 Hash
+        public uint256 Hash
         {
-            get { return Hash256.Compute256(Bytes); }
+            get { return CryptoUtils.ComputeHash256(this); }
         }
 
         /// <summary>
-        /// A sequence of bytes, which corresponds to the current state of CTransaction.
+        /// Amount of novacoins spent by this transaction.
         /// </summary>
-        public byte[] Bytes
+        public ulong nValueOut
         {
             get
             {
-                var resultBytes = new List<byte>();
-
-                // Typical transaction example:
-                //
-                // 01000000 -- version
-                // 78b4c953 -- timestamp
-                // 06       -- amount of txins
-                // 340d96b77ec4ee9d42b31cadc2fab911e48d48c36274d516f226d5e85bbc512c -- txin hash
-                // 01000000 -- txin outnumber
-                // 6b       -- txin scriptSig length
-                // 483045022100c8df1fc17b6ea1355a39b92146ec67b3b53565e636e028010d3a8a87f6f805f202203888b9b74df03c3960773f2a81b2dfd1efb08bb036a8f3600bd24d5ed694cd5a0121030dd13e6d3c63fa10cc0b6bf968fbbfcb9a988b333813b1f22d04fa60e344bc4c -- txin scriptSig
-                // ffffffff -- txin nSequence
-                // 364c640420de8fa77313475970bf09ce4d0b1f8eabb8f1d6ea49d90c85b202ee -- txin hash
-                // 01000000 -- txin outnumber
-                // 6b       -- txin scriptSig length
-                // 483045022100b651bf3a6835d714d2c990c742136d769258d0170c9aac24803b986050a8655b0220623651077ff14b0a9d61e30e30f2c15352f70491096f0ec655ae1c79a44e53aa0121030dd13e6d3c63fa10cc0b6bf968fbbfcb9a988b333813b1f22d04fa60e344bc4c -- txin scriptSig
-                // ffffffff -- txin nSequence
-                // 7adbd5f2e521f567bfea2cb63e65d55e66c83563fe253464b75184a5e462043d -- txin hash
-                // 00000000 -- txin outnumber
-                // 6a       -- txin scriptSig length
-                // 4730440220183609f2b995993acc9df241aff722d48b9a731b0cd376212934565723ed81f00220737e7ce75ef39bdc061d0dcdba3ee24e43b899696a7c96803cee0a79e1f78ecb0121030dd13e6d3c63fa10cc0b6bf968fbbfcb9a988b333813b1f22d04fa60e344bc4c -- txin scriptSig
-                // ffffffff -- txin nSequence
-                // 999eb03e00a41c2f9fde8865a554ceebbc48d30f4c8ba22dd88da8c9b46fa920 -- txin hash
-                // 03000000 -- txin outnumber
-                // 6b       -- txin scriptSig length
-                // 483045022100ec1ab104ef086ba79b0f2611ebf1bfdd22a7a1020f6630fa1c6707546626e0db022056093d4048a999392185ccc735ef736a5497bd68f60b42e6c0c93ba770b54d010121030dd13e6d3c63fa10cc0b6bf968fbbfcb9a988b333813b1f22d04fa60e344bc4c -- txin scriptSig
-                // ffffffff -- txin nSequence
-                // c0543b86be257ddd85b014a76718a70fab9eaa3c477460e4ca187094d86f369c -- txin hash
-                // 05000000 -- txin outnumber
-                // 69       -- txin scriptSig length
-                // 463043021f24275c72f952043174daf01d7f713f878625f0522124a3cab48a0a2e12604202201b47742e6697b0ebdd1e4ba49c74baf142a0228ad0e0ee847488994c9dce78470121030dd13e6d3c63fa10cc0b6bf968fbbfcb9a988b333813b1f22d04fa60e344bc4c -- txin scriptSig
-                // ffffffff -- txin nSequence
-                // e1793d4519147782293dd1db6d90e461265d91db2cc6889c37209394d42ad10d -- txin hash
-                // 05000000 -- txin outnumber
-                // 6a       -- txin scriptSig length
-                // 473044022018a0c3d73b2765d75380614ab36ee8e3c937080894a19166128b1e3357b208fb0220233c9609985f535547381431526867ad0255ec4969afe5c360544992ed6b3ed60121030dd13e6d3c63fa10cc0b6bf968fbbfcb9a988b333813b1f22d04fa60e344bc4c -- txin scriptSig
-                // ffffffff -- txin nSequence
-                // 02 -- amount of txouts
-                // e542000000000000 -- txout value
-                // 19 -- scriptPubKey length
-                // 76a91457d84c814b14bd86bf32f106b733baa693db7dc788ac -- scriptPubKey
-                // 409c000000000000 -- txout value
-                // 19 -- scriptPubKey length
-                // 76a91408c8768d5d6bf7c1d9609da4e766c3f1752247b188ac -- scriptPubKey
-                // 00000000 -- lock time
-
-                resultBytes.AddRange(BitConverter.GetBytes(nVersion));
-                resultBytes.AddRange(BitConverter.GetBytes(nTime));
-                resultBytes.AddRange(VarInt.EncodeVarInt(vin.LongLength));
-
-                foreach (var input in vin)
+                ulong nValueOut = 0;
+                foreach (var txout in vout)
                 {
-                    resultBytes.AddRange(input.Bytes);
+                    nValueOut += txout.nValue;
+                    Contract.Assert(MoneyRange(txout.nValue) && MoneyRange(nValueOut));
                 }
+                return nValueOut;
+            }
+        }
 
