User:Shimmy/Variable-length quantity

See the main code base on Variable-length quantity.

<lang csharp>namespace Vlq {

 using System;
 using System.IO;

 public static class VariableLengthQuantity
 {
   /// <summary>
   /// Reads a 7-bit encoded variable-length quantity from binary and return it as integer.
   /// </summary>
   /// <returns></returns>
   public uint ReadVariableLengthQuantity(BinaryReader reader)
   {
     var index = 0;
     uint buffer = 0;
     byte current;
     do
     {
       if (index++ == 8)
         throw new FormatException("Could not read variable-length quantity from provided stream.");

       buffer <<= 7;

       current = reader.ReadByte();
       buffer |= (current & 0x7FU);
     } while ((current & 0x80) != 0);

     return buffer;
   }

   /// <summary>
   /// Writes the specified integer as a 7-bit encoded variable-length quantity.
   /// </summary>
   /// <param name="integer"></param>
   public void WriteVariableLengthQuantity(BinaryWriter writer, ulong integer)
   {
     if (integer > Math.Pow(2, 56))
       throw new OverflowException("Integer exceeds max value.");

     var index = 3;
     var significantBitReached = false;
     var mask = 0x7fUL << (index * 7);
     while (index >= 0)
     {
       var buffer = (mask & integer);
       if (buffer > 0 || significantBitReached)
       {
         significantBitReached = true;
         buffer >>= index * 7;
         if (index > 0)
           buffer |= 0x80;
         writer.Write((byte)buffer);
       }
       mask >>= 7;
       index--;
     }

     if (!significantBitReached && index < 0)
       writer.Write(new byte());
   }
 }

}</lang>