BitArray alternative for the .NET Micro Framework

Question

Is there a BitArray alternative for the .NET Micro Framework? I was thinking about simply using a bool[], but how can you convert it back into a byte[] ?

In the full framework, considering "bits" is a BitArray, the following works:

byte[] data = new byte[dimensions / 8];
bits.CopyTo(data, 0);

But I cannot seem to find the BitArray class in the micro framework

Conchiferous

What exactly do you need? Maybe a byte which you can manipulate is enough? – Grosberg

BitArray is implemented using integers and bitwise operators – Hump

@Grosberg nope really needed to operate at the bit level :-) – Conchiferous

Answer 1

It's not terribly difficult to duplicate the functionality of BitArray. First, if you need fewer than 65 bits, then you can do it with a long or smaller.

To set an individual bit:

void Set(ref long ba, int bit)
{
    ba |= 1L << bit;
}

To clear a bit:

void Clear(ref long ba, int bit)
{
    long mask = 1L << bit;
    mask = ~mask;
    ba &= mask;
}

To see if a bit is set:

bool IsSet(long ba, int bit)
{
    long mask = 1L << bit;
    return (ba & mask) != 0;
}

If you have more than 64 bits, then you'll need to create an array (byte[], probably), and do the division to determine which byte/bit you want to modify. The methods above will work, provided you change the long to byte.

For example, if you have:

byte[] myBytes = new byte[128];

You have 1024 bits.

To set a bit:

void Set (int bit)
{
    int byte = bit/8;
    int bitIndex = bit%8;
    myBytes[byte] |= (byte)(1 << bitIndex);
}

The other methods use the same math to get the byte and bit index, and setting, clearing, and testing a bit is the same as with the long example above.

Enclose

If Interlocked.CompareExchange is available on the micro framework, one could use that to make any desired types of bit operations atomic. Within a loop, read the old value of the word, compute a new value, and CompareExchange the old value to the new one; reloop until the CompareExchange succeeds. I personally like having an atomic method to compute Thebits = (TheBits & ~Mask) ^ NewBits). Bits which are clear in Mask and NewBits are left alone; those that are clear in Mask and set in NewBits are toggled. Bits that are set in Mask will be copied from NewBits. – Dunton

Answer 2

You can find a BitArray Implementation in the 802.15.4 Stack. Just search the Porting Kit for BitArray.cs

Utoaztecan

Answer 3

I uploaded an array for .net microframework:

http://code.tinyclr.com/project/310/bitarray-class/

Hope this helps.

Yablon