-                resultBytes.AddRange(VarInt.EncodeVarInt(vout.LongLength));
+        /// <summary>
+        /// A sequence of bytes, which corresponds to the current state of CTransaction.
+        /// </summary>
+        public static implicit operator byte[] (CTransaction tx)
+        {
+            var stream = new MemoryStream();
+            var writer = new BinaryWriter(stream);
 
-                foreach (var output in vout)
-                {
-                    resultBytes.AddRange(output.Bytes);
-                }
+            writer.Write(tx.nVersion);
+            writer.Write(tx.nTime);
+            writer.Write(VarInt.EncodeVarInt(tx.vin.LongLength));
 
-                resultBytes.AddRange(BitConverter.GetBytes(nLockTime));
+            foreach (var input in tx.vin)
+            {
+                writer.Write(input);
+            }
+
+            writer.Write(VarInt.EncodeVarInt(tx.vout.LongLength));
 
-                return resultBytes.ToArray();
+            foreach (var output in tx.vout)
+            {
+                writer.Write(output);
             }
+
+            writer.Write(tx.nLockTime);
+            var resultBytes = stream.ToArray();
+            writer.Close();
+
+            return resultBytes;
         }
 
         public override string ToString()
@@ -269,17 +478,210 @@ namespace Novacoin
 
             foreach (var txin in vin)
             {
-                sb.AppendFormat(" {0},\n", txin.ToString());
+                sb.AppendFormat(" {0},\n", txin);
             }
 
             foreach (var txout in vout)
             {
-                sb.AppendFormat(" {0},\n", txout.ToString());
+                sb.AppendFormat(" {0},\n", txout);
             }
 
             sb.AppendFormat("\nnLockTime={0}\n)", nLockTime);
 
