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- <?php
- /**
- * A UTF-8 specific character encoder that handles cleaning and transforming.
- * @note All functions in this class should be static.
- */
- class HTMLPurifier_Encoder
- {
- /**
- * Constructor throws fatal error if you attempt to instantiate class
- */
- private function __construct() {
- trigger_error('Cannot instantiate encoder, call methods statically', E_USER_ERROR);
- }
- /**
- * Error-handler that mutes errors, alternative to shut-up operator.
- */
- public static function muteErrorHandler() {}
- /**
- * iconv wrapper which mutes errors, but doesn't work around bugs.
- */
- public static function unsafeIconv($in, $out, $text) {
- set_error_handler(array('HTMLPurifier_Encoder', 'muteErrorHandler'));
- $r = iconv($in, $out, $text);
- restore_error_handler();
- return $r;
- }
- /**
- * iconv wrapper which mutes errors and works around bugs.
- */
- public static function iconv($in, $out, $text, $max_chunk_size = 8000) {
- $code = self::testIconvTruncateBug();
- if ($code == self::ICONV_OK) {
- return self::unsafeIconv($in, $out, $text);
- } elseif ($code == self::ICONV_TRUNCATES) {
- // we can only work around this if the input character set
- // is utf-8
- if ($in == 'utf-8') {
- if ($max_chunk_size < 4) {
- trigger_error('max_chunk_size is too small', E_USER_WARNING);
- return false;
- }
- // split into 8000 byte chunks, but be careful to handle
- // multibyte boundaries properly
- if (($c = strlen($text)) <= $max_chunk_size) {
- return self::unsafeIconv($in, $out, $text);
- }
- $r = '';
- $i = 0;
- while (true) {
- if ($i + $max_chunk_size >= $c) {
- $r .= self::unsafeIconv($in, $out, substr($text, $i));
- break;
- }
- // wibble the boundary
- if (0x80 != (0xC0 & ord($text[$i + $max_chunk_size]))) {
- $chunk_size = $max_chunk_size;
- } elseif (0x80 != (0xC0 & ord($text[$i + $max_chunk_size - 1]))) {
- $chunk_size = $max_chunk_size - 1;
- } elseif (0x80 != (0xC0 & ord($text[$i + $max_chunk_size - 2]))) {
- $chunk_size = $max_chunk_size - 2;
- } elseif (0x80 != (0xC0 & ord($text[$i + $max_chunk_size - 3]))) {
- $chunk_size = $max_chunk_size - 3;
- } else {
- return false; // rather confusing UTF-8...
- }
- $chunk = substr($text, $i, $chunk_size); // substr doesn't mind overlong lengths
- $r .= self::unsafeIconv($in, $out, $chunk);
- $i += $chunk_size;
- }
- return $r;
- } else {
- return false;
- }
- } else {
- return false;
- }
- }
- /**
- * Cleans a UTF-8 string for well-formedness and SGML validity
- *
- * It will parse according to UTF-8 and return a valid UTF8 string, with
- * non-SGML codepoints excluded.
- *
- * @note Just for reference, the non-SGML code points are 0 to 31 and
- * 127 to 159, inclusive. However, we allow code points 9, 10
- * and 13, which are the tab, line feed and carriage return
- * respectively. 128 and above the code points map to multibyte
- * UTF-8 representations.
- *
- * @note Fallback code adapted from utf8ToUnicode by Henri Sivonen and
- * hsivonen@iki.fi at <http://iki.fi/hsivonen/php-utf8/> under the
- * LGPL license. Notes on what changed are inside, but in general,
- * the original code transformed UTF-8 text into an array of integer
- * Unicode codepoints. Understandably, transforming that back to
- * a string would be somewhat expensive, so the function was modded to
- * directly operate on the string. However, this discourages code
- * reuse, and the logic enumerated here would be useful for any
- * function that needs to be able to understand UTF-8 characters.
- * As of right now, only smart lossless character encoding converters
- * would need that, and I'm probably not going to implement them.
- * Once again, PHP 6 should solve all our problems.
- */
- public static function cleanUTF8($str, $force_php = false) {
- // UTF-8 validity is checked since PHP 4.3.5
- // This is an optimization: if the string is already valid UTF-8, no
- // need to do PHP stuff. 99% of the time, this will be the case.
