BinaryWriter problem - "code adds some byte between Write() method"

Question

I am try to do some code using BinaryWriter and Then BinaryReader. When I wanna write I use method Write(). But the problem is that between two lines of Write method there appears a new byte which is in ASCII table in decimal 31 (sometines 24). You can see it on this image:

You can see that byte at index 4 (5th byte) is of ASCII decimal value 31. I didnt insert it there. As you can see 1st 4 bytes are reserved for a number (Int32), next are other data (some text mostly - this is not important now).

As you can see from the code i write: - into 1st line a number 10 - into 2nd line text "This is some text..."

How come came that 5th byte (dec 31) in between??

And this is the code I have:

static void Main(string[] args)
    {           
        //
        //// SEND - RECEIVE:
        //
        SendingData();
        Console.ReadLine();
    }

    private static void SendingData()
    {
        int[] commandNumbers = { 1, 5, 10 }; //10 is for the users (when they send some text)!

        for (int i = 0; i < commandNumbers.Length; i++)
        {
            //convert to byte[]
            byte[] allBytes;
            using (MemoryStream ms = new MemoryStream())
            {
                using (BinaryWriter bw = new BinaryWriter(ms))
                {
                    bw.Write(commandNumbers[i]);   //allocates 1st 4 bytes - FOR MAIN COMMANDS!
                    if (commandNumbers[i] == 10)
                        bw.Write("This is some text at command " + commandNumbers[i]); //HERE ON THIS LINE IS MY QUESTION!!!
                }
                allBytes = ms.ToArray();
            }

            //convert back:
            int valueA = 0;
            StringBuilder sb = new StringBuilder();
            foreach (var b in GetData(allBytes).Select((a, b) => new { Value = a, Index = b }))
            {
                if (b.Index == 0) //1st num
                    valueA = BitConverter.ToInt32(b.Value, 0);
                else //other text
                {
                    foreach (byte _byte in b.Value)
                        sb.Append(Convert.ToChar(_byte));
                }
            }

            if (sb.ToString().Length == 0)
                sb.Append("ONLY COMMAND");
            Console.WriteLine("Command = {0} and Text is \"{1}\".", valueA, sb.ToString());
        }
    }

    private static IEnumerable<byte[]> GetData(byte[] data)
    {
        using (MemoryStream ms = new MemoryStream(data))
        {
            using (BinaryReader br = new BinaryReader(ms))
            {
                int j = 0;
                byte[] buffer = new byte[4];
                for (int i = 0; i < data.Length; i++)
                {
                    buffer[j++] = data[i];
                    if (i == 3) //SENDING COMMAND DATA
                    {
                        yield return buffer;
                        buffer = new byte[1];
                        j = 0;
                    }
                    else if (i > 3) //SENDING TEXT
                    {
                        yield return buffer;
                        j = 0;
                    }
                }
            }
        }
    }

Side note: You're creating and destroying a writer and stream each time through your loop — Cameron
– Cameron, Commented Sep 2, 2011 at 16:32

Cameron · Accepted Answer · 2011-09-02 16:34:24Z

5

If you look at the documentation for Write(string), you'll see that it writes a length-prefixed string. So the 31 is the number of characters in your string -- perfectly normal.

answered Sep 2, 2011 at 16:34

Cameron

99.4k29 gold badges206 silver badges233 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Mitja Bonca Over a year ago

:) This is it. Just the point is that I dont want that byte. So it would be better to avoid BinaryWriter method.... the point is I wanna create an application server-client, where will be many possibilities, like chat, new game, join game, ... and 1st bytes (so in Int32) will be reserved for the command, next bytes will be the rest, like text (chat between users).

Cameron Over a year ago

Perhaps a library like lidgren would be better suited to your needs?

Conrad Frix · Accepted Answer · 2011-09-02 17:04:52Z

3

You should probably be using Encoding.GetBytes and then write the bytes instead of writing a string

for example

     bw.Write(
          Encoding.UTF8.GetBytes("This is some text at command " + commandNumbers[i])
     );

edited Sep 2, 2011 at 17:04

answered Sep 2, 2011 at 16:36

Conrad Frix

52.8k13 gold badges99 silver badges158 bronze badges

3 Comments

Mitja Bonca Over a year ago

So no BinaryReader in my code any longer? Do you mind showing me an example? And thx guys for a great and simple answers. It really does writh the Lenght of the whole string into the byte just before string.

