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package HTML::HeadParser;
=head1 NAME
HTML::HeadParser - Parse <HEAD> section of a HTML document
=head1 SYNOPSIS
require HTML::HeadParser;
$p = HTML::HeadParser->new;
$p->parse($text) and print "not finished";
$p->header('Title') # to access <title>....</title>
$p->header('Content-Base') # to access <base href="http://...">
$p->header('Foo') # to access <meta http-equiv="Foo" content="...">
$p->header('X-Meta-Author') # to access <meta name="author" content="...">
$p->header('X-Meta-Charset') # to access <meta charset="...">
=head1 DESCRIPTION
The C<HTML::HeadParser> is a specialized (and lightweight)
C<HTML::Parser> that will only parse the E<lt>HEAD>...E<lt>/HEAD>
section of an HTML document. The parse() method
will return a FALSE value as soon as some E<lt>BODY> element or body
text are found, and should not be called again after this.
Note that the C<HTML::HeadParser> might get confused if raw undecoded
UTF-8 is passed to the parse() method. Make sure the strings are
properly decoded before passing them on.
The C<HTML::HeadParser> keeps a reference to a header object, and the
parser will update this header object as the various elements of the
E<lt>HEAD> section of the HTML document are recognized. The following
header fields are affected:
=over 4
=item Content-Base:
The I<Content-Base> header is initialized from the E<lt>base
href="..."> element.
=item Title:
The I<Title> header is initialized from the E<lt>title>...E<lt>/title>
element.
=item Isindex:
The I<Isindex> header will be added if there is a E<lt>isindex>
element in the E<lt>head>. The header value is initialized from the
I<prompt> attribute if it is present. If no I<prompt> attribute is
given it will have '?' as the value.
=item X-Meta-Foo:
All E<lt>meta> elements containing a C<name> attribute will result in
headers using the prefix C<X-Meta-> appended with the value of the
C<name> attribute as the name of the header, and the value of the
C<content> attribute as the pushed header value.
E<lt>meta> elements containing a C<http-equiv> attribute will result
in headers as in above, but without the C<X-Meta-> prefix in the
header name.
E<lt>meta> elements containing a C<charset> attribute will result in
an C<X-Meta-Charset> header, using the value of the C<charset>
attribute as the pushed header value.
The ':' character can't be represented in header field names, so
if the meta element contains this char it's substituted with '-'
before forming the field name.
=back
=head1 METHODS
The following methods (in addition to those provided by the
superclass) are available:
=over 4
=cut
require HTML::Parser;
our @ISA = qw(HTML::Parser);
use HTML::Entities ();
use strict;
our $DEBUG;
#$DEBUG = 1;
our $VERSION = '3.81';
=item $hp = HTML::HeadParser->new
=item $hp = HTML::HeadParser->new( $header )
The object constructor. The optional $header argument should be a
reference to an object that implement the header() and push_header()
methods as defined by the C<HTTP::Headers> class. Normally it will be
of some class that is a or delegates to the C<HTTP::Headers> class.
If no $header is given C<HTML::HeadParser> will create an
C<HTTP::Headers> object by itself (initially empty).
=cut
sub new
{
my($class, $header) = @_;
unless ($header) {
require HTTP::Headers;
$header = HTTP::Headers->new;
}
my $self = $class->SUPER::new(api_version => 3,
start_h => ["start", "self,tagname,attr"],
end_h => ["end", "self,tagname"],
text_h => ["text", "self,text"],
ignore_elements => [qw(script style)],
);
$self->{'header'} = $header;
$self->{'tag'} = ''; # name of active element that takes textual content
$self->{'text'} = ''; # the accumulated text associated with the element
$self;
}
=item $hp->header;
Returns a reference to the header object.
=item $hp->header( $key )
Returns a header value. It is just a shorter way to write
C<$hp-E<gt>header-E<gt>header($key)>.
