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From: gnb@bby.oz.au (Gregory N. Bond)
Newsgroups: comp.lang.perl
Subject: Calculating XOR checksums? Fast splitting?
Message-ID: <GNB.91Jun3135656@leo.bby.oz.au>
Date: 3 Jun 91 03:56:56 GMT
Article-I.D.: leo.GNB.91Jun3135656
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Organization: Burdett, Buckeridge and Young Ltd.
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Given a string, what is the fastest way to calculate the XOR of all
bytes?  here is what I used:

    $bcc = 0;
    grep ($bcc ^= $_, unpack("C" x length($sc_data), $sc_data));

But is there a batter way without having to construct and destroy the
array? (I need this to be fairly quick...).

And a second point, what is likely to be faster to split a string into
several subfields?  A regexp:
	$str =~ /(.{32})(.{24})(.{8})/;
	($a, $b, $c) = ($1, $2, $3);
or unpack:
	($a, $b, $c) = unpack("c32 c24 c8", $str);
or substr:
	$a = substr($str, 0, 32);
	$b = substr($str, 32, 24);
	$c = substr($str, 32 + 24, 8);

Or something I haven't considered?

Greg, performance weenie (at least for this application!)
--
Gregory Bond, Burdett Buckeridge & Young Ltd, Melbourne, Australia
Internet: gnb@melba.bby.oz.au    non-MX: gnb%melba.bby.oz@uunet.uu.net
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