Beefy Boxes and Bandwidth Generously Provided by pair Networks
laziness, impatience, and hubris

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??

Hi monks,

I'm currently fixing a few bugs in Mail::IMAPClient that for whatever reason have gone unnoticed. One of these is that its fetch_hash() method can't handle a parenthesized value if contains parentheses. In other words, its not dealing with nested parentheses correctly.

A typical server response to a FETCH command might look something like this:

* 2 FETCH (UID 2 FLAGS (\Answered \Seen) INTERNALDATE "05-Jun-2008 0 +7:19:01 +1000" RFC822.SIZE 5144 BODYSTRUCTURE ("text" "plain" ("chars +et" "ISO-8859-1") NIL NIL "7bit" 2053 46 NIL ("inline" NIL) NIL NIL))

fetch_hash() seeks to turn that into the following hash:

"UID" => "2", "FLAGS" => "\Answered \Seen", "INTERNALDATE" => "05-Jun-2008 07:19:01 +1000", "RFC822.SIZE" => "5144", "BODYSTRUCTURE" => "text" "plain" ("charset" "ISO-8859-1") NIL NIL " +7bit" 2053 46 NIL ("inline" NIL) NIL NIL",

In other words, the parenthesized data consists of key/value pairs. The values are either simple strings (matched by \S+), quoted strings (matched by "[^"]*") or a parenthesized fragment, which may include parentheses itself.

What's inside the parentheses is actually completely opaque as far as this method is concerned. The original code used \([\)]*\) to try and match it, which works great until there is a closing paren inside.

My attempt matching/capturing the parenthesized fragment is based on mjd's regex to match balanced parentheses. Its actually part of a larger regex that matches the other stuff described above, but this doesn't work in isolation either so I don't think those things are affecting it:

(?: (?{ local $d=0 }) # set depth to 0 ( # start capture (?: \( # opening paren (?{$d++}) # increment the depth | \) # or closing paren (?{$d--}) # decrement the depth (?(?{$d==0}) # if we're back to the start (*ACCEPT) # we're done ) | (?>[^()]*) # or there's just some normal text )* (?(?{$d!=0}) # done. did we reach a matching closing paren (?!) # nope, failed ) ) # end capture )

Running a basic test program with -Mre=debug seems to suggest that this is doing something close to what I want, stopping when it gets to the correct closing paren. The only problem is that nothing gets captured, even though the description of (*ACCEPT) in perlre makes it sound like it should.

So, what's wrong here? And is there an easier way to do this? Note that I'm restricted to Perl 5.6, which sucks as I'd really like to try the PARNO stuff that came with 5.10.


In reply to Extracting a parenthesized fragment from a string by fce2

Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":

  • Are you posting in the right place? Check out Where do I post X? to know for sure.
  • Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
    <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
  • Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
  • Want more info? How to link or or How to display code and escape characters are good places to start.
Log In?

What's my password?
Create A New User
Domain Nodelet?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others making s'mores by the fire in the courtyard of the Monastery: (3)
As of 2022-08-11 00:17 GMT
Find Nodes?
    Voting Booth?

    No recent polls found