Work with bits

[Guest]

I have some problems which getting bites.
For example 247 it is 11110111 in bytes.

int i = 247; // 11110111

How I can get some pozition on bite?
Something like this
i[0] = 1;
i[1] = 1;
i[2] = 1;
i[3] = 0;
i[4] = 1;
i[5] = 1;
i[6] = 1;
i[7] = 1;

So I can get 1 or 0 for any pozition.
i[2] = 1;
How I can do this?

 

[Guest]

I have some problems which getting bites.
For example 247 it is 11110111 in bytes.

int i = 247; // 11110111

How I can get some pozition on bite?
Something like this
i[0] = 1;
i[1] = 1;
i[2] = 1;
i[3] = 0;
i[4] = 1;
i[5] = 1;
i[6] = 1;
i[7] = 1;

So I can get 1 or 0 for any pozition.
i[2] = 1;
How I can do this?

Welcome to the world of bit manipulation !

Try look at this code:

using System;

namespace E
{
public class Program
{
public static void Main(string[] args)
{
byte v = 247;
for(int i = 0; i < 8; i++)
{
Console.WriteLine(i + " " + ((v >> i) & 1));
}
Console.ReadKey();
}
}
}

Arne

 

[deerchao]

I have some problems which getting bites.
For example 247 it is 11110111 in bytes.

int i = 247; // 11110111

How I can get some pozition on bite?
Something like this
i[0] = 1;
i[1] = 1;
i[2] = 1;
i[3] = 0;
i[4] = 1;
i[5] = 1;
i[6] = 1;
i[7] = 1;

So I can get 1 or 0 for any pozition.
i[2] = 1;
How I can do this?

Welcome to the world of bit manipulation !

Try look at this code:

using System;

namespace E
{
public class Program
{
public static void Main(string[] args)
{
byte v = 247;
for(int i = 0; i < 8; i++)
{
Console.WriteLine(i + " " + ((v >> i) & 1));
}
Console.ReadKey();
}
}

}

Arne

Maybe it's a better idea to shift left but not right?
Because int is signed, shit right may expand the sign bit.

 

[=?ISO-8859-1?Q?Arne_Vajh=F8j?=]

Maybe it's a better idea to shift left but not right?
Because int is signed, shit right may expand the sign bit.

For this code it does not matter.

Arne

 

[Nicholas Paldino [.NET/C# MVP]]

You can use the BitArray class, passing in the integer, like so:

BitArray bitArray = new BitArray(new int[]{i});

Now, bitArray[0] is equal to true, bitArray[3] is false, and so on, and
so on.

 

[Michael C]

You can use the BitArray class, passing in the integer, like so:

BitArray bitArray = new BitArray(new int[]{i});

Now, bitArray[0] is equal to true, bitArray[3] is false, and so on, and
so on.

This is potentially inefficient I guess. It's possibly better to just loop
through the bits using & and <<.

Michael

 

[Nicholas Paldino [.NET/C# MVP]]

Michael,

"better" is a subjective term, at best. If you were to ask the OP, I
would say that using a BitArray is better, since it gives him the exact
functionality he is looking for.

Also, "potentially" inefficient doesn't hold much meaning. It probably
is slower than just applying a bit mask, but to be honest, I don't know how
much slower it can be and depending on what you are doing, how significant
that performance hit will be.


--
- Nicholas Paldino [.NET/C# MVP]
- (e-mail address removed)

You can use the BitArray class, passing in the integer, like so:

BitArray bitArray = new BitArray(new int[]{i});

Now, bitArray[0] is equal to true, bitArray[3] is false, and so on,
and so on.

This is potentially inefficient I guess. It's possibly better to just loop
through the bits using & and <<.

Michael

 

[Michael C]

Michael,

"better" is a subjective term, at best. If you were to ask the OP, I
would say that using a BitArray is better, since it gives him the exact
functionality he is looking for.

Also, "potentially" inefficient doesn't hold much meaning. It probably
is slower than just applying a bit mask, but to be honest, I don't know
how much slower it can be and depending on what you are doing, how
significant that performance hit will be.

That is why I used the terms "potentially", "I guess" and "possibly".
Naturally it depends on the situation but it is wise to mention that your
solution is potentially inefficient. If used in a loop the BitConverter
could possibly be 50 to 100 times slower. (No I have not tested this and it
is a guesstimate).

Michael