HTML::Gumbo(3)

NAME
HTML::Gumbo - HTML5 parser based on gumbo C library

SYNOPSIS
    use HTML::Gumbo;
    say HTML::Gumbo->new->parse('<div></div>');

    say HTML::Gumbo->new->parse('<h1>Hello</h1>', format => 'tree')->as_HTML;

DESCRIPTION
Gumbo <https://github.com/google/gumbo-parser> is an implementation of the HTML5 parsing algorithm <http://www.w3.org/TR/html5/syntax.html> implemented as a pure C99 library with no outside dependencies.

Goals and features of the C library:

•   Fully conformant with the HTML5 spec.

•   Robust and resilient to bad input.

•   Simple API that can be easily wrapped by other languages. (This is one of such wrappers.)

•   Support for source locations and pointers back to the original text. (Not exposed by this implementation at the moment.)

•   Relatively lightweight, with no outside dependencies.

•   Passes all html5lib-0.95 tests.

•   Tested on over 2.5 billion pages from Google's index.

METHODS

  new
    my $parser = HTML::Gumbo->new;

No options at the moment.

  parse
    my $res = $parser->parse(
        "<h1>hello world!</h1>",
        format => 'tree',
        input_is => 'string',
    );

Takes html string and pairs of named arguments:

format
    Output format, default is string. See "SUPPORTED OUTPUT FORMATS".

fragment_namespace
    Enables fragments parsing algorithm. Pass either 'HTML', 'SVG' or 'MATHML' to enable and set namespace. Without this input is parsed as html document, so html, head, title and body tags are added if absent.

    Note that fragment_enclosing_tag is set to '<body>' and can not be changed at the moment. Feel free to send patches implementing this part.

    See "SUPPORTED OUTPUT FORMATS" for additional details.

    Note that SVG and MATHML parsing is not tested, feel free to file bug reports with tests in case it doesn't work.

input_is
    Whether html is perl 'string', 'octets' or 'utf8' (octets known to be utf8). See "CHARACTER ENCODING OF THE INPUT".

encoding, encoding_content_type, encoding_tentative
    See "CHARACTER ENCODING OF THE INPUT".

... Some formatters may have additional arguments, see "SUPPORTED OUTPUT FORMATS"

Return value depends on the picked format.

SUPPORTED OUTPUT FORMATS

  string
HTML is parsed and re-built from the tree, so tags are balanced (except void elements).

No additional arguments specific for this format.

    $html = HTML::Gumbo->new->parse( $html );

  callback
HTML::Parser like interface. Pass a sub as "callback" argument to "parse" method and it will be called for every node in the document:

    HTML::Gumbo->new->parse( $html, format => 'callback', callback => sub {
        my ($event) = shift;
        if ( $event eq 'document start' ) {
            my ($doctype) = @_;
        }
        elsif ( $event eq 'document end' ) {
        }
        elsif ( $event eq 'start' ) {
            my ($tag, $attrs) = @_;
        }
        elsif ( $event eq 'end' ) {
            my ($tag) = @_;
        }
        elsif ( $event =~ /^(text|space|cdata|comment)$/ ) {
            my ($text) = @_;
        }
        else {
            die "Unknown event";
        }
    } );

Note that 'end' events are not generated for void elements <http://www.w3.org/TR/html5/syntax.html#void-elements>, for example "hr", "br" and "img".

No additional arguments except mentioned "callback".

Fragment parsing still generates 'document start' and 'document end' events what can be handy to initialize your parsing callback.

  tree
Alpha stage.

Produces tree based on HTML::Elements, like HTML::TreeBuilder.

There is major difference from HTML::TreeBuilder, this method produces top level element with tag name 'document' which may have doctype, comments and html tags as children.

Fragments parsing still produces top level 'document' element as fragment can be a list of tags, for example: '<p>hello</p><p>world</p'.

Yes, it's not ready to use as drop in replacement of tree builder. Patches are wellcome as I don't use this formatter at the moment. Note that it's hard to get rid of top level element because of situations described above. So not bad idea is to write HTML::Gumbo::Document class that is either subclass of HTML::Element or implements a small subset of methods of HTML::Element.

CHARACTER ENCODING OF THE INPUT
The C parser works only with UTF-8, so you have several options to make sure input is UTF-8. First of all define "input_is" argument:

string
    Input is Perl string, for example obtained from "decoded_content" in HTTP::Response. Default value.

        $gumbo->parse( decode_utf8($octets) );

octets
    Input are octets. Partial implementation of encoding sniffing algorithm <http://www.w3.org/TR/html5/syntax.html#encoding-sniffing-algorithm> is used. First thing wins:

    "encoding" argument
        Use it to hardcode a specific encoding.

            $gumbo->parse( $octets, input_is => 'octets', encoding => 'latin-1' );

    BOM UTF-8/UTF-16 BOMs are checked.

    "encoding_content_type" argument
        Encdoning from rransport layer, charset in content-type header.

            $gumbo->parse( $octets, input_is => 'octets', encoding_content_type => 'latin-1' );

    Prescan
        Not implemented, follow issue 58 <https://github.com/google/gumbo-parser/issues/58>.

        HTML5 defines prescan algorithm <http://www.w3.org/TR/html5/syntax.html#prescan-a-byte-stream-to-determine-its-encoding> that extracts encoding from meta tags in the head.

        It would be cool to get it in the C library, but I will accept a patch that impements it in pure perl.

    "encoding_tentative" argument
        The likely encoding for this page, e.g. based on the encoding of the page when it was last visited.

            $gumbo->parse( $octets, input_is => 'octets', encoding_tentative => 'latin-1' );

    nested browsing context
        Not implemented. Fragment parsing with or without context is not implemented. Parser also has no origin information, so it wouldn't be implemented.

    autodetection
        Not implemented.

        Can be implemented using Encode::Detect::Detector. Patches are welcome.

    otherwise
        It dies.

"utf8"
    Use utf8 as input_is when you're sure input is UTF-8, but octets. No pre-processing at all. Should only be used on trusted input or when it's preprocessed already.

AUTHOR
Ruslan Zakirov <ruz@bestpractical.com>

Best Practical Solutions, LLC <modules@bestpractical.com>

BUGS
All bugs should be reported via email to: bug-HTML-Gumbo@rt.cpan.org <mailto:bug-HTML-Gumbo@rt.cpan.org>

Or via the web at: rt.cpan.org <http://rt.cpan.org/Public/Dist/Display.html?Name=HTML-Gumbo>.

LICENSE
Under the same terms as perl itself.