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Validating bits

I have a char (1 byte) value inside a struct. I need to check each bit - and if certain bits are set, perform certain operations.

How do i check each bit within a byte?

giltjr

What language?

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List244

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jewee

ASKER

Sorry, I meant to post this under the C programming language.

List244

Should work for C as well.

lostcarpark

I would suggest you define the meanings for your bits (hex is often easiest):

#define VALID_USER 0x01
#define LOGGED_IN 0x02
#define HAS_DOG 0x04
#define FAST_CAR 0x08
#define GOLD_CARD 0x10

You could then define a specific combination of bits you want to test for with the "or" operater:

#define VALID_LOG_CAR (VALID_USER | LOGGED_IN | GLAD_CARD)

Then, loop the bytes you want to check, and test each byte with the "and" operater:

if ((c & VALID_LOG_CAR) == VALID_LOG_CAR)
{

}

Hope this helps.

James

jewee

ASKER

I am looking to validate each one individually - for example, if bit 7 is set, then perform some operation, if bit 6, then call another function...etc.

jewee

ASKER

I am reading from a binary file

List244

Jewee that is what my example does, take a look. You get the byte and then you can view each individual bit to see
if it is set or not. If it is 0 it is not set, if it is not 0 then it is set. The value that you retrieve will be the value of that
bits placeholder. The bits run 0-7 for the byte, so you check each like so:

(MyByte & (1 << 0)) //Check bit 0
(MyByte & (1 << 0)) //Check bit 1
(MyByte & (1 << 0)) //Check bit 2
(MyByte & (1 << 0)) //Check bit 3
(MyByte & (1 << 0)) //Check bit 4
(MyByte & (1 << 0)) //Check bit 5
(MyByte & (1 << 0)) //Check bit 6
(MyByte & (1 << 0)) //Check bit 7