Convert to Hexadecimal

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Convert to Hexadecimal by davido (Cardinal) on May 17, 2012 at 18:03 UTC
unpack or sprintf to get the hex digits. The substitution operator to match the hex digits, prepending each pair with the literal '`\x`'. `my $string = "39860000N000"; my $hexlen = sprintf( '%4.4x', length $string ) =~ s/ ( \p{Hex}{2} ) / +\\x$1/grx; print "Length of ($string) in hex: ($hexlen)\n";` [download] In older versions of Perl that didn't have the /r flag you would probably want to break that into a couple of statements (and may still wish to do so for clarity's sake): `my $string = '39860000N000'; my $hexlen = sprintf '%4.4x', length $string; $hexlen =~ s/ ( \p{Hex}{2} ) /\\x$1/gx; print "Length of ($string) in hex: ($hexlen)\n";` [download] Dave	[reply] [d/l] [select]
Re^2: Convert to Hexadecimal by sauoq (Abbot) on May 17, 2012 at 19:07 UTC
`$hexlen = printf("\\x%02x\\x%02x", unpack("C2", pack("n", length($string)));` (Explanation in reply to OP.) `-sauoq "My two cents aren't worth a dime.";`	[reply] [d/l]
Re^2: Convert to Hexadecimal by martydavis (Initiate) on May 17, 2012 at 18:53 UTC
Forever grateful! Works like a charm. It will take me some time to understand it though.	[reply]
Re: Convert to Hexadecimal by sauoq (Abbot) on May 17, 2012 at 19:00 UTC
As davido points out, `sprintf()` would be almost good enough on its own. `$ perl -le 'printf( "%04x\n", 12)' 000c` [download] And, as he points out, you can get the rest of the way with `s///`. That's pretty ugly though. You could also get there a few other ways... but they are all pretty ugly. It would be nice if you could have something like `perl -le 'printf( "\\x%02x\\x%02x\n", 12 )' # WRONG \x0c\x00` [download] Unfortunately, "12" is one argument, not two. But that's where unpack comes in handy. You want to unpack a number into two (char sized) values. That leads you to `perl -le 'printf( "\\x%02x\\x%02x\n", unpack( "C2", 12 ))' WRONG \x31\x32` [download] But that's wrong too as `12` is a scalar and gets unpacked (by that) as "1", "2" (ASCII 0x31 and 0x32 respectively.) And this is where pack is useful. You want to pack that 12 into a single value before unpacking it into two. Two characters is a short... `perl -le 'printf( "\\x%02x\\x%02x\n", unpack( "C2", pack("S", 12)))' \x0c\x00` [download] Oops. Still not quite right. My architecture is little-endian (x86). But that's okay, we can force pack to give us a big-endian short. `perl -le 'printf( "\\x%02x\\x%02x\n", unpack( "C2", pack("n", 12)))' \x00\x0c # Another way to say that . . . perl -le 'printf( "\\x%02x\\x%02x\n", unpack( "C2", pack("S>", 12)))' \x00\x0c` [download] It might not be beautiful, but I think it's better than futzing about with string operations after the conversion to hex. Of course, if you read perlpacktut as suggested, I'm sure you've come to this solution already! ;-) `-sauoq "My two cents aren't worth a dime.";`	[reply] [d/l] [select]
Re: Convert to Hexadecimal by afoken (Chancellor) on May 17, 2012 at 17:11 UTC
See perlpacktut Alexander -- Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)	[reply]
Re: Convert to Hexadecimal by ikegami (Patriarch) on May 17, 2012 at 19:12 UTC
Hex is text. «2 hex bytes» makes no sense. You actually want «2 bytes equal to "\x00\x0C"», and that's obtained using `pack('n', length($string))` [download] You might also be interested in the following: `pack('n/a*', $string)` [download] It's short for `pack('n', length($string)) . $string` [download]	[reply] [d/l] [select]


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