OpenStory.Cryptography.RollingIv.ConstructHeader C# (CSharp) Method

        public byte[] ConstructHeader(int length)
        {
            if (length < 2)
            {
                throw new ArgumentOutOfRangeException("length", length, CommonStrings.PacketLengthMustBeMoreThan2Bytes);
            }

            int encodedVersion = ((this.iv[2] << 8) | this.iv[3]) ^ this.versionMask;
            int encodedLength = encodedVersion ^ (((length & 0xFF) << 8) | (length >> 8));

            var header = new byte[4];
            unchecked
            {
                header[0] = (byte)(encodedVersion >> 8);
                header[1] = (byte)encodedVersion;
                header[2] = (byte)(encodedLength >> 8);
                header[3] = (byte)encodedLength;
            }

            return header;
        }

 /// <summary>
 /// Constructs a packet header and encodes the given length in it.
 /// </summary>
 /// <remarks>
 /// When overriding this method in a derived class,
 /// do not call the base implementation.
 /// </remarks>
 /// <param name="length">The length of the packet.</param>
 /// <returns>a 4-element byte array which should be prepended to the packet data.</returns>
 private byte[] ConstructHeader(int length)
 {
     return(_encryptor.ConstructHeader(length));
 }