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Re^4: Wierd behaviour with HTML::Entities::decode_entities()

by ikegami (Patriarch)
on Dec 14, 2009 at 16:27 UTC ( [id://812737]=note: print w/replies, xml ) Need Help??

in reply to Re^3: Wierd behaviour with HTML::Entities::decode_entities()
in thread Wierd behaviour with HTML::Entities::decode_entities()

This is very particular to the ordering I mentioned earlier (first decimal, then hexadecimal, then named entities are expanded)

No, it isn't

Different nesting order:

>perl -MHTML::Entities -le"print decode_entities '"'; " >perl -MHTML::Entities -le"print decode_entities '"'; "

Different sibling order:

[ Can't find a valid example ]

Or I still don't understand. Please given an example where ordering matters.

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Re^5: Wierd behaviour with HTML::Entities::decode_entities()
by JadeNB (Chaplain) on Dec 14, 2009 at 17:02 UTC

    The source for decode_entities_old, which I thought was just a pure-Perl version of decode_entities, looks roughly like this (I've stripped out some context dependence):

    sub decode_entities_old { my $array = [ @_ ]; my $c; for (@$array) { s/(&\#(\d+);?)/$2 < 256 ? chr($2) : $1/eg; s/(&\#[xX]([0-9a-fA-F]+);?)/$c = hex($2); $c < 256 ? chr($c) : $1/ +eg; s/(&(\w+);?)/$entity2char{$2} || $1/eg; } return @$array; }
    With this code, and the under-populated hash my %entity2char = ( amp => '&', quot => '"' ), we have
    say decode_entities_old '&#x26;amp;quot;'; => &quot; say decode_entities_old '&amp;#x26;quot;'; => &#x26;quot;
    We would get (essentially) the opposite behaviour if we switched the second and third substitutions; that's what I mean by “This is very particular to the ordering”.

    Of course, your example shows that decode_entities (which I guess is implemented in XS—I couldn't find it in the source) doesn't exhibit this buggy behaviour, so I guess that there's a reason that the sub I quoted has _old postpended. :-)

    UPDATE: I just noticed that I'd mangled my intended bug-inducer, &&#x71;uot;, above. I wonder if decode_entities (not decode_entities_old) handles it correctly?

      If HTML::Entities were to decode &#x26;amp;quot; to &quot;, it would be buggy. I did understand you correctly. Does what I said make more sense now?

      I wonder if decode_entities (not decode_entities_old) handles it correctly?

      I don't know if that's legal in SGML/HTML — unescaped ampersand — but yes.

      $ perl -MHTML::Entities -le'print decode_entities "&&#x71;uot;"' &quot;
        You can test with this -
        <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w"> <html xmlns="" xml:lang="sv" lang="sv"> <head> <meta http-equiv="Content-Type" content="text/html;charset=iso-885 +9-1"/> </head> <body> Mic i vĀr replokal &amp;quot;The Dungeon&amp;quot; </body> </html>
        Now it very clear what the problem is...

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