             return sb.ToString();
         }
-       }
+
+        public static bool MoneyRange(ulong nValue) { return (nValue <= nMaxMoney); }
+
+        /// <summary>
+        /// Get total sigops.
+        /// </summary>
+        /// <param name="inputs">Inputs map.</param>
+        /// <returns>Amount of sigops.</returns>
+        public uint GetP2SHSigOpCount(ref Dictionary<COutPoint, TxOutItem> inputs)
+        {
+            if (IsCoinBase)
+            {
+                return 0;
+            }
+
+            uint nSigOps = 0;
+            for (var i = 0; i < vin.Length; i++)
+            {
+                var prevout = GetOutputFor(vin[i], ref inputs);
+                if (prevout.scriptPubKey.IsPayToScriptHash)
+                {
+                    nSigOps += prevout.scriptPubKey.GetSigOpCount(vin[i].scriptSig);
+                }
+            }
+
+            return nSigOps;
+        }
+
+        /// <summary>
+        /// Get sum of inputs spent by this transaction.
+        /// </summary>
+        /// <param name="inputs">Reference to innputs map.</param>
+        /// <returns>Sum of inputs.</returns>
+        public ulong GetValueIn(ref Dictionary<COutPoint, TxOutItem> inputs)
+        {
+            if (IsCoinBase)
+            {
+                return 0;
+            }
+
+            ulong nResult = 0;
+            for (int i = 0; i < vin.Length; i++)
+            {
+                nResult += GetOutputFor(vin[i], ref inputs).nValue;
+            }
+
+            return nResult;
+        }
+
+        /// <summary>
+        /// Helper method to find output in the map.
+        /// </summary>
+        /// <param name="input">Transaction input.</param>
+        /// <param name="inputs">eference to inuts map.</param>
+        /// <returns>Parent output.</returns>
+        private CTxOut GetOutputFor(CTxIn input, ref Dictionary<COutPoint, TxOutItem> inputs)
+        {
+            if (!inputs.ContainsKey(input.prevout))
+            {
+                throw new Exception("No such input");
+            }
+
+            var outItem = inputs[input.prevout];
+
+            return new CTxOut(outItem.nValue, outItem.scriptPubKey);
+        }
+
+        /// <summary>
+        /// Calculate coin*age. 
+        /// 
+        /// Note, only those coins meeting minimum age requirement counts.
+        /// </summary>
+        /// <param name="inputs">Inputs set.</param>
+        /// <param name="nCoinAge">Coin age calculation result.</param>
+        /// <returns>Result</returns>
+        public bool GetCoinAge(ref Dictionary<COutPoint, TxOutItem> inputs, out ulong nCoinAge)
+        {
+            BigInteger bnCentSecond = 0;  // coin age in the unit of cent-seconds
+            nCoinAge = 0;
+
+            if (IsCoinBase)
+            {
+                // Nothing spent by coinbase, coinage is always zero.
+                return true;
+            }
+
+            for( var i = 0; i<vin.Length; i++)
+            {
+                var prevout = vin[i].prevout;
+                Contract.Assert(inputs.ContainsKey(prevout));
+                var input = inputs[prevout];
+
+                CBlockStoreItem parentBlockCursor;
+                var merkleItem = CBlockStore.Instance.GetMerkleCursor(input, out parentBlockCursor);
+
+                if (merkleItem == null)
+                {
+                    return false; // Unable to find merkle node
+                }
+
+                if (nTime < merkleItem.nTime)
+                {
+                    return false;  // Transaction timestamp violation
+                }
+
+                if (parentBlockCursor.nTime + StakeModifier.nStakeMinAge > nTime)
+                {
+                    continue; // only count coins meeting min age requirement
+                }
+
+                ulong nValueIn = input.nValue;
+                bnCentSecond += new BigInteger(nValueIn) * (nTime - merkleItem.nTime) / nCent;
+            }
+
+            BigInteger bnCoinDay = bnCentSecond * nCent / nCoin / (24 * 60 * 60);
+            nCoinAge = (ulong)bnCoinDay;
+
+            return true;
+        }
+
+        public ulong GetMinFee(uint nBlockSize, bool fAllowFree, MinFeeMode mode)
+        {
+            ulong nMinTxFee = CTransaction.nMinTxFee, nMinRelayTxFee = CTransaction.nMinRelayTxFee;
+            uint nBytes = Size;
+
+            if (IsCoinStake)
+            {
+                // Enforce 0.01 as minimum fee for old approach or coinstake
+                nMinTxFee = nCent;
+                nMinRelayTxFee = nCent;
+
+                if (nTime < NetInfo.nStakeValidationSwitchTime)
+                {
+                    // Enforce zero size for compatibility with old blocks.
+                    nBytes = 0;
+                }
+            }
+
+            // Base fee is either nMinTxFee or nMinRelayTxFee
+            ulong nBaseFee = (mode == MinFeeMode.GMF_RELAY) ? nMinRelayTxFee : nMinTxFee;
+
+            uint nNewBlockSize = nBlockSize + nBytes;
+            ulong nMinFee = (1 + (ulong)nBytes / 1000) * nBaseFee;
+
+            if (fAllowFree)
+            {
+                if (nBlockSize == 1)
+                {
+                    // Transactions under 1K are free
+                    if (nBytes < 1000)
+                        nMinFee = 0;
+                }
+                else
+                {
+                    // Free transaction area
+                    if (nNewBlockSize < 27000)
+                        nMinFee = 0;
+                }
+            }
+
+            // To limit dust spam, require additional MIN_TX_FEE/MIN_RELAY_TX_FEE for
+            //    each non empty output which is less than 0.01
+            //
+            // It's safe to ignore empty outputs here, because these inputs are allowed
+            //     only for coinbase and coinstake transactions.
+            foreach (var txout in vout)
+            {
+                if (txout.nValue < nCent && !txout.IsEmpty)
+                {
+                    nMinFee += nBaseFee;
+                }
+            }
+
+            var nMaxBlockSizeGen = CBlock.nMaxBlockSize / 2;
+
+            // Raise the price as the block approaches full
+            if (nBlockSize != 1 && nNewBlockSize >= nMaxBlockSizeGen / 2)
+            {
+                if (nNewBlockSize >= nMaxBlockSizeGen)
+                {
+                    return nMaxMoney;
+                }
+
+                nMinFee *= nMaxBlockSizeGen / (nMaxBlockSizeGen - nNewBlockSize);
+            }
+
+            if (!MoneyRange(nMinFee))
+            {
+                nMinFee = nMaxMoney;
+            }
+
+            return nMinFee;
+        }
+    }
 }