C# – Converting from byte[] to string

binaryreaderc

I have the following code:

using (BinaryReader br = new BinaryReader(
       File.Open(FILE_PATH, FileMode.Open, FileAccess.ReadWrite)))
{
    int pos = 0;
    int length = (int) br.BaseStream.Length;

    while (pos < length)
    {
        b[pos] = br.ReadByte();
        pos++;
    }

    pos = 0;
    while (pos < length)
    {
        Console.WriteLine(Convert.ToString(b[pos]));
        pos++;
    }
}

The FILE_PATH is a const string that contains the path to the binary file being read.
The binary file is a mixture of integers and characters.
The integers are 1 bytes each and each character is written to the file as 2 bytes.

For example, the file has the following data :

1HELLO HOW ARE YOU45YOU ARE LOOKING GREAT //and so on

Please note: Each integer is associated with the string of characters following it. So 1 is associated with "HELLO HOW ARE YOU" and 45 with "YOU ARE LOOKING GREAT" and so on.

Now the binary is written (I do not know why but I have to live with this) such that '1' will take only 1 byte while 'H' (and other characters) take 2 bytes each.

So here is what the file actually contains:

0100480045..and so on
Heres the breakdown:

01 is the first byte for the integer 1
0048 are the 2 bytes for 'H' (H is 48 in Hex)
0045 are the 2 bytes for 'E' (E = 0x45)

and so on..
I want my Console to print human readable format out of this file: That I want it to print "1 HELLO HOW ARE YOU" and then "45 YOU ARE LOOKING GREAT" and so on…

Is what I am doing correct? Is there an easier/efficient way?
My line Console.WriteLine(Convert.ToString(b[pos])); does nothing but prints the integer value and not the actual character I want. It is OK for integers in the file but then how do I read out characters?

Any help would be much appreciated.
Thanks

Best Answer

I think what you are looking for is Encoding.GetString.

Since your string data is composed of 2 byte characters, how you can get your string out is:

for (int i = 0; i < b.Length; i++)
{
  byte curByte = b[i];

  // Assuming that the first byte of a 2-byte character sequence will be 0
  if (curByte != 0)
  { 
    // This is a 1 byte number
    Console.WriteLine(Convert.ToString(curByte));
  }
  else
  { 
    // This is a 2 byte character. Print it out.
    Console.WriteLine(Encoding.Unicode.GetString(b, i, 2));

    // We consumed the next character as well, no need to deal with it
    //  in the next round of the loop.
    i++;
  }
}

This is the style that Microsoft tends to use in their examples.

It appears that the guidance in this area may have changed, as StyleCop now enforces the use of the C# specific aliases.

C# – Creating a byte array from a stream

It really depends on whether or not you can trust s.Length. For many streams, you just don't know how much data there will be. In such cases - and before .NET 4 - I'd use code like this:

public static byte[] ReadFully(Stream input)
{
    byte[] buffer = new byte[16*1024];
    using (MemoryStream ms = new MemoryStream())
    {
        int read;
        while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
        {
            ms.Write(buffer, 0, read);
        }
        return ms.ToArray();
    }
}

With .NET 4 and above, I'd use Stream.CopyTo, which is basically equivalent to the loop in my code - create the MemoryStream, call stream.CopyTo(ms) and then return ms.ToArray(). Job done.

I should perhaps explain why my answer is longer than the others. Stream.Read doesn't guarantee that it will read everything it's asked for. If you're reading from a network stream, for example, it may read one packet's worth and then return, even if there will be more data soon. BinaryReader.Read will keep going until the end of the stream or your specified size, but you still have to know the size to start with.

The above method will keep reading (and copying into a MemoryStream) until it runs out of data. It then asks the MemoryStream to return a copy of the data in an array. If you know the size to start with - or think you know the size, without being sure - you can construct the MemoryStream to be that size to start with. Likewise you can put a check at the end, and if the length of the stream is the same size as the buffer (returned by MemoryStream.GetBuffer) then you can just return the buffer. So the above code isn't quite optimised, but will at least be correct. It doesn't assume any responsibility for closing the stream - the caller should do that.

See this article for more info (and an alternative implementation).

Best Answer

Related Solutions

C# – the difference between String and string in C#

This is the style that Microsoft tends to use in their examples.

C# – Creating a byte array from a stream

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