ExtensionMimeTypeGuesser::guess

public ExtensionMimeTypeGuesser::guess($path)

public function guess($path) {
  if ($this->mapping === NULL) {
    $mapping = $this->defaultMapping;
    // Allow modules to alter the default mapping.
    $this->moduleHandler->alter('file_mimetype_mapping', $mapping);
    $this->mapping = $mapping;
  }

  $extension = '';
  $file_parts = explode('.', drupal_basename($path));

  // Remove the first part: a full filename should not match an extension.
  array_shift($file_parts);

  // Iterate over the file parts, trying to find a match.
  // For my.awesome.image.jpeg, we try:
  //   - jpeg
  //   - image.jpeg, and
  //   - awesome.image.jpeg
  while ($additional_part = array_pop($file_parts)) {
    $extension = strtolower($additional_part . ($extension ? '.' . $extension : ''));
    if (isset($this->mapping['extensions'][$extension])) {
      return $this->mapping['mimetypes'][$this->mapping['extensions'][$extension]];
    }
  }

  return 'application/octet-stream';
}