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<?php
/**
* HTML API: WP_HTML_Decoder class
*
* Decodes spans of raw text found inside HTML content.
*
* @package WordPress
* @subpackage HTML-API
* @since 6.6.0
*/
class WP_HTML_Decoder {
/**
* Indicates if an attribute value starts with a given raw string value.
*
* Use this method to determine if an attribute value starts with a given string, regardless
* of how it might be encoded in HTML. For instance, `http:` could be represented as `http:`
* or as `http:` or as `http:` or as `http:`, or in many other ways.
*
* Example:
*
* $value = 'http://wordpress.org/';
* true === WP_HTML_Decoder::attribute_starts_with( $value, 'http:', 'ascii-case-insensitive' );
* false === WP_HTML_Decoder::attribute_starts_with( $value, 'https:', 'ascii-case-insensitive' );
*
* @since 6.6.0
*
* @param string $haystack String containing the raw non-decoded attribute value.
* @param string $search_text Does the attribute value start with this plain string.
* @param string $case_sensitivity Optional. Pass 'ascii-case-insensitive' to ignore ASCII case when matching.
* Default 'case-sensitive'.
* @return bool Whether the attribute value starts with the given string.
*/
public static function attribute_starts_with( $haystack, $search_text, $case_sensitivity = 'case-sensitive' ): bool {
$search_length = strlen( $search_text );
$loose_case = 'ascii-case-insensitive' === $case_sensitivity;
$haystack_end = strlen( $haystack );
$search_at = 0;
$haystack_at = 0;
while ( $search_at < $search_length && $haystack_at < $haystack_end ) {
$chars_match = $loose_case
? strtolower( $haystack[ $haystack_at ] ) === strtolower( $search_text[ $search_at ] )
: $haystack[ $haystack_at ] === $search_text[ $search_at ];
$is_introducer = '&' === $haystack[ $haystack_at ];
$next_chunk = $is_introducer
? self::read_character_reference( 'attribute', $haystack, $haystack_at, $token_length )
: null;
// If there's no character reference and the characters don't match, the match fails.
if ( null === $next_chunk && ! $chars_match ) {
return false;
}
// If there's no character reference but the character do match, then it could still match.
if ( null === $next_chunk && $chars_match ) {
++$haystack_at;
++$search_at;
continue;
}
// If there is a character reference, then the decoded value must exactly match what follows in the search string.
if ( 0 !== substr_compare( $search_text, $next_chunk, $search_at, strlen( $next_chunk ), $loose_case ) ) {
return false;
}
// The character reference matched, so continue checking.
$haystack_at += $token_length;
$search_at += strlen( $next_chunk );
}
return true;
}
/**
* Returns a string containing the decoded value of a given HTML text node.
*
* Text nodes appear in HTML DATA sections, which are the text segments inside
* and around tags, excepting SCRIPT and STYLE elements (and some others),
* whose inner text is not decoded. Use this function to read the decoded
* value of such a text span in an HTML document.
*
* Example:
*
* '“😄”' === WP_HTML_Decode::decode_text_node( '“😄”' );
*
* @since 6.6.0
*
* @param string $text Text containing raw and non-decoded text node to decode.
* @return string Decoded UTF-8 value of given text node.
*/
public static function decode_text_node( $text ): string {
return static::decode( 'data', $text );
}
/**
* Returns a string containing the decoded value of a given HTML attribute.
*
* Text found inside an HTML attribute has different parsing rules than for
* text found inside other markup, or DATA segments. Use this function to
* read the decoded value of an HTML string inside a quoted attribute.
*
* Example:
*
* '“😄”' === WP_HTML_Decode::decode_attribute( '“😄”' );
*
* @since 6.6.0
*
* @param string $text Text containing raw and non-decoded attribute value to decode.
* @return string Decoded UTF-8 value of given attribute value.
*/
public static function decode_attribute( $text ): string {
return static::decode( 'attribute', $text );
}
/**
* Decodes a span of HTML text, depending on the context in which it's found.
*
* This is a low-level method; prefer calling WP_HTML_Decoder::decode_attribute() or
* WP_HTML_Decoder::decode_text_node() instead. It's provided for cases where this
* may be difficult to do from calling code.
*
* Example:
*
* '©' = WP_HTML_Decoder::decode( 'data', '©' );
*
* @since 6.6.0
*
* @access private
*
* @param string $context `attribute` for decoding attribute values, `data` otherwise.
