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010efc9b AD |
1 | <?php |
2 | ||
3 | /** | |
4 | * A UTF-8 specific character encoder that handles cleaning and transforming. | |
5 | * @note All functions in this class should be static. | |
6 | */ | |
7 | class HTMLPurifier_Encoder | |
8 | { | |
9 | ||
10 | /** | |
11 | * Constructor throws fatal error if you attempt to instantiate class | |
12 | */ | |
13 | private function __construct() { | |
14 | trigger_error('Cannot instantiate encoder, call methods statically', E_USER_ERROR); | |
15 | } | |
16 | ||
17 | /** | |
18 | * Error-handler that mutes errors, alternative to shut-up operator. | |
19 | */ | |
20 | public static function muteErrorHandler() {} | |
21 | ||
010efc9b AD |
22 | /** |
23 | * Cleans a UTF-8 string for well-formedness and SGML validity | |
24 | * | |
25 | * It will parse according to UTF-8 and return a valid UTF8 string, with | |
26 | * non-SGML codepoints excluded. | |
27 | * | |
28 | * @note Just for reference, the non-SGML code points are 0 to 31 and | |
29 | * 127 to 159, inclusive. However, we allow code points 9, 10 | |
30 | * and 13, which are the tab, line feed and carriage return | |
31 | * respectively. 128 and above the code points map to multibyte | |
32 | * UTF-8 representations. | |
33 | * | |
34 | * @note Fallback code adapted from utf8ToUnicode by Henri Sivonen and | |
35 | * hsivonen@iki.fi at <http://iki.fi/hsivonen/php-utf8/> under the | |
36 | * LGPL license. Notes on what changed are inside, but in general, | |
37 | * the original code transformed UTF-8 text into an array of integer | |
38 | * Unicode codepoints. Understandably, transforming that back to | |
39 | * a string would be somewhat expensive, so the function was modded to | |
40 | * directly operate on the string. However, this discourages code | |
41 | * reuse, and the logic enumerated here would be useful for any | |
42 | * function that needs to be able to understand UTF-8 characters. | |
43 | * As of right now, only smart lossless character encoding converters | |
44 | * would need that, and I'm probably not going to implement them. | |
45 | * Once again, PHP 6 should solve all our problems. | |
46 | */ | |
47 | public static function cleanUTF8($str, $force_php = false) { | |
48 | ||
49 | // UTF-8 validity is checked since PHP 4.3.5 | |
50 | // This is an optimization: if the string is already valid UTF-8, no | |
51 | // need to do PHP stuff. 99% of the time, this will be the case. | |
52 | // The regexp matches the XML char production, as well as well as excluding | |
53 | // non-SGML codepoints U+007F to U+009F | |
54 | if (preg_match('/^[\x{9}\x{A}\x{D}\x{20}-\x{7E}\x{A0}-\x{D7FF}\x{E000}-\x{FFFD}\x{10000}-\x{10FFFF}]*$/Du', $str)) { | |
55 | return $str; | |
56 | } | |
57 | ||
58 | $mState = 0; // cached expected number of octets after the current octet | |
59 | // until the beginning of the next UTF8 character sequence | |
60 | $mUcs4 = 0; // cached Unicode character | |
61 | $mBytes = 1; // cached expected number of octets in the current sequence | |
62 | ||
63 | // original code involved an $out that was an array of Unicode | |
64 | // codepoints. Instead of having to convert back into UTF-8, we've | |
65 | // decided to directly append valid UTF-8 characters onto a string | |
66 | // $out once they're done. $char accumulates raw bytes, while $mUcs4 | |
67 | // turns into the Unicode code point, so there's some redundancy. | |
68 | ||
69 | $out = ''; | |
70 | $char = ''; | |
71 | ||
72 | $len = strlen($str); | |
73 | for($i = 0; $i < $len; $i++) { | |
74 | $in = ord($str{$i}); | |
