So this scanner will backtrack quite a bit. Every word that turns out to
not be a an email address will be processed starting from every
character. To eliminate that you can add a pattern just before any that
consumes email_chars+. As long as it doesn't contain '@' it will just
replace the default for something that looks almost like an email, but
isn't quite.
-Adrian
Matthieu Tourne wrote:
So I'm doing a parser that recognizes email addresses in an html
document, in order to obfuscate them.
This is a slightly simplified version of my current grammar :
main : |*
((email_chars+) >email_start ('.' email_chars+ )* '@' @email_confirmed
(domain_part '.')+ domain_part) $email_max => email_end;
# turn off email scanning until the end of the tag
'<' html_tag => { RESET(); fgoto tag; };
# turn off email scanning until the end of the comment
'<--' => { RESET(); fgoto comment; };
any => { RESET(); }
*|;
email_chars = [a-zA-Z0-9#&+~_\-];
domain_part = [a-zA-Z0-9] ([a-zA-Z0-9\-]* [a-zA-Z0-9])?;
RESET(); is a macro to reset some internal tracking variables (set by
actions such as email_start, email_confirmed, etc...).
html_tag is the list of all possible html tags.
When I transform this into the pure state machine I described earlier
(all expressions unioned and wrapped with a kleene star),
Some email don't match anymore, and I get parse errors.
It works currently, but I think if I could suppress the need for
backtracking, the performances could really improve.
Thanks,
Matthieu.
On Tue, Feb 23, 2010 at 6:24 AM, Adrian Thurston
<[email protected] <mailto:[email protected]>> wrote:
Matthieu Tourne wrote:
I've tried that without much success, I have a union with all my
scanner patterns, wrapped in ()**.
I have also replaced all the => { do_stuff(); } in the scanner
with @{ do_stuff(); } for each pattern.
If you want, post the specifics and we might be able to nail down
the problem.
So, I'm back to using a scanner construction, but resetting the
backtracking in between buffers, and it seems to work fine.
Are there any concerns with doing something like that ?
No.
-Adrian
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Matthieu Tourne
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