- // The regexp matches the XML char production, as well as well as excluding
- // non-SGML codepoints U+007F to U+009F
- if (preg_match('/^[\x{9}\x{A}\x{D}\x{20}-\x{7E}\x{A0}-\x{D7FF}\x{E000}-\x{FFFD}\x{10000}-\x{10FFFF}]*$/Du', $str)) {
- return $str;
- }
- $mState = 0; // cached expected number of octets after the current octet
- // until the beginning of the next UTF8 character sequence
- $mUcs4 = 0; // cached Unicode character
- $mBytes = 1; // cached expected number of octets in the current sequence
- // original code involved an $out that was an array of Unicode
- // codepoints. Instead of having to convert back into UTF-8, we've
- // decided to directly append valid UTF-8 characters onto a string
- // $out once they're done. $char accumulates raw bytes, while $mUcs4
- // turns into the Unicode code point, so there's some redundancy.
- $out = '';
- $char = '';
- $len = strlen($str);
- for($i = 0; $i < $len; $i++) {
- $in = ord($str{$i});
- $char .= $str[$i]; // append byte to char
- if (0 == $mState) {
- // When mState is zero we expect either a US-ASCII character
- // or a multi-octet sequence.
- if (0 == (0x80 & ($in))) {
- // US-ASCII, pass straight through.
- if (($in <= 31 || $in == 127) &&
- !($in == 9 || $in == 13 || $in == 10) // save \r\t\n
- ) {
- // control characters, remove
- } else {
- $out .= $char;
- }
- // reset
- $char = '';
- $mBytes = 1;
- } elseif (0xC0 == (0xE0 & ($in))) {
- // First octet of 2 octet sequence
- $mUcs4 = ($in);
- $mUcs4 = ($mUcs4 & 0x1F) << 6;
- $mState = 1;
- $mBytes = 2;
- } elseif (0xE0 == (0xF0 & ($in))) {
- // First octet of 3 octet sequence
- $mUcs4 = ($in);
- $mUcs4 = ($mUcs4 & 0x0F) << 12;
- $mState = 2;
- $mBytes = 3;
- } elseif (0xF0 == (0xF8 & ($in))) {
- // First octet of 4 octet sequence
- $mUcs4 = ($in);
- $mUcs4 = ($mUcs4 & 0x07) << 18;
- $mState = 3;
- $mBytes = 4;
- } elseif (0xF8 == (0xFC & ($in))) {
- // First octet of 5 octet sequence.
- //
- // This is illegal because the encoded codepoint must be
- // either:
- // (a) not the shortest form or
- // (b) outside the Unicode range of 0-0x10FFFF.
- // Rather than trying to resynchronize, we will carry on
- // until the end of the sequence and let the later error
- // handling code catch it.
- $mUcs4 = ($in);
- $mUcs4 = ($mUcs4 & 0x03) << 24;
- $mState = 4;
- $mBytes = 5;
- } elseif (0xFC == (0xFE & ($in))) {
- // First octet of 6 octet sequence, see comments for 5
- // octet sequence.
- $mUcs4 = ($in);
- $mUcs4 = ($mUcs4 & 1) << 30;
- $mState = 5;
- $mBytes = 6;
- } else {
- // Current octet is neither in the US-ASCII range nor a
- // legal first octet of a multi-octet sequence.
- $mState = 0;
- $mUcs4 = 0;
- $mBytes = 1;
- $char = '';
- }
- } else {
- // When mState is non-zero, we expect a continuation of the
- // multi-octet sequence
- if (0x80 == (0xC0 & ($in))) {
- // Legal continuation.
- $shift = ($mState - 1) * 6;
- $tmp = $in;
- $tmp = ($tmp & 0x0000003F) << $shift;
- $mUcs4 |= $tmp;
- if (0 == --$mState) {
- // End of the multi-octet sequence. mUcs4 now contains
- // the final Unicode codepoint to be output
- // Check for illegal sequences and codepoints.