=cut
sub header
{
my $self = shift;
return $self->{'header'} unless @_;
$self->{'header'}->header(@_);
}
sub as_string # legacy
{
my $self = shift;
$self->{'header'}->as_string;
}
sub flush_text # internal
{
my $self = shift;
my $tag = $self->{'tag'};
my $text = $self->{'text'};
$text =~ s/^\s+//;
$text =~ s/\s+$//;
$text =~ s/\s+/ /g;
print "FLUSH $tag => '$text'\n" if $DEBUG;
if ($tag eq 'title') {
my $decoded;
$decoded = utf8::decode($text) if $self->utf8_mode && defined &utf8::decode;
HTML::Entities::decode($text);
utf8::encode($text) if $decoded;
$self->{'header'}->push_header(Title => $text);
}
$self->{'tag'} = $self->{'text'} = '';
}
# This is an quote from the HTML3.2 DTD which shows which elements
# that might be present in a <HEAD>...</HEAD>. Also note that the
# <HEAD> tags themselves might be missing:
#
# <!ENTITY % head.content "TITLE & ISINDEX? & BASE? & STYLE? &
# SCRIPT* & META* & LINK*">
#
# <!ELEMENT HEAD O O (%head.content)>
#
# From HTML 4.01:
#
# <!ENTITY % head.misc "SCRIPT|STYLE|META|LINK|OBJECT">
# <!ENTITY % head.content "TITLE & BASE?">
# <!ELEMENT HEAD O O (%head.content;) +(%head.misc;)>
#
# From HTML 5 as of WD-html5-20090825:
#
# One or more elements of metadata content, [...]
# => base, command, link, meta, noscript, script, style, title
sub start
{
my($self, $tag, $attr) = @_; # $attr is reference to a HASH
print "START[$tag]\n" if $DEBUG;
$self->flush_text if $self->{'tag'};
if ($tag eq 'meta') {
my $key = $attr->{'http-equiv'};
if (!defined($key) || !length($key)) {
if ($attr->{name}) {
$key = "X-Meta-\u$attr->{name}";
} elsif ($attr->{charset}) { # HTML 5 <meta charset="...">
$key = "X-Meta-Charset";
$self->{header}->push_header($key => $attr->{charset});
return;
} else {
return;
}
}
$key =~ s/:/-/g;
$self->{'header'}->push_header($key => $attr->{content});
} elsif ($tag eq 'base') {
return unless exists $attr->{href};
(my $base = $attr->{href}) =~ s/^\s+//; $base =~ s/\s+$//; # HTML5
$self->{'header'}->push_header('Content-Base' => $base);
} elsif ($tag eq 'isindex') {
# This is a non-standard header. Perhaps we should just ignore
# this element
$self->{'header'}->push_header(Isindex => $attr->{prompt} || '?');
} elsif ($tag =~ /^(?:title|noscript|object|command)$/) {
# Just remember tag. Initialize header when we see the end tag.
$self->{'tag'} = $tag;
} elsif ($tag eq 'link') {
return unless exists $attr->{href};
# <link href="http:..." rel="xxx" rev="xxx" title="xxx">
my $href = delete($attr->{href});
$href =~ s/^\s+//; $href =~ s/\s+$//; # HTML5
my $h_val = "<$href>";
for (sort keys %{$attr}) {
next if $_ eq "/"; # XHTML junk
$h_val .= qq(; $_="$attr->{$_}");
}
$self->{'header'}->push_header(Link => $h_val);
} elsif ($tag eq 'head' || $tag eq 'html') {
# ignore
} else {
# stop parsing
$self->eof;
}
}
sub end
{
my($self, $tag) = @_;
print "END[$tag]\n" if $DEBUG;
$self->flush_text if $self->{'tag'};
$self->eof if $tag eq 'head';
}
sub text
{
my($self, $text) = @_;
print "TEXT[$text]\n" if $DEBUG;
unless ($self->{first_chunk}) {
# drop Unicode BOM if found
if ($self->utf8_mode) {
$text =~ s/^\xEF\xBB\xBF//;
}
else {
$text =~ s/^\x{FEFF}//;
}
$self->{first_chunk}++;
}
my $tag = $self->{tag};
if (!$tag && $text =~ /\S/) {
# Normal text means start of body
$self->eof;
return;
}
return if $tag ne 'title';
$self->{'text'} .= $text;
}
BEGIN {
*utf8_mode = sub { 1 } unless HTML::Entities::UNICODE_SUPPORT;
}
1;
__END__
=back
=head1 EXAMPLE
$h = HTTP::Headers->new;
$p = HTML::HeadParser->new($h);
$p->parse(<<EOT);
<title>Stupid example</title>
<base href="http://www.linpro.no/lwp/">
Normal text starts here.
EOT
undef $p;
print $h->title; # should print "Stupid example"
=head1 SEE ALSO
L<HTML::Parser>, L<HTTP::Headers>
The C<HTTP::Headers> class is distributed as part of the
I<libwww-perl> package. If you don't have that distribution installed
you need to provide the $header argument to the C<HTML::HeadParser>
constructor with your own object that implements the documented
protocol.
=head1 COPYRIGHT
Copyright 1996-2001 Gisle Aas. All rights reserved.
This library is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.
=cut