Convert Byte Array to Bit Array?

Question

How would I go about converting a bytearray to a bit array?

Elly

Answer 1

The obvious way; using the constructor that takes a byte array:

BitArray bits = new BitArray(arrayOfBytes);

Alula

What about to a pre-existing bit array? – Monroemonroy

Answer 2

It depends on what you mean by "bit array"... If you mean an instance of the BitArray class, Guffa's answer should work fine.

If you actually want an array of bits, in the form of a bool[] for instance, you could do something like that :

byte[] bytes = ...
bool[] bits = bytes.SelectMany(GetBits).ToArray();

...

IEnumerable<bool> GetBits(byte b)
{
    for(int i = 0; i < 8; i++)
    {
        yield return (b & 0x80) != 0;
        b *= 2;
    }
}

Bustos

Your answer is more appropriate than the answer above cos result contains leading zeros. +1 – Cambell

Answer 3

public static byte[] ToByteArray(this BitArray bits)
 {
    int numBytes = bits.Count / 8;
    if (bits.Count % 8 != 0) numBytes++;
    byte[] bytes = new byte[numBytes];
    int byteIndex = 0, bitIndex = 0;
    for (int i = 0; i < bits.Count; i++) {
        if (bits[i])
            bytes[byteIndex] |= (byte)(1 << (7 - bitIndex));
        bitIndex++;
        if (bitIndex == 8) {
            bitIndex = 0;
            byteIndex++;
        }
    }
    return bytes;
}

Parallelogram

Just curious.. Doesn't he want the function the other way?!! – Sexology

Answer 4

You can use BitArray to create a stream of bits from a byte array. Here an example:

string testMessage = "This is a test message";

byte[] messageBytes = Encoding.ASCII.GetBytes(testMessage);

BitArray messageBits = new BitArray(messageBytes);

Unlimber

Answer 5

byte number  = 128;
Convert.ToString(number, 2);

=> out: 10000000

Hawkinson

Could you please provide a bit more detail of what you are doing and how it is working? – Hottempered

From the documentation >ToString(Byte, Int32) Converts the value of an 8-bit unsigned integer to its equivalent string representation in a specified base. – Rightward

Answer 6

public static byte[] ToByteArray(bool[] byteArray)
{
    return = byteArray
               .Select(
                    (val1, idx1) => new { Index = idx1 / 8, Val = (byte)(val1 ? Math.Pow(2, idx1 % 8) : 0) }
                )
                .GroupBy(gb => gb.Index)
                .Select(val2 => (byte)val2.Sum(s => (byte)s.Val))
                .ToArray();
}

Electroluminescence