- // From Unicode 3.1, non-shortest form is illegal
- if (((2 == $mBytes) && ($mUcs4 < 0x0080)) ||
- ((3 == $mBytes) && ($mUcs4 < 0x0800)) ||
- ((4 == $mBytes) && ($mUcs4 < 0x10000)) ||
- (4 < $mBytes) ||
- // From Unicode 3.2, surrogate characters = illegal
- (($mUcs4 & 0xFFFFF800) == 0xD800) ||
- // Codepoints outside the Unicode range are illegal
- ($mUcs4 > 0x10FFFF)
- ) {
- } elseif (0xFEFF != $mUcs4 && // omit BOM
- // check for valid Char unicode codepoints
- (
- 0x9 == $mUcs4 ||
- 0xA == $mUcs4 ||
- 0xD == $mUcs4 ||
- (0x20 <= $mUcs4 && 0x7E >= $mUcs4) ||
- // 7F-9F is not strictly prohibited by XML,
- // but it is non-SGML, and thus we don't allow it
- (0xA0 <= $mUcs4 && 0xD7FF >= $mUcs4) ||
- (0x10000 <= $mUcs4 && 0x10FFFF >= $mUcs4)
- )
- ) {
- $out .= $char;
- }
- // initialize UTF8 cache (reset)
- $mState = 0;
- $mUcs4 = 0;
- $mBytes = 1;
- $char = '';
- }
- } else {
- // ((0xC0 & (*in) != 0x80) && (mState != 0))
- // Incomplete multi-octet sequence.
- // used to result in complete fail, but we'll reset
- $mState = 0;
- $mUcs4 = 0;
- $mBytes = 1;
- $char ='';
- }
- }
- }
- return $out;
- }
- /**
- * Translates a Unicode codepoint into its corresponding UTF-8 character.
- * @note Based on Feyd's function at
- * <http://forums.devnetwork.net/viewtopic.php?p=191404#191404>,
- * which is in public domain.
- * @note While we're going to do code point parsing anyway, a good
- * optimization would be to refuse to translate code points that
- * are non-SGML characters. However, this could lead to duplication.
- * @note This is very similar to the unichr function in
- * maintenance/generate-entity-file.php (although this is superior,
- * due to its sanity checks).
- */
- // +----------+----------+----------+----------+
- // | 33222222 | 22221111 | 111111 | |
- // | 10987654 | 32109876 | 54321098 | 76543210 | bit
- // +----------+----------+----------+----------+
- // | | | | 0xxxxxxx | 1 byte 0x00000000..0x0000007F
- // | | | 110yyyyy | 10xxxxxx | 2 byte 0x00000080..0x000007FF
- // | | 1110zzzz | 10yyyyyy | 10xxxxxx | 3 byte 0x00000800..0x0000FFFF
- // | 11110www | 10wwzzzz | 10yyyyyy | 10xxxxxx | 4 byte 0x00010000..0x0010FFFF
- // +----------+----------+----------+----------+
- // | 00000000 | 00011111 | 11111111 | 11111111 | Theoretical upper limit of legal scalars: 2097151 (0x001FFFFF)
- // | 00000000 | 00010000 | 11111111 | 11111111 | Defined upper limit of legal scalar codes
- // +----------+----------+----------+----------+
- public static function unichr($code) {
- if($code > 1114111 or $code < 0 or
- ($code >= 55296 and $code <= 57343) ) {
- // bits are set outside the "valid" range as defined
- // by UNICODE 4.1.0
- return '';
- }
- $x = $y = $z = $w = 0;
- if ($code < 128) {
- // regular ASCII character
- $x = $code;
- } else {
- // set up bits for UTF-8
- $x = ($code & 63) | 128;
- if ($code < 2048) {
- $y = (($code & 2047) >> 6) | 192;
- } else {
- $y = (($code & 4032) >> 6) | 128;
- if($code < 65536) {
- $z = (($code >> 12) & 15) | 224;
- } else {
- $z = (($code >> 12) & 63) | 128;
- $w = (($code >> 18) & 7) | 240;
- }
- }
- }
- // set up the actual character
- $ret = '';
- if($w) $ret .= chr($w);
- if($z) $ret .= chr($z);
- if($y) $ret .= chr($y);
- $ret .= chr($x);
- return $ret;
- }
- public static function iconvAvailable() {
- static $iconv = null;
- if ($iconv === null) {
- $iconv = function_exists('iconv') && self::testIconvTruncateBug() != self::ICONV_UNUSABLE;
- }
- return $iconv;
- }
- /**
- * Converts a string to UTF-8 based on configuration.
