Convert decimal to binary combination (of custom lenght)

Question

I need to convert several decimal numbers (or a string or 1 and 0) to a binary combination. In .NET I see many libraries working with Byte. A Byte is a manipulation of 8 bits. In my case I have to work with set of 3 bit that I need to concatenate together.

For example:

for Filter or Partition I have a 3 position bit.

What should I use to help me for this kind of conversion? At this moment I try to understand BitArray but I don't understand how to create bit a specific size then fill them easily.

Here is what I already did

    BitArray headerBits = new BitArray(new bool[] { false, false, true, true, false, false, false, false }); // 8
    BitArray filterBits = new BitArray(new bool[] { false, true, true });  // 11
    BitArray PartitionBits = new BitArray(new bool[] { true, false, true });  // 14
    BitArray CompanyPrefixBits = new BitArray(new bool[] { false, false }); // 16

Let's try with these 16 first bits. The result I want is

EDIT ------

BitArray headerBits = new BitArray(new bool[] { false, false, true, true, false, false, false, false }); // 8
BitArray filterBits = new BitArray(new bool[] { false, true, true });  // 11
BitArray PartitionBits = new BitArray(new bool[] { true, false, true });  // 14
BitArray CompanyPrefixBits = new BitArray(new bool[] { false, false }); // 16

BitArray newBitArray = new BitArray(headerBits.Cast<bool>()
.Concat(filterBits.Cast<bool>())
.Concat(PartitionBits.Cast<bool>())
.Concat(CompanyPrefixBits.Cast<bool>())
.ToArray());

var byteArray = newBitArray.ToByteArray();
Console.WriteLine($"{BitConverter.ToString(byteArray, 0)}");
// Result is 0C-2E
// I expect 30-74

How is this possible?

So you're trying to display the data as text either in hexadecimal, decimal, octal or binary format? — ChrisBD, Sep 13 '18 at 09:11
The screenshot come from the Windows Calculator but i'm only interested by hexadecimal — Bastien Vandamme, Sep 13 '18 at 09:13

György Kőszeg · Answer 1 · 2018-09-13T09:28:19.783

1

I try to understand BitArray but I don't understand how to create bit a specific size then fill them easily.

BitArrayhas several constructors. The most obvious is to create the BitArray from a bool array:

var bits = new BitArray(new[] { true, false, true, true });

The other approach is to create an uninitialized BitArray just by the size constructor and then setting the bits one by one:

var bits = new BitArray(4); // 4 bits, all false for now
for (int i = 0; i < bits.Length; i++)
    bits[i] = GetMyNextBit();

Update:

If your main issue is to convert the concatenated bits into bytes you had better you use one big BitArray for all the fields.

After you set all of the bits you can use this extension method:

public static byte[] ToByteArray(this BitArray bits)
{
    byte[] result = new byte[(bits.Length - 1) / 8 + 1];
    bits.CopyTo(result, 0);
    return result;
}

i'm only interested by hexadecimal

You can easily convert the bytes into hex string:

var result = new StringBuilder(bytes.Length * 2);
for (int i = 0; i < bytes.Length; i++)
    result.Append(bytes[i].ToString("X2"));

edited Sep 13 '18 at 09:28

answered Sep 13 '18 at 08:48

György Kőszeg

17,093
6
37
65

I also don't know how I can concatenate my bits vraiables – Bastien Vandamme Sep 13 '18 at 09:32
2

Here is a solution for concatenating `BitArray`s: https://stackoverflow.com/questions/518513/is-there-any-simple-way-to-concatenate-two-bitarray-c-net – György Kőszeg Sep 13 '18 at 09:37
+1 @taffer. Bastien, if you're dealing with a BitArray then you'll need to decide how you handle a size that is not divisible by 16 if you're looking to display the result in hex. – ChrisBD Sep 13 '18 at 09:51
The concatenation works but I still cannot convert properly to hexa. I edited my question with the code I use. the result and my expected result. – Bastien Vandamme Sep 13 '18 at 10:28
It seems endianness is not what you need. If you insert `Reverse` after the concatenated bits as well as the converted bytes you get 3074. I created a fiddle, see here: https://dotnetfiddle.net/eALFeD - EDIT: a single reverse is enough if you use `Insert` into position 0 instead of `Append` when creating the hex result (fiddle modified). – György Kőszeg Sep 13 '18 at 11:42

ChrisBD · Answer 2 · 2018-09-13T09:40:41.280

0

I see that you're reading data from an RFID tag. All data can be treated as a series of bytes, hence the examples using bytes.

If the data is to be displayed as a string in hexadecimal format then I would suggest that you read the data into an array and then use

System.Convert.ToString(data, base);

where data is your 16 bit value and base can be 2,8, 10, 16 for binary, octal, decimal or hexadecimal.

edited Sep 13 '18 at 09:40

answered Sep 13 '18 at 09:19

ChrisBD

9,104
3
22
35

Convert decimal to binary combination (of custom lenght)

2 Answers2