gistfile1.cs

public static void WriteVariableUint64(this BinaryWriter writer, UInt64 value)
        {
            for (int i = 0; i < sizeof(UInt64); i++)
            {
                byte writeByte = (byte)(value & 127);
                value >>= 7;

                if (value != 0)
                    writeByte |= 128;

                writer.Write(writeByte);

                if (value == 0)
                    return;
            }
        }

        public static UInt64 ReadVariableUint64(this BinaryReader reader)
        {
            UInt64 accumulator = 0;
            int iterations = 0;

            byte readByte;
            do
            {
                readByte = reader.ReadByte();
                accumulator |= ((ulong)readByte & 127) << (iterations * 7);
                iterations++;
            } while ((readByte & 128) != 0);

            return accumulator;
        }