- */
- public static function convertToUTF8($str, $config, $context) {
- $encoding = $config->get('Core.Encoding');
- if ($encoding === 'utf-8') return $str;
- static $iconv = null;
- if ($iconv === null) $iconv = self::iconvAvailable();
- if ($iconv && !$config->get('Test.ForceNoIconv')) {
- // unaffected by bugs, since UTF-8 support all characters
- $str = self::unsafeIconv($encoding, 'utf-8//IGNORE', $str);
- if ($str === false) {
- // $encoding is not a valid encoding
- trigger_error('Invalid encoding ' . $encoding, E_USER_ERROR);
- return '';
- }
- // If the string is bjorked by Shift_JIS or a similar encoding
- // that doesn't support all of ASCII, convert the naughty
- // characters to their true byte-wise ASCII/UTF-8 equivalents.
- $str = strtr($str, self::testEncodingSupportsASCII($encoding));
- return $str;
- } elseif ($encoding === 'iso-8859-1') {
- $str = utf8_encode($str);
- return $str;
- }
- $bug = HTMLPurifier_Encoder::testIconvTruncateBug();
- if ($bug == self::ICONV_OK) {
- trigger_error('Encoding not supported, please install iconv', E_USER_ERROR);
- } else {
- trigger_error('You have a buggy version of iconv, see https://bugs.php.net/bug.php?id=48147 and http://sourceware.org/bugzilla/show_bug.cgi?id=13541', E_USER_ERROR);
- }
- }
- /**
- * Converts a string from UTF-8 based on configuration.
- * @note Currently, this is a lossy conversion, with unexpressable
- * characters being omitted.
- */
- public static function convertFromUTF8($str, $config, $context) {
- $encoding = $config->get('Core.Encoding');
- if ($escape = $config->get('Core.EscapeNonASCIICharacters')) {
- $str = self::convertToASCIIDumbLossless($str);
- }
- if ($encoding === 'utf-8') return $str;
- static $iconv = null;
- if ($iconv === null) $iconv = self::iconvAvailable();
- if ($iconv && !$config->get('Test.ForceNoIconv')) {
- // Undo our previous fix in convertToUTF8, otherwise iconv will barf
- $ascii_fix = self::testEncodingSupportsASCII($encoding);
- if (!$escape && !empty($ascii_fix)) {
- $clear_fix = array();
- foreach ($ascii_fix as $utf8 => $native) $clear_fix[$utf8] = '';
- $str = strtr($str, $clear_fix);
- }
- $str = strtr($str, array_flip($ascii_fix));
- // Normal stuff
- $str = self::iconv('utf-8', $encoding . '//IGNORE', $str);
- return $str;
- } elseif ($encoding === 'iso-8859-1') {
- $str = utf8_decode($str);
- return $str;
- }
- trigger_error('Encoding not supported', E_USER_ERROR);
- // You might be tempted to assume that the ASCII representation
- // might be OK, however, this is *not* universally true over all
- // encodings. So we take the conservative route here, rather
- // than forcibly turn on %Core.EscapeNonASCIICharacters
- }
- /**
- * Lossless (character-wise) conversion of HTML to ASCII
- * @param $str UTF-8 string to be converted to ASCII
- * @returns ASCII encoded string with non-ASCII character entity-ized
- * @warning Adapted from MediaWiki, claiming fair use: this is a common
- * algorithm. If you disagree with this license fudgery,
- * implement it yourself.
- * @note Uses decimal numeric entities since they are best supported.
- * @note This is a DUMB function: it has no concept of keeping
- * character entities that the projected character encoding
- * can allow. We could possibly implement a smart version
- * but that would require it to also know which Unicode
- * codepoints the charset supported (not an easy task).
