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   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 <[email protected]>
  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      /**
  35       * Maximum file size to still qualify for in-line embedding as a data-URI
  36       *
  37       * 24,576 is used because Internet Explorer has a 32,768 byte limit for data URIs,
  38       * which when base64 encoded will result in a 1/3 increase in size.
  39       */
  40      const EMBED_SIZE_LIMIT = 24576;
  41      const URL_REGEX = 'url\(\s*[\'"]?(?P<file>[^\?\)\'"]*?)(?P<query>\?[^\)\'"]*?|)[\'"]?\s*\)';
  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 = array(
  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       * Gets a list of local file paths which are referenced in a CSS style sheet
  64       *
  65       * This function will always return an empty array if the second parameter is not given or null
  66       * for backwards-compatibility.
  67       *
  68       * @param string $source CSS data to remap
  69       * @param string $path File path where the source was read from (optional)
  70       * @return array List of local file references
  71       */
  72  	public static function getLocalFileReferences( $source, $path = null ) {
  73          if ( $path === null ) {
  74              return array();
  75          }
  76  
  77          $path = rtrim( $path, '/' ) . '/';
  78          $files = array();
  79  
  80          $rFlags = PREG_OFFSET_CAPTURE | PREG_SET_ORDER;
  81          if ( preg_match_all( '/' . self::URL_REGEX . '/', $source, $matches, $rFlags ) ) {
  82              foreach ( $matches as $match ) {
  83                  $url = $match['file'][0];
  84  
  85                  // Skip fully-qualified and protocol-relative URLs and data URIs
  86                  if ( substr( $url, 0, 2 ) === '//' || parse_url( $url, PHP_URL_SCHEME ) ) {
  87                      break;
  88                  }
  89  
  90                  $file = $path . $url;
  91                  // Skip non-existent files
  92                  if ( file_exists( $file ) ) {
  93                      break;
  94                  }
  95  
  96                  $files[] = $file;
  97              }
  98          }
  99          return $files;
 100      }
 101  
 102      /**
 103       * Encode an image file as a base64 data URI.
 104       * If the image file has a suitable MIME type and size, encode it as a
 105       * base64 data URI. Return false if the image type is unfamiliar or exceeds
 106       * the size limit.
 107       *
 108       * @param string $file Image file to encode.
 109       * @param string|null $type File's MIME type or null. If null, CSSMin will
 110       *     try to autodetect the type.
 111       * @param int|bool $sizeLimit If the size of the target file is greater than
 112       *     this value, decline to encode the image file and return false
 113       *     instead. If $sizeLimit is false, no limit is enforced.
 114       * @return string|bool: Image contents encoded as a data URI or false.
 115       */
 116  	public static function encodeImageAsDataURI( $file, $type = null,
 117          $sizeLimit = self::EMBED_SIZE_LIMIT
 118      ) {
 119          if ( $sizeLimit !== false && filesize( $file ) >= $sizeLimit ) {
 120              return false;
 121          }
 122          if ( $type === null ) {
 123              $type = self::getMimeType( $file );
 124          }
 125          if ( !$type ) {
 126              return false;
 127          }
 128          $data = base64_encode( file_get_contents( $file ) );
 129          return 'data:' . $type . ';base64,' . $data;
 130      }
 131  
 132      /**
 133       * @param $file string
 134       * @return bool|string
 135       */
 136  	public static function getMimeType( $file ) {
 137          $realpath = realpath( $file );
 138          if (
 139              $realpath
 140              && function_exists( 'finfo_file' )
 141              && function_exists( 'finfo_open' )
 142              && defined( 'FILEINFO_MIME_TYPE' )
 143          ) {
 144              return finfo_file( finfo_open( FILEINFO_MIME_TYPE ), $realpath );
 145          }
 146  
 147          // Infer the MIME-type from the file extension
 148          $ext = strtolower( pathinfo( $file, PATHINFO_EXTENSION ) );
 149          if ( isset( self::$mimeTypes[$ext] ) ) {
 150              return self::$mimeTypes[$ext];
 151          }
 152  
 153          return false;
 154      }
 155  
 156      /**
 157       * Build a CSS 'url()' value for the given URL, quoting parentheses (and other funny characters)
 158       * and escaping quotes as necessary.
