Jonathan Rockway
and 1 contributors

NAME

Algorithm::IncludeExclude - build and evaluate include/exclude lists

VERSION

Version 0.01

SYNOPSIS

Algorithm::IncludeExclude lets you define a tree of include / exclude rules and then allows you to determine the best rule for a given path.

For example, to include everything, then exclude everything under bar or baz but then include everything under foo baz, you could write:

   my $ie = Algorithm::IncludeExclude->new;
   
   # setup rules
   $ie->include();                      # default to include
   $ie->exclude('foo');
   $ie->exclude('bar');
   $ie->include(qw/foo baz/);

   # evaluate candidates
   $ie->evaluate(qw/foo bar/);          # exclude (due to 'foo' rule)
   $ie->evaluate(qw/bar baz/);          # exclude (due to 'bar' rule)
   $ie->evaluate(qw/quux foo bar/);     # include (due to '' rule)
   $ie->evaluate(qw/foo baz quux/);     # include (due to 'foo/baz' rule)

You can also match against regexes. Let's imagine you want to exclude everything in the admin directory, as well as all files that end with a .protected extension.

Here's how to implement that:

   my $ie = Algorithm::IncludeExclude->new;
   $ie->exclude('admin');
   $ie->exclude(qr/[.]protected$/);

   $ie->evaluate(qw/admin let me in/);  # exclude (due to 'admin' rule)
   $ie->evaluate(qw/a path.protected/); # exclude (due to regex)
   $ie->evaluate(qw/foo bar/);          # undefined (no rule matches)

   $ie->include(qw/foo bar/);
   $ie->evaluate(qw/foo bar/);          # now it's included

If you wanted to include files inside the admin path ending in .ok, you could just add this rule:

   $ie->include('admin', qr/[.]ok$/);
   $ie->evaluate(qw/admin super public records.ok/); # included

The most specific match always wins -- if there's not an exact match, the nearest match is chosen instead.

NOTES

  • Regexes can only appear as the last element in a rule:

       $ie->include(qr/foo/, qr/bar/);
       $ie->exclude(qr/foo/, qr/bar/);

    If regexes were allowed anywhere, things could get very confusing, very quickly.

  • Regexes are matched against any remaining path elements when they are first encountered. In the following example:

       $ie->include('foo', qr/bar/);
       $ie->evaluate('foo', 'baz', 'quux', 'bar'); # include

    The match works like this. First, 'foo' (from the include rule) and 'foo' (from the path being evaluated) are compared. Since there's a match, the next element in the path is examined against foo's subtree. The only remaining item in the rule tree is a regex, so the regex is compared to the rest of the path being evaluated, joined by the join argument to new (see "METHODS/new"); namely:

       baz/quux/bar

    Since the regular expression matches this string, the include rule is matched.

  • Regex rules are checked before non-regex rules. For example:

      $ie->exclude('foo', 'bar');
      $ie->include(qr/bar/);
    
      $ie->evaluate('foo', 'bar'); # include, due to regex
  • If two or more regular expressions at the same level match a path, the result is undefined:

      $ie->include(qr/foo/);
      $ie->exclude(qr/bar/);
     
      $ie->evaluate('foobar'); # undef is returned

METHODS

new

Create a new instance. Accepts an optional hashref of arguments. The arguments may be:

join

String to join remaining path elements with when matching against a regex. Defaults to /, which is good for matching against URLs or filesystem paths.

include(@path)

Add an include path to the rule tree. @path may end with a regex.

exclude(@path)

Add an exclude path to the rule tree. @path may end with a regex.

evaluate(@path)

Evaluate whether @path should be included (true) or excluded (false). If the include/exclude status cannot be determined (no rules match, more than one regex matches), undef is returned.

AUTHOR

Jonathan Rockway, <jrockway at cpan.org>

BUGS

Please report any bugs or feature requests to bug-algorithm-includeexclude at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Algorithm-IncludeExclude. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT

You can find documentation for this module with the perldoc command.

    perldoc Algorithm::IncludeExclude

You can also look for information at:

ACKNOWLEDGEMENTS

COPYRIGHT & LICENSE

Copyright 2007 Jonathan Rockway, all rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.