state of bit test 1

[MerryMadDad]

Hello,

I am trying to test the state of bits in a byte, active low state I used the case of statement
case of
254: do something
253: do something else
251:
247: and so on

The problem is without working out every possible combination, how can I detect that two bits are active at the same time ?

in assembly language I could clear the carry bit and rotate all the bits left or right and branch on the state of the carry bit, can I do something similar in Delphi pascal ? I am using Delphi 4.00 at the moment.

any help much appreciated Thanks in advance.
MMD

 

[towerbase]

The following function returns the number of bits set in a byte:

function CountSetBitsInByte ( b: byte ): integer;
var
  eight: integer;
begin
  result := 0;
  for eight := 1 to 8 do begin
    if b and 1 = 1 then
      inc ( result );
    b := b shr 1;
  end;
end;

Hope that helps.

Andrew

 

[MerryMadDad]

Hi Andrew, thanks very much for that, it is just what I am looking for

Best regards

Robert

 

[towerbase]

The following code is simpler and will probably run a bit quicker but I haven't timed it to make sure. It returns true if the byte has multiple bits and false if not.

function HasMultipleBitsSetInByte ( b: byte ): boolean;
begin
  result := not ( b in [ 0, 1, 2, 4, 8, 16, 32, 64, 128 ] );
end;

Andrew

 

[noghte]

sorry for off-topic question towerbase, but how do you compare different programs to find out which one is quicker?

 

[towerbase]

Start a new topic if you want answers to this question.

Andrew

 

[MerryMadDad]

Hello All,

I just found out that TurboPower's systools has an StBits program that can "twiddle" the state of bits in a byte and presumably read them too. Available free from

http://www.sourceforge.net

(search for TurboPower) along with loads of other tools and components etc.

For anyone thats interested

Regards

MMD