includes/libs/CSSMin.php

   1 <?php
   2 /**
   3  * Minification of CSS stylesheets.
   4  *
   5  * Copyright 2010 Wikimedia Foundation
   6  *
   7  * Licensed under the Apache License, Version 2.0 (the "License"); you may
   8  * not use this file except in compliance with the License.
   9  * You may obtain a copy of the License at
  10  *
  11  *     http://www.apache.org/licenses/LICENSE-2.0
  12  *
  13  * Unless required by applicable law or agreed to in writing, software distributed
  14  * under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
  15  * OF ANY KIND, either express or implied. See the License for the
  16  * specific language governing permissions and limitations under the License.
  17  *
  18  * @file
  19  * @version 0.1.1 -- 2010-09-11
  20  * @author Trevor Parscal <tparscal@wikimedia.org>
  21  * @copyright Copyright 2010 Wikimedia Foundation
  22  * @license http://www.apache.org/licenses/LICENSE-2.0
  23  */
  24
  25 /**
  26  * Transforms CSS data
  27  *
  28  * This class provides minification, URL remapping, URL extracting, and data-URL embedding.
  29  */
  30 class CSSMin {
  31
  32         /* Constants */
  33
  34         /** @var string Strip marker for comments. **/
  35         const PLACEHOLDER = "\x7fPLACEHOLDER\x7f";
  36
  37         /**
  38          * Internet Explorer data URI length limit. See encodeImageAsDataURI().
  39          */
  40         const DATA_URI_SIZE_LIMIT = 32768;
  41
  42         const EMBED_REGEX = '\/\*\s*\@embed\s*\*\/';
  43         const COMMENT_REGEX = '\/\*.*?\*\/';
  44
  45         /* Protected Static Members */
  46
  47         /** @var array List of common image files extensions and MIME-types */
  48         protected static $mimeTypes = [
  49                 'gif' => 'image/gif',
  50                 'jpe' => 'image/jpeg',
  51                 'jpeg' => 'image/jpeg',
  52                 'jpg' => 'image/jpeg',
  53                 'png' => 'image/png',
  54                 'tif' => 'image/tiff',
  55                 'tiff' => 'image/tiff',
  56                 'xbm' => 'image/x-xbitmap',
  57                 'svg' => 'image/svg+xml',
  58         ];
  59
  60         /* Static Methods */
  61
  62         /**
  63          * Get a list of local files referenced in a stylesheet (includes non-existent files).
  64          *
  65          * @param string $source CSS stylesheet source to process
  66          * @param string $path File path where the source was read from
  67          * @return array List of local file references
  68          */
  69         public static function getLocalFileReferences( $source, $path ) {
  70                 $stripped = preg_replace( '/' . self::COMMENT_REGEX . '/s', '', $source );
  71                 $path = rtrim( $path, '/' ) . '/';
  72                 $files = [];
  73
  74                 $rFlags = PREG_OFFSET_CAPTURE | PREG_SET_ORDER;
  75                 if ( preg_match_all( '/' . self::getUrlRegex() . '/', $stripped, $matches, $rFlags ) ) {
  76                         foreach ( $matches as $match ) {
  77                                 self::processUrlMatch( $match, $rFlags );
  78                                 $url = $match['file'][0];
  79
  80                                 // Skip fully-qualified and protocol-relative URLs and data URIs
  81                                 if ( substr( $url, 0, 2 ) === '//' || parse_url( $url, PHP_URL_SCHEME ) ) {
  82                                         break;
  83                                 }
  84
  85                                 $files[] = $path . $url;
  86                         }
  87                 }
  88                 return $files;
  89         }
  90
  91         /**
  92          * Encode an image file as a data URI.
  93          *
  94          * If the image file has a suitable MIME type and size, encode it as a data URI, base64-encoded
  95          * for binary files or just percent-encoded otherwise. Return false if the image type is
  96          * unfamiliar or file exceeds the size limit.
  97          *
  98          * @param string $file Image file to encode.
  99          * @param string|null $type File's MIME type or null. If null, CSSMin will
 100          *     try to autodetect the type.