- * @note Sort of with cleanUTF8() but it assumes that $str is
- * well-formed UTF-8
- */
- public static function convertToASCIIDumbLossless($str) {
- $bytesleft = 0;
- $result = '';
- $working = 0;
- $len = strlen($str);
- for( $i = 0; $i < $len; $i++ ) {
- $bytevalue = ord( $str[$i] );
- if( $bytevalue <= 0x7F ) { //0xxx xxxx
- $result .= chr( $bytevalue );
- $bytesleft = 0;
- } elseif( $bytevalue <= 0xBF ) { //10xx xxxx
- $working = $working << 6;
- $working += ($bytevalue & 0x3F);
- $bytesleft--;
- if( $bytesleft <= 0 ) {
- $result .= "&#" . $working . ";";
- }
- } elseif( $bytevalue <= 0xDF ) { //110x xxxx
- $working = $bytevalue & 0x1F;
- $bytesleft = 1;
- } elseif( $bytevalue <= 0xEF ) { //1110 xxxx
- $working = $bytevalue & 0x0F;
- $bytesleft = 2;
- } else { //1111 0xxx
- $working = $bytevalue & 0x07;
- $bytesleft = 3;
- }
- }
- return $result;
- }
- /** No bugs detected in iconv. */
- const ICONV_OK = 0;
- /** Iconv truncates output if converting from UTF-8 to another
- * character set with //IGNORE, and a non-encodable character is found */
- const ICONV_TRUNCATES = 1;
- /** Iconv does not support //IGNORE, making it unusable for
- * transcoding purposes */
- const ICONV_UNUSABLE = 2;
- /**
- * glibc iconv has a known bug where it doesn't handle the magic
- * //IGNORE stanza correctly. In particular, rather than ignore
- * characters, it will return an EILSEQ after consuming some number
- * of characters, and expect you to restart iconv as if it were
- * an E2BIG. Old versions of PHP did not respect the errno, and
- * returned the fragment, so as a result you would see iconv
- * mysteriously truncating output. We can work around this by
- * manually chopping our input into segments of about 8000
- * characters, as long as PHP ignores the error code. If PHP starts
- * paying attention to the error code, iconv becomes unusable.
- *
- * @returns Error code indicating severity of bug.
- */
- public static function testIconvTruncateBug() {
- static $code = null;
- if ($code === null) {
- // better not use iconv, otherwise infinite loop!
- $r = self::unsafeIconv('utf-8', 'ascii//IGNORE', "\xCE\xB1" . str_repeat('a', 9000));
- if ($r === false) {
- $code = self::ICONV_UNUSABLE;
- } elseif (($c = strlen($r)) < 9000) {
- $code = self::ICONV_TRUNCATES;
- } elseif ($c > 9000) {
- trigger_error('Your copy of iconv is extremely buggy. Please notify HTML Purifier maintainers: include your iconv version as per phpversion()', E_USER_ERROR);
- } else {
- $code = self::ICONV_OK;
- }
- }
- return $code;
- }
- /**
- * This expensive function tests whether or not a given character
- * encoding supports ASCII. 7/8-bit encodings like Shift_JIS will
- * fail this test, and require special processing. Variable width
- * encodings shouldn't ever fail.
- *
- * @param string $encoding Encoding name to test, as per iconv format
- * @param bool $bypass Whether or not to bypass the precompiled arrays.
- * @return Array of UTF-8 characters to their corresponding ASCII,
- * which can be used to "undo" any overzealous iconv action.
- */
- public static function testEncodingSupportsASCII($encoding, $bypass = false) {
- // All calls to iconv here are unsafe, proof by case analysis:
- // If ICONV_OK, no difference.
- // If ICONV_TRUNCATE, all calls involve one character inputs,
- // so bug is not triggered.
- // If ICONV_UNUSABLE, this call is irrelevant
- static $encodings = array();
- if (!$bypass) {
- if (isset($encodings[$encoding])) return $encodings[$encoding];
- $lenc = strtolower($encoding);
- switch ($lenc) {
- case 'shift_jis':
- return array("\xC2\xA5" => '\\', "\xE2\x80\xBE" => '~');
- case 'johab':
- return array("\xE2\x82\xA9" => '\\');
- }
- if (strpos($lenc, 'iso-8859-') === 0) return array();
- }
- $ret = array();
- if (self::unsafeIconv('UTF-8', $encoding, 'a') === false) return false;
- for ($i = 0x20; $i <= 0x7E; $i++) { // all printable ASCII chars
- $c = chr($i); // UTF-8 char
- $r = self::unsafeIconv('UTF-8', "$encoding//IGNORE", $c); // initial conversion
- if (
- $r === '' ||
- // This line is needed for iconv implementations that do not
- // omit characters that do not exist in the target character set
- ($r === $c && self::unsafeIconv($encoding, 'UTF-8//IGNORE', $r) !== $c)
- ) {
- // Reverse engineer: what's the UTF-8 equiv of this byte
- // sequence? This assumes that there's no variable width
- // encoding that doesn't support ASCII.
- $ret[self::unsafeIconv($encoding, 'UTF-8//IGNORE', $c)] = $c;
- }
- }
- $encodings[$encoding] = $ret;
- return $ret;
- }
- }
- // vim: et sw=4 sts=4
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