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How to modify a part of a binary data?

andrei
New User

Sep 19, 2009, 7:30 PM

Post #1 of 3 (601 views)

How to modify a part of a binary data?	Can't Post

Hi everybody!

here is a simple question.

Suppose that I have some binary data stored in $data (a scalar variable). For simplicity assume, that the length of $data is 5 bytes which can be interpreted as one byte + one integer packed together. I want to modify the integer in a way that is similar to the function vec:

Code

vec EXPR,OFFSET,BITS

In other words, I do not want to unpack the data into an array of a byte and an integer, modify the integer, then pack it again. I would rather do it directly if it was possible. Any suggestions?

shawnhcorey
Enthusiast

Sep 20, 2009, 3:42 AM

Post #2 of 3 (593 views)

Re: [andrei] How to modify a part of a binary data? [In reply to]	Can't Post

In Reply To

In other words, I do not want to unpack the data into an array of a byte and an integer, modify the integer, then pack it again. I would rather do it directly if it was possible. Any suggestions?

KISS. Code that is difficult to understand is costly to maintain.

In other words, unpack it, modify it, pack it.

__END__

I love Perl; it's the only language where you can bless your thingy.

Perl documentation is available at perldoc.perl.org. The list of standard modules and pragmatics is available in perlmodlib.

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alager
Novice

Oct 8, 2009, 1:57 PM

Post #3 of 3 (489 views)

Re: [andrei] How to modify a part of a binary data? [In reply to]	Can't Post

You don't have to put it into actual temporary variables, if that is what you are trying to avoid.

Here is an example of a 16bit binary value that is incremented.

Code

 $key = pack "n", ((unpack "(n)*", $key)+1);

But you still have to pack and unpack...

Aaron

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