HTMLPurifier_Encoder Class Reference

A UTF-8 specific character encoder that handles cleaning and transforming. More...

Collaboration diagram for HTMLPurifier_Encoder:

Static Public Member Functions
static	muteErrorHandler ()
	Error-handler that mutes errors, alternative to shut-up operator. More...
static	unsafeIconv ($in, $out, $text)
	iconv wrapper which mutes errors, but doesn't work around bugs. More...
static	iconv ($in, $out, $text, $max_chunk_size=8000)
	iconv wrapper which mutes errors and works around bugs. More...
static	cleanUTF8 ($str, $force_php=false)
	Cleans a UTF-8 string for well-formedness and SGML validity. More...
static	unichr ($code)
	Translates a Unicode codepoint into its corresponding UTF-8 character. More...
static	iconvAvailable ()
static	convertToUTF8 ($str, $config, $context)
	Converts a string to UTF-8 based on configuration. More...
static	convertFromUTF8 ($str, $config, $context)
	Converts a string from UTF-8 based on configuration. More...
static	convertToASCIIDumbLossless ($str)
	Lossless (character-wise) conversion of HTML to ASCII. More...
static	testIconvTruncateBug ()
	glibc iconv has a known bug where it doesn't handle the magic //IGNORE stanza correctly. More...
static	testEncodingSupportsASCII ($encoding, $bypass=false)
	This expensive function tests whether or not a given character encoding supports ASCII. More...

Data Fields
const	ICONV_OK = 0
	No bugs detected in iconv. More...
const	ICONV_TRUNCATES = 1
	Iconv truncates output if converting from UTF-8 to another character set with //IGNORE, and a non-encodable character is found. More...
const	ICONV_UNUSABLE = 2
	Iconv does not support //IGNORE, making it unusable for transcoding purposes. More...

Private Member Functions
	__construct ()
	Constructor throws fatal error if you attempt to instantiate class. More...

Detailed Description

A UTF-8 specific character encoder that handles cleaning and transforming.

Note

All functions in this class should be static.

Definition at line 7 of file Encoder.php.

Constructor & Destructor Documentation

__construct()

HTMLPurifier_Encoder::__construct ( )

private

Constructor throws fatal error if you attempt to instantiate class.

Definition at line 13 of file Encoder.php.

                                   {
        trigger_error('Cannot instantiate encoder, call methods statically', E_USER_ERROR);
    }

Member Function Documentation

cleanUTF8()

static HTMLPurifier_Encoder::cleanUTF8 (   $str,   $force_php = false  )

static

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.

Fallback code adapted from utf8ToUnicode by Henri Sivonen and hsivo.nosp@m.nen@.nosp@m.iki.f.nosp@m.i 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.

Definition at line 109 of file Encoder.php.

References $in, and $out.

Referenced by HTMLPurifier_Printer\escape(), HTMLPurifier_AttrDef\expandCSSEscape(), and HTMLPurifier_Lexer\normalize().

                                                               {

        // 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;
    }

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convertFromUTF8()

static HTMLPurifier_Encoder::convertFromUTF8 (   $str,   $config,   $context  )

static

Converts a string from UTF-8 based on configuration.

Note

Currently, this is a lossy conversion, with unexpressable characters being omitted.

Definition at line 371 of file Encoder.php.

Referenced by HTMLPurifier\purify().

                                                                    {
        $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
    }

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convertToASCIIDumbLossless()

static HTMLPurifier_Encoder::convertToASCIIDumbLossless (   $str )

static

Lossless (character-wise) conversion of HTML to ASCII.

Parameters

$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.

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).

Sort of with cleanUTF8() but it assumes that $str is well-formed UTF-8

Definition at line 418 of file Encoder.php.

References $result.

                                                            {
        $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;
    }

convertToUTF8()

static HTMLPurifier_Encoder::convertToUTF8 (   $str,   $config,   $context  )

static

Converts a string to UTF-8 based on configuration.

Definition at line 336 of file Encoder.php.

References testIconvTruncateBug().

Referenced by HTMLPurifier\purify().

                                                                  {
        $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);
        }
    }

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iconv()

static HTMLPurifier_Encoder::iconv (   $in,   $out,   $text,   $max_chunk_size = 8000  )

static

iconv wrapper which mutes errors and works around bugs.

Definition at line 35 of file Encoder.php.

References $in, $out, and $r.

Referenced by unsafeIconv().

                                                                           {
        $code = self::testIconvTruncateBug();
        if ($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;
        }
    }

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iconvAvailable()

static HTMLPurifier_Encoder::iconvAvailable ( )

static

Definition at line 325 of file Encoder.php.

                                            {
        static $iconv = null;
        if ($iconv === null) {
            $iconv = function_exists('iconv') && self::testIconvTruncateBug() != self::ICONV_UNUSABLE;
        }
        return $iconv;
    }

muteErrorHandler()

static HTMLPurifier_Encoder::muteErrorHandler ( )

static

Error-handler that mutes errors, alternative to shut-up operator.

Definition at line 20 of file Encoder.php.

{}

testEncodingSupportsASCII()

static HTMLPurifier_Encoder::testEncodingSupportsASCII (   $encoding,   $bypass = false  )

static

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.

Parameters

string	$encoding	Encoding name to test, as per iconv format
bool	$bypass	Whether or not to bypass the precompiled arrays.

Returns

Array of UTF-8 characters to their corresponding ASCII, which can be used to "undo" any overzealous iconv action.

Definition at line 503 of file Encoder.php.

References $r, and $ret.

                                                                                 {
        // 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;
    }

testIconvTruncateBug()

static HTMLPurifier_Encoder::testIconvTruncateBug ( )

static

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.

Definition at line 474 of file Encoder.php.

References $r.

Referenced by convertToUTF8().

                                                  {
        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;
    }

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unichr()

static HTMLPurifier_Encoder::unichr (   $code )

static

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.

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.

This is very similar to the unichr function in maintenance/generate-entity-file.php (although this is superior, due to its sanity checks).

Definition at line 288 of file Encoder.php.

References $ret.

Referenced by HTMLPurifier_AttrDef\expandCSSEscape(), and HTMLPurifier_EntityParser\nonSpecialEntityCallback().

                                         {
        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;
    }

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unsafeIconv()

static HTMLPurifier_Encoder::unsafeIconv (   $in,   $out,   $text  )

static

iconv wrapper which mutes errors, but doesn't work around bugs.

Definition at line 25 of file Encoder.php.

References $in, $out, $r, and iconv().

                                                         {
        set_error_handler(array('HTMLPurifier_Encoder', 'muteErrorHandler'));
        $r = iconv($in, $out, $text);
        restore_error_handler();
        return $r;
    }

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Field Documentation

ICONV_OK

const HTMLPurifier_Encoder::ICONV_OK = 0

No bugs detected in iconv.

Definition at line 450 of file Encoder.php.

ICONV_TRUNCATES

const HTMLPurifier_Encoder::ICONV_TRUNCATES = 1

Iconv truncates output if converting from UTF-8 to another character set with //IGNORE, and a non-encodable character is found.

Definition at line 454 of file Encoder.php.

ICONV_UNUSABLE

const HTMLPurifier_Encoder::ICONV_UNUSABLE = 2

Iconv does not support //IGNORE, making it unusable for transcoding purposes.

Definition at line 458 of file Encoder.php.

---

The documentation for this class was generated from the following file:

• Services/Html/HtmlPurifier/library/HTMLPurifier/Encoder.php