perl: How to decode hex data to integer, string?

Question

Support I have some hex raw data printed using c code with format such as “%02X”.
so they look like :

\x00\x20\x00\x10\xfd\x02\x10\x00\x00\x00\x00\x20\xff\x02\x10\x00\x00\x00\x00\x00 \x05\x00\x011\x00\x01\x00\n\x00\x0240

I want to decode them following some format like:
The first two Byte hex “\x00\x20” should be decoded to a ushort:
The following two B hex “\x00\x10” should be decoded to a ushort:
The following 8B hex “\xfd\x02\x10\x00\x00\x00\x00\x20” should be coded to a 64 bit.
The following 8B hex “\xff\x02\x10\x00\x00\x00\x00`\x00” should be coded to a 64 bit;
The following 3 Byte Hex should be decoded to 3 char.
....

How do I implement the decoding in perl
(BTW I do not understand why there are backslash between each hex, is it how hex should be printed out)?

user502515 · Accepted Answer · 2010-12-05 00:14:50Z

1

s{\\x(..)}{chr hex $1}eg; for single bytes. or just unpack("v", "\x00\x20"); (see unpack function for details).

answered Dec 5, 2010 at 0:14

user502515

4,47427 silver badges21 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

user389955 Over a year ago

#!/usr/bin/perl -w $_ = "\x61\x62"; s{\\x(..)}{chr hex $1}eg; print "approach1: $_\n"; $str2 = unpack("v", "\x61\x62"); print "approach2: $str2\n";

user389955 Over a year ago

the answer is:bash-3.00# ./hex2str.pl approach1: ab approach2: 25185

user502515 Over a year ago

Indeed. And it wholly depends on what you want which approach you use. One day you say ushort (short of Perl not having "shorts" - "\x61\x62" is a string, "ab" is another string, and 25185 is a number, usually with a capacity of int), so use approach 2; the other you say "hex2str", so use appoach 1.

Marcelo Cantos · Accepted Answer · 2010-12-05 00:15:19Z

0

Decode the data:
- s/\\x(..)/chr hex $1/eg/;
- Better still, assuming you have control over the C code that generates the input, get it to output binary data in the first place and avoid this step entirely.
Use unpack to decode the components.

answered Dec 5, 2010 at 0:15

Marcelo Cantos

187k40 gold badges338 silver badges366 bronze badges

Collectives™ on Stack Overflow

perl: How to decode hex data to integer, string?

2 Answers 2

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related