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POHow can I process opcodes stored in a binary file in Perl?
 

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  1. POHow can I process opcodes stored in a binary file in Perl?
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    <p><em><a href="http://packetstormsecurity.org/files/105938/Abstract-Processor.pdf" rel="nofollow">Creating Your Own Abstract Processor</a></em> is a quick paper on what I am trying to do.</p> <p><a href="http://malcon.org/ctm.rar" rel="nofollow">http://malcon.org/ctm.rar</a> is the exact specifications on what the emulator should be.</p> <p>I am writing a sort of an emulator in Perl. This program will read in a binary file and process the hex of the binary into actions, how a processor works, but software based with different opcodes. Just a challenge thing.</p> <p>Anyhow, I am not entirely sure how to read the binary file into an array and then assign the hex from the array to the opcodes. This is part of my code:</p> <pre><code>my $opcode=''; my $file= "path/to/file"; my $IP=0; my $SP=0; my $FLAG=0; my $A=0; my $B=0; my $X=0; my @STACK=(0); open(F, "&lt;".$file) || die("Could not open file"); binmode(F); my @ROM = &lt;F&gt;; close(F); while($IP &gt;= 0) { $opcode="$ROM[$IP]"; if ($opcode eq 11) { $A = $STACK[$SP]; $IP++; } if ($opcode eq 12) { $B = $STACK[$SP]; $IP++; } if ($opcode eq 13) { $A = $B; $IP++; } if ($opcode eq 14) { $B = $A; $IP++; } </code></pre> <p>This is just the part of the code I need help with. If you need to see more of it for some reason, just let me know.</p> <p>So I changed my code to reflect an answer above, my code now looks like this:</p> <pre><code>my $opcode=''; my $file= "CTM-bootrom"; my $IP=0; my $SP=0; my $FLAG=0; my $A=0; my $B=0; my $X=0; my @STACK=(0); open my $ROM, '&lt;:raw', $file or die "Cannot open '$file': $!"; { local $/ = \1; # Read one byte at a time while (my $byte = &lt;$ROM&gt;){ while($IP &gt;= 0) { $opcode=$ROM[$IP]; if ($opcode eq 11) { $A = $STACK[$SP]; $IP++; } if ($opcode eq 12) { $B = $STACK[$SP]; $IP++; } if ($opcode eq 13) { $A = $B; $IP++; } </code></pre> <p>But now I get an error:</p> <blockquote> <p>Use of uninitialized value $opcode in string eq at Aod8.pl line 73,</p> </blockquote> <p>&lt;$ROM> to me it looks like opcode is initialized... How can I fix this problem?</p>
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