Conrad Frix Over a year ago

@Mitja I clarified what I meant by adding a sample

Mitja Bonca Over a year ago

Thank you very much. I know how to get bytes already. I will show you my new version as soon as its over (soon). The point is to learn how to seperated messages... I will be using this code for Server-Client application. So I have to seperate comamnds from normal text.

Cole Campbell · Accepted Answer · 2011-09-02 16:32:53Z

2

When a string is written to a binary stream, the first thing it does is write the length of the string. The string "This is some text at command 10" has 31 characters, which is the value you're seeing.

answered Sep 2, 2011 at 16:32

Cole Campbell

4,8571 gold badge19 silver badges20 bronze badges

Comments

CodeCaster · Accepted Answer · 2011-09-02 16:44:09Z

1

You should check the documentation of methods you use before asking questions about them:

A length-prefixed string represents the string length by prefixing to the string a single byte or word that contains the length of that string. This method first writes the length of the string as a UTF-7 encoded unsigned integer, and then writes that many characters to the stream by using the BinaryWriter instance's current encoding.

;-)

(Though in fact it is an LEB128 and not UTF-7, according to Wikipedia).

edited Sep 2, 2011 at 16:44

answered Sep 2, 2011 at 16:38

CodeCaster

153k24 gold badges237 silver badges287 bronze badges

Comments

Frank Trocchia · Accepted Answer · 2011-09-02 17:20:58Z

0

The reason this byte is there because you're adding a variable amount of information, so the length is needed. If you were to add two strings, where would you know where the first ended and the second began?

If you really don't want or need that length byte, you can always convert the string to a byte array and use that.

answered Sep 2, 2011 at 17:20

Frank Trocchia

861 silver badge5 bronze badges

Comments

Mitja Bonca · Accepted Answer · 2011-09-02 17:32:27Z

Ok, here is my edited code. I removed BinaryWriter (while BinaryReader is still there!!), and now it works very well - no more extra bytes.

What do you thing? Is there anytihng to do better, to make it run faster? Expecially Im interesting for that foreach loop, which read from another method that is yield return type!!

New Code:

static void Main(string[] args)
    {           
        //
        //// SEND - RECEIVE:
        //
        SendingData();
        Console.ReadLine();
    }

    private static void SendingData()
    {
        int[] commands = { 1, 2, 3 }; 
        // 1 - user text
        // 2 - new game
        // 3 - join game
        // ...

        for (int i = 0; i < commands.Length; i++)
        {
            //convert to byte[]
            byte[] allBytes;
            using (MemoryStream ms = new MemoryStream())
            {
                // 1.st - write a command:
                ms.Write(BitConverter.GetBytes(commands[i]), 0, 4);
                // 2nd - write a text:                                         
                if (commands[i] == 1)
                {
                    //some example text (like that user sends it):
                    string myText = "This is some text at command " + commands[i];
                    byte[] myBytes = Encoding.UTF8.GetBytes(myText);
                    ms.Write(myBytes, 0, myBytes.Length);
                }
                allBytes = ms.ToArray();
            }

            //convert back:
            int valueA = 0;
            StringBuilder sb = new StringBuilder();
            foreach (var b in ReadingData(allBytes).Select((a, b) => new { Value = a, Index = b }))
            {
                if (b.Index == 0)
                {
                    valueA = BitConverter.ToInt32(b.Value, 0);
                }
                else
                {
                    sb.Append(Convert.ToChar(b.Value[0]));
                }
            }

            if (sb.ToString().Length == 0)
                sb.Append("ONLY COMMAND");
            Console.WriteLine("Command = {0} and Text is \"{1}\".", valueA, sb.ToString());
        }            
    }

    private static IEnumerable<byte[]> ReadingData(byte[] data)
    {
        using (MemoryStream ms = new MemoryStream(data))
        {
            using (BinaryReader br = new BinaryReader(ms))
            {
                int j = 0;
                byte[] buffer = new byte[4];
                for (int i = 0; i < data.Length; i++)
                {
                    buffer[j++] = data[i];
                    if (i == 3) //SENDING COMMAND DATA
                    {
                        yield return buffer;
                        buffer = new byte[1];
                        j = 0;
                    }
                    else if (i > 3) //SENDING TEXT
                    {
                        yield return buffer;
                        j = 0;
                    }
                }
            }
        }
    }

Collectives™ on Stack Overflow

BinaryWriter problem - "code adds some byte between Write() method"

6 Answers 6

2 Comments

3 Comments

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

6 Answers 6

2 Comments

3 Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related