* @param string $text Text document containing span of text to decode.
* @return string Decoded UTF-8 string.
*/
public static function decode( $context, $text ): string {
$decoded = '';
$end = strlen( $text );
$at = 0;
$was_at = 0;
while ( $at < $end ) {
$next_character_reference_at = strpos( $text, '&', $at );
if ( false === $next_character_reference_at ) {
break;
}
$character_reference = self::read_character_reference( $context, $text, $next_character_reference_at, $token_length );
if ( isset( $character_reference ) ) {
$at = $next_character_reference_at;
$decoded .= substr( $text, $was_at, $at - $was_at );
$decoded .= $character_reference;
$at += $token_length;
$was_at = $at;
continue;
}
++$at;
}
if ( 0 === $was_at ) {
return $text;
}
if ( $was_at < $end ) {
$decoded .= substr( $text, $was_at, $end - $was_at );
}
return $decoded;
}
/**
* Attempt to read a character reference at the given location in a given string,
* depending on the context in which it's found.
*
* If a character reference is found, this function will return the translated value
* that the reference maps to. It will then set `$match_byte_length` the
* number of bytes of input it read while consuming the character reference. This
* gives calling code the opportunity to advance its cursor when traversing a string
* and decoding.
*
* Example:
*
* null === WP_HTML_Decoder::read_character_reference( 'attribute', 'Ships…', 0 );
* '…' === WP_HTML_Decoder::read_character_reference( 'attribute', 'Ships…', 5, $token_length );
* 8 === $token_length; // `…`
*
* null === WP_HTML_Decoder::read_character_reference( 'attribute', '¬in', 0 );
* '∉' === WP_HTML_Decoder::read_character_reference( 'attribute', '∉', 0, $token_length );
* 7 === $token_length; // `∉`
*
* '¬' === WP_HTML_Decoder::read_character_reference( 'data', '¬in', 0, $token_length );
* 4 === $token_length; // `¬`
* '∉' === WP_HTML_Decoder::read_character_reference( 'data', '∉', 0, $token_length );
* 7 === $token_length; // `∉`
*
* @since 6.6.0
*
* @global WP_Token_Map $html5_named_character_references Mappings for HTML5 named character references.
*
* @param string $context `attribute` for decoding attribute values, `data` otherwise.
* @param string $text Text document containing span of text to decode.
* @param int $at Optional. Byte offset into text where span begins, defaults to the beginning (0).
* @param int &$match_byte_length Optional. Set to byte-length of character reference if provided and if a match
* is found, otherwise not set. Default null.
* @return string|false Decoded character reference in UTF-8 if found, otherwise `false`.
*/
public static function read_character_reference( $context, $text, $at = 0, &$match_byte_length = null ) {
/**
* Mappings for HTML5 named character references.
*
* @var WP_Token_Map $html5_named_character_references
*/
global $html5_named_character_references;
$length = strlen( $text );
if ( $at + 1 >= $length ) {
return null;
}
if ( '&' !== $text[ $at ] ) {
return null;
}
/*
* Numeric character references.
*
* When truncated, these will encode the code point found by parsing the
* digits that are available. For example, when `🅰` is truncated
* to `DZ` it will encode `DZ`. It does not:
* - know how to parse the original `🅰`.
* - fail to parse and return plaintext `DZ`.
* - fail to parse and return the replacement character `�`
*/
if ( '#' === $text[ $at + 1 ] ) {
if ( $at + 2 >= $length ) {
return null;
}
/** Tracks inner parsing within the numeric character reference. */
$digits_at = $at + 2;
if ( 'x' === $text[ $digits_at ] || 'X' === $text[ $digits_at ] ) {
$numeric_base = 16;
$numeric_digits = '0123456789abcdefABCDEF';
$max_digits = 6; // 
++$digits_at;
} else {
$numeric_base = 10;
$numeric_digits = '0123456789';
$max_digits = 7; // 
}
// Cannot encode invalid Unicode code points. Max is to U+10FFFF.