 159       *
 160       * See http://www.w3.org/TR/css-syntax-3/#consume-a-url-token
 161       *
 162       * @param string $url URL to process
 163       * @return string 'url()' value, usually just `"url($url)"`, quoted/escaped if necessary
 164       */
 165  	public static function buildUrlValue( $url ) {
 166          // The list below has been crafted to match URLs such as:
 167          //   scheme://user@domain:port/~user/fi%20le.png?query=yes&really=y+s
 168          //   data:image/png;base64,R0lGODlh/+==
 169          if ( preg_match( '!^[\w\d:@/~.%+;,?&=-]+$!', $url ) ) {
 170              return "url($url)";
 171          } else {
 172              return 'url("' . strtr( $url, array( '\\' => '\\\\', '"' => '\\"' ) ) . '")';
 173          }
 174      }
 175  
 176      /**
 177       * Remaps CSS URL paths and automatically embeds data URIs for CSS rules
 178       * or url() values preceded by an / * @embed * / comment.
 179       *
 180       * @param string $source CSS data to remap
 181       * @param string $local File path where the source was read from
 182       * @param string $remote URL path to the file
 183       * @param bool $embedData If false, never do any data URI embedding,
 184       *   even if / * @embed * / is found.
 185       * @return string Remapped CSS data
 186       */
 187  	public static function remap( $source, $local, $remote, $embedData = true ) {
 188          // High-level overview:
 189          // * For each CSS rule in $source that includes at least one url() value:
 190          //   * Check for an @embed comment at the start indicating that all URIs should be embedded
 191          //   * For each url() value:
 192          //     * Check for an @embed comment directly preceding the value
 193          //     * If either @embed comment exists:
 194          //       * Embedding the URL as data: URI, if it's possible / allowed
 195          //       * Otherwise remap the URL to work in generated stylesheets
 196  
 197          // Guard against trailing slashes, because "some/remote/../foo.png"
 198          // resolves to "some/remote/foo.png" on (some?) clients (bug 27052).
 199          if ( substr( $remote, -1 ) == '/' ) {
 200              $remote = substr( $remote, 0, -1 );
 201          }
 202  
 203          // Replace all comments by a placeholder so they will not interfere with the remapping.
 204          // Warning: This will also catch on anything looking like the start of a comment between
 205          // quotation marks (e.g. "foo /* bar").
 206          $comments = array();
 207          $placeholder = uniqid( '', true );
 208  
 209          $pattern = '/(?!' . CSSMin::EMBED_REGEX . ')(' . CSSMin::COMMENT_REGEX . ')/s';
 210  
 211          $source = preg_replace_callback(
 212              $pattern,
 213              function ( $match ) use ( &$comments, $placeholder ) {
 214                  $comments[] = $match[ 0 ];
 215                  return $placeholder . ( count( $comments ) - 1 ) . 'x';
 216              },
 217              $source
 218          );
 219  
 220          // Note: This will not correctly handle cases where ';', '{' or '}'
 221          // appears in the rule itself, e.g. in a quoted string. You are advised
 222          // not to use such characters in file names. We also match start/end of
 223          // the string to be consistent in edge-cases ('@import url(…)').
 224          $pattern = '/(?:^|[;{])\K[^;{}]*' . CSSMin::URL_REGEX . '[^;}]*(?=[;}]|$)/';
 225  
 226          $source = preg_replace_callback(
 227              $pattern,
 228              function ( $matchOuter ) use ( $local, $remote, $embedData, $placeholder ) {
 229                  $rule = $matchOuter[0];
 230  
 231                  // Check for global @embed comment and remove it. Allow other comments to be present
 232                  // before @embed (they have been replaced with placeholders at this point).
 233                  $embedAll = false;
 234                  $rule = preg_replace( '/^((?:\s+|' . $placeholder . '(\d+)x)*)' . CSSMin::EMBED_REGEX . '\s*/', '$1', $rule, 1, $embedAll );
 235  
 236                  // Build two versions of current rule: with remapped URLs
 237                  // and with embedded data: URIs (where possible).
