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.Linq;
  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 IList<byte> EncodeVarInt(ulong n)
  35         {
  36             List<byte> 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;
  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 IList<byte> EncodeVarInt(long n)
  82         {
  83             return EncodeVarInt((ulong)n);
  84         }
  85
  86         /// <summary>
  87         /// Decodes integer value from compact representation
  88         ///
  89         /// See https://bitcoin.org/en/developer-reference#compactsize-unsigned-integers for additional information.
  90         /// </summary>
  91         /// <param name="bytes">Byte sequence</param>
  92         /// <returns>Integer value</returns>
  93         public static ulong DecodeVarInt(IList<byte> bytes)
  94         {
  95             byte prefix = bytes[0];
  96
  97             bytes.RemoveAt(0); // Remove prefix
  98
  99             byte[] bytesArray = bytes.ToArray();
 100
 101             switch (prefix)
 102             {
 103                 case 0xfd: // ushort flag
 104                     return BitConverter.ToUInt16(bytesArray, 0);
 105                 case 0xfe: // uint flag
 106                     return BitConverter.ToUInt32(bytesArray, 0);
 107                 case 0xff: // ulong flag
 108                     return BitConverter.ToUInt64(bytesArray, 0);
 109                 default:
 110                     return prefix;
 111             }
 112         }
 113     }
 114 }