$zero_count = strspn( $text, '0', $digits_at );
$digit_count = strspn( $text, $numeric_digits, $digits_at + $zero_count );
$after_digits = $digits_at + $zero_count + $digit_count;
$has_semicolon = $after_digits < $length && ';' === $text[ $after_digits ];
$end_of_span = $has_semicolon ? $after_digits + 1 : $after_digits;
// `&#` or `&#x` without digits returns into plaintext.
if ( 0 === $digit_count && 0 === $zero_count ) {
return null;
}
// Whereas `&#` and only zeros is invalid.
if ( 0 === $digit_count ) {
$match_byte_length = $end_of_span - $at;
return '�';
}
// If there are too many digits then it's not worth parsing. It's invalid.
if ( $digit_count > $max_digits ) {
$match_byte_length = $end_of_span - $at;
return '�';
}
$digits = substr( $text, $digits_at + $zero_count, $digit_count );
$code_point = intval( $digits, $numeric_base );
/*
* Noncharacters, 0x0D, and non-ASCII-whitespace control characters.
*
* > A noncharacter is a code point that is in the range U+FDD0 to U+FDEF,
* > inclusive, or U+FFFE, U+FFFF, U+1FFFE, U+1FFFF, U+2FFFE, U+2FFFF,
* > U+3FFFE, U+3FFFF, U+4FFFE, U+4FFFF, U+5FFFE, U+5FFFF, U+6FFFE,
* > U+6FFFF, U+7FFFE, U+7FFFF, U+8FFFE, U+8FFFF, U+9FFFE, U+9FFFF,
* > U+AFFFE, U+AFFFF, U+BFFFE, U+BFFFF, U+CFFFE, U+CFFFF, U+DFFFE,
* > U+DFFFF, U+EFFFE, U+EFFFF, U+FFFFE, U+FFFFF, U+10FFFE, or U+10FFFF.
*
* A C0 control is a code point that is in the range of U+00 to U+1F,
* but ASCII whitespace includes U+09, U+0A, U+0C, and U+0D.
*
* These characters are invalid but still decode as any valid character.
* This comment is here to note and explain why there's no check to
* remove these characters or replace them.
*
* @see https://infra.spec.whatwg.org/#noncharacter
*/
/*
* Code points in the C1 controls area need to be remapped as if they
* were stored in Windows-1252. Note! This transformation only happens
* for numeric character references. The raw code points in the byte
* stream are not translated.
*
* > If the number is one of the numbers in the first column of
* > the following table, then find the row with that number in
* > the first column, and set the character reference code to
* > the number in the second column of that row.
*/
if ( $code_point >= 0x80 && $code_point <= 0x9F ) {
$windows_1252_mapping = array(
0x20AC, // 0x80 -> EURO SIGN (€).
0x81, // 0x81 -> (no change).
0x201A, // 0x82 -> SINGLE LOW-9 QUOTATION MARK (‚).
0x0192, // 0x83 -> LATIN SMALL LETTER F WITH HOOK (ƒ).
0x201E, // 0x84 -> DOUBLE LOW-9 QUOTATION MARK („).
0x2026, // 0x85 -> HORIZONTAL ELLIPSIS (…).
0x2020, // 0x86 -> DAGGER (†).
0x2021, // 0x87 -> DOUBLE DAGGER (‡).
0x02C6, // 0x88 -> MODIFIER LETTER CIRCUMFLEX ACCENT (ˆ).
0x2030, // 0x89 -> PER MILLE SIGN (‰).
0x0160, // 0x8A -> LATIN CAPITAL LETTER S WITH CARON (Š).
0x2039, // 0x8B -> SINGLE LEFT-POINTING ANGLE QUOTATION MARK (‹).
0x0152, // 0x8C -> LATIN CAPITAL LIGATURE OE (Œ).
0x8D, // 0x8D -> (no change).
0x017D, // 0x8E -> LATIN CAPITAL LETTER Z WITH CARON (Ž).
0x8F, // 0x8F -> (no change).
0x90, // 0x90 -> (no change).
0x2018, // 0x91 -> LEFT SINGLE QUOTATION MARK (‘).
0x2019, // 0x92 -> RIGHT SINGLE QUOTATION MARK (’).
0x201C, // 0x93 -> LEFT DOUBLE QUOTATION MARK (“).
0x201D, // 0x94 -> RIGHT DOUBLE QUOTATION MARK (”).
0x2022, // 0x95 -> BULLET (•).
0x2013, // 0x96 -> EN DASH (–).
0x2014, // 0x97 -> EM DASH (—).
