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Static Public Member Functions | Private Member Functions
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.
static cleanUTF8 ($str, $force_php=false)
 Cleans a UTF-8 string for well-formedness and SGML validity.
static unichr ($code)
 Translates a Unicode codepoint into its corresponding UTF-8 character.
static convertToUTF8 ($str, $config, $context)
 Converts a string to UTF-8 based on configuration.
static convertFromUTF8 ($str, $config, $context)
 Converts a string from UTF-8 based on configuration.
static convertToASCIIDumbLossless ($str)
 Lossless (character-wise) conversion of HTML to ASCII.
static testEncodingSupportsASCII ($encoding, $bypass=false)
 This expensive function tests whether or not a given character encoding supports ASCII.

Private Member Functions

 __construct ()
 Constructor throws fatal error if you attempt to instantiate class.

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

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

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 47 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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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 299 of file Encoder.php.

References $config, convertToASCIIDumbLossless(), and testEncodingSupportsASCII().

Referenced by HTMLPurifier\purify().

{
$encoding = $config->get('Core.Encoding');
if ($encoding === 'utf-8') return $str;
static $iconv = null;
if ($iconv === null) $iconv = function_exists('iconv');
if ($escape = $config->get('Core.EscapeNonASCIICharacters')) {
$str = HTMLPurifier_Encoder::convertToASCIIDumbLossless($str);
}
set_error_handler(array('HTMLPurifier_Encoder', 'muteErrorHandler'));
if ($iconv && !$config->get('Test.ForceNoIconv')) {
// Undo our previous fix in convertToUTF8, otherwise iconv will barf
$ascii_fix = HTMLPurifier_Encoder::testEncodingSupportsASCII($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 = iconv('utf-8', $encoding . '//IGNORE', $str);
restore_error_handler();
return $str;
} elseif ($encoding === 'iso-8859-1') {
$str = utf8_decode($str);
restore_error_handler();
return $str;
}
trigger_error('Encoding not supported', E_USER_ERROR);
}

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static HTMLPurifier_Encoder::convertToASCIIDumbLossless (   $str)
static

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

Parameters
$strUTF-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 345 of file Encoder.php.

References $result.

Referenced by convertFromUTF8().

{
$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;
}

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

Converts a string to UTF-8 based on configuration.

Definition at line 266 of file Encoder.php.

References $config, and testEncodingSupportsASCII().

Referenced by HTMLPurifier\purify().

{
$encoding = $config->get('Core.Encoding');
if ($encoding === 'utf-8') return $str;
static $iconv = null;
if ($iconv === null) $iconv = function_exists('iconv');
set_error_handler(array('HTMLPurifier_Encoder', 'muteErrorHandler'));
if ($iconv && !$config->get('Test.ForceNoIconv')) {
$str = iconv($encoding, 'utf-8//IGNORE', $str);
if ($str === false) {
// $encoding is not a valid encoding
restore_error_handler();
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, HTMLPurifier_Encoder::testEncodingSupportsASCII($encoding));
restore_error_handler();
return $str;
} elseif ($encoding === 'iso-8859-1') {
$str = utf8_encode($str);
restore_error_handler();
return $str;
}
trigger_error('Encoding not supported, please install iconv', E_USER_ERROR);
}

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static HTMLPurifier_Encoder::muteErrorHandler ( )
static

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

Definition at line 20 of file Encoder.php.

{}
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$encodingEncoding name to test, as per iconv format
bool$bypassWhether 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 387 of file Encoder.php.

References $ret.

Referenced by convertFromUTF8(), and convertToUTF8().

{
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();
set_error_handler(array('HTMLPurifier_Encoder', 'muteErrorHandler'));
if (iconv('UTF-8', $encoding, 'a') === false) return false;
for ($i = 0x20; $i <= 0x7E; $i++) { // all printable ASCII chars
$c = chr($i); // UTF-8 char
$r = iconv('UTF-8', "$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 === $c && iconv($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.
$ret[iconv($encoding, 'UTF-8//IGNORE', $c)] = $c;
}
}
restore_error_handler();
$encodings[$encoding] = $ret;
return $ret;
}

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