 238                  $pattern = '/(?P<embed>' . CSSMin::EMBED_REGEX . '\s*|)' . CSSMin::URL_REGEX . '/';
 239  
 240                  $ruleWithRemapped = preg_replace_callback(
 241                      $pattern,
 242                      function ( $match ) use ( $local, $remote ) {
 243                          $remapped = CSSMin::remapOne( $match['file'], $match['query'], $local, $remote, false );
 244  
 245                          return CSSMin::buildUrlValue( $remapped );
 246                      },
 247                      $rule
 248                  );
 249  
 250                  if ( $embedData ) {
 251                      $ruleWithEmbedded = preg_replace_callback(
 252                          $pattern,
 253                          function ( $match ) use ( $embedAll, $local, $remote ) {
 254                              $embed = $embedAll || $match['embed'];
 255                              $embedded = CSSMin::remapOne(
 256                                  $match['file'],
 257                                  $match['query'],
 258                                  $local,
 259                                  $remote,
 260                                  $embed
 261                              );
 262  
 263                              return CSSMin::buildUrlValue( $embedded );
 264                          },
 265                          $rule
 266                      );
 267                  }
 268  
 269                  if ( $embedData && $ruleWithEmbedded !== $ruleWithRemapped ) {
 270                      // Build 2 CSS properties; one which uses a base64 encoded data URI in place
 271                      // of the @embed comment to try and retain line-number integrity, and the
 272                      // other with a remapped an versioned URL and an Internet Explorer hack
 273                      // making it ignored in all browsers that support data URIs
 274                      return "$ruleWithEmbedded;$ruleWithRemapped!ie";
 275                  } else {
 276                      // No reason to repeat twice
 277                      return $ruleWithRemapped;
 278                  }
 279              }, $source );
 280  
 281          // Re-insert comments
 282          $pattern = '/' . $placeholder . '(\d+)x/';
 283          $source = preg_replace_callback( $pattern, function( $match ) use ( &$comments ) {
 284              return $comments[ $match[1] ];
 285          }, $source );
 286  
 287          return $source;
 288  
 289      }
 290  
 291      /**
 292       * Remap or embed a CSS URL path.
 293       *
 294       * @param string $file URL to remap/embed
 295       * @param string $query
 296       * @param string $local File path where the source was read from
 297       * @param string $remote URL path to the file
 298       * @param bool $embed Whether to do any data URI embedding
 299       * @return string Remapped/embedded URL data
 300       */
 301  	public static function remapOne( $file, $query, $local, $remote, $embed ) {
 302          // The full URL possibly with query, as passed to the 'url()' value in CSS
 303          $url = $file . $query;
 304  
 305          // Skip fully-qualified and protocol-relative URLs and data URIs
 306          if ( substr( $url, 0, 2 ) === '//' || parse_url( $url, PHP_URL_SCHEME ) ) {
 307              return $url;
 308          }
 309  
 310          // URLs with absolute paths like /w/index.php need to be expanded
 311          // to absolute URLs but otherwise left alone
 312          if ( $url !== '' && $url[0] === '/' ) {
 313              // Replace the file path with an expanded (possibly protocol-relative) URL
 314              // ...but only if wfExpandUrl() is even available.
 315              // This will not be the case if we're running outside of MW
 316              if ( function_exists( 'wfExpandUrl' ) ) {
 317                  return wfExpandUrl( $url, PROTO_RELATIVE );
 318              } else {
 319                  return $url;
 320              }
 321          }
 322  
 323          if ( $local === false ) {
 324              // Assume that all paths are relative to $remote, and make them absolute
 325              return $remote . '/' . $url;
 326          } else {
 327              // We drop the query part here and instead make the path relative to $remote
 328              $url = "{$remote}/{$file}";
 329              // Path to the actual file on the filesystem
 330              $localFile = "{$local}/{$file}";
 331              if ( file_exists( $localFile ) ) {
 332                  // Add version parameter as a time-stamp in ISO 8601 format,
 333                  // using Z for the timezone, meaning GMT
 334                  $url .= '?' . gmdate( 'Y-m-d\TH:i:s\Z', round( filemtime( $localFile ), -2 ) );
 335                  if ( $embed ) {
 336                      $data = self::encodeImageAsDataURI( $localFile );
 337                      if ( $data !== false ) {
 338                          return $data;
 339                      }
 340                  }
 341              }
 342              // If any of these conditions failed (file missing, we don't want to embed it
 343              // or it's not embeddable), return the URL (possibly with ?timestamp part)
 344              return $url;
 345          }
 346      }
 347  
 348      /**
 349       * Removes whitespace from CSS data
 350       *
 351       * @param string $css CSS data to minify
 352       * @return string Minified CSS data
 353       */
 354  	public static function minify( $css ) {
 355          return trim(
 356              str_replace(
 357                  array( '; ', ': ', ' {', '{ ', ', ', '} ', ';}' ),
 358                  array( ';', ':', '{', '{', ',', '}', '}' ),
 359                  preg_replace( array( '/\s+/', '/\/\*.*?\*\//s' ), array( ' ', '' ), $css )
 360              )
 361          );
 362      }
 363  }