issue with byte array, I cant Shift left byte

Question

I want to convert a string containing a binary number into an array of bytes. For that, I have this function:

private byte[] ToByteArray(string StringToConvert)
{
   byte[] ByteArray = new byte[StringToConvert.Length/8];
   byte temp;
   for (int i = 0; i < StringToConvert.Length; i=i+8)
   {
      for (int j = i; j < 8; j++)
      {
         temp = Convert.ToByte(StringToConvert[j]);
         ByteArray[i]=ByteArray[i] << temp;
      }
   }

   return ByteArray;
}

I get an error that I can not convert byte to int(?) at

ByteArray[i]=ByteArray[i]<< temp;

What am I doing wrong?

And you start with an array full of 0 and then they only get shifted around... End result: all zeroes. — Henk Holterman
– Henk Holterman, Commented Apr 30, 2014 at 7:26
i want to take 8 bit and make it a byte, that's the point. Henk Holterman do u have a better solution? — user3531487
– user3531487, Commented Apr 30, 2014 at 7:33

Daniel Brückner · Accepted Answer · 2014-04-30 08:45:06Z

1

This will convert a string containing a binary number like "001011101101011010101011" into a byte array { 46, 214, 171 }.

private Byte[] ToByteArray(String stringToConvert)
{
   Contract.Requires(stringToConvert != null);
   Contract.Requires(stringToConvert.Length % 8 == 0);

   var result = new Byte[stringToConvert.Length / 8];

   for (var index = 0; index < stringToConvert.Length / 8; index++)
   {
      result[index] = Convert.ToByte(stringToConvert.Substring(index * 8, 8), 2);
   }

   return result;
}

edited Apr 30, 2014 at 8:45

answered Apr 30, 2014 at 8:04

Daniel Brückner

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Comments

Manish Dalal · Accepted Answer · 2014-04-30 07:41:26Z

0

Use

ByteArray[i] = (byte)(ByteArray[i] << temp);

As mentioned on MSDN (Shift Operators), the following is the predefined shift operators

int operator <<(int x, int count);
uint operator <<(uint x, int count);
long operator <<(long x, int count);
ulong operator <<(ulong x, int count);

and the byte values (ByteArray[i]) matches the first operator specification which is then invoked and returns an int value. So, to store the int value in byte, you have to typecast it to byte. As int to byte is not implicit (data loss may occur), so you have to explicitly do the cast, as shown in the line above.

answered Apr 30, 2014 at 7:41

Manish Dalal

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Comments

jaket · Accepted Answer · 2014-04-30 07:45:16Z

0

I'm going to read between the lines and guess that StringToConvert is a string containing multiples of 8 '0's or '1's, and that what you are trying to do is convert it to an array of bytes.

private byte[] ToByteArray(string StringToConvert)
{
    byte[] ByteArray = new byte[StringToConvert.Length/8];
    for (int i = 0; i < StringToConvert.Length/8; i++)
    {
        for (int j = 0; j < 8; j++)
        {
            char bitStr = StringToConvert[i*8+j];
            ByteArray[i] = (byte)((ByteArray[i] << 1) | (bit=='1' ? 1 : 0));
        }
    }

    return ByteArray;
}

answered Apr 30, 2014 at 7:45

jaket

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2 Comments

user3531487 Over a year ago

lol i forgot the [i*8+j] part... can i ask why the (bit=='1' ? 1 : 0) part is necessary? the "(byte)(ByteArray[i] << temp)" solution is as good as your solution?

jaket Over a year ago

@user3531487 They are not equivalent at all. Convert.ToByte('1') == 0x31 whereas you want it to equal 0x1.

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