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Re: Detect STX and ETX hex in received string

by ColonelPanic (Friar)
on Nov 28, 2012 at 09:08 UTC ( #1005983=note: print w/ replies, xml ) Need Help??


in reply to Detect STX and ETX hex in received string

Here is an example regex that will match as soon as 80 characters or an ETX is found. I used kcott's answer as a starting point.

use Modern::Perl; my $STX = 'a'; my $ETX = 'z'; my $re = qr{ [$STX] (?: (?<match>[^$ETX]{80}) | (?:(?<match>[^$ETX]{0, +79}) [$ETX])) }x; $_='a12345678za1234567890123456789012345678901234567'. '890123456789012345678901234567890123456789012345678901234567890z'; say $+{match} while (/$re/g);

Note that this uses named capture to put either set of matching parentheses into a single variable.



When's the last time you used duct tape on a duct? --Larry Wall


Comment on Re: Detect STX and ETX hex in received string
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Re^2: Detect STX and ETX hex in received string
by MidLifeXis (Prior) on Nov 28, 2012 at 13:32 UTC

    It appears that your solution only allows for a single-character STX or ETX token, due to the check for character classes (eg [$STX]). I am presently experiencing too much of a coffee deficiency to offer an alternative.

    Update: ... and to not recognize that STX and ETX are possibly symbols for one character tokens :-)

    --MidLifeXis

      I interpreted single-character STX and ETX codes as being intrinsic to the problem. Maybe that is not so, however. Here is a multi-character solution:
      use Modern::Perl; my $STX = 'foo'; my $ETX = 'bar'; my $re = qr{ $STX (?: (?<match>.*?) $ETX | (?:(?<match>.{80}))) }x; $_='foo12345678barfoo1234567890123456789012345678901234567'. '890123456789012345678901234567890123456789012345678901234567890bar'; say substr($+{match},0,80) while (/$re/g);

      (I added a substr() to limit the matched string to 80 characters. It appears to me that it's not trivial to meet these requirements entirely within the regex...though I'm sure others will quickly prove me wrong!)



      When's the last time you used duct tape on a duct? --Larry Wall

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