Difficulty with Logic parsing ICAL feed

[ChocolateCake]

I have been working on a code that will parse event information from an Ical feed. It is a huge block of data that I want to divide by key term. I need it to be done in an orderly way. I tried indexing the key terms and then having the program print what is between those indexes. However for some reason it became in infinite loop that printed all the data. I don't know how to fix it. DO NOT RUN MY CODE IT KEEPS FREEZING MY COMPUTER. I was hoping someone could show me what my problem is.

 DO NOT RUN THIS PROGRAM

use strict;
use warnings;


use LWP::Simple;
use HTML::TreeBuilder;
use HTML::FormatText;

my $URL= get("https://www.events.utoronto.ca/iCal.php?ical=1&campus=0&
+sponsor%5B%5D=&audience%5B%5D=&category%5B%5D=");

my $Format=HTML::FormatText->new;
my $TreeBuilder=HTML::TreeBuilder->new;
 $TreeBuilder->parse($URL);
my $Parsed=$Format->format($TreeBuilder);
open(FILE, ">UOTSUMMER.txt");
print FILE "$Parsed";
close (FILE);

open (FILE, "UOTSUMMER.txt");
my @array=<FILE>;

my $string ="@array";
my $offset = 0;     # Where are we in the string?


my $numResults = 0;

while (1) {
    my $idxSummary = index($string, "SUMMARY", $offset);
    my $result = "";
    my $idxDescription = index ($string, "DESCRIPTION", $offset);
    my $result2= "";
    if ($idxSummary > -1) {
        $offset = $idxSummary + length("SUMMARY");
        my $idxDescription = index($string, "DESCRIPTION", $offset);
        if ($idxDescription == -1) {
            print "(Data malformed: missing DESCRIPTION line.)\n";
            last;
        }
    if ($idxDescription > -1) {
        $offset = $idxDescription+ length("DESCRIPTION");
        my $idxLocation= index($string, "LOCATION", $offset);
        if ($idxLocation == -1) {
            print "(Data malformed: missing LOCATION line.)\n";
            last;
        } 
        
       my $length = $idxDescription - $offset;
        my $length2= $idxLocation - $offset;
        $result = substr($string, $offset, $length);
        $result2= substr ($string, $offset, $length2);
  
        $offset = $idxDescription + length("DESCRIPTION");
        $result =~ s/^\s+|\s+$//g ; # Strip leading and trailing white
#+space,
 $result2 =~ s/^\s+|\s+$//g ; 
                                    # includng newlines.
        $numResults++;
    } else { 
        print "(All done. $numResults result(s) found.)\n";
        last;
    }
   
open (FILE2, "UOT123.txt")
print FILE2 "TITLE: <$result>\n DESCRIPTION: <$result2>\n";

Any guidance you may have will be greatly appreciated! Thanks!

[roboticus]

ChocolateCake:

It looks like it doesn't find "SUMMARY", so it keeps resetting $offset to the same location--character 10: -1 + length("DESCRIPTION"). I'd suggest terminating the loop if it can't find SUMMARY or DESCRIPTION.

...roboticus

When your only tool is a hammer, all problems look like your thumb.

[ChocolateCake]

THANK YOU!! YOU FIXED MY PROBLEM AND MY CODE WORKS!! BEST FEELING IN THE WORLD!!

[roboticus]

ChocolateCake:

I should've mentioned: If you're having trouble with a loop like this, you might find it helpful to print the "interesting" variables (e.g. $offset) at the top of the loop. For example:

while (1) {
    my $idxSummary = index($string, "SUMMARY", $offset);
    my $result = "";
    my $idxDescription = index ($string, "DESCRIPTION", $offset);
    my $result2= "";
    print "idxSum:$idxSummary, idxDesc:$idxDescriptioni, offs:$offset\
+n";

Then I'd imagine you'd see something like:

idxSum:47, idxDesc: 62, offs:0
idxSum:122, idxDesc: 143, offs:73
idxSum:-1, idxDesc:-1, offs:10
idxSum:-1, idxDesc:-1, offs:10
.....

Then you'd probably figure it processed the first two records, and had a problem with the third. I didn't download your code, nor the ICAL url or anything, so the numbers are entirely fictitious.

...roboticus

When your only tool is a hammer, all problems look like your thumb.

[davido]

Crossposted on Stack Overflow: http://stackoverflow.com/q/12009527/716443

There's nothing wrong with minimal crossposting. But it's polite and useful to link to the other copies so that people don't put effort into a question that already has a solution elsewhere, and so that the collaborative effort can be based on responses from all incarnations of the question.

[ChocolateCake]

You are absolutely right, I am new to this and don't know the proper etiquette. Thank you for sharing that with me! How do I link the crosspost?

[MidLifeXis]

See What shortcuts can I use for linking to other information?.

[tobyink]

Why on earth are you parsing iCalendar by hand? Use Text::vFile::asData.

[davido]

If you don't have https support installed this line will be a problem (maybe you do, as it's not the problem you're posting about):

my $URL= get("https://www.events.utoronto.ca/iCal.php?ical=1&campus=0&sponsor%5­B%5D=&audience%5B%5D=&category%5B%5D=");

You should be checking the return value from LWP::Simple::get(). If it's undef, you didn't get a successful response. In this case you can solve the this part of the problem simply by switching to http:// instead of https://, or by installing LWP::Protocol::https. But still get in the habit of checking for undef after using LWP::Simple::get.

You should be able to enable https support in LWP::Simple by following the advice in the README for LWP:

If you want to access sites using the https protocol, then you need to install the LWP::Protocol::https module from CPAN.

Once this is done, LWP::Simple is able to fetch the https request. (And maybe you've done this already).