75 | $char .= $str[$i]; // append byte to char | |
76 | if (0 == $mState) { | |
77 | // When mState is zero we expect either a US-ASCII character | |
78 | // or a multi-octet sequence. | |
79 | if (0 == (0x80 & ($in))) { | |
80 | // US-ASCII, pass straight through. | |
81 | if (($in <= 31 || $in == 127) && | |
82 | !($in == 9 || $in == 13 || $in == 10) // save \r\t\n | |
83 | ) { | |
84 | // control characters, remove | |
85 | } else { | |
86 | $out .= $char; | |
87 | } | |
88 | // reset | |
89 | $char = ''; | |
90 | $mBytes = 1; | |
91 | } elseif (0xC0 == (0xE0 & ($in))) { | |
92 | // First octet of 2 octet sequence | |
93 | $mUcs4 = ($in); | |
94 | $mUcs4 = ($mUcs4 & 0x1F) << 6; | |
95 | $mState = 1; | |
96 | $mBytes = 2; | |
97 | } elseif (0xE0 == (0xF0 & ($in))) { | |
98 | // First octet of 3 octet sequence | |
99 | $mUcs4 = ($in); | |
100 | $mUcs4 = ($mUcs4 & 0x0F) << 12; | |
101 | $mState = 2; | |
102 | $mBytes = 3; | |
103 | } elseif (0xF0 == (0xF8 & ($in))) { | |
104 | // First octet of 4 octet sequence | |
105 | $mUcs4 = ($in); | |
106 | $mUcs4 = ($mUcs4 & 0x07) << 18; | |
107 | $mState = 3; | |
108 | $mBytes = 4; | |
109 | } elseif (0xF8 == (0xFC & ($in))) { | |
110 | // First octet of 5 octet sequence. | |
111 | // | |
112 | // This is illegal because the encoded codepoint must be | |
113 | // either: | |
114 | // (a) not the shortest form or | |
115 | // (b) outside the Unicode range of 0-0x10FFFF. | |
116 | // Rather than trying to resynchronize, we will carry on | |
117 | // until the end of the sequence and let the later error | |
118 | // handling code catch it. | |
119 | $mUcs4 = ($in); | |
120 | $mUcs4 = ($mUcs4 & 0x03) << 24; | |
121 | $mState = 4; | |
122 | $mBytes = 5; | |
123 | } elseif (0xFC == (0xFE & ($in))) { | |
124 | // First octet of 6 octet sequence, see comments for 5 | |
125 | // octet sequence. | |
126 | $mUcs4 = ($in); | |
127 | $mUcs4 = ($mUcs4 & 1) << 30; | |
128 | $mState = 5; | |
129 | $mBytes = 6; | |
130 | } else { | |
131 | // Current octet is neither in the US-ASCII range nor a | |
132 | // legal first octet of a multi-octet sequence. | |
133 | $mState = 0; | |
134 | $mUcs4 = 0; | |
135 | $mBytes = 1; | |
136 | $char = ''; | |
137 | } | |
138 | } else { | |
139 | // When mState is non-zero, we expect a continuation of the | |
140 | // multi-octet sequence | |
141 | if (0x80 == (0xC0 & ($in))) { | |
142 | // Legal continuation. | |
143 | $shift = ($mState - 1) * 6; | |
144 | $tmp = $in; | |
145 | $tmp = ($tmp & 0x0000003F) << $shift; | |
146 | $mUcs4 |= $tmp; | |
147 | ||
148 | if (0 == --$mState) { | |
149 | // End of the multi-octet sequence. mUcs4 now contains | |
150 | // the final Unicode codepoint to be output | |
151 | ||
152 | // Check for illegal sequences and codepoints. | |
153 | ||
154 | // From Unicode 3.1, non-shortest form is illegal | |
155 | if (((2 == $mBytes) && ($mUcs4 < 0x0080)) || | |
156 | ((3 == $mBytes) && ($mUcs4 < 0x0800)) || | |
157 | ((4 == $mBytes) && ($mUcs4 < 0x10000)) || | |
158 | (4 < $mBytes) || | |
159 | // From Unicode 3.2, surrogate characters = illegal | |
160 | (($mUcs4 & 0xFFFFF800) == 0xD800) || | |
161 | // Codepoints outside the Unicode range are illegal | |
162 | ($mUcs4 > 0x10FFFF) | |
163 | ) { | |
164 | ||
165 | } elseif (0xFEFF != $mUcs4 && // omit BOM | |
166 | // check for valid Char unicode codepoints | |
167 | ( | |
168 | 0x9 == $mUcs4 || | |
169 | 0xA == $mUcs4 || | |
170 | 0xD == $mUcs4 || | |
171 | (0x20 <= $mUcs4 && 0x7E >= $mUcs4) || | |
172 | // 7F-9F is not strictly prohibited by XML, | |
173 | // but it is non-SGML, and thus we don't allow it | |
