1<?php
2
3/**
4 * Proof-of-concept lexer that uses the PEAR package XML_HTMLSax3 to parse HTML.
5 *
6 * PEAR, not suprisingly, also has a SAX parser for HTML.  I don't know
7 * very much about implementation, but it's fairly well written.  However, that
8 * abstraction comes at a price: performance. You need to have it installed,
9 * and if the API changes, it might break our adapter. Not sure whether or not
10 * it's UTF-8 aware, but it has some entity parsing trouble (in all areas,
11 * text and attributes).
12 *
13 * Quite personally, I don't recommend using the PEAR class, and the defaults
14 * don't use it. The unit tests do perform the tests on the SAX parser too, but
15 * whatever it does for poorly formed HTML is up to it.
16 *
17 * @todo Generalize so that XML_HTMLSax is also supported.
18 *
19 * @warning Entity-resolution inside attributes is broken.
20 */
21
22class HTMLPurifier_Lexer_PEARSax3 extends HTMLPurifier_Lexer
23{
24
25    /**
26     * Internal accumulator array for SAX parsers.
27     */
28    protected $tokens = array();
29    protected $last_token_was_empty;
30
31    private $parent_handler;
32    private $stack = array();
33
34    public function tokenizeHTML($string, $config, $context) {
35
36        $this->tokens = array();
37        $this->last_token_was_empty = false;
38
39        $string = $this->normalize($string, $config, $context);
40
41        $this->parent_handler = set_error_handler(array($this, 'muteStrictErrorHandler'));
42
43        $parser = new XML_HTMLSax3();
44        $parser->set_object($this);
45        $parser->set_element_handler('openHandler','closeHandler');
46        $parser->set_data_handler('dataHandler');
47        $parser->set_escape_handler('escapeHandler');
48
49        // doesn't seem to work correctly for attributes
50        $parser->set_option('XML_OPTION_ENTITIES_PARSED', 1);
51
52        $parser->parse($string);
53
54        restore_error_handler();
55
56        return $this->tokens;
57
58    }
59
60    /**
61     * Open tag event handler, interface is defined by PEAR package.
62     */
63    public function openHandler(&$parser, $name, $attrs, $closed) {
64        // entities are not resolved in attrs
65        foreach ($attrs as $key => $attr) {
66            $attrs[$key] = $this->parseData($attr);
67        }
68        if ($closed) {
69            $this->tokens[] = new HTMLPurifier_Token_Empty($name, $attrs);
70            $this->last_token_was_empty = true;
71        } else {
72            $this->tokens[] = new HTMLPurifier_Token_Start($name, $attrs);
73        }
74        $this->stack[] = $name;
75        return true;
76    }
77
78    /**
79     * Close tag event handler, interface is defined by PEAR package.
80     */
81    public function closeHandler(&$parser, $name) {
82        // HTMLSax3 seems to always send empty tags an extra close tag
83        // check and ignore if you see it:
84        // [TESTME] to make sure it doesn't overreach
85        if ($this->last_token_was_empty) {
86            $this->last_token_was_empty = false;
87            return true;
88        }
89        $this->tokens[] = new HTMLPurifier_Token_End($name);
90        if (!empty($this->stack)) array_pop($this->stack);
91        return true;
92    }
93
94    /**
95     * Data event handler, interface is defined by PEAR package.
96     */
97    public function dataHandler(&$parser, $data) {
98        $this->last_token_was_empty = false;
99        $this->tokens[] = new HTMLPurifier_Token_Text($data);
100        return true;
101    }
102
103    /**
104     * Escaped text handler, interface is defined by PEAR package.
105     */
106    public function escapeHandler(&$parser, $data) {
107        if (strpos($data, '--') === 0) {
108            // remove trailing and leading double-dashes
109            $data = substr($data, 2);
110            if (strlen($data) >= 2 && substr($data, -2) == "--") {
111                $data = substr($data, 0, -2);
112            }
113            if (isset($this->stack[sizeof($this->stack) - 1]) &&
114                $this->stack[sizeof($this->stack) - 1] == "style") {
115                $this->tokens[] = new HTMLPurifier_Token_Text($data);
116            } else {
117                $this->tokens[] = new HTMLPurifier_Token_Comment($data);
118            }
119            $this->last_token_was_empty = false;
120        }
121        // CDATA is handled elsewhere, but if it was handled here:
122        //if (strpos($data, '[CDATA[') === 0) {
123        //    $this->tokens[] = new HTMLPurifier_Token_Text(
124        //        substr($data, 7, strlen($data) - 9) );
125        //}
126        return true;
127    }
128
129    /**
130     * An error handler that mutes strict errors
131     */
132    public function muteStrictErrorHandler($errno, $errstr, $errfile=null, $errline=null, $errcontext=null) {
133        if ($errno == E_STRICT) return;
134        return call_user_func($this->parent_handler, $errno, $errstr, $errfile, $errline, $errcontext);
135    }
136
137}
138
139// vim: et sw=4 sts=4
140