Reputation: 12329

How to return bits from Byte

Seems elementary but I am not sure how to get each bit from a byte. Thanks for the help

Upvotes: 1

Answers (5)

Oliver

Reputation: 45119

As RyuuGan already posted you should go with the BitArrary. You just put the data in it by calling the constructor with the wanted elements.

byte[] myBytes = new byte[5] { 1, 2, 3, 4, 5 };
BitArray bitArray = new BitArray( myBytes );

Afterwards the instance has some interesting properties to easily access each bit. At first you can just call the index operator to get or set the state of each bit:

bool bit = bitArray[4];
bitArray[2] = true;

Also you can enumerate over all bits by just using a foreach loop (or any LINQ-stuff you like)

foreach (var bit in bitArray.Cast<bool>())
{
    Console.Write(bit + " ");
}

To get back from the bits to some specific type (e.g. int) is a little bit trickier, but is quite easy using this extension methods:

public static class Extensions
{
    public static IList<TResult> GetBitsAs<TResult>(this BitArray bits) where TResult : struct
    {
        return GetBitsAs<TResult>(bits, 0);
    }

    /// <summary>
    /// Gets the bits from an BitArray as an IList combined to the given type.
    /// </summary>
    /// <typeparam name="TResult">The type of the result.</typeparam>
    /// <param name="bits">An array of bit values, which are represented as Booleans.</param>
    /// <param name="index">The zero-based index in array at which copying begins.</param>
    /// <returns>An read-only IList containing all bits combined to the given type.</returns>
    public static IList<TResult> GetBitsAs<TResult>(this BitArray bits, int index) where TResult : struct
    {
        var instance = default(TResult);
        var type = instance.GetType();
        int sizeOfType = Marshal.SizeOf(type);

        int arraySize = (int)Math.Ceiling(((bits.Count - index) / 8.0) / sizeOfType);
        var array = new TResult[arraySize];

        bits.CopyTo(array, index);

        return array;
    }
}

With this in place you can just get out of it with this single line of code:

IList<int> result = bitArray.GetBitsAs<int>();

Upvotes: 2

RyuuGan

Reputation: 792

Try to use BitArray.

byte[] myBytes = new byte[5] { 1, 2, 3, 4, 5 };
BitArray myBA3 = new BitArray( myBytes );

Upvotes: 2

Niet the Dark Absol

Reputation: 324790

The bits are "numbered" 0 to 7 from right to left. So to get the 5th bit, you'd use byte & (1<<5)
I'm sure there's a clearer way of explaining this >_>

EDIT: This would work in an IF statement, but if you want just the 1 or 0 specifically, use winwaed's solution.

Upvotes: 3