174 | (0xA0 <= $mUcs4 && 0xD7FF >= $mUcs4) || | |
175 | (0x10000 <= $mUcs4 && 0x10FFFF >= $mUcs4) | |
176 | ) | |
177 | ) { | |
178 | $out .= $char; | |
179 | } | |
180 | // initialize UTF8 cache (reset) | |
181 | $mState = 0; | |
182 | $mUcs4 = 0; | |
183 | $mBytes = 1; | |
184 | $char = ''; | |
185 | } | |
186 | } else { | |
187 | // ((0xC0 & (*in) != 0x80) && (mState != 0)) | |
188 | // Incomplete multi-octet sequence. | |
189 | // used to result in complete fail, but we'll reset | |
190 | $mState = 0; | |
191 | $mUcs4 = 0; | |
192 | $mBytes = 1; | |
193 | $char =''; | |
194 | } | |
195 | } | |
196 | } | |
197 | return $out; | |
198 | } | |
199 | ||
200 | /** | |
201 | * Translates a Unicode codepoint into its corresponding UTF-8 character. | |
202 | * @note Based on Feyd's function at | |
203 | * <http://forums.devnetwork.net/viewtopic.php?p=191404#191404>, | |
204 | * which is in public domain. | |
205 | * @note While we're going to do code point parsing anyway, a good | |
206 | * optimization would be to refuse to translate code points that | |
207 | * are non-SGML characters. However, this could lead to duplication. | |
208 | * @note This is very similar to the unichr function in | |
209 | * maintenance/generate-entity-file.php (although this is superior, | |
210 | * due to its sanity checks). | |
211 | */ | |
212 | ||
213 | // +----------+----------+----------+----------+ | |
214 | // | 33222222 | 22221111 | 111111 | | | |
215 | // | 10987654 | 32109876 | 54321098 | 76543210 | bit | |
216 | // +----------+----------+----------+----------+ | |
217 | // | | | | 0xxxxxxx | 1 byte 0x00000000..0x0000007F | |
218 | // | | | 110yyyyy | 10xxxxxx | 2 byte 0x00000080..0x000007FF | |
219 | // | | 1110zzzz | 10yyyyyy | 10xxxxxx | 3 byte 0x00000800..0x0000FFFF | |
220 | // | 11110www | 10wwzzzz | 10yyyyyy | 10xxxxxx | 4 byte 0x00010000..0x0010FFFF | |
221 | // +----------+----------+----------+----------+ | |
222 | // | 00000000 | 00011111 | 11111111 | 11111111 | Theoretical upper limit of legal scalars: 2097151 (0x001FFFFF) | |
223 | // | 00000000 | 00010000 | 11111111 | 11111111 | Defined upper limit of legal scalar codes | |
224 | // +----------+----------+----------+----------+ | |
225 | ||
226 | public static function unichr($code) { | |
227 | if($code > 1114111 or $code < 0 or | |
228 | ($code >= 55296 and $code <= 57343) ) { | |
229 | // bits are set outside the "valid" range as defined | |
230 | // by UNICODE 4.1.0 | |
231 | return ''; | |
232 | } | |
233 | ||
234 | $x = $y = $z = $w = 0; | |
235 | if ($code < 128) { | |
236 | // regular ASCII character | |
237 | $x = $code; | |
238 | } else { | |
239 | // set up bits for UTF-8 | |
240 | $x = ($code & 63) | 128; | |
241 | if ($code < 2048) { | |
242 | $y = (($code & 2047) >> 6) | 192; | |
243 | } else { | |
244 | $y = (($code & 4032) >> 6) | 128; | |
245 | if($code < 65536) { | |
246 | $z = (($code >> 12) & 15) | 224; | |
247 | } else { | |
248 | $z = (($code >> 12) & 63) | 128; | |
249 | $w = (($code >> 18) & 7) | 240; | |
250 | } | |
251 | } | |
252 | } | |
253 | // set up the actual character | |
254 | $ret = ''; | |
255 | if($w) $ret .= chr($w); | |
256 | if($z) $ret .= chr($z); | |
257 | if($y) $ret .= chr($y); | |
258 | $ret .= chr($x); | |
259 | ||
260 | return $ret; | |
261 | } | |
262 | ||
010efc9b AD |
263 | /** |
264 | * Converts a string to UTF-8 based on configuration. | |
265 | */ | |
266 | public static function convertToUTF8($str, $config, $context) { | |
267 | $encoding = $config->get('Core.Encoding'); | |
268 | if ($encoding === 'utf-8') return $str; | |
269 | static $iconv = null; | |
cb73535c AD |
