includes/libs/StringUtils.php

   1 <?php
   2 /**
   3  * Methods to play with strings.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  */
  22
  23 /**
  24  * A collection of static methods to play with strings.
  25  */
  26 class StringUtils {
  27         /**
  28          * Test whether a string is valid UTF-8.
  29          *
  30          * The function check for invalid byte sequences, overlong encoding but
  31          * not for different normalisations.
  32          *
  33          * @note In MediaWiki 1.21, this function did not provide proper UTF-8 validation.
  34          * In particular, the pure PHP code path did not in fact check for overlong forms.
  35          * Beware of this when backporting code to that version of MediaWiki.
  36          *
  37          * @since 1.21
  38          * @param string $value String to check
  39          * @return bool Whether the given $value is a valid UTF-8 encoded string
  40          */
  41         static function isUtf8( $value ) {
  42                 $value = (string)$value;
  43
  44                 // Before PHP 5.4, values above U+10FFFF are incorrectly allowed, so we have to
  45                 // check for them separately.
  46                 static $newPHP;
  47                 if ( $newPHP === null ) {
  48                         $newPHP = !mb_check_encoding( "\xf4\x90\x80\x80", 'UTF-8' );
  49                 }
  50
  51                 return mb_check_encoding( $value, 'UTF-8' ) &&
  52                         ( $newPHP || preg_match( "/\xf4[\x90-\xbf]|[\xf5-\xff]/S", $value ) === 0 );
  53         }
  54
  55         /**
  56          * Perform an operation equivalent to `preg_replace()`
  57          *
  58          * Matches this code:
  59          *
  60          *     preg_replace( "!$startDelim(.*?)$endDelim!", $replace, $subject );
  61          *
  62          * ..except that it's worst-case O(N) instead of O(N^2). Compared to delimiterReplace(), this
  63          * implementation is fast but memory-hungry and inflexible. The memory requirements are such
  64          * that I don't recommend using it on anything but guaranteed small chunks of text.
  65          *
  66          * @param string $startDelim
  67          * @param string $endDelim
  68          * @param string $replace
  69          * @param string $subject
  70          * @return string
  71          */
  72         static function hungryDelimiterReplace( $startDelim, $endDelim, $replace, $subject ) {
  73                 $segments = explode( $startDelim, $subject );
  74                 $output = array_shift( $segments );
  75                 foreach ( $segments as $s ) {
  76                         $endDelimPos = strpos( $s, $endDelim );
  77                         if ( $endDelimPos === false ) {
  78                                 $output .= $startDelim . $s;
  79                         } else {
  80                                 $output .= $replace . substr( $s, $endDelimPos + strlen( $endDelim ) );
  81                         }
  82                 }
  83
  84                 return $output;
  85         }
  86
  87         /**
  88          * Perform an operation equivalent to `preg_replace_callback()`
  89          *
  90          * Matches this code:
  91          *
  92          *     preg_replace_callback( "!$startDelim(.*)$endDelim!s$flags", $callback, $subject );
  93          *
  94          * If the start delimiter ends with an initial substring of the end delimiter,
  95          * e.g. in the case of C-style comments, the behavior differs from the model
  96          * regex. In this implementation, the end must share no characters with the
  97          * start, so e.g. `/*\/` is not considered to be both the start and end of a
  98          * comment. `/*\/xy/*\/` is considered to be a single comment with contents `/xy/`.
  99          *
 100          * The implementation of delimiterReplaceCallback() is slower than hungryDelimiterReplace()
 101          * but uses far less memory. The delimiters are literal strings, not regular expressions.
 102          *
 103          * @param string $startDelim Start delimiter
 104          * @param string $endDelim End delimiter
 105          * @param callable $callback Function to call on each match
 106          * @param string $subject
 107          * @param string $flags Regular expression flags
 108          * @throws InvalidArgumentException
 109          * @return string
 110          */
 111         static function delimiterReplaceCallback( $startDelim, $endDelim, $callback,
 112                 $subject, $flags = ''
 113         ) {
 114                 $inputPos = 0;
 115                 $outputPos = 0;
 116                 $output = '';
 117                 $foundStart = false;
 118                 $encStart = preg_quote( $startDelim, '!' );
 119                 $encEnd = preg_quote( $endDelim, '!' );
 120                 $strcmp = strpos( $flags, 'i' ) === false ? 'strcmp' : 'strcasecmp';
 121                 $endLength = strlen( $endDelim );
 122                 $m = [];
 123
 124                 while ( $inputPos < strlen( $subject ) &&
 125                         preg_match( "!($encStart)|($encEnd)!S$flags", $subject, $m, PREG_OFFSET_CAPTURE, $inputPos )
 126                 ) {
 127                         $tokenOffset = $m[0][1];
 128                         if ( $m[1][0] != '' ) {
 129                                 if ( $foundStart &&
 130                                         $strcmp( $endDelim, substr( $subject, $tokenOffset, $endLength ) ) == 0
 131                                 ) {
 132                                         # An end match is present at the same location
 133                                         $tokenType = 'end';
 134                                         $tokenLength = $endLength;
 135                                 } else {
 136                                         $tokenType = 'start';
 137                                         $tokenLength = strlen( $m[0][0] );
 138                                 }
 139                         } elseif ( $m[2][0] != '' ) {
 140                                 $tokenType = 'end';
 141                                 $tokenLength = strlen( $m[0][0] );
 142                         } else {
 143                                 throw new InvalidArgumentException( 'Invalid delimiter given to ' . __METHOD__ );
 144                         }
 145
 146                         if ( $tokenType == 'start' ) {
 147                                 # Only move the start position if we haven't already found a start
 148                                 # This means that START START END matches outer pair
 149                                 if ( !$foundStart ) {
 150                                         # Found start