0x02DC, // 0x98 -> SMALL TILDE (˜).
0x2122, // 0x99 -> TRADE MARK SIGN (™).
0x0161, // 0x9A -> LATIN SMALL LETTER S WITH CARON (š).
0x203A, // 0x9B -> SINGLE RIGHT-POINTING ANGLE QUOTATION MARK (›).
0x0153, // 0x9C -> LATIN SMALL LIGATURE OE (œ).
0x9D, // 0x9D -> (no change).
0x017E, // 0x9E -> LATIN SMALL LETTER Z WITH CARON (ž).
0x0178, // 0x9F -> LATIN CAPITAL LETTER Y WITH DIAERESIS (Ÿ).
);
$code_point = $windows_1252_mapping[ $code_point - 0x80 ];
}
$match_byte_length = $end_of_span - $at;
return self::code_point_to_utf8_bytes( $code_point );
}
/** Tracks inner parsing within the named character reference. */
$name_at = $at + 1;
// Minimum named character reference is two characters. E.g. `GT`.
if ( $name_at + 2 > $length ) {
return null;
}
$name_length = 0;
$replacement = $html5_named_character_references->read_token( $text, $name_at, $name_length );
if ( false === $replacement ) {
return null;
}
$after_name = $name_at + $name_length;
// If the match ended with a semicolon then it should always be decoded.
if ( ';' === $text[ $name_at + $name_length - 1 ] ) {
$match_byte_length = $after_name - $at;
return $replacement;
}
/*
* At this point though there's a match for an entry in the named
* character reference table but the match doesn't end in `;`.
* It may be allowed if it's followed by something unambiguous.
*/
$ambiguous_follower = (
$after_name < $length &&
$name_at < $length &&
(
ctype_alnum( $text[ $after_name ] ) ||
'=' === $text[ $after_name ]
)
);
// It's non-ambiguous, safe to leave it in.
if ( ! $ambiguous_follower ) {
$match_byte_length = $after_name - $at;
return $replacement;
}
// It's ambiguous, which isn't allowed inside attributes.
if ( 'attribute' === $context ) {
return null;
}
$match_byte_length = $after_name - $at;
return $replacement;
}
/**
* Encode a code point number into the UTF-8 encoding.
*
* This encoder implements the UTF-8 encoding algorithm for converting
* a code point into a byte sequence. If it receives an invalid code
* point it will return the Unicode Replacement Character U+FFFD `�`.
*
* Example:
*
* '🅰' === WP_HTML_Decoder::code_point_to_utf8_bytes( 0x1f170 );
*
* // Half of a surrogate pair is an invalid code point.
* '�' === WP_HTML_Decoder::code_point_to_utf8_bytes( 0xd83c );
*
* @since 6.6.0
*
* @see https://www.rfc-editor.org/rfc/rfc3629 For the UTF-8 standard.
*
* @param int $code_point Which code point to convert.
* @return string Converted code point, or `�` if invalid.
*/
public static function code_point_to_utf8_bytes( $code_point ): string {
// Pre-check to ensure a valid code point.
if (
$code_point <= 0 ||
( $code_point >= 0xD800 && $code_point <= 0xDFFF ) ||
$code_point > 0x10FFFF
) {
return '�';
}
if ( $code_point <= 0x7F ) {
return chr( $code_point );
}
if ( $code_point <= 0x7FF ) {
$byte1 = chr( ( $code_point >> 6 ) | 0xC0 );
$byte2 = chr( $code_point & 0x3F | 0x80 );
return "{$byte1}{$byte2}";
}
if ( $code_point <= 0xFFFF ) {
$byte1 = chr( ( $code_point >> 12 ) | 0xE0 );
$byte2 = chr( ( $code_point >> 6 ) & 0x3F | 0x80 );
$byte3 = chr( $code_point & 0x3F | 0x80 );
return "{$byte1}{$byte2}{$byte3}";
}
// Any values above U+10FFFF are eliminated above in the pre-check.
$byte1 = chr( ( $code_point >> 18 ) | 0xF0 );
$byte2 = chr( ( $code_point >> 12 ) & 0x3F | 0x80 );
$byte3 = chr( ( $code_point >> 6 ) & 0x3F | 0x80 );
$byte4 = chr( $code_point & 0x3F | 0x80 );
return "{$byte1}{$byte2}{$byte3}{$byte4}";
}
}