270 | if ($iconv === null) $iconv = function_exists('iconv'); |
271 | set_error_handler(array('HTMLPurifier_Encoder', 'muteErrorHandler')); | |
010efc9b | 272 | if ($iconv && !$config->get('Test.ForceNoIconv')) { |
cb73535c | 273 | $str = iconv($encoding, 'utf-8//IGNORE', $str); |
010efc9b AD |
274 | if ($str === false) { |
275 | // $encoding is not a valid encoding | |
cb73535c | 276 | restore_error_handler(); |
010efc9b AD |
277 | trigger_error('Invalid encoding ' . $encoding, E_USER_ERROR); |
278 | return ''; | |
279 | } | |
280 | // If the string is bjorked by Shift_JIS or a similar encoding | |
281 | // that doesn't support all of ASCII, convert the naughty | |
282 | // characters to their true byte-wise ASCII/UTF-8 equivalents. | |
cb73535c AD |
283 | $str = strtr($str, HTMLPurifier_Encoder::testEncodingSupportsASCII($encoding)); |
284 | restore_error_handler(); | |
010efc9b AD |
285 | return $str; |
286 | } elseif ($encoding === 'iso-8859-1') { | |
287 | $str = utf8_encode($str); | |
cb73535c | 288 | restore_error_handler(); |
010efc9b AD |
289 | return $str; |
290 | } | |
291 | trigger_error('Encoding not supported, please install iconv', E_USER_ERROR); | |
292 | } | |
293 | ||
294 | /** | |
295 | * Converts a string from UTF-8 based on configuration. | |
296 | * @note Currently, this is a lossy conversion, with unexpressable | |
297 | * characters being omitted. | |
298 | */ | |
299 | public static function convertFromUTF8($str, $config, $context) { | |
300 | $encoding = $config->get('Core.Encoding'); | |
010efc9b AD |
301 | if ($encoding === 'utf-8') return $str; |
302 | static $iconv = null; | |
cb73535c AD |
303 | if ($iconv === null) $iconv = function_exists('iconv'); |
304 | if ($escape = $config->get('Core.EscapeNonASCIICharacters')) { | |
305 | $str = HTMLPurifier_Encoder::convertToASCIIDumbLossless($str); | |
306 | } | |
307 | set_error_handler(array('HTMLPurifier_Encoder', 'muteErrorHandler')); | |
010efc9b AD |
308 | if ($iconv && !$config->get('Test.ForceNoIconv')) { |
309 | // Undo our previous fix in convertToUTF8, otherwise iconv will barf | |
cb73535c | 310 | $ascii_fix = HTMLPurifier_Encoder::testEncodingSupportsASCII($encoding); |
010efc9b AD |
311 | if (!$escape && !empty($ascii_fix)) { |
312 | $clear_fix = array(); | |
313 | foreach ($ascii_fix as $utf8 => $native) $clear_fix[$utf8] = ''; | |
314 | $str = strtr($str, $clear_fix); | |
315 | } | |
316 | $str = strtr($str, array_flip($ascii_fix)); | |
317 | // Normal stuff | |
cb73535c AD |
318 | $str = iconv('utf-8', $encoding . '//IGNORE', $str); |
319 | restore_error_handler(); | |
010efc9b AD |
320 | return $str; |
321 | } elseif ($encoding === 'iso-8859-1') { | |
322 | $str = utf8_decode($str); | |
cb73535c | 323 | restore_error_handler(); |
010efc9b AD |
324 | return $str; |
325 | } | |
326 | trigger_error('Encoding not supported', E_USER_ERROR); | |
010efc9b AD |
327 | } |
328 | ||
329 | /** | |
330 | * Lossless (character-wise) conversion of HTML to ASCII | |
331 | * @param $str UTF-8 string to be converted to ASCII | |
332 | * @returns ASCII encoded string with non-ASCII character entity-ized | |
333 | * @warning Adapted from MediaWiki, claiming fair use: this is a common | |
334 | * algorithm. If you disagree with this license fudgery, | |
335 | * implement it yourself. | |
336 | * @note Uses decimal numeric entities since they are best supported. | |
337 | * @note This is a DUMB function: it has no concept of keeping | |
338 | * character entities that the projected character encoding | |
339 | * can allow. We could possibly implement a smart version | |
