using a byte as a bit mask.

[bob]

Hi,
Having trouble determining if bit n in a byte is on or off.
Seem to remember being able to do this with the logical And operator
something like if (2 & mybyte) { do something}
Maybe I am dreaming of VB days.
Is there a succint way of doing this?
thanks
Bob

[TAB]

Re: using a byte as a bit mask.

Hi Bob

You are on the right track, try something like this
if ((bits & 1) != 0) // bit is set if not zero

where bits is an byte, uint or ulong.
Exhange 1 for the bit you would like to check, i.e. 1,2,4,8,16,32, ....

"bob" <startatbob_cle gg@cutthis.adri ley.co.nzskrev i meddelandet
news:als5f4pfeo 9d8je90kma4vfrc tsluep14v@4ax.c om...

Hi,
Having trouble determining if bit n in a byte is on or off.
Seem to remember being able to do this with the logical And operator
something like if (2 & mybyte) { do something}
Maybe I am dreaming of VB days.
Is there a succint way of doing this?
thanks
Bob
>

[Ignacio Machin ( .NET/ C# MVP )]

Re: using a byte as a bit mask.

On Oct 13, 2:10 pm, bob <startatbob_cl. ..@cutthis.adri ley.co.nz>
wrote:

Hi,
Having trouble determining if bit n in a byte is on or off.
Seem to remember being able to do this with the logical And operator
something like if (2 & mybyte) { do something}
Maybe I am dreaming of VB days.
Is there a succint way of doing this?
thanks
Bob

It's similar here , you use & or | , note that it's only one if you
use two (&&) it's the logic operation instead of the bit operation.

[Peter Morris]

Re: using a byte as a bit mask.

public bool IsBitSet(byte value, byte bitNumber)
{
return value & (1 << bitNumber);
}

Something like that anyway :-)



--
Pete
====

http://mrpmorris.blogspot.com

http://www.capableobjects.com

[bob]

Re: using a byte as a bit mask.

Hi Anders,
Spot on.
Dunno why I couldn't see it.
Thanks

On Mon, 13 Oct 2008 20:49:19 +0200, "TAB" <anders.berglun d@email.com>
wrote:

>Hi Bob
>
>You are on the right track, try something like this
if ((bits & 1) != 0) // bit is set if not zero
>
>where bits is an byte, uint or ulong.
>Exhange 1 for the bit you would like to check, i.e. 1,2,4,8,16,32, ....
>
>"bob" <startatbob_cle gg@cutthis.adri ley.co.nzskrev i meddelandet
>news:als5f4pfe o9d8je90kma4vfr ctsluep14v@4ax. com...

>Hi,
>Having trouble determining if bit n in a byte is on or off.
>Seem to remember being able to do this with the logical And operator
>something like if (2 & mybyte) { do something}
>Maybe I am dreaming of VB days.
>Is there a succint way of doing this?
>thanks
>Bob
>>

[=?ISO-8859-1?Q?G=F6ran_Andersson?=]

Re: using a byte as a bit mask.

Peter Morris wrote:

public bool IsBitSet(byte value, byte bitNumber)
{
return value & (1 << bitNumber);
}
>
Something like that anyway :-)
>
>
>

Close. ;)

return (value & (1 << bitNumber)) != 0;

Note, just to be overly clear: bitNumber is zero based.

--
Göran Andersson
_____

http://www.guffa.com

[Michael J. Ryan]

Re: using a byte as a bit mask.

Effectively you just want to check a given value against x..

int value = X; //user input, or saved value
int check = 1<<3; //third to last bit 0x0...001000
bool hasCheck = (value & check == check);


I am pretty sure you can do something like the following...
[Flags]
public enum MyOptions : int {
None= 0,
First= 1,
Second= 1<<1,
Third= 1<<2
}

public bool HasOption(MyOpt ions value, MyOptions check) {
return (value & check == check);
}

On 10/13/2008 11:10 AM, bob wrote:

Hi,
Having trouble determining if bit n in a byte is on or off.
Seem to remember being able to do this with the logical And operator
something like if (2 & mybyte) { do something}
Maybe I am dreaming of VB days.
Is there a succint way of doing this?
thanks
Bob
>

--
Michael J. Ryan - tracker1(at)the roughnecks(dot) net - www.theroughnecks.net
icq: 4935386 - AIM/AOL: azTracker1 - Y!: azTracker1 - MSN/Win: (email)

.... B5: The mind sees what it needs to see. The soul sees what the soul sees.