CssOptimizer::loadFile

public CssOptimizer::loadFile($file, $optimize = NULL, $reset_basepath = TRUE)

public function loadFile($file, $optimize = NULL, $reset_basepath = TRUE) {
  // These statics are not cache variables, so we don't use drupal_static().
  static $_optimize, $basepath;
  if ($reset_basepath) {
    $basepath = '';
  }
  // Store the value of $optimize for preg_replace_callback with nested
  // @import loops.
  if (isset($optimize)) {
    $_optimize = $optimize;
  }

  // Stylesheets are relative one to each other. Start by adding a base path
  // prefix provided by the parent stylesheet (if necessary).
  if ($basepath && !file_uri_scheme($file)) {
    $file = $basepath . '/' . $file;
  }
  // Store the parent base path to restore it later.
  $parent_base_path = $basepath;
  // Set the current base path to process possible child imports.
  $basepath = dirname($file);

  // Load the CSS stylesheet. We suppress errors because themes may specify
  // stylesheets in their .info.yml file that don't exist in the theme's path,
  // but are merely there to disable certain module CSS files.
  $content = '';
  if ($contents = @file_get_contents($file)) {
    // If a BOM is found, convert the file to UTF-8, then use substr() to
    // remove the BOM from the result.
    if ($encoding = (Unicode::encodingFromBOM($contents))) {
      $contents = Unicode::substr(Unicode::convertToUtf8($contents, $encoding), 1);
    }
    // If no BOM, check for fallback encoding. Per CSS spec the regex is very strict.
    elseif (preg_match('/^@charset "([^"]+)";/', $contents, $matches)) {
      if ($matches[1] !== 'utf-8' && $matches[1] !== 'UTF-8') {
        $contents = substr($contents, strlen($matches[0]));
        $contents = Unicode::convertToUtf8($contents, $matches[1]);
      }
    }

    // Return the processed stylesheet.
    $content = $this->processCss($contents, $_optimize);
  }

  // Restore the parent base path as the file and its children are processed.
  $basepath = $parent_base_path;
  return $content;
}