 101          * @param bool $ie8Compat By default, a data URI will only be produced if it can be made short
 102          *     enough to fit in Internet Explorer 8 (and earlier) URI length limit (32,768 bytes). Pass
 103          *     `false` to remove this limitation.
 104          * @return string|bool Image contents encoded as a data URI or false.
 105          */
 106         public static function encodeImageAsDataURI( $file, $type = null, $ie8Compat = true ) {
 107                 // Fast-fail for files that definitely exceed the maximum data URI length
 108                 if ( $ie8Compat && filesize( $file ) >= self::DATA_URI_SIZE_LIMIT ) {
 109                         return false;
 110                 }
 111
 112                 if ( $type === null ) {
 113                         $type = self::getMimeType( $file );
 114                 }
 115                 if ( !$type ) {
 116                         return false;
 117                 }
 118
 119                 return self::encodeStringAsDataURI( file_get_contents( $file ), $type, $ie8Compat );
 120         }
 121
 122         /**
 123          * Encode file contents as a data URI with chosen MIME type.
 124          *
 125          * The URI will be base64-encoded for binary files or just percent-encoded otherwise.
 126          *
 127          * @since 1.25
 128          *
 129          * @param string $contents File contents to encode.
 130          * @param string $type File's MIME type.
 131          * @param bool $ie8Compat See encodeImageAsDataURI().
 132          * @return string|bool Image contents encoded as a data URI or false.
 133          */
 134         public static function encodeStringAsDataURI( $contents, $type, $ie8Compat = true ) {
 135                 // Try #1: Non-encoded data URI
 136                 // The regular expression matches ASCII whitespace and printable characters.
 137                 if ( preg_match( '/^[\r\n\t\x20-\x7e]+$/', $contents ) ) {
 138                         // Do not base64-encode non-binary files (sane SVGs).
 139                         // (This often produces longer URLs, but they compress better, yielding a net smaller size.)
 140                         $uri = 'data:' . $type . ',' . rawurlencode( $contents );
 141                         if ( !$ie8Compat || strlen( $uri ) < self::DATA_URI_SIZE_LIMIT ) {
 142                                 return $uri;
 143                         }
 144                 }
 145
 146                 // Try #2: Encoded data URI
 147                 $uri = 'data:' . $type . ';base64,' . base64_encode( $contents );
 148                 if ( !$ie8Compat || strlen( $uri ) < self::DATA_URI_SIZE_LIMIT ) {
 149                         return $uri;
 150                 }
 151
 152                 // A data URI couldn't be produced
 153                 return false;
 154         }
 155
 156         /**
 157          * Serialize a string (escape and quote) for use as a CSS string value.
 158          * http://www.w3.org/TR/2013/WD-cssom-20131205/#serialize-a-string
 159          *
 160          * @param string $value
 161          * @return string
 162          * @throws Exception
 163          */
 164         public static function serializeStringValue( $value ) {
 165                 if ( strstr( $value, "\0" ) ) {
 166                         throw new Exception( "Invalid character in CSS string" );
 167                 }
 168                 $value = strtr( $value, [ '\\' => '\\\\', '"' => '\\"' ] );
 169                 $value = preg_replace_callback( '/[\x01-\x1f\x7f-\x9f]/', function ( $match ) {
 170                         return '\\' . base_convert( ord( $match[0] ), 10, 16 ) . ' ';
 171                 }, $value );
 172                 return '"' . $value . '"';
 173         }
 174
 175         /**
 176          * @param string $file
 177          * @return bool|string
 178          */
 179         public static function getMimeType( $file ) {
 180                 // Infer the MIME-type from the file extension
 181                 $ext = strtolower( pathinfo( $file, PATHINFO_EXTENSION ) );
 182                 if ( isset( self::$mimeTypes[$ext] ) ) {
 183                         return self::$mimeTypes[$ext];
 184                 }
 185
 186                 $realpath = realpath( $file );
 187                 if (
 188                         $realpath
 189                         && function_exists( 'finfo_file' )
 190                         && function_exists( 'finfo_open' )
 191                         && defined( 'FILEINFO_MIME_TYPE' )
 192                 ) {
 193                         return finfo_file( finfo_open( FILEINFO_MIME_TYPE ), $realpath );
 194                 }
 195
 196                 return false;
 197         }
 198
 199         /**
 200          * Build a CSS 'url()' value for the given URL, quoting parentheses (and other funny characters)
 201          * and escaping quotes as necessary.
