Provided by: libhtml-simpleparse-perl_0.12-5_all 
NAME
HTML::SimpleParse - a bare-bones HTML parser
SYNOPSIS
use HTML::SimpleParse;
# Parse the text into a simple tree
my $p = new HTML::SimpleParse( $html_text );
$p->output; # Output the HTML verbatim
$p->text( $new_text ); # Give it some new HTML to chew on
$p->parse # Parse the new HTML
$p->output;
my %attrs = HTML::SimpleParse->parse_args('A="xx" B=3');
# %attrs is now ('A' => 'xx', 'B' => '3')
DESCRIPTION
This module is a simple HTML parser. It is similar in concept to HTML::Parser, but it
differs from HTML::TreeBuilder in a couple of important ways.
First, HTML::TreeBuilder knows which tags can contain other tags, which start tags have
corresponding end tags, which tags can exist only in the <HEAD> portion of the document,
and so forth. HTML::SimpleParse does not know any of these things. It just finds tags
and text in the HTML you give it, it does not care about the specific content of these
tags (though it does distiguish between different _types_ of tags, such as comments,
starting tags like <b>, ending tags like </b>, and so on).
Second, HTML::SimpleParse does not create a hierarchical tree of HTML content, but rather
a simple linear list. It does not pay any attention to balancing start tags with
corresponding end tags, or which pairs of tags are inside other pairs of tags.
Because of these characteristics, you can make a very effective HTML filter by sub-
classing HTML::SimpleParse. For example, to remove all comments from HTML:
package NoComment;
use HTML::SimpleParse;
@ISA = qw(HTML::SimpleParse);
sub output_comment {}
package main;
NoComment->new($some_html)->output;
Historically, I started the HTML::SimpleParse project in part because of a
misunderstanding about HTML::Parser's functionality. Many aspects of these two modules
actually overlap. I continue to maintain the HTML::SimpleParse module because people seem
to be depending on it, and because beginners sometimes find HTML::SimpleParse to be
simpler than HTML::Parser's more powerful interface. People also seem to get a fair
amount of usage out of the "parse_args()" method directly.
Methods
• new
$p = new HTML::SimpleParse( $some_html );
Creates a new HTML::SimpleParse object. Optionally takes one argument, a string
containing some HTML with which to initialize the object. If you give it a non-empty
string, the HTML will be parsed into a tree and ready for outputting.
Can also take a list of attributes, such as
$p = new HTML::SimpleParse( $some_html, 'fix_case' => -1);
See the "parse_args()" method below for an explanation of this attribute.
• text
$text = $p->text;
$p->text( $new_text );
Get or set the contents of the HTML to be parsed.
• tree
foreach ($p->tree) { ... }
Returns a list of all the nodes in the tree, in case you want to step through them
manually or something. Each node in the tree is an anonymous hash with (at least)
three data members, $node->{type} (is this a comment, a start tag, an end tag, etc.),
$node->{content} (all the text between the angle brackets, verbatim), and
$node->{offset} (number of bytes from the beginning of the string).
The possible values of $node->{type} are "text", "starttag", "endtag", "ssi", and
"markup".
• parse
$p->parse;
Once an object has been initialized with some text, call $p->parse and a tree will be
created. After the tree is created, you can call $p->output. If you feed some text
to the new() method, parse will be called automatically during your object's
construction.
• parse_args
%hash = $p->parse_args( $arg_string );
This routine is handy for parsing the contents of an HTML tag into key=value pairs.
For instance:
$text = 'type=checkbox checked name=flavor value="chocolate or strawberry"';
%hash = $p->parse_args( $text );
# %hash is ( TYPE=>'checkbox', CHECKED=>undef, NAME=>'flavor',
# VALUE=>'chocolate or strawberry' )
Note that the position of the last m//g search on the string (the value returned by
Perl's pos() function) will be altered by the parse_args function, so make sure you
take that into account if (in the above example) you do "$text =~ m/something/g".
The parse_args() method can be run as either an object method or as a class method,
i.e. as either $p->parse_args(...) or HTML::SimpleParse->parse_args(...).
HTML attribute lists are supposed to be case-insensitive with respect to attribute
names. To achieve this behavior, parse_args() respects the 'fix_case' flag, which can
be set either as a package global $FIX_CASE, or as a class member datum 'fix_case'.
If set to 0, no case conversion is done. If set to 1, all keys are converted to upper
case. If set to -1, all keys are converted to lower case. The default is 1, i.e. all
keys are uppercased.
If an attribute takes no value (like "checked" in the above example) then it will
still have an entry in the returned hash, but its value will be "undef". For example:
%hash = $p->parse_args('type=checkbox checked name=banana value=""');
# $hash{CHECKED} is undef, but $hash{VALUE} is ""
This method actually returns a list (not a hash), so duplicate attributes and order
will be preserved if you want them to be:
@hash = $p->parse_args("name=family value=gwen value=mom value=pop");
# @hash is qw(NAME family VALUE gwen VALUE mom VALUE pop)
• output
$p->output;
This will output the contents of the HTML, passing the real work off to the
output_text, output_comment, etc. functions. If you do not override any of these
methods, this module will output the exact text that it parsed into a tree in the
first place.
• get_output
print $p->get_output
Similar to $p->output(), but returns its result instead of printing it.
• execute
foreach ($p->tree) {
print $p->execute($_);
}
Executes a single node in the HTML parse tree. Useful if you want to loop through the
nodes and output them individually.
The following methods do the actual outputting of the various parts of the HTML. Override
some of them if you want to change the way the HTML is output. For instance, to strip
comments from the HTML, override the output_comment method like so:
# In subclass:
sub output_comment { } # Does nothing
• output_text
• output_comment
• output_endtag
• output_starttag
• output_markup
• output_ssi
CAVEATS
Please do not assume that the interface here is stable. This is a first pass, and I'm
still trying to incorporate suggestions from the community. If you employ this module
somewhere, make doubly sure before upgrading that none of your code breaks when you use
the newer version.
BUGS
• Embedded >s are broken
Won't handle tags with embedded >s in them, like <input name=expr value="x > y">.
This will be fixed in a future version, probably by using the parse_args method.
Suggestions are welcome.
TO DO
• extensibility
Based on a suggestion from Randy Harmon (thanks), I'd like to make it easier for
subclasses of SimpleParse to pick out other kinds of HTML blocks, i.e. extend the set
{text, comment, endtag, starttag, markup, ssi} to include more members. Currently the
only easy way to do that is by overriding the "parse" method:
sub parse { # In subclass
my $self = $_[0];
$self->SUPER::parse(@_);
foreach ($self->tree) {
if ($_->{content} =~ m#^a\s+#i) {
$_->{type} = 'anchor_start';
}
}
}
sub output_anchor_start {
# Whatever you want...
}
Alternatively, this feature might be implemented by hanging attatchments onto the
parsing loop, like this:
my $parser = new SimpleParse( $html_text );
$regex = '<(a\s+.*?)>';
$parser->watch_for( 'anchor_start', $regex );
sub SimpleParse::output_anchor_start {
# Whatever you want...
}
I think I like that idea better. If you wanted to, you could make a subclass with
output_anchor_start as one of its methods, and put the ->watch_for stuff in the
constructor.
• reading from filehandles
It would be nice if you could initialize an object by giving it a filehandle or
filename instead of the text itself.
• tests
I need to write a few tests that run under "make test".
AUTHOR
Ken Williams <ken@forum.swarthmore.edu>
COPYRIGHT
Copyright 1998 Swarthmore College. All rights reserved.
This library is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.