[Last Call] Learn how to a build a cloud-first strategyRegister Now

x
?
Solved

C# - Convert byte[] to bit mask

Posted on 2010-08-26
3
Medium Priority
?
2,719 Views
Last Modified: 2013-12-17
Experts,

I'm writing an web app which contains a large series of Checkboxes on a page.  Once the user selects which options he/she wants I am creating a byte array like this:

//Just using 4 for simplicity:
byte[] options = new byte[4]
options[0] = Convert.ToByte(cbOption1.Checked);
options[1] = Convert.ToByte(cbOption2.Checked);
options[2] = Convert.ToByte(cbOption3.Checked);
options[3] = Convert.ToByte(cbOption4.Checked);

So saying that options 1 and 2 where checked I will end up with a byte[] array looking like this: 1100, which is expected.  I want to convert this to an integer (i.e. a bitmask) which 1100 should equal 12.

So I googled "C# byte[] to int" and most everything comes up using the BitConverter class, but I'm getting some weird values.

One example shows the checking for LittleEndian processor architecture. So:

if(BitConverter.IsLittleEndian)
      Array.Reverse(options);

int optionBitMask = BitConverter.ToInt32(options, 0);

And optionBitMask shows up as 16,842,752.

If I remove the reversing for LittleEndian and just use:

int optionBitMask = BitConverter.ToInt32(options, 0);

Then optionBitMask shows up as 257.

I'm not sure what I'm doing wrong.  How do I get an int value of 12 from a byte[] containing 1100 ?
0
Comment
Question by:P1ST0LPETE
3 Comments
 
LVL 2

Assisted Solution

by:eoindevery
eoindevery earned 200 total points
ID: 33534762
You should use BitArrays instead of ByteArrays


> How do I get an int value of 12 from a byte[] containing 1100 ?

using System.Collections;

---------------------------------------

BitArray ba = new BitArray(4);
            ba.Set(3, true);
            ba.Set(2, true);
            ba.Set(1, false);
            ba.Set(0, false);
            //ba= 1100

            int[] array = new int[1];
            ba.CopyTo(array, 0);
            Console.WriteLine(array[0]);

-> will give you 12
0
 
LVL 75

Accepted Solution

by:
käµfm³d   👽 earned 1800 total points
ID: 33534835
You're storing "bit" values in an entire byte for each position. You would need to treat each position as a bit rather than a byte. You can do so by working with the value of each byte and using a combination of shift and bitwise-or operations:
byte[] data = new byte[] { 1, 1, 0, 0 };
int result = 0;

for (int i = data.Length - 1; i >= 0; i--)
{
    result |= (data[i] << (data.Length - (i + 1)));
}

Console.WriteLine(result);

Open in new window

0
 
LVL 10

Author Comment

by:P1ST0LPETE
ID: 33535410
Thanks guys, was working on the following when I read your post:

private int BytesToInt(byte[] bytes)
{
        int result = 0;

        for (int i = 0; i < bytes.Length; i++)
        {
                result += bytes[i] << i;
        }

        return result;
}

So I was close, but obviously missing some crucial steps that kaufmed cleared up.  Also, had forgotten about the BitArray as there is no "bit" data type - well there's bool, but that's not exactly a bit. You know what i mean.
0

Featured Post

Free Tool: ZipGrep

ZipGrep is a utility that can list and search zip (.war, .ear, .jar, etc) archives for text patterns, without the need to extract the archive's contents.

One of a set of tools we're offering as a way to say thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Today I had a very interesting conundrum that had to get solved quickly. Needless to say, it wasn't resolved quickly because when we needed it we were very rushed, but as soon as the conference call was over and I took a step back I saw the correct …
Hello there! As a developer I have modified and refactored the unit tests which was written by fellow developers in the past. On the course, I have gone through various misconceptions and technical challenges when it comes to implementation. I would…
this video summaries big data hadoop online training demo (http://onlineitguru.com/big-data-hadoop-online-training-placement.html) , and covers basics in big data hadoop .
Screencast - Getting to Know the Pipeline
Suggested Courses

829 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question