Byte packer in C# (article: http://www.aspnet.cz/articles/5465-byte-packer-jak-na-binarni-datove-struktury)

BytePacker.cs

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('-', Console.WindowWidth - 1));
        Console.WriteLine(" B# | Length  | Data");
        Console.WriteLine(new string('-', Console.WindowWidth - 1));
        for (int i = 0; i < blocks.Length; i++) {
            Console.Write($" {i:X2} | {blocks[i].Length,5} B | ");
            Console.WriteLine(string.Join(' ', blocks[i].Select(x => x.ToString("x2"))));
        }
        Console.WriteLine(new string('-', Console.WindowWidth - 1));
        Console.WriteLine($"{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);
        }

    }
}