 202          *
 203          * See http://www.w3.org/TR/css-syntax-3/#consume-a-url-token
 204          *
 205          * @param string $url URL to process
 206          * @return string 'url()' value, usually just `"url($url)"`, quoted/escaped if necessary
 207          */
 208         public static function buildUrlValue( $url ) {
 209                 // The list below has been crafted to match URLs such as:
 210                 //   scheme://user@domain:port/~user/fi%20le.png?query=yes&really=y+s
 211                 //   data:image/png;base64,R0lGODlh/+==
 212                 if ( preg_match( '!^[\w\d:@/~.%+;,?&=-]+$!', $url ) ) {
 213                         return "url($url)";
 214                 } else {
 215                         return 'url("' . strtr( $url, [ '\\' => '\\\\', '"' => '\\"' ] ) . '")';
 216                 }
 217         }
 218
 219         /**
 220          * Remaps CSS URL paths and automatically embeds data URIs for CSS rules
 221          * or url() values preceded by an / * @embed * / comment.
 222          *
 223          * @param string $source CSS data to remap
 224          * @param string $local File path where the source was read from
 225          * @param string $remote URL path to the file
 226          * @param bool $embedData If false, never do any data URI embedding,
 227          *   even if / * @embed * / is found.
 228          * @return string Remapped CSS data
 229          */
 230         public static function remap( $source, $local, $remote, $embedData = true ) {
 231                 // High-level overview:
 232                 // * For each CSS rule in $source that includes at least one url() value:
 233                 //   * Check for an @embed comment at the start indicating that all URIs should be embedded
 234                 //   * For each url() value:
 235                 //     * Check for an @embed comment directly preceding the value
 236                 //     * If either @embed comment exists:
 237                 //       * Embedding the URL as data: URI, if it's possible / allowed
 238                 //       * Otherwise remap the URL to work in generated stylesheets
 239
 240                 // Guard against trailing slashes, because "some/remote/../foo.png"
 241                 // resolves to "some/remote/foo.png" on (some?) clients (T29052).
 242                 if ( substr( $remote, -1 ) == '/' ) {
 243                         $remote = substr( $remote, 0, -1 );
 244                 }
 245
 246                 // Disallow U+007F DELETE, which is illegal anyway, and which
 247                 // we use for comment placeholders.
 248                 $source = str_replace( "\x7f", "?", $source );
 249
 250                 // Replace all comments by a placeholder so they will not interfere with the remapping.
 251                 // Warning: This will also catch on anything looking like the start of a comment between
 252                 // quotation marks (e.g. "foo /* bar").
 253                 $comments = [];
 254
 255                 $pattern = '/(?!' . CSSMin::EMBED_REGEX . ')(' . CSSMin::COMMENT_REGEX . ')/s';
 256
 257                 $source = preg_replace_callback(
 258                         $pattern,
 259                         function ( $match ) use ( &$comments ) {
 260                                 $comments[] = $match[ 0 ];
 261                                 return CSSMin::PLACEHOLDER . ( count( $comments ) - 1 ) . 'x';
 262                         },
 263                         $source
 264                 );
 265
 266                 // Note: This will not correctly handle cases where ';', '{' or '}'
 267                 // appears in the rule itself, e.g. in a quoted string. You are advised
 268                 // not to use such characters in file names. We also match start/end of
 269                 // the string to be consistent in edge-cases ('@import url(…)').
