Solved

Setting the bits in an unsigned char.

Posted on 2007-12-02
20
194 Views
Last Modified: 2010-04-21
Hi,

I use the attached method to get the bits out of a byte, but what is the equivalent of setting the bits in a byte?

Thanks,
Uni
BIT* convertByteToBits(BYTE aByte){

	BIT *aBits=new BIT[8];

	for(unsigned int bitCount=0;bitCount<8;bitCount++)

		aBits[bitCount]=((aByte>>bitCount)&1);

	return aBits;

}

Open in new window

0
Comment
Question by:Unimatrix_001
  • 8
  • 8
  • 3
20 Comments
 
LVL 53

Accepted Solution

by:
Infinity08 earned 250 total points
ID: 20392770
Something like this :


void setBit(BYTE &aByte, int pos) {

    aByte |= 0x01 << pos;

}

Open in new window

0
 
LVL 53

Expert Comment

by:Infinity08
ID: 20392776
And a nice getBit :


bool getBit(BYTE aByte, int pos) {

    return (aByte & (0x01 << pos));

}

Open in new window

0
 
LVL 3

Author Comment

by:Unimatrix_001
ID: 20392777
Actually, also how do I clear a bit?
0
 
LVL 53

Expert Comment

by:Infinity08
ID: 20392780
>> And a nice getBit :

With the code :

bool getBit(BYTE aByte, int pos) {
    return (aByte & (0x01 << pos));
}
0
 
LVL 55

Expert Comment

by:Jaime Olivares
ID: 20392783
I should be something like:

BYTE convertBitsToBytes(BIT *bits)

{

    BYTE result = 0;

    for (int bitCount=7;bitCount>=0;bitCount--)

        result = (result<<1) | bits[i];

    return result;

}

Open in new window

0
 
LVL 55

Expert Comment

by:Jaime Olivares
ID: 20392790
BYTE convertBitsToByte(BIT *bits)
{
      result = 0;
      for(int bitCount=7;bitCount>=0;bitCount--)
          result = (result<<1) | bits[i];
      return result;
}
0
 
LVL 53

Expert Comment

by:Infinity08
ID: 20392794
>> Actually, also how do I clear a bit?

void clearBit(BYTE &aByte, int pos) {
    aByte &= (0xFF ^ (0x01 << pos));
}
0
 
LVL 3

Author Comment

by:Unimatrix_001
ID: 20392796
Okay, cheers for that Jamie... Sorry Infinity, I'm going to get the question reopened to split the points 50/50 with you and Jamie... My bad though, I shouldn't have worded the question as setting the bits...
0
 
LVL 53

Expert Comment

by:Infinity08
ID: 20392816
>> My bad though, I shouldn't have worded the question as setting the bits...

It's quite inefficient to do it that way though - that's why I posted code to set and get single bits. For most applications, there's no need to convert a byte to an array of bits - you can simply loop over the bits in the byte directly.

You can also consider the std::bitset :

        http://www.cplusplus.com/reference/stl/bitset/

but it's not much better.
0
What Should I Do With This Threat Intelligence?

Are you wondering if you actually need threat intelligence? The answer is yes. We explain the basics for creating useful threat intelligence.

 
LVL 3

Author Comment

by:Unimatrix_001
ID: 20392823
>>For most applications, there's no need to convert a byte to an array of bits - you can simply loop over the bits in the byte directly.

I fully plan to do that, although that makes the works slightly harder, so I'll leave that for a future time. ;)
0
 
LVL 53

Expert Comment

by:Infinity08
ID: 20392850
>> I fully plan to do that, although that makes the works slightly harder, so I'll leave that for a future time. ;)

It doesn't make it harder. Instead of this :

        BIT *bits = convertByteToBits(aByte);
        for (int i = 0; i < 8; ++i) {
            std::cout << bits[i];
        }
        delete [] bits;

you'd simply have :

        for (int i = 0; i < 8; ++i) {
            std::cout << getBit(aByte, i);
        }

I don't see how that's harder ... You can even bypass the function call if you feel like it :

        for (int i = 0; i < 8; ++i) {
            std::cout << ((aByte >> i) & 0x01);
        }
0
 
LVL 3

Author Comment

by:Unimatrix_001
ID: 20392867
Well you see I dot about the file for certain bits, so at the moment it's easier for me to just read all the file in as bits...
0
 
LVL 53

Expert Comment

by:Infinity08
ID: 20392873
>> Well you see I dot about the file for certain bits, so at the moment it's easier for me to just read all the file in as bits...

I disagree, but it's your code ;)
0
 
LVL 53

Expert Comment

by:Infinity08
ID: 20392874
Do take a look at bitset in that case ...
0
 
LVL 3

Author Comment

by:Unimatrix_001
ID: 20392876
I shall... (-:
0
 
LVL 3

Author Comment

by:Unimatrix_001
ID: 20393064
Jamie, can you please post a comment...
0
 
LVL 55

Assisted Solution

by:Jaime Olivares
Jaime Olivares earned 250 total points
ID: 20393080
My solution:
BYTE convertBitsToByte(BIT *bits)
{
      result = 0;
      for(int bitCount=7;bitCount>=0;bitCount--)
          result = (result<<1) | bits[i];
      return result;
}

Greetings,
Jaime.
0
 
LVL 3

Author Closing Comment

by:Unimatrix_001
ID: 31412234
Yes, something just like that. :)
0
 
LVL 3

Author Comment

by:Unimatrix_001
ID: 20393090
Thank you. :)
0

Featured Post

Maximize Your Threat Intelligence Reporting

Reporting is one of the most important and least talked about aspects of a world-class threat intelligence program. Here’s how to do it right.

Join & Write a Comment

Suggested Solutions

When writing generic code, using template meta-programming techniques, it is sometimes useful to know if a type is convertible to another type. A good example of when this might be is if you are writing diagnostic instrumentation for code to generat…
Container Orchestration platforms empower organizations to scale their apps at an exceptional rate. This is the reason numerous innovation-driven companies are moving apps to an appropriated datacenter wide platform that empowers them to scale at a …
The viewer will learn how to user default arguments when defining functions. This method of defining functions will be contrasted with the non-default-argument of defining functions.
The viewer will learn how to clear a vector as well as how to detect empty vectors in C++.

759 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

20 Experts available now in Live!

Get 1:1 Help Now