I know this is outside the scope of the original question but this is a good opportunity to try your hand at some testing! Sometimes a regexp might look like it will do the job but how can you be SURE it does what you expect?

Try the following code:

use Test::Simple tests => 14;
use strict;

#
# PUT THE REGEXP TO TEST HERE
#
my $testregexp = qr/\x26\x67(?!.{0,6}\x26\x67).{8}/s;

sub mytest( $ ) {
    return( ( $_[0] =~ m/$testregexp/ ) ? 1 : 0 );
}

# tests
ok( mytest( "\x26\x67________" ),
    "lead bytes followed by 8 clear bytes" );
ok( !mytest( "\x26\x67_______" ),
    "lead bytes followed by only 7 clear bytes" );
ok( mytest( "\x26\x67_________" ),
    "lead bytes followed by 9 clear bytes" );
ok( !mytest( "\x26\x67\x26\x67______" ),
    "lead bytes with 2 bad bytes" );
ok( !mytest( "\x26\x67_\x26\x67_____" ),
    "lead bytes with 2 bad bytes" );
ok( !mytest( "\x26\x67_____\x26\x67_" ),
    "lead bytes with 2 bad bytes" );
ok( !mytest( "\x26\x67______\x26\x67" ),
    "lead bytes with 2 bad bytes" );
ok( mytest( "\x26\x67________\x26\x67" ),
    "lead bytes with 1 bad byte inside the eight byte limit" );
ok( mytest( "\x26\x67_______\x26\x67" ),
    "lead bytes with 1 bad bytes" );
ok( !mytest( "\x26\x67\x26\x67\x26\x67____" ),
    "lead bytes with 2 sets of bad bytes" );
ok( !mytest( "\x26\x67\x26\x67_\x26\x67___" ),
    "lead bytes with 2 sets of bad bytes" );
ok( !mytest( "\x26\x67_\x26\x67\x26\x67___" ),
    "lead bytes with 2 sets of bad bytes" );
ok( !mytest( "\x26\x67_\x26\x67___\x26\x67" ),
    "lead bytes with 2 sets of bad bytes" );
ok( !mytest( "\x26\x67\x26\x67____\x26\x67" ),
    "lead bytes with 2 sets of bad bytes" );

[download]

You can see that I've tried to cover all the cases I can think of in your requirements. Do they look right? Do the test situations describe all the match/nomatch situations you're expecting?

The test script produces the following output:

C:\temp>perl -w regexp.t
1..14
ok 1 - lead bytes followed by 8 clear bytes
ok 2 - lead bytes followed by only 7 clear bytes
ok 3 - lead bytes followed by 9 clear bytes
ok 4 - lead bytes with 2 bad bytes
ok 5 - lead bytes with 2 bad bytes
ok 6 - lead bytes with 2 bad bytes
ok 7 - lead bytes with 2 bad bytes
ok 8 - lead bytes with 1 bad byte inside the eight byte limit
ok 9 - lead bytes with 1 bad bytes
ok 10 - lead bytes with 2 sets of bad bytes
ok 11 - lead bytes with 2 sets of bad bytes
ok 12 - lead bytes with 2 sets of bad bytes
ok 13 - lead bytes with 2 sets of bad bytes
ok 14 - lead bytes with 2 sets of bad bytes

[download]

You can plug in anybody's suggestion into the script and verify that it does, indeed, do what you want. If you get the hang of a little testing now you'll find it easier for other things too! Good luck!

In reply to Re: regex for negating a sequence by monarch
in thread regex for negating a sequence by spurperl

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