XOR checksum

[boppen]

Hi!

I'm getting a string from a device that's connected on a serial-port that looks like this;

STX Text text text ... CR ETX BCC

Where STX=0x02, ETX=0x03, CR=0x0d and BCC is the checksum 0x00-0xFF.

The checksum should be calculated using XOR of everything exept STX and BCC.

But how should I do that using Perl? I've found lots of C examples but no Perl ... can I just XOR character by character or do I need to do some XOR bit by bit?

I'm using Device::Serialport and I've got everything in a string, and then I'm using a for-loop and substr to get character by character - I don't know if that's the correct way to do it.

Thanks för any help!

Best regards, Lars Fredriksson

 

[133tcamel]

Hi,
I'm not sure about it but you can give this a try...

my $txt = 'nice text';
my $xor = 0x03 ^ 0x0d;
for ( split(//, $txt) ) { $xor ^= ord($_); };
print sprintf ("%.32b, %s", $xor, $xor);

you don't have to do this bit by bit AFAIK, 10 ^ 12 works off the bat.

---
cheers!
san

print length "The answer to life, universe & everything!

 

[boppen]

Hi!

Thanks for the answer, I think it works just as I hope - I will try it for real on Monday!
I think that ord() did the trick that I've missed ;-)

/Boppen

 

[133tcamel]

glad to be of help.. just out of curiosity, what is this a part of?

[ BTW no worries if its under a NDA, etc. ]





---
cheers!
san

print length "The answer to life, universe & everything!