Novacoin/VarInt.cs

   1 \feff/**
   2  *  Novacoin classes library
   3  *  Copyright (C) 2015 Alex D. (balthazar.ad@gmail.com)
   4
   5  *  This program is free software: you can redistribute it and/or modify
   6  *  it under the terms of the GNU Affero General Public License as
   7  *  published by the Free Software Foundation, either version 3 of the
   8  *  License, or (at your option) any later version.
   9
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU Affero General Public License for more details.
  14
  15  *  You should have received a copy of the GNU Affero General Public License
  16  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19 using System;
  20 using System.Collections.Generic;
  21 using System.IO;
  22
  23 namespace Novacoin
  24 {
  25     public class VarInt
  26     {
  27         /// <summary>
  28         /// Encodes unsigned integer value into compact representation.
  29         ///
  30         /// See https://bitcoin.org/en/developer-reference#compactsize-unsigned-integers for additional information.
  31         /// </summary>
  32         /// <param name="n">Unsigned integer value</param>
  33         /// <returns>Byte sequence</returns>
  34         public static byte[] EncodeVarInt(ulong n)
  35         {
  36             var resultBytes = new List<byte>();
  37
  38             if (n <= 0xfc)
  39             {
  40                 // Values up to 0xfc are stored directly without any prefix
  41                 resultBytes.Add((byte)n);
  42             }
  43             else
  44             {
  45                 byte prefix;
  46                 byte[] valueBytes;
  47
  48                 if (n <= ushort.MaxValue)
  49                 {
  50                     // ushort flag
  51                     prefix = 0xfd;
  52                     valueBytes = BitConverter.GetBytes((ushort)n);
  53                 }
  54                 else if (n <= uint.MaxValue)
  55                 {
  56                     // uint flag
  57                     prefix = 0xfe;
  58                     valueBytes = BitConverter.GetBytes((uint)n);
  59                 }
  60                 else
  61                 {
  62                     // ulong flag
  63                     prefix = 0xff;
  64                     valueBytes = BitConverter.GetBytes(n);
  65                 }
  66
  67                 resultBytes.Add(prefix);
  68                 resultBytes.AddRange(valueBytes);
  69             }
  70
  71             return resultBytes.ToArray();
  72         }
  73
  74         /// <summary>
  75         /// Encodes integer value into compact representation.
  76         ///
  77         /// See https://bitcoin.org/en/developer-reference#compactsize-unsigned-integers for additional information.
  78         /// </summary>
  79         /// <param name="n">Integer value</param>
  80         /// <returns>Byte sequence</returns>
  81         public static byte[] EncodeVarInt(long n)
  82         {
  83             return EncodeVarInt((ulong)n);
  84         }
  85
  86         public static int GetEncodedSize(long n)
  87         {
  88             if (n <= 0xfc)
  89             {
  90                 return 1;
  91             }
  92             else if (n <= ushort.MaxValue)
  93             {
  94                 return 3;
  95             }
  96             else if (n <= uint.MaxValue)
  97             {
  98                 return 5;
  99             }
 100             else
 101             {
 102                 return 9;
 103             }
 104         }
 105
 106         /// <summary>
 107         /// Decodes integer value from compact representation
 108         ///
 109         /// See https://bitcoin.org/en/developer-reference#compactsize-unsigned-integers for additional information.
 110         /// </summary>
 111         /// <param name="bytes">Byte sequence</param>
 112         /// <returns>Integer value</returns>
 113         public static ulong DecodeVarInt(byte[] bytes)
 114         {
 115             var prefix = bytes[0];
 116             var bytesArray = new byte[bytes.Length - 1];
 117
 118             bytes.CopyTo(bytesArray, 1);  // Get rid of prefix
 119
 120             switch (prefix)
 121             {
 122                 case 0xfd: // ushort flag
 123                     return BitConverter.ToUInt16(bytesArray, 0);
 124                 case 0xfe: // uint flag
 125                     return BitConverter.ToUInt32(bytesArray, 0);
 126                 case 0xff: // ulong flag
 127                     return BitConverter.ToUInt64(bytesArray, 0);
 128                 default:
 129                     return prefix;
 130             }
 131         }
 132
 133         public static ulong ReadVarInt(ref BinaryReader reader)
 134         {
 135             byte prefix = reader.ReadByte();
 136
 137             switch (prefix)
 138             {
 139                 case 0xfd: // ushort
 140                     return reader.ReadUInt16();
 141                 case 0xfe: // uint
 142                     return reader.ReadUInt32();
 143                 case 0xff: // ulong
 144                     return reader.ReadUInt64();
 145                 default:
 146                     return prefix;
 147             }
 148         }
 149
 150     }
 151 }