Decode binary octet string in a file with perl-CodePudding

I have a file that contains for some of the lines a number that is coded as text -> binary -> octets and I need to decode that to end up with the number. All the lines where this encoded string is, begins with STRVID:

For example I have in one of the lines:

STRVID: SarI3gXp

If I do this echo "SarI3gXp" | perl -lpe '$_=unpack"B*"' I get the number in binary

0101001101100001011100100100100100110011011001110101100001110000

Now just to decode from binary to octets I do this (assign the previous command to a variable and then convert binary to octets

variable=$(echo "SarI3gXp" | perl -lpe '$_=unpack"B*"') ; printf '%x\n' "$((2#$variable))"

The result is the number but not in the correct order

5361724933675870

To get the previous number in the correct order I have to get for each couple of digits first the second digit and then the first digit to finally have the number I'm looking for. Something like this:

variable=$(echo "SarI3gXp" | perl -lpe '$_=unpack"B*"') ; printf '%x\n' "$((2#$variable))" | gawk 'BEGIN {FS = ""} {print $2 $1 $4 $3 $6 $5 $8 $7 $10 $9 $12 $11 $14 $13 $16 $15}'

And finally I have the number I'm looking for:

3516279433768507

I don't have any clue on how to do this automatically for every line that begins with STRVID: in my file. At the end what I need is the whole file but when a line begins with STRVID: then the decoded value.

When I find this:

STRVID: SarI3gXp

I will have in my file

STRVID: 3516279433768507

Can someone help with this?

CodePudding user response：

you can cross flip the numbers entirely via regex (and without back-references either) :

variable=$(echo "SarI3gXp"        | perl -lpe '$_=unpack"B*"') ; 
printf '%x\n' "$((2#$variable))"  | 

mawk -F'^$' 'gsub("..", "_&=&_")   gsub(\
                "(^|[0-9]_)(_[0-9]|$)", _) gsub("=",_)^_'

 1  3516279433768507

The idea is to make a duplicate copy on the other side, like this :

_53=53__61=61__72=72__49=49__33=33__67=67__58=58__70=70_

then scrub out the leftovers, since the numbers u now want are anchoring the 2 sides of each equal sign ("=")

CodePudding user response：

Please inspect the following sample demo code snippet for compliance with your problem.

You do not need double conversion when it can be done in one go.

Note: please read pack documentation , unpack utilizes same TEMPLATE

use strict;
use warnings;
use feature 'say';

while( <DATA> ) {
    chomp;
    /^STRVID: (. )/
        ? say 'STRVID: ' . unpack("h*",$1) 
        : say; 

}

__DATA__
It would be nice if you provide proper input data sample
 
STRVID: SarI3gXp

Perhaps the result of this script complies with your requirements.

To work with real input data file replace

while( <DATA> ) {

with 

while( <> ) {

and pass filename as an argument to the script.

Output

It would be nice if you provide proper input data sample

STRVID: 3516279433768507

Perhaps the result of this script complies with your requirements.

To work with real input data file replace

while( <DATA> ) {

with

while( <> ) {

and pass filename as an argument to the script.

./script.pl input_file.dat