 270                 $pattern = '/(?:^|[;{])\K[^;{}]*' . self::getUrlRegex() . '[^;}]*(?=[;}]|$)/';
 271
 272                 $source = preg_replace_callback(
 273                         $pattern,
 274                         function ( $matchOuter ) use ( $local, $remote, $embedData ) {
 275                                 $rule = $matchOuter[0];
 276
 277                                 // Check for global @embed comment and remove it. Allow other comments to be present
 278                                 // before @embed (they have been replaced with placeholders at this point).
 279                                 $embedAll = false;
 280                                 $rule = preg_replace(
 281                                         '/^((?:\s+|' .
 282                                                 CSSMin::PLACEHOLDER .
 283                                                 '(\d+)x)*)' .
 284                                                 CSSMin::EMBED_REGEX .
 285                                                 '\s*/',
 286                                         '$1',
 287                                         $rule,
 288                                         1,
 289                                         $embedAll
 290                                 );
 291
 292                                 // Build two versions of current rule: with remapped URLs
 293                                 // and with embedded data: URIs (where possible).
 294                                 $pattern = '/(?P<embed>' . CSSMin::EMBED_REGEX . '\s*|)' . self::getUrlRegex() . '/';
 295
 296                                 $ruleWithRemapped = preg_replace_callback(
 297                                         $pattern,
 298                                         function ( $match ) use ( $local, $remote ) {
 299                                                 self::processUrlMatch( $match );
 300
 301                                                 $remapped = CSSMin::remapOne( $match['file'], $match['query'], $local, $remote, false );
 302                                                 return CSSMin::buildUrlValue( $remapped );
 303                                         },
 304                                         $rule
 305                                 );
 306
 307                                 if ( $embedData ) {
 308                                         // Remember the occurring MIME types to avoid fallbacks when embedding some files.
 309                                         $mimeTypes = [];
 310
 311                                         $ruleWithEmbedded = preg_replace_callback(
 312                                                 $pattern,
 313                                                 function ( $match ) use ( $embedAll, $local, $remote, &$mimeTypes ) {
 314                                                         self::processUrlMatch( $match );
 315
 316                                                         $embed = $embedAll || $match['embed'];
 317                                                         $embedded = CSSMin::remapOne(
 318                                                                 $match['file'],
 319                                                                 $match['query'],
 320                                                                 $local,
 321                                                                 $remote,
 322                                                                 $embed
 323                                                         );
 324
 325                                                         $url = $match['file'] . $match['query'];
 326                                                         $file = "{$local}/{$match['file']}";
 327                                                         if (
 328                                                                 !self::isRemoteUrl( $url ) && !self::isLocalUrl( $url )
 329                                                                 && file_exists( $file )
 330                                                         ) {
 331                                                                 $mimeTypes[ CSSMin::getMimeType( $file ) ] = true;
 332                                                         }
 333
 334                                                         return CSSMin::buildUrlValue( $embedded );
 335                                                 },
 336                                                 $rule
 337                                         );
 338
 339                                         // Are all referenced images SVGs?
 340                                         $needsEmbedFallback = $mimeTypes !== [ 'image/svg+xml' => true ];
 341                                 }
 342
 343                                 if ( !$embedData || $ruleWithEmbedded === $ruleWithRemapped ) {
 344                                         // We're not embedding anything, or we tried to but the file is not embeddable
 345                                         return $ruleWithRemapped;
 346                                 } elseif ( $embedData && $needsEmbedFallback ) {
 347                                         // Build 2 CSS properties; one which uses a data URI in place of the @embed comment, and
 348                                         // the other with a remapped and versioned URL with an Internet Explorer 6 and 7 hack
 349                                         // making it ignored in all browsers that support data URIs
 350                                         return "$ruleWithEmbedded;$ruleWithRemapped!ie";
 351                                 } else {
 352                                         // Look ma, no fallbacks! This is for files which IE 6 and 7 don't support anyway: SVG.
 353                                         return $ruleWithEmbedded;
 354                                 }
 355                         }, $source );
 356
 357                 // Re-insert comments
 358                 $pattern = '/' . CSSMin::PLACEHOLDER . '(\d+)x/';
 359                 $source = preg_replace_callback( $pattern, function( $match ) use ( &$comments ) {
 360                         return $comments[ $match[1] ];
 361                 }, $source );
 362
 363                 return $source;
 364         }
 365
 366         /**
 367          * Is this CSS rule referencing a remote URL?
