converting a byte array to a bitset

[dendenners]

Hey there,
Does anyone have a method to convert a byte array to a bitset? I have one but it doesn't seem to work properly. Thanks.

 

[meadandale]

No but I could write one easily enough. First of all, you have to decide what your rules are for turning a byte into a bit. Does a 0 byte equate to a 0 bit and a non zero byte equate to a 1 bit? That's what I will do:

public BitSet byteArrayToBitSet(byte [] bits)
{
int length = bits.length;
BitSet set = new BitSet(length);
for (int i = 0; i < length; i++)
{
if (bits != 0)
set.set(i);
}
return set;
}

 

[dendenners]

Hey there,
No I need to convert each byte to its bit representation, and then put each individual converted bit into the bitset. The reason I ask is that I have one example but I'm not sure if its working properly. Here it is:

public static BitSet byte2BitSet
(byte[] b, int offset, boolean bitZeroMeansExtended)
{
int len = bitZeroMeansExtended ?
((b[offset] & 0x80) == 0x80 ? 128 : 64) : 64;

BitSet bmap = new BitSet (len);
for (int i=0; i<len; i++)
if (((b[offset + (i >> 3)]) & (0x80 >> (i % 8))) > 0)
bmap.set(i+1);
return bmap;
}
}
Thanks a lot.

 

[meadandale]

So, are you saying that if you had four bytes then you want 32 bits in the bitset? How do you want it represented? Big endian or little endian?

 

[dendenners]

Thanks for the input. I discovered the above method works fine, the problem I had was in a different part of the code.

 

[Guest_imported]

Thanks, I was really looking for a function like this. Now I only need more functions to work with bits. To check if a bitset is, say, 1010, I'll have to do:

if (bitset.get(0) && !bitset.get(1) && bitset.get(2) && !bitset.get(3)) { my_lucious_function(); }

Lots of job if I have to check for occurances of bit combinations in larger maps... Any better ideas?

 

[meadandale]

Create the bitset that you are looking for and do a comparison:

BitSet lucious = new BitSet();
lucious.set(0);
lucious.set(2);

...

if (bitset.equals(lucious) {my_lucious_function();}

You can create a different bitset object for each 'switch' that you want to do.