 151                                         $inputPos = $tokenOffset + $tokenLength;
 152                                         # Write out the non-matching section
 153                                         $output .= substr( $subject, $outputPos, $tokenOffset - $outputPos );
 154                                         $outputPos = $tokenOffset;
 155                                         $contentPos = $inputPos;
 156                                         $foundStart = true;
 157                                 } else {
 158                                         # Move the input position past the *first character* of START,
 159                                         # to protect against missing END when it overlaps with START
 160                                         $inputPos = $tokenOffset + 1;
 161                                 }
 162                         } elseif ( $tokenType == 'end' ) {
 163                                 if ( $foundStart ) {
 164                                         # Found match
 165                                         $output .= call_user_func( $callback, [
 166                                                 substr( $subject, $outputPos, $tokenOffset + $tokenLength - $outputPos ),
 167                                                 substr( $subject, $contentPos, $tokenOffset - $contentPos )
 168                                         ] );
 169                                         $foundStart = false;
 170                                 } else {
 171                                         # Non-matching end, write it out
 172                                         $output .= substr( $subject, $inputPos, $tokenOffset + $tokenLength - $outputPos );
 173                                 }
 174                                 $inputPos = $outputPos = $tokenOffset + $tokenLength;
 175                         } else {
 176                                 throw new InvalidArgumentException( 'Invalid delimiter given to ' . __METHOD__ );
 177                         }
 178                 }
 179                 if ( $outputPos < strlen( $subject ) ) {
 180                         $output .= substr( $subject, $outputPos );
 181                 }
 182
 183                 return $output;
 184         }
 185
 186         /**
 187          * Perform an operation equivalent to `preg_replace()` with flags.
 188          *
 189          * Matches this code:
 190          *
 191          *     preg_replace( "!$startDelim(.*)$endDelim!$flags", $replace, $subject );
 192          *
 193          * @param string $startDelim Start delimiter regular expression
 194          * @param string $endDelim End delimiter regular expression
 195          * @param string $replace Replacement string. May contain $1, which will be
 196          *  replaced by the text between the delimiters
 197          * @param string $subject String to search
 198          * @param string $flags Regular expression flags
 199          * @return string The string with the matches replaced
 200          */
 201         static function delimiterReplace( $startDelim, $endDelim, $replace, $subject, $flags = '' ) {
 202                 $replacer = new RegexlikeReplacer( $replace );
 203
 204                 return self::delimiterReplaceCallback( $startDelim, $endDelim,
 205                         $replacer->cb(), $subject, $flags );
 206         }
 207
 208         /**
 209          * More or less "markup-safe" explode()
 210          * Ignores any instances of the separator inside `<...>`
 211          * @param string $separator
 212          * @param string $text
 213          * @return array
 214          */
 215         static function explodeMarkup( $separator, $text ) {
 216                 $placeholder = "\x00";
 217
 218                 // Remove placeholder instances
 219                 $text = str_replace( $placeholder, '', $text );
 220
 221                 // Replace instances of the separator inside HTML-like tags with the placeholder
 222                 $replacer = new DoubleReplacer( $separator, $placeholder );
 223                 $cleaned = StringUtils::delimiterReplaceCallback( '<', '>', $replacer->cb(), $text );
 224
 225                 // Explode, then put the replaced separators back in
 226                 $items = explode( $separator, $cleaned );
 227                 foreach ( $items as $i => $str ) {
 228                         $items[$i] = str_replace( $placeholder, $separator, $str );
 229                 }
 230
 231                 return $items;
 232         }
 233
 234         /**
 235          * More or less "markup-safe" str_replace()
 236          * Ignores any instances of the separator inside `<...>`
 237          * @param string $search
 238          * @param string $replace
 239          * @param string $text
 240          * @return string
 241          */
 242         static function replaceMarkup( $search, $replace, $text ) {
 243                 $placeholder = "\x00";
 244
 245                 // Remove placeholder instances
 246                 $text = str_replace( $placeholder, '', $text );
 247
 248                 // Replace instances of the separator inside HTML-like tags with the placeholder
 249                 $replacer = new DoubleReplacer( $search, $placeholder );
 250                 $cleaned = StringUtils::delimiterReplaceCallback( '<', '>', $replacer->cb(), $text );
 251
 252                 // Explode, then put the replaced separators back in
 253                 $cleaned = str_replace( $search, $replace, $cleaned );
 254                 $text = str_replace( $placeholder, $search, $cleaned );
 255
 256                 return $text;
 257         }
 258
 259         /**
 260          * Escape a string to make it suitable for inclusion in a preg_replace()
 261          * replacement parameter.
 262          *
 263          * @param string $string
 264          * @return string
 265          */
 266         static function escapeRegexReplacement( $string ) {
 267                 $string = str_replace( '\\', '\\\\', $string );
 268                 $string = str_replace( '$', '\\$', $string );
 269                 return $string;
 270         }
 271
 272         /**
 273          * Workalike for explode() with limited memory usage.
 274          *
 275          * @param string $separator
 276          * @param string $subject
 277          * @return ArrayIterator|ExplodeIterator
 278          */
 279         static function explode( $separator, $subject ) {
 280                 if ( substr_count( $subject, $separator ) > 1000 ) {
 281                         return new ExplodeIterator( $separator, $subject );
 282                 } else {
 283                         return new ArrayIterator( explode( $separator, $subject ) );
 284                 }
 285         }
 286 }