 368          *
 369          * @param string $maybeUrl
 370          * @return bool
 371          */
 372         protected static function isRemoteUrl( $maybeUrl ) {
 373                 if ( substr( $maybeUrl, 0, 2 ) === '//' || parse_url( $maybeUrl, PHP_URL_SCHEME ) ) {
 374                         return true;
 375                 }
 376                 return false;
 377         }
 378
 379         /**
 380          * Is this CSS rule referencing a local URL?
 381          *
 382          * @param string $maybeUrl
 383          * @return bool
 384          */
 385         protected static function isLocalUrl( $maybeUrl ) {
 386                 if ( $maybeUrl !== '' && $maybeUrl[0] === '/' && !self::isRemoteUrl( $maybeUrl ) ) {
 387                         return true;
 388                 }
 389                 return false;
 390         }
 391
 392         private static function getUrlRegex() {
 393                 static $urlRegex;
 394                 if ( $urlRegex === null ) {
 395                         // Match these three variants separately to avoid broken urls when
 396                         // e.g. a double quoted url contains a parenthesis, or when a
 397                         // single quoted url contains a double quote, etc.
 398                         // Note: PCRE doesn't support multiple capture groups with the same name by default.
 399                         // - PCRE 6.7 introduced the "J" modifier (PCRE_INFO_JCHANGED for PCRE_DUPNAMES).
 400                         //   https://secure.php.net/manual/en/reference.pcre.pattern.modifiers.php
 401                         //   However this isn't useful since it just ignores all but the first one.
 402                         //   Also, while the modifier was introduced in PCRE 6.7 (PHP 5.2+) it was
 403                         //   not exposed to public preg_* functions until PHP 5.6.0.
 404                         // - PCRE 8.36 fixed this to work as expected (e.g. merge conceptually to
 405                         //   only return the one matched in the part that actually matched).
 406                         //   However MediaWiki supports 5.5.9, which has PCRE 8.32
 407                         //   Per https://secure.php.net/manual/en/pcre.installation.php:
 408                         //   - PCRE 8.32 (PHP 5.5.0)
 409                         //   - PCRE 8.34 (PHP 5.5.10, PHP 5.6.0)
 410                         //   - PCRE 8.37 (PHP 5.5.26, PHP 5.6.9, PHP 7.0.0)
 411                         //   Workaround by using different groups and merge via processUrlMatch().
 412                         // - Using string concatenation for class constant or member assignments
 413                         //   is only supported in PHP 5.6. Use a getter method for now.
 414                         $urlRegex = '(' .
 415                                 // Unquoted url
 416                                 'url\(\s*(?P<file0>[^\'"][^\?\)]*?)(?P<query0>\?[^\)]*?|)\s*\)' .
 417                                 // Single quoted url
 418                                 '|url\(\s*\'(?P<file1>[^\?\']*?)(?P<query1>\?[^\']*?|)\'\s*\)' .
 419                                 // Double quoted url
 420                                 '|url\(\s*"(?P<file2>[^\?"]*?)(?P<query2>\?[^"]*?|)"\s*\)' .
 421                                 ')';
 422                 }
 423                 return $urlRegex;
 424         }
 425
 426         private static function processUrlMatch( array &$match, $flags = 0 ) {
 427                 if ( $flags & PREG_SET_ORDER ) {
 428                         // preg_match_all with PREG_SET_ORDER will return each group in each
 429                         // match array, and if it didn't match, instead of the sub array
 430                         // being an empty array it is `[ '', -1 ]`...