340 | * but that would require it to also know which Unicode | |
341 | * codepoints the charset supported (not an easy task). | |
342 | * @note Sort of with cleanUTF8() but it assumes that $str is | |
343 | * well-formed UTF-8 | |
344 | */ | |
345 | public static function convertToASCIIDumbLossless($str) { | |
346 | $bytesleft = 0; | |
347 | $result = ''; | |
348 | $working = 0; | |
349 | $len = strlen($str); | |
350 | for( $i = 0; $i < $len; $i++ ) { | |
351 | $bytevalue = ord( $str[$i] ); | |
352 | if( $bytevalue <= 0x7F ) { //0xxx xxxx | |
353 | $result .= chr( $bytevalue ); | |
354 | $bytesleft = 0; | |
355 | } elseif( $bytevalue <= 0xBF ) { //10xx xxxx | |
356 | $working = $working << 6; | |
357 | $working += ($bytevalue & 0x3F); | |
358 | $bytesleft--; | |
359 | if( $bytesleft <= 0 ) { | |
360 | $result .= "&#" . $working . ";"; | |
361 | } | |
362 | } elseif( $bytevalue <= 0xDF ) { //110x xxxx | |
363 | $working = $bytevalue & 0x1F; | |
364 | $bytesleft = 1; | |
365 | } elseif( $bytevalue <= 0xEF ) { //1110 xxxx | |
366 | $working = $bytevalue & 0x0F; | |
367 | $bytesleft = 2; | |
368 | } else { //1111 0xxx | |
369 | $working = $bytevalue & 0x07; | |
370 | $bytesleft = 3; | |
371 | } | |
372 | } | |
373 | return $result; | |
374 | } | |
375 | ||
010efc9b AD |
376 | /** |
377 | * This expensive function tests whether or not a given character | |
378 | * encoding supports ASCII. 7/8-bit encodings like Shift_JIS will | |
379 | * fail this test, and require special processing. Variable width | |
380 | * encodings shouldn't ever fail. | |
381 | * | |
382 | * @param string $encoding Encoding name to test, as per iconv format | |
383 | * @param bool $bypass Whether or not to bypass the precompiled arrays. | |
384 | * @return Array of UTF-8 characters to their corresponding ASCII, | |
385 | * which can be used to "undo" any overzealous iconv action. | |
386 | */ | |
387 | public static function testEncodingSupportsASCII($encoding, $bypass = false) { | |
010efc9b AD |
388 | static $encodings = array(); |
389 | if (!$bypass) { | |
390 | if (isset($encodings[$encoding])) return $encodings[$encoding]; | |
391 | $lenc = strtolower($encoding); | |
392 | switch ($lenc) { | |
393 | case 'shift_jis': | |
394 | return array("\xC2\xA5" => '\\', "\xE2\x80\xBE" => '~'); | |
395 | case 'johab': | |
396 | return array("\xE2\x82\xA9" => '\\'); | |
397 | } | |
398 | if (strpos($lenc, 'iso-8859-') === 0) return array(); | |
399 | } | |
400 | $ret = array(); | |
cb73535c AD |
401 | set_error_handler(array('HTMLPurifier_Encoder', 'muteErrorHandler')); |
402 | if (iconv('UTF-8', $encoding, 'a') === false) return false; | |
010efc9b AD |
403 | for ($i = 0x20; $i <= 0x7E; $i++) { // all printable ASCII chars |
404 | $c = chr($i); // UTF-8 char | |
cb73535c | 405 | $r = iconv('UTF-8', "$encoding//IGNORE", $c); // initial conversion |
010efc9b AD |
406 | if ( |
407 | $r === '' || | |
408 | // This line is needed for iconv implementations that do not | |
409 | // omit characters that do not exist in the target character set | |
cb73535c | 410 | ($r === $c && iconv($encoding, 'UTF-8//IGNORE', $r) !== $c) |
010efc9b AD |
411 | ) { |
412 | // Reverse engineer: what's the UTF-8 equiv of this byte | |
413 | // sequence? This assumes that there's no variable width | |
414 | // encoding that doesn't support ASCII. | |
cb73535c | 415 | $ret[iconv($encoding, 'UTF-8//IGNORE', $c)] = $c; |
010efc9b AD |
416 | } |
417 | } | |
cb73535c | 418 | restore_error_handler(); |
010efc9b AD |
419 | $encodings[$encoding] = $ret; |
420 | return $ret; | |
421 | } | |
422 | ||
423 | ||
424 | } | |
425 | ||
426 | // vim: et sw=4 sts=4 |