C# Split byte[] by hexademimal value into new array of byte[]

Question

I want to take data from an IP packet which is a byte array and split it into a collection of byte arrays that start with 0x47 i.e. mpeg-2 transport packets.

For example the original byte array looks like this:

08 FF FF 47 FF FF FF 47 FF FF 47 FF 47 FF FF FF FF 47 FF FF

How would you split the byte array on 0x47 and retain the deliminator 0x47 so it looks like this? In order words an array of byte arrays that start on a particular hexadecimal?

[0] 08 FF FF
[1] 47 FF FF FF
[2] 47 FF FF
[3] 47 FF
[4] 47 FF FF FF FF
[5] 47 FF FF

Why not simply loop through that? That ought to work in like O(2n) time, I suppose. — Nikhil Girraj
– Nikhil Girraj, Commented Jun 24, 2016 at 19:50

Dmitrii Bychenko · Accepted Answer · 2016-06-24 19:45:30Z

You can easily implement the splitter required:

public static IEnumerable<Byte[]> SplitByteArray(IEnumerable<Byte> source, byte marker) {
  if (null == source)
    throw new ArgumentNullException("source");

  List<byte> current = new List<byte>();

  foreach (byte b in source) {
    if (b == marker) {
      if (current.Count > 0)
        yield return current.ToArray();

      current.Clear();
    }

    current.Add(b);
  }

  if (current.Count > 0)
    yield return current.ToArray();
}

and use it:

  String source = "08 FF FF 47 FF FF FF 47 FF FF 47 FF 47 FF FF FF FF 47 FF FF";

  // the data
  Byte[] data = source
    .Split(' ')
    .Select(x => Convert.ToByte(x, 16))
    .ToArray();

  // splitted
  Byte[][] result = SplitByteArray(data, 0x47).ToArray();

  // data splitted has been represented for testing
  String report = String.Join(Environment.NewLine, 
    result.Select(line => String.Join(" ", line.Select(x => x.ToString("X2")))));

  // 08 FF FF
  // 47 FF FF FF
  // 47 FF FF
  // 47 FF
  // 47 FF FF FF FF
  // 47 FF FF
  Console.Write(report);

Matias Cicero · Accepted Answer · 2016-06-24 20:03:26Z

2

A possible solution:

byte[] source = // ...
string packet = String.Join(" ", source.Select(b => b.ToString("X2")));

// chunks is of type IEnumerable<IEnumerable<byte>>
var chunks = Regex.Split(packet, @"(?=47)")
             .Select(c =>
                 c.Split(new [] { ' ' }, StringSplitOptions.RemoveEmptyEntries)
                 .Select(x => Convert.ToByte(x, 16)));

edited Jun 24, 2016 at 20:03

answered Jun 24, 2016 at 19:32

Matias Cicero

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Comments

pay · Accepted Answer · 2016-06-24 19:30:19Z

1

Maybe a little too hacky for you, but should work just fine:

string ins = "08 FF FF 47 FF FF FF 47 FF FF 47 FF 47 FF FF FF FF 47 FF FF ";
string[] splits = ins.Split(new string[] { "47" }, StringSplitOptions.None);
for (int i = 0; i < splits.Length; i++) {
     splits[i] = "47 " + splits[i];
}

Edit: similar to the already existing answer I guess.

answered Jun 24, 2016 at 19:30

pay

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Ingenioushax · Accepted Answer · 2016-06-24 19:20:30Z

0

There's a couple of ways to do this, the easiest approach is to just use .Split() and replace the value that is being split on.

string[] values = packet.Split("47");
for(int i = 0; i < values.Length; i++)
{
    Console.WriteLine("[{0}] 47 {1}", i, values[i]);
    // C# 6+ way: Console.WriteLine($"[{i}] 47 {values[i]}");
}

Of course, you can always use regular expressions, but my Regex skills are pretty limited and I don't think I could personally construct a valid regex for this.

answered Jun 24, 2016 at 19:20

Ingenioushax

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2 Comments

Jonathan Kittell Over a year ago

This would work, string[] mpegPackets = Regex.Split(data, "(?=47)"); I guess you are right I need to convert the hex values to string in order to split.

Nikhil Girraj Over a year ago

Isn't the question about an Array of bytes?

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