 431                         if ( isset( $match['file0'] ) && $match['file0'][1] !== -1 ) {
 432                                 $match['file'] = $match['file0'];
 433                                 $match['query'] = $match['query0'];
 434                         } elseif ( isset( $match['file1'] ) && $match['file1'][1] !== -1 ) {
 435                                 $match['file'] = $match['file1'];
 436                                 $match['query'] = $match['query1'];
 437                         } else {
 438                                 $match['file'] = $match['file2'];
 439                                 $match['query'] = $match['query2'];
 440                         }
 441                 } else {
 442                         if ( isset( $match['file0'] ) && $match['file0'] !== '' ) {
 443                                 $match['file'] = $match['file0'];
 444                                 $match['query'] = $match['query0'];
 445                         } elseif ( isset( $match['file1'] ) && $match['file1'] !== '' ) {
 446                                 $match['file'] = $match['file1'];
 447                                 $match['query'] = $match['query1'];
 448                         } else {
 449                                 $match['file'] = $match['file2'];
 450                                 $match['query'] = $match['query2'];
 451                         }
 452                 }
 453         }
 454
 455         /**
 456          * Remap or embed a CSS URL path.
 457          *
 458          * @param string $file URL to remap/embed
 459          * @param string $query
 460          * @param string $local File path where the source was read from
 461          * @param string $remote URL path to the file
 462          * @param bool $embed Whether to do any data URI embedding
 463          * @return string Remapped/embedded URL data
 464          */
 465         public static function remapOne( $file, $query, $local, $remote, $embed ) {
 466                 // The full URL possibly with query, as passed to the 'url()' value in CSS
 467                 $url = $file . $query;
 468
 469                 // Expand local URLs with absolute paths like /w/index.php to possibly protocol-relative URL, if
 470                 // wfExpandUrl() is available. (This will not be the case if we're running outside of MW.)
 471                 if ( self::isLocalUrl( $url ) && function_exists( 'wfExpandUrl' ) ) {
 472                         return wfExpandUrl( $url, PROTO_RELATIVE );
 473                 }
 474
 475                 // Pass thru fully-qualified and protocol-relative URLs and data URIs, as well as local URLs if
 476                 // we can't expand them.
 477                 if ( self::isRemoteUrl( $url ) || self::isLocalUrl( $url ) ) {
 478                         return $url;
 479                 }
 480
 481                 if ( $local === false ) {
 482                         // Assume that all paths are relative to $remote, and make them absolute
 483                         $url = $remote . '/' . $url;
 484                 } else {
 485                         // We drop the query part here and instead make the path relative to $remote
 486                         $url = "{$remote}/{$file}";
 487                         // Path to the actual file on the filesystem
 488                         $localFile = "{$local}/{$file}";
 489                         if ( file_exists( $localFile ) ) {
 490                                 if ( $embed ) {
 491                                         $data = self::encodeImageAsDataURI( $localFile );
 492                                         if ( $data !== false ) {
 493                                                 return $data;
 494                                         }
 495                                 }
 496                                 if ( method_exists( 'OutputPage', 'transformFilePath' ) ) {
 497                                         $url = OutputPage::transformFilePath( $remote, $local, $file );
 498                                 } else {
 499                                         // Add version parameter as the first five hex digits
 500                                         // of the MD5 hash of the file's contents.
 501                                         $url .= '?' . substr( md5_file( $localFile ), 0, 5 );
 502                                 }
 503                         }
 504                         // If any of these conditions failed (file missing, we don't want to embed it
 505                         // or it's not embeddable), return the URL (possibly with ?timestamp part)
 506                 }
 507                 if ( function_exists( 'wfRemoveDotSegments' ) ) {
 508                         $url = wfRemoveDotSegments( $url );
 509                 }
 510                 return $url;
 511         }
 512
 513         /**
 514          * Removes whitespace from CSS data
 515          *
 516          * @param string $css CSS data to minify
 517          * @return string Minified CSS data
 518          */
 519         public static function minify( $css ) {
 520                 return trim(
 521                         str_replace(
 522                                 [ '; ', ': ', ' {', '{ ', ', ', '} ', ';}' ],
 523                                 [ ';', ':', '{', '{', ',', '}', '}' ],
 524                                 preg_replace( [ '/\s+/', '/\/\*.*?\*\//s' ], [ ' ', '' ], $css )
 525                         )
 526                 );
 527         }
 528 }