using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        // Test data

        byte[] prefix = {0xDE, 0xAD, 0xBE, 0xEF}; // 4 bytes

        byte[] block1 = {0xAA, 0xAA, 0xAA, 0xAA}; // 4 bytes

        byte[] block2 = {0xBB, 0xBB, 0xBB, 0xBB, 0xBB, 0xBB, 0xBB, 0xBB, }; // 8 bytes

        byte[] block3 = {0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC}; // 16 bytes

        // Pack

        var data = BytePacker.Pack(prefix, block1, block2, block3);

        Console.WriteLine($"Packed data ({data.Length} bytes):");

        Console.WriteLine(string.Join(" ", data.Select(x => x.ToString("x2"))));

        Console.WriteLine();

        // Unpack

        var blocks = BytePacker.Unpack(data, prefix.Length).ToArray();

        Console.WriteLine(new string ('-', 79));

        Console.WriteLine(" B# | Length  | Data");

        Console.WriteLine(new string ('-', 79));

        for (int i = 0; i < blocks.Length; i++)

        {

            Console.Write($" {i:X2} | {blocks[i].Length, 5} B | ");

            Console.WriteLine(string.Join(" ", blocks[i].Select(x => x.ToString("x2"))));

        }

​

        Console.WriteLine(new string ('-', 79));

        Console.WriteLine($"{blocks.Sum(x => x.Length), 11} B total");

        Console.WriteLine();

    }

}

​

public static class BytePacker

{

    public static byte[] Pack(byte[] prefix, params byte[][] blocks)

    {

        // Validate arguments

        if (blocks.Length < 2)

            throw new ArgumentOutOfRangeException(nameof(blocks), "Minimum number of blocks is 2.");

        if (blocks.Length > 256)

            throw new ArgumentOutOfRangeException(nameof(blocks), "Maximum number of blocks is 256.");

        // Write structure

        using (var ms = new System.IO.MemoryStream())

        {

            using (var bw = new System.IO.BinaryWriter(ms))

            {

                // Write prefix if any

                if (prefix != null && prefix.Length > 0)

                    bw.Write(prefix);

                // Write number of blocks

                bw.Write((byte)(blocks.Length - 1));

                // Write block lengths

                for (byte i = 0; i < blocks.Length - 1; i++)

                {

                    if (blocks[i].Length > 255)

                        throw new ArgumentOutOfRangeException(nameof(blocks), $"Block #{i} is too long. Maximum length is 255 bytes.");

                    bw.Write((byte)blocks[i].Length);

                }

​

                // Write all blocks

                for (byte i = 0; i < blocks.Length; i++)

                {

                    bw.Write(blocks[i]);

                }

            }

​

            return ms.ToArray();

        }

    }

​

    public static IEnumerable<byte[]> Unpack(byte[] data, int prefixLength = 0)

    {

        if (prefixLength < 0)

            throw new ArgumentOutOfRangeException(nameof(prefixLength));

        using (var ms = new System.IO.MemoryStream(data))

            using (var br = new System.IO.BinaryReader(ms))

            {

                // Read prefix

                if (prefixLength > 0)

                    yield return br.ReadBytes(prefixLength);

                // Get block lengths

                var numberOfBlocksExceptLast = ms.ReadByte();

                var lengths = br.ReadBytes(numberOfBlocksExceptLast);

                // Read blocks except last

                for (int i = 0; i < numberOfBlocksExceptLast; i++)

                {

                    yield return br.ReadBytes(lengths[i]);

                }

​

                // Read last block

                var bytesRead = prefixLength + 1 + numberOfBlocksExceptLast + lengths.Sum(x => x);

                var lastBlockSize = data.Length - bytesRead;

                yield return br.ReadBytes(lastBlockSize);

            }

    }

}