in reply to Re^2: How do I read a 24 bit integer?
in thread How do I read a 24 bit integer?

  1. Little endian would have 8 trailing 0 bits, wouldn't it? I'm sure you'll be able to add a NUL byte to a string.
  2. How about reading them into four variables, and prepending them with NUL bytes?

Replies are listed 'Best First'.
Re^4: How do I read a 24 bit integer?
by Anonymous Monk on Jan 02, 2010 at 11:13 UTC
    Finally understanding this a bit, but it seems like I have one more problem.

    First, my code: 

    read FILE, $myinput, 12;
my($var1, $var2, $var3, $var4) = unpack('A3A3A3A3', $myinput);
$var1 = unpack ('N', "\x00" . $var1);
$var2 = unpack ('N', "\x00" . $var2);
$var3 = unpack ('N', "\x00" . $var3);
$var4 = unpack ('N', "\x00" . $var4);
print "$var1\n";
print "$var2\n";
print "$var3\n";
print "$var4\n";

    [download]
    The problem is that some of these values are legitimately zero, and when I try to print them, I get: 
    Use of uninitialized value in concatenation (.) or string at myscript.
+pl line 20.

    [download]
    What did I miss to allow zeroes?
[reply]
[d/l]
[select]
      Are you sure you actually read 12 bytes? Because it seems one of your variables wasn't set by the unpack (probably the $var4).
[reply]
        I have absolutely no idea. :( But this code: 
        #!/usr/bin/perl -w
use strict;

my $myinput="\x00\x00\x00\x00\x00\x00\x01\x02\x03\x04\x05\x06";
my($var1, $var2, $var3, $var4) = unpack('A3A3A3A3', $myinput);
$var1 = unpack ('N', "\x00" . $var1);
$var2 = unpack ('N', "\x00" . $var2);
$var3 = unpack ('N', "\x00" . $var3);
$var4 = unpack ('N', "\x00" . $var4);
print "$var1\n";
print "$var2\n";
print "$var3\n";
print "$var4\n";

        [download]
        produces: 
        Use of uninitialized value in concatenation (.) or string at ./test2.p
+l line 10.

Use of uninitialized value in concatenation (.) or string at ./test2.p
+l line 11.

66051
263430

        [download]
        when I would expect to see: 
        0
0
66051
264430

        [download]
[reply]
[d/l]
[select